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

[Joe Touch <[e-mail]>]

On 1/22/2014 9:55 AM, Eggert, Lars wrote:
> Hi,
>
> On 2014-1-22, at 18:29, Noel Chiappa <[e-mail]> wrote:
>> Envision the following 4 (or more) scenarios for one Border Tunneling Routing
>> (BTR), BTR A, to send packets to another BTR, BTR B, on the path from ultimate
>> source S (somewhere before BTR A) to destination D (somewhere after BTR B).
>>
>> - Plain IP
>> - Some existing encapsulation like GRE
>> - A new, custom encapsulation
>> - Encapsulation using UDP
>>
>> What you seem to be claiming is that in case 4 we need to have congestion
>> detection and response at the intermediate forwarding node BTR A - but it
>> would not be required in cases 1-3? This makes no sense.

FWIW, the whole point of using UDP is to leverage the Internet's ability 
to interpret the tunneled traffic as application data - to manage it 
according to port-based flow interpretation.

There's a cost associated with that privilege - the cost of needing to 
react to congestion. That doesn't require 1-RTT, TCP-friendly dynamic 
congestion control; it does mean *reacting* to congestion in some way, 
over some timescale more than just ignoring things.

This should be expected of any tunneling system that encapsulates 
non-reactive flows - regardless of technology.

Joe