JP4472208B2 - Communication system, communication method, and MPLS / ATM conversion program - Google Patents

Description

【表２】

なお、本実施形態では、ＭＰＬＳのトラヒックパラメータのうちＥＢＳ（Excess Burst Size）、Frequency、WeightはＡＴＭ網では使用しないものとする。また、ＡＴＭメッセージからＭＰＬＳメッセージへの変換時には、ＤＳのFrequencyのみFrequentとし、他は不使用（EBS=0、Frequency=Unspecified、Weight=0）とする。
【００３６】
次に、ＭＰＬＳ／ＡＴＭ変換機能部１が有するＭＰＬＳ回線とＡＴＭ回線との対応関係を管理する機能について説明する。ＭＰＬＳ／ＡＴＭ変換機能部１では、ＭＰＬＳ回線とＡＴＭ回線の対応関係の管理することで、ＭＰＬＳまたはＡＴＭメッセージを受信した時に、どのＭＰＬＳ回線及びＡＴＭ回線に関するメッセージなのかを識別する。例えば、本実施形態のＭＰＬＳ／ＡＴＭ変換機能部１は、管理テーブル１８を備え、管理テーブル１８に必要なデータを記録して、ＭＰＬＳ回線とＡＴＭ回線との対応関係を管理する（図１６参照）。管理テーブル１８は、例えば加入者系ＡＴＭ交換機３が備える記憶装置に記録される。なお、管理テーブル１８の行に該当するデータのまとまりを本実施形態では管理レコード１９と呼ぶ。
【００３７】
以上のような機能を備える加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）が、ＬＥＲ２から各種のＭＰＬＳメッセージを受信した場合、またバックボーンＡＴＭ交換機４から各種のＡＴＭメッセージを受信した場合の処理の一例を、メッセージの種別毎に図７から図１５のフローチャートに示し、以下これに従って説明する。
【００３８】
加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２ａからラベル要求のＭＰＬＳメッセージ（Label Request）を受信すると、例えば図７のフローチャートに示す処理を実行する。先ず、ＭＰＬＳメッセージ（Label Request）が有効であるか否か調べる（ステップ１０１）。なお、メッセージが有効であるか否かとは、当該メッセージが所定のフォーマットに違反するか否か、例えば必須パラメータが含まれているか等のエラーの有無をチェックするものである。有効であれば（ステップ１０１；Ｙｅｓ）、ＭＰＬＳ／ＡＴＭ変換機能部１にて宛先ＩＰアドレスをＡＴＭアドレスに変換する（ステップ１０２）。そして、必要なパラメータ変換を行う（ステップ１０３）。そして、転送先のバックボーンＡＴＭ交換機４が存在するか否か確認する（ステップ１０４）。転送先のバックボーンＡＴＭ交換機４が存在すれば（ステップ１０４；Ｙｅｓ）、次いでリソースの確保が可能であるか否か、即ち要求された伝送品質が提供可能であるか否か確認する（ステップ１０５）。リソース確保可能であれば（ステップ１０５；Ｙｅｓ）、ラベル要求のＭＰＬＳメッセージ（Label Request）を回線設定要求のＡＴＭメッセージ（SETUP）に変換し、当該ＡＴＭメッセージ（SETUP）を上記変換した所定パラメータとともに、バックボーンＡＴＭ交換機４に向けて送信する（ステップ１０６）。そして、ＬＥＲ２から受信したＭＰＬＳメッセージ（Label Request）中のＬＳＰＩＤ（Label Switched Path Identifier）と宛先ＩＰアドレスとを管理テーブル１８に記録する。さらに、これに対応させて、バックボーンＡＴＭ交換機４へ送信したＡＴＭメッセージ（SETUP）のＣＲ（Call Reference）を管理テーブル１８に記録する（ステップ１０７）。一方、ＭＰＬＳメッセージ（Label Request）が有効でない場合（ステップ１０１；Ｎｏ）、または転送先のバックボーンＡＴＭ交換機４が存在しない場合（ステップ１０４；Ｎｏ）、またはリソース確保できない場合（ステップ１０５；Ｎｏ）は、ＬＥＲ２にエラーを通知すべくＭＰＬＳメッセージ（Notification）を送信する（ステップ１０８）。
【００３９】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４から回線設定要求のＡＴＭメッセージ（SETUP）を受信すると、例えば図８のフローチャートに示す処理を実行する。先ず、ＡＴＭメッセージ（SETUP）が有効であるか否か調べ（ステップ２０１）、有効であれば（ステップ２０１；Ｙｅｓ）、宛先ＡＴＭアドレスのＥＳＩ部１５がＭＰＬＳ用特番であるか否か調べる（ステップ２０２）。宛先ＡＴＭアドレスのＥＳＩ部１５がＭＰＬＳ用特番であれば、ＩＰアドレスに復元する必要があることを認識し（ステップ２０２；Ｙｅｓ）、ＡＴＭアドレスからＩＰアドレスへの変換を行う（ステップ２０３）。そして、必要なパラメータ変換を行う（ステップ２０４）。そして、転送先のＬＥＲ２が存在するか否か確認する（ステップ２０５）。転送先のＬＥＲ２が存在すれば（ステップ２０５；Ｙｅｓ）、次いでリソースの確保が可能であるか否か、即ち要求された伝送品質が提供可能であるか否か確認する（ステップ２０６）。リソース確保可能であれば（ステップ２０６；Ｙｅｓ）、回線設定要求のＡＴＭメッセージ（SETUP）をラベル要求のＭＰＬＳメッセージ（Label Request）に変換し、当該ＭＰＬＳメッセージを上記変換した所定パラメータとともに、ＬＥＲ２に向けて送信する（ステップ２０７）。そして、バックボーンＡＴＭ交換機４から受信したＡＴＭメッセージ（SETUP）のＣＲと、ＬＥＲ２に送信したＭＰＬＳメッセージ（Label Request）中のＬＳＰＩＤと宛先ＩＰアドレスとを管理テーブル１８に対応させて記録する。一方、宛先ＡＴＭアドレスのＥＳＩ部１５がＭＰＬＳ用特番でない場合は（ステップ２０２；Ｎｏ）、当該ＡＴＭアドレスを有するＡＴＭ端末に対して通常のＡＴＭ処理が行われる（ステップ２０９）。また、ＡＴＭメッセージ（SETUP）が有効でない場合（ステップ２０１；Ｎｏ）、または転送先のＬＥＲ２が存在しない場合（ステップ２０５；Ｎｏ）、またはリソース確保できない場合（ステップ２０６；Ｎｏ）は、バックボーンＡＴＭ交換機４に回線解放のＡＴＭメッセージ（RELEASE）を送信する（ステップ２１０）。
【００４０】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２からラベル通知のＭＰＬＳメッセージ（Label Mapping）を受信すると、例えば図９のフローチャートに示す処理を実行する。即ち、ＭＰＬＳメッセージ（Label Mapping）が有効であるか否か調べ（ステップ３０１）、有効であれば（ステップ３０１；Ｙｅｓ）、対応する設定待ちのＡＴＭ回線が存在するか調べる（ステップ３０２）。即ち、ＬＥＲ２から受信したＭＰＬＳメッセージ（Label Mapping）中のＬＳＰＩＤや宛先ＩＰアドレスをキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＭＰＬＳ回線及びＡＴＭ回線の組み合わせを把握する。そして、対応するＡＴＭ回線が存在すれば（ステップ３０２；Ｙｅｓ）、ＶＰＩ／ＶＣＩ（Virtual Path Identifier／Virtual Channel Identifier）を決定し（ステップ３０３）、ラベル通知のＭＰＬＳメッセージ（Label Mapping）を回線設定完了のＡＴＭメッセージ（CONNECT）に変換してバックボーンＡＴＭ交換機４に向けて送信する（ステップ３０４）。そして、ＬＥＲ２から受信したＭＰＬＳメッセージ（Label Mapping）中のＭＰＬＳ用のラベルと、バックボーンＡＴＭ交換機４に送信したＡＴＭメッセージ（CONNECT）のＶＰＩ／ＶＣＩとを、管理テーブル１８上の該当する管理レコード１９に追加して記録する。従って、ＬＳＰＩＤと宛先ＩＰアドレスとラベルとＣＲとＶＰＩ／ＶＣＩとが管理レコード１９として関連付けられて管理テーブル１８上で管理される（ステップ３０５）。一方、ＭＰＬＳメッセージ（Label Mapping）が有効でない場合（ステップ３０１；Ｎｏ）、または対応する設定待ちのＡＴＭ回線が存在しない場合（ステップ３０２；Ｎｏ）は、ＬＥＲ２にエラーを通知すべくＭＰＬＳメッセージ（Notification）を送信する（ステップ３０６）。
【００４１】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４から回線設定完了のＡＴＭメッセージ（CONNECT）を受信すると、例えば図１０のフローチャートに示す処理を実行する。即ち、ＡＴＭメッセージ（CONNECT）が有効であるか否か調べ（ステップ４０１）、有効であれば（ステップ４０１；Ｙｅｓ）、対応する設定待ちのＭＰＬＳ回線が存在するか調べる（ステップ４０２）。ＭＰＬＳ／ＡＴＭ変換機能部１では、例えばバックボーンＡＴＭ交換機４から受信したＡＴＭメッセージ（CONNECT）のＣＲをキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＭＰＬＳ回線及びＡＴＭ回線の組み合わせを把握する。そして、対応する設定待ちのＭＰＬＳ回線が存在すれば（ステップ４０２；Ｙｅｓ）、ＭＰＬＳ用のラベルを決定し（ステップ４０３）、回線設定完了のＡＴＭメッセージ（CONNECT）をラベル通知のＭＰＬＳメッセージ（Label Mapping）に変換してＬＥＲ２に向けて送信する（ステップ４０４）。なお、本実施形態では、ＭＰＬＳ用のラベルとして、ＡＴＭセルのＶＰＩ／ＶＣＩを用いるものとしている。そして、バックボーンＡＴＭ交換機４から受信したＡＴＭメッセージ（CONNECT）のＶＰＩ／ＶＣＩと、ＬＥＲ２に送信したＭＰＬＳメッセージ（Label Mapping）中に含まれ当該送信に際して決定されたＭＰＬＳ用のラベルとを、管理テーブル１８上の該当する管理レコード１９に追加して記録する。従って、ＬＳＰＩＤと宛先ＩＰアドレスとラベルとＣＲとＶＰＩ／ＶＣＩとが対応付けられて管理テーブル１８上で管理される（ステップ４０５）。一方、ＡＴＭメッセージ（CONNECT）が有効でない場合（ステップ４０１；Ｎｏ）、または対応する設定待ちのＭＰＬＳ回線が存在しない場合（ステップ４０２；Ｎｏ）は、バックボーンＡＴＭ交換機４からの当該ＡＴＭメッセージ（CONNECT）は無視される（ステップ４０６）。
【００４２】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４から回線解放のＡＴＭメッセージ（RELEASE）を受信すると、例えば図１１のフローチャートに示す処理を実行する。即ち、ＡＴＭメッセージ（RELEASE）が有効であるか否か調べ（ステップ５０１）、有効であれば（ステップ５０１；Ｙｅｓ）、対応するＭＰＬＳ回線が存在するか調べる（ステップ５０２）。ＭＰＬＳ／ＡＴＭ変換機能部１では、例えばバックボーンＡＴＭ交換機４から受信したＡＴＭメッセージ（RELEASE）のＣＲをキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＭＰＬＳ回線を把握する。そして、対応するＭＰＬＳ回線が存在すれば（ステップ５０２；Ｙｅｓ）、次いでバックボーンＡＴＭ交換機４から受信した当該ＡＴＭメッセージ（RELEASE）が、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）が先に送信した回線設定要求のＡＴＭメッセージ（SETUP）に対する応答か否か確認する（ステップ５０３）。当該応答であれば（ステップ５０３；Ｙｅｓ）、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）が要求した回線設定は、例えば帯域不足等で完了されなかったものと判断し、ＬＥＲ２に向けて通知のＭＰＬＳメッセージ（Notification）を送信する（ステップ５０４）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレスとＡＴＭのＣＲとの対応関係管理を終了する（ステップ５０５）。
【００４３】
一方、当該ＡＴＭメッセージ（RELEASE）が加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）が先に送信した回線設定要求のＡＴＭメッセージ（SETUP）に対する応答ではない場合は（ステップ５０３；Ｎｏ）、次に当該ＡＴＭメッセージ（RELEASE）が加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）が以前に受信した回線設定要求のＡＴＭメッセージ（SETUP）に対応するものか否か確認する（ステップ５０７）。当該ＡＴＭメッセージ（SETUP）に対応するものであれば（ステップ５０７；Ｙｅｓ）、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）に以前に要求された回線設定は、要求側の何らかの事情で取り消すように要請されたものと判断し、当該ＡＴＭメッセージ（SETUP）に関して、ラベル要求のＭＰＬＳメッセージ（Label Request）をＬＥＲ２に送信済みであるか否か確認する（ステップ５０８）。ＭＰＬＳメッセージ（Label Request）をＬＥＲ２に既に送信してれば（ステップ５０８；Ｙｅｓ）、当該ＬＥＲ２に向けてラベル解放のＭＰＬＳメッセージ（Label Release）を送信する（ステップ５０９）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ５０５）。他方、ＬＥＲ２にＭＰＬＳメッセージ（Label Request）を未だ送信していない場合は（ステップ５０８；Ｎｏ）、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ５０５）。
【００４４】
また、バックボーンＡＴＭ交換機４から受信したＡＴＭメッセージ（RELEASE）が、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）が先に送信したＡＴＭメッセージ（SETUP）に対する応答ではなく（ステップ５０３；Ｎｏ）、しかも以前に受信したＡＴＭメッセージ（SETUP）に対応するものでもない場合には（ステップ５０７；Ｎｏ）、設定済みの回線の解放を要求されたケースとなる。この場合、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）では、対向するＬＥＲ２がラベル要求側か否か確認し（ステップ５１０）、ラベル要求側であれば（ステップ５１０；Ｙｅｓ）、ラベル取消のＭＰＬＳメッセージ（Label Withdraw）を送信する（ステップ５１１）。ラベル要求側でなければ即ちラベルを要求された側であれば（ステップ５１０；Ｎｏ）、ラベル解放のＭＰＬＳメッセージ（Label Release）を送信する（ステップ５０９）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ５０５）。この他、ＡＴＭメッセージ（RELEASE）が有効でない場合（ステップ５０１；Ｎｏ）、または対応する設定待ちのＭＰＬＳ回線が存在しない場合（ステップ５０２；Ｎｏ）は、当該ＡＴＭメッセージ（RELEASE）は無視される（ステップ５０６）。
【００４５】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２からラベル解放のＭＰＬＳメッセージ（Label Release）を受信すると、例えば図１２のフローチャートに示す処理を実行する。即ち、当該ＭＰＬＳメッセージ（Label Release）が有効であるか否か調べる（ステップ６０１）。有効であれば（ステップ６０１；Ｙｅｓ）、次いで当該ＭＰＬＳメッセージが、既に加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）がＬＥＲ２に送信してあるラベル取消のＭＰＬＳメッセージ（Label Withdraw）への応答であるか否か判断する（ステップ６０２）。当該応答でなければ（ステップ６０２；Ｎｏ）、対応するＡＴＭ回線が存在するか否か調べる（ステップ６０３）。即ち、ＭＰＬＳ／ＡＴＭ変換機能部１では、ＬＥＲ２から受信したＭＰＬＳメッセージ（Label Release）中のＬＳＰＩＤや宛先ＩＰアドレスをキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＡＴＭ回線を把握する。そして、対応するＡＴＭ回線が存在すれば（ステップ６０３；Ｙｅｓ）、ラベル解放のＭＰＬＳメッセージ（Label Release）を回線解放のＡＴＭメッセージ（RELEASE）に変換してバックボーンＡＴＭ交換機４に向けて送信する（ステップ６０４）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ６０５）。一方、当該ラベル解放のＭＰＬＳメッセージ（Label Release）が有効でない場合（ステップ６０１；Ｎｏ）、または当該ＭＰＬＳメッセージ（Label Release）が送信済みのＭＰＬＳメッセージ（Label Withdraw）への応答である場合（ステップ６０２；Ｙｅｓ）、または対応するＡＴＭ回線が存在しない場合（ステップ６０３；Ｎｏ）は、当該ＭＰＬＳメッセージ（Label Release）は無視される（ステップ６０６）。
