Seeking Comcast Contact: need to troubleshoot packet loss and/or asymmetric routing issue between Comcast & Onvoy
Alain_Durand at cable.comcast.com
Thu Aug 2 13:43:35 UTC 2007
I've forwarded your message to the appropriate team within Comcast.
> -----Original Message-----
> From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On
> Behalf Of Craig D. Rice
> Sent: Thursday, August 02, 2007 9:30 AM
> To: nanog at merit.edu
> Subject: Seeking Comcast Contact: need to troubleshoot packet
> loss and/or asymmetric routing issue between Comcast & Onvoy
> For four months dozens of our users who are Comcast
> subscribers have had difficulty reaching St. Olaf College's
> and Carleton College's network services.
> We have worked through everything we can think of with our
> Onvoy (regional
> ISP) network engineers. We have isolated the problem a couple
> of Comcast's IP subnets, but need a contact within Comcast to
> further troubleshoot.
> The behavior in a nutshell:
> User A on Comcast Subnet B browses to www.stolaf.edu (http or
> https, other web sites on-site and @carleton.edu behave the
> same). Our access_log shows an initial "GET /" of our
> homepage, then very slow (if any) subsequent requests (for
> our stylesheet or homepage images). Ping's look fine;
> traceroute's look as reasonable. Telnet's to port 80 and
> other services do seem to respond, albeit very slowly.
> User A has the same problem with access @carleton.edu but can
> access everything else (including other Onvoy customers)
> without any trouble whatsoever.
> If User A then removes his Linksys router and connects his
> computer directly to the cable modem, he acquires an IP
> address in Comcast Subnet C. Then, everything works fine,
> including access to www.stolaf.edu and www.carleton.edu. He
> puts the Linksys router back in (which still has the IP
> address in Comcast Subnet B), and the problem returns.
> The problem IP subnets are completely consistent.
> Known WORKING IP Subnets: 188.8.131.52, 24.x Known
> NON-WORKING IP Subnets: 71.x, 73.x
> We have already attempted the usual troubleshooting and have
> eliminated user problems, computer problems, server problems,
> cable modem problems, and Linksys router problems.
> Traceroutes have been somewhat inconclusive since Onvoy
> blocks ICMP within its network.
> So, why just St. Olaf and Carleton services? We are on a
> shared physical link from Onvoy, though on different VLANs.
> Onvoy has verified everything they can (routing, packet loss,
> etc.) between them and us, and I'm not sure what additional
> questions I can ask of them to test. Suggestions?
> Maybe Comcast has a broken transparent proxy on part(s) of
> their network?
> But they have told us they have nothing like this anywhere on
> their network.
> Maybe there is some asymmetric routing somewhere, though all
> the investigation there has come up empty.
> A third possibility is some kind of packet loss, but there is
> little if any evidence of that.
> So, we are really at a loss and seek any suggestions you all
> might have. And a contact in Comcast network engineering
> would be especially useful to continue our troubleshooting.
> With thanks,
> Craig D. Rice Associate Director of
> Information Systems
> cdr at stolaf.edu Information and Instructional
> +1 507 786-3631 St.
> Olaf College
> +1 507 786-3096 FAX 1510 St.
> Olaf Avenue
> http://www.stolaf.edu/people/cdr Northfield, MN
> 55057-1097 USA
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