JP4820343B2 - IP routing stabilization method, program thereof, and border router - Google Patents

Description

  The present invention relates to a routing technique in an IP (Internet Protocol) network having an optical network as a core network.

  In a network with an optical network as the core network, the configuration of switching can be remotely changed to this optical network, such as ROADM (Reconfigurable OADM, Reconfigurable Optical Add / Drop Multiplexer) and OXC (Optical Cross Connect). New transmission equipment is being introduced. Along with this, VNT (Virtual Network Topology) that provides an optimal optical path in this optical network and efficiently operates the optical network according to traffic exchange of the IP network, which is the upper layer, has been studied. (See Non-Patent Document 1).

  However, if the optical path is frequently changed (reconfigured) in such a VNT, it appears that the neighboring routers (IP network neighbors) of the IP network always change, and the route of the route is frequently recalculated in the routers of the IP network. Will be implemented. Thus, if route recalculation is frequently performed, routing instability of the IP network is caused.

Conventionally, (1) a technique for passing a routing protocol packet of an IP network through a GMPLS (Generalized Multi Protocol Label Switcing) control plane, or (2) a PSC-LSP (Packet defined in GMPLS) to solve such problems. There has been proposed a technique of using (Switch Capable-Label Switched Path) as a virtual tunnel (see Non-Patent Documents 2 and 3).
Shimazaki et al., “Traffic Driven VNT Reconfiguration Technology”, Proceedings of Society Conference of IEICE, B-12-14, March 2006 Kojima et al., “Examination of routing methods in multi-layer service networks”, IEICE Technical Report PN2004-38, August 2004 E. Mannie, “Generalized Multi-Protocol Label Switching (GMPLS) Architecture”, RFC3845, October 2004, IETF, [online], [Search June 15, 2007], Internet, <URL: http: // www. ietf.org/rfc/rfc3945.txt>

  However, the technology proposed for the above problem is based on the premise that GMPLS is used, and it is necessary that a transmission device such as ROADM or OXC or a router can use GMPLS. However, at the initial stage of introduction of ROADM and OXC, it is assumed that there are few devices that can use GMPLS, and it is considered difficult to immediately apply the techniques (1) and (2) described above.

  Therefore, an object of the present invention is to ensure the stability of IP routing when an optical path is changed without introducing GMPLS in an optical network in which the optical path can be changed.

In order to solve the above-described problem, the invention according to claim 1 is an optical network in which IP (Internet Protocol) networks are connected by an optical path, and the IP network is changed when the optical path established in the optical network is changed. An IP routing stabilization method for stabilizing IP routing between the optical network and the IP network, received from the IP network with reference to route information in a routing table stored in a storage unit A border router that forwards the packet using an optical path established with another border router in the optical network establishes a physical network neighbor with the border router connected by the optical path; The connection relationship with the border router that has established the physical network neighbor is recorded as the routing information of the physical layer in the routing table and stored in its border router. An IP network neighbor is established with an IP router of the IP network to be continued, an IP tunnel is established with each of the other border routers of the optical network using the optical path, and the established IP tunnel is established. An IP network neighbor is established with each of the other border routers that terminate the network using the IP tunnel, and the connection relationship with the border router that has established the IP network neighbor is determined in the IP layer of the routing table. The route information is recorded as route information, the route information in the IP layer is advertised to the IP router of the IP network that has established the IP network neighbor, the route information of the physical layer is sent to the other border router, and the IP tunnel is routed. It was set as the IP routing stabilization method characterized by using and advertising .

The invention according to claim 6 is an optical network that connects IP networks to each other, connects the optical network and the IP network, refers to route information in a routing table, and receives packets received from the IP network. A border router that transfers using an optical path established with another border router in the optical network, the storage section storing the routing table; and a border router connected by the established optical path; A physical network instance unit that records a connection relationship with the border router that has established the physical network neighbor as route information of the physical layer of the routing table, and is connected to its own border router An IP network neighbor is established with an IP router of the IP network, and the other boundary of the optical network is established using the established optical path. Establishing an IP tunnel with a router, establishing an IP network neighbor with the other border router that is the termination of the established IP tunnel, using the IP tunnel, and establishing the IP network neighbor The connection relationship between the IP router and the border router is recorded as route information in the IP layer of the routing table, and the route information in the IP layer of the route information in the routing table is established as the IP network neighbor. An IP network instance that advertises to the IP router, advertises the physical layer route information to the other border router using the IP tunnel, and receives a packet addressed to the other IP network from the IP network The IP table addressed to the other IP network by referring to the routing information in the IP layer of the routing table. To the received packet, an IP encapsulated packet with an IP header addressed to the address of the border router that is the end of the selected IP tunnel is generated, and the generated IP encapsulated packet is An IP tunnel processing unit configured to refer to route information in a physical layer of the routing table and transfer to a border router serving as a physical network neighbor in a route to a border router serving as a termination of the IP tunnel. A border router to be used.

