From lachlan.andrew at gmail.com Mon Jan 7 14:07:42 2008 From: lachlan.andrew at gmail.com (Lachlan Andrew) Date: Mon, 7 Jan 2008 14:07:42 -0800 Subject: [Tmrg] (limited) measurement of file size vs congestion level Message-ID: Greetings all, During the discussion of what traffic parameters to change to test different levels of congestion, we noted the lack of measurement of file sizes w.r.t. congestion level. The measurements reported in Table I of K Shah, S Bohacek "High short-term bit-rates from TCP Flows," MASCOTS, 2005 suggest strongly that increased congestion comes from increased mean file size, rather than simply increased arrival rate. For different link utilisations, here are the mean file sizes, and number of flows per hour: 4%: 2.85 kByte 16.8M 5.4%: 4.85 kByte 12.8M 25%: 9.80 kByte 29.2M 35%: 10.1 kByte 39.5M 48%: 13.2 kByte 41.2M This suggests that to increase congestion by a factor of x, we should increase both the arrival rate and the mean file size by a factor of sqrt(x). Thoughts? Lachlan -- Lachlan Andrew Dept of Computer Science, Caltech 1200 E California Blvd, Mail Code 256-80, Pasadena CA 91125, USA Ph: +1 (626) 395-8820 Fax: +1 (626) 568-3603 http://netlab.caltech.edu/~lachlan From sallyfloyd at mac.com Mon Jan 7 19:00:19 2008 From: sallyfloyd at mac.com (Sally Floyd) Date: Mon, 7 Jan 2008 19:00:19 -0800 Subject: [Tmrg] (limited) measurement of file size vs congestion level In-Reply-To: References: Message-ID: <85e556a7e9ab3c208a851e253133f216@mac.com> Lachlan - > This suggests that to increase congestion by a factor of x, we > should increase both the arrival rate and the mean file size by a > factor of sqrt(x). That sounds reasonable to me. (While there has been a fair amount of research on characterizing aggregate traffic in the Internet, there hasn't been much about aggregate traffic on congested links. Not just with respect to the level of congestion, but the type or bandwidth of the congested link, etc. But maybe that will come.) - Sally http://www.icir.org/floyd/ On Jan 7, 2008, at 2:07 PM, Lachlan Andrew wrote: > Greetings all, > > During the discussion of what traffic parameters to change to test > different levels of congestion, we noted the lack of measurement of > file sizes w.r.t. congestion level. > > The measurements reported in Table I of > K Shah, S Bohacek "High short-term bit-rates from TCP Flows," > MASCOTS, 2005 > > suggest strongly that increased congestion comes from increased mean > file size, rather than simply increased arrival rate. > > For different link utilisations, here are the mean file sizes, and > number of flows per hour: > 4%: 2.85 kByte 16.8M > 5.4%: 4.85 kByte 12.8M > 25%: 9.80 kByte 29.2M > 35%: 10.1 kByte 39.5M > 48%: 13.2 kByte 41.2M > > This suggests that to increase congestion by a factor of x, we > should increase both the arrival rate and the mean file size by a > factor of sqrt(x). > > Thoughts? > > Lachlan > > -- > Lachlan Andrew Dept of Computer Science, Caltech > 1200 E California Blvd, Mail Code 256-80, Pasadena CA 91125, USA > Ph: +1 (626) 395-8820 Fax: +1 (626) 568-3603 > http://netlab.caltech.edu/~lachlan > _______________________________________________ > Tmrg-interest mailing list > Tmrg-interest at ICSI.Berkeley.EDU > http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/tmrg-interest > From sallyfloyd at mac.com Mon Jan 7 19:56:29 2008 From: sallyfloyd at mac.com (Sally Floyd) Date: Mon, 7 Jan 2008 19:56:29 -0800 Subject: [Tmrg] (limited) measurement of file size vs congestion level In-Reply-To: References: Message-ID: Lachlan - As an additional comment, my assumption would be that users' behavior is *heavily* affected by the level of congestion, but I don't know that much research has been done on this. That is, I would assume that users would cut their Internet browsing short in times of heavy congestion (i.e., of slow response times and long download times), in terms of the number of TCP connections initiated. I wouldn't have had a good guess, however, what this would mean to the distribution of connection sizes. It might mean different things on different type links. - Sally http://www.icir.org/floyd/ From ricciato at ftw.at Tue Jan 8 01:44:31 2008 From: ricciato at ftw.at (ricciato) Date: Tue, 08 Jan 2008 10:44:31 +0100 Subject: [Tmrg] (limited) measurement of file size vs congestion level In-Reply-To: References: Message-ID: <478345FF.6050306@ftw.at> Hi Sally, all [I am new to the list] just an humble comment on the relationship between congestion and user behaviour. 