What is SRLG shared risk link group

SRLG (Shared Risk Link Group) Explained in Detail

Within the realm of optical mesh networks and MPLS (Multiprotocol Label Switching) traffic engineering, SRLG stands for Shared Risk Link Group. It's a crucial concept for understanding how network failures can impact traffic flow.

Understanding Shared Risks:

• In an optical network, data travels through fiber optic cables.
• These cables can be bundled together within a single conduit or mounted on the same power/telephone pole (aerial).
• If a fault occurs in this shared conduit or pole, it can potentially damage multiple fiber optic cables simultaneously.

SRLG Groups Similar Risks:

• An SRLG is a collection of links within a network that share a common risk factor.
• This common risk factor is typically the physical infrastructure that houses the fiber optic cables.
• Links belonging to the same SRLG experience a higher likelihood of failing simultaneously due to a shared physical vulnerability.

Identifying SRLGs:

• Network operators identify SRLGs by analyzing the physical layout of their network infrastructure.
• This analysis considers factors like conduit placements, pole sharing, and any other situations where multiple fiber links are exposed to the same potential point of failure.

SRLG and Backup Paths:

• MPLS traffic engineering utilizes SRLG information for establishing reliable traffic paths.
• The goal is to avoid situations where both the primary and backup paths for a traffic flow are susceptible to failure due to belonging to the same SRLG.

MPLS Path Protection with SRLG:

There are two primary approaches to MPLS path protection that leverage SRLG information:

1. Constraint-Based Shortest Path First (CSPF):
   • When calculating the backup path (secondary LSP) for a traffic flow, the network routing algorithm (CSPF) considers the SRLG information.
   • It prioritizes paths that do not share any SRLGs with the primary path (disjoint paths). This ensures that a single physical incident wouldn't disrupt both the primary and backup paths.
2. Fast Reroute (FRR):
   • In some scenarios, finding a completely disjoint path might not be feasible.
   • FRR allows for faster rerouting mechanisms in case the primary path fails.
   • However, network operators might still configure FRR to prioritize paths with minimal overlap in SRLGs compared to the primary path.

Benefits of SRLGs:

• Enhanced Network Resilience: By understanding shared risks, network operators can design more robust traffic engineering strategies.
• Improved Traffic Flow Reliability: MPLS path protection with SRLG awareness helps prevent single points of failure from causing widespread service disruptions.
• Efficient Resource Utilization: While aiming for disjoint paths, SRLG information can still guide the selection of backup paths that minimize unnecessary resource detours.

Additional Notes:

• The specific implementation details of SRLG awareness might vary depending on the network equipment and software used.
• Some network devices might utilize explicit SRLG configuration, while others rely on automated SRLG discovery based on network topology analysis.

I hope this explanation clarifies the technical concept of SRLG (Shared Risk Link Group) and its significance in MPLS traffic engineering for enhancing network resilience.