https://www.segmentroutingexpert.com/2020/03/segment-routing-data-plane.html

Segment Routing data plane can also be IPv6 using new type of extension header called SRH (Segment Routing Header). The IPv6 data plane implementation of Segment Routing is known as SRv6 . In SRv6 implementation  , segment is represented using IPv6 address , and segment list is encoded as an ordered list of IPv6 addresses in the SRH header.

SRH is standard track draft and you can refer to IETF link below to check details of SRH header

https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26

SRv6 implementation does not require MPLS and also, it further reduces some of overlay technologies like VXLAN, NSH (Network Service Header )  etc. We will discuss SRv6 , its use case and working principle  in subsequent articles . 

SRv6 is going to revolutionize packet forwarding behaviour as it can potentially span across all segments of network like Service Provider WAN, Data Center fabric ,Enterprise WAN and even to compute and applications. SRv6 further simplifies networking needs compare to SR-MPLS because SRv6 header carries all underlay and overlay services like VPN, Service Chaining , Traffic-engineering etc.

SRv6 benefits from inherent properties of IPv6 like hyper-scale , Hierarchical addressing and summarization.

SRv6 is Service programmable, lets be very clear what it means. It means, SRv6 not only provides the ability to encode destination address directly into each packet header, known as “Locator” but also, defines how the traffic should be treated either at destination node or in the path itself, this is achieved via Network Instruction in the IPv6 SRH header which is called as “Function”.

This forms the basis of SRv6 SID structure which is,

SID structure is  combination of locator and Function

– the  locator identifies the address of the Endpoint  
– the function signifies the treatment of the packet

Will discuss more on Locator and Function in next article.