JP2010178310A - Route control system and route control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for suppressing a useless route change. <P>SOLUTION: A route control system 1 is comprised of a first route control apparatus 10, which has a function for collecting internal border gateway protocol (IBGP) peers, for transmitting a route updating message and a second route control apparatus 20 for receiving the route updating message from the first route control apparatus. The first route control apparatus 10 transmits to the second route control apparatus a route updating message including update reason information indicating a reason why a route is to be updated. When the route updating message including the update reason information is received, the second route control apparatus 20 updates route information at the second route control apparatus in accordance with the update reason information. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a route control system and a route control device.

  BGP (Border Gateway Protocol), which is a route control protocol of IP network, is used for route control between independent management units called AS (Autonomous System), but also received by BGP, for example, in route control within AS. In some cases, BGP is used when advertising routes outside the AS to routers inside the AS via BGP. In order to distinguish between the two, the BGP inside the AS is usually called IBGP (Internal BGP), and the BGP between the ASs is called EBGP (External BGP).

  In principle, IBGP establishes peers with all BGP routers in the AS in order to prevent path loops. Therefore, if the number of BGP routers in the AS increases, the number of peers increases, which imposes a heavy burden on operation. As a method for solving this, there is a method using a route reflector.

  The route reflector is a BGP router having a function of aggregating IBGP peers. In the case of a configuration that does not use a route reflector, as shown in FIG. 4A, the number of peers increases because it is necessary to establish a full mesh peer between each BGP router in the AS. In this case, as shown in FIG. 4B, a normal BGP router only needs to establish peers with the route reflector, and the number of peers can be reduced. Note that the route reflector advertises a route update (UPDATE) message received from the BGP router via IBGP to other BGP routers.

BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP) ”, IETF RFC 4456.

  However, in a configuration using a route reflector, there may be a problem in route control. Hereinafter, this problem will be described with reference to FIG. FIG. 5A shows that there are three routers (routers A, B, and C) and a route reflector (indicated as “RR” in FIG. 5) in the AS, and all links are functioning normally. FIG. 5B illustrates a state where the link between the routers A and RR is disconnected from the state illustrated in FIG. As shown in FIG. 5, the router A receives an external route update message from the adjacent AS via the link (EBGP peer) with the router D of the adjacent AS, and the router B and the router E of the adjacent AS An external route update message is received from the neighboring AS by the link between the two (EBGP peer). Each router exchanges a route update message through a link (IBGP peer) with the RR. The number attached to each link is the link cost.

  The path control in the state of FIG. 5A (a state in which all links are functioning normally) is as follows. Assume that router A and router B receive a route update message for a prefix p from the neighboring AS. Further, regarding the route attribute of p, it is assumed that all route attributes related to the selection of the optimum route (best route) in BGP, such as the LOCAL_PREF attribute, the AS_PATH attribute, the ORIGIN attribute, and the MED attribute, are the same.

The router A and the router B broadcast the p route update message received from the neighboring AS to the RR by IBGP. NEXT_HOP of p advertised by router A is the address of router D or the address of router A (when NEXT_HOP is rewritten to its own address by router A), and NEXT_HOP of p advertised by router B is the address of router E Or the address of router B.
The RR compares the route update message from the router A with the route update message from the router B for p, and selects any route that has received the route update message as the optimum route to p. Specifically, since the route attributes are all the same as described above, the RR compares the costs for reaching the IP address described in the NEXT_HOP attribute of p, and the one with the smaller cost is assigned to p. Select as the best route. For example, when the link cost between the routers A and D and the link cost between the routers B and E are the same, the RR selects the route of the router A as the optimum route. Also, the RR advertises the route update message received from the router A to other routers by IBGP.
Router C receives the p route update message for which NEXT_HOP is the address of router A (or router D). Here, when router C forwards a packet addressed to p, NEXT_HOP to p is the address of router A (or router D), but the shortest path from router C to router A is a direct connection link with router A. Since it passes, the packet from router C to p is transferred to the adjacent AS through the link between router C and router A.

