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Traffic Engineering Using Segment Routing

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Santiago Alvarez discusses traffic engineering segment routing at Cisco Connect Toronto 2015.

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Traffic Engineering Using Segment Routing

  1. 1. Traffic Engineering using Segment Routing Santiago Álvarez
  2. 2. Thank you for attending Cisco Connect Toronto 2015, here are a few housekeeping notes to ensure we all enjoy the session today. §  Please ensure your cellphones / laptops are set on silent to ensure no one is disturbed during the session §  A power bar is available under each desk in case you need to charge your laptop (Labs only) House Keeping Notes
  3. 3. §  Technology Overview §  Use Cases §  A Closer Look to Control and Data Plane §  Traffic Engineering §  Conclusions Agenda
  4. 4. Technology Overview
  5. 5. §  Source Routing §  the source chooses a path and encodes it in the packet header as an ordered list of segments §  the rest of the network executes the encoded instructions without any further per-flow state §  Segment: an identifier for any type of instruction §  forwarding or service Segment Routing
  6. 6. §  Shortest-path to the IGP prefix §  Global §  16000 + Index §  Signaled by ISIS/OSPF IGP Prefix Segment DC (BGP-SR) 10 11 12 13 14 2 4 6 5 7 WAN (IGP-SR) 3 1 PEER 16005
  7. 7. §  Forward on the IGP adjacency §  Local §  1XY §  X is the “from” §  Y is the “to” §  Signaled by ISIS/OSPF IGP Adjacency Segment DC (BGP-SR) 10 11 12 13 14 2 4 6 5 7 WAN (IGP-SR) 3 1 PEER 124
  8. 8. §  Shortest-path to the BGP prefix §  Global §  16000 + Index §  Signaled by BGP BGP Prefix Segment DC (BGP-SR) 10 11 12 13 14 2 4 6 5 7 WAN (IGP-SR) 3 1 PEER 16001
  9. 9. §  Forward to the BGP peer §  Local §  1XY §  X is the “from” §  Y is the “to” §  Signaled by BGP-LS (topology information) to the controller BGP Peering Segment DC (BGP-SR) 10 11 12 13 14 2 6 7 WAN (IGP-SR) 3 1 PEER Low Lat, Low BW 4 5 High Lat, High BW 147
  10. 10. §  WAE collects via BGP-LS §  IGP segments §  BGP segments §  Topology WAN Controller DC (BGP-SR) 10 11 12 13 14 2 4 6 5 7 WAN (IGP-SR) 3 1 PEER Low Lat, Low BW BGP-LS BGP-LS BGP-LS
  11. 11. §  WAE computes that the green path can be encoded as §  16001 §  16002 §  124 §  147 §  WAE programs a single per-flow state to create an application- engineered end-to-end policy An end-to-end path as a list of segments DC (BGP-SR) 10 11 12 13 14 2 4 6 5 7 WAN (IGP-SR) 3 1 PEER Low Lat, Low BW 50 Default ISIS cost metric: 10 {16001, 16002, 124, 147} PCEP, Netconf, BGP
  12. 12. §  IETF standardization in SPRING working group §  Protocol extensions progressing in multiple groups §  IS-IS §  OSPF §  PCE §  IDR §  6MAN §  Broad vendor and customer support Segment Routing Standardization Sample IETF Documents Segment Routing Architecture (draft-ietf-spring-segment-routing) Problem Statement and Requirements (draft-ietf-spring-problem-statement) IPv6 SPRING Use Cases (draft-ietf-spring-ipv6-use-cases) Segment Routing Use Cases (draft-filsfils-spring-segment-routing-use-cases) Topology Independent Fast Reroute using Segment Routing (draft-francois-spring-segment-routing-ti-lfa) IS-IS Extensions for Segment Routing (draft-ietf-isis-segment-routing-extensions) OSPF Extensions for Segment Routing (draft-ietf-ospf-segment-routing-extensions) PCEP Extensions for Segment Routing (draft-ietf-pce-segment-routing) Close to 30 IETF drafts in progress
  13. 13. §  Platforms: ASR9000, CRS-1/CRS-3 (shipping) §  IS-IS IPv4 (shipping) §  Node/Adjacency SID advertisement §  LDP interworking (mapping server/client) §  Traffic protection (topology independent LFA link protection) §  OSPFv2 (shipping) §  Node SID advertisement §  Traffic protection (LFA) §  Upcoming §  IS-IS IPv6 §  IS-IS / OSPFv2 parity §  SR Traffic Engineering (manual provisioning and PCEP) §  OAM (Ping/Trace) Segment Routing Product Support
  14. 14. Use Cases
