Subject: [pcp] PORT_SET for application protocols other than SIP

From: Simon Perreault <[email-masked]>
Date: Thu, 14 Mar 2013 16:24:17 -0400

During the meeting earlier today there was a question about whether any 
application protocol other than SIP could benefit from PORT_SET.

There were some replies to that question that involved the notion of set 
contiguity.

Contiguity has nothing to do with it. It's not because SIP likes to make 
use of contiguous ports that it would benefit from PORT_SET. It's all 
about optimization. A SIP UAS would be faster if it preallocated a bunch 
of ports instead of sending a PCP request each time it needed one. It 
could do that with individual MAP requests, but that would not be as 
efficient as a single PORT_SET for a number of reasons well stated in 
the draft.

I stand by my comment that it would be easy to imagine a protocol that 
would benefit similarly.

But I'll go further with a bold and daring example: PCP itself could 
benefit from PORT_SET. Imagine a back-to-back PCP server/client, as 
described in draft-cheshire-recursive-pcp. Imagine that it is very busy, 
handling many requests per second. It could benefit from PORT_SET by 
obtaining ports from upstream in big chunks. Then it would manage those 
chunks like port pools from which it would allocate to downstream 
clients. That could be more efficient than obtaining ports from upstream 
with individual MAP requests.

Simon
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From: <[email-masked]>
Date: Fri, 15 Mar 2013 08:31:50 +0100

Hi Simon,

I do agree with your points. 
Please see inline.
Cheers,
Med

>-----Message d'origine-----
>De : [email-masked] [mailto:[email-masked]] De la 
>part de Simon Perreault
>Envoyé : jeudi 14 mars 2013 21:24
>À : [email-masked]
>Objet : [pcp] PORT_SET for application protocols other than SIP
>

Med: I would say SDP instead. If other examples are needed to cite: there are other non-SDP protocols in the field such as H.323. 

>about optimization.

Med: Fully agree. An example is when an address sharing device is configured with a very low address sharing ratio (e.g., 1:2 or 1:5). It would benefit from the PORT_SET option.

 A SIP UAS would be faster if it 
>preallocated a bunch 

Med: Hence the initial name of the draft: NAT COORDINATION ;-)