When the link between the router A and the RR is disconnected, as shown in FIG. 5B, the reach of NEXT_HOP to the p received from the router A is lost, that is, the cost becomes infinite. , P, the route of the router B is selected as the optimum route, and is advertised to other routers. In the router C, NEXT_HOP to p is changed to the address of the router B (or router E), and traffic from the router C to p flows through the router B to the adjacent AS.
That is, although the link between the routers C and A can actually be used, the traffic from the routers C to p is changed from the route through the router A to the route B with a large cost. Such a route change may cause packet loss, order reversal, etc., especially at the time of switching. Unexpected traffic changes can cause congestion in the network. Therefore, there is a problem that the network becomes unstable and adversely affects communication quality.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique for suppressing unnecessary route changes.

  In order to solve the above problem, a routing control system according to an aspect of the present invention includes a first routing controller that has a function of aggregating IBGP peers and transmits a routing update message, and a routing update from the first routing controller. A route control system comprising a second route control device that receives a message, wherein the first route control device transmits a route update message including update reason information indicating a reason for route update to the second route control device. The second route control device is characterized in that, when a route update message including update reason information is received, the route information in the second route control device is updated according to the update reason information.

  The route control system is a route control system including a first route control device having a function of aggregating IBGP peers and a second route control device that transmits and receives a route update message to and from the first route control device. Then, when the link cost to the NEXT_HOP on the optimum route selected from the plurality of routes that receive the route update message changes, the first route control device displays update reason information indicating the change as a reason for the route update. When the second route control device receives the route update message including the update reason information indicating the change as a reason, the second route control device until NEXT_HOP in the route information set in the second route control device. If the link cost is equal to or higher than the link cost up to NEXT_HOP on the route based on the route update message, May be characterized in that on the basis of the road update message does not update if the routing information set in the second path control unit updates, less than.

  The route control system is a route control system including a first route control device having a function of aggregating IBGP peers and a second route control device that transmits and receives a route update message to and from the first route control device. The first route control apparatus refers to a route update message receiving unit that receives route update messages from a plurality of routes, and a route update message received from the plurality of routes by the route update message receiving unit, and When the change of the link cost is recognized by the cost change recognizing unit, the cost change recognizing unit for recognizing the change of the link cost up to NEXT_HOP on the optimum route, the change is detected. A route update message for sending a route update message including update reason information shown as the reason for route update to the second route control device The second route control device, when receiving a route update message including update reason information indicating the change as a reason, a link to NEXT_HOP in the route information set in the second route control device The cost comparison unit that compares the cost and the link cost to NEXT_HOP on the route based on the route update message, and the link cost to NEXT_HOP in the route information set in the second route control device by the cost comparison unit is route update. When it is determined that the link cost to the NEXT_HOP on the route based on the message is equal to or higher than the link cost, the route information set in the second route control device is updated based on the route update message, while the second route control is performed. Link cost to NEXT_HOP in route information set in the device If it is determined to be less than the link cost up NEXT_HOP on the path based on the route update message may be characterized in that it comprises a routing information updating unit does not update the routing information based on the route update message.

  In order to solve the above problem, a route control device according to another aspect of the present invention receives a route update message including update reason information indicating the reason for route update from another device having a function of aggregating IBGP peers. When the route update message receiving unit and the route update message receiving unit receive a route update message including update reason information indicating the change in the link cost up to NEXT_HOP on the optimum route in another device as a reason, A cost comparison unit that compares the link cost to NEXT_HOP in the set route information with the link cost to NEXT_HOP on the route based on the route update message, and NEXT_HOP in the route information set in the own device by the cost comparison unit The link cost up to is on the route based on the route update message. When it is determined that the link cost is equal to or higher than the link cost up to EXT_HOP, the route information set in the own device is updated based on the route update message, while the link cost up to NEXT_HOP in the route information set in the own device is updated. Is determined to be less than the link cost up to NEXT_HOP on the route based on the route update message, the route information update unit does not update the route information based on the route update message.