【００４６】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２からラベル要求取消のＭＰＬＳメッセージ（Label Abort Request）を受信すると、例えば図１３のフローチャートに示す処理を実行する。即ち、当該ＭＰＬＳメッセージ（Label Abort Request）が有効であるか否か調べる（ステップ７０１）。有効であれば（ステップ７０１；Ｙｅｓ）、このＭＰＬＳメッセージ（Label Abort Request）と対応するラベル要求のＭＰＬＳメッセージ（Label Request）に対し、ラベル通知のＭＰＬＳメッセージ（Label Mapping）で既に応答しているか否か、例えば管理テーブル１８の管理レコード１９の内容から確認する（ステップ７０２）。未だ応答していなければ（ステップ７０２；Ｎｏ）、バックボーンＡＴＭ交換機４に回線解放のＡＴＭメッセージ（RELEASE）を送信する（ステップ７０３）。そして、ＬＥＲ２には通知のＭＰＬＳメッセージ（Notification）を送信する（ステップ７０４）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレスとＡＴＭのＣＲとの対応関係管理を終了する（ステップ７０５）。一方、当該ラベル要求取消のＭＰＬＳメッセージ（Label Abort Request）が有効でない場合（ステップ７０１；Ｎｏ）、またはラベル通知のＭＰＬＳメッセージ（Label Mapping）で既に応答している場合（ステップ７０２；Ｙｅｓ）は、当該ＭＰＬＳメッセージ（Label Abort Request）は無視される（ステップ７０６）。
【００４７】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２からラベル取消のＭＰＬＳメッセージ（Label Withdraw）を受信すると、例えば図１４のフローチャートに示す処理を実行する。即ち、当該ＭＰＬＳメッセージ（Label Withdraw）が有効であるか否か調べる（ステップ８０１）。有効であれば（ステップ８０１；Ｙｅｓ）、対応するＡＴＭ回線が存在するか調べる（ステップ８０２）。即ち、ＭＰＬＳ／ＡＴＭ変換機能部１では、ＬＥＲ２から受信したＭＰＬＳメッセージ（Label Withdraw）中のＬＳＰＩＤや宛先ＩＰアドレスをキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＡＴＭ回線を把握する。そして、対応するＡＴＭ回線が存在すれば（ステップ８０２；Ｙｅｓ）、バックボーンＡＴＭ交換機４にＡＴＭメッセージ（RELEASE）を送信する（ステップ８０３）。そして、ＬＥＲ２にはＭＰＬＳメッセージ（Label Release）を送信する（ステップ８０４）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ８０５）。一方、当該ラベル取消のＭＰＬＳメッセージ（Label Withdraw）が有効でない場合（ステップ８０１；Ｎｏ）、または対応するＡＴＭ回線が存在しない場合（ステップ８０２；Ｎｏ）は、当該ＭＰＬＳメッセージ（Label Abort Request）は無視される（ステップ８０６）。
【００４８】
また、加入者系ＡＴＭ交換機３（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２から通知のＭＰＬＳメッセージ（Notification）を受信すると、例えば図１５のフローチャートに示す処理を実行する。即ち、当該ＭＰＬＳメッセージ（Notification）が有効であるか否か調べる（ステップ９０１）。有効であれば（ステップ９０１；Ｙｅｓ）、当該ＭＰＬＳメッセージ（Notification）が特定のＭＰＬＳ回線に関するメッセージであるか否か調べ、さらに対応するＡＴＭ回線が存在するか否か、例えば管理テーブル１８の管理レコード１９の内容から調べる（ステップ９０２）。例えばＭＰＬＳメッセージ（Notification）の内容が、ＬＳＰ（Label Switched Path）設定の失敗等に起因する特定のＭＰＬＳ回線に関するメッセージであって、対応するＡＴＭ回線が存在すれば（ステップ９０２；Ｙｅｓ）、バックボーンＡＴＭ交換機４に回線解放のＡＴＭメッセージ（RELEASE）を送信する（ステップ９０３）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ９０４）。一方、当該ＭＰＬＳメッセージ（Notification）が特定のＭＰＬＳ回線に関するメッセージではなく対応するＡＴＭ回線が存在しない場合（ステップ９０２；Ｎｏ）は、重大なシステム障害を通知するメッセージであるか否か確認する（ステップ９０５）。重大なシステム障害を通知するメッセージであれば（ステップ９０５；Ｙｅｓ）、バックボーンＡＴＭ交換機４に、すべてのＡＴＭ回線に対する回線解放のＡＴＭメッセージ（RELEASE）を送信する（ステップ９０６）。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ９０４）。この他、当該ＭＰＬＳメッセージ（Notification）が有効でない場合（ステップ９０１；Ｎｏ）、または当該ＭＰＬＳメッセージ（Notification）が特定のＭＰＬＳ回線に関するメッセージではなく重大なシステム障害を通知するメッセージではない場合は（ステップ９０５；Ｎｏ）、当該ＭＰＬＳメッセージ（Notification）は無視される（ステップ９０７）。
【００４９】
次に、以上のように構成される通信システムの品質保証提供可能な論理的な通信路の設定例（図１）、品質保証提供可能な論理的な通信路の設定不可例（図２）、品質保証提供可能な論理的な通信路の解放例（図３）について説明する。なお、本発明に係る主要なメッセージ及び動作のみ記し、明記しない部分（例えばＬＡＮ端末５とＬＥＲ２間の通信等）は、既知の通信技術及び通信方法によるものとする。
【００５０】
先ず、品質保証提供可能な論理的な通信路の設定例を図１を用いて説明する。図１は、自営通信網のＡ支店１１のＬＡＮ端末５ａからＢ支店１２のＬＡＮ端末５ｂにＩＰトラヒックを送信するために、ＬＥＲ２ａからＬＥＲ２ｂに品質保証提供可能である論理的な通信路の設定をする場合を示したものである。従って、本例では、Ａ支店１１側が送信側、Ｂ支店１２側が受信側となる。
【００５１】
ここで、送信側ＬＡＮ端末のＩＰアドレスを例えば「ａ．ａ．１．１」とする。また、送信側ＬＥＲ２ａのＩＰアドレスを例えば「ａ．ａ．１．０」とする。一方、受信側ＬＡＮ端末のＩＰアドレスを例えば「ｂ．ｂ．２．２」とする。また、受信側ＬＥＲ２ｂのＩＰアドレスを例えば「ｂ．ｂ．２．０」とする。
【００５２】
ＬＥＲ２ａは、ＩＰアドレス「ｂ．ｂ．２．２」に対するラベル要求を行うべく、ラベル要求のＭＰＬＳメッセージ（Label Request）を加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）に送信する。図１中矢印７ａは当該メッセージ送信のイメージを示す。この場合のＭＰＬＳメッセージのパラメータは例えば、ＬＳＰＩＤ＝Ｌ１、宛先ＩＰアドレス＝ｂ．ｂ．２．２、要求品質＝（PDR=W、PBS=B、CDR=W、CBS=B、EBS=0、Frequency=Frequent）とする。
【００５３】
加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２ａからラベル要求のＭＰＬＳメッセージ（Label Request）を受信すると、先に説明した図７のフローチャートに示す処理を実行する。即ち、ＭＰＬＳメッセージ（Label Request）が有効であるか否か調べ（ステップ１０１）、有効であれば（ステップ１０１；Ｙｅｓ）、ＭＰＬＳ／ＡＴＭ変換機能部１にて宛先ＩＰアドレスをＡＴＭアドレスに変換する（ステップ１０２）。
【００５４】
そして、必要なパラメータ変換を行う（ステップ１０３）。ＭＰＬＳ／ＡＴＭ変換機能部１では、例えばＭＰＬＳメッセージ中のパラメータにおいてＰＤＲ＝ＣＤＲ、ＰＢＳ＝ＣＢＳ等であるから、ＭＰＬＳにおいて要求されたサービスがＤＳであると判断してＡＴＭ網ではＣＢＲとして扱うものとし、パラメータをＰＣＲ＝Ｗ’、ＣＤＶＴ＝Ｂ’に変換する。ここで、Ｗ’とＢ’は、ＭＰＬＳで用いるＷとＢの単位（ｂｙｔｅ／ｓｅｃ）を、ＡＴＭで用いる単位（ｃｅｌｌ／ｓｅｃ）にそれぞれ変換したものである。
【００５５】
そして、転送先のバックボーンＡＴＭ交換機４ａが存在するか否か確認する（ステップ１０４）。転送先のバックボーンＡＴＭ交換機４ａは存在するから（ステップ１０４；Ｙｅｓ）、次いでリソースの確保が可能であるか否か、即ち要求された伝送品質が提供可能であるか否か確認する（ステップ１０５）。リソース確保可能であれば（ステップ１０５；Ｙｅｓ）、ラベル要求のＭＰＬＳメッセージ（Label Request）を回線設定要求のＡＴＭメッセージ（SETUP）に変換し、当該ＡＴＭメッセージ（SETUP）を上記変換した所定パラメータとともに、バックボーンＡＴＭ交換機４ａに向けて送信する（ステップ１０６）。図１中矢印７ｂは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、宛先ＡＴＭアドレス＝Z（AFI=49、NP=b.b.2.2.32.0.0.0.0.0.0.0、ESI=0.0.0.0.0.0、SEL=0）、ＣＲ＝Ｒ１、要求品質＝ＣＢＲ（ＰＣＲ＝Ｗ’、ＣＤＶＴ＝Ｂ’）となる。
【００５６】
そして、ＭＰＬＳメッセージ（Label Request）中のＬＳＰＩＤ（＝Ｌ１）と（図１６中符号２０参照）、宛先ＩＰアドレス（＝ｂ．ｂ．２．２）と（図１６中符号２１参照）、ＡＴＭメッセージ（SETUP）中のＣＲ（＝Ｒ１）とを（図１６中符号２２参照）、管理テーブル１８ａに記録し、対応付けて管理する（ステップ１０７）。
【００５７】
バックボーンＡＴＭ交換機４ａは、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）からＡＴＭメッセージ（SETUP）を受信すると、当該メッセージの中継を行う。バックボーンＡＴＭ交換機４ａでは、宛先ＡＴＭアドレスのＮＰ部１４の２バイト即ち「ｂ．ｂ」から転送先をバックボーンＡＴＭ交換機４ｂに決定する。そして、ＡＴＭメッセージ（SETUP）をバックボーンＡＴＭ交換機４ｂに送信する。図１中矢印７ｃは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＡＴＭアドレス＝Z（AFI=49、NP=b.b.2.2.32.0.0.0.0.0.0.0、ESI=0.0.0.0.0.0、SEL=0）、ＣＲ＝Ｒ２、要求品質＝ＣＢＲ（ＰＣＲ＝Ｗ’、ＣＤＶＴ＝Ｂ’）である。なお、ＣＲは、各ＡＴＭ交換機が個別に管理し、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）とバックボーンＡＴＭ交換機４ａとで一致している必要はない。
【００５８】
バックボーンＡＴＭ交換機４ｂは、バックボーンＡＴＭ交換機４ａからＡＴＭメッセージ（SETUP）を受信すると、当該メッセージの中継を行う。バックボーンＡＴＭ交換機４ｂでは、宛先ＡＴＭアドレスのＮＰ部１４の２バイト即ち「ｂ．ｂ」から加入者系ＡＴＭ交換機３ｂに転送を決定する。そして、ＡＴＭメッセージ（SETUP）を加入者系ＡＴＭ交換機３ｂに送信する。図１中矢印７ｄは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＡＴＭアドレス＝Z（AFI=49、NP=b.b.2.2.32.0.0.0.0.0.0.0、ESI=0.0.0.0.0.0、SEL=0）、ＣＲ＝Ｒ３、要求品質＝ＣＢＲ（ＰＣＲ＝Ｗ’、ＣＤＶＴ＝Ｂ’）である。
【００５９】
加入者系ＡＴＭ交換機３ｂ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４ｂから回線設定要求のＡＴＭメッセージ（SETUP）を受信すると、先に説明した図８のフローチャートに示す処理を実行する。即ち、ＡＴＭメッセージ（SETUP）が有効であるか否か調べ（ステップ２０１）、有効であれば（ステップ２０１；Ｙｅｓ）、宛先ＡＴＭアドレスのＥＳＩ部１５がＭＰＬＳ用特番であるか否か調べる（ステップ２０２）。宛先ＡＴＭアドレスのＥＳＩ部１５はＭＰＬＳ用特番であるから、ＭＰＬＳ／ＡＴＭ変換機能部１はＩＰアドレスに変換する必要があることを認識し（ステップ２０２；Ｙｅｓ）、ＡＴＭアドレスからＩＰアドレスへの変換を行う（ステップ２０３）。即ち、ＡＴＭアドレスのＮＰ部１４から宛先ＩＰアドレス「ｂ．ｂ．２．２」を得る。
【００６０】
そして、必要なパラメータ変換を行う（ステップ２０４）。即ち、送信側である加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）のＭＰＬＳ／ＡＴＭ変換機能部１にて行われたパラメータ変換と逆の変換を行う。これにより、要求品質が「PDR=W、PBS=B、CDR=W、CBS=B、EBS=0、Frequency=Frequent」であると認識する。
【００６１】
そして、転送先のＬＥＲ２ｂが存在するか否か確認する（ステップ２０５）。転送先のＬＥＲ２ｂは存在するから（ステップ２０５；Ｙｅｓ）、次いでリソースの確保が可能であるか否か、即ち要求された伝送品質が提供可能であるか否か確認する（ステップ２０６）。リソース確保可能であれば（ステップ２０６；Ｙｅｓ）、回線設定要求のＡＴＭメッセージ（SETUP）をラベル要求のＭＰＬＳメッセージ（Label Request）に変換し、当該ＭＰＬＳメッセージを上記変換した所定パラメータとともに、ＬＥＲ２ｂに向けて送信する（ステップ２０７）。図１中矢印７ｅは当該送信のイメージを示す。この場合のＭＰＬＳメッセージのパラメータは、ＬＳＰＩＤ＝Ｌ２、宛先ＩＰアドレス＝ｂ．ｂ．２．２、要求品質＝（PDR=W、PBS=B、CDR=W、CBS=B、EBS=0、Frequency=Frequent）となる。
【００６２】
そして、ＡＴＭメッセージ（SETUP）中のＣＲ（＝Ｒ３）と（図１６中符号２３）、ＭＰＬＳメッセージ（Label Request）中のＬＳＰＩＤ（＝Ｌ２）と（図１６中符号２４）、宛先ＩＰアドレス（＝ｂ．ｂ．２．２）とを（図１６中符号２５）、管理テーブル１８ｂに記録し、対応付けて管理する（ステップ２０８）。なお、ＬＳＰＩＤは加入者系ＡＴＭ交換機３ｂで独自に設定して構わない。従って、管理テーブル１８ｂで記録管理されるＬＳＰＩＤ（＝Ｌ２）が、ＬＥＲ２ａが発行したＭＰＬＳメッセージ（Label Request）に含まれるＬＳＰＩＤ（＝Ｌ１）と一致している必要はない。
【００６３】
ＬＥＲ２ｂは、加入者系ＡＴＭ交換機３ｂ（ＭＰＬＳ／ＡＴＭ変換機能部１）からラベル要求のＭＰＬＳメッセージ（Label Request）を受信すると、ＭＰＬＳ用のラベルを決定する。なお、本実施形態では、ラベルとして、ＡＴＭセルのＶＰＩ／ＶＣＩを用いるものとしている。そして、ラベル通知のＭＰＬＳメッセージ（Label Mapping）を加入者系ＡＴＭ交換機３ｂ（ＭＰＬＳ／ＡＴＭ変換機能部１）に向けて送信する。図１中矢印７ｆは当該送信のイメージを示す。この場合のＭＰＬＳメッセージのパラメータは、ＬＳＰＩＤ＝Ｌ２、宛先ＩＰアドレス＝ｂ．ｂ．２．２、例えばラベル（ＶＰＩ／ＶＣＩ）＝Ｐ１／Ｃ１とする。
【００６４】
加入者系ＡＴＭ交換機３ｂ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２ｂからラベル通知のＭＰＬＳメッセージ（Label Mapping）を受信すると、先に説明した図９のフローチャートに示す処理を実行する。即ち、ＭＰＬＳメッセージ（Label Mapping）が有効であるか否か調べ（ステップ３０１）、有効であれば（ステップ３０１；Ｙｅｓ）、対応する設定待ちのＡＴＭ回線が存在するか調べる（ステップ３０２）。即ち、ＭＰＬＳ／ＡＴＭ変換機能部１では、ＬＥＲ２ｂから受信したＭＰＬＳメッセージ（Label Mapping）中のＬＳＰＩＤ（＝Ｌ２）や宛先ＩＰアドレス（＝ｂ．ｂ．２．２）をキーとして管理テーブル１８ｂから該当する管理レコード１９を検索し、該当するＡＴＭ回線（ＣＲ＝Ｒ３）を把握する（ステップ３０２；Ｙｅｓ）。そして、ＶＰＩ／ＶＣＩを決定し（ステップ３０３）、ラベル通知のＭＰＬＳメッセージ（Label Mapping）を回線設定完了のＡＴＭメッセージ（CONNECT）に変換してバックボーンＡＴＭ交換機４ｂに向けて送信する（ステップ３０４）。図１中矢印７ｇは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＣＲ＝Ｒ３、ＶＰＩ／ＶＣＩ＝Ｐ２／Ｃ２である。
【００６５】
そして、管理テーブル１８ｂの所定管理レコード１９に、ＬＥＲ２ｂから受信したＭＰＬＳメッセージ（Label Mapping）中のＭＰＬＳ用のラベル（＝Ｐ１／Ｃ１）と（図１６中符号２６）、バックボーンＡＴＭ交換機４ｂに送信したＡＴＭメッセージ（CONNECT）のＶＰＩ／ＶＣＩ（＝Ｐ２／Ｃ２）と（図１６中符号２７）を記録する。これにより、ＭＰＬＳのＬＳＰＩＤ（＝Ｌ２）と、宛先ＩＰアドレス（＝ｂ．ｂ．２．２）と、ラベル（＝Ｐ１／Ｃ１）と、ＡＴＭのＣＲ（＝Ｒ３）と、ＶＰＩ／ＶＣＩ（＝Ｐ２／Ｃ２）とが管理テーブル１８ｂ上で対応付けて管理される（ステップ３０５）。
【００６６】
バックボーンＡＴＭ交換機４ｂは、加入者系ＡＴＭ交換機３ｂから回線設定完了のＡＴＭメッセージ（CONNECT）を受信すると、当該メッセージを中継するべくバックボーンＡＴＭ交換機４ａに送信する。図１中矢印７ｈは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＣＲ＝Ｒ２、例えばＶＰＩ／ＶＣＩ＝Ｐ３／Ｃ３とする。
