Subject: [pcp] To change a mapping does the pcp source port need remain the same?

From: [email-masked] (Eric W. Biederman)
Date: Sat, 15 Sep 2012 07:25:35 -0700

I have just been reading through draft-ietf-pcp-base-26.txt and figuring
out what it would take to implement.

In the normal non-authenticated case a pcp client will pick a randomized
source port and use that one port to create and refresh mappings.

Would it be an error for a pcp server to require pcp clients to use
the same source port that a mapping was established with to change
that mapping?

As a trivial way to keep different clients from stepping on each other
by accident I would certainly require the source port to remain constant
to change a mapping.

Eric

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From: Simon Perreault <[email-masked]>
Date: Mon, 17 Sep 2012 09:36:01 -0400

> the same source port that a mapping was established with to change

Yes it would.

> by accident I would certainly require the source port to remain constant

Two issues I see:

- It would only be a convenience, not secure, because it would be 
trivial to guess and spoof.

- With long-lived mappings it becomes hard to guarantee that the same 
port will be used for all requests.

Simon
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