> we can reword the statement so to explain that there are places
> where mpls is not planned to be deployed while ipv6 is and it is
> preferred (by the network operators of such infrastructures) to
> extend ipv6 with sr rather than changing dataplane.
To me this paragraph above is the real justification for use of IPv6. (although
one could debate whether forwarding based on a not-yet-standardized new
extension header constitutes changing the dataplane).
This points to my main concern with
draft-martin-spring-segment-routing-ipv6-use-cases -- specifically that it
confuses some perfectly reasonable use cases for SPRING (which would be equally
valid with either MPLS or IPv6 implementation), with the choice of data plane.
Looking at draft-martin-spring-segment-routing-ipv6-use-cases in detail:
Section 2.1 ("IPv6 Segment Routing in the Home Network") does not seem too bad.
On the one hand as far as I know the MPLS data plane has not been deployed in
home networks -- although to be fair just how my digital cable box and my
digital telephone box talk with the network is a detail that I don't need to
know and in my role as a homeowner I don't want to know. Also the data speeds
needed in the home network might be slow enough that purely software forwarding
might be appropriate (at least for now).
Section 2.2 ("IPv6 Segment Routing in the Access Network") seems to me to be a
perfectly reasonable explanation for why SPRING is useful in the access
network, along with a statement along the lines of the paragraph above (that
some might just not want to use an MPLS data plane).
The same could be said for sections 2.3, 2.4 and 2.5, which contain perfectly
reasonable explanations for why SPRING might be useful in Data Centers, Content
Delivery Networks, and Core Networks. However, why the data centers, content
delivery networks, and core networks might want to use SPRING, and whether they
choose to use an MPLS forwarding plane or an IPv6 forwarding plane, seem like
independent issues. Given that a SPRING control plane should be able to work
just fine with either data plane, the choice of data plane might come down to
issues such as what products get built and what performance can be achieved at
what cost.
Ross
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