JPH10285168A - Path change-over system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a path change-over system which returns a default route from a congested state by switching a packet transfer path that becomes a congestion factor to a short-cut path when a default route is congested in an MPOA network. SOLUTION: A congestion detecting part in each router 11 to 14 on a default route supervises the states of a transmitting buffer and a receiving buffer which are provided in each interface that is held by each router. As a result of supervision, when congestion is detected, a congestion notification message is transferred through an NHRT control path or an MPOA control path. An edge device 21 which receives the congestion notification message uses a target protocol address and switches to a short-cut path that is performed by an MPOA protocol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a path switching system, and more particularly to a path switching system in an ATM (Asynchronous Transfer Mode) network employing MPOA (Multi Protocol Over ATM).

[0002]

2. Description of the Related Art FIG. 9 shows a general configuration example of an MPOA network, and FIGS. 10 and 11 show the configurations of a router and an edge device according to the prior art. In FIG. 9, MPOA (Mu
lti Protocol Over ATM) is an IP (Inte
One technique for operating internetworking protocols, such as the Internet Protocol (rnet Protocol), is ATM.
Standardization is underway at the Forum. MPOA network is also LAN-Em standardized by ATMForum.
Emulation LANs (hereinafter referred to as E-LANs) 401 and 402 based on the existing LAN (Ethernet in this example).
et) are composed of edge devices 21 and 22 for transferring the above packets by E-LAN, and routers 11, 12, 13 and 14 connecting between the E-LANs.

An edge device 21 which is an edge node,
An MPOA Client (MPC) 201 that operates as a client of the MPOA protocol is mounted on 22, and an MPOA Server (MPS) 10 that operates as a server of the MPOA protocol on the routers 11, 12, 13, and 14.
1 is implemented. In the MPOA, the MP of the edge device 21 which is a packet input side with respect to the ATM network is
The C201 resolves the ATM address of the edge device 22, which is the output side of the packet, by the MPOA protocol, so that the ATM VC (Virtual Channel) is directly connected between the input side edge device 21 and the output side edge device 22.
Set 301 and transfer the packet. In addition, 501,5
02 and 503 are data paths between routers.

In FIG. 10, a router 11 includes an MPS 101 including a message processing unit 111 and an NHRP control path IF unit 1 that interfaces with an NHRP control path.
13 and the M which forms an interface with the MPOA control path
A POA control path IF unit 114, an E-LAN IF 104 serving as an interface with the E-LAN, an inter-router IF 103 serving as an interface with another router, and a destination I
A routing table 108 in which the IP address of the next transfer destination with respect to the P address, the host / router type, the interface number, the interface type, and the like are described;
And a routing processing unit that determines a transfer destination for the destination IP address of the data packet with reference to the routing table.

[0005] An E-LAN IF 104 is a transmission buffer unit 105 for temporarily storing packets to be transmitted to the E-LAN.
, A reception buffer unit 106 for temporarily storing packets received from the E-LAN, and an LEC (LAN Emulation Cl
ient) 107. LEC107
Is the MAC (Media Access Control) of the terminal on Ethernet.
l) LES (LAN Emulation Ser
ver). Thereby, signaling for performing the ATM communication is performed.

The inter-router IF 103 includes a transmission buffer unit 105 for temporarily storing a packet to be transmitted to the E-LAN.
And a reception buffer unit 106 for temporarily storing packets received from the E-LAN.

The other routers 12 to 14 have the same configuration as the router 11 described above.

In FIG. 11, an edge device 21 is
An MPC 201 having an output processing unit 207, an input processing unit 209, and a path switching control unit 213; an E-LAN IF 203 having an LEC 107; a shortcut IF 204 serving as an interface with a shortcut path;
It is configured to include an MPOA control path IF unit 205 serving as an interface with the MPOA control path, and a bridge unit 202 serving as an interface with Ethernet.

