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Re: [spring] L4 Checksum and draft-ietf-6man-segment-routing-header

"Stefano Previdi (sprevidi)" <sprevidi@cisco.com> Mon, 16 May 2016 08:58 UTC

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From: "Stefano Previdi (sprevidi)" <sprevidi@cisco.com>
To: Ole Trøan <otroan@employees.org>, Tal Mizrahi <talmi@marvell.com>
Subject: Re: [spring] L4 Checksum and draft-ietf-6man-segment-routing-header
Thread-Topic: [spring] L4 Checksum and draft-ietf-6man-segment-routing-header
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Date: Mon, 16 May 2016 08:58:53 +0000
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Cc: "spring@ietf.org" <spring@ietf.org>, 6man WG <ipv6@ietf.org>, "draft-ietf-6man-segment-routing-header@tools.ietf.org" <draft-ietf-6man-segment-routing-header@tools.ietf.org>
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> On May 15, 2016, at 8:06 PM, otroan@employees.org wrote:
> 
> Tal,
> 
>> [Apologies if this issue has been discussed before.]
>> 
>> According to draft-ietf-6man-segment-routing-header, an ‘SR Segment Endpoint Node’ updates the Destination IP address.
>> Therefore, it must also update the Layer 4 Checksum, right?
>> 
>> I wonder if there is an upper bound on the size of the SRH. Otherwise, the L4 Checksum may be located in a pretty deep location.
>> Speaking from a chip vendor’s perspective this may be a problem.
> 
> From RFC2460, RH0:
> 
> 
>      o  If the IPv6 packet contains a Routing header, the Destination
>         Address used in the pseudo-header is that of the final
>         destination.  At the originating node, that address will be in
>         the last element of the Routing header; at the recipient(s),
>         that address will be in the Destination Address field of the
>         IPv6 header.
> 
> I would expect SR would work the same.


exactly.

Moreover, draft-ietf-6man-segment-routing-header assumes encapsulation so clearly there’s no L4 involved here.

s.


> 
> Cheers,
> Ole
>

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