【００６７】
バックボーンＡＴＭ交換機４ａは、バックボーンＡＴＭ交換機４ｂから回線設定完了のＡＴＭメッセージ（CONNECT）を受信すると、当該メッセージを中継するべく加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）に送信する。図１中矢印７ｉは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＣＲ＝Ｒ１、例えばＶＰＩ／ＶＣＩ＝Ｐ４／Ｃ４とする。
【００６８】
加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４ａから回線設定完了のＡＴＭメッセージ（CONNECT）を受信すると、先に説明した図１０のフローチャートに示す処理を実行する。即ち、ＡＴＭメッセージ（CONNECT）が有効であるか否か調べ（ステップ４０１）、有効であれば（ステップ４０１；Ｙｅｓ）、対応する設定待ちのＭＰＬＳ回線が存在するか調べる（ステップ４０２）。ＭＰＬＳ／ＡＴＭ変換機能部１では、例えばバックボーンＡＴＭ交換機４ａから受信したＡＴＭメッセージ（CONNECT）のＣＲ（＝Ｒ１）をキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＭＰＬＳ回線を把握する（ステップ４０２；Ｙｅｓ）。そして、ＭＰＬＳ用のラベルを決定し（ステップ４０３）、回線設定完了のＡＴＭメッセージ（CONNECT）をラベル通知のＭＰＬＳメッセージ（Label Mapping）に変換してＬＥＲ２ａに向けて送信する（ステップ４０４）。図１中矢印７ｊは当該送信のイメージを示す。この場合のＭＰＬＳメッセージのパラメータは、ＬＳＰＩＤ＝Ｌ１、 宛先ＩＰアドレス＝ｂ．ｂ．２．２、例えばラベル（ＶＰＩ／ＶＣＩ）＝Ｐ５／Ｃ５とする。
【００６９】
そして、管理テーブル１８ａの所定管理レコード１９に、バックボーンＡＴＭ交換機４ａから受信したＡＴＭメッセージ（CONNECT）のＶＰＩ／ＶＣＩ（＝Ｐ４／Ｃ４）と（図１６中符号２８）、ＬＥＲ２ａに送信したＭＰＬＳメッセージ（Label Mapping）中のＭＰＬＳ用のラベル（＝Ｐ５／Ｃ５）と（図１６中符号２９）を記録する。これにより、ＭＰＬＳのＬＳＰＩＤ（＝Ｌ１）と、宛先ＩＰアドレス（＝ｂ．ｂ．２．２）と、ラベル（＝Ｐ５／Ｃ５）と、ＡＴＭのＣＲ（＝Ｒ１）と、ＶＰＩ／ＶＣＩ（＝Ｐ４／Ｃ４）とが管理テーブル１８ａ上で対応付けて管理される（ステップ４０５）。
【００７０】
ＬＥＲ２ａにラベル通知されることにより、宛先ＩＰアドレス（＝ｂ．ｂ．２．２）にラベルが設定され、ＬＥＲ２ａとＬＥＲ２ｂとの間で品質保証提供可能な論理的な通信路が設定される。ＬＥＲ２ａ，ＬＥＲ２ｂによりラベルを利用したＭＰＬＳの持つ品質要求機能が実現され、実際の品質保証は、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１），バックボーンＡＴＭ交換機４ａ，バックボーンＡＴＭ交換機４ｂ，加入者系ＡＴＭ交換機３ｂにより設定されたＡＴＭ回線で実現される。
【００７１】
次に、品質保証提供可能な論理的な通信路の設定不可例を図２を用いて説明する。図２は、自営通信網のＡ支店１１のＬＡＮ端末５ａがＢ支店１２のＬＡＮ端末５ｂにＩＰトラヒックを送信するべく、ＬＥＲ２ａからＬＥＲ２ｂに品質保証提供可能な論理的な通信路を設定しようとしたが、バックボーンＡＴＭ交換機４ａとバックボーンＡＴＭ交換機４ｂとの間で帯域が不足し、設定できなかった場合を示したものである。
【００７２】
ＬＥＲ２ａがラベル要求のＭＰＬＳメッセージ（Label Request）を加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）に送信する処理（図２中矢印８ａは当該送信のイメージを示す）は、図１に示した例と同様である。
【００７３】
また、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）が、回線設定要求のＡＴＭメッセージ（SETUP）を所定パラメータとともに、バックボーンＡＴＭ交換機４ａに向けて送信する処理（図２中矢印８ｂは当該送信のイメージを示す）は、図１に示した例と同様である。
【００７４】
バックボーンＡＴＭ交換機４ａは、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）からＡＴＭメッセージ（SETUP）を受信すると、宛先ＡＴＭアドレスのＮＰ部１４の２バイト即ち「ｂ．ｂ」からバックボーンＡＴＭ交換機４ｂに転送を決定し、当該メッセージの中継を試みる。しかし、バックボーンＡＴＭ交換機４ａは、要求された伝送品質に対する帯域不足を認識したため、ＡＴＭメッセージ（SETUP）の送信を行わない。図２中矢印８ｃは当該送信中止のイメージを示す。
【００７５】
そして、バックボーンＡＴＭ交換機４ａは、回線解放のＡＴＭメッセージ（RELEASE）を加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）に送信する。図２中矢印８ｄは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＣＲ＝Ｒ１、状況＝帯域不足とする。
【００７６】
加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４ａから回線解放のＡＴＭメッセージ（RELEASE）を受信すると、先に説明した図１１のフローチャートに示す処理を実行する。即ち、ＡＴＭメッセージ（RELEASE）が有効であるか否か調べ（ステップ５０１）、有効であれば（ステップ５０１；Ｙｅｓ）、対応するＭＰＬＳ回線が存在するか調べる（ステップ５０２）。ＭＰＬＳ／ＡＴＭ変換機能部１では、例えばバックボーンＡＴＭ交換機４ａから受信したＡＴＭメッセージ（RELEASE）のＣＲ（＝Ｒ１）をキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＭＰＬＳ回線を把握する（ステップ５０２；Ｙｅｓ）。次いで、バックボーンＡＴＭ交換機４ａから受信した当該ＡＴＭメッセージ（RELEASE）が、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）が先に送信したＡＴＭメッセージ（SETUP）に対する応答か否か確認する（ステップ５０３）。当該ＡＴＭメッセージ（RELEASE）は、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）が先に送信したＡＴＭメッセージ（SETUP）に対する応答であるから（ステップ５０３；Ｙｅｓ）、ＬＥＲ２ａに向けて通知のＭＰＬＳメッセージ（Notification）を送信する（ステップ５０４）。図２中矢印８ｅは当該送信のイメージを示す。この場合のＭＰＬＳメッセージのパラメータは、ＬＳＰＩＤ＝Ｌ１、理由＝帯域不足とする。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレスとＡＴＭのＣＲとの対応関係管理を終了する（ステップ５０５）。
【００７７】
次に、品質保証提供可能な論理的な通信路の解放例を図３を用いて説明する。図３は、図１にて設定した品質保証提供可能な論理的な通信路をＬＥＲ２ａから解放する場合を示したものである。
【００７８】
ＬＥＲ２ａは、ＩＰアドレス「ｂ．ｂ．２．２」に対するラベル解放を行うべく、ラベル解放のＭＰＬＳメッセージ（Label Release）を加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）に送信する。図３中矢印９ａは当該メッセージ送信のイメージを示す。この場合のＭＰＬＳメッセージのパラメータは例えば、ＬＳＰＩＤ＝Ｌ１、宛先ＩＰアドレス＝ｂ．ｂ．２．２である。
【００７９】
加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、ＬＥＲ２ａからラベル解放のＭＰＬＳメッセージ（Label Release）を受信すると、先に説明した図１２のフローチャートに示す処理を実行する。即ち、ＭＰＬＳメッセージ（Label Release）が有効であるか否か調べる（ステップ６０１）。有効であれば（ステップ６０１；Ｙｅｓ）、次いで当該ＭＰＬＳメッセージが、既に加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）からＬＥＲ２ａに送信済みであるＭＰＬＳメッセージ（Label Withdraw）への応答であるか否か判断する（ステップ６０２）。当該応答ではないから（ステップ６０２；Ｎｏ）、対応するＡＴＭ回線が存在するか否か調べる（ステップ６０３）。即ち、ＭＰＬＳ／ＡＴＭ変換機能部１では、ＬＥＲ２ａから受信したＭＰＬＳメッセージ（Label Release）中のＬＳＰＩＤ（＝Ｌ１）や宛先ＩＰアドレス（＝ｂ．ｂ．２．２）をキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＡＴＭ回線（ＣＲ＝Ｒ１）を把握する（ステップ６０３；Ｙｅｓ）。そして、ラベル解放のＭＰＬＳメッセージ（Label Release）を回線解放のＡＴＭメッセージ（RELEASE）に変換してバックボーンＡＴＭ交換機４ａに向けて送信する（ステップ６０４）。図３中矢印９ｂは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＣＲ＝Ｒ１とする。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ６０５）。
【００８０】
バックボーンＡＴＭ交換機４ａは、加入者系ＡＴＭ交換機３ａ（ＭＰＬＳ／ＡＴＭ変換機能部１）から回線解放のＡＴＭメッセージ（RELEASE）を受信すると、当該メッセージを中継するべくバックボーンＡＴＭ交換機４ｂに送信する。図３中矢印９ｃは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＣＲ＝Ｒ２である。
【００８１】
バックボーンＡＴＭ交換機４ｂは、バックボーンＡＴＭ交換機４ａから回線解放のＡＴＭメッセージ（RELEASE）を受信すると、当該メッセージを中継するべく加入者系ＡＴＭ交換機３ｂに送信する。図３中矢印９ｄは当該送信のイメージを示す。この場合のＡＴＭメッセージのパラメータは、ＣＲ＝Ｒ３である。
【００８２】
加入者系ＡＴＭ交換機３ｂ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４ｂから回線解放のＡＴＭメッセージ（RELEASE）を受信すると、先に説明した図１１のフローチャートに示す処理を実行する。即ち、ＡＴＭメッセージ（RELEASE）が有効であるか否か調べ（ステップ５０１）、有効であれば（ステップ５０１；Ｙｅｓ）、対応するＭＰＬＳ回線が存在するか調べる（ステップ５０２）。即ち、ＭＰＬＳ／ＡＴＭ変換機能部１では、バックボーンＡＴＭ交換機４ｂから受信したＡＴＭメッセージ（RELEASE）のＣＲ（＝Ｒ３）をキーとして管理テーブル１８から該当する管理レコード１９を検索し、該当するＭＰＬＳ回線を把握する（ステップ５０２；Ｙｅｓ）。加入者系ＡＴＭ交換機３ｂ（ＭＰＬＳ／ＡＴＭ変換機能部１）は、バックボーンＡＴＭ交換機４ａから設定済みの回線の解放を要求されており（ステップ５０３；Ｎｏ、ステップ５０７；Ｎｏ）、加入者系ＡＴＭ交換機３ｂ（ＭＰＬＳ／ＡＴＭ変換機能部１）と対向するＬＥＲ２ｂはラベル要求側でなくラベルを要求された側であるから（ステップ５１０；Ｎｏ）、ＬＥＲ２ｂに向けてラベル解放のＭＰＬＳメッセージ（Label Release）を送信する（ステップ５０９）。図３中矢印９ｅは当該送信のイメージを示す。この場合のＭＰＬＳメッセージのパラメータは、ＬＳＰＩＤ＝Ｌ２、宛先ＩＰアドレス＝ｂ．ｂ．２．２とする。そして、該当する管理レコード１９を管理テーブル１８上から削除し、該当するＭＰＬＳのＬＳＰＩＤ及び宛先ＩＰアドレス及びラベルと、ＡＴＭのＣＲ及びＶＰＩ／ＶＣＩとの対応関係管理を終了する（ステップ５０５）。
【００８３】
以上のように本発明の通信システム及び通信方法によれば、加入者系ＡＴＭ交換機３に簡易に実現可能なＭＰＬＳ／ＡＴＭ変換機能部１を実装し、ＬＥＲ２と加入者系ＡＴＭ交換機３を接続することにより、ＭＰＬＳの持つ品質要求機能をＬＥＲ２で実現し、実際の品質保証はＡＴＭ網で行うことができる。上記説明から明らかなように、バックボーンＡＴＭ網１０には変更を加える必要はまったくない。また、ＭＰＬＳドメインを新たに構築することなく、ＭＰＬＳ／ＡＴＭ変換機能部１を実装した加入者系ＡＴＭ換機３にＬＥＲ２を接続するのみでＭＰＬＳの品質機能を導入することができる。したがって、既存のＡＴＭ網を利用して、ＩＰトラヒックに容易に品質保証を提供することができる。
【００８４】
また、本発明では、ＩＰアドレスとＡＴＭアドレスを共に例えば組織階層に合わせた体系にすることにより、ＩＰアドレスとＡＴＭアドレスに明確な関係を持たせることで、容易かつ高速にアドレス変換可能である。
【００８５】
また、ＭＰＬＳ回線とＡＴＭ回線との対応関係を管理することで、ＡＴＭの回線設定不可等の他のメッセージを受信した場合でも、ＣＲやＬＳＰＩＤにより対象となる回線を認識でき、適切な処理が可能となる。
【００８６】
なお、上述の実施形態は本発明の好適な実施の一例ではあるがこれに限定されるものではなく、本発明の要旨を逸脱しない範囲において種々変形実施可能である。ＩＰアドレスとＡＴＭアドレスを共に組織階層に合わせた体系にし、ＩＰアドレスとＡＴＭアドレスに明確な関係を持たせることは、容易かつ高速なアドレス変換を行うための本発明の好適な一例ではあるが、必ずしもこの例に限定されるものではない。例えば小規模自営通信網等で、予め全てのＩＰアドレスとＡＴＭアドレスを把握できる場合等には、ＭＰＬＳ／ＡＴＭ変換機能部１にてＩＰアドレスとＡＴＭアドレスとの対応関係を把握できる変換対応表等を保持しておき、当該変換対応表に基いてアドレス変換を行なうようにしても良い。この場合、ＭＰＬＳ／ＡＴＭ変換機能部１は、加入者系ＡＴＭ交換機３を構成するコンピュータにＭＰＬＳ／ＡＴＭ変換プログラムを実行させて実現させるものに必ずしも限定されない。例えば、加入者系ＡＴＭ換機３とＬＥＲ２とを接続するゲートウェイ装置としてＭＰＬＳ／ＡＴＭ変換機能部１を実現させても良い。
【００８７】
【発明の効果】
以上の説明から明らかなように、請求項１記載の通信システム及び請求項５記載の通信方法及び請求項６記載のＭＰＬＳ／ＡＴＭ変換プログラムによれば、バックボーンＡＴＭ網には変更を加えることなく、ＭＰＬＳの持つ品質要求機能をラベルエッジルータで実現して、実際の品質保証はＡＴＭ網で行うことができる。したがって、例えば既存のＡＴＭ網を利用して、ＩＰトラヒックに容易に品質保証を提供することができる。また、ＭＰＬＳ回線とＡＴＭ回線との対応関係を管理することで、ＡＴＭの回線設定不可等の他のメッセージを受信した場合でも、対象となる回線を認識でき、適切な処理が可能となる。
【００８８】
さらに、請求項２記載の通信システムによれば、ＩＰアドレスとＡＴＭアドレスに明確な関係を持たせることで、容易かつ高速にアドレス変換可能である。
【００８９】
さらに、請求項３記載の通信システムによれば、ＭＰＬＳ／ＡＴＭ変換機能部にてＭＰＬＳ変換認識用コードの有無を調べることで、終端ＡＴＭ交換機にＡＴＭ端末が接続されている場合に、ラベルエッジルータに対するＭＰＬＳ／ＡＴＭ変換処理をすべきか、またはＡＴＭ端末に対する通常のＡＴＭ処理をすべきか等を容易に判断することができる。
【００９０】
さらに、請求項４記載の通信システムによれば、ＭＰＬＳメッセージまたはＡＴＭメッセージの変換または復元に際して、メッセージに含まれるパラメータの変換も併せて行うようにしているので、ＩＰトラヒックに、より柔軟かつ高度の品質保証の提供が可能となる。
【図面の簡単な説明】
【図１】本発明の通信システムの実施の一形態を示す概略構成図であり、品質保証提供可能な論理的な通信路の設定例を示す。
【図２】本発明の通信システムの実施の一形態を示す概略構成図であり、品質保証提供可能な論理的な通信路の設定不可例を示す。
【図３】本発明の通信システムの実施の一形態を示す概略構成図であり、品質保証提供可能な論理的な通信路の解放例を示す。
【図４】ＩＰアドレスからＡＴＭアドレスへ変換する一例を示す概念図である。
【図５】ＡＴＭアドレスからＩＰアドレスへ変換する処理の一例を示すフローチャートである。
【図６】ＭＰＬＳメッセージとＡＴＭメッセージの対応関係を表すメッセージ変換テーブルの一例を示す概念図である。
【図７】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、ラベルエッジルータからラベル要求のＭＰＬＳメッセージを受信した場合の処理の一例を示すフローチャートである。
【図８】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、バックボーンＡＴＭ交換機から回線設定要求のＡＴＭメッセージを受信した場合の処理の一例を示すフローチャートである。
【図９】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、ラベルエッジルータからラベル通知のＭＰＬＳメッセージを受信した場合の処理の一例を示すフローチャートである。
【図１０】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、バックボーンＡＴＭ交換機から回線設定完了のＡＴＭメッセージを受信した場合の処理の一例を示すフローチャートである。