  In order to solve the above problem, a route control device according to another aspect of the present invention includes a route update message receiving unit that receives a route update message from a plurality of routes, and a route update message receiving unit that is received from the plurality of routes. An optimal route selection unit that selects an optimal route from a plurality of routes, a cost change recognition unit that recognizes a link cost change to NEXT_HOP on the optimal route, and a cost change recognition unit A route update message transmission unit that transmits a route update message including update reason information indicating the change as a reason for route update to the other device when the change is recognized. Link to NEXT_HOP in the route information set in the other device when a route update message including the same is received The route information set in the other device is updated based on the route update message when the cost is equal to or higher than the link cost up to NEXT_HOP on the route based on the route update message, and is not updated when it is less than the link cost. It is characterized by that.

  According to the present invention, unnecessary route changes can be suppressed. Therefore, it becomes possible to suppress instability of the network and deterioration in communication quality due to unnecessary path change.

It is a lineblock diagram of route control system 1 by one embodiment of the present invention. 1 is an example of a network to which a routing control system 1 is applied. It is a flowchart which shows operation | movement of the route reflector 10a shown in FIG. 2, and operation | movement of the router 20c. It is a figure for demonstrating the structure of the conventional IBGP peer. It is a figure for demonstrating the problem of the conventional IBGP peer.

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a route control system 1 according to an embodiment of the present invention includes a first route control device 10 (corresponding to a route reflector) and a second route control device 20 (corresponding to a BGP router). The In FIG. 1, the path control system 1 describes only one second path control device 20, but the path control system 1 may include two or more second path control devices.

  The first route control apparatus 10 includes a route update message receiving unit 100, a cost change recognition unit 110, an optimum route selection unit 120, a route update message transmission unit 130, and a storage unit 190.

  The route update message receiving unit 100 receives route update messages from a plurality of routes. Specifically, the route update message receiving unit 100 receives a route update message from another BGP router (for example, a plurality of BGP routers connected to another AS). The route update message receiving unit 100 that has received the route update message stores the received route update message (or the content indicated by the route update message) in the storage unit 190. The receiving unit 100 that has received the route update message notifies the optimum route selection unit 120 of information indicating that the route update message has been received (hereinafter referred to as “message reception notification”).

  The storage unit 190 stores the route update message (or content indicated by the route update message) received by the route update message receiving unit 100. In addition, the storage unit 190 stores one route (hereinafter referred to as “optimum route”) having the lowest cost selected from the plurality of routes from which the route update message receiving unit 100 receives the route update message.

  The cost change recognition unit 110 recognizes a link cost change up to NEXT_HOP on the optimum route. For example, the cost change recognizing unit 110 refers to the optimum route stored in the storage unit 190, and when the link to the BGP router which is the NEXT_HOP on the optimum route is disconnected (when reachability is lost), the optimum route Recognize changes in link cost up to NEXT_HOP above. The cost change recognizing unit 110 that has recognized the change in the link cost up to NEXT_HOP on the optimum route shows information indicating that the change in the link cost to NEXT_HOP on the optimum route has been recognized (hereinafter referred to as “link cost change notification”). To the optimum route selection unit 120 and the route update message transmission unit 130.

  The optimum route selection unit 120 refers to the route update messages received from the plurality of routes by the route update message receiving unit 100, that is, the plurality of route update messages (or the contents indicated by the route update message) stored in the storage unit 190. The optimum route is selected from the plurality of routes. The optimum route selection unit 120 selects the optimum route when a message reception notification is notified from the route update message reception unit 100 or when a link cost change notification is notified from the cost change recognition unit 110. The optimum route selecting unit 120 that has selected the optimum route supplies the route update message transmitting unit 130 with the route update message (or the content indicated by the route update message) received from the optimum route by the route update message receiving unit 100. In addition, the optimum route selection unit 120 that has selected a new optimum route updates the optimum route stored in the storage unit 190.

