Hi Tried with an MS-Windows version of tracert (ftrace), it was supposed to be able to set the ToS field. However it seems like when I run wireshark that the modified ToS field does not stick, it could be some Windows specific feature that simply clears the ToS field. I will try some traceroute tests on our Linux boxes next week when I really start working. It could be that this will do.
I also tried http://www.microsoft.com/windows/using/tools/igd/default.mspx as it claimed that my homelaptop is indeed ECN capable. The test seems however to be a bit limited and perhaps a bit faulty. The SYN packet sets ECE and CWR according to RFC3168, the ECE flag is however not set in the SYN-ACK packet, still the ECN test is marked as passe!. Also the ECN bits are never set in any subsequent data traffic which means that AFAIK nothing is really tested. I have not looked at PlanetLab earlier, will have a look at it, thanks for the tip. Regards /Ingemar > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Piers O'Hanlon > Sent: den 20 augusti 2009 18:38 > To: Ingemar Johansson S > Cc: iccrg; tsv-area; carlberg; Colin Perkins; Magnus Westerlund > Subject: Re: Testing ECN support for UDP flows > > Hi Ingmar, > > I found that one could do some quite useful tests using (on > Linux) traceroute -t <tos> hostname. Linux machines seem to > reflect the TOS byte contents even in ICMP error responses > and ICMP echos. Though DSCP bits are usually reset the the > ECN bits are more resilient... Since traceroute uses UDP as > default it's quite a neat test. And it seems that ICMP time > exceeded responses are more likely to get thru router filters > than plain ICMP responses - and the can carry ECN markings. > Though it seems that that there maybe some bugs in certain > routers as I've seen the TOS byte reversed in some replies?! > > As ken mentioned - I was thinking that wide area testing > could be most easily done using PlanetLab - though as far as > I'm aware it doesn't tunnel packets - though packet timings > can get skewed by the vserver implementation. Also the > network sharing system in use on Planetlab can make things > tricky if someone else on that machine using the same ports. > > Additionally it may be worth checking with the methodology > used by Floyd et al when they did their [tcp] tbit testing: > http://www.icir.org/tbit/ecn-tbit.html > > Piers. > > 2009/8/20 Ingemar Johansson S <[email protected]>: > > Hi > > > > Sorry for the cross-post, I would believe that it is best > to reply to tsv-area only. > > > > I have previously asked people regarding the support of ECN > especially > > for UDP flows.. There seems to be a lot of uncertanities > around this and in general it is difficult to get any clear > view (if there is any ?) So... how do I best test this on a > larger scale ? > > > > 1) UDP port 7: The idea is to ping other host with UDP > packets on port 7, some of the packets are ECT(0)/(1) marked, > some are not. If I get things right, port 7 is not genarally > enabled these days, are there any host around that are known > to leave port 7 open. > > > > 2) Modified STUN client: The idea is to do STUN requests to > a number of STUN servers. Some of the STUN requests are ECT. > > > > 3) Setup a mesh of volountary hosts that installs a > software that agrees to communicate via a specific port, the > hack would need to implement some means to communicate NAT'ed > addresses etc. This would require some logistic effort to > gather up volounteers for the test-fest. > > > > Ideally the test should be able to tell if possible ECN > issues are located close to the user (e.g firewalls, WLAN > routers etc) or in the core-networks. Also I believe that > running UDP would be beneficial even though I know some > people have already tried with ICMP. > > > > Which would be the best alternative in order to do such a > test ?, comments/suggestions are welcome. > > > > Regards > > Ingemar > > > > ******************************************* > > Ingemar Johansson > > Senior Research Engineer, IETF "nethead" > > EAB/TVK - Multimedia Technologies > > Ericsson Research Ericsson AB > > Box 920 S-971 28 Luleå, Sweden > > Tel: +46 (0)10 7143042 > > ECN: 852-43042 > > ECC: 852-19042 > > Mobile: +46 (0)730 783289 > > Visit http://labs.ericsson.com ! > > ******************************************* > > >
