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

[<[e-mail]>]

Surely you mean minimised state?

The tunnels have to know where the other tunnel endpoint is - state. This is distinct from having a congestion-aware state machine that e.g. TCP includes...

Lloyd Wood
http://about.me/lloydwood
________________________________________
From: mpls [[e-mail]] On Behalf Of Ross Callon [[e-mail]]
Sent: 16 January 2014 22:32
To: Eggert, Lars
Cc: EXT - [e-mail]; [e-mail]; IETF discussion list
Subject: Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard

>> 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:[e-mail]] On Behalf Of Eggert, Lars
Sent: Thursday, January 16, 2014 12:20 PM
To: EXT - [e-mail]
Cc: [e-mail]; 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 <[e-mail]> 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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