BGP-Based SPF IETF 96, Berlin. Keyur Patel, Cisco Acee Lindem, Cisco Derek Yeung, Cisco Abhay Roy, Cisco Venu Venugopal, Cisco

Transcription

1 BGP-Based SPF IETF 96, Berin Keyur Pate, Cisco Acee Lindem, Cisco Derek Yeung, Cisco Abhay Roy, Cisco Venu Venugopa, Cisco 1

2 Data Center Routing Routing Probem Space Routing scaing for Massivey Scaabe Data Centers (MSDCs) Support both traditiona and controerbased soutions Many MSDCs migrating towards ayer 3 ony soutions for simpified management 2

3 Advantages of BGP-Based Soution Robust and scaabe impementations exist Wide Acceptance minima earning curve Aready movement toward BGP as soe MSDC protoco as evidenced by Use BGP for Routing in Large-Scae Data Centers work in RTGWG Reiabe Transport Guaranteed In-order Deivery Incrementa Updates Incrementa Updates upon session restart No Fooding Lends itsef to mutipe peering modes incuding Route-Refectors and controers. 3

4 Advantages of BGP SPF over Traditiona BGP Distance Vector Nodes have compete view of topoogy Ony network faiures (e.g., ink) need be advertised vis-à-vis a routes impacted by faiure. Faster covergence Better scaing SPF ends itsef better to optima path seection in Route-Refector (RR) and controer topoogies. 4

5 BGP based Link-State Routing Buid on BGP LS Address Famiy to carry ink state information BGP Capabiity and BGP-LS Node attributed to assure compatibiity Mutipe Peering Modes BGP runs Dijkstra instead of Best Path 5

6 BGP-LS Usage Uses existing BGP-LS Encodings from RFC 7752 and subsequent drafts. Competey incrementa updates Considered new BGP-SPF Protoco-ID but this woud imit usage to SPF. It woud aow impicit poicy to prevent advertisement to peers that don t support BGP SPF. Node NLRI Carries a new BGP-LS node attribute to indicate BGP SPF capabiity and specify the agorithm Link NLRI Identifies inks with advertisement dependent on peering mode Dua stack advertisement of IPv6/IPv4 addresses Unnumbered interfaces use oca/remote identifier (so far no BGP extension for remote identifier discovery) Prefix NLRI Advertise connected prefixes or even prefixes imported from other AFs or protocos 6

7 BGP Capabiity New capabiity indicating support for the BGP-LS SPF computation Requires support for MP Address-Famiy Link-State Used to determine whether to incude ink in topoogy. 7

8 BGP Best-Path Next-Path and Path Attribute basicay aong for the ride for BGP Link-State Address Famiy anyway Need to be vaidated based on RFC 4271 error handing Decision Process Phases 1 and 2 repaced by SPF agorithm Decision Process Phase 3 may be shortcircuited since NLRI is unique per BGP speaker. Need to assure the most recent version of NLRI is aways used and re-advertised. More work required here. 8

9 BGP SPF Starting with greaty simpified SPF with P2P ony inks in singe area (i.e., SPT) Wi scae very we to many use cases. Coud support computation of LFAs, Segment Routing SIDs, and other IGP features. BGP-LS incudes necessary Link-State Link-State AF is dua-stack AF since both IPv4 and IPv6 addresses/prefixes advertised BGP-LS aso supports VPNs but SPF behavior not defined (at east not yet). Work needed to define interaction with existing unicast AFs. 9

10 Peering Modes BGP run on a inter-fabric connections Simiar to RTGWG BGP Data Center soution Assures a nodes in SPT support SPF capabiity May want to wait for End-of-RIB (RFC 4724) to advertise ink to avoid back hoes. BGP run between a inter-fabric BGP speakers Singe session when mutipe inks can be muti-hop. Links/Liveiness discovered outside BGP. 10

11 Peering Modes (Continued) BGP sessions with Route-Refector or controer hierarchy. Link discovery/iveiness detection outside of BGP. Less contro over avoiding inks unti new node has compete topoogy. Controer coud earn the expected topoogy through some other means and inject it. SPF Computation is distributed though. Simiar to Jupiter Rising: A Decade of Cos Topoogies and Centraized Contro in Googe s Datacenter Network 11

12 Next Steps More refinement of mechanisms Changes to Best-Path seection for Link-State Address Famiy Interactions with other Address Famiies Further discussion Coaboration 12