1. there is a very preliminary study [1] investigating the issue 2. we have found and reported in [2] a case of severe congestion on "our" network, i.e. a mobile UMTS network that we extensively and constantly monitor in our project [3]. There we show that the presence of the bottleneck changes the statistics of the aggregate traffic, of course. An analysis of the impact of user-behaviour (change in file-size, abandoning, re-clicks, etc.) based on the detailed packet-traces was always in our to-do list, but so far had not time to work that out (there are some complications in doing user-level analysis, e.g. the file-size does not correspond to the TCP connection size, as the relationship file:connections is NOT 1:1 in modern applications, we, p2p etc.) 3. However, based on our experience (we have seen many severe congestion events in this network), I can report the following qualitative observations A. the user abandoning process seems to be "with threshold" : if you consider the frequency of TCP RST as a gross indicator of user (or server) impatience, we saw that for mild congestion (right before the peak hour, on a congested link) the RST stay at physiological level (pretty low), while it sharply jumps to abnormally high values when the congestion becomes severe (during the peak hour) B. if you look at the distribution of the number of packets downloaded by each users in fixed timebins (e.g. 1 min), you see that after a capacity upgrade that removes a congestion points, such distribution changes, with more user downloading more packets (as expected). 4. My expectation is that the users regulate the duration of the *session* and the total download rate (often across multiple parallel TCP connection) based on the experienced response time, there it is the *session* attributes (duration, rate), rather than the *file* ones, that are dependent on the congestion level. At the TCP level, this might means that it?s the connection arrival process that is mostly impacted, rtaher than the size (the latter is probably affected only in the tail of long files, which are probably truncated upon congestion). Furthermore, after a certain threshold (severe congestion), users or servers suddenly get crazy and start to reclick/reset the downloads, and eventually give up the session. ciao fabio [1] "User patience and the Web: a hands-on investigation", by Rossi, Casetti, Mellia, @ Globecom 2003. [2] F. Ricciato, F. Vacirca, P. Svoboda, Diagnosis of Capacity Bottlenecks via Passive Monitoring in 3G Networks: an Empirical Analysis, Computer Networks, vol. 51, n.4, pp. 1205-1231, March 2007 [3] http://userver.ftw.at/~ricciato/darwin/ Sally Floyd wrote: > Lachlan - > > As an additional comment, my assumption would be that users' behavior > is *heavily* affected by the level of congestion, but I don't know > that much research has been done on this. That is, I would assume > that users would cut their Internet browsing short in times of heavy > congestion (i.e., of slow response times and long download times), > in terms of the number of TCP connections initiated. > > I wouldn't have had a good guess, however, what this would mean to > the distribution of connection sizes. It might mean different > things on different type links. > > - Sally > http://www.icir.org/floyd/ > > _______________________________________________ > Tmrg-interest mailing list > Tmrg-interest at ICSI.Berkeley.EDU > http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/tmrg-interest > Sally Floyd wrote: > Lachlan - > > As an additional comment, my assumption would be that users' behavior > is *heavily* affected by the level of congestion, but I don't know > that much research has been done on this. That is, I would assume > that users would cut their Internet browsing short in times of heavy > congestion (i.e., of slow response times and long download times), > in terms of the number of TCP connections initiated. > > I wouldn't have had a good guess, however, what this would mean to > the distribution of connection sizes. It might mean different > things on different type links. > > - Sally > http://www.icir.org/floyd/ > > _______________________________________________ > Tmrg-interest mailing list > Tmrg-interest at ICSI.Berkeley.EDU > http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/tmrg-interest > From mascolo at poliba.it Tue Jan 22 10:28:11 2008 From: mascolo at poliba.it (Saverio Mascolo) Date: Tue, 22 Jan 2008 19:28:11 +0100 Subject: [Tmrg] Implementation of XCP and similar feedback from routers ... Message-ID: <01b901c85d24$a97804c0$723bccc1@HPSM> dear all, i would like to ask who knows on the state of implementation, in commercial routers, of mechanisms to provide feedback to improve e2e congestion control such as XCP and similar. thanks for the attention, Saverio Mascolo, Dipartimento di Elettrotecnica ed Elettronica Politecnico di Bari -------------- next part -------------- An HTML attachment was scrubbed... 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