Subject: [mpls] Martin Stiemerling's Discuss on draft-ietf-mpls-in-udp-10: (with DISCUSS)

From: "Martin Stiemerling" <[email-masked]>
Date: Wed, 21 Jan 2015 09:32:47 -0800

Martin Stiemerling has entered the following ballot position for
draft-ietf-mpls-in-udp-10: Discuss

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DISCUSS:
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The draft improved a lot and I am on no-objection after discussing the
point below:

The UDP source port is randomly chosen and I guess not further retained
(*) for receiving incoming MPLS-over-UDP packets. In turn this means that
"returning" packets are sent to the MPLS/UDP port number. 

(*) nobody is listening on that UDP port. 

This will cause issues when NATs/firewalls are in-between, as the return
traffic, i.e., the traffic incoming from the public part of the NAT, is
not matching any NAT binding that was created before by an outgoing
packet. Similar for firewalls as no state was created when the packet
traversed the firewall. 

NATs are probably not a big issue in a carrier net, but firewalls will
for sure. I guess this should be mentioned as an operational note.