  The route update message transmission unit 130 acquires a route update message (or content indicated by the route update message) from the optimum route selection unit 120. In addition, the route update message transmission unit 130 acquires a link cost change notification from the cost change recognition unit 110. When the route update message transmission unit 130 acquires the route update message (or the content indicated by the route update message) and the link cost change notification, the update reason indicating the change of the link cost up to NEXT_HOP on the optimum route as the reason for the route update. A route update message including information is transmitted (public information) to the second route control device 20. Note that the route update message including the update reason information is implemented, for example, by defining a spare area or an extension region in the format constituting the route update message as a storage area for the update reason information.

  The second route control device 20 includes a route update message reception unit 200, a cost comparison unit 210, a route information update unit 220, and a storage unit 290. The storage unit 290 stores route information (route table, Local-RIB) of the second route control device 20.

  The route update message receiving unit 200 receives a route update message from the first route control device 10. The route update message receiving unit 200 that has received the route update message supplies the received route update message to the cost comparison unit 210.

  The cost comparison unit 210 acquires a route update message from the route update message reception unit 200. The cost comparison unit 210 that has acquired the route update message refers to the update reason information included in the route update message, and if the update reason information indicates a link change as a reason for the route update, the cost comparison unit 210 stores the update reason information in the storage unit 290. The link cost to NEXT_HOP in the stored route information is compared with the link cost to NEXT_HOP on the route based on the route update message. The cost comparison unit 210 supplies the route update message acquired from the route update message reception unit 200 and the comparison result to the route information update unit 220.

  The route information update unit 220 acquires a route update message and a comparison result from the cost comparison unit 210. The route information update unit 220 determines the cost of the comparison result that the link cost to NEXT_HOP in the route information set in the second route control device 20 is equal to or higher than the link cost to NEXT_HOP on the route based on the route update message. When acquired from the comparison unit 210, that is, the link cost to NEXT_HOP on the route based on the route update message is the same as the link cost to NEXT_HOP in the route information stored in the storage unit 290 or stored in the storage unit 290. If the link cost to the NEXT_HOP in the existing route information is smaller, the route information stored in the storage unit 290 is updated based on the route update message acquired from the cost comparison unit 210. On the other hand, the route information update unit 220 compares the link cost to NEXT_HOP in the route information set in the second route control device 20 to be less than the link cost to NEXT_HOP on the route based on the route update message. Is obtained from the cost comparison unit 210, that is, when the link cost to NEXT_HOP on the route based on the route update message is larger than the link cost to NEXT_HOP in the route information stored in the storage unit 290, the storage unit 290 The route information is not updated.

  Hereinafter, the route control system 1 will be described supplementarily using specific examples. FIG. 2 shows a network (AS) to which the routing control system 1 is applied. In FIG. 2, the route reflector 10 a corresponds to the first route control device 10, and the router 20 c corresponds to the second route control device 20. The router 20c establishes a peer with the route reflector 10a using IBGP and exchanges a route update message. In AS, a routing protocol generally used in AS, such as OSPF and ISIS, generally called IGP (Interior Gateway Protocol) is also operating.

The route reflector 10a transmits a route update message including the reason for route update (update reason information) to the router 20c. The main reasons for route update are as follows.
Reason 1: A route update message for whitdrawing the route is received from the optimum route.
Reason 2: A route update message indicating a path attribute such that the route becomes the optimum route is received from a route other than the optimum route.
Reason 3: The path attribute of the optimal route has been changed (the receiving source of the optimal route whose path attribute has been changed is unchanged).
Reason 4: As a result of changing the path attribute of the optimum route, the route received from another route is given priority over the optimum route.
Reason 5: As a result of changing the cost to NEXT_HOP of the optimum route, the cost to NEXT_HOP of another route that has received another route update message is smaller.
However, among reasons 1 to 5, reason 5 is related to the above-described problem.

  The community attribute is used as means for including the update reason information in the route update message. The community attribute is used for performing different route control for each defined route group. The community attribute is expressed by 32 bits. The upper 16 bits are defined as the self AS number, and the lower 16 bits are defined as an arbitrary area. Therefore, the lower 16 bits of the community attribute are defined as the update reason information area, and the value of the community attribute (hereinafter referred to as “community attribute value”) is defined. For example, reason 5 is defined as community attribute value “1”, and reasons other than reason 5 (reasons 1 to 4) are defined as community attribute value “2”.