  By doing so, the path information exchanged between the IP router and the border router of the IP network indicates the connection relationship (adjacent relationship) of the border router in the IP layer, and the physical network ( The connection relationship of the (physical layer) is not included. Therefore, even when the optical path in the optical network is changed, the topology viewed from the IP network does not change. As a result, it is possible to efficiently operate the optical network by reconfiguring the optical path without considering the influence on the IP network by reconfiguring the optical path. In addition, since the present invention does not presuppose the introduction of GMPLS, it is not necessary to change the ROADM, OXC, router, etc., which are transmission devices in the optical network. A physical network neighbor is a neighbor in a routing protocol used for a border router of a physical network (here, an optical network), and an IP network neighbor is a neighbor in a routing protocol used for an IP network.

  The invention according to claim 2 is the IP routing stabilization method according to claim 1, wherein when the border router receives a packet addressed to another IP network from the IP network, an IP layer of the routing table is provided. An IP tunnel destined for the other IP network is selected with reference to the route information in the IP, and an IP header with an IP header addressed to the address of the border router serving as the termination of the selected IP tunnel is added to the received packet Generating an encapsulated packet and referring to the generated IP encapsulated packet in the physical layer of the routing table in a path that reaches the border router that is the end of the IP tunnel; The IP routing stabilization method is characterized by forwarding to a border router.

  The invention according to claim 3 is the IP routing stabilization method according to claim 2, wherein when the border router receives the IP encapsulated packet from another border router, the route in the physical layer of the routing table The IP routing stabilization method is characterized in that, by referring to the information, a route reaching the border router indicated in the IP header of the IP encapsulated packet is transferred to the border router serving as the physical network neighbor.

  Thus, the packet transmitted from the IP network is transferred to the border router connected to the destination IP network of the packet using the IP tunnel in the optical network. That is, when viewed from the external IP network, border routers that are not physically directly connected also appear to be adjacent.

  The IP routing stabilization method according to claim 4 is the IP routing stabilization method according to any one of claims 1 to 3, wherein the border router establishes the physical network neighbor. The IP routing stabilization method according to any one of claims 1 to 3, wherein OSPF (Open Shortest Path First) is used as a protocol.

  By doing in this way, this invention is realizable, without adding a change to the routing protocol of the existing router. Thereby, the setting (change) cost of the router for applying the present invention can be reduced.

  According to a fifth aspect of the present invention, there is provided a program that causes the border router to execute the IP routing stabilization method according to any one of the first to fourth aspects.

  According to such a program, it is possible to cause a general router to execute the IP routing stabilization method according to any one of claims 1 to 4.

  According to the present invention, in an optical network in which an optical path can be reconfigured, stability of IP routing at the time of optical path reconfiguration can be ensured without introducing GMPLS.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings. In the border router according to the present embodiment, the routing protocol used in the physical network instance unit is described as an example of OSPF, but is not limited thereto. For example, IS-IS (Intermediate System to Intermediate System), RIP (Routing Information Protocol), or the like may be used as a routing protocol.

  FIG. 1 is a diagram illustrating a configuration example of a network according to the present embodiment.

  The network shown in FIG. 1 includes an optical network 1 and a plurality of IP networks 2 (2A, 2B, 2C) that use the optical network 1 as a core network.

  The optical network 1 includes a plurality of OXCs 3 and border routers 4 (4A, 4B, 4C). The optical network 1 is connected to an external IP network 2 through the border router 4. In the following description, it is assumed that the IP address of the border router 4A is “A”, the IP address of the border router 4B is “B”, and the IP address of the border router 4C is “C”.

  In addition, an optical path 6 such as a wavelength is established between the border routers 4 in the optical network 1, and a physical network neighbor is established between the two border routers 4 connected by the optical path 6. The The border router 4 in the optical network 1 is connected to any other border router 4 by an optical path 6. That is, each border router 4 is connected by the optical path 6 so as not to be isolated. An IP tunnel 7 is established in the optical path 6. The IP tunnel 7 is a virtual path obtained by encapsulating an IP packet with a new IP header. This IP tunnel 7 is established with all the border routers 4 in a full mesh. Note that an IP tunnel 7 via the boundary router 4A is established between the boundary routers 4 not directly connected by the optical path 6, for example, between the boundary router 4B and the boundary router 4C in FIG.

