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

[Stewart Bryant <[e-mail]>]

Yes, the inner (real) transport header is the only meaningful place
to apply congestion avoidance.

Stewart

On 14/01/2014 13:52, Scott Brim wrote:
> Now that I'm at a real keyboard, and since at least one person didn't
> get what I was trying to say with my reference, let me try to explain
> more clearly.
>
> Transport is pretty arcane. We sometimes get it more or less right
> when we're dealing with a single instance of it in endpoints and
> routers/switches. In this case, if we add congestion management to the
> encapsulating UDP, we have two possible instances of the same function
> stacked on top of each other, where each has no way of knowing whether
> the other exists, if so what it's doing, or if there's any way to
> communicate with it. We have examples in the past where we have got
> this badly wrong. IMHO this is more likely to be a problem than not.
>
> The best architectural answer I can think of in this case is the one
> with the least surprises built in: treat the lower level UDP as just
> an encapsulation, not an intelligent transport protocol. Yes there
> should be scope for congestion management but that is higher up, where
> the endpoints come in to play.
>
> Scott
>
> On Tue, Jan 14, 2014 at 8:11 AM, Scott Brim <[e-mail]> wrote:
>> On Jan 14, 2014 6:00 AM, "Stewart Bryant" <[e-mail]> wrote:
>>> On 13/01/2014 19:09, Scott Brim wrote:
>>>> On Mon, Jan 13, 2014 at 10:51 AM, Joel M. Halpern <[e-mail]>
>>>> wrote:
>>>> I'm concerned about TCP-over-X.25 scenarios.
>>> ... and how many b/s of that exist in the universe!
>> Stewart: none that I know of, of course, but it was in production at a
>> significant time in Internet history and was one of our first experiences
>> with multiple layers each trying to provide transport control and thereby
>> destroying goodput. I'll never forget it. When I think of two layers each
>> trying to do congestion management,  with no way to coordinate with each
>> other, that's the first example that comes to mind.
>>
>> Scott
> .
>


-- 
For corporate legal information go to:

http://www.cisco.com/web/about/doing_business/legal/cri/index.html