JP2590211B2 - Network congestion control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a packet switching network for transferring packets via a transit exchange, which temporarily stops the inflow of packets to a transit exchange in a congested state. And a network congestion control method.

[Conventional technology]

In a packet switching network, means for suppressing input of a packet to a transit exchange when the transit exchange is congested is required. In the conventional packet switching network, the packet transfer method in the network adopts the datagram method, and the relay path is not fixed during the data transfer phase. For this reason, the originating exchange that has received a packet from the terminal cannot determine which transit exchange the packet passes through, and temporarily stops only packets that pass through a specific transit path at the entrance of the exchange. Did not have.

[Problems to be solved by the invention]

For this reason, when a transit exchange is congested, in order to prevent a packet from flowing into the transit exchange, a method has been adopted in which an adjacent exchange detours a transit packet to another transit exchange. Has the drawback of being congested. Also, when the transit exchange is congested, it transmits a congestion notification packet to the adjacent exchange to execute the above-described detour of the relay packet, and when the congestion is released, transmits a congestion release notification packet to detour the relay packet. Although the method of stopping is used, there is a disadvantage that the state management becomes complicated, such as using a response packet of the congestion release notification in preparation for loss of the congestion release notification packet.

SUMMARY OF THE INVENTION An object of the present invention is to provide a network congestion control method that can easily prevent the spread of congestion to a device other than the congestion switch when the relay switch is congested.

[Means for solving the problem]

In order to achieve the above object, in the present invention, communication for each logical channel between terminals, during a data transfer phase,
In a packet-switched network that uses fixed transit routes, if the transmission queue of the forward communication channel in the transit exchange on the transit route becomes larger than the specified value, "forward congestion"
Is displayed when the transmission queue of the communicating channel in the opposite direction to the channel is larger than a specified value.The display of "reverse congestion" is displayed when both the transmission queues of both channels are larger than the specified value. The indication of "two-way congestion" is set and relayed to the packet passing through the channel, and when the destination exchange receives a packet with the indication of forward congestion, the originating exchange of the packet is notified of the reverse congestion. When a packet for which indication is set is returned and a packet for which indication of reverse congestion is set is received, input from a terminal using the corresponding relay path is temporarily stopped.

[Action]

When congestion is detected by the relay exchange on the relay path and the congestion identification information is sent to the originating exchange and the destination exchange, the relay path between the originating and destination exchanges is fixed for communication for each logical channel between terminals. It is possible to identify a communication call using the relay path. Therefore, the originating and terminating exchange accommodating the terminal can temporarily stop the communication call of the corresponding logical channel and the input packet from the logical channel using the same relay path as the communication call, Also, this temporarily stops the input to the congestion relay exchange.

〔Example〕

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. In the figure, 1, 2 are terminals, 3, 5 are outgoing or incoming packet switches, 4 is a transit exchange on the transit path between packet switches 3 and 5, 6 and 7 are subscriber lines, and 8 and 9 are transit lines. , 10 and 11 are control packet generation determining mechanisms for identifying whether or not there is a piggybackable packet for returning congestion information, and 12 and 13 are transmission queues for transmission to a transmission line, When the data is transmitted from the exchange 3 to the exchange 5, if the length of the queue 12 exceeds a predetermined value, a forward congestion indication (see FIG. 51 described later) of the congestion identification information of the packet is set. If the length of the queue 13 exceeds a predetermined value, a reverse congestion indication (see FIG. 52 described later) of the congestion identification information of the packet is set.

FIG. 2 is an explanatory diagram showing an example of a packet switching network for implementing the present invention. In the figure, 21 to 23 are terminals, 24 to 28
Is a packet switch, 29 to 31 are subscriber lines, 32 to 39 are trunk lines, and 40 and 41 are examples of relay paths between switches 24 and 28, and are fixed without being changed during the data transfer phase. .

FIG. 3 is an explanatory diagram showing an example of a format of a packet used in the present invention. In the figure, reference numeral 50 denotes a field for setting the congestion identification information, 51 denotes a subfield for displaying the congestion of the forward relay path in which the own packet is transferred, and 52 denotes the transfer of the own packet. This is a subfield for displaying the congestion of the relay path in the direction opposite to the direction in which it is performed.

 The operation will be described below with reference to these figures.

An example of the configuration of the packet switching network used in the present invention is as shown in FIG. In a normal packet switching network, for example, when a packet is transmitted from the switch 24 to the switch 28,
Packets are 24-26-28, 24-27-28, 24-26-25-27
-28, a method of selecting a relay path for each packet, that is, data is transferred within the network by a datagram method. On the other hand, in the present invention, the relay path for the communication call for each logical channel between the terminals is the same relay path during the data transfer phase, for example, only the relay path 40 passing through 24-26-28 is used. Is controlled not to use. This is because, in the virtual call system, the destination DT in the packet header is set at the time of call setup at each exchange on the relay path.
This can be realized by determining the outgoing line based on the E address information, tabulating the correspondence between the outgoing line number and the logical channel number and the like, and selecting the outgoing line based on the table in the data transfer phase. Alternatively, a plurality of relay routes, for example, 40 and 41, are set in advance between the exchanges, and a number of the relay route is assigned thereto, and in the call setting phase,
At the originating exchange and the destination exchange, the relay path number is selected based on the destination DTE address information in the packet header, and the correspondence between the relay path number and the logical channel number is tabulated, and the outgoing line is selected based on the table in the data transfer phase. It is also feasible. If the logical channel number and the like in the packet from the terminal are configured to be associated with a preset relay path number, it is also possible to realize the permanent virtual circuit method.

