Label Encoding Algorithm for MPLS Segment Routing

Rabah Guedrez*, Orange Laps Olivier Dugeon , Orange Labs

Samer Lahoud, IRISA/Rennes 1 University Géraldine Texier, IRISA/Telecom Bretagne

The 15th IEEE International Symposium on Network Computing and Applications (NCA 2016)

2 Orange Group restricted

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Agenda

Problem to solve

Encoding Algorithms

Conclusion

Segment Routing ?

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What is Segment Routing ?

It is not a NEW PROTOCOL

It is a new architecture that leverages the source routing paradigm

Can be implemented over two data planes (MPLS & IPv6)

Standardized by the IETF SPRING Working Group

Segment Routing

Choose your data plane

IPv6 MPLS

SR-IPv6 SR-MPLS

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A segment can represent a node, link ,etc

SIDs are interpreted by the forwarding plane as:

Node-SID: “forward the packet using the IGP shortest path”

Adj-SID: “forward the packet using a specific interface”.

:100

:8000

What is Segment Routing ?

SR-MPLS

SID is a 20 bit label

SR Paths are encoded as a stack of labels

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SR Strict Path Encoding (No stack optimization)

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Problem : Maximum Stack Depth (MSD)

Limitation

It is a physical limitation on the routers

The maximum number of labels a router can push onto the header of packet

Results: paths expressed with a label stack > MSD are unusable

=> a sub-optimal network utilization

Percentage of useable paths

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SR Paths Label Encoding Algorithm (SR-LEA)

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SR Paths Label Encoding Algorithm (SR-LEA)

5037

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SR-LEA with Global Adj-SIDs

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Simulation Results

Useable paths

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Simulation Results

Conclusion

The MSD limitation slows the deployment of Segment Routing

The proposed algorithms are proven to slacken the impact of the MSD limitation

Implementation

Quagga-SR an open source SR-MPLS implementation with Global Adj-SID

ELENAOR an SDN base implementation of the proposed algorithms

Thank You