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

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

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

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

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

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)

Graceful Restart Example … and advertises its new RIB, replacing the marked routes. Once B and C have sent all their routes, A runs best path, populates its FIB 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. B and C send their routes to A. A stores them in its RIB. When A has finished advertising its RIB, any marked routes which weren’t replaced are flushed. Router A Router B RIB: (routes from A) (other routes) RIB: (routes from A) (other routes) RIB: (new routes from A) (other routes) RIB: (routes from B) (routes from C) RIB: RIB: (routes from B) RIB: (routes from B) (routes from C) Router C FIB: (new routes from B) (new routes from C) FIB: (routes from B) (routes from C) FIB: (routes from B) (routes from C) RIB: (routes from A) (other routes) RIB: (routes from A) (other routes) RIB: (new routes from A) (other routes)

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

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

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

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

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

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

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

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

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

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 10, MED 1 C, IGP 11, MED 1 B, IGP 5, MED 2 A B C AS X AS Y MED 2 MED 1 RR 1 RR 2 5 4 1 10

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 2 AS Y MED 1

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”