Segments distributed by IGP are called IGP segments and those distributed by BGP are called BGP segments. There are two types of IGP segments ,
1. IGP Prefix Segment – It is distributed by either ISIS or OSPF . IGP prefix segment is associated with prefix advertised by IGP. It signify steer traffic along ECMP aware shortest path to the prefix associated with this segment. Prefix segment is fundamental building block of segment routing .Typically, Prefix segment is identified by Node-SID which is Global unique in the network , assigned to the loopback address of the node.
2. IGP Adjacency Segment – This type of segment is associated with unidirectional adjacency of IS-IS or OSPF. It signify to steer traffic out to link of the adjacency (ISIS or OSPF) of the segment . Traffic is always steered on the link regardless of shortest path routing. Adjacency segment is local significant to the node of the segment.
And there are two types of BGP segments,
3. BGP Prefix Segment – BGP prefix segment is associated with BGP prefixes , similar to IGP prefix segment associated with IGP prefixes. It signify steer traffic along the ECMP aware BGP multi-path to the prefix associated with this segment.
4. BGP Peer Segment – BGP peer segments are associated with BGP Peering session to a specific neighbour . BGP peer segments are applicable to both IBGP and EBGP.