  FIG. 3A is a flowchart showing the operation of the route reflector 10a shown in FIG. In addition, the flowchart shown to Fig.3 (a) is started when the optimal path | route changes (step S100). The route reflector 10a determines whether or not the cost up to the next route NEXT_HOP has been changed (step S110). That is, the route reflector 10a determines whether or not the optimum route has been changed for the reason 5.

  When the route reflector 10a determines that the cost up to NEXT_HOP of the optimum route has been changed (step S110: Yes), the route reflector 10a transmits a route update message in which the community attribute value “1” is set to the router 20c (step S120). That is, the route reflector 10a transmits the route update message including the update reason information indicating the reason 5 as the route update reason to the router 20c. Then, this flowchart ends.

  On the other hand, when the route reflector 10a determines that the cost up to the NEXT_HOP of the optimum route has not been changed (step S110: No), the route reflector 10a transmits a route update message in which the community attribute value “2” is set (step S130). That is, the route reflector 10a transmits the route update message including the update reason information indicating that the reason for the route update is other than the reason 5 to the router 20c. Then, this flowchart ends.

  FIG. 3B is a flowchart showing the operation of the router 20c shown in FIG. The flowchart shown in FIG. 3B starts when a route update message is received from the route reflector 10a (step S200). The router 20c determines whether or not a community attribute (update reason information) is included in the received route update message (step S210). When the router 20c determines that the community attribute is included in the route update message (step S210: Yes), the router 20c determines whether or not the community attribute value is “1” (step S220). When the router 20c determines that the community attribute value is “1” (step S220: Yes), the link cost up to NEXT_HOP in the current route information (route information stored in the storage unit 290) is included in the route update message. It is determined whether or not the link cost up to NEXT_HOP on the route is higher (step S230).

  When the router 20c determines that the link cost to NEXT_HOP in the current route information (route information stored in the storage unit 290) is equal to or higher than the link cost to NEXT_HOP on the route based on the route update message (step S230). : Yes), the route information is updated based on the route update message (step S240). That is, the router 20c determines that the route information based on the route update message has priority over the current route information, and reflects the contents of the route update message (check other policies). Therefore, NEXT_HOP is changed in the router 20c. The route information is created by IGP. And this flowchart is complete | finished.

  On the other hand, when the router 20c determines that the link cost to NEXT_HOP in the current route information (route information stored in the storage unit 290) is not equal to or higher than the link cost to NEXT_HOP on the route based on the route update message (step S230: No), although the route update message is retained, the content of the route update message is not reflected (step S240 is skipped). That is, the router 20c determines that the current route information has priority over the route information based on the route update message, and ignores the content of the route update message. Therefore, NEXT_HOP is not changed in the router 20c. And this flowchart is complete | finished.

  If the router 20c determines that the route update message does not include the community attribute (step S210: No) or determines that the route attribute does not have the community attribute value “1” (step S220: No), the route update is performed. The route information is updated based on the message (step S240). And this flowchart is complete | finished.

  As described above, when the BGP router that establishes an IBGP peer with the route reflector receives a route update message in which only the NEXT_HOP attribute is changed for a certain prefix from the route reflector, the previous NEXT_HOP and the new NEXT_HOP to the prefix are received. Only when the cost up to the new NEXT_HOP is the same as or lower than the previous NEXT_HOP, the route update message from the route reflector is accepted and the route information is updated.

