Cable Forum - View Single Post - Dropouts in web access to JANET and BBC...

tomo · 02-03-2008, 17:55

I also work for a University, located in London, on the JANET network. And to be honest I never have any issues with connectivity. I can work from home from time to time and SSH and SSL sessions stay active for hours.

That being said I have seen an issue occur twice in the past 12 months when basic connectivity is fine (ICMP works) but TCP/UDP connectivity to a random selection of places (not just BBC or JANET) does not work.

When this occurs I give VM Tech Support a ring, and provided that the person answering has got some clue (once it required a second phone call) I usually explain that

the basic network path is there, ie. ICMP ping/tracert is ok,
TCP and UDP to random destinations appears to be dropped,
the destinations that are non-responsive are constantly non-responsive during the problem, those that work, do work consistantly
Using a different DNS server or IP addresses does not change matters (on both occasions the primary VM DNS server was a non-responsive destination)
I've restarted the Cable Modem
I've removed my router and connected my laptop directly to the cable modem
those sites are down are OK from the same laptop using an independent internet connection (GPRS/3G) - so it's not my laptop at fault.
I'm attached to UBR 2 in Watford

The VM tech has a look around for scheduled maintenance, checks my connection, pronounce all is OK. But usually within 10mins it appears to be cleared. Although no one ever admits anything.

I suspect that someone does a restart of soemthing upstream of me that has got a messed up network stack. There's nothing reported in the CM logs to indicate that the CM has had to renogiate.

Hope this helps in someway.

02-03-2008, 17:55	#6
tomo Inactive Join Date: Mar 2008 Posts: 4	Re: Dropouts in web access to JANET and BBC... I also work for a University, located in London, on the JANET network. And to be honest I never have any issues with connectivity. I can work from home from time to time and SSH and SSL sessions stay active for hours. That being said I have seen an issue occur twice in the past 12 months when basic connectivity is fine (ICMP works) but TCP/UDP connectivity to a random selection of places (not just BBC or JANET) does not work. When this occurs I give VM Tech Support a ring, and provided that the person answering has got some clue (once it required a second phone call) I usually explain that the basic network path is there, ie. ICMP ping/tracert is ok, TCP and UDP to random destinations appears to be dropped, the destinations that are non-responsive are constantly non-responsive during the problem, those that work, do work consistantly Using a different DNS server or IP addresses does not change matters (on both occasions the primary VM DNS server was a non-responsive destination) I've restarted the Cable Modem I've removed my router and connected my laptop directly to the cable modem those sites are down are OK from the same laptop using an independent internet connection (GPRS/3G) - so it's not my laptop at fault. I'm attached to UBR 2 in Watford The VM tech has a look around for scheduled maintenance, checks my connection, pronounce all is OK. But usually within 10mins it appears to be cleared. Although no one ever admits anything. I suspect that someone does a restart of soemthing upstream of me that has got a messed up network stack. There's nothing reported in the CM logs to indicate that the CM has had to renogiate. Hope this helps in someway.