IP and Optical Networks
IP and optical networks in this exam test converged design: segment routing, Flex-Algo, path computation, and cross-layer visibility between Nokia SR OS routers and optical transport.
Core rules
- SR-MPLS uses prefix and adjacency SIDs; SRv6 uses IPv6 segments. Both can steer traffic without RSVP-TE state.
- Flex-Algo lets IS-IS compute constrained topologies such as low latency or high bandwidth using advertised attributes.
- BGP-LS exports topology to a PCE; the PCE computes SR policies.
- Cross-layer design aligns router ports with optical wavelengths and uses optical protection or restoration for fiber faults.
Worked example
An operator wants low-latency traffic to avoid a congested link. Define Flex-Algo 128 with a latency metric, enable it in IS-IS on participating routers, and advertise the links' delay. BGP-LS sends the topology to the PCE, which computes an SR policy with a segment list. Verify that the policy's candidate path is active and that the forwarding entries use the expected SID stack.
Traps
Do not confuse prefix SID with adjacency SID. Do not assume Flex-Algo overrides IGP reachability; it selects a constrained topology. Do not forget that optical restoration time differs from router convergence time.