【図１１】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、バックボーンＡＴＭ交換機から回線解放のＡＴＭメッセージを受信した場合の処理の一例を示すフローチャートである。
【図１２】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、ラベルエッジルータからラベル解放のＭＰＬＳメッセージを受信した場合の処理の一例を示すフローチャートである。
【図１３】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、ラベルエッジルータからラベル要求取消のＭＰＬＳメッセージを受信した場合の処理の一例を示すフローチャートである。
【図１４】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、ラベルエッジルータからラベル取消のＭＰＬＳメッセージを受信した場合の処理の一例を示すフローチャートである。
【図１５】ＭＰＬＳ／ＡＴＭ変換機能部を実装した終端ＡＴＭ交換機が、ラベルエッジルータから通知のＭＰＬＳメッセージを受信した場合の処理の一例を示すフローチャートである。
【図１６】ＭＰＬＳ回線とＡＴＭ回線との対応関係を管理するための管理テーブルの一例を示す概念図である。
【図１７】本発明におけるＡＴＭ端末のＡＴＭアドレスの一例を示す概念図である。
【図１８】ＩＰアドレスからＡＴＭアドレスへ変換した一例を示す概念図である。
【図１９】ＩＰアドレスからＡＴＭアドレスへ変換する処理の一例を示す概念図である。
【符号の説明】
１ ＭＰＬＳ／ＡＴＭ変換機能部
２ ＬＥＲ（ラベルエッジルータ）
３ 加入者系ＡＴＭ交換機（終端ＡＴＭ交換機）
４ バックボーンＡＴＭ交換機[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for providing quality assurance for IP traffic. More specifically, the present invention relates to a communication system, a communication method, and a program for performing mutual conversion between ATM (Asynchronous Transfer Mode) and MPLS (MultiProtocol Label Switching).
[0002]
[Prior art]
By using IP (Internet Protocol), various networks can be connected to form a large internetwork, and each network can be operated seamlessly. However, when dealing with variable-length IP packets, it becomes difficult to control the delay time, and it is difficult to guarantee strict transmission quality. The transmission quality generally has parameters such as transmission delay, fluctuation (delay variation), minimum guaranteed speed, and peak speed. ATM is a technique for guaranteeing such transmission quality. For this reason, a network configuration for constructing an IP network on an ATM network is considered promising. Conventional techniques for providing quality assurance for IP traffic using ATM include LANE (Local Area Network Emulation) and MPOA (Multiprotocol over ATM).
[0003]
In addition, although not particularly limited to those using ATM, MPLS is a technology for providing quality assurance for IP traffic. In MPLS, a protocol called CR-LDP (Constraint-based Routing-Label Distribution Protocol) is used, a label corresponding to the required quality is added to a variable-length IP packet, and quality control is performed according to the label.
[0004]
[Problems to be solved by the invention]
However, in the conventional LANE, communication between LANs is communication via a router, and the router does not provide quality assurance. Therefore, the quality of IP traffic across routers is not guaranteed.
[0005]
In addition, when providing quality assurance by MPOA, since there is generally no correlation between an IP address and an ATM address, complicated processing such as grasping a correspondence relationship by a server is required to perform address conversion. In addition, MPOA is not widely used due to the complexity of the protocol in addition to the problem that priority designation is impossible compared to the quality that MPLS intends to provide.
[0006]
Further, when providing quality assurance by means of MPLS, it is possible to provide quality assurance by using a header of a fixed-length ATM cell used in the ATM network as an MPLS label. However, in this case, it is necessary to change the software of all ATM exchanges in the ATM network. For this reason, when a new ATM-based MPLS network is constructed, it takes a lot of time and enormous costs and is not easy to introduce. In addition, MPLS is not a well-established technology, and when it is introduced to an ATM backbone network, there are concerns about strict quality assurance and operation management.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a communication system and communication method and an MPLS / ATM conversion program that can easily provide quality assurance for IP traffic.
[0008]
[Means for Solving the Problems]
In order to achieve this object, a communication system according to claim 1 is a label edge router having a backbone ATM switch constituting a backbone ATM network, a terminating ATM switch connected to the backbone ATM switch, and a function constituting an MPLS network. And an MPLS / ATM conversion function unit for connecting the label edge router and the terminating ATM switch to form a private communication network, and the MPLS / ATM conversion function unit obtains an IP address from which the label edge router requests label setting. A function for converting an ATM address according to a predetermined address conversion rule, a function for restoring an ATM address received by a terminating ATM switch from a backbone ATM switch to an IP address according to an address conversion rule, and an MPLS message transmitted from a label edge router in advance. Stipulated message A function of converting the ATM message according to the correspondence relationship, a function of restoring the ATM message received by the terminal ATM switch from the backbone ATM switch into an MPLS message according to the message correspondence relationship, an IP address at which the label edge router requests label setting, It is assumed that a label set for the IP address and a function for managing the correspondence between the MPLS line and the ATM line set for the label are provided.
[0009]
According to a fifth aspect of the present invention, there are provided a backbone ATM switch constituting a backbone ATM network, a terminal ATM switch connected to the backbone ATM switch, a label edge router having a function of constituting an MPLS network, and a label edge router. And an MPLS / ATM conversion function unit for connecting a terminal ATM switch and a terminal ATM switch to configure a private network, and the MPLS / ATM conversion function unit determines an IP address for which a label edge router requests a label setting in advance. The ATM address received from the backbone ATM switch is restored to the IP address according to the address conversion rule, and the MPLS message transmitted from the label edge router is converted into an ATM message according to a predetermined message correspondence. In other words, the ATM message received by the terminating ATM switch from the backbone ATM switch is restored to the MPLS message according to the message correspondence relationship, and the label address is requested by the label edge router, the label set to the IP address, The correspondence between the MPLS line and the ATM line set for the label is managed.
[0010]
According to another aspect of the present invention, there is provided an MPLS / ATM conversion program for terminating a terminal ATM switch connected to a backbone ATM switch and a label edge router having a function of configuring an MPLS network in a private network. A function that the label edge router converts an IP address that requires label setting into an ATM address according to a predetermined address conversion rule, and a terminal ATM switch that converts the ATM address received from the backbone ATM switch into a computer provided in the ATM switch A function for restoring the IP address according to the rules, a function for converting an MPLS message transmitted from the label edge router into an ATM message according to a predetermined message correspondence relationship, and an ATM message received from the backbone ATM switch by the terminating ATM switch. A function for restoring a message to an MPLS message according to a message correspondence relationship, an IP address for which a label edge router requests label setting, a label set for the IP address, and an MPLS line and an ATM line set for the label And a function for managing the correspondence.
