1 / 20

BGP Update

Learn about Graceful Restart, Cooperative Route Filtering, Extended Communities, Route Refresh, and more updates in BGP protocol. Understand deployment guidelines and avoid common pitfalls for better network operation.

calejandra
Download Presentation

BGP Update

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BGP Update John Scudder jgs@cisco.com October 24, 2000

  2. Overview • New stuff • Graceful Restart • Cooperative Route Filtering, Prefix-ORF • Extended Communities • Route Refresh • Tweaks, frobs, cleanup • Revisions of base spec, Route Reflection, Confederations, Capabilities, MP-BGP

  3. Base Spec • draft-ietf-idr-bgp4-10.txt • Fix ambiguities about MED • Actually, this part is not so new • Otherwise, mostly editorial

  4. Graceful Restart • draft-ramachandra-bgp-restart-03.txt • a.k.a. NSF • When BGP restarts, continue forwarding for some (short) period of time • Avoid route flap • Non-intrusive upgrades, less harmful failures • Some risk of transient blackholes/loops • But route flaps have their own risks

  5. Graceful Restart Mechanism • Capability includes • flags (currently restarting or not, preserved FIB or not) • timer (time to wait for me to restart) • “End of RIB” message

  6. Graceful Restart Mechanism • When BGP stops, neighbors don’t drop TCP session right away, wait for timer instead • When BGP restarts, neighbors don’t flush old routes immediately — wait to converge • Old routes are flushed after convergence (or after a timer expires)

  7. Graceful Restart Example … and advertises its new RIB, replacing the marked routes. BGP comes back up and establishes new sessions with B and C. BGP halts on A. B and C’s RIBs and A’s FIB all mark routes for later deletion. Once B and C have sent all their routes, A runs best path, populates its FIB When A has finished advertising its RIB, any marked routes which weren’t replaced are flushed. B and C send their routes to A. A stores them in its RIB. Router A Router B RIB: (routes from A) (other routes) RIB: (new routes from A) (other routes) RIB: (routes from A) (other routes) RIB: (routes from B) RIB: RIB: (routes from B) (routes from C) RIB: (routes from B) (routes from C) Router C FIB: (routes from B) (routes from C) FIB: (routes from B) (routes from C) FIB: (new routes from B) (new routes from C) RIB: (routes from A) (other routes) RIB: (new routes from A) (other routes) RIB: (routes from A) (other routes)

  8. Route Refresh • RFC 2918 • Allows a router to request neighbor to re-send its whole Adj-RIB-Out • Permits soft reconfig without storing filtered Adj-RIB-In • Benefits: save memory • Drawbacks: extra communication, CPU when inbound policy is changed

  9. Cooperative Route Filtering • draft-chen-bgp-route-filter-01.txt,draft-chen-bgp-prefix-orf-00.txt • Lets router export its filtering policy to neighbor • Community and prefix policies are specified so far • Reduces communication and CPU on both ends

  10. Cooperative Route Filtering Mechanism • Outbound Route Filters (ORFs) are sent along with Route Refresh • So far communities and prefix lists are specified, simple encoding • Each AFI/SAFI can have its own ORFs • Can change filters by sending new Route Refresh request • Peer can use ORFs to filter outbound routes

  11. Refresh + ORF Example ORF Comm 2 ORF Comm 3 Router B Router A OPEN, Refresh, ORF = Comm 2 Comm 1 2 2 3 Pfx 10.0.1 10.0.2 10.0.3 10.0.4 Announce 10.0.2, 10.0.3 Refresh, ORF = Comm 3 w/d 10.0.2, 10.0.3, Announce 10.0.4

  12. Extended Communities • draft-ramachandra-bgp-ext-communities-04.txt • 8-byte, more structured communities • 2 byte type, 6 byte value. Type determines format of value. • Value typically includes originator’s IP address or AS number • Defined types: route target, route origin, link bandwidth • Currently used for network-based VPNs

  13. Route Reflection • RFC 2796 • Changes vs. RFC 1966 • Editorial cleanup • Deployment section with some points regarding MED, avoidance of loops • No fundamental changes

  14. Confederations • draft-ietf-idr-bgp-confed-rfc1965bis-01.txt • Changes vs. RFC 1965 • Corrections to reflect reality — particularly reverse code points for CONFED_SEQ and CONFED_SET. • Editorial changes • Expanded deployment section with discussion of MED, routing loops • No fundamental changes

  15. Deployment Guidelines • RR and clusters scale by hiding routes • This changes some BGP assumptions • To avoid trouble: • Avoid overlapping clusters/sub-ASes • Set IGP metrics to prefer intra-cluster (or sub-AS) paths

  16. Why Avoid Overlapping Clusters? • Well-known problem (I hope!) • Avoid simply by making clusters/sub-ASes follow topology RR 2 B RR 1 A

  17. 1 RR 1 RR 2 4 5 10 A B C AS X AS Y MED 1 AS Y MED 2 Why Set IGP Metrics To Prefer Intra-Cluster Paths? A, IGP 5 C, IGP 10, MED 1 * * * * * B, IGP 4, MED 2 * * A, IGP 6 * C, IGP 11, MED 1 C, IGP 10, MED 1 B, IGP 5, MED 2

  18. Why Set IGP Metrics To Prefer Intra-Cluster Paths? A, IGP 5 C, IGP 10, MED 1 * * B, IGP 4, MED 2 A, IGP 17 C, IGP 10, MED 1 12 RR 1 RR 2 4 5 10 A B C AS X AS Y MED 1 AS Y MED 2

  19. Mailing List • IETF IDR Working Group mailing list — idr@merit.edu • For: • Discussion of BGP protocol itself • Discussion of operational needs, problems • Not: • “how do I build my network” • “vendor foo feature bar”

More Related