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3. SR Nodes

3. SR Nodes​

There are different types of nodes that may be involved in segment routing networks: SR source nodes that originate packets with a segment in the destination address of the IPv6 header, transit nodes that forward packets destined to a remote segment, and SR segment endpoint nodes that process a local segment in the destination address of an IPv6 header.

3.1. SR Source Node​

A SR source node is any node that originates an IPv6 packet with a segment (i.e., SRv6 SID) in the destination address of the IPv6 header. The packet leaving the SR source node may or may not contain an SRH. This includes either:

  • A host originating an IPv6 packet, or

  • An SR domain ingress router encapsulating a received packet in an outer IPv6 header, followed by an optional SRH.

It is out of the scope of this document to describe the mechanism through which a segment in the destination address of the IPv6 header and the Segment List in the SRH are derived.

3.2. Transit Node​

A transit node is any node forwarding an IPv6 packet where the destination address of that packet is not locally configured as a segment or a local interface. A transit node is not required to be capable of processing a segment or SRH.

3.3. SR Segment Endpoint Node​

An SR segment endpoint node is any node receiving an IPv6 packet where the destination address of that packet is locally configured as a segment or local interface.