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

[Gregory Mirsky <[e-mail]>]

Hi Lars,
I think that " The whole point of running MPLS is to create networks in which paths are provisionable, so this is usually not an issue." is only partially correct. LDP-based MPLS network is not provisionable and LSPs follow IP best route selection. Explicit signaling of LSP is achievable in (G)MPLS by using RSVP(-TE) signaling.

	Regards,
		Greg

-----Original Message-----
From: mpls [mailto:[e-mail]] On Behalf Of Eggert, Lars
Sent: Friday, January 10, 2014 8:10 AM
To: Joel Halpern
Cc: [e-mail]; IETF
Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard

Hi,

On 2014-1-10, at 16:36, Joel M. Halpern <[e-mail]> wrote:
> Maybe I am completely missing things, but this looks wrong.
> If the MPLS LSP is carrying fixed rate pseudo-wires, adding congestion 
> control will make it more likely that the service won't work.  Is that 
> really the goal?
> 
> We do not perform congestion control on MPLS LSPs.
> Assuming that a UDP tunnel is carrying just MPLS and was established 
> just for MPLS, why would we expect it to behave differently than an 
> MPLS LSP running over the exact same path, carrying the exact same traffic?

we've been rehashing this discussion several times over the years, e.g., for PWE, AMT, etc. In order to carry fixed-rate or otherwise non-congestion-controlled traffic over unprovisioned general Internet paths, there needs to be some sort of basic congestion control mechanism, like a circuit breaker.

The whole point of running MPLS is to create networks in which paths are provisionable, so this is usually not an issue. But if you start sticking MPLS inside of UDP, those packets can go anywhere on the net, so you need mechanisms to control the rate of that traffic if it causes congestion, or at the very least you need to be able to stop the traffic if it creates severe congestion.

Lars