  Each of the IP networks 2 outside the optical network 1 includes one or more IP routers 5. Here, a case will be described as an example where the destination network 8 connected to the IP router 5B exists in the IP network 2B. The IP address of the destination network 8 is “100.1.1.0/24”.

<Border router>
Next, the configuration of the border router 4 in FIG. 1 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the border router 4 of FIG.

  The border router 4 includes a physical network instance unit 101, an IP network instance unit 102, an IP tunnel processing unit 103, and a storage unit 100. The border router 4 is realized by a router that can connect the optical network 1 and the IP network 2 to each other.

<Physical network instance part>
The physical network instance unit 101 performs an OSPF protocol process. Specifically, a physical network OSPF neighbor (physical network neighbor) 107 is established with another border router 4 in the optical network 1, and the topology of the physical network in the optical network 1 is grasped through this neighbor. That is, the topology of the physical network in the optical network 1 is grasped by exchanging the path information of the physical network (path information indicating the physical adjacency state) between the boundary routers 4 that have established the physical network OSPF neighbor 107. . Since the physical network OSPF neighbor 107 is directly established on the optical path 6 (see FIG. 1) (that is, not through the IP tunnel 7), the physical network OSPF neighbor 107 is connected between the border routers 4 connected by the direct optical path 6. Only the physical network OSPF neighbor 107 exists. However, since the border router 4 is connected by the optical path 6 so as not to be isolated, the topology of the physical network of all the border routers 4 can be grasped.

  The physical network instance unit 101 does not establish a neighbor with the IP router 5 of the external IP network 2. Thereby, even if the optical path 6 in the optical network 1 is changed, it is possible to prevent the external IP network 2 from knowing it. When the physical network instance unit 101 grasps the topology of the physical network of the optical network 1, the physical adjacency relationship between the border routers 4 (the border router 4 serving as the next hop) is used as the routing information of the physical layer of the routing table 104. Record. Here, the physical adjacency relationship between the border routers 4 (the border router 4 serving as the next hop) is referred to when the border router 4 transfers a packet within the optical network 1.

<IP network instance part>
The IP network instance unit 102 performs processing of a routing protocol used in the IP network 2. Specifically, the IP router 5 of the IP network 2 and a routing protocol neighbor (IP network neighbor 108) used in the IP network 2 are established. In addition, an IP tunnel 7 is established with another border router 4 in the optical network 1 and an IP network neighbor 108 is established. The IP network neighbor 108 with the other border router 4 is established through the IP tunnel 7 after being IP-encapsulated by an IP tunnel processing unit 103 described later. The routing protocol operated by the IP network instance unit 102 is not particularly limited. For example, any protocol provided in a general router such as OSPF, BGP (Border Gateway Protocol), IS-IS, or the like can be used. Further, the IP network instance unit 102 records the connection relationship with the established IP network neighbor 108 as route information of the IP layer in the routing table 104. The IP network instance unit 102 advertises the IP layer route information to the IP router 5 and the border router 4 that have established the IP network neighbor.

<IP tunnel processing section>
The IP tunnel processing unit 103 performs IP packet encapsulation and decapsulation processing. Encapsulation here refers to the transfer of IP packets transferred from the IP network 2 to the optical network 1 with a new IP header for realizing the IP tunnel 7 being transferred. The destination address of the header describes the IP address of the border router 4 that is the end of the IP tunnel 7. Decapsulation is to remove the IP header of a packet that has been IP-encapsulated and transferred from another border router 4 and transfer it to the external IP network 2 as the original IP packet. When viewed from the IP network 2 outside the optical network 1, the IP tunnel processing unit 103 appears to be adjacent to the border routers 4 that are not physically directly connected.

  The storage unit 100 stores various data referred to when performing route control of packets input from the outside of the optical network 1. The storage unit 100 stores a routing table 104 and a forwarding table 106. The storage unit includes a RAM (Random Access Memory), a HDD (Hard Disk Drive), a flash memory, and the like.

<Routing table>
The routing table 104 is a table referred to when the border router 4 performs packet route control. FIG. 3A is a diagram illustrating the routing table 104 (104A) of the border router 4A in FIG. 1, and FIG. 3B is a diagram illustrating the routing table 104 (104B) of the border router 4B in FIG. FIG.