[0011]
Therefore, the quality requirement function of MPLS can be realized by the label edge router, and actual quality assurance can be realized by the ATM network. For example: That is, the label edge router requests a label corresponding to the destination IP address for which the required quality is specified based on the quality request function of MPLS (the label edge router that has requested the label is referred to as an originating label edge router). . The MPLS message of the label request is sent to the line setting request according to a predetermined message correspondence relationship by an MPLS / ATM conversion function unit (hereinafter referred to as a calling side MPLS / ATM conversion function unit) connected to the calling side label edge router. To ATM messages. The ATM message is transmitted to the backbone ATM switch by the terminating ATM switch connected to the originating side MPLS / ATM conversion function unit (hereinafter referred to as the originating side terminating ATM switch), further transferred to the ATM backbone network, and sent to the destination IP. Arrives at the terminating ATM exchange on the opposite side to which the address belongs (hereinafter referred to as the terminating ATM exchange). The ATM message is restored to the MPLS message of the label request by the MPLS / ATM conversion function unit (hereinafter referred to as the called-side MPLS / ATM conversion function unit) connected to the terminating-end ATM exchange, and the called-side MPLS / ATM. The data is transmitted to a label edge router connected to the conversion function unit (that is, a label edge router for which a label is requested, hereinafter referred to as a called label edge router). When the receiving side label edge router responding to the label request notifies the label, the MPLS message of the label notification is converted into a line setting complete ATM message by the receiving side MPLS / ATM conversion function unit, and further received by the terminating side terminating ATM exchange. It is transmitted to the backbone ATM exchange, further transferred through the ATM backbone network, and arrives at the originating end ATM exchange. The ATM message is restored to the MPLS message of the label notification by the originating side MPLS / ATM conversion function unit, and transmitted to the originating side label edge router that requested the label. With the above operation, a logical communication path capable of providing quality assurance is configured between the originating label edge router and the terminating label edge router. Here, MPLS requests a label corresponding to the destination IP address, but an ATM address is required for line setting in the ATM network. Therefore, the destination MPLS address / ATM conversion function unit converts the destination IP address into an ATM address according to a predetermined address conversion rule. Based on the converted ATM address, the ATM message of the line setting request is transferred through the backbone ATM network and reaches the terminating end ATM exchange. The ATM address received by the terminating-end ATM switch is restored to an IP address according to a predetermined address conversion rule. As a result, the called label edge router can set a label for the IP address. In addition, since the correspondence between the MPLS line and the ATM line is managed by the MPLS / ATM conversion function unit, the target line can be identified even when other messages such as ATM line setting impossible are received, Appropriate processing becomes possible.
[0012]
According to a second aspect of the present invention, in the communication system according to the first aspect, the IP address and the ATM address are assigned in an organizational hierarchy, and the MPLS / ATM conversion function unit converts the IP address into the ATM address. The IP address is converted into an ATM address so as to include a part or all of the IP address.
[0013]
The terminal ATM switch, the label edge router, and the communication terminals connected to the label edge router are arranged in an organizational hierarchy. In accordance with this, ATM addresses or IP addresses of these devices are assigned in an organizational hierarchy. In this case, the backbone ATM switch can specify the terminal ATM switch to which data is to be transferred from the IP address part included in the ATM address. Further, when converting from an IP address to an ATM address and restoring from an ATM address to an IP address, complicated processing such as grasping and managing the correspondence between the IP address and the ATM address is unnecessary, and the IP address is converted into the ATM address. Address conversion can be performed easily and at high speed by writing the data as it is or by extracting the IP address from the ATM address.
[0014]
The invention described in claim 3 is the communication system according to claim 1 or 2, wherein the MPLS / ATM conversion function unit has a function of writing an MPLS conversion recognition code to an ATM address converted from an IP address. The terminating ATM switch checks the presence or absence of an MPLS conversion recognition code for the ATM address received from the backbone ATM switch, and if the MPLS conversion recognition code is present, has a function of restoring the ATM address to an IP address according to an address conversion rule. It is supposed to be. Therefore, when an ATM terminal is connected to the terminal ATM switch, it can be easily determined whether to perform MPLS / ATM conversion processing for the label edge router or normal ATM processing for the ATM terminal.
[0015]
According to a fourth aspect of the present invention, there is provided the communication system according to any one of the first to third aspects, wherein the MPLS / ATM conversion function unit has a predetermined parameter correspondence relationship when converting or restoring an MPLS message or an ATM message. Accordingly, the function included in the message is also converted or restored. It is possible to provide more flexible and high quality assurance for IP traffic.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.
[0017]
1 to 19 show an embodiment of a communication system according to the present invention. This communication system includes a backbone ATM switch 4 constituting a backbone ATM network 10, a terminating ATM switch 3 connected to the backbone ATM switch 4, a label edge router 2 having a function constituting an MPLS network, and a label edge router 2 And an MPLS / ATM conversion function unit 1 for connecting the terminal ATM switch 3 to the private ATM.
[0018]
The backbone ATM switch (also referred to as a relay ATM switch) 4 is, for example, four in the present embodiment for convenience of explanation, and is connected by a loop communication line to form a backbone ATM network (also referred to as a relay ATM network) 10. ing. The backbone ATM switch 4 is connected to, for example, a terminal ATM switch 3 (hereinafter referred to as a subscriber ATM switch 3) installed in the premises of the user. The subscriber ATM switch 3 is an ATM switch that accommodates the label edge router 2 and the ATM terminal. For example, a subscriber ATM switch 3 is installed in each of branch A (indicated by reference numeral 11 in FIG. 1) and branch B (indicated by reference numeral 12 in FIG. 1), and the subscriber ATM switch 3 is a backbone. It is connected to the ATM switch 4. Accordingly, when communication is performed between the A branch 11 and the B branch 12, the backbone ATM network 10 is always used.
[0019]
A label edge router (hereinafter abbreviated as LER) 2 is a known information processing apparatus having a function of accommodating IP traffic in an MPLS domain (that is, an area to which MPLS is applied). The LER 2 is connected to the subscriber ATM exchange 3 via the MPLS / ATM conversion function unit 1 and is connected to a communication terminal 5 that performs communication by IP traffic.
[0020]
The communication terminal 5 is a device for performing end-to-end bidirectional communication. For example, in this embodiment, the communication terminal 5 is a known personal computer or the like that has a communication function and is connected to a LAN. Hereinafter, the communication terminal is referred to as a LAN terminal 5. For example, the LAN terminal 5a of the branch A 11 is connected to the LER 2a via a communication line, and the LER 2a is connected to the subscriber ATM exchange 3a via a communication line. Similarly, the LAN terminal 5b of the branch B 12 is connected to the LER 2b via a communication line, and the LER 2b is connected to the subscriber ATM exchange 3b via a communication line.
[0021]
The MPLS / ATM conversion function unit 1 of the present embodiment mainly has the following three functions. First, the LER 2 converts the IP address for requesting label setting into an ATM address according to a predetermined address conversion rule, and the ATM address received by the subscriber ATM switch 3 from the backbone ATM switch 4 according to the address conversion rule. It has a function of restoring to an IP address. Second, a function for converting an MPLS message transmitted by LER2 into an ATM message according to a predetermined message correspondence, and an ATM message received from the backbone ATM exchange 3 by the subscriber ATM exchange 3 into an MPLS message according to the message correspondence. Has a function to restore. Third, the label edge router has a function of managing a correspondence relationship between an IP address requesting label setting, a label set in the IP address, and an MPLS line and an ATM line set for the label.
[0022]
The MPLS / ATM conversion function unit 1 of the present embodiment is realized by software (MPLS / ATM conversion program), for example. The MPLS / ATM conversion program is set up in the subscriber ATM exchange 3 and causes the computer (processing device) included in the subscriber ATM exchange 3 to realize the above functions. However, it goes without saying that the functions that can be implemented in hardware among the functions of the MPLS / ATM conversion function unit 1 may be realized as hardware. Hereinafter, a subscriber ATM switch 3 having an MPLS / ATM conversion function unit 1, that is, a subscriber ATM switch 3 in which an MPLS / ATM conversion program is set up, is referred to as a subscriber ATM switch 3 (MPLS / ATM conversion function unit 1). ).
[0023]
In the present embodiment, a protocol used between the LER 2 and the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) is, for example, CR-LDP. The protocol used between the subscriber ATM exchange 3 and the backbone ATM exchange 4 and within the backbone ATM network 10 is, for example, PNNI (Private Network-Network Interface).
[0024]
First, the IP address / ATM address conversion and restoration function of the MPLS / ATM conversion function unit 1 will be described. Since the present invention constitutes a private communication network, both the IP address and the ATM address can be freely set. Therefore, it is possible to assign an IP address or ATM address to a communication device so as to have a certain relationship between the IP address and the ATM address, or to grasp in advance the IP address and ATM address of each communication device. You can also keep it.
[0025]
For example, in this embodiment, in order to facilitate mutual conversion between an IP address and an ATM address, address assignment is performed with a clear relationship between the IP address and the ATM address. For example, as shown in the example of FIG. 1, network devices such as the subscriber ATM switch 3, the LER 2, and the LAN terminal 5 are generally arranged and configured corresponding to the organizational structure of the user. Therefore, in this embodiment, the IP address and the ATM address are assigned in an organizational hierarchy according to the organizational hierarchy of the user. The MPLS / ATM conversion function unit 1 has a function of converting an IP address into an ATM address so as to include a part or all of the IP address when converting the IP address into an ATM address.
[0026]
For example, in the case of IPv4, the IP address is composed of 4 bytes. Therefore, the following roles are assigned to each byte. For example, the first byte is a “part identifying the main store or branch”. For example, the second byte is “a part for identifying a business office (a sales office or the like) in a head office or a branch”. For example, the third byte is set as “a part for identifying a LAN (segment) in the office”. For example, the fourth byte is a “part for identifying a terminal in the LAN”. Accordingly, for example, the terminal “D” of the LAN “C” of the “B” sales office of the “A” branch office is given an IP address of “ABCD”.
[0027]
On the other hand, the ATM address is also assigned according to the organizational hierarchy, and has the same “portion identifying head office or branch” and “portion identifying office (branch office, etc.) in the head office or branch” that is the same as the IP address. . The ATM address includes, for example, an AFI (Authority and Format Identifier) unit 13, an NP (Network Prefix) unit 14, an ESI (End System Identifier) unit 15, and a SEL (Selector) unit 16, as shown in FIG. The numbers in parentheses of the respective parts 13, 14, 15, 16 indicate the number of bytes. In the AFI unit 13, “49” shown in hexadecimal notation represents a local format. The ESI unit 15 is written with a MAC address for identifying an ATM terminal (a terminal directly connected to the ATM exchange and having an ATM address). The SEL unit 16 is arbitrarily set by the ATM terminal. For example, the ATM address shown in FIG. 17 is given to an ATM terminal whose MAC address of the “B” sales office of the “A” branch is “MACE”.
[0028]
Here, the message relay in the backbone ATM network 10 is performed, for example, using only the upper 2 bytes of the NP unit 14 in the ATM address (in the example of FIG. 17, the 2-byte portion of “A” and “B”). Therefore, other parts (“C”, “D”, “MACE”, etc. in the example of FIG. 17) are ignored. That is, “a part for identifying the head office or branch” in the ATM address (“A” in the example of FIG. 17) and “a part for identifying the office (business office, etc.) in the head office or branch” (in the example of FIG. 17). Based on “B”), message relay is performed in the backbone ATM network 10.
[0029]
In the present embodiment, it is assumed that not only LER2 but also an ATM terminal may be connected to the subscriber ATM switch 3 (MPLS / ATM conversion function unit 1), and the subscriber ATM switch 3 (MPLS). / ATM conversion function unit 1) can easily determine whether to perform MPLS / ATM conversion processing for LER2 or normal ATM processing for an ATM terminal for the ATM address received from the backbone ATM switch 4. An MPLS conversion recognition code is defined. The MPLS / ATM conversion function unit 1 of the present embodiment has a function of writing an MPLS conversion recognition code to an ATM address converted from an IP address, and the subscriber ATM switch 3 receives from the backbone ATM switch 4. The ATM address is checked for the presence or absence of an MPLS conversion recognition code, and when the MPLS conversion recognition code is present, the ATM address is restored to an IP address according to an address conversion rule.
[0030]
FIG. 19 shows an example of the procedure for converting IP addresses to ATM addresses when assigning IP addresses and ATM addresses as described above. That is, the AFI part 13 of the ATM address sets a code (“49” in hexadecimal) indicating the local format (step 1). The NP unit 14 receives a destination IP address requested by LER2 (however, it may be a prefix of the IP address) and a prefix length PL (for example, “32” representing 32 bits in the case of an IPv4 IP address). Write (step 2). The remaining portions of the NP unit 14 other than the written data are all “0”. Then, an MPLS conversion recognition code (hereinafter referred to as an MPLS special number) is written in the ESI unit 15 which is ignored in message relay in the backbone ATM network 10 (step 3). For example, in the present embodiment, all ESI units 15 are set to “0” as MPLS special numbers. The SEL unit 16 is not used in the present embodiment, for example, and is all set to “0” (step 4).
[0031]
FIG. 4 shows an image in which an IP address “ABCD”, for example, is converted into an ATM address. As described above, the message relay in the backbone ATM network 10 is performed only in the upper 2 bytes of the NP portion 14 in the ATM address, and the other portions are ignored. Therefore, in the backbone ATM network 10, as shown in FIG. The converted ATM address is handled in the same manner as the ATM address shown in FIG. That is, the converted ATM address shown in FIG. 4 is an address that can reach the subscriber ATM switch 3 of the “B” sales office of the “A” branch.
[0032]
By the way, the case where the IP address prefix is written in the NP unit 14 is, for example, the following case. That is, the example of FIG. 4 shows a case where a line is set for the LAN terminal 5 whose IP address is “ABCD”, but in MPLS, a line may be set for the LAN. is there. That is, a line may be set for all the LAN terminals 5 belonging to a certain LAN. For example, when a line is set for the LAN “C” of the “B” sales office of the “A” branch, the NP unit 14 is as shown in FIG. 18, for example. That is, a part of the IP address (IP address prefix) indicating the LAN “C” of the “B” branch office of the “A” branch and the prefix length PL (in this case, “24” representing 24 bits, for example) are NP. Part 14 is written. As a result, a line is set in the LAN terminal 5 whose IP address is “ABC” (* is arbitrary). In the present specification, the “IP address” for which LER2 requests label setting includes a case where it is a prefix of such an IP address (that is, a part of the IP address).
[0033]
On the other hand, restoration processing from an ATM address to an IP address is performed, for example, according to the procedure shown in FIG. That is, first, the MPLS special number of the ESI unit 15 is detected, and it is recognized that it is necessary to convert from the ATM address to the IP address (step 5). Next, the prefix length PL is detected (step 6). Next, the IP address is restored based on the prefix length PL (step 7).
[0034]
Next, the mutual conversion function between the MPLS message and the ATM message that the MPLS / ATM conversion function unit 1 has will be described. The subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) converts the MPLS message received from the LER 2 into a corresponding ATM message with reference to, for example, the message conversion table 17 shown in FIG. To send to. On the other hand, the ATM message received from the backbone ATM switch 4 is converted into a corresponding MPLS message so that it can be transmitted toward the LER2. The message conversion table 17 is recorded in a storage device provided in the subscriber ATM switch 3, for example. A message that does not exist in the message conversion table 17 is ignored, for example, as “no conversion necessary”.
