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Re: [rtcweb] SDP Security Descriptions (RFC 4568) and RTCWeb

Dan Wing <dwing@cisco.com> Fri, 26 April 2013 13:53 UTC

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From: Dan Wing <dwing@cisco.com>
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Date: Fri, 26 Apr 2013 06:53:08 -0700
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To: Tim Panton <tim@phonefromhere.com>
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Subject: Re: [rtcweb] SDP Security Descriptions (RFC 4568) and RTCWeb
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On Apr 26, 2013, at 6:29 AM, Tim Panton <tim@phonefromhere.com> wrote:

> 
> On 26 Apr 2013, at 14:24, Matthew Kaufman wrote:
> 
>> On 4/26/2013 6:16 AM, Tim Panton wrote:
>>> 
>>> On 26 Apr 2013, at 12:37, Iñaki Baz Castillo wrote:
>>> 
>>>> Such a solution requires a very expensive gateway. Good for vendors but bad for all the rest.
>>>> 
>>> 
>>> I don't understand why the DTLS gateway would be so expensive. It is _exactly_ the same
>>> (conceptually) as the ICE processing - you filter off a few UDP packets from the stream, do some
>>> stuff, send replies then once you are happy you punt some dynamic settings back up to the (s)rtp
>>> layer.
>>> 
>> 
>> The CPU-seconds of cryptography required are markedly different, especially on low-end processors used by some of the distributed gateway solutions.
> 
> True, but only at call set-up time, not for the life of the call. I'd want to see numbers on this before we select to adopt even 
> more complexity for the sake of a theoretical legacy interop requirement.

Right - only at call setup and only when keys change.  The SRTP packets themselves are not decrypted/encrypted.

-d

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