PLNOG 6: Robert Raszuk, Nana Ogawa - FIB table saving technique (with simple virtual aggregation)
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This document describes a technique called simple virtual aggregation that can save router memory by suppressing more specific routes in the Routing Information Base (RIB) and Forwarding Information Base (FIB) if they have the same next hop as the default route. It monitors the default route in the BGP table and suppresses installation of specific routes with the same next hop, reducing the number of routes in RIB/FIB. Testing on a Cisco 3825 router showed this reduced the memory used by BGP and RIB/FIB from 230MB to 73MB. The technique is based on an IETF draft and can help smaller routers avoid running out of data plane memory due to many internet routes.
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PLNOG 6: Robert Raszuk, Nana Ogawa - FIB table saving technique (with simple virtual aggregation)
- 1. Cisco Confidential 1© 2010 Cisco and/or its affiliates. All rights reserved. FIB table saving technique (with simple virtual aggregation) PLNOG Warszawa - Marzec 2011 Cisco Systems Robert Raszuk, raszuk@cisco.com Nana Ogawa, naogawa@cisco.com
- 2. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 • ookubo@sakura presentations at IRS 20090914 Mesurment RIB hit rate on real traffics Very low hit rate 99% traffics hit 3.67% tables • Default route check by Randy bush But bad manner with default route at upstream edges
- 3. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3
- 4. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 R R Customer Site EBGP EBGP IBGP IBGP EBGP ISP X ISP Y R FULL FULL BGP RIB/FIB Internet
- 5. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 R-C R-D R-E Customer Site FULL +default FULL FULL BGP RIB/FIB FULL FULL default + α R-F R-A R-B EBGP IBGPIBGP FULL EBGP ISP X ISP Y FULL Route Next hop Best path 0.0.0.0/0 R-D ✓ A R-C R-D ✓ B R-D ✓ C R-C R-D ✓ D R-C ✓ BGP Table Aggregate to default route Route Next hop 0.0.0.0/0 R-D C R-C D R-C RIB/FIB A, C, D A, B, C default Internet
- 6. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 R-C R-D R-E Customer Site FULL +default FULL FULL BGP RIB/FIB FULL FULL default + α R-F R-B EBGP IBGPIBGP FULL EBGP ISP FULL Route Next hop Best path 0.0.0.0/0 R-D ✓ A R-C R-D ✓ ✓ B R-C R-D ✓ ✓ BGP Table Route Next hop 0.0.0.0/0 R-D A R-C R-D B R-C R-D RIB/FIB A, B default Internet Default route from R-C is also needed to be suppressed Path A and B.
- 7. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 • Conditions for aggregation -monitors the default routes in the main BGP table. -If default route is installed in RIB and FIB, it suppresses any more specific route to be installed in RIB and FIB, if the next hop is the same as default route. -if multipath is enabled, only when two default would be coming via the same next-hop as that of multi-path, the specific multipath would be suppressed. • Simple configuration router bgp xxx table-map <route-map name> simple-va • This implementation is based on IETF draft, but not totally same. http://tools.ietf.org/html/draft-ietf-grow-simple-va-01 RIB/FIBAggregate to default route BGP
- 8. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 EBGP IBGP IBGP IBGP DIX-IE (IX) EBGP Verio (ISP) Internet EBGP C3825 394 routes 306,620 routes 46 routes 1 route WIDE network ISPs IBGP eBGP peers EBGP eBGP peers BGP route RIB/FIB route Memory taken by BGP and RIB/FIB Before 307,061 307,041 230 MB After 307,061 429 73 MB Reduce about 160MB memory
- 9. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 va-eft@cisco.com • It can save a lot of small routers from having their data plane overflow by lots of internet routes. • The real saving here would be normally also in the amount of FIB on line cards in distributed systems ( ex. cat6k) as well as significant reduction of IPC traffic • In next phase we could do the same for other aggregates .. not only for default route. But for now this is what we have discussed and agreed up on. • Tell us that this feature is useful or not…. • You can encourage your vendor to implement this feature.
- 10. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 • Ookubo-san report IRS21 http://irs.ietf.to/ • Randy’s report http://www.janog.gr.jp/meeting/janog24/program/st3.html • IETF draft http://tools.ietf.org/html/draft-ietf-grow-simple-va-01
- 11. Thank you.