Segment Routing (SRv6)
The Future of Simplified Source Routing
The Paradigm Shift: Source Routing
Imagine you are going on a road trip.Traditional Routing is like driving and stopping at every intersection to ask a local for directions.Segment Routing is like having a GPS that prints a list of instructions on your windshield before you leave: "Turn right at Node A, then left at Node B."
SRv6 Packet Structure
Unlike SR-MPLS, which uses a stack of labels, SRv6 uses the IPv6 Routing Header.
- Segment List: An array of IPv6 SIDs representing the desired path.
- Segments Left: A pointer that moves through the list as the packet traverses the network.
SRv6 Network Programming
Watch how SIDs guide a packet using IPv6 Extension Headers.
Operational Insight
Ingress router encapsulates IP packet in SRv6 header. Destination Address (DA) is set to the first Segment ID (SID).
Why SRv6? (Eliminating Complexity)
- No LDP/RSVP: Eliminates two of the most complex protocols in the SP core.
- TI-LFA (Topology Independent Loop-Free Alternate): Provides guaranteed <50ms protection against link failures for any topology.
- Service Chaining: Allows you to force traffic through specific security or optimization services just by adding their SIDs to the list.
- Slicing: Enables "Network Slices" where high-priority traffic takes a low-latency path, while bulk data takes a cheaper, high-bandwidth path.
Conclusion
SRv6 is more than a routing protocol; it is a Network OS. It treats the entire global network as a single programmable entity, allowing for traffic engineering and service delivery that was previously impossible or prohibitively complex.