  As described above, according to the route control system 1 according to the embodiment of the present invention, unnecessary route changes can be suppressed. Therefore, it becomes possible to suppress instability of the network and deterioration in communication quality due to unnecessary path change. The effect of maintaining the stability of the network and not deteriorating the communication quality can be expected.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 1 Path control system 10 1st path control apparatus (route reflector) 20 2nd path control apparatus (BGP router) 100 Path update message receiving part 110 Cost change recognition part 120 Optimal path selection part 130 Path update message transmission part 190 Storage part 200 Route update message reception unit 210 Cost comparison unit 220 Route information update unit 290 Storage unit

Claims (5)

A route control system comprising a first route control device that has a function of aggregating IBGP peers and transmits a route update message, and a second route control device that receives the route update message from the first route control device. There,
The first path control device
Sending the route update message including update reason information indicating the reason for route update to the second route control device;
The second path control device
When the route update message including the update reason information is received, route information in the second route control device is updated according to the update reason information. A path control system comprising a first path control device having a function of aggregating IBGP peers and a second path control device that transmits and receives the path update message to and from the first path control device,
The first path control device
When the link cost to NEXT_HOP on the optimum route selected from a plurality of routes that receive the route update message changes, the route update message including update reason information indicating the change as a reason for route update is transmitted,
The second path control device
When the route update message including the update reason information indicating the change as the reason is received, the link cost to NEXT_HOP in the route information set in the second route control device is based on the route update message. The route information set in the second route control device is updated based on the route update message when it is equal to or higher than the link cost up to the next NEXT_HOP, and is not updated when it is less than the link cost. Routing system. A path control system comprising a first path control device having a function of aggregating IBGP peers and a second path control device that transmits and receives the path update message to and from the first path control device,
The first path control device
A route update message receiver that receives the route update message from a plurality of routes;
An optimum route selection unit that refers to the route update message received from a plurality of routes by the route update message reception unit, and selects an optimum route from the plurality of routes;
A cost change recognizing unit for recognizing a link cost change up to NEXT_HOP on the optimum route;
When a change in the link cost is recognized by the cost change recognizing unit, a route update message is transmitted that transmits the route update message including update reason information indicating the change as a reason for route update to the second route control device. With
The second path control device
When the route update message including the update reason information indicating the change as the reason is received, a link cost to NEXT_HOP in the route information set in the second route control device and a route based on the route update message A cost comparison unit for comparing the link cost up to NEXT_HOP above;
When it is determined by the cost comparison unit that the link cost to NEXT_HOP in the route information set in the second route control device is equal to or higher than the link cost to NEXT_HOP on the route based on the route update message, The route information set in the second route control device is updated based on the route update message, while the link cost to NEXT_HOP in the route information set in the second route control device is based on the route update message. A route control system comprising: a route information update unit that does not update the route information based on the route update message when it is determined that the link cost is lower than NEXT_HOP on the route. A route update message receiving unit for receiving a route update message including update reason information indicating the reason for route update from another device having a function of aggregating IBGP peers;
When the route update message receiving unit receives the route update message including the update reason information indicating the change in the link cost up to NEXT_HOP on the optimum route in the other device as the reason, the route update message receiving unit is set in the own device. A cost comparison unit that compares the link cost to NEXT_HOP in the route information and the link cost to NEXT_HOP on the route based on the route update message;
When it is determined by the cost comparison unit that the link cost to NEXT_HOP in the route information set for the own device is equal to or higher than the link cost to NEXT_HOP on the route based on the route update message, the route update message While updating the route information set in the own device based on the link information, the link cost to NEXT_HOP in the route information set in the own device is less than the link cost to NEXT_HOP on the route based on the route update message. And a route information update unit that does not update the route information based on the route update message when determined. A route update message receiver that receives the route update message from a plurality of routes;
An optimum route selection unit that refers to the route update message received from a plurality of routes by the route update message reception unit and selects an optimum route from the plurality of routes;
A cost change recognizing unit for recognizing a link cost change up to NEXT_HOP on the optimum route;
A route update message transmission unit that transmits the route update message including update reason information indicating the change as a reason for route update when the change of the link cost is recognized by the cost change recognition unit; Prepared,
The other device is
When the route update message including the update reason information is received, the link cost to NEXT_HOP in the route information set in the other device is equal to or higher than the link cost to NEXT_HOP on the route based on the route update message. In some cases, the route control device updates the route information set in the other device based on the route update message, and does not update the route information if it is less than the route information.

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