  As illustrated in FIGS. 3A and 3B, the routing table 104 is a table indicating the next hop 202 of the IP packet, the output interface 203 of the IP packet, and the like for each destination IP address 201 of the IP packet. It is. In the output interface 203, in addition to the interface number of the network interface 105 that outputs the corresponding IP packet, when performing IP encapsulation, as shown in FIG. 3A, "IP encapsulation: B" or the like It is described. This means “IP encapsulate and send to B”.

  Note that the routing table 104 is generated based on the information obtained by the physical network instance unit 101 and the IP network instance unit 102 as described above, and becomes the basis of the forwarding table 106 described later.

  Specifically, when the physical network instance unit 101 grasps the physical adjacency relationship (physical network OSPF neighbor) of each boundary router 4 based on the topology information of the physical network, for example, the routing shown in FIG. The second row (destination IP address “B”, next hop “B”, output interface “# 1”) and third row (destination IP address “C”, next hop “C”, output interface “# 2” of the table 104A. )). That is, for each destination IP address of the border router 4 in the optical network 1, the physical network instance unit 101 describes information on the next hop when the packet is transferred to the border router 4. The physical network OSPF neighbor described above will be described. As described above, the physical network instance unit 101 records the connection relationship with the border router 4 that has established the physical network neighbor as the routing information of the physical layer of the routing table 104. Further, when the IP network instance unit 102 grasps the adjacency relationship (IP network neighbor) of each border router 4 viewed from the IP layer of each border router 4 based on the topology information of the IP network 2, based on this, for example, FIG. Information such as the first line (destination IP address “100.1.1.0/24”, next hop “B”, output interface “IP encapsulation: B”) of the routing table 104A shown in FIG. To do. That is, for each destination IP address of the destination network 8, the IP network instance unit 102 describes information such as an output interface to be the next hop for reaching the destination network 8. List network neighbors. That is, the IP network instance unit 102 establishes an IP network neighbor with the IP router 5 of the IP network 2 connected to its own border router 4 and records the IP network neighbor as route information of the IP layer.

<Network interface>
The network interface 105 is an interface for connecting the optical fiber line of the optical network 1 and the border router 4 and is used for input / output of packets and plays a role of actually transferring packets. When the network interface 105 receives an input of an external packet, the network interface 105 determines an output interface with reference to a forwarding table 106 described later. For example, when a packet is received from the IP network 2 side, the output interface is determined with reference to the forwarding table 106. Then, a packet is output into the optical network 1 using the determined output interface. Also, when a packet is received from the optical network 1 side, the output interface is determined with reference to the forwarding table 106 as well. Then, a packet is output to the IP network 2 using the determined output interface.

<Forwarding table>
The forwarding table 106 is a table that is referred to when the network interface 105 determines an output interface of a packet. 4A is a diagram illustrating the forwarding table 106 (106A) of the border router 4A in FIG. 1. FIG. 4B is a diagram illustrating the forwarding table 106 (106B) of the border router 4B in FIG. is there.

  As shown in FIGS. 4A and 4B, the forwarding table 106 includes, for each destination IP address 301 of the IP packet, an output interface 302 of this IP packet, IP encapsulation (information about IP encapsulation) 303, It is the table which showed. This IP encapsulation 303 indicates whether a packet having the address described in the destination IP address 301 as the destination IP address needs to be IP encapsulated and transferred. Here, when IP encapsulation is necessary, the destination address of the IP header newly added to this packet when IP encapsulation is performed is also described.

  For example, in the forwarding table 106 (106A) of FIG. 4A, a packet having a destination IP address “100.1.1.0/24” is assigned an IP capsule with the destination address “B” added to the IP header. And output from the output interface “# 1”. Here, the source address is also given to the IP header of the IP-encapsulated packet, but the source address is given the address of the own router (for example, IP address “A”).

  In FIG. 2, the forwarding table 106 is drawn separately from the one used by the network interface 105 on the IP network 2 side and the one used by the network interface 105 on the optical network 1 side. It may be summarized in the table 106.

  In addition, among the components described above, the physical network instance unit 101, the IP network instance unit 102, and the IP tunnel processing unit 103 may be realized in software or in hardware. In other words, the CPU (Central Processing Unit) of the border router 4 may be realized by reading and executing a program in the storage unit 100, or may be realized by the above-described physical network instance unit 101, IP network instance unit 102, IP You may implement | achieve using the dedicated circuit which implement | achieves the function of the tunnel process part 103. FIG.