[0035]
The MPLS / ATM conversion function unit 1 of the present embodiment has a function of performing conversion or restoration of parameters included in the message in accordance with a predetermined parameter correspondence when converting or restoring an MPLS message or an ATM message. It is supposed to be. Table 1 shows an example of correspondence between MPLS and ATM services, and Table 2 shows examples of traffic parameters of each ATM service corresponding to MPLS traffic parameters.
[Table 1]

[Table 2]

In this embodiment, it is assumed that EBS (Excess Burst Size), Frequency, and Weight are not used in the ATM network among MPLS traffic parameters. In addition, when converting from an ATM message to an MPLS message, only the frequency of the DS is set to Frequent and the others are not used (EBS = 0, Frequency = Unspecified, Weight = 0).
[0036]
Next, the function of managing the correspondence between the MPLS line and the ATM line that the MPLS / ATM conversion function unit 1 has will be described. The MPLS / ATM conversion function unit 1 identifies which MPLS line and ATM line the message is associated with when an MPLS or ATM message is received by managing the correspondence between the MPLS line and the ATM line. For example, the MPLS / ATM conversion function unit 1 of this embodiment includes a management table 18, records necessary data in the management table 18, and manages the correspondence between the MPLS line and the ATM line (see FIG. 16). . The management table 18 is recorded, for example, in a storage device provided in the subscriber ATM exchange 3. A group of data corresponding to the row of the management table 18 is called a management record 19 in this embodiment.
[0037]
When the subscriber ATM switch 3 (MPLS / ATM conversion function unit 1) having the above-described functions receives various MPLS messages from the LER 2, or when various ATM messages are received from the backbone ATM switch 4. An example of the process is shown in the flowcharts of FIGS. 7 to 15 for each message type, and will be described below.
[0038]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives an MPLS message (Label Request) for a label request from the LER 2a, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. First, it is checked whether or not the MPLS message (Label Request) is valid (step 101). Whether the message is valid is to check whether the message violates a predetermined format, for example, whether there is an error such as whether a required parameter is included. If valid (step 101; Yes), the MPLS / ATM conversion function unit 1 converts the destination IP address into an ATM address (step 102). Then, necessary parameter conversion is performed (step 103). Then, it is confirmed whether or not the transfer destination backbone ATM switch 4 exists (step 104). If the transfer destination backbone ATM switch 4 exists (step 104; Yes), then it is confirmed whether or not resources can be secured, that is, whether or not the requested transmission quality can be provided (step 105). . If resources can be secured (step 105; Yes), the MPLS message (Label Request) of the label request is converted into an ATM message (SETUP) of the line setting request, and the ATM message (SETUP) is converted with the converted predetermined parameter, Transmission is performed toward the backbone ATM switch 4 (step 106). Then, the LSPID (Label Switched Path Identifier) and the destination IP address in the MPLS message (Label Request) received from the LER 2 are recorded in the management table 18. Further, in correspondence with this, the CR (Call Reference) of the ATM message (SETUP) transmitted to the backbone ATM switch 4 is recorded in the management table 18 (step 107). On the other hand, when the MPLS message (Label Request) is not valid (Step 101; No), when the transfer destination backbone ATM switch 4 does not exist (Step 104; No), or when resources cannot be secured (Step 105; No). Then, an MPLS message (Notification) is transmitted to notify LER2 of the error (step 108).
[0039]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives an ATM message (SETUP) for a line setting request from the backbone ATM exchange 4, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. First, it is checked whether the ATM message (SETUP) is valid (step 201). If it is valid (step 201; Yes), it is checked whether the ESI portion 15 of the destination ATM address is an MPLS special number (step 201). 202). If the ESI part 15 of the destination ATM address is an MPLS special number, it recognizes that it needs to be restored to the IP address (step 202; Yes), and performs conversion from the ATM address to the IP address (step 203). Then, necessary parameter conversion is performed (step 204). Then, it is confirmed whether or not the transfer destination LER2 exists (step 205). If the transfer destination LER2 exists (step 205; Yes), it is then checked whether resources can be secured, that is, whether the requested transmission quality can be provided (step 206). If resources can be secured (step 206; Yes), the ATM message (SETUP) of the line setting request is converted into an MPLS message (Label Request) of the label request, and the MPLS message is sent to LER2 together with the converted predetermined parameter. (Step 207). Then, the CR of the ATM message (SETUP) received from the backbone ATM switch 4, the LSPID and the destination IP address in the MPLS message (Label Request) transmitted to the LER 2 are recorded in association with the management table 18. On the other hand, when the ESI part 15 of the destination ATM address is not the MPLS special number (step 202; No), normal ATM processing is performed on the ATM terminal having the ATM address (step 209). If the ATM message (SETUP) is not valid (step 201; No), or if the transfer destination LER2 does not exist (step 205; No), or if resources cannot be secured (step 206; No), the backbone ATM switch A line release ATM message (RELEASE) is transmitted to 4 (step 210).
[0040]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives an MPLS message (Label Mapping) for label notification from the LER 2, it executes, for example, the processing shown in the flowchart of FIG. That is, it is checked whether the MPLS message (Label Mapping) is valid (step 301). If it is valid (step 301; Yes), it is checked whether there is a corresponding setting-waiting ATM line (step 302). That is, the corresponding management record 19 is searched from the management table 18 using the LSPID and destination IP address in the MPLS message (Label Mapping) received from LER 2 as a key, and the combination of the corresponding MPLS line and ATM line is grasped. If the corresponding ATM line exists (step 302; Yes), VPI / VCI (Virtual Path Identifier / Virtual Channel Identifier) is determined (step 303), and the MPLS message (Label Mapping) for label notification is completed. The ATM message (CONNECT) is converted and transmitted to the backbone ATM switch 4 (step 304). Then, the MPLS label in the MPLS message (Label Mapping) received from LER 2 and the VPI / VCI of the ATM message (CONNECT) transmitted to the backbone ATM switch 4 are stored in the corresponding management record 19 on the management table 18. Add and record. Therefore, the LSPID, the destination IP address, the label, the CR, and the VPI / VCI are associated as the management record 19 and managed on the management table 18 (step 305). On the other hand, when the MPLS message (Label Mapping) is not valid (step 301; No), or when there is no corresponding setting-waiting ATM line (step 302; No), an MPLS message (Notification) is sent to notify the LER2 of an error. ) Is transmitted (step 306).
[0041]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives an ATM message (CONNECT) indicating completion of line setting from the backbone ATM exchange 4, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. That is, it is checked whether or not the ATM message (CONNECT) is valid (step 401). If it is valid (step 401; Yes), it is checked whether there is a corresponding setting-waiting MPLS line (step 402). In the MPLS / ATM conversion function unit 1, for example, the corresponding management record 19 is searched from the management table 18 using the CR of the ATM message (CONNECT) received from the backbone ATM switch 4 as a key, and the combination of the corresponding MPLS line and ATM line is determined. To grasp. Then, if there is a corresponding MPLS line waiting for setting (step 402; Yes), a label for MPLS is determined (step 403), and an ATM message (CONNECT) indicating completion of line setting is sent as an MPLS message (Label Mapping) for label notification. ) And transmitted to LER2 (step 404). In the present embodiment, ATM cell VPI / VCI is used as the MPLS label. The management table 18 shows the VPI / VCI of the ATM message (CONNECT) received from the backbone ATM switch 4 and the MPLS label included in the MPLS message (Label Mapping) transmitted to the LER 2 and determined at the time of the transmission. Record in addition to the corresponding management record 19 above. Accordingly, the LSPID, the destination IP address, the label, the CR, and the VPI / VCI are associated with each other and managed on the management table 18 (step 405). On the other hand, if the ATM message (CONNECT) is not valid (step 401; No), or if there is no corresponding MPLS line waiting for setting (step 402; No), the ATM message (CONNECT) from the backbone ATM switch 4 is displayed. Is ignored (step 406).
[0042]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives a line release ATM message (RELEASE) from the backbone ATM exchange 4, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. That is, it is checked whether the ATM message (RELEASE) is valid (step 501). If it is valid (step 501; Yes), it is checked whether the corresponding MPLS line exists (step 502). The MPLS / ATM conversion function unit 1 searches for the corresponding management record 19 from the management table 18 using, for example, the CR of the ATM message (RELEASE) received from the backbone ATM switch 4 as a key, and grasps the corresponding MPLS line. If there is a corresponding MPLS line (step 502; Yes), the ATM message (RELEASE) received from the backbone ATM switch 4 is sent to the subscriber ATM switch 3 (MPLS / ATM conversion function unit 1) first. It is confirmed whether or not it is a response to the ATM message (SETUP) of the line setting request transmitted to (step 503). If it is the response (step 503; Yes), it is determined that the line setting requested by the subscriber ATM switch 3 (MPLS / ATM conversion function unit 1) has not been completed, for example, due to insufficient bandwidth, etc. A notification MPLS message (Notification) is transmitted to the terminal (step 504). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID and destination IP address and the ATM CR is terminated (step 505).
[0043]
On the other hand, when the ATM message (RELEASE) is not a response to the ATM message (SETUP) of the line setup request previously transmitted by the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) (step 503; No) Next, it is confirmed whether or not the ATM message (RELEASE) corresponds to the ATM message (SETUP) of the line setting request previously received by the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) (step) 507). If it corresponds to the ATM message (SETUP) (step 507; Yes), the line setting previously requested for the subscriber ATM switch 3 (MPLS / ATM conversion function unit 1) is some reason on the request side. In step 508, it is determined whether the request has been sent to LER 2 for the ATM message (SETUP) (step 508). If an MPLS message (Label Request) has already been transmitted to LER2 (step 508; Yes), an MPLS message (Label Release) for label release is transmitted to LER2 (step 509). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address and label and ATM CR and VPI / VCI is terminated (step 505). On the other hand, if an MPLS message (Label Request) has not yet been transmitted to LER2 (step 508; No), the corresponding management record 19 is deleted from the management table 18, and the MPLS LSPID, destination IP address, and label are deleted. And the correspondence management between the ATM CR and VPI / VCI are terminated (step 505).
[0044]
Further, the ATM message (RELEASE) received from the backbone ATM switch 4 is not a response to the ATM message (SETUP) previously transmitted by the subscriber ATM switch 3 (MPLS / ATM conversion function unit 1) (step 503; No. In addition, when it does not correspond to the previously received ATM message (SETUP) (step 507; No), it is a case where the release of the set line is requested. In this case, the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) confirms whether or not the LER 2 facing is the label requesting side (step 510), and if it is the label requesting side (step 510; Yes), An MPLS message (Label Withdraw) for canceling the label is transmitted (step 511). If it is not the label requesting side, that is, if the label is requested (step 510; No), a label release MPLS message (Label Release) is transmitted (step 509). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address and label and ATM CR and VPI / VCI is terminated (step 505). In addition, when the ATM message (RELEASE) is not valid (step 501; No), or when there is no corresponding MPLS line waiting for setting (step 502; No), the ATM message (RELEASE) is ignored ( Step 506).
[0045]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives an MPLS message (Label Release) for label release from the LER 2, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. That is, it is checked whether or not the MPLS message (Label Release) is valid (step 601). If it is valid (step 601; Yes), then the MPLS message is transferred to the MPLS message (Label Withdraw) for canceling the label already transmitted to the LER2 by the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1). It is determined whether or not the response is (step 602). If it is not the said response (step 602; No), it will be investigated whether the corresponding ATM line exists (step 603). That is, the MPLS / ATM conversion function unit 1 searches the management table 19 from the management table 18 using the LSPID or destination IP address in the MPLS message (Label Release) received from the LER 2 as a key, and grasps the corresponding ATM line. To do. If there is a corresponding ATM line (step 603; Yes), the label release MPLS message (Label Release) is converted into a line release ATM message (RELEASE) and transmitted to the backbone ATM switch 4 (step). 604). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address and label and ATM CR and VPI / VCI is terminated (step 605). On the other hand, when the MPLS message (Label Release) for releasing the label is not valid (Step 601; No), or when the MPLS message (Label Release) is a response to the transmitted MPLS message (Label Withdraw) (Step 602). Yes), or if the corresponding ATM line does not exist (step 603; No), the MPLS message (Label Release) is ignored (step 606).
[0046]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives an MPLS message (Label Abort Request) for canceling the label request from the LER 2, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. That is, it is checked whether or not the MPLS message (Label Abort Request) is valid (step 701). If valid (step 701; Yes), whether or not the MPLS message (Label Mapping) of the label notification corresponding to the MPLS message (Label Abort Request) has already been responded with the MPLS message (Label Mapping) of the label notification. Alternatively, for example, the contents of the management record 19 of the management table 18 are confirmed (step 702). If no response has been made yet (step 702; No), a line release ATM message (RELEASE) is transmitted to the backbone ATM switch 4 (step 703). Then, a notification MPLS message (Notification) is transmitted to LER2 (step 704). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID and destination IP address and the ATM CR is terminated (step 705). On the other hand, when the MPLS message (Label Abort Request) for canceling the label request is not valid (step 701; No), or when the MPLS message (Label Mapping) for label notification is already responding (step 702; Yes), The MPLS message (Label Abort Request) is ignored (step 706).
[0047]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives an MPLS message (Label Withdraw) for canceling a label from the LER 2, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. That is, it is checked whether or not the MPLS message (Label Withdraw) is valid (step 801). If it is valid (step 801; Yes), it is checked whether a corresponding ATM line exists (step 802). In other words, the MPLS / ATM conversion function unit 1 searches the management table 19 from the management table 18 using the LSPID and destination IP address in the MPLS message (Label Withdraw) received from the LER 2 as a key, and grasps the corresponding ATM line. To do. If there is a corresponding ATM line (step 802; Yes), an ATM message (RELEASE) is transmitted to the backbone ATM switch 4 (step 803). Then, an MPLS message (Label Release) is transmitted to LER2 (step 804). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address, and label and ATM CR and VPI / VCI is terminated (step 805). On the other hand, if the MPLS message (Label Withdraw) for canceling the label is not valid (step 801; No), or if the corresponding ATM line does not exist (step 802; No), the MPLS message (Label Abort Request) is ignored. (Step 806).
