Re: [rtcweb] Let's define the purpose of WebRTC

Harald Alvestrand <harald@alvestrand.no> Mon, 07 November 2011 14:09 UTC

Return-Path: <harald@alvestrand.no>
X-Original-To: rtcweb@ietfa.amsl.com
Delivered-To: rtcweb@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 3DDA621F8BEF for <rtcweb@ietfa.amsl.com>; Mon, 7 Nov 2011 06:09:48 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -110.545
X-Spam-Level:
X-Spam-Status: No, score=-110.545 tagged_above=-999 required=5 tests=[AWL=0.054, BAYES_00=-2.599, RCVD_IN_DNSWL_HI=-8, USER_IN_WHITELIST=-100]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id An0ILknv2FNf for <rtcweb@ietfa.amsl.com>; Mon, 7 Nov 2011 06:09:47 -0800 (PST)
Received: from eikenes.alvestrand.no (eikenes.alvestrand.no [158.38.152.233]) by ietfa.amsl.com (Postfix) with ESMTP id D81AE21F8B85 for <rtcweb@ietf.org>; Mon, 7 Nov 2011 06:09:46 -0800 (PST)
Received: from localhost (localhost [127.0.0.1]) by eikenes.alvestrand.no (Postfix) with ESMTP id 1C62B39E119 for <rtcweb@ietf.org>; Mon, 7 Nov 2011 15:09:46 +0100 (CET)
X-Virus-Scanned: Debian amavisd-new at eikenes.alvestrand.no
Received: from eikenes.alvestrand.no ([127.0.0.1]) by localhost (eikenes.alvestrand.no [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id nOxwuruFqVO4 for <rtcweb@ietf.org>; Mon, 7 Nov 2011 15:09:42 +0100 (CET)
Received: from hta-dell.lul.corp.google.com (62-20-124-50.customer.telia.com [62.20.124.50]) by eikenes.alvestrand.no (Postfix) with ESMTPS id 0F08439E112 for <rtcweb@ietf.org>; Mon, 7 Nov 2011 15:09:42 +0100 (CET)
Message-ID: <4EB7E6A5.70209@alvestrand.no>
Date: Mon, 07 Nov 2011 15:09:41 +0100
From: Harald Alvestrand <harald@alvestrand.no>
User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.23) Gecko/20110921 Thunderbird/3.1.15
MIME-Version: 1.0
To: rtcweb@ietf.org
References: <CALiegfkVNVAs_MyU_-4koA4zRwSn1-FwLjY9g_oZVkhi9rSK5Q@mail.gmail.com> <8A61D801-D14D-408B-9875-63C37D0CC166@acmepacket.com> <CABw3bnPE=OY_h5bM7GA6wgrXiOBL8P4J0kw1jLv-GSpHAbg=Cg@mail.gmail.com> <CABcZeBNqdkh8u=gwOvKfDCQA7rXdAyQkfaM1r2Sx10787btP6A@mail.gmail.com> <B10FEFF6-0ADC-4DB1-83BB-50A11C65EC35@acmepacket.com> <CABcZeBNSXtim_VqzqAd8Z-u4zWSjaYmsVZPN=7sDYkJsgtRAHA@mail.gmail.com>
In-Reply-To: <CABcZeBNSXtim_VqzqAd8Z-u4zWSjaYmsVZPN=7sDYkJsgtRAHA@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [rtcweb] Let's define the purpose of WebRTC
X-BeenThere: rtcweb@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <rtcweb.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/rtcweb>
List-Post: <mailto:rtcweb@ietf.org>
List-Help: <mailto:rtcweb-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 07 Nov 2011 14:09:48 -0000

On 11/07/2011 02:50 PM, Eric Rescorla wrote:
> On Sun, Nov 6, 2011 at 7:20 PM, Hadriel Kaplan<HKaplan@acmepacket.com>  wrote:
>>>> IMHO, if a web service doesn't want to take, or cannot take, the hit
>>>> for SRTP, WebRTC is not the appropriate solution for such a service.
>>> I'm exceedingly unsympathetic to the claim that SRTP is too slow. This
>>> is precisely the claim that was made about TLS for years, but measurements
>>> (see Langley and Modadugu's Overclocking SSL talk at Velocity) show
>>> that that's not really true.
>> Who said "too slow"?  There *is* an extra round-trip or two involved I presume, if we're talking DTLS-SRTP, but no I didn't mean that as a "hit".  I just meant the extra computing cycles for SRTP being a "hit".  For WebRTC-to-WebRTC I don't think that matters at all.  For WebRTC-to-media-server it might, for a free game app or greeting card app that don't care about it to begin with, and which use plaintext HTTP to begin with.
> Sorry, I didn't mean to put words in your mouth. Performance measurements
> of HTTP versus HTTPS in modern Web environments suggest that the additional
> load for HTTPS is not significant. Do you have evidence that the situation is
> different for SRTP versus RTP?
FWIW, one particularly clumsy implementation of a test of SRTP 
encryption speed that I dealt with spent nearly forty microseconds of 
(single-thread, no-hardware-acceleration) CPU time AES-encrypting an RTP 
packet - consuming nearly 0.1% of the time I had before the next packet 
arrived on that audio channel.

This, like all measurements, is false. But it convinced me that this was 
not the part of the system I needed to optimize.