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

[Greg Daley <[e-mail]>]

Hi Curtis, 

> -----Original Message-----
[my post chopped]
> 
> 
> Reality check time.
> 
> To get the PW over MPLS drafts past the TSV AD there is a SHOULD regarding
> congestion control.
> 
> AFAIK: No service providers ask for it.  No one implements it.  If they did
> implement it no one would deploy it.
> 
> PW over MPLS is generally carrying relatively low volumes of high priority
> traffic.  The TC bits (MPLS flavor of Diffserv DSCP) are used to enforce the
> higher priority.  If congestion occurs other traffic on that infrastructure
> (typically plain old Internet) sees loss.  That is intended.  This is the reality of
> how PW over MPLS is deployed.
> 
> Anyone who knows of implementation or deployment of congestion control for
> PW over MPLS can correct me.
> 
> I don't know about the "over GRE" or "over L2TP" tunneling.

Essentially, my point is that with traditional carriage environments there is an underlying medium which it may be possible to traffic engineer.
The value of a SHOULD is that it isn't necessary to there is a valid reason not to follow it (i.e. you control the medium and/or the ingress traffic flows and the traffic remains private).  The onus remains on the implementer and deployer not to mess up the Internet.

I think that similar guidance may be applicable in this case (as in GRE and L2TP encapsulations), where the next label switch could be across paths shared with other Internet traffic that has congestion avoidance, mitigation or control.

Sincerely, 

Greg Daley