4A0-116: Nokia Segment Routing Exam

An Adjacency-SID is locally significant and is allocated from local label space, such as an SRLB or dynamic label range, rather than from the SRGB. The SRGB is used for global segments such as Prefix-SIDs and Node-SIDs. Adjacency-SIDs can also be allocated automatically by the IGP.

An MPLS Label Switched Path (LSP) is a directed path through label switching routers. Bidirectional communication normally uses separate LSPs for each direction, rather than one inherently bi-directional MPLS tunnel. RFC 3031 defines an LSP as a sequence of routers followed by packets in a forwarding equivalence class.

A Node-SID can be configured as either an absolute MPLS label or an index. SRGB ranges are local to each router and therefore do not have to match across all routers. A Node-SID advertisement is not limited to cases where the Node-SID was configured as an index; the control plane provides the information needed to map the SID for the receiving router’s local SRGB.

Traffic engineering selects paths according to constraints such as available capacity, congestion avoidance, policy, and resiliency. The selected route may be longer than the shortest path when that better meets those requirements.

Administrative-group membership is encoded as a bitmask. The value 0x11 is binary 0001 0001, containing two set bits; therefore, the interface is a member of two distinct administrative groups. Cisco documents SR-TE affinity/admin-group mappings in terms of positions in an administrative-group bitmask.