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

[Joe Touch <[e-mail]>]

On 1/27/2014 11:19 AM, Joel M. Halpern wrote:
> Yes Joe, routers could ahve been built to do those calcualtions at that
> performance scale.
> There are however two major problems:
>
> 1) That is not how routers are built.
> 2) The target performance scale is rather higher.
>
> So could someone build an ASIC to do what you want?

Has. It's already part of nearly every DMA ASIC in a network interface 
already.

 > Probably.  Is there
> any reason in the world to expect operators to pay the significant extra
> cost for such?Not that I can see.

We're talking about a ring of full adders, the specs for which are given 
in an RFC that's 18 years old, and that is already implemented in nearly 
every host interface, including 10Gps NICs.

And we're talking about "routers", many variants of which operate at 
very high speeds and transparently proxy TCP already. So this is a 
solved problem.

> And even if we could and they would, that is not the world into which we
> are deploying these tunnels.

We're back to "that's not what they do now", at least in some devices.

Well, they don't use MPLS in UDP (since no spec exists), so clearly if 
they're limited to doing what they already do, this is an exercise in 
futility.

Joe

>
> Yours,
> Joel
>
> On 1/27/14 1:53 PM, Joe Touch wrote:
>>
>>
>> On 1/27/2014 10:48 AM, joel jaeggli wrote:
>>> On 1/27/14, 8:48 AM, Joe Touch wrote:
>>>> Those same mechanisms have provided hardware checksum support for a
>>>> very long time.
>>>
>>> The new header and the payload are actually in different parts of the
>>> forwarding complex until they hit the output queue, you can't checksum
>>> data you don't have.
>>
>> You can (and some do) the checksum component parts when things go into
>> memory; the partial sums can be added as the parts are combined in the
>> output queue.
>>
>> I appreciate that we're all taking about what might be done, but the
>> reality is that there are many 'transparent TCP proxies' that have to do
>> this, so there's clearly a solution, and it clearly runs fast enough.
>>
>> Joe
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