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Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard

<l.wood@surrey.ac.uk> Mon, 27 January 2014 23:18 UTC

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From: l.wood@surrey.ac.uk
To: touch@isi.edu, stbryant@cisco.com
Date: Mon, 27 Jan 2014 23:17:24 +0000
Thread-Topic: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard
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References: <201401240320.s0O3KsR9013700@maildrop2.v6ds.occnc.com> <52E2BBC0.2030203@isi.edu> <52E68C12.2050308@cisco.com>, <98034F7E-47CF-4ABE-A199-A9DB4DACBC2E@isi.edu>
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Cc: mpls@ietf.org, ietf@ietf.org
Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard
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...and UDP Lite just covering the L3 and L4 headers, but not the full payload a la UDP,
 is still possible when the full payload is not visible.

Lloyd Wood
http://about.me/lloydwood
________________________________________
From: ietf [ietf-bounces@ietf.org] On Behalf Of Joe Touch [touch@isi.edu]
Sent: 27 January 2014 16:48
To: stbryant@cisco.com
Cc: mpls@ietf.org; IETF discussion list; curtis@ipv6.occnc.com
Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard

Those same mechanisms have provided hardware checksum support for a very long time.

Joe

> On Jan 27, 2014, at 8:40 AM, Stewart Bryant <stbryant@cisco.com> wrote:
>
>> On 24/01/2014 19:15, Joe Touch wrote:
>>
>>> This eliminates the "expands the reach of MPLS argument".
>>>
>>> First UDP checksums:
>>>
>>>   The UDP checksum is at the beginning of the payload.  Please see
>>> http://www.ietf.org/mail-archive/web/mpls/current/msg11279.html
>>>   This makes filling in a new UDP checksum infeasible on most high end
>>>   hardware.
>>
>> That argument would make sense if most hardware wasn't store-and-forward on a per-packet basis.
> They may be store and forward, but most of the high end designs
> use multiple grades of memory putting the packet in "slow memory"
> and providing a snapshot of the header in "fast memory" to the
> forwarder. Thus although the whole packet is in the system, it
> it is not accessible to the engine that would need to calculate the
> c/s.
>
> Stewart

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