SRv6 SRH header Explained

SRv6 SRH header | Below article will explain SRH (Segment Routing header)

Segment Routing implementation can be IPv6 data plane using a new type of Routing Extension Header called the Segment Routing Header (SRH).We have discussed this in detail in my earlier Post at, 

Routing Headers are defined in RFC 8200. The Segment Routing has a Routing Type value 4 to be assigned to identify SR header. The Segment Routing Header (SRH) is defined as follows: 
SRH header
Few of the important fields in the SRH header are described below,
Segment listSegment list represent segment id (SID) which is 128 bit IPv6 address .The Segment list is encoded starting from the last segment of the SID list , means , the first element of the segment list (index 0) contains the last SID in the a list , the second element contains the penultimate segment in the  SID list and so on.

Each Segment id in the list is combination of locator & function as explained in the earlier Post.

Last Entry – It contains the index value of last element in the segment list.

Next header – It Identifies the header immediately following the routing header .

Routing Type – It identifies the particular routing header type , here in this case , value will be 4 , representing Segment Routing header.

Segments Left – It identifies number of explicitly listed intermediate nodes still to be visited before reaching the final destination.

TLVs – Optional TLVs are used to carry additional Meta-data information.

In the next Post we will discuss forwarding mechanism of SRv6 . I hope this article is useful .

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