<Operation procedure>
Next, the operation procedure of each component of the network in FIG. 1 will be described with reference to FIGS. First, it demonstrates using FIG.

  FIG. 5 is a sequence diagram showing a procedure from when the IP router 5B of FIG. 1 advertises the route information of the destination network 8 until the packet addressed to the destination network 8 arrives at the IP router 5B. Here, the optical path 6 as shown in FIG. 1 has already been established between the border routers 4A and 4B and between the border routers 4A and 4C. It is assumed that the adjacent relationship is recorded in the routing table 104. Further, it is assumed that an IP tunnel is established in these optical paths 6 by the IP network instance unit 102 of each border router 4. Further, although the description of the transmission source IP address is omitted in the packets in FIGS. 5 to 8, the transmission source IP address of this packet is actually given to each packet.

  The IP router 5B of the IP network 2B that accommodates the destination network 8 of FIG. 1 advertises the route information of the destination network 8 (IP address “100.1.1.0/24”) to the border router 4B by OSPF. (S1). Thereby, this route information is input to the IP network instance unit 102 (see FIG. 2) of the border router 4B, and the IP network instance unit 102 stores the routing table 104 based on the information described in this route information. Update (S2). The IP network instance unit 102 also updates the forwarding table 106.

  For example, the IP network instance unit 102, based on the advertised route information, information (destination IP address “100.1.1.0/24”) in the first row of the routing table 104B shown in FIG. , Next hop “B1”, output interface “# 2”). Further, the IP network instance unit 102, based on the information described in the first line of the routing table 104B, the information (destination IP address “100.1”) in the first line of the forwarding table 106B shown in FIG. 1.1.0 / 24 ", output interface" # 2 ", IP encapsulation"-(none) ").

  Returning to the description of FIG. Next, the border router 4B advertises the route information to the border routers 4A and 4C by the IP tunnel processing unit 103 in order to advertise this route information to the other border routers 4 (S3, S4). The OSPF route information (OSPF packet) advertised here is IP-encapsulated by the IP tunnel processing unit 103, and the destination IP address of each route information is “A” and “C”.

  Thereafter, when the border router 4A receives the OSPF packet advertised from the border router 4B, the IP tunnel processing unit 103 decapsulates the OSPF packet and inputs it to the IP network instance unit 102. Then, the IP network instance unit 102 updates the routing table 104 in the same manner as S2 described above (S5).

  For example, in S5, the IP network instance unit 102 describes the contents of the first line of the routing table 104A shown in FIG. 3A, but describes that IP encapsulation is performed in the column of the output interface 203 ( Output interface “IP encapsulation: B”). In order to transmit a packet from the border router 4A to the destination network 8, it is necessary to send out the OSPF packet that advertises the information of the destination network 8 in the receiving direction. And received through the IP tunnel. For this reason, the packet addressed to the destination network 8 must be transmitted through the IP tunnel. Thereafter, the border router 4A updates the forwarding table 106A as well as the routing table 104A.

  For example, from the contents of the first row of the routing table 104A in FIG. 3A, a packet having a destination IP address “100.1.1.0/24” is IP-encapsulated and then IP address “B”. I know that I should send it to. Here, the output interface for transmitting to the IP address “B” is “# 1” from the contents of the second row of the routing table 104A. Therefore, it is understood that the packet addressed to “100.1.1.0/24” should be output from the interface “# 1” after being IP-encapsulated. Therefore, the information shown in the first line (destination IP address “100.1.1.0/24”, output interface “# 1”, IP encapsulation “B”) is written in the forwarding table 106A of FIG. To do.

  Note that the information on the second and third lines of the routing table 104A shown in FIG. 3A is information obtained by the physical network instance unit 101 described above. Since this information is information that can be generated within the scope of the standard function of OSPF that operates in the physical network instance unit 101, description thereof is omitted here.

  Returning to the description of FIG. Thereafter, the border router 4A advertises the route information (OSPF packet) exchanged by the IP network instance unit 102 to the IP router 5 (for example, IP router 5A) of the IP network 2A (S6). That is, the IP network instance unit 102 of the border router 4A transmits the route information “destination IP address: 10.1.1.1.0 / 24, advertising router: 5B, source of the route information: A” of the IP network 2A. Advertisement is sent to the IP router 5 (5A) (not shown).

