On 01/04/2010, at 7:37 PM, Philippe d'Anfray wrote: > Bonjour, > > Just to summarize, I have ran more tests on another site where > Multicast > is enabled: > > * With VPCscreen only, all packets corresponding to the video stream > are > given a TTL of 16 > * With VPCscreen and a Video Producer I can see packets with a TTL > of 16 > and others with a TTL of 127 > > Only those with a TTL of 127 can be received outside the site. > > Has someone used VPCScreen successfully in Multicast ?
Phillipe, Yes, as per one of my earlier emails, our results are somewhat different to yours - our use of vpcscreen with multicast shows no problems so far. Although it is clearly wrong that vpcscreen's ttl is somehow reset to 16 even when you explicitly set it to 127, I would nevertheless expect that a ttl of 16 is more than sufficient for most multicast sessions within a country - try an ordinary ping to one of your regular destinations - does it take more than 16 hops? So, although there is something wrong with vpcscreen, I think the issue is made worse by some router misconfiguration somewhere in your area (perhaps wrongly passing only multicast traffic with ttl of, say 32). How to fix vpcscreen? I had a quick look through the source code for obvious problems yesterday and found one potential issue but haven't had a chance to investigate it yet - maybe in the next few days. BTW you could confirm that the reduced ttl is actually the cause of your original problem with vpcscreen by running vic (which works as expected with multicast, I think?) with a lower ttl too - does it then exhibit the same problem of not reaching the destination when you set its ttl to 16? chris Christoph Willing +61 7 3365 8316 QCIF Access Grid Manager University of Queensland