The output processing unit 207 in the MPC 201
It has an output cache 208 for temporarily storing packets to be output to the hernet. The input processing unit 209 in the MPC 201 has an input cache 210 for temporarily storing packets input from the Ethernet and a counter 211.

The other edge devices 22 have the same configuration as the above edge device 21.

Hereinafter, the operation will be described for the case where the routing protocol is IP. In FIG. 9, the host 31 connected to the edge device 21 via the Ethernet 801
Therefore, a case where an IP packet is transmitted to the host 32 similarly connected to the edge device 22 via the Ethernet 802 will be considered. The destination MAC address of the packet sent from the host 31 to the edge device 21 is the MAC address of the router 11, and the destination IP address is the IP address of the host 32.
Address. First packet is incoming edge node 2
At the stage where the packet is received at step 1, the MPC 31 does not know the ATM address of the outgoing edge device 22, so the packet is passed to the E-LAN IF 203 and transferred to the router 11 on the E-LAN 401 based on the destination MAC address.

The routing processing unit 102 in the router 11
Determines the transfer destination for the destination IP address of the data packet with reference to the routing table 108. The routing table 108 describes the IP address of the next transfer destination for the destination IP address, the type of host / router, the interface number, and the interface type (E-LAN or data path between routers). This information is dynamically set by a routing protocol exchanged between routers or fixedly set in advance.

By the transfer processing in the routers 11, 12, and 13, the packet is transferred to the router 11-data path 601-router 12-data path 602-router 13-data path 6.
03-Transferred by the route of the router 14.

The router 14 recognizes from the destination IP address of the packet that the next transfer destination is the host 32 and that the host 32 can be reached via the edge device 22 connected to the E-LAN 402. Then, the router 14 sends the packet having the destination MAC address as the MAC address of the host 32 by the E-LAN 402 to the edge device 2.
Transfer to 2. The edge device 22 transfers the packet to the host 32 based on the destination MAC address. Thus, for the initial packet, the edge node 21-
The data is transferred by the route 1 (default path) passing through the router 11-router 12-router 13-router 14-edge node 22.

In the input processing unit 209 in the MPC 201 of the edge device 21 which is an edge node, an Ethernet 80
The destination IP address of the packet received from 1 is monitored by the router 11 for the router MAC address,
The number of packets is counted by the counter 211 for each destination IP address. As a result of this counting, if the number of packets per unit time exceeds a preset threshold value, the router resolves the ATM address of the outgoing edge device 22 of the ATM network to reach the destination IP address. M for MPS 101 on
POA address resolution request (MPOA Resolution Req
uest).

The address resolution request is sent to the router 11 by the MPS
IETF (Internet Engeneering Task F
orce) standardized NHRP (Next Ho
p Resolution Protocol) Address Resolution Request (NHR)
P Resolution Request), and the router 1 on the E-LAN 402 to which the outgoing edge device 22 is connected.
4 is transferred to the MPS 101. M in router 14
The PS 101 transmits information (the ATM address of the edge device 21 and the MAC address of the router 14 and the MAC address of the router 32) necessary for the edge device 22 to transfer the packet received from the shortcut path to the host 32 by a cache setting request (MPOA Imposition Request). After being set in the output cache 208 of the edge device 22, the ATM address of the edge device 22 is set to the M of the router 11 by an address resolution response (NHRP Resolution Reply).
Responds to PS101. This response is the MPS of router 11.
At 101, the MPOA address resolution response (MPOA Reso
lution Reply), and the MP of the edge device 21
Transferred to C201.

Note that the address resolution request between MPC and MPS, the address resolution request between MPS and MPS, M
For the cache setting request between PS and MPC, E-
The data is transferred via MPOA control paths 701 and 702 or NHRP control paths 601, 602 and 603 which are set separately from the data path between the LAN and the router.

