Re: [rtcweb] NAT behavior heuristics

<> Tue, 07 August 2012 14:13 UTC

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Thread-Topic: [rtcweb] NAT behavior heuristics
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Subject: Re: [rtcweb] NAT behavior heuristics
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Hi Cameron,

Cameron Byrne wrote:
>I asked around in Vancouver about PCP, and all the operators i spoke to said
>no-plans, no motivation.  But, that was a small sample.

This is probably a fair assessment about the concrete plans. Most mobile operators don't even follow IETF much, so I doubt that they have even heard about PCP so far. There are however a few operators, where at least the research and standardization people have been interested in PCP (as witnessed by I think some operators are also proposing PCP to be included in the 3GPP specs (release 12). It is hard to say how much that means in the real world, but at least I'd expect we could find a few operators willing to do real-network trials withing the next 12 months. 

Personally I see PCP as a very useful tool in the cellular access environment, for probing the NAT/FW timers and in the best case even setting them. It will be a major chicken-and-egg situation between apps, mobile OS's and the networks, to get anything into use. I think we should still do our best to overcome it. I agree that RTCWeb or anyone else should not rely on PCP (or any similar mechanim), but have the ability to make use of it if it happens to be available. 

I'm unconvinced IPv6 will help at all in this case. How do you know how long the FW on the path will keep its state up without keepalives? It will probably be the same as for NATs: In some networks timeout is 2 minutes, while in others 60 minutes. Having something like PCP to check out that it indeed is 60 min. would be extremely helpful. While most app developers might not be willing/able to optimize for battery/mobile, there are already some that are doing a good job. So there is hope that the new mechanisms would get some traction.


>-----Original Message-----
>From: [] On Behalf
>Of ext Cameron Byrne
>Sent: 06 August, 2012 01:22
>To: Tirumaleswar Reddy (tireddy)
>Cc: Randell Jesup;;
>Subject: Re: [rtcweb] NAT behavior heuristics
>On Sun, Aug 5, 2012 at 3:05 PM, Tirumaleswar Reddy (tireddy)
><> wrote:
>>> Fyi. I have not seen any traction for pcp anywhere in the mobile space.
>> describes
>usage of PCP in Mobile Deployments.
>> --Tiru.
>Yep, that's  an I-D.
>And, it says things like "Without
>   the particular considerations , PCP may not provide desirable
>   outcomes.  Some default behaviours may even cause negative impacts or
>   system failures in a mobile environment.  "
>Got an operators with a timeline on supporting it?  How about a mobile OS
>that plans to support PCP, because you will need both.  And, that would be
>interesting information.
>I asked around in Vancouver about PCP, and all the operators i spoke to said
>no-plans, no motivation.  But, that was a small sample.
>In any event, my only point is that RTCWEB should NOT be counting on PCP.  If
>PCP is a tool you have, use it.  My point: it is not a tool you have.
>rtcweb mailing list