Re: [rtcweb] STUN for keep-alive

Christer Holmberg <christer.holmberg@ericsson.com> Wed, 14 September 2011 17:18 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: 'Eric Rescorla' <ekr@rtfm.com>, Harald Alvestrand <harald@alvestrand.no>
Date: Wed, 14 Sep 2011 19:20:33 +0200
Thread-Topic: [rtcweb] STUN for keep-alive
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] STUN for keep-alive
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Hi, 

>One new concern in this context is maintaining the consent freshness.
>The browser needs to be sure that the recipient of traffic is stil responding in a way that can't be forged. It's likely RTCP provides this (though we'd need to analyze to be sure) but perhaps better would be to mandate STUN checks 
>at enough frequency that you get some sort of level of freshness.... maybe every 2 minutes or something.

Please note that the STUN keep-alives are implemented using STUN indication messages, so there are no replies (nor does the receiver perform an authentication check).

Regards,

Christer


On Wed, Sep 14, 2011 at 9:14 AM, Harald Alvestrand <harald@alvestrand.no>; wrote:
> On 09/14/11 15:07, Christer Holmberg wrote:
>>
>> Hi,
>>
>>>> |Sure, but there is still a max time between the keep-alives.
>>>
>>> You are free to set it to a very long duration that disables 
>>> keepalives for all practical purposes (assuming such duration is 
>>> represented by a 32-bit unsigned integer you can set it to
>>> ~136 years).
>>
>> Yes, but at the end of the day something has to be sent in order to 
>> keep the NAT binding open.
>>
>>>> |Using e.g. RTP, the media handler would not have to be prepared to 
>>>> |receive the STUN keep-alives in the first place, it could simply 
>>>> |just relay whatever comes on the media plane.
>>>
>>> If the media handles can handle STUN binding requests efficiently I 
>>> don't see why they can't handle STUN binding indications 
>>> (keepalives) in a similar manner.
>>
>> I believe it knows when to expect those. But, in any case, the main 
>> reason behind the proposal is to decrease the number of STUN requests.
>
> I think it's a more urgent desire that we should minimize the number 
> of variants of protocols in use.
> Defining a variant of ICE that modifies the keepalive mechanism seems 
> to me like a Bad Idea.
>
>                     Harald
>
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