The SPRING WG Chairs have noticed several recent discussions which wound
around to the question of whether specific information belongs in a
Destination Option Header (DOH) before the SHR, or belongs in an SRH
TLV. Clearly there are some pieces of information that are closely tied
to the SRH, such as SRH Authentication information, that belong in the
SRH TLV. The question is discussed here is about information that while
tied to the SRH hops is not tied to the SRH contents.
There seem to be two obvious answers, but we'd like to hear the WG
opinion, in particular to propose alternatives.
One obvious alternative would seem to be simply not to allow any
extension in the SRH that can be properly handled by a DoH, and does not
depend upon information in the SRH other than potentially the current
DA, which is in the IPv6 Destination Address field. This provides a
clear decision process for the working group, but some folks have argued
it is limiting or inefficient.
The next obvious choice would seem to be to allow any extension that can
be carried in a DOH to also be carried in an SRH TLV. This seems to lead
to a large number of SRH TLV definitions, complicating implementations
and adding limited value. It should also be noted for this evaluation
that RFC 8754 section 4.3.1.1 and section 4.3.1.1.1 make it clear that
processing TLVs at an SRv6 Hop is optional and subject to local
configuration.
Does the working group have any suggestions or opinions?
Thank you,
Joel, Jim, and Bruno
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