Re: [rtcweb] NAT behavior heuristics

"Tirumaleswar Reddy (tireddy)" <> Sun, 05 August 2012 22:05 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id CC2BA21F851B for <>; Sun, 5 Aug 2012 15:05:53 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -10.599
X-Spam-Status: No, score=-10.599 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, RCVD_IN_DNSWL_HI=-8]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id RMxdleg7afhY for <>; Sun, 5 Aug 2012 15:05:53 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id EB7EF21F8575 for <>; Sun, 5 Aug 2012 15:05:52 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=3337; q=dns/txt; s=iport; t=1344204353; x=1345413953; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=Dz+rq5TTBCya5v0Uj4u/zoqQYngD01wLHGCOApvepA8=; b=ThFBaZnGZWhvrAr6uPJEvCRKcwyF81laYc5mO0ptCstZGrh/JjcF7+J2 8fG8awU4DP54aqD5dF/6fu+VHagTWxeTnc0jlBBGbu7fsNtOQq5oHqmIl yv07z61LEETnkFOGj906YR9l+xGhacqXSD+UHU8voslVx6sK3ACUHDEWX g=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="4.77,715,1336348800"; d="scan'208";a="108638982"
Received: from ([]) by with ESMTP; 05 Aug 2012 22:05:52 +0000
Received: from ( []) by (8.14.5/8.14.5) with ESMTP id q75M5q8C001670 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL); Sun, 5 Aug 2012 22:05:52 GMT
Received: from ([]) by ([]) with mapi id 14.02.0298.004; Sun, 5 Aug 2012 17:05:52 -0500
From: "Tirumaleswar Reddy (tireddy)" <>
To: Cameron Byrne <>, Randell Jesup <>
Thread-Topic: [rtcweb] NAT behavior heuristics
Thread-Index: Ac1w1ovfvzUgFxvbR0qnhkeGI2kOuAAVj+eAAAB2nYAAdXC7AAAK960AAAlqvrA=
Date: Sun, 5 Aug 2012 22:05:51 +0000
Message-ID: <>
References: <038b01cd70d6$8c5bc870$a5135950$@com> <> <04ff01cd7104$be09bed0$3a1d3c70$@com> <> <>
In-Reply-To: <>
Accept-Language: en-US
Content-Language: en-US
x-originating-ip: []
x-tm-as-product-ver: SMEX-
x-tm-as-result: No--40.769300-8.000000-31
x-tm-as-user-approved-sender: No
x-tm-as-user-blocked-sender: No
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Cc: "" <>, "" <>
Subject: Re: [rtcweb] NAT behavior heuristics
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Sun, 05 Aug 2012 22:05:54 -0000

> Fyi. I have not seen any traction for pcp anywhere in the mobile space. describes usage of PCP in Mobile Deployments.


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 SIP).
> 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
> _______________________________________________
> rtcweb mailing list