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 ! > ******************************************* >