In the MPC 201 of the edge device 21,
When the ATM address of the edge device 22 addressed to the host 32 is resolved, a VC 301 is set between the edge device 21 and the edge device 22. VCI of this VC
(Virtual Channel Identifier) value is input cache 2
Recorded at 10. Thereafter, the destination MAC address in the packet received from the Ethernet 801 is the router 11,
For the packet whose address indicates the host 32, the input processing unit 209 of the edge device 21
10 and transfer to the VC 301 instead of the E-LAN 401.

In the edge device 22, for the packet received from the VC 301, the output processing unit 207 refers to the output cache 208, sets the destination MAC address in the host 32, and sets the source MAC address in the router 12 and sends it to the host 32. Forward. Thus, once the ATM address of the outgoing edge device 22 is resolved, the packet is transferred by route 2 (shortcut path) passing through the edge device 21-the edge device 22.

According to the above operation, the data flow between the specific hosts having a large traffic amount can be directly transferred by the shortcut path. It is possible to ensure the quality and reduce the load on the data transfer of the router on the default path.

[0021]

In this conventional path switching system, the trigger for path switching is that an edge device counter exceeds a threshold value. Usually IP
TCP (Transmission Control Protocol)
l) In the layer and application layer, window control is performed between hosts. If the path between hosts is congested and delay increases, the transmission of packets from the sending host is restricted depending on the window size, and the throughput decreases. I do. When a router on the default path is shared as a default route between multiple edge devices, if the path between routers is free,
Packet delay on the default route is small and required throughput is obtained. Therefore, if the threshold value is set to an appropriate value, switching to the shortcut path occurs because the counter value exceeds the threshold value.

On the other hand, when the path between the routers is congested, the packet transfer throughput by the default path cannot be obtained, and the counter of the edge node does not easily exceed the threshold value. Therefore, even if the same threshold value is set in the same application, there is a possibility that switching to the shortcut path does not occur.

As described above, in MPOA, when the default route is congested, switching to the shortcut path is less likely to occur. In particular, even if an attempt is made to use MPOA to reduce the transfer load on a router on the default route, the transfer load cannot be improved in situations where traffic from multiple edge nodes is concentrated on the default route. There is a disadvantage of doing so.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to transfer a packet that causes congestion when a default route is congested in an MPOA network. An object of the present invention is to provide a path switching system capable of returning a default route from a congested state by switching a route to a shortcut path.

[0025]

SUMMARY OF THE INVENTION A path switching system according to the present invention is a path switching system in a network having a default path and a shortcut path, and transferring a packet using these paths. And a path switching control unit that switches a packet transfer path from the default path to the shortcut path in response to detection of a congestion state.

Further, the path switching means includes a congestion detecting means for detecting congestion in accordance with a storage state of a buffer for temporarily storing a packet transferred by the default path;
Path switching means for switching a transfer path from the default path to the shortcut path in response to the congestion detection.

Further, the network includes an edge device that is a source and a destination of the packet, and a router that relays the packet. The congestion detecting unit is provided in the router, and the path switching unit is an edge device. And notifies the path switching means of the congestion detection by the congestion detection means.

The notification of congestion detection from the congestion detection means to the path switching means is performed using a control path or a data path.

In short, the present invention provides a function of detecting congestion to a router on a default route, a function of notifying congestion to an ingress edge device of a packet which has caused congestion when detecting congestion, The function of activating the switching operation to the shortcut path triggered by the reception of the congestion notification in the edge device is provided.

By doing so, even if congestion occurs in the router on the default route of the MPOA network,
Since the ingress edge device of the packet that caused the congestion is notified of the congestion, and the ingress edge device is switched to the shortcut path by the MPOA protocol,
The default route can be restored from the congestion state.

[0031]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a path switching system according to the present invention. In this figure, the same parts as those in FIG. 9 are denoted by the same reference numerals, and detailed description of those parts will be omitted.

Here, the internal configuration of the router in FIG.
Is shown in In FIG. 2, the same parts as those in FIG. 10 are denoted by the same reference numerals, and detailed description of those parts will be omitted.

FIG. 3 shows the internal configuration of the edge device in FIG. In FIG. 2, the same parts as those in FIG. 11 are denoted by the same reference numerals, and detailed description of those parts will be omitted.

