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

[joel jaeggli <[e-mail]>]

On 1/16/14, 9:35 AM, Stewart Bryant wrote:

>> 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.
> The root cause of the problem here is that UDP, has bifurcated into a
> general purpose encapsulation.

One observation with respect to general purpose use of UDP as an mpls
encapsulation on the internet as a whole that seems to have been missed
in this discussion is the rather dire prospects for MTU and potential for
fragmentation. Effectively, assuring, that you do not need to fragment
requires as certain amount of coordination.

1500 mtu hops pretty effectively (imho) preclude the use of this
encapsulation on the internet as a whole (if encapsulated traffic is not
aware of a correspondingly lower MTU) this is especially true for L2vpn
where you don't have recourse to PMTUD). As the document notes (section 4)
preventing fragmentation is rather important.


> Stewart
>