I call breaking any middleware that does checksum validation a problem - and a 
big one


Andrew Alston


Internal All Employees

________________________________
From: Robert Raszuk <rob...@raszuk.net>
Sent: Monday, February 5, 2024 7:16:23 PM
To: Ron Bonica <rbon...@juniper.net>
Cc: Andrew Alston - IETF <andrew-i...@liquid.tech>; spring@ietf.org 
<spring@ietf.org>
Subject: Re: [spring] draft-ietf-spring-srv6-srh-compression

Hi Ron,

Is there a problem ?

If I read RFC8200 L4 checksum is computed by the packet originator and 
validated by the packet's ultimate receiver.

In all SPRING work to the best of my knowledge the vast majority of packets are 
only encapsulated by transit nodes.

Is there any formal mandate in any of the RFCs that an encapsulating node must 
mangle the inner packet's L4 checksum ? I don't think so but stand open to get 
my understanding corrected.

Cheers,
Robert






On Mon, Feb 5, 2024 at 5:04 PM Ron Bonica 
<rbonica=40juniper....@dmarc.ietf.org<mailto:40juniper....@dmarc.ietf.org>> 
wrote:
Folks,

Has anyone proposed a solution to the L4 checksum problem that Andrew talks 
about?

                                          Ron


Juniper Business Use Only

________________________________
From: spring <spring-boun...@ietf.org<mailto:spring-boun...@ietf.org>> on 
behalf of Andrew Alston - IETF 
<andrew-ietf=40liquid.t...@dmarc.ietf.org<mailto:40liquid.t...@dmarc.ietf.org>>
Sent: Monday, February 5, 2024 5:21 AM
To: spring@ietf.org<mailto:spring@ietf.org> 
<spring@ietf.org<mailto:spring@ietf.org>>
Subject: [spring] draft-ietf-spring-srv6-srh-compression


[External Email. Be cautious of content]


Hi All,



(In capacity as a contributor and wearing no other hats)



At this point I cannot support progression of this document until the issues 
around the L4 Checksum have been resolved.  It’s been clearly stated in other 
emails on the list that in certain circumstances the behavior described in this 
document break the L4 checksum as defined in RFC8200.  This requires an update 
to RFC8200 to fix it – and I’m not sure that spring can update 8200 absent the 
consent of 6man, which I’m not sure has been asked for, nor am I sure that a 
spring document can update something like 8200 in an area so fundamental as the 
checksum without a -BIS, which would have to be done via 6man.  The L4 checksum 
issue though is real – and it cannot simply be ignored.



I also have deep concerns that the compression document creates something that 
(in a similar way to SRv6) creates something that is completely non-conformant 
with RFC4291.  There are multiple references to this in draft-6man-sids, and 
should draft-6man-sids become an RFC I would argue that it should probably be a 
normative reference in this document – on the logic that this document relies 
on similar RFC4291 violations that srv6 itself does (and for the record, just 
because SRv6 itself violates RFC4291 as is clearly documented in 
draft-6man-sids – does not make it acceptable to do so in yet another draft 
without clear and unambiguously stating the deviations and ideally updating 
RFC4291 to allow for said deviations)



I believe these two issues alone are sufficient that to pass this document 
would create still further tensions about the relationship between SRv6 and 
IPv6 and lead to confusion.  As such – I believe these issues need to be 
adequately dealt with – and the solutions to them need to be approved by 6man 
as the working group that holds responsibility for ipv6 maintenance.



Thanks



Andrew Alston






Internal All Employees

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