yeah, those are almost sure to be boxes of the vendor-type that is de-prioritizing icmp control messages to the max. That will be rememdied, but not sure exactly when. It does not affect actual data flow through the network. Just trace ttl-exceeded response (you can't ping those boxes anyway, so it doesn't matter, but they would be dropping those also). Michelle Michelle Truman CCIE # 8098 Principal Technical Consultant AT&T Solutions Center mailto:mtruman@att.com VO: 651-998-0949 w 612-376-5137 -----Original Message----- From: Brennan_Murphy@NAI.com [mailto:Brennan_Murphy@NAI.com] Sent: Thursday, March 20, 2003 6:13 PM To: Truman, Michelle, SALES; nanog@merit.edu Subject: RE: Problems with AT&T 12.123.196.10 12.123.17.30 12.122.10.74 Seems like one or all of those 3 boxes routinely drop ICMP packets. Still trying to determine if other traffic types are dropping as well. -----Original Message----- From: Truman, Michelle, SALES [mailto:mtruman@att.com] Sent: Wednesday, March 19, 2003 3:39 PM To: nanog@merit.edu Subject: RE: Problems with AT&T If someone can identify what you are actually seeing, I'll check into it. If you are experiencing drops or slow traces, only through the core, there is an issue with excessive de-prioritization of ICMP control message with a particular router type (vendcor) in the core. End to end data flow has not seemed to be affected but trace and ping core latencies are looking very wierd. I've been asking customers to use trace only for path detail and to use end to end ping for any performance data. Yes, the core is MPLS enabled. Diffserv acted on only at the edges though. Michelle Michelle Truman CCIE # 8098 Principal Technical Consultant AT&T Solutions Center mailto:mtruman@att.com VO: 651-998-0949 w 612-376-5137 -----Original Message----- From: brett watson [mailto:brett@the-watsons.org] Sent: Wednesday, March 19, 2003 1:48 PM To: nanog@merit.edu Subject: Re: Problems with AT&T On Wednesday, Mar 19, 2003, at 12:28 America/Phoenix, Sean Donelan wrote:

On Wed, 19 Mar 2003, German Martinez wrote:

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Anybody here seeing problems with AS7018 ?

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If you report it to AT&T, they seem to get it fixed; but then the problems re-appear a few days later. I'm guessing that packet size is relevant, but I haven't spent much time trying to troubleshoot it.

isn't at&t heavily MPLSed? maybe something to do with mpls tunnels, or diff-serv marking?