FIG. 1 is an explanatory view showing an embodiment of the present invention as already described, but corresponds to a part which is extracted from FIG. 2 and is necessary for understanding the present invention. Description will be made on the assumption that a packet is transferred from the terminal 1 to the terminal 2. When the exchange 4 receives the packet from the exchange 3, it extracts information necessary for routing such as a logical channel number from the header of the packet, and selects an outgoing line from the table created by the above-described method based on the information. , The transmission queue 12 to which the packet is to be attached is determined.

Next, the queue length of the waiting queue 13 on the transmission side of the reverse line of the line receiving the packet and the transmission queue 12 to which the packet is attached are checked. Transmission queue 13
Is larger than the specified value, a congestion display is set in the subfield 52, and a display of reverse congestion is set. Further, if the transmission queue 12 exceeds the predetermined length, a congestion indication is set in the subfield 51 of the packet congestion identification information field 50 to indicate the forward congestion.
In this case, if both the transmission queues exceed the specified value, or if the entire transit exchange is considered to be congested as in buffer congestion, the subfields 51 and 5
Set the display for both of the two. When the setting of the congestion indication is completed, the packet is attached to the transmission waiting queue, and the incoming exchange 5
Transferred to

When the packet arrives, the terminating exchange 5 checks the congestion information identification field of the packet to determine the occurrence of congestion on the intermediate relay route. If congestion has occurred and a forward congestion indication is set in the subfield 51, it is necessary to return a control packet for controlling the input from the terminal 1 to the originating exchange 3. Therefore, the control packet generation determining mechanism 11 determines whether or not there is a packet that can be piggybacked toward the exchange 3 and, if there is a packet destined for the exchange 3, returns to the subfield 52 of the congestion identification information field of the packet. Set the direction congestion indication. If there is no packet destined for the exchange 3, a control packet is generated, a congestion indication in the reverse direction is set in the subfield 52 of the congestion identification information field of the packet, and the packet is transmitted to the exchange 3. When the exchange 3 receives the packet, it temporarily restricts the input to the terminal 1 accommodated in the exchange 3 that uses the corresponding logical channel of the terminal 1 and the corresponding relay path, thereby inputting the packet to the relay exchange 4. Deter.

Subfield 52 of the packet received by terminating exchange 5
If the display of the reverse congestion is set in, the relay path from the exchange 5 to the exchange 3 is congested, and therefore the exchange 5 uses the corresponding logical channel of the terminal 2 and the corresponding relay path. In this case, input control is temporarily performed on the terminal accommodating the exchange 5 to suppress the packet input to the relay exchange 4. As a result, the congestion of the transmission queue 13 in the relay exchange 4 gradually decreases, and the exchange 3 can be notified of the congestion from the exchange 5. In addition,
The same processing is performed for a packet for which the congestion display in both directions is set.

As described above, according to the present invention, the state of congestion is determined based on the congestion identification information set in the relay packet, and the packet is relayed to the exchange accommodating the terminal that is inputting the packet to the congested relay exchange. It is possible to notify the congestion of the route and regulate the communication using the route for a certain fixed time.

〔The invention's effect〕

As described above, when the transit exchange is congested,
It is possible to regulate the inflow of packets to the congested relay exchange without diverting the packets passing through the relay exchange to another relay exchange. The transit exchange does not need to notify other exchanges of the congestion release, and has an advantage that the state management is simple.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of a packet switching network embodying the present invention, and FIG.
The figure is an explanatory diagram showing a configuration example of a packet used in the present invention,
It is. Description of symbols 1,2… terminal, 3,5… packet exchange accommodating terminal,
4: a relay exchange having a relay function between the packet switches 3 and 5, 6, 7: subscriber line, 8, 9: trunk line, 10, 11: control packet generation judging mechanism, 12, 13: transmission line Queues for sending, 21-23… Terminals, 24-28… Packet switches, 29-31
... subscriber line, 32-39 trunk line, 40, 41 ... relay line set between exchanges 24 and 28, 50 ... field for setting congestion identification information, 51 ... own packet is transferred Display subfield when the direction of the route is congested,
52: Display subfield when the route opposite to the direction in which the own packet is transferred is congested

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Sakai 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-63-24742 (JP, A) JP-A Sho 62-85532 (JP, A) Computer Communication Review, Vol. 4 (Aug 1988), KK Ramakrishnan (1 other person), A Binary Feedback Scheme for Cong Estion Avoidance in Computer Network with a Communication Less Network

Claims (1)

(57) [Claims] In a packet switching network in which a relay path is fixed and used during a data transfer phase for communication between logical terminals between terminals, a transmission queue of a forward communication channel in a relay switch on the relay path is used. Is greater than the specified value "forward congestion"
Is displayed when the transmission queue of the communicating channel in the opposite direction to the channel is larger than a specified value.The display of "reverse congestion" is displayed when both the transmission queues of both channels are larger than the specified value. The indication of "bidirectional congestion" is set and relayed to the packet passing through the channel, and when the destination exchange receives a packet with the indication of forward congestion, the destination exchange of the packet is notified of the reverse congestion. A network congestion control method, comprising: returning a packet for which indication is set, and temporarily stopping input from a terminal using a corresponding relay path, when receiving a packet for which indication of reverse congestion is set.