A Novel Mechanism for Resilient Routing Suksant Sae Lor , Raul Landa, - - PowerPoint PPT Presentation

Multi-Service Networks 2010, Cosener's House, Abingdon

A Novel Mechanism for Resilient Routing

Suksant Sae Lor, Raul Landa, and Miguel Rio {s.lor, r.landa, m.rio}@ee.ucl.ac.uk

Network & Services Research Laboratory Department of Electronic & Electrical Engineering University College London

Introduction & Motivation

• Network failures cause packet losses
• Re-convergence is not fast enough
• Existing approaches are not universal

S D Single failures? Dual failures? Link failures? Node failures? Multiple failures? Shared-risk link group? Speed of convergence: Packet loss rates: Sensitive applications can’t tolerate this!

Existing Resilient Mechanisms

• Loop-Free Alternates (LFAs)
• Not-via addresses
• Multiple Routing Configurations (MRC)
• Failure-Insensitive Routing (FIR)
• SafeGuard

Existing Resilient Mechanisms

• Loop-Free Alternates (LFAs)
• Not-via addresses
• Multiple Routing Configurations (MRC)
• Failure-Insensitive Routing (FIR)
• SafeGuard

Aim to solve only “SINGLE FAILURES”!

• Failure-Carrying Packets (FCP)

Existing Resilient Mechanisms

• Loop-Free Alternates (LFAs)
• Not-via addresses
• Multiple Routing Configurations (MRC)
• Failure-Insensitive Routing (FIR)
• SafeGuard

Aim to solve only “SINGLE FAILURES”!

• Failure-Carrying Packets (FCP)

Large overheads Difficult to implement

Packet Re-cycling (PR) Overview

• Handles any number of failures
• Pre-computed paths; hence, fast re-route
• No major modifications on current routing
• Minimal packet/memory overheads
• Shortest path routing under failure-free scenario
• Routing & cycle following in case of failures

Cellular Graph Embeddings

• Draw a network graph, G on a closed surface, S

A D G B E H C F

Cellular Graph Embeddings

• Minimum genus embedding: cellular cycle system

A D G B E H C F C1 C2 C3 C4

Cellular Graph Embeddings

• Each link is included in exactly 2 cycles

A D G B E H C F C1 C2 C3 C4 Main cycle Complementary Cycle

Packet Re-cycling (PR) Routing & Cycle Following

• Routing using normal routing table (no failures)

A D G B E H C F C1 C2 C3 C4

Packet Re-cycling (PR) Routing & Cycle Following

• Cycle following when a failure is encountered

A D G B E H C F C1 C2 C3 C4

Packet Re-cycling (PR) Routing & Cycle Following

• Only PR bit (1 bit) is used to handle single failures

A D G B E H C F C1 C2 C3 C4

• Forwarding loop without termination condition

Packet Re-cycling (PR) Routing & Cycle Following

A D G B E H C F C1 C2 C3 C4

• Terminates only if it is closer to the destination!

Packet Re-cycling (PR) Cycle Following Termination Condition

A D G B E H C F C1 C2 C3 C4 4 H 5 G 3 E 6 D 1 C 2 B 7 A

• No. of hops to F

Node

• G detects a failure, it performs cycle following

Packet Re-cycling (PR) Cycle Following Termination Condition

A D G B E H C F C1 C2 C3 C4 4 H 5 G 3 E 6 D 1 C 2 B 7 A

• No. of hops to F

From

• A detects a failure, its performs cycle following

Packet Re-cycling (PR) Cycle Following Termination Condition

A D G B E H C F C1 C2 C3 C4 4 H 5 G 3 E 6 D 1 C 2 B 7 A

• No. of hops to F

From

• B detects a failure, it performs routing

Packet Re-cycling (PR) Cycle Following Termination Condition

A D G B E H C F C1 C2 C3 C4 4 H 5 G 3 E 6 D 1 C 2 B 7 A

• No. of hops to F

From

Benefits

• Minimal overheads while providing full protection:

– Packet header

• 1 bit for single failure cases
• Order of log2(d), where d is the network diameter
• For d 7, pool 2 DSCP can be used

– Memory

• Additional column in the routing table
• Cycle following tables (no. of interfaces x 3)

Incurred Stretch

• Stretch: cost(re-routing path) / cost(shortest path)

Abilene with 1 failure cases Abilene with 4 failure cases (worst-case scenarios)

Conclusion

• Resilience is important
• Some applications cannot tolerate losses
• Most mechanisms handle only single failure cases
• PR provides a full-failure protection with minimal
• verheads

Thank you! Q & A