[98306] in North American Network Operators' Group
RE: Seeking Comcast Contact: need to troubleshoot packet loss and/or asymmetric routing issue between Comcast & Onvoy
daemon@ATHENA.MIT.EDU (Durand, Alain)
Thu Aug 2 09:45:01 2007
Date: Thu, 2 Aug 2007 09:43:35 -0400
In-Reply-To: <46B1DC65.7060405@stolaf.edu>
From: "Durand, Alain" <Alain_Durand@cable.comcast.com>
To: "Craig D. Rice" <cdr@stolaf.edu>, <nanog@merit.edu>
Errors-To: owner-nanog@merit.edu
I've forwarded your message to the appropriate team within Comcast.
- Alain.=20
> -----Original Message-----
> From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On=20
> Behalf Of Craig D. Rice
> Sent: Thursday, August 02, 2007 9:30 AM
> To: nanog@merit.edu
> Subject: Seeking Comcast Contact: need to troubleshoot packet=20
> loss and/or asymmetric routing issue between Comcast & Onvoy
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> For four months dozens of our users who are Comcast=20
> subscribers have had difficulty reaching St. Olaf College's=20
> and Carleton College's network services.
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> We have worked through everything we can think of with our=20
> Onvoy (regional
> ISP) network engineers. We have isolated the problem a couple=20
> of Comcast's IP subnets, but need a contact within Comcast to=20
> further troubleshoot.
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> The behavior in a nutshell:
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> --
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> User A on Comcast Subnet B browses to www.stolaf.edu (http or=20
> https, other web sites on-site and @carleton.edu behave the=20
> same). Our access_log shows an initial "GET /" of our=20
> homepage, then very slow (if any) subsequent requests (for=20
> our stylesheet or homepage images). Ping's look fine;=20
> traceroute's look as reasonable. Telnet's to port 80 and=20
> other services do seem to respond, albeit very slowly.
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> User A has the same problem with access @carleton.edu but can=20
> access everything else (including other Onvoy customers)=20
> without any trouble whatsoever.
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> If User A then removes his Linksys router and connects his=20
> computer directly to the cable modem, he acquires an IP=20
> address in Comcast Subnet C. Then, everything works fine,=20
> including access to www.stolaf.edu and www.carleton.edu. He=20
> puts the Linksys router back in (which still has the IP=20
> address in Comcast Subnet B), and the problem returns.
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> The problem IP subnets are completely consistent.
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> Known WORKING IP Subnets: 75.72.0.0, 24.x Known=20
> NON-WORKING IP Subnets: 71.x, 73.x
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> --
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> We have already attempted the usual troubleshooting and have=20
> eliminated user problems, computer problems, server problems,=20
> cable modem problems, and Linksys router problems.=20
> Traceroutes have been somewhat inconclusive since Onvoy=20
> blocks ICMP within its network.
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> So, why just St. Olaf and Carleton services? We are on a=20
> shared physical link from Onvoy, though on different VLANs.=20
> Onvoy has verified everything they can (routing, packet loss,=20
> etc.) between them and us, and I'm not sure what additional=20
> questions I can ask of them to test. Suggestions?
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> Maybe Comcast has a broken transparent proxy on part(s) of=20
> their network?=20
> But they have told us they have nothing like this anywhere on=20
> their network.
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> Maybe there is some asymmetric routing somewhere, though all=20
> the investigation there has come up empty.
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> A third possibility is some kind of packet loss, but there is=20
> little if any evidence of that.
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> So, we are really at a loss and seek any suggestions you all=20
> might have. And a contact in Comcast network engineering=20
> would be especially useful to continue our troubleshooting.
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> With thanks,
> Craig
> --=20
> Craig D. Rice Associate Director of=20
> Information Systems
> cdr@stolaf.edu Information and Instructional=20
> Technologies
> +1 507 786-3631 St.=20
> Olaf College
> +1 507 786-3096 FAX 1510 St.=20
> Olaf Avenue
> http://www.stolaf.edu/people/cdr Northfield, MN =20
> 55057-1097 USA
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