In one embodiment, a Segment Routing network node provides processing and network efficiencies in protecting Internet Protocol version 6 (IPv6) Segment Routing (SRv6) packets and functions using Security Segment Identifiers, which are included in Segment Lists of a Segment Routing Header of a SRv6 packet. The Security Segment Identifier provides, inter alia, origin authentication, integrity of information in one or more headers of the packet, and/or anti-replay protection. In one embodiment, a Security Segment Identifier includes a value determined based on a secured portion of the packet. A typically secured portion includes the Source and Destination Addresses, one or more Segment Identifiers in a Segment List and the Segments Left value. In one embodiment, the Destination Address and/or a Segment Identifier in the Segment List includes and an anti-replay value (e.g., sequence number or portion thereof) which is also in the secured portion of the packet.