First, referring to FIG. 2, the router is configured as shown in FIG.
And a congestion detection unit 109, a congestion notification generation unit 110, and a congestion notification transfer unit 112. The congestion detection unit 109 includes the transmission buffer 10
5. Detect the congestion state of the reception buffer 106. The congestion notification generation unit 110 generates a congestion notification message when the congestion detection unit 109 detects congestion. Upon receiving the congestion notification from the congestion notification generation unit 109 of this router or another router, the congestion notification transfer unit 112 refers to the routing table 108 and transmits the N
The congestion notification is transferred via the HRP control path or the MPOA control path.

Referring also to FIG. 3, the edge device is:
It includes a congestion notification processing unit 214 in addition to the components already shown in FIG. Congestion notification processing unit 214
Analyzes the congestion notification received from the MPS via the control path for MPOA, and instructs the path switching control unit 213 to switch from the default path to the shortcut path.

Next, an operation in a network configuration having the present system will be described with reference to FIG.

As shown in FIG. 1, the host 31
A case in which congestion occurs in the router 13 when a packet is transferred to the router 13 (indicated by X in the figure) will be described. The congestion detection unit 109 of the router 13 includes a transmission buffer 105 and a reception buffer 1 provided for each interface of the router.
06 to detect congestion. In this method, for example, a buffer is composed of a memory, and packets are written and read in order from the head address of the buffer, and the address of the buffer where the first packet is written and the last packet are written. It can be detected by comparing with the address of the buffer that is present. That is,
If the difference between the two addresses is close to the capacity of the memory, it can be determined that a congestion state has occurred.

Next, a pair (data flow) of the source IP address and the destination IP address of the packet is detected from the information of the IP header of the packet in the congested buffer, and the data flow to be switched to the shortcut path is determined. . As to which data flow is to be switched to the shortcut, for example, it can be considered that the switching is performed only for the data flow in which the most packets exist in the buffer.

Here, the source IP address and the destination address of the data flow most frequently present in the buffer in which the congestion has occurred are the IP addresses of the host 31 and the host 32, respectively.
If it is an address, the congestion detection unit 109 transfers this combination to the congestion notification generation unit 110. The congestion notification generation unit 110 generates a congestion notification message as shown in FIG. 4 using the IP address of the host 31 as a destination protocol address and the IP address of the host 32 as a target protocol address, and sends the message to the congestion notification transfer unit 112. This message format is a new message type of the NHRP message.

In FIG. 4, the congestion notification message in the path switching system according to the present embodiment has a “Fixed Header”
(Operation type = 134) and "Common Header"
And "CIE".

"Common Header" is "Src Proto Len
"," Dest Proto Len "," Flags ", and" Request
ID "," Source NBMA Address ", and" Sou
rce Protocol Address '' and `` Dest Protocol Address
".

CIE (Client Information Entry) is
“Code”, “Prefix”, and “Maxmum Transmission Un
it "," Holding Time "," Cli Addr T / L ", and" Cl
i Proto Len ”,“ Preference ”and“ Client NB
MA Address "and" Client NBMA Sub Addres
s "and" Client Protocol Address ". Do not use the "unused" part.

Note that "Source NBMA Address"
(Source NBMA address) is the ATM address of the MPS that has detected congestion, and “Source Protocol Address” is the I / O of the MPS that has detected congestion.
The P address, the "Dest Protocol Address" (destination protocol address) is the destination IP address for transmitting the congestion notification, and the "Client Protocol Address" (target protocol address) is when the edge device that has received the congestion notification sets a shortcut path. Destination IP used for
It is assumed that each is set in the device.

The congestion notification message in the above format is indicated by an arrow in FIG. Referring back to FIG. 1, the congestion notification transfer unit 112 refers to the routing table 108 and
The next transfer destination for 1) can be determined to be the router 12. Therefore, this message is transferred to the NHRP control path 602 between the routers in the same manner as the NHRP message.

