Le 2024-04-05 à 16:30, Tom Herbert a écrit :
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On Fri, Apr 5, 2024, 8:53 AM Antoine FRESSANCOURT
<antoine.fressancourt=40huawei....@dmarc.ietf.org
<mailto:40huawei....@dmarc.ietf.org>> wrote:
Hello,
After reading RFC 8754 and RFC 8986 together with the draft (version
14), it seems to me that the cases when the SRH will be omitted are
quite limited, and will happen among nodes sharing the same locator
block. We can assume that, in such cases, nodes exchanging packets
carrying a C-SID without SRH will be managed by a single entity and
that this entity can check whether some middlebox infer with packet
relaying.
Antoine,
If it's such a limited use case then I have to ask if it's worth the
effort to make this a robust protocol? All we really need is a
deterministic way to distinguish SR packets from non-SR packets, which
could be accomplished by a minimum sized eight byte SRH. In other words,
it seems like this discussion is only about saving eight bytes on the
wire for a narrow use case.
Tom
considering an earlier message from Francois:
---
Specifically for the case of middleboxes attempting to verify the
upper-layer checksum,
An SRv6-unaware middlebox will not be able to verify the
upper-layer checksum of SRv6 packets in flight, regardless of whether an
SRH is present or not.
An SRv6 and C-SID aware middlebox will be able to find the ultimate
DA and verify the upper-layer checksum in flight, regardless of whether
an SRH is present or not.
---
I'm not sure to understand the value of an SRH to distinguish SR packets
from non-SR packets.
-m
Tom
Then we could modify the text to mention that, if such an inference
is detected, the packet should use a SRH. In my view, being clear
about potential issue related with omitting the SRH and giving an
alternative is enough, and gives some freedom to people willing to
use C-SID without SRH in their context.
Best regards,
Antoine Fressancourt
-----Original Message-----
From: spring <spring-boun...@ietf.org
<mailto:spring-boun...@ietf.org>> On Behalf Of Alvaro Retana
Sent: jeudi 28 mars 2024 13:06
To: SPRING WG List <spring@ietf.org <mailto:spring@ietf.org>>
Cc: 6man <i...@ietf.org <mailto:i...@ietf.org>>;
spring-cha...@ietf.org <mailto:spring-cha...@ietf.org>
Subject: [spring] Subject: Mandating SRH when using C-SIDs
(draft-ietf-spring-srv6-srh-compression)
Focusing on the C-SID draft, some have suggested requiring the
presence of the SRH whenever C-SIDs are used. Please discuss whether
that is the desired behavior (or not) -- please be specific when
debating the benefits or consequences of either behavior.
Please keep the related (but independent) discussion of requiring
the SRH whenever SRv6 is used separate. This larger topic may impact
several documents and is better handled in a different thread (with
6man and spring included).
Thanks!
Alvaro
-- for spring-chairs
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