The Segment Routing Architecture (IEEE Globecom 2015)
- 1. Nagendra Kumar Nainar Technical Leader, Cisco Dec 2015 The Segment Routing Architecture
- 2. • Clarence Filsfils • Nagendra Kumar Nainar • Carlos Pignataro • Juan Camilo Cardona • Pierre Francois Authors
- 3. Introduction
- 4. Network Architecture Evolution IP Forwarding MPLS ?? Strict SLA (Packet, jitter, delay) High Performance Converged N/w Application centric Network simplification Programm able network • IP header lookup • Shortest path forwarding • Lacks path control • Lacks Flexibility • Lacks Performance •Label lookup •Traffic Engineering •Flexible to accommodate services •Control Plane complexity •Scalability •Distributed Path computing • Flexible • Scalable • Simple to Operate
- 5. Segment Routing • Source Routing Source chooses a path and encodes it in the packet header as an ordered list of segments Rest of the network executes the encoded instructions without any further per- flow state • Segment Identifier for any type of instruction Forwarding or service • Control Plane Paradigm Distributed intelligence is used to build these segments Centralized intelligence maps application to path for resource optimization
- 6. Segment Routing • Very briefly, the objective is to support end-to-end per-flow policies in terms of Connectivity Resiliency Path preference (traffic engineering) Service selection
- 7. Segment Routing - Architecture
- 8. Segment Routing Components • Segment ID – Identifier for any type of instruction – Node wide or Domain wide Uniqueness • Data Plane – Encode the sequence of segment to be applied to packet – Associated forward semantic for the segment – MPLS and IPv6 • Control Plane – Distribution of segment among the devices in domain – Flow to Segment sequence mapping instruction
- 9. IGP Prefix Segment • Aka Node Segment ID • Shortest-path to the IGP prefix • Global • Signaled by ISIS/OSPF • Manually assigned or using centralized controller. 11 1 2 3 15 654 Illustration: Prefix-SID NodeX = 16000+X 16015 16015 payload 16015 payload
- 10. 11 1 2 3 15 654 24025 payload IGP Adjacency Segment • Forward on the IGP adjacency • Locally Assigned • Local significance • Signaled by ISIS/OSPF • Programmed only in originator’s forwarding table Illustration: Adj-SID XY = 24nXY, n is index 24023 2412524025 24021 24125 payload
- 11. Service Segment • Forward on the IGP adjacency • Locally Assigned • Local significance • Signaled by ISIS/OSPF • Programmed only in originator’s forwarding table Illustration: Service-SID X = 30000+X 30020 Firewall 20 11 1 2 3 15 654 30020 payload
- 12. SR Data Plane • Data Plane Forwarding actions: – CONTINUE: Forwarding action based on active segment – PUSH: Add segment to SR header – NEXT: Mark the next segment as “Active” Segment Routing MPLS Data Plane SR Header Label Stack Active Segment Topmost Label PUSH Label Push NEXT Label Pop CONTINUE Label Swap
- 13. SR Control Plane • Segment ID distribution – OSPF, ISIS • Flow to Segment sequence mapping instruction – Distributed CSPF – SDN Controller based approach – Operator defined • Controller collects via BGP-LS – IGP segments – BGP segments – Topology Ctrl BGP-LSBGP-LS 11 1 2 3 15 654
- 15. Traffic Engineering using SR Tunnels 11 1 14 2 3 15 654 1312 High BW High delay Low BW Low delay Ctrl Application or Controller triggered Flow mapping Instruction • Voice Traffic with low latency requirement uses {16002, 24125, 16013, 30021} • File Transfer Traffic with High BW requirement uses {16002, 24025, 16013, 30021} DPI 21 Voice Traffic File Transfer Illustration: Prefix-SID NodeX = 16000+X Adj-SID XY = 24nXY, n is index Service-SID X = 30000+X Low BW High delay 30021 Voice 16013 24125 16002 30021 File Data 16013 24125 16002
- 16. Service Function Chaining 11 1 14 2 3 15 654 1312 High BW High delay Low BW Low delay Ctrl • Traffic to be applied with Service Chain comprising FW and DPI uses {16014, 30020, 16013, 30021, 16015} 21 Traffic Illustration: Prefix-SID NodeX = 16000+X Adj-SID XY = 24nXY, n is index Service-SID X = 30000+XFirewall 20 Flow mapping Instruction DPI 16015 payload 30021 16013 30020 16014
- 17. Segment Routing OAM • OAM probe originates and terminates at Monitoring server. • OAM probe to validate path between 11 to 15 uses {16011, 16015, 16022} • Path validation performed with no control plane involvement 11 1 14 2 3 15 654 1312 Illustration: Prefix-SID NodeX = 16000+X Adj-SID XY = 24nXY, n is index Service-SID X = 30000+X Monitoring server 2216022 payload 16015 16011 16022 payload 16015 16022 payload
- 18. More details are available in below links: www.segment-routing.net www.segment-routing.net/home/tutorial www.linkedin.com/groups/Segment-Routing-8266623 Stay Informed
- 19. Thank you