  15. 15. §  IGP only §  No LDP, no RSVP-TE §  ECMP IPv4/6 VPN/Service transport 1 2 3 4 6 5 7 Site1 Site2 pkt 16007 vpn pkt 16007 vpn pkt pkt vpn pkt
  16. 16. §  Seamless deployment Seamless interworking with LDP 1 2 3 4 6 5 7 Site1 Site2 pkt pkt vpn pkt pkt 16007 vpn pkt 16007 vpn pkt vpn LDP(7)
  17. 17. §  50msec FRR in any topology §  IGP Automated §  No LDP, no RSVP-TE §  Optimum §  Post-convergence path §  No midpoint backup state §  Detailed operator report §  S. Litkowski, B. Decraene, Orange §  Mate Design §  How many backup segments §  Capacity analysis Topology-Independent LFA (TI-LFA FRR) 1 2 3 4 6 5 7 pkt 16007 16005 pkt 16007 pkt 16007
  18. 18. §  Traffic Matrix is fundamental for §  capacity planning §  centralized traffic engineering §  IP/Optical optimization §  Most operators do not have an accurate traffic matrix §  With SR, the traffic matrix collection is automated Automated Traffic Matrix Collection 1 2 3 4 1 2 3 4 1 2 4 3
  19. 19. §  On a per-content, per-user basis, the content delivery application can engineer §  the path within the AS §  the selected border router §  the selected peer §  Also applicable for engineering egress traffic from DC to peer §  BGP Prefix and Peering Segments Optimized Content Delivery 1 2 6 4 3 AS1 5 7 AS6AS5 AS7 pkt 16003 16002 126
  20. 20. §  Per-application flow engineering §  End-to-End §  DC, WAN, AGG, PEER §  Millions of flows §  No signaling §  No midpoint state §  No reclassification at boundaries Application Engineered Routing DC (or AGG) 10 11 12 13 14 Push {16001, 200, 147} Low-Latency to 7 for application A12 2 4 6 5 7 Default ISIS cost metric: 10 Default Latency metric: 10 ISIS: 35 WAN 3 1 BSID: 200 200: pop and push {16002, 16004} PEER Low Lat, Low BW Low-Lat to 4 PeerSID: 147, Low Lat, Low BW PeerSID: 147, High Lat, High BW
  21. 21. §  Per-application flow engineering §  End-to-End §  DC, WAN, AGG, PEER §  Millions of flows §  No signaling §  No midpoint state §  No reclassification at boundaries Application Engineered Routing DC (or AGG) 10 11 12 13 14 Push {16010, 16001, 200, 147} Low-Latency to 7, DC Plane 0 only, for application A12 2 4 6 5 7 Default ISIS cost metric: 10 Default Latency metric: 10 ISIS: 35 WAN 3 1 BSID: 200 200: pop and push {16002, 16004} PEER Low Lat, Low BW Low-Lat to 4 PeerSID: 147, Low Lat, Low BW PeerSID: 147, High Lat, High BW
  22. 22. A Closer Look to Control and Data Plane
  23. 23. MPLS Control and Forwarding Operation with Segment Routing PE1 PE2 IGPPE1 PE2 Services IPv4 IPv6 IPv4 VPN IPv6 VPN VPWS VPLS Packet Transport LDP MPLS Forwarding RSVP BGP Static IS-IS OSPF No changes to control or forwarding plane IGP label distribution for IPv4 and IPv6, same forwarding plane BGP / LDP
  24. 24. §  Prefix SID §  SID encoded as an index §  Index represents an offset from SRGB base §  Index globally unique §  SRGB may vary across LSRs §  SRGB (base and range) advertised with router capabilities §  Adjacency SID §  SID encoded as absolute (i.e. not indexed) value §  Locally significant §  Automatically allocated for each adjacency SID Encoding SRGB = [ 16000 - 23999 ]. Advertised as base = 16,000, range = 7,999 Prefix SID = 16041. Advertised as Prefix SID Index = 41 Adjacency SID = 24000. Advertised as Adjacency SID = 24000 SR-enabled Node
  25. 25. §  Level 1, level 2 and multi-level routing §  Prefix Segment ID (Prefix-SID) for host prefixes on loopback interfaces §  Adjacency SIDs for adjacencies §  Prefix-to-SID mapping advertisements (mapping server) §  MPLS penultimate hop popping (PHP) signaling §  MPLS explicit-null label signaling SR IS-IS Control Plane Overview
  26. 26. §  Required §  Wide metrics §  SR enabled under unicast address family §  Optional §  Prefix-SID configured under loopback(s) AF IPv4 §  MPLS forwarding enabled automatically on all (non-passive) IS-IS interfaces §  Adjacency-SIDs are automatically allocated for each adjacency IS-IS Configuration
  27. 27. §  IPv4 Prefix Segment ID (Prefix-SID) for host prefixes on loopback interfaces §  MPLS penultimate hop popping (PHP) signaling §  MPLS explicit-null label signaling SR OSPF Control Plane Overview