  As a result, the IP router 5A receives the route information “destination IP address: 10.1.1.2.0 / 24, advertisement IP router: 5B, source of the route information: A” (S7).

  At this time, the physical network instance unit 101 of the border router 4A has not established a neighbor with the IP router 5 (5A) of the IP network 2A. The information shown in the second and third lines of the routing table 104A shown in FIG. Thereby, even if there is a change in the optical path 6 in the optical network 1, it is possible to prevent the IP network 2A from being aware of this.

  The IP router 5A that has received the route information (OSPF packet) from the border router 4A in S7 of FIG. 5 refers to this route information to grasp the topology viewed from the IP layer. An IP packet assigned with the address “100.1.1.1.1” is transmitted. Then, the border router 4A receives this IP packet (S11).

  The border router 4A searches the forwarding table 106A (see FIG. 4A) using the destination IP address of the IP packet input to the network interface 105 as a key. Then, a new IP header with a destination IP address “B” is added to the packet, and the packet is IP-encapsulated and then transmitted from the output interface “# 1”. Next, the network interface 105 sends the received packet to the IP tunnel processing unit 103, and after adding IP headers of “destination IP address: B” and “source IP address: A” to this packet. The IP packet is transmitted from the network interface 105 corresponding to the output interface “# 1” (S12). That is, the border router 4 refers to the route information in the IP layer of the routing table 104, selects an IP tunnel, and sends the address of the border router 4 that is the end of the selected IP tunnel to the packet received in S11. An IP encapsulated packet with the IP header added is generated. Then, the generated IP encapsulated packet is referred to the path information in the physical layer of the routing table 104, and is routed to the boundary router 4 serving as the physical network neighbor in the path reaching the boundary router 4 serving as the termination of the IP tunnel Forward.

  The border router 4B receives the IP packet transmitted from the border router 4A (S13). This IP packet is input to the network interface 105 of the border router 4B. The network interface 105 uses the destination IP address “100.1.1.1.1” as a key and the forwarding table 106B (see FIG. 4B). By searching, the border router 4B knows that this packet should be output from the output interface “# 2”. Since this IP packet is transferred to the outside of the optical network 1 (that is, the IP network 2), it is decapsulated by the IP tunnel processing unit 103 of the border router 4B. The decapsulated packet is transferred from the network interface 105 corresponding to the output interface “# 2” of the border router 4B to the IP router 5B (S14). Thereafter, this packet reaches the destination network 8 from the IP router 5B.

  Next, a processing procedure after the optical path 6 in the optical network 1 of FIG. 1 is changed will be described with reference to FIGS.

  FIG. 6 is a diagram illustrating the reconfiguration of the optical path 6 in the optical network 1 of FIG. FIG. 7 is a sequence diagram showing a procedure until a packet addressed to the destination network 8 reaches the IP router 5B via the reconfigured optical path 6 after the reconfiguration of the optical path 6 of FIG. 8A is a diagram showing the routing table 104A of the border router 4A before reconfiguration of the optical path 6 of FIG. 1, and FIG. 8B is a border router after reconfiguration of the optical path 6 of FIG. It is the figure which showed the routing table 104A of 4A.

  Here, in the optical network 1, a case where the configuration of the optical path 6 shown in FIG. 6A is changed to the configuration of the optical path 6 shown in FIG. 6B will be described as an example. That is, the case where the optical path 6 that connects the border router 4A and the border router 4B is disconnected and the optical path 6 that connects the border router 4C and the border router 4B is newly established will be described as an example.

  First, the border router 4 in FIG. 1 reconfigures the optical path 6 (S101). The reconfiguration of the optical path 6 may be performed by an operator manually instructing the boundary router 4 and the OXC 3 from an external management device or the like that manages the optical network 1, or some parameter may be set in the boundary router 4 itself. For example, the management apparatus or the like may be instructed to reconfigure the optical path 6 when the amount of traffic (for example, traffic between the border routers 4) exceeds a predetermined threshold.

  When the optical path 6 is reconfigured, the physical network instance neighbor 101 between the border routers 4A and 4B disconnects the physical network OSPF neighbor between the border routers 4A and 4B (S102). The physical network instance unit 101 of each of the border routers 4C and 4B establishes a physical network OSPF neighbor between the border routers 4C and 4B (S103).

  Accordingly, the border routers 4B, 4C, and 4A update the routing table 104 by the physical network instance unit 101 (S104, S105, and S106).

