Explains how SRv6-TE uses SIDs in the SRH to steer traffic through explicit or dynamically calculated paths and identifies its supported policy capabilities.
Segment Routing over IPv6 Traffic Engineering (SRv6-TE ) is a traffic engineering solution that
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enables you to steer traffic across a network based on specific policies and requirements and provides greater control over how traffic flows through the network
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allows you to create explicit paths through the network for specific traffic flows where a particular application or service requires a specific quality of service (QoS) level, such as low latency or high bandwidth, and
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leverages the concept of source routing, where the source node determines the path and encodes it in the packet header as a list of segments. This list of segments is added to an IPv6 routing header called the SRv6 Segment Routing Header (SRH) in the incoming packet.
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Feature Name |
Release Information |
Feature Description |
|---|---|---|
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SRv6 Traffic Engineering |
Release 25.4.1 |
Introduced in this release on: Fixed Systems (8700 [ASIC: K100], 8010 [ASIC: A100])(select variants only*) *This feature is supported on:
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SRv6 Traffic Engineering |
Release 25.1.1 |
Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*) *This feature is supported on Cisco 8011-4G24Y4H-I routers. |
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SRv6 Traffic Engineering |
Release 24.4.1 |
Introduced in this release on: Fixed Systems(8200, 8700);Modular Systems (8800 [LC ASIC: P100]) (select variants only*) *This feature is now supported on:
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SRv6 Traffic Engineering |
Release 7.10.1 |
You can now control the traffic flows within the network by defining the explicit and dynamic paths for traffic flows using the Segment Identifier (SID) within the IPv6 packet header. Defining explicit and dynamic paths based on different attributes and constraints allow the router to optimize routing decisions and enhance resource utilization. SRv6-TE policies supports the following functionalities:
This feature introduces the following changes: CLI: YANG Data Model:
(see GitHub, YANG Data Models Navigator) |
Why SRv6-TE is Essential for Modern Networks
SRv6-TE provides enhanced control and flexibility in steering traffic across a network based on specific policies and requirements. This solution eliminates the need for intermediate nodes to maintain per-application and per-flow state. Only the head-end nodes at the network edge maintain state, while the remaining nodes forward packets based on instructions encoded in the packet header. This source routing approach improves scalability and reduces complexity.
Key benefits of SRv6-TE include:
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Explicit traffic steering: Enables the creation of explicit paths for traffic flows that require specific Quality of Service (QoS) levels, such as low latency or high bandwidth.
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Source routing efficiency: The source node calculates and encodes the path directly in the packet header, which offloads path computation from intermediate routers.
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Optimized resource utilization: Utilizes network bandwidth more effectively than traditional MPLS RSVP-TE by leveraging Equal-Cost Multi-Path (ECMP) within each segment.
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Simplified network management: Embeds forwarding paths within packets, which reduces overhead and makes the network more responsive to changes.
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Support for advanced traffic engineering: Supports flexible algorithms and policies for intents like low latency, disjointness, affinity inclusion/exclusion, and Shared Risk Link Group (SRLG) exclusion, often with Path Computation Element (PCE) assistance.
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Seamless IPv6 integration: Leverages existing IPv6 infrastructure for easier deployment.
Comparison between SRv6-TE and MPLS RSVP-TE
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Feature |
SRv6-TE |
Traditional MPLS RSVP-TE |
|---|---|---|
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State Maintenance |
Only head-end nodes maintain state |
All nodes along the path maintain per-flow state |
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Routing Paradigm |
Source routing with path encoded in packet header. |
Signaling-based path setup with RSVP protocol. |
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Bandwidth Utilization |
More efficient via ECMP within segments |
Less efficient, limited ECMP usage |
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Traffic Engineering Flexibility |
Supports advanced policies including flexible algorithms and explicit paths. |
Supports explicit paths but with more overhead. |
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Integration |
Native IPv6-based, leverages IPv6 infrastructure |
MPLS-based, requires MPLS infrastructure |
Methods of traffic engineering with SRv6
Traffic engineering over SRv6 can be accomplished in these ways:
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End-to-End Flexible Algorithm: This is used for traffic engineering intents achieved with Flexible Algorithm, including low latency, multi-plane disjointness, affinity inclusion/exclusion, and SRLG exclusion. See SRv6 Flexible Algorithm.
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SRv6-TE Policy: This is used for traffic engineering intents beyond Flex Algo capabilities, such as path disjointness that rely on path computation by a PCE. In addition, this is used for user-configured explicit paths. See SRv6-TE Policy .