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

2014-01-16 16:32:46
These tunnels are stateless

yep. (But they don't have to be.)

The tunnels strictly speaking do not have to be stateless. However, if you want 
routers to actually implement them, and you want to scale in both forwarding 
speed and number of tunnels, then yes they do have to be stateless. 

Ross
(speaking only as an individual contributor) 

-----Original Message-----
From: mpls [mailto:mpls-bounces(_at_)ietf(_dot_)org] On Behalf Of Eggert, Lars
Sent: Thursday, January 16, 2014 12:20 PM
To: EXT - joelja(_at_)bogus(_dot_)com
Cc: mpls(_at_)ietf(_dot_)org; IETF discussion list
Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating 
MPLS in UDP) to Proposed Standard

Hi,

On 2014-1-16, at 18:06, joel jaeggli <joelja(_at_)bogus(_dot_)com> wrote:
These tunnels are stateless

yep. (But they don't have to be.)

 The endpoints not the encapsulators have visibility into the
end-to-end loss latency properties of the path.

Yep. But when you tunnel some L2 in UDP, apps that were limited to L2 domains - 
where not reacting to congestion may be OK - can now go over the wider 
Internet, where this is not OK.

I'd be great if those apps would change. But in the meantime, it's the duty of 
the encapsulator - who enables this traffic to break out of an L2 domain and go 
over the wider net - to make sure the traffic it emits conforms to our BCPs.

 the encapsulator is an intermediate hop, similar to any other router
in the path.

It's not. For the rest of the network, that encapsulator is indistinguishable 
from any other app that sends UDP traffic.

UDP is a transport-layer protocol, and we have practices how it is to be used 
on the net. If you want to use it for encapsulation, you bind yourself to these 
BCPs.

Look at it the other way: if transport area folks would want to send MPLS 
packets into the network in some problematic way, I'm sure the routing and ops 
folks would not be amused.

Lars


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