REDUCED TRAFFIC LOSS FOR BORDER GATEWAY PROTOCOL SESSIONS IN MULTI-HOMED NETWORK CONNECTIONS

• US 20130259058A1
• Filed: 03/31/2012
• Published: 10/03/2013
• Est. Priority Date: 03/31/2012
• Status: Active Grant

• Current Assignee: Juniper Networks Incorporated
• Original Assignee: Juniper Networks Incorporated
• Inventors: Vairavakkalai, Kaliraj
• Granted Patent: US 9,137,142 B2
• Time in Patent Office: Days
• US Class Current: 370/401
• CPC Class Codes: H04L 45/023 Delayed use of routing table updates
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing

Abstract

This disclosure describes techniques to reduce traffic loss for a Border Gateway Protocol (BGP) session by delaying re-advertisement of routes received from a newly re-established multi-homed router by a primary router until all the routes are installed in a forwarding plane of the primary router. The techniques of this disclosure make use of a BGP marker received from the multi-homed router that indicates the end of a route download for an address family. Upon receiving the BGP marker, a control plane of the primary router requests a route acknowledgement message (Route-ACK) from the forwarding plane for only the last route of the address family received before the BGP marker. When the control plane receives the Route-ACK indicating that the last route has been installed in the forwarding plane, the primary router initiates re-advertisement of the routes to other BGP peer routers.

Claims

1. A method comprising:

receiving, with a primary router, advertised routes from a multi-homed router via a Border Gateway Protocol (BGP) session, wherein the multi-homed router is connected to the primary router and a backup router;

updating, in a control plane of the primary router, routing information in a routing table based on the received routes;

installing, in a forwarding plane of the primary router, forwarding data structures for the received routes in forwarding tables based on the routing information; and

deferring re-advertisement of the routes to BGP peer routers until the control plane receives an acknowledgement from the forwarding plane indicating that a last route received from the multi-homed router is installed in the forwarding tables of the forwarding plane.

2. The method of claim 1, further comprising:

receiving a BGP marker indicating an end of a route download from the multi-homed router; and

in response to receiving the BGP marker, requesting, with the control plane, the acknowledgement from the forwarding plane indicating that the last route from the multi-homed router is installed in the forwarding tables.

3. The method of claim 1, further comprising, upon receiving, with the control plane, the acknowledgement from the forwarding plane indicating that the last route from the multi-homed router is installed in the forwarding tables, re-advertising all the routes to the BGP peer routers.

4. The method of claim 1, further comprising:

receiving a BGP marker indicating an end of a route download from the multi-homed router; and

in response to receiving the BGP marker, issuing a route change request for the last route received from the multi-homed router before receiving the BGP marker.

5. The method of claim 4, wherein issuing a route change request for the last route comprises:

locating the last route in the routing table in the control plane;

setting an acknowledgment flag associated with the last route in the routing table;

sending the route change request for the last route to a kernel of the primary router;

requesting, with the kernel, the acknowledgement from the forwarding plane indicating that the last route is installed in the forwarding tables;

receiving, with the kernel, the acknowledgement from the forwarding plane when the last route has been installed in the forwarding tables; and

upon receiving the acknowledgement, clearing the acknowledgment flag from the routing table, wherein clearing the acknowledgment flag triggers re-advertisement of the routes to the BGP peer routers.

6. The method of claim 1, further comprising:

generating, with a kernel of the primary router, an acknowledgement request for the last route and an acknowledgment cookie associated with the acknowledgment request;

mapping, in the control plane, the acknowledgement cookie to the last route;

upon receiving the acknowledgement from the forwarding plane in response to the acknowledgment request, identifying the last route based on the acknowledgment cookie associated with the acknowledgment request.

7. The method of claim 1, further comprising receiving, with the primary router, advertised routes of one or more address families negotiated for the BGP session from the multi-homed router, wherein each address family comprises a last route.

8. The method of claim 1, further comprising reestablishing the BGP session between the primary router and the multi-homed router after a failure of the BGP session.

9. The method of claim 1, wherein deferring re-advertisement of the routes to BGP peer routers comprises executing a BGP protocol in the control plane of the primary router with a deferred advertisement extension.

10. The method of claim 1, wherein, during the deferred re-advertisement of the routes at the primary router, traffic is sent to the multi-homed routed via the backup router.

22. The computer-readable medium of claim 1, further comprising instructions that cause the processor to:

receive a BGP marker indicating an end of a route download from the multi-homed router; and

in response to receiving the BGP marker, request, with the control plane, the acknowledgement from the forwarding plane indicating that the last route from the multi-homed router is installed in the forwarding tables.