The congestion notification transfer unit 112 of the router 12
The destination protocol address (host 3) described in the congestion notification message is referred to by referring to the routing table 108.
The next transfer destination for 1) can be determined to be the router 11. Therefore, this message is transferred to the router 11 through the NHRP control path 601.

In the congestion notification transfer unit 112 of the router 11,
The destination protocol address (host 3) described in the congestion notification message is referred to by referring to the routing table 108.
It can be determined that 1) can be reached via the edge device 21. Therefore, this message is transferred to the edge device 21 through the MPOA control path 701.

The congestion notification message from the router 11 is
Edge device 2 received by POA control path 701
In step 1, this message is processed by the congestion notification processing unit 214. The congestion notification processing unit 214 takes out the target protocol address (host 32) of this message and sends a switching instruction request including this address to the path switching control unit 213 to instruct switching from the default path to the shortcut path.

Upon receiving the switching instruction request, the path switching control unit 213 receives the MPOA address for the target IP address (host 32) specified by the congestion notification processing unit 214 in the same manner as when the counter value exceeds the threshold value. The ATM address of the outgoing edge device 22 is resolved by the resolution request, and the edge device 21-the edge device 22 are resolved.
A shortcut VC 301 is set in between, and this VCI is recorded in the input cache 210. Thereafter, the input processing unit 2
At 09, the input cache 210 is referred to, and the data packet whose destination IP address is the host 32 is transferred by the shortcut path 2.

Next, another embodiment of the path switching system according to the present invention will be described with reference to FIGS.

The difference between the above-described embodiment and this embodiment will be described. First, in the configuration of the router of FIG. 5, when the congestion notification transfer unit 112 receives the congestion notification from the congestion notification generation unit 110 of this router or another router, it transfers the message 100 to the routing processing unit 102, and transmits the E-LAN or The congestion notification is transferred via the data path between routers.

In the configuration of the edge device shown in FIG. 6, the congestion notification detecting unit 215 monitors an IP packet transferred from the E-LAN to the bridge unit. here,
When the congestion notification message as shown in FIG. 7 is detected, the packet is analyzed without being transferred to the bridge side, and the path switching control unit 213 is instructed to switch from the default path to the shortcut path. It is assumed that the congestion notification detection unit 215 can detect only a specific message as shown in FIG.
No processing of P is required.

In FIG. 7, the congestion notification message in the path switching system of the present embodiment includes “Version”
"IHL (Internet Header Length)" and "TOS
(TypeOf Service) "," Length ", and" Identific
ation "," Flag "," Flagment Offset "
“TTL (Time To Live)”, “Protocol” and “He
ader Checksum "," Source IP Address ", and" De
st IP Address "and" Target IP Address ".

Note that “Source IP Address” (source I
P) indicates “Dest” to the IP address of the MPS that has detected congestion.
"IP Address" (destination IP address) is the destination IP address for transmitting the congestion notification, and "Target IP Address" is (target IP address) for the destination IP used when the edge device that has received the congestion notification sets a shortcut path. It is assumed that each address is set. "Pr
It is assumed that a new protocol ID of "otocol" is used.

The congestion notification message in the above format is indicated by an arrow in FIG.

Next, the operation of the present system will be described with reference to FIG.

The operation of this system is the same as that of the embodiment shown in FIGS. 1 to 4 except that the congestion notification message is transferred in the same manner as a normal data packet through a data path between routers or an E-LAN. Operation is the same.

In FIG. 8, the congestion notification generation unit 110 generates a congestion notification message as shown in FIG. 7 in which the IP address of the host 31 is set to the destination IP address and the IP address of the host 32 is set to the target IP address. It is sent to the transfer unit 112. This message format is a new protocol type overlaid on IP. The congestion notification transfer unit 112 transfers this message to the routing processing unit 102. The routing processing unit 102 refers to the routing table 108, and can determine that the next transfer destination for the destination IP address (host 31) is the router 12. Therefore, this message is transferred to the inter-router data path 502 as a normal data packet.

