Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Fernando Gont <fgont@si6networks.com> Thu, 28 May 2020 13:10 UTC

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Subject: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH
To: "Ketan Talaulikar (ketant)" <ketant=40cisco.com@dmarc.ietf.org>, Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>, "Joel M. Halpern" <jmh@joelhalpern.com>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Thu, 28 May 2020 09:47:06 -0300
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On 28/5/20 08:46, Ketan Talaulikar (ketant) wrote:
[...]
> 
> Some of the operators may not care about the SR name, but it is clear to 
> me that the proposal in the CRH draft is a subset of Segment Routing 
> (i.e. a reduced portion of Spring Architecture) 

I find it kind of amusing when folks suggest that source routing routing 
is a spring or segment-routing thing, when all IPv4, CLNP, and IPv6 
(with RHT0) have supported some for of it for *ages*, and all predate 
segment routing and the work of Spring wg.

CRH seems to me as a variant of RHT0, where rather than employing 
128-bit addresses, they employ labels that are indirectly mapped to 
addresses, thus reducing the overhead in the packets themselves. With 
the obvious consequence that you need intermediate systems to support 
CRH (since otherwise you wouldn't be able to map the ID/label into an 
actual IPv6 address).

The above comment is meant neither in favor nor against CRH, but rather 
a reminder that source routing existed well before Spring, RFC8754, and 
others, and, as a result, well before Spring monopoly on routing headers 
(?) was declared.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492