11. A primary router in a multi-homed network connection, the primary router comprising:

interfaces configured to receive advertised routes from the multi-homed router via a Border Gateway Protocol (BGP) session, wherein the multi-homed router is connected to the primary router and a backup router; and

a control unit configured to update routing information in a routing table in a control plane of the primary router based on the received routes, install forwarding data structures for the received routes in forwarding tables in a forwarding plane of the primary router based on the routing information, and defer re-advertisement of the routes to BGP peer routers until the control plane receives an acknowledgement from the forwarding plane indicating that a last route received from the multi-homed router is installed in the forwarding tables of the forwarding plane.

12. The primary router of claim 11, wherein:

the interfaces receive a BGP marker indicating an end of a route download from the multi-homed router; and

in response to receiving the BGP marker, the control unit requests the acknowledgement from the forwarding plane indicating that the last route from the multi-homed router is installed in the forwarding tables.

13. The primary router of claim 11, further comprising, upon receiving the acknowledgement from the forwarding plane indicating that the last route from the multi-homed router is installed in the forwarding tables, the control unit re-advertising all the routes to the BGP peer routers.

14. The primary router of claim 11, wherein:

the interfaces receive a BGP marker indicating an end of a route download from the multi-homed router; and

in response to receiving the BGP marker, the control unit issues a route change request for the last route received from the multi-homed router before receiving the BGP marker.

15. The primary router of claim 14,

wherein the control unit locates the last route in the routing table in the control plane, sets an acknowledgment flag associated with the last route in the routing table, and sends the route change request for the last route to a kernel of the primary router;

wherein the kernel requests the acknowledgement from the forwarding plane indicating that the last route is installed in the forwarding tables, and receives the acknowledgement from the forwarding plane when the last route has been installed in the forwarding tables; and

wherein, upon receiving the acknowledgement with the kernel, the control unit clears the acknowledgment flag from the routing table and triggers re-advertisement of the routes to the BGP peer routers.

16. The primary router of claim 14, further comprising a kernel configured to generate an acknowledgement request for the last route and an acknowledgment cookie associated with the acknowledgment request, wherein the control unit maps the acknowledgement cookie to the last route, and, upon receiving the acknowledgement from the forwarding plane in response to the acknowledgment request, identifies the last route based on the acknowledgment cookie associated with the acknowledgment request.

17. The primary router of claim 14, wherein the interfaces receive advertised routes of one or more address families negotiated for the BGP session from the multi-homed router, wherein each address family comprises a last route.

18. The primary router of claim 14, wherein the control unit reestablishes the BGP session between the primary router and the multi-homed router after a failure of the BGP session.

19. The primary router of claim 14, wherein the control unit executes a BGP protocol with a deferred advertisement extension in order to defer re-advertisement of the routes to the BGP peer routers.

20. The primary router of claim 14, wherein, during the deferred re-advertisement of the routes at the primary router, traffic is sent to the multi-homed routed via the backup router.

21. A computer-readable medium comprising instructions that when executed cause a processor of a primary router to:

receive advertised routes from a multi-homed router via a Border Gateway Protocol (BGP) session, wherein the multi-homed router is connected to the primary router and a backup router;

update, in a control plane of the primary router, routing information in a routing table based on the received routes;

install, in a forwarding plane of the primary router, forwarding data structures for the received routes in forwarding tables based on the routing information; and

defer re-advertisement of the routes to BGP peer routers until the control plane receives an acknowledgement from the forwarding plane indicating that a last route received from the multi-homed router is installed in the forwarding tables of the forwarding plane.

23. The computer-readable medium of claim 21, further comprising instructions that cause the processor to, upon receiving the acknowledgement from the forwarding plane indicating that the last route from the multi-homed router is installed in the forwarding tables, re-advertise all the routes to the BGP peer routers.

24. The computer-readable medium of claim 21, further comprising instructions that cause the processor to:

receive a BGP marker indicating an end of a route download from the multi-homed router; and

in response to receiving the BGP marker, issue a route change request for the last route received from the multi-homed router before receiving the BGP marker.

25. The computer-readable medium of claim 24, wherein the instructions further cause the processor to:

locate the last route in the routing table in the control plane;

set an acknowledgment flag associated with the last route in the routing table;

send the route change request for the last route to a kernel of the primary router;

request, with the kernel, the acknowledgement from the forwarding plane indicating that the last route is installed in the forwarding tables;

receive, with the kernel, the acknowledgement from the forwarding plane when the last route has been installed in the forwarding tables; and

upon receiving the acknowledgement, clear the acknowledgment flag from the routing table, wherein clearing the acknowledgment flag triggers re-advertisement of the routes to the BGP peer routers.

26. The computer-readable medium of claim 21, further comprising instructions that cause the processor to:

generate, with a kernel of the primary router, an acknowledgement request for the last route and an acknowledgment cookie associated with the acknowledgment request;

map, in the control plane, the acknowledgement cookie to the last route; and

upon receiving the acknowledgement from the forwarding plane in response to the acknowledgment request, identify the last route based on the acknowledgment cookie associated with the acknowledgment request.