The routers 12 and the respective routing processors 102 in the router 11 refer to the routing table 108 and transfer the congestion notification message as a normal data packet. As a result, the congestion notification message is transferred via the inter-router data path 501 and the E-LAN 401.

In the edge device 21, the congestion notification is detected by the congestion notification detection unit 215, the target IP address (host 32) of this message is extracted, and a switching instruction request including this address is sent to the path switching control unit 213. This instructs switching from the default path to the shortcut path.

As described above, in the system according to the present embodiment, the congestion notification is transferred as a normal data packet, so that the router on the way does not need the processing for the congestion notification.

That is, in the present system, the function of detecting congestion in the router on the default path and notifying the edge device and notifying the edge device of the congestion triggers the data flow between the hosts that caused the congestion to be the shortcut path. The function of switching is provided. Therefore M
Even when the default route of the POA is congested, it is possible to return from the congested state.

Further, the second communication between the hosts which has caused the congestion
In order to switch the data flow of this to the shortcut path,
The throughput on the default route between the first hosts is improved, and the packet count per unit time at the edge device is increased. For this reason, in a state where the default route can be obtained without congestion,
When there is a first data flow between certain hosts where switching to a shortcut path by MPOA occurs,
When the congestion caused by the second data flow between different hosts on the default route makes it impossible to obtain the throughput of the first data flow and the switching to the shortcut path does not occur, This first
The data flow is also switched to the shortcut.

The present invention can take the following aspects in connection with the description of the claims.

(6) The path switching system according to any one of claims 1 to 5, wherein the network is a multi-protocol over ATM network.

(7) The path switching system according to any one of claims 1 to 6, wherein the shortcut path is a path directly connecting edge devices.

[0067]

As described above, the present invention switches the packet transfer route from the default path to the shortcut path in response to the detection of the congestion state of the default path. There is an effect that it is possible to return from.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a path switching system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of a router in FIG.

FIG. 3 is a block diagram illustrating an internal configuration of the edge device in FIG. 1;

FIG. 4 is a diagram showing a format of a congestion notification message in the path switching system of FIG. 1;

FIG. 5 is a block diagram showing an internal configuration of a router of a path switching system according to another embodiment of the present invention.

FIG. 6 is a block diagram showing an internal configuration of an edge device of a path switching system according to another embodiment of the present invention.

FIG. 7 is a diagram showing a format of a congestion notification message in a path switching system according to another embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a path switching system according to another embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a conventional path switching system.

FIG. 10 is a block diagram illustrating a configuration of a router in the path switching system of FIG. 9;

FIG. 11 is a block diagram illustrating a configuration of an edge device in the path switching system of FIG. 9;

[Explanation of symbols]

 11-14 Router 21,22 Edge device 31,32 Host 401,402 E-LAN 101 MPS 201 MPC

Claims (5)

[Claims] 1. A path switching system in a network having a default path and a shortcut path and transferring packets using these paths, wherein a packet transfer path is provided in response to detection of a congestion state of the default path. A path switching control means for switching from the default path to the shortcut path. 2. The method according to claim 1, wherein the path switching unit detects congestion in accordance with a storage state of a buffer for temporarily storing a packet transferred by the default path, and sets a transfer path in response to the congestion detection. 2. The path switching system according to claim 1, further comprising: a path switching unit that switches from a default path to the shortcut path. 3. The network includes an edge device that is a source and a destination of the packet, and a router that relays the packet. The congestion detecting unit is provided in the router, and the path switching unit is an edge device. 3. The path switching system according to claim 2, wherein said path switching unit is provided with a notification of congestion detection by said congestion detection unit. 4. The path switching system according to claim 3, wherein the notification of the congestion detection from the congestion detection unit to the path switching unit is performed using a control path. 5. The path switching system according to claim 3, wherein the notification of the congestion detection from the congestion detection unit to the path switching unit is performed using a data path.