From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from uplift.swm.pp.se (swm.pp.se [212.247.200.143]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id 0656421F21F for ; Thu, 7 May 2015 02:16:34 -0700 (PDT) Received: by uplift.swm.pp.se (Postfix, from userid 501) id A7E5BA1; Thu, 7 May 2015 11:16:31 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=swm.pp.se; s=mail; t=1430990191; bh=lonDssElYUEDyPqNFoisb+4cGPd5xBiExNhW4R/5/PE=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=xord83zVsKA0Q5jwEcSLVxXSW+YDA/3vhrXJT9cDhk9y1tpjd940OogfRUjID6ZmW w+WmkYxX57AazK97hr97KZcKthaL+JkA27QZ9Q5VuLoyg/N5K6ygIWghuD7wT3wFpP gH8S03S/4Ly047J0ZI7EzM/XT72194ZCrQCryyD0= Received: from localhost (localhost [127.0.0.1]) by uplift.swm.pp.se (Postfix) with ESMTP id 9F7849F; Thu, 7 May 2015 11:16:31 +0200 (CEST) Date: Thu, 7 May 2015 11:16:31 +0200 (CEST) From: Mikael Abrahamsson To: Sebastian Moeller In-Reply-To: <9CF0E173-2CE5-4950-84D1-44EAEF174882@gmx.de> Message-ID: References: <6C0D04CF-53AA-4D18-A4E4-B746AF6487C7@gmx.de> <87wq123p5r.fsf@toke.dk> <2288B614-B415-4017-A842-76E8F5DFDE4C@gmx.de> <553B06CE.1050209@superduper.net> <14ceed3c818.27f7.e972a4f4d859b00521b2b659602cb2f9@superduper.net> <0C930D43-A05B-48E2-BC01-792CAA72CAD1@gmx.de> <5549A1B8.50005@superduper.net> <9CF0E173-2CE5-4950-84D1-44EAEF174882@gmx.de> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) Organization: People's Front Against WWW MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: bloat Subject: Re: [Bloat] DSLReports Speed Test has latency measurement built-in X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 May 2015 09:17:03 -0000 On Thu, 7 May 2015, Sebastian Moeller wrote: > Is this 40ms sort of set in stone? If so we have a new indicator > for bad buffer-bloat if inured latency > 40 ms link is unsuitable for > decent voip (using old equipment). Is the newer voip stuff that telcos > roll out currently any smarter? The 40ms is fairly typical for what I encountered 10 years ago. To deploy them there was a requirement to have QoS (basically low-latency queuing on Cisco) for DSCP EF traffic, otherwise things didn't work on the 0.5-2 megabit/s connections that were common back then. I'd say anything people are trying to deploy now for use on the Internet without QoS, 40ms just won't work and has never really worked. You need adaptive PDV-buffers and they need to be able to handle hundreds of ms of PDV. If you look at this old document from Cisco (10 years old): http://www.ciscopress.com/articles/article.asp?p=357102 "Voice (Bearer Traffic) The following list summarizes the key QoS requirements and recommendations for voice (bearer traffic): Voice traffic should be marked to DSCP EF per the QoS Baseline and RFC 3246. Loss should be no more than 1 percent. One-way latency (mouth to ear) should be no more than 150 ms. Average one-way jitter should be targeted at less than 30 ms. A range of 21 to 320 kbps of guaranteed priority bandwidth is required per call (depending on the sampling rate, the VoIP codec, and Layer 2 media overhead). Voice quality directly is affected by all three QoS quality factors: loss, latency, and jitter." This requirement kind of reflects the requirements of the VoIP systems of the day with 40ms PDV buffer. There is also a section a page down or so about "Jitter buffers" where there is a recommendation to have adaptive jitter buffers, which I didn't encounter back then but I really hope is a lot more common today. -- Mikael Abrahamsson email: swmike@swm.pp.se