RE: Problems with AT&T

["Truman, Michelle, SALES" <mtruman () att com>]

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:
> > Anybody here seeing problems with AS7018 ?
>
> ...
...
>  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?