Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!pacbell.com!ames!dftsrv!nssdcb.gsfc.nasa.gov!lanmaint
From: lanmaint@nssdcb.gsfc.nasa.gov (Dave Yoest)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: Serial problems with 8.0(6) to 8.1(*)
Message-ID: <4150@dftsrv.gsfc.nasa.gov>
Date: 10 Dec 90 13:01:19 GMT
References: <30777@boulder.Colorado.EDU>
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In article <30777@boulder.Colorado.EDU>, asp@uunet.UU.NET (Andrew Partan) writes...
>We switched from 8.0(6) to 8.1(14) about 6 months ago and have been
>having serial line problems on 1 T1 ever since.  This was a T1 that had
>been working just fine for over a year prior to this.
> 
>We first thought that it was a serial line problem or perhaps bad

 [Body of message deleted]

>All to *no* avail - we are still getting errors - to the tune of 100 -
>1000 (nearly) *every* 5 minutes.  Most of these error are cisco abort
>errors.
> 
>cisco has been of little or no real help.  They keep on saying that it
>must be either the T1 or the CSU/DSUs.  [The only bug report number
>that has ever been given to me by cisco for this problem is 901120235.
>I almost never get a number for any of the calls that I make.]
> 
>Does anyone have any suggestions?  Or have similar problems?
> 
>Thanks,
>	--asp@uunet.uu.net (Andrew Partan)
>	ASN.1 