  28. 28. §  OSPFv2 control plane §  Required §  Enable segment-routing under instance or area(s) §  Command has area scope, usual inheritance applies §  Enable segment-routing forwarding under instance, area(s) or interface(s) §  Command has interface scope, usual inheritance applies §  Optional §  Prefix-SID configured under loopback(s) §  MPLS forwarding enabled on all OSPF interfaces with segment-routing forwarding configured OSPF Configuration
  29. 29. §  Packet forwarded along IGP shortest path §  Packet leverages ECMP load balancing §  Swap operation performed on input label §  Same top label if same/similar SRGB §  PHP if signaled by egress LSR MPLS Data Plane Operation Payload SRGB [16,000 – 23,999 ] X Payload Swap Y Payload SRGB [16,000 – 23,999 ] Y Payload Pop Y Adjacency SID = X X Prefix SID Adjacency SID §  Packet forwarded along IGP adjacency §  Pop operation performed on input label §  Top labels will likely differ §  Penultimate hop always pops last adjacency SID
  30. 30. Payload VPN Label MPLS Data Plane Operation (Prefix SID) SRGB [16,000 – 23,999 ] SRGB [16,000 – 23,999 ] SRGB [26,000 – 23,999 ] SRGB [16,000 – 23,999 ] Loopback X.X.X.X Prefix SID Index = 41 A B C D Payload 16041 Payload Push Push Swap Pop Payload Payload VPN Label 26041 VPN Label Pop
  31. 31. Payload VPN Label MPLS Data Plane Operation (Adjacency SIDs) MPLS Label Range [ 24000– 265535 ] MPLS Label Range [ 24000– 265535 ] MPLS Label Range [ 24000– 265535 ] MPLS Label Range [ 24000– 265535 ] Payload 24000 Payload Push Push Push Pop Pop Payload Payload VPN Label 24000 VPN Label Pop Adjacency SID = 24000Adjacency SID = 24000Adjacency SID = 24010 24000 A B C D
  32. 32. §  LFIB populated by IGP (ISIS / OSPF) §  Forwarding table remains constant (Nodes + Adjacencies) regardless of number of paths §  Other protocols (LDP, RSVP, BGP) can still program LFIB MPLS LFIB with Segment Routing PE PE PE PE PE PE PE PE P In Label Out Label Out Interface L1 L1 Intf1 L2 L2 Intf1 … … … L8 L8 Intf4 L9 L9 Intf2 L10 Pop Intf2 … … … Ln Pop Intf5 Network Node Segment Ids Node Adjacency Segment Ids Forwarding table remains constant
  33. 33. Traffic Engineering
  34. 34. §  Provides explicit routing §  Supports constraint-based routing §  Supports centralized admission control §  No RSVP-TE to establish LSPs §  Uses existing ISIS / OSPF extensions to advertise link attributes §  Provides ECMP Traffic Engineering with Segment Routing TE LSP Segment Routing
  35. 35. §  Link information Distribution §  ISIS-TE §  OSPF-TE §  Path Calculation §  Path Setup §  Forwarding Traffic down path §  Auto-route (announce / destinations) §  Static route §  PBR §  PBTS / CBTS §  Forwarding Adjacency §  Pseudowire Tunnel select How Traffic Engineering Works IP/MPLS Head end Mid-point Tail end TE LSP
  36. 36. §  Addresses complex requirements for path computation in large, multi-domain and multi-layer networks §  Path computation element (PCE) §  Computes network paths based on network information (topology, paths, etc.) §  Stores TE topology database (synchronized with network) §  May reside on a network node or on out-of-network server §  May initiate path creation §  Stateful - stores path database included resources used (synchronized with network) §  Stateless - no knowledge of previously established paths §  Path computation client (PCC) §  May send path computation requests to PCE §  May send path state updates to PCE §  PCC and PCE communicate via Path Computation Element Protocol (PCEP) §  Cisco WAN orchestration provides network path instantiation driven by an out-of-network stateful PCE PCE Architecture Introduction H E L L O my name is PCE
  37. 37. §  PCE maintains topology and path database (established paths) §  More optimal centralized path computation §  Enables centralized path initiation and update control §  Well suited for SDN deployments Stateful PCE PCEP Stateful PCE TED LSP DB PCC
