Re: [rtcweb] NAT behavior heuristics

Cameron Byrne <> Sun, 05 August 2012 12:32 UTC

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Date: Sun, 5 Aug 2012 05:32:26 -0700
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From: Cameron Byrne <>
To: Randell Jesup <>
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Subject: Re: [rtcweb] NAT behavior heuristics
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On Aug 5, 2012 12:20 AM, "Randell Jesup" <> wrote:
> On 8/2/2012 7:15 PM, Dan Wing wrote:
>>> -----Original Message-----
>>> From: Martin Thomson []
>>> Sent: Thursday, August 02, 2012 4:02 PM
>>> To: Dan Wing
>>> Cc:
>>> Subject: Re: [rtcweb] NAT behavior heuristics
>>> I assume that this applies only to the NAT that doesn't exist yet and
>>> that we will have to live with status quo (and the current keep-alive
>>> recommendations) until PCP becomes bountiful.
>> Yes.  PCP is new, somewhat like RTCWEB.
>> There is an incentive for the existing CGNs, deployed by almost all
>> 3G/LTE carriers around the world, to have their vendors add PCP
>> support to those NATs, as it saves battery lifetime for their
>> subscribers and reduces chatter on their network.  Incentives are
>> well aligned for that to happen.
>> I agree that home NATs, enterprise NATs, and enterprise firewalls
>> do not have those same incentives.
> And that's a rub, since in many/most cases, the 3G/LTE people will likely
be talking to non-3G/LTE people, and if either side needs keepalives, then
radio will be kept active.  Note we're talking long-term inactive media
flows and an inactive (or rarely active) datachannel, such as a client
using PeerConnection and DataChannels to keep a registration or empty
conference alive, or various non-phone-like applications.
> An alternative mechanism for keepalives might help - you can use
short-TTL packets to prop the local router without letting the packet go
all the way to the other end.  If the fixed-station PC uses this TTL trick,
and the mobile unit uses PCP, the mobile unit can keep its radio off.

Fyi. I have not seen any traction for pcp anywhere in the mobile space.
Not on host and not on the CGN. I would not assume it will catch on. As a
mobile operator i have zero plans for ever supporting it. I have operated
CGN in mobile for years, most mobile operators have, and we don't see
inbound connections to mobiles via the cgn as a requirement (nat44 works
today, and applying polish to crap is not productive)

I would avoid the rtcweb layer going into too much effort to optimize
batteries of devices. The intention is good, but at some point it becomes a
layer violation and suboptimization.

Ipv6 is the solution to these issue.


> Short-TTL can be handy for reducing loads on servers, especially where
the port needs to stay open with no real traffic for long periods (think
> The local router is rarely more than 5-7 hops from a device, though there
are pathological cases; this could be configured (and disableable).  There
are also ways to do discovery on the local router; these might work better
than discovery of UDP port binding time, which is known to not work.
> --
> Randell Jesup
> _______________________________________________
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