Network Services Header Context Allocation Identifier
Praveen Mulay, Gunter Van de Velde, Martin Vigoureux · 2016
The specification of the NSH 1 header [draft-ietf-sfc-nsh] mandates four Context Headers, 4-byte each, and they MUST be added immediately following the Service Path Header. As direct consequence, an NSH 1 header is always Length 0x6 (six 4-byte words). As a result, the Length field of the NSH 1 header provides an information which is known by simply looking at the MD Type field. However, while [draft-ietf-sfc-nsh] does not specify the encoding of these Context Headers, other specifications have started to do so. A need to distinguish types of Context Headers therefore arises. This draft proposes to overload the Length field of an NSH 1 as Meta-Data context allocation identifier and to create a IANA repository for NSH 1 allocation schemes. The NSH 1 Length field overload intends to allow universal understanding at any network location and by any network device of the context allocation structure.