[0048]
When the subscriber ATM exchange 3 (MPLS / ATM conversion function unit 1) receives the notification MPLS message (Notification) from the LER 2, the subscriber ATM exchange 3 executes, for example, the processing shown in the flowchart of FIG. That is, it is checked whether or not the MPLS message (Notification) is valid (step 901). If it is valid (step 901; Yes), it is checked whether or not the MPLS message (Notification) is a message relating to a specific MPLS line, and whether or not a corresponding ATM line exists, for example, a management record in the management table 18 The contents of 19 are examined (step 902). For example, if the content of the MPLS message (Notification) is a message related to a specific MPLS line caused by LSP (Label Switched Path) setting failure or the like and a corresponding ATM line exists (step 902; Yes), the backbone ATM A line release ATM message (RELEASE) is transmitted to the exchange 4 (step 903). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address and label and ATM CR and VPI / VCI is terminated (step 904). On the other hand, if the MPLS message (Notification) is not a message relating to a specific MPLS line and there is no corresponding ATM line (step 902; No), it is confirmed whether or not the message is a message notifying a serious system failure (step 902). 905). If it is a message notifying a serious system failure (step 905; Yes), a line release ATM message (RELEASE) for all ATM lines is transmitted to the backbone ATM switch 4 (step 906). Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address and label and ATM CR and VPI / VCI is terminated (step 904). In addition, when the MPLS message (Notification) is not valid (step 901; No), or when the MPLS message (Notification) is not a message relating to a specific MPLS line but a message notifying a serious system failure (step) 905; No), the MPLS message (Notification) is ignored (step 907).
[0049]
Next, an example of setting a logical communication path capable of providing quality assurance of the communication system configured as described above (FIG. 1), an example of setting a logical communication path capable of providing quality assurance (FIG. 2), An example (FIG. 3) of releasing a logical communication path that can provide quality assurance will be described. It should be noted that only main messages and operations according to the present invention are described, and unspecified parts (for example, communication between the LAN terminal 5 and the LER 2) are based on known communication techniques and methods.
[0050]
First, an example of setting a logical communication path capable of providing quality assurance will be described with reference to FIG. FIG. 1 shows the setting of logical communication paths that can provide quality assurance from LER 2a to LER 2b in order to transmit IP traffic from LAN terminal 5a at branch A 11 of the private network to LAN terminal 5b at branch B 12. It shows the case of doing. Therefore, in this example, the A branch 11 side is the transmitting side, and the B branch 12 side is the receiving side.
[0051]
Here, it is assumed that the IP address of the transmitting LAN terminal is “aa.1.1”, for example. Further, the IP address of the transmission side LER 2a is, for example, “aa 1.0”. On the other hand, the IP address of the receiving LAN terminal is set to “bb.2.2”, for example. In addition, the IP address of the receiving side LER2b is assumed to be “bb 2.0”, for example.
[0052]
The LER 2a transmits an MPLS message (Label Request) of a label request to the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) in order to make a label request for the IP address “bb.2.2”. An arrow 7a in FIG. 1 shows an image of the message transmission. The parameters of the MPLS message in this case are, for example, LSPID = L1, destination IP address = b. b. 2.2 Required quality = (PDR = W, PBS = B, CDR = W, CBS = B, EBS = 0, Frequency = Frequent).
[0053]
When the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) receives the MPLS message (Label Request) of the label request from the LER 2a, it executes the processing shown in the flowchart of FIG. That is, it is checked whether the MPLS message (Label Request) is valid (step 101). If it is valid (step 101; Yes), the MPLS / ATM conversion function unit 1 converts the destination IP address into an ATM address. (Step 102).
[0054]
Then, necessary parameter conversion is performed (step 103). In the MPLS / ATM conversion function unit 1, for example, PDR = CDR, PBS = CBS, etc. in the parameters in the MPLS message, it is determined that the service requested in MPLS is DS and handled as CBR in the ATM network. , Parameters are converted to PCR = W ′ and CDVT = B ′. Here, W ′ and B ′ are obtained by converting the units of W and B (byte / sec) used in MPLS into units (cell / sec) used in ATM, respectively.
[0055]
Then, it is confirmed whether or not the transfer destination backbone ATM switch 4a exists (step 104). Since the transfer destination backbone ATM switch 4a exists (step 104; Yes), it is next checked whether resources can be secured, that is, whether the requested transmission quality can be provided (step 105). . If resources can be secured (step 105; Yes), the MPLS message (Label Request) of the label request is converted into an ATM message (SETUP) of the line setting request, and the ATM message (SETUP) is converted with the converted predetermined parameter, Transmission is performed toward the backbone ATM switch 4a (step 106). An arrow 7b in FIG. 1 shows an image of the transmission. The parameters of the ATM message in this case are: destination ATM address = Z (AFI = 49, NP = bb2.2.32.0.0.0.0.0.0.0, ESI = 0.0.0.0.0.0, SEL = 0), CR = R1, Required quality = CBR (PCR = W ′, CDVT = B ′).
[0056]
Then, LSPID (= L1) in the MPLS message (Label Request) (see reference numeral 20 in FIG. 16), destination IP address (= bb.2.2) (see reference numeral 21 in FIG. 16), ATM message CR (= R1) in (SETUP) (see reference numeral 22 in FIG. 16) is recorded in the management table 18a and managed in association with it (step 107).
[0057]
When the backbone ATM exchange 4a receives an ATM message (SETUP) from the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1), the backbone ATM exchange 4a relays the message. In the backbone ATM switch 4a, the transfer destination is determined to be the backbone ATM switch 4b from 2 bytes of the NP portion 14 of the destination ATM address, that is, “bb”. Then, an ATM message (SETUP) is transmitted to the backbone ATM switch 4b. An arrow 7c in FIG. 1 shows an image of the transmission. The ATM message parameters in this case are ATM address = Z (AFI = 49, NP = bb2.2.32.0.0.0.0.0.0.0, ESI = 0.0.0.0.0.0, SEL = 0), CR = R2, request Quality = CBR (PCR = W ′, CDVT = B ′). The CR is individually managed by each ATM switch, and it is not necessary for the subscriber ATM switch 3a (MPLS / ATM conversion function unit 1) and the backbone ATM switch 4a to match.
[0058]
When the backbone ATM exchange 4b receives an ATM message (SETUP) from the backbone ATM exchange 4a, the backbone ATM exchange 4b relays the message. In the backbone ATM exchange 4b, the transfer to the subscriber ATM exchange 3b is determined from 2 bytes of the NP portion 14 of the destination ATM address, that is, “b.b”. Then, an ATM message (SETUP) is transmitted to the subscriber ATM exchange 3b. An arrow 7d in FIG. 1 shows an image of the transmission. The ATM message parameters in this case are ATM address = Z (AFI = 49, NP = bb2.2.32.0.0.0.0.0.0.0, ESI = 0.0.0.0.0.0, SEL = 0), CR = R3, request Quality = CBR (PCR = W ′, CDVT = B ′).
[0059]
When the subscriber ATM exchange 3b (MPLS / ATM conversion function unit 1) receives the ATM message (SETUP) of the line setting request from the backbone ATM exchange 4b, the subscriber ATM exchange 3b executes the process shown in the flowchart of FIG. That is, it is checked whether the ATM message (SETUP) is valid (step 201). If it is valid (step 201; Yes), it is checked whether the ESI portion 15 of the destination ATM address is an MPLS special number (step 201). 202). Since the ESI unit 15 of the destination ATM address is an MPLS special number, the MPLS / ATM conversion function unit 1 recognizes that it needs to be converted to an IP address (step 202; Yes), and converts the ATM address to the IP address. (Step 203). That is, the destination IP address “bb.2.2” is obtained from the NP portion 14 of the ATM address.
[0060]
Then, necessary parameter conversion is performed (step 204). That is, the reverse conversion is performed to the parameter conversion performed in the MPLS / ATM conversion function unit 1 of the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) on the transmission side. As a result, the required quality is recognized as “PDR = W, PBS = B, CDR = W, CBS = B, EBS = 0, Frequency = Frequent”.
[0061]
Then, it is confirmed whether or not the transfer destination LER2b exists (step 205). Since the transfer destination LER2b exists (step 205; Yes), it is then checked whether resources can be secured, that is, whether the requested transmission quality can be provided (step 206). If resources can be secured (step 206; Yes), the ATM message (SETUP) of the line setting request is converted into an MPLS message (Label Request) of the label request, and the MPLS message is sent to the LER 2b together with the converted predetermined parameter. (Step 207). An arrow 7e in FIG. 1 shows an image of the transmission. The parameters of the MPLS message in this case are: LSPID = L2, destination IP address = b. b. 2.2, required quality = (PDR = W, PBS = B, CDR = W, CBS = B, EBS = 0, Frequency = Frequent).
[0062]
Then, CR (= R3) in the ATM message (SETUP) (reference numeral 23 in FIG. 16), LSPID (= L2) in the MPLS message (Label Request) (reference numeral 24 in FIG. 16), destination IP address (= b.b.2.2) (reference numeral 25 in FIG. 16) is recorded in the management table 18b and managed in association with the management table 18b (step 208). The LSPID may be uniquely set by the subscriber ATM exchange 3b. Therefore, the LSPID (= L2) recorded and managed in the management table 18b does not need to match the LSPID (= L1) included in the MPLS message (Label Request) issued by the LER 2a.
[0063]
When the LER 2b receives an MPLS message (Label Request) for a label request from the subscriber ATM exchange 3b (MPLS / ATM conversion function unit 1), the LER 2b determines an MPLS label. In the present embodiment, ATM cell VPI / VCI is used as a label. Then, an MPLS message (Label Mapping) for label notification is transmitted to the subscriber ATM exchange 3b (MPLS / ATM conversion function unit 1). An arrow 7f in FIG. 1 shows an image of the transmission. The parameters of the MPLS message in this case are: LSPID = L2, destination IP address = b. b. 2.2, for example, label (VPI / VCI) = P1 / C1.
[0064]
When the subscriber ATM exchange 3b (MPLS / ATM conversion function unit 1) receives the MPLS message (Label Mapping) of the label notification from the LER 2b, the subscriber ATM exchange 3b executes the process shown in the flowchart of FIG. That is, it is checked whether the MPLS message (Label Mapping) is valid (step 301). If it is valid (step 301; Yes), it is checked whether there is a corresponding setting-waiting ATM line (step 302). That is, in the MPLS / ATM conversion function unit 1, the LSPID (= L2) or the destination IP address (= bb.2.2) in the MPLS message (Label Mapping) received from the LER 2 b is used as a key from the management table 18 b. The management record 19 to be searched is searched and the corresponding ATM line (CR = R3) is grasped (step 302; Yes). Then, the VPI / VCI is determined (step 303), and the MPLS message (Label Mapping) for label notification is converted into an ATM message (CONNECT) for completion of line setting and transmitted to the backbone ATM switch 4b (step 304). An arrow 7g in FIG. 1 shows an image of the transmission. In this case, the parameters of the ATM message are CR = R3 and VPI / VCI = P2 / C2.
[0065]
Then, the MPLS label (= P1 / C1) in the MPLS message (Label Mapping) received from the LER 2b (= P1 / C1) is sent to the predetermined management record 19 of the management table 18b, and sent to the backbone ATM switch 4b. The VPI / VCI (= P2 / C2) of the ATM message (CONNECT) and (reference numeral 27 in FIG. 16) are recorded. Thereby, MPLS LSPID (= L2), destination IP address (= bb.2.2), label (= P1 / C1), ATM CR (= R3), VPI / VCI (= P2 / C2) are managed in association with each other on the management table 18b (step 305).
[0066]
When the backbone ATM switch 4b receives an ATM message (CONNECT) indicating completion of line setting from the subscriber ATM switch 3b, the backbone ATM switch 4b transmits the message to the backbone ATM switch 4a to relay the message. An arrow 7h in FIG. 1 shows an image of the transmission. In this case, the parameter of the ATM message is CR = R2, for example, VPI / VCI = P3 / C3.
[0067]
When the backbone ATM switch 4a receives an ATM message (CONNECT) indicating completion of line setting from the backbone ATM switch 4b, the backbone ATM switch 4a transmits the message to the subscriber ATM switch 3a (MPLS / ATM conversion function unit 1) to relay the message. In FIG. 1, an arrow 7i indicates an image of the transmission. In this case, the parameter of the ATM message is CR = R1, for example, VPI / VCI = P4 / C4.
[0068]
When the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) receives the ATM message (CONNECT) indicating the completion of line setting from the backbone ATM exchange 4a, the subscriber ATM exchange 3a executes the process shown in the flowchart of FIG. That is, it is checked whether or not the ATM message (CONNECT) is valid (step 401). If it is valid (step 401; Yes), it is checked whether there is a corresponding setting-waiting MPLS line (step 402). In the MPLS / ATM conversion function unit 1, for example, the corresponding management record 19 is searched from the management table 18 using the CR (= R1) of the ATM message (CONNECT) received from the backbone ATM switch 4a as a key, and the corresponding MPLS line is grasped. (Step 402; Yes). Then, an MPLS label is determined (step 403), the line setting complete ATM message (CONNECT) is converted into a label notification MPLS message (Label Mapping) and transmitted to the LER 2a (step 404). An arrow 7j in FIG. 1 shows an image of the transmission. The parameters of the MPLS message in this case are: LSPID = L1, destination IP address = b. b. 2.2, for example, label (VPI / VCI) = P5 / C5.
[0069]
Then, in the predetermined management record 19 of the management table 18a, the VPI / VCI (= P4 / C4) of the ATM message (CONNECT) received from the backbone ATM switch 4a (reference numeral 28 in FIG. 16), and the MPLS message transmitted to the LER 2a ( The MPLS label (= P5 / C5) in (Label Mapping) and (reference numeral 29 in FIG. 16) are recorded. Thus, MPLS LSPID (= L1), destination IP address (= bb.2.2), label (= P5 / C5), ATM CR (= R1), and VPI / VCI (= P4 / C4) are managed in association with each other on the management table 18a (step 405).
[0070]
By label notification to LER 2a, a label is set for the destination IP address (= bb.2.2), and a logical communication path capable of providing quality assurance is set between LER 2a and LER 2b. LER2a, LER2b realizes a quality requirement function of MPLS using labels, and actual quality assurance is performed by subscriber ATM switch 3a (MPLS / ATM conversion function unit 1), backbone ATM switch 4a, backbone ATM switch 4b, This is realized by an ATM line set by the subscriber ATM exchange 3b.
[0071]
Next, an example in which a logical communication path that can provide quality assurance cannot be set will be described with reference to FIG. FIG. 2 shows that the LAN terminal 5a of the A branch 11 of the private communication network tries to set a logical communication path capable of providing quality assurance from the LER 2a to the LER 2b so as to transmit IP traffic to the LAN terminal 5b of the B branch 12. However, the figure shows a case where the bandwidth is insufficient between the backbone ATM switch 4a and the backbone ATM switch 4b and cannot be set.
[0072]
The processing in which the LER 2a transmits an MPLS message (Label Request) for a label request to the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) (arrow 8a in FIG. 2 indicates an image of the transmission) is shown in FIG. This is the same as the example shown.
[0073]
Further, the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) transmits an ATM message (SETUP) of a line setting request to the backbone ATM exchange 4a together with a predetermined parameter (an arrow 8b in FIG. 2 indicates The image of the transmission is the same as the example shown in FIG.
[0074]
When the backbone ATM switch 4a receives the ATM message (SETUP) from the subscriber ATM switch 3a (MPLS / ATM conversion function unit 1), the backbone ATM starts from 2 bytes of the NP portion 14 of the destination ATM address, that is, “bb”. It decides to transfer to the exchange 4b and tries to relay the message. However, the backbone ATM switch 4a does not transmit an ATM message (SETUP) because it recognizes a lack of bandwidth for the requested transmission quality. An arrow 8c in FIG. 2 shows an image of the transmission stop.
[0075]
Then, the backbone ATM switch 4a transmits a line release ATM message (RELEASE) to the subscriber ATM switch 3a (MPLS / ATM conversion function unit 1). An arrow 8d in FIG. 2 shows an image of the transmission. In this case, the parameters of the ATM message are CR = R1, and the situation = band shortage.
[0076]
When the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) receives a line release ATM message (RELEASE) from the backbone ATM exchange 4a, the subscriber ATM exchange 3a executes the process shown in the flowchart of FIG. That is, it is checked whether the ATM message (RELEASE) is valid (step 501). If it is valid (step 501; Yes), it is checked whether the corresponding MPLS line exists (step 502). The MPLS / ATM conversion function unit 1 searches the corresponding management record 19 from the management table 18 using, for example, the CR (= R1) of the ATM message (RELEASE) received from the backbone ATM switch 4a as a key, and grasps the corresponding MPLS line. (Step 502; Yes). Next, it is confirmed whether or not the ATM message (RELEASE) received from the backbone ATM switch 4a is a response to the ATM message (SETUP) previously transmitted by the subscriber ATM switch 3a (MPLS / ATM conversion function unit 1) ( Step 503). Since the ATM message (RELEASE) is a response to the ATM message (SETUP) previously transmitted by the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) (step 503; Yes), it is notified to the LER 2a. The MPLS message (Notification) is transmitted (step 504). An arrow 8e in FIG. 2 shows an image of the transmission. The parameters of the MPLS message in this case are LSPID = L1 and reason = insufficient bandwidth. Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID and destination IP address and the ATM CR is terminated (step 505).
[0077]
Next, an example of releasing a logical communication path capable of providing quality assurance will be described with reference to FIG. FIG. 3 shows a case where the logical communication path capable of providing quality assurance set in FIG. 1 is released from the LER 2a.
[0078]
The LER 2a transmits a label release MPLS message (Label Release) to the subscriber ATM switch 3a (MPLS / ATM conversion function unit 1) in order to release the label for the IP address “bb.2.2”. An arrow 9a in FIG. 3 shows an image of the message transmission. The parameters of the MPLS message in this case are, for example, LSPID = L1, destination IP address = b. b. 2.2.
[0079]
When the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) receives an MPLS message (Label Release) for label release from the LER 2a, it executes the process shown in the flowchart of FIG. That is, it is checked whether the MPLS message (Label Release) is valid (step 601). If valid (step 601; Yes), then the MPLS message is a response to the MPLS message (Label Withdraw) that has already been transmitted from the subscriber ATM exchange 3a (MPLS / ATM conversion function unit 1) to the LER 2a. It is determined whether or not there is (step 602). Since it is not the said response (step 602; No), it is investigated whether the corresponding ATM line exists (step 603). That is, in the MPLS / ATM conversion function unit 1, the LSPID (= L1) and the destination IP address (= bb.2.2) in the MPLS message (Label Release) received from the LER 2a are used as keys from the management table 18. The management record 19 to be searched is retrieved, and the corresponding ATM line (CR = R1) is grasped (step 603; Yes). Then, the MPLS message (Label Release) for label release is converted into an ATM message (RELEASE) for line release and transmitted to the backbone ATM switch 4a (step 604). An arrow 9b in FIG. 3 shows an image of the transmission. In this case, the parameter of the ATM message is CR = R1. Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address and label and ATM CR and VPI / VCI is terminated (step 605).
[0080]
When the backbone ATM switch 4a receives a line release ATM message (RELEASE) from the subscriber ATM switch 3a (MPLS / ATM conversion function unit 1), it transmits the message to the backbone ATM switch 4b to relay the message. An arrow 9c in FIG. 3 shows an image of the transmission. In this case, the parameter of the ATM message is CR = R2.
[0081]
When the backbone ATM switch 4b receives a line release ATM message (RELEASE) from the backbone ATM switch 4a, the backbone ATM switch 4b transmits the message to the subscriber ATM switch 3b to relay the message. An arrow 9d in FIG. 3 shows an image of the transmission. In this case, the parameter of the ATM message is CR = R3.
[0082]
When the subscriber ATM switch 3b (MPLS / ATM conversion function unit 1) receives a line release ATM message (RELEASE) from the backbone ATM switch 4b, the subscriber ATM switch 3b executes the process shown in the flowchart of FIG. That is, it is checked whether the ATM message (RELEASE) is valid (step 501). If it is valid (step 501; Yes), it is checked whether the corresponding MPLS line exists (step 502). That is, the MPLS / ATM conversion function unit 1 retrieves the corresponding management record 19 from the management table 18 using the CR (= R3) of the ATM message (RELEASE) received from the backbone ATM switch 4b as a key, and sets the corresponding MPLS line. Grasp (step 502; Yes). The subscriber ATM switch 3b (MPLS / ATM conversion function unit 1) is requested to release the set line from the backbone ATM switch 4a (Step 503; No, Step 507; No), and the subscriber ATM switch Since the LER 2b facing the 3b (MPLS / ATM conversion function unit 1) is not the label request side but the side from which the label is requested (step 510; No), the label release MPLS message (Label Release) is sent to the LER 2b. Transmit (step 509). An arrow 9e in FIG. 3 shows an image of the transmission. The parameters of the MPLS message in this case are: LSPID = L2, destination IP address = b. b. Let 2.2. Then, the corresponding management record 19 is deleted from the management table 18, and the correspondence management between the corresponding MPLS LSPID, destination IP address and label and ATM CR and VPI / VCI is terminated (step 505).
[0083]
As described above, according to the communication system and the communication method of the present invention, the MPLS / ATM conversion function unit 1 that can be easily realized is installed in the subscriber ATM switch 3 and the LER 2 and the subscriber ATM switch 3 are connected. Thus, the quality requirement function of MPLS can be realized by LER2, and actual quality assurance can be performed by the ATM network. As is apparent from the above description, there is no need to make any changes to the backbone ATM network 10. Further, it is possible to introduce the MPLS quality function only by connecting the LER 2 to the subscriber ATM exchange 3 in which the MPLS / ATM conversion function unit 1 is mounted without newly constructing an MPLS domain. Therefore, it is possible to easily provide quality assurance for IP traffic using an existing ATM network.
[0084]
Further, in the present invention, the IP address and the ATM address are both adapted to the organizational hierarchy, for example, so that the IP address and the ATM address have a clear relationship, so that the address conversion can be performed easily and at high speed.
[0085]
Also, by managing the correspondence between MPLS lines and ATM lines, even if other messages such as ATM line settings not possible are received, the target line can be recognized by CR or LSPID, and appropriate processing is possible It becomes.
[0086]
The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. Although it is a suitable example of the present invention for performing easy and high-speed address conversion, it is a system in which both the IP address and the ATM address are adapted to the organizational hierarchy and the IP address and the ATM address have a clear relationship. It is not necessarily limited to this example. For example, when all IP addresses and ATM addresses can be grasped in advance in a small-scale private communication network or the like, a conversion correspondence table or the like in which the correspondence between IP addresses and ATM addresses can be grasped by the MPLS / ATM conversion function unit 1 May be held, and address conversion may be performed based on the conversion correspondence table. In this case, the MPLS / ATM conversion function unit 1 is not necessarily limited to the one realized by causing the computer constituting the subscriber ATM exchange 3 to execute the MPLS / ATM conversion program. For example, the MPLS / ATM conversion function unit 1 may be realized as a gateway device that connects the subscriber ATM exchange 3 and the LER 2.
[0087]
【The invention's effect】
As is clear from the above description, according to the communication system according to claim 1, the communication method according to claim 5, and the MPLS / ATM conversion program according to claim 6, without changing the backbone ATM network, The quality requirement function possessed by MPLS is realized by a label edge router, and actual quality assurance can be performed by an ATM network. Therefore, for example, quality assurance can be easily provided to IP traffic using an existing ATM network. Also, by managing the correspondence relationship between the MPLS line and the ATM line, even when other messages such as ATM line setting impossible are received, the target line can be recognized and appropriate processing can be performed.
[0088]
Furthermore, according to the communication system of the second aspect, the IP address and the ATM address can be easily and quickly converted by giving a clear relationship between the IP address and the ATM address.
[0089]
Further, according to the communication system according to claim 3, when the ATM terminal is connected to the terminal ATM switch by checking the presence / absence of the MPLS conversion recognition code in the MPLS / ATM conversion function unit, the label edge router It is possible to easily determine whether or not to perform MPLS / ATM conversion processing for the above or normal ATM processing for an ATM terminal.
[0090]
Furthermore, according to the communication system of claim 4, since conversion of the MPLS message or ATM message or the restoration of the parameter included in the message is also performed, the IP traffic can be more flexible and sophisticated. Quality assurance can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a communication system according to the present invention, and shows an example of setting a logical communication path capable of providing quality assurance.
FIG. 2 is a schematic configuration diagram showing an embodiment of a communication system according to the present invention, showing an example in which a logical communication path that can provide quality assurance cannot be set.
FIG. 3 is a schematic configuration diagram showing an embodiment of a communication system according to the present invention, showing an example of releasing a logical communication path capable of providing quality assurance;
FIG. 4 is a conceptual diagram showing an example of conversion from an IP address to an ATM address.
FIG. 5 is a flowchart showing an example of processing for converting an ATM address to an IP address.
FIG. 6 is a conceptual diagram showing an example of a message conversion table representing the correspondence between an MPLS message and an ATM message.
FIG. 7 is a flowchart showing an example of processing in a case where a terminal ATM switch equipped with an MPLS / ATM conversion function unit receives an MPLS message for a label request from a label edge router.
FIG. 8 is a flowchart showing an example of processing in a case where a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives a line setting request ATM message from a backbone ATM switch.
FIG. 9 is a flowchart showing an example of processing when a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives an MPLS message for label notification from a label edge router;
FIG. 10 is a flowchart showing an example of processing when a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives a line setting completion ATM message from a backbone ATM switch.
FIG. 11 is a flowchart showing an example of processing in a case where a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives a line release ATM message from a backbone ATM switch.
FIG. 12 is a flowchart showing an example of processing in a case where a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives an MPLS message for label release from a label edge router.
FIG. 13 is a flowchart showing an example of processing when a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives an MPLS message for canceling a label request from a label edge router.
FIG. 14 is a flowchart showing an example of processing in a case where a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives an MPLS message for label cancellation from a label edge router.
FIG. 15 is a flowchart showing an example of processing in a case where a terminating ATM switch equipped with an MPLS / ATM conversion function unit receives a notification MPLS message from a label edge router;
FIG. 16 is a conceptual diagram illustrating an example of a management table for managing the correspondence between an MPLS line and an ATM line.
FIG. 17 is a conceptual diagram showing an example of an ATM address of an ATM terminal in the present invention.
FIG. 18 is a conceptual diagram showing an example of conversion from an IP address to an ATM address.
FIG. 19 is a conceptual diagram illustrating an example of processing for converting an IP address to an ATM address.
[Explanation of symbols]
1 MPLS / ATM conversion function
2 LER (label edge router)
3 Subscriber ATM switch (Terminal ATM switch)
4 Backbone ATM switch

Claims (6)

A backbone ATM switch constituting a backbone ATM network, a terminal ATM switch connected to the backbone ATM switch, a label edge router having a function of configuring an MPLS network, and the label edge router and the terminal ATM switch are connected to each other. An MPLS / ATM conversion function unit is provided to construct a private network, and the MPLS / ATM conversion function unit converts an IP address for which the label edge router requests label setting into an ATM address according to a predetermined address conversion rule. A function for restoring the ATM address received by the terminating ATM switch from the backbone ATM switch to an IP address according to the address conversion rule, and an MPLS message transmitted by the label edge router according to a predetermined message correspondence relationship. A function for converting to an M message, a function for restoring the ATM message received by the terminal ATM switch from the backbone ATM switch to an MPLS message according to the message correspondence, an IP address for requesting label setting by the label edge router, A communication system comprising a label set for the IP address and a function of managing a correspondence relationship between an MPLS line and an ATM line set for the label. The IP address and the ATM address are allocated in an organizational hierarchy, and the MPLS / ATM conversion function unit converts the IP address into the ATM address so as to include a part or all of the IP address. 2. The communication system according to claim 1, further comprising a function of converting into an ATM address. The MPLS / ATM conversion function unit has a function of writing an MPLS conversion recognition code to an ATM address converted from the IP address, and the MPLS conversion recognition for the ATM address received by the terminal ATM switch from the backbone ATM switch. 3. The communication system according to claim 1, further comprising a function of examining the presence / absence of a code for use and restoring the ATM address to an IP address in accordance with the address conversion rule if the MPLS conversion recognition code is present. The MPLS / ATM conversion function unit has a function of performing conversion or restoration of parameters included in the message in accordance with a predetermined parameter correspondence when converting or restoring the MPLS message or the ATM message. The communication system according to any one of claims 1 to 3. A backbone ATM switch constituting a backbone ATM network, a terminal ATM switch connected to the backbone ATM switch, a label edge router having a function of configuring an MPLS network, and the label edge router and the terminal ATM switch are connected to each other. An MPLS / ATM conversion function unit is provided to construct a private network, and the MPLS / ATM conversion function unit converts the IP address for which the label edge router requests label setting into an ATM address according to a predetermined address conversion rule. The terminal ATM switch restores the ATM address received from the backbone ATM switch to an IP address according to the address conversion rule, and the MPLS message transmitted from the label edge router is converted to an ATM message according to a predetermined message correspondence. The terminal ATM switch restores the ATM message received from the backbone ATM switch into an MPLS message according to the message correspondence relationship, and the label edge router sets the IP address for requesting label setting and the IP address. And a correspondence relationship between an MPLS line and an ATM line set for the label. In a private communication network, in order to connect a terminal ATM switch connected to a backbone ATM switch and a label edge router having a function of configuring an MPLS network, the label edge router is connected to a computer provided in the terminal ATM switch. A function of converting an IP address requesting label setting into an ATM address according to a predetermined address conversion rule, and a function of restoring the ATM address received from the backbone ATM switch by the terminal ATM switch into an IP address according to the address conversion rule; A function of converting an MPLS message transmitted from the label edge router into an ATM message according to a predetermined message correspondence relationship, and an ATM message received by the terminal ATM switch from the backbone ATM switch. Correspondence between the function for restoring to an MPLS message according to the correspondence, the IP address for which the label edge router requests label setting, the label set for the IP address, and the MPLS line and ATM line set for the label MPLS / ATM conversion program for realizing the function of managing

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