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

[Stewart Bryant <[e-mail]>]

Sorry, are you talking the same h/w that does IP c/s?

That h/w can only see the IP header.

S


On 27/01/2014 16:48, Joe Touch wrote:
> Those same mechanisms have provided hardware checksum support for a very long time.
>
> Joe
>
>> On Jan 27, 2014, at 8:40 AM, Stewart Bryant <[e-mail]> 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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