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MPLS-TE Fault Tolerance
This document discusses MPLS-TE fast reroute (FRR) and fault tolerance techniques. It describes various types of network failures that can occur and the packet loss they cause. Several protection schemes are then outlined, including path protection, local protection, link protection and node protection. Local protection techniques like link and node protection provide fast failure recovery times and high scalability by pre-signaling backup label switched paths to avoid affected network elements. Label stacking is also discussed as a method for encapsulating traffic on backup LSPs. The document concludes that interior gateway protocols and TE headend rerouting are too slow for real-time applications, so FRR and local protection schemes are needed to minimize traffic loss during failures.
MPLS-TE Fault Tolerance
- 1. MPLS-TE Fault Tolerance MPLS-TEPROTECTION OR FAST REROUTE (FRR)
- 2. Network Failures • Nodefailures Hardware Failures Maintenance Electrical Problems • Link failures Loose Cables Fiber Cuts ADM Problems Packet Lost
- 3. Possible Solutions • InteriorGateway Protocol (IGP) • OSPF • IS-IS Convergence/Rapid Convergence Congestion SPF • SONET Automatic Protection Switching (APS) • Active Link • Passive/Standby Link ~50ms Delay between link changes IGP Convergence ADM Required Insufficient Fault Tolerance
- 4. Background • RFC 2702“Requirements for Traffic Engineering Over MPLS” • LSP reroute/Headend reroute New TE LSP (RSVP) Signaling SFP Substantial Traffic Lost Packet Lost MPLS-TE Protection or Fast Reroute (FRR)
- 5. Protection • Procedures • Resources •Physical • Links • Nodes • Logical • LSP Minimal Traffic Lost • Protection Preset LSP Backup Pre-computed Pre-signaled
- 6. Protection Schemes • PathProtection • End-to-End Protection • Local Protection • Link Protection • Node Protection
- 7. Path Protection • Backup/SecondaryLSP • Parallel to Primary LSP • Distinct route • Pre-signaled • BW properties similar to primary LSP Better Convergence vs. IGP & TE LSP reroute 1:1 Bit Scalable
- 8. Local Protection • BackupLSP for a segment of the primary LSP • Pre-signaled • Around the affected link (link protection) • Around the affected node (node protection) • Encapsulates primary LSP Fast Failure Recovery 1:N High Scalability
- 9. Label Stacking •12008a –12008c link failure •12008a switch traffic to backup LSP •12008a stack label 38 to 33, {38,33} •12008a switch to 12008b {38,33} •12008b relieve {38,33} & switch to 12008d based on high level label (38), replacing 38 by 35, {35,33} •12008d receive {35,33}, performs PHP removing 35 & switch to 12008c, {33} •12008c receive {33}, performs PHP & resend to 7200c• Required • Label Stacking • Global Label Space
- 10. Link Protection • BackupTunnel or LSP • Avoids "protected link" Protects against link failures. Vulnerable against node failures • NHop Tunnels • From PLR to NHop Node • PLR knows MP expected label
- 11. Node Protection • BackupTunnel or LSP • Avoids "protected node" • NNHop Tunnels • From PLR to NNHop • Label Recording required Protects against link and node failures
- 12. Advanced Methods ofProtection • Multiple backup tunnels • Backup BW Reservation • Promotion
- 13. Conclusions • IGP • MPLS-TEheadend reroute Slow and Insufficient • Real-time Applications • VoIP • Live Meeting • etc. • FRR • Local Protection
- 14. Bibliography • Traffic Engineeringwith MPLS, Eric Osborne CCIE #4122, Ajay Simha CCIE #2970, Cisco Press