  For example, the physical network instance unit 101 of the border router 4A updates the routing table 104A from the state shown in FIG. 8A to the state shown in FIG. In other words, since the optical path 6 is directly established between the border router 4A and the border router 4B before the optical path 6 is reconfigured, the packet next reaches the border router 4B (IP address “B”). The hop was “B”. However, after the optical path 6 is reconfigured, in order to reach the border router 4B (IP address “B”), it must pass through the border router 4C (IP address “C”). “C”. However, the IP network instance unit 102 does not change information related to the destination IP address “100.1.1.0/24” (information on the first line in FIG. 3A). This is because the destination IP address “100.1.1.0/24” is route information obtained through the IP tunnel 7 and the connection form itself of the IP tunnel 7 does not change before and after the optical path 6 is reconfigured. is there. That is, the IP network neighbor relating to the destination IP address “100.1.1.0/24” does not change. Further, since the physical network instance unit 101 does not establish a neighbor with the IP router 5 of the external IP network 2, the path information is not updated for the external IP network 2. By doing so, it is possible to maintain the topology viewed from the external IP network 2 before and after reconfiguration of the optical path 6.

  Thereafter, for example, when the packet of the destination IP address “100.1.1.1.1” is input from the IP router 5A to the boundary router 4A (S111) as in FIG. 5 described above, the boundary router 4A is updated. With reference to the subsequent routing table 104A (see FIG. 8B), this packet is IP-encapsulated and transmitted to the border router 4B (S112). That is, the border router 4A transmits an IP packet after newly adding an IP header of “destination IP address: B” to the packet. However, as shown in the information in the second row of the updated routing table 104A shown in FIG. 8B, the next hop of the packet with the destination IP address “B” is “C” (boundary router 4C). The output interface to the border router 4C is “# 2”. That is, after the optical path 6 is reconfigured, the packet from the border router 4A to the border router 4B passes through the border router 4C, and therefore the border router 4A outputs the output interface “# 2” to the border router 4C. The packet is transmitted from the network interface 105 corresponding to "."

  The border router 4C receives the packet transmitted from the border router 4A in this way (S113), and confirms that the received packet is not addressed to itself. Transfer to the router 4B (S114). That is, the border router 4C refers to the route information in the physical layer of the routing table 104 and transfers the route to the border router 4B serving as the physical network neighbor in the route reaching the border router 4B indicated in the IP header of the IP encapsulated packet. To do. Here, the border router 4C refers to the outer IP header of the received packet, that is, the IP header having the destination IP address “B”, but the inner IP header (destination IP address “100.1.1.1”). .1 ") is not referenced.

  Thereafter, when the border router 4B receives the packet from the border router 4C (S115), the border router 4B knows that the packet is addressed to itself (addressed to the border router 4B). The IP header is removed and decapsulation is performed, and the decapsulated packet is transferred to the IP router 5B which is the next hop of the destination IP address “100.1.1.1” (S116). Thereafter, this packet reaches the destination network 8 from the IP router 5B.

  Thus, since packets are transferred between the border routers 4 through the IP tunnel, when viewed from the external IP network 2, the border routers 4 are always connected with one hop without depending on the topology of the optical path 6. Looks like. That is, even when the optical path 6 is reconfigured, the IP router neighbor is the same in the border router 4, so that the IP router 5 on the IP network 2 side can be made unaware of the reconfiguration of the optical path 6.

  The border router 4 according to the present embodiment can be realized by a program that executes the processing as described above, and can provide the program as a computer-readable storage medium (CD-ROM or the like). is there. It is also possible to provide the program through a network.

It is the figure which showed the structural example of the network of this Embodiment. It is the block diagram which showed the structure of the border router 4 of FIG. (A) is the figure which illustrated the routing table 104 (104A) of the border router 4A of FIG. 1, (b) is the figure which illustrated the routing table 104 (104B) of the border router 4B of FIG. (A) is the figure which illustrated the forwarding table 106 (106A) of the border router 4A of FIG. 1, (b) is the figure which illustrated the forwarding table 106 (106B) of the border router 4B of FIG. FIG. 3 is a sequence diagram showing a procedure from when the IP router 5B of FIG. 1 advertises route information of the destination network 8 until a packet addressed to the destination network 8 arrives at the IP router 5B. It is the figure which illustrated reconfiguration | reconstruction of the optical path 6 in the optical network 1 of FIG. FIG. 2 is a sequence diagram showing a procedure until a packet addressed to a destination network 8 reaches the IP router 5B via the reconfigured optical path 6 after the optical path 6 in FIG. 1 is reconfigured. (A) is a diagram showing a routing table 104A of the border router 4A before reconfiguration of the optical path 6 of FIG. 1, and (b) is a diagram of the border router 4A after reconfiguration of the optical path 6 of FIG. It is the figure which showed the routing table 104A.