  38. 38. §  An external PCE requires some form of topology acquisition §  A PCE may learn topology using BGP- LS, IGP, SNMP, etc. §  BGP-LS characteristics §  aggregates topology across one or more domains §  provides familiar operational model §  New BGP-LS attribute TLVs for SR §  IGP: links, nodes, prefixes §  BGP: peer node, peer adjacency, peer set Topology Acquisition Domain 1 Domain 2 Domain 0 BGP-LS TED BGP-LS BGP-LS RR PCE
  39. 39. §  PCC or PCE may initiate path setup §  PCC may delegate update control to PCE §  PCC may revoke delegation §  PCE may return delegation Active Stateful PCE PCEP Active Stateful PCE TED LSP DB Stateful PCC PCE has update control over delegated paths
  40. 40. Active Stateful PCE PCE-Initiated and PCC-Initiated LSPs PCEP PCC-Initiated (Active Stateful PCE) TED LSP DB Stateful PCC PCEP PCE-Initiated (Active Stateful PCE) TED LSP DB Stateful PCC PCC initiates LSP and delegates update control PCE initiates LSP and maintains update control §  PCE part of controller architecture managing full path life cycle §  Tighter integration with application demands §  PCC may initiate path setup based on distributed network state §  Can be used in conjunction with PCE- initiated paths
  41. 41. §  Segment routing enables source routing based on segment ids distributed by IGP §  PCE specifies path as list of segment ids §  PCC forwards traffic by pushing segment id list on packets §  No path signaling required §  Minimal forwarding state §  Maximum network forwarding virtualization §  The state is no longer in the network but in the packet §  Paths may be PCE- or PCC-initiated PCE Extensions for Segment Routing (SR) PCEP Segment List:: 10,20,30,40 Stateful PCE TED LSP DB Stateful PCC Node SID Adjacency SID Forwarding table remains constant In Out Int L1 L1 Intf1 … … … L7 L7 Int3 L8 Pop Intf3 … … … L9 Pop Intf5 Application Path Request
  42. 42. §  Segment Routing capability (when opening PCEP session) §  Existing ERO object with new Segment Routing Explicit Route Object (SR-ERO) sub-object §  Sub-objects include a segment id (SID) and/or an associated “Node or Adjacency Identifier”(NAI) §  A NAI can specify a §  IPv4 node §  IPv6 node §  IPv4 adjacency §  IPv6 adjacency §  Unnumbered adjacency with IPv4 node ids §  Request parameters indicate path type (SR or RSVP) PCEP Extensions for Segment Routing SID / NAI SID / NAI SID / NAI SR-ERO subobject (1) SR-ERO subobject (2) SR-ERO subobject (n) ERO Object
  43. 43. Conclusions
  44. 44. §  Minimal midpoint forwarding state required §  No extra protocol (LDP or RSVP-TE) required to signal path §  Native ECMP §  Few segments required (apply Cisco Mate Design on your data) §  Distributed computation or centralized §  Integration with IP/Optical optimization Conclusions
  45. 45. §  Cisco dCloud is a self-service platform that can be accessed via a browser, a high-speed Internet connection, and a cisco.com account §  Customers will have direct access to a subset of dCloud demos and labs §  Restricted content must be brokered by an authorized user (Cisco or Partner) and then shared with the customers (cisco.com user). §  Go to dcloud.cisco.com, select the location closest to you, and log in with your cisco.com credentials §  Review the getting started videos and try Cisco dCloud today: https://dcloud-cms.cisco.com/help dCloud Customers now get full dCloud experience!
  46. 46. §  Give us your feedback and you could win a Plantronics headset. Complete the session survey on your Cisco Connect Toronto Mobile app at the end of your session for a chance to win §  Winners will be announced and posted at the Information desk and on Twitter at the end of the day (You must be present to win!) Complete your session evaluation – May 14th
  47. 47. #CiscoSpark Let’s continue this conversation on… Spark Cisco’s mobile collaboration team application Visit the Collaboration booth in the World of Solutions to join the Connect Spark room
  48. 48. Thank you

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