Explanation of symbols

1 Optical network 2 (2A, 2B, 2C) IP network 3 OXC
4 (4A, 4B, 4C) Border router 5 (5A, 5B) IP router 6 Optical path 7 IP tunnel 8 Destination network 101 Physical network instance unit 102 IP network instance unit 103 IP tunnel processing unit 104 (104A, 104B) Routing table 105 Network interface 106 (106A, 106B) Forwarding table 107 Physical network OSPF neighbor 108 IP network neighbor

Claims (6)

An IP routing stabilization method for stabilizing IP routing between IP networks when an optical path established in the optical network is changed in an optical network in which IP (Internet Protocol) networks are connected by an optical path,
A packet received from the IP network is established with another border router of the optical network by connecting the optical network and the IP network and referring to route information in a routing table stored in a storage unit. Border router that forwards using the optical path
Establishing a physical network neighbor with the border router connected by the optical path, and recording the connection relationship with the border router that established the physical network neighbor as the routing information of the physical layer of the routing table,
Establishing an IP network neighbor with the IP router of the IP network connected to its border router;
Establishing an IP tunnel with each of the other border routers of the optical network using the optical path;
Establishing IP network neighbors with each of the other border routers that terminate the established IP tunnel using the IP tunnel,
The connection relationship with the border router that has established the IP network neighbor is recorded as route information in the IP layer of the routing table,
Advertising the route information in the IP layer to the IP router of the IP network that established the IP network neighbor ;
An IP routing stabilization method, wherein the physical layer route information is advertised to the other border router using the IP tunnel . The border router is
When a packet addressed to another IP network is received from the IP network,
With reference to route information in the IP layer of the routing table, an IP tunnel addressed to the other IP network is selected,
Generating an IP-encapsulated packet in which an IP header is added to the received packet, the destination being the address of the border router that is the end of the selected IP tunnel;
The generated IP encapsulated packet is transferred to the boundary router serving as the physical network neighbor in the route reaching the boundary router serving as the termination of the IP tunnel with reference to the route information in the physical layer of the routing table. The IP routing stabilization method according to claim 1, wherein: The border router is
When the IP encapsulated packet is received from another border router,
The route information reaching the border router indicated by the IP header of the IP encapsulated packet is referred to the route information in the physical layer of the routing table, and transferred to the border router serving as the physical network neighbor. Item 3. The IP routing stabilization method according to Item 2.   The IP routing stability according to any one of claims 1 to 3, wherein the border router uses OSPF (Open Shortest Path First) as a routing protocol when establishing the physical network neighbor. Method.   The program which makes the said border router perform the IP routing stabilization method of any one of Claim 1 thru | or 4. In an optical network for connecting IP networks to each other, the optical network and the IP network are connected, the routing information in the routing table is referred to, and a packet received from the IP network is sent to another border router in the optical network. A border router that forwards using an optical path established between
A storage unit for storing the routing table;
A physical network that establishes a physical network neighbor with a border router connected by the established optical path, and records a connection relationship with the border router that has established the physical network neighbor as route information of a physical layer of the routing table An instance part;
An IP network neighbor is established with an IP router of an IP network connected to its own border router, an IP tunnel is established with another border router of the optical network using the established optical path, Establishing an IP network neighbor using the IP tunnel with another border router that terminates the established IP tunnel, and establishing a connection relationship between the IP router that established the IP network neighbor and the border router. , recorded as the route information in the IP layer of the routing table, the out of the path information in the routing table, the routing information in the IP layer, and advertised to the IP router which has established the IP network neighbor, the path of the physical layer An IP network instance unit that advertises information to the other border routers using the IP tunnel ;
When a packet addressed to another IP network is received from the IP network, an IP tunnel addressed to the other IP network is selected by referring to route information in the IP layer of the routing table. Generate an IP encapsulated packet with an IP header attached to the address of the border router that is the end of the selected IP tunnel, and refer to the generated IP encapsulated packet in the routing table in the physical layer of the routing table And an IP tunnel processing unit configured to transfer to the border router serving as the physical network neighbor in a route to the border router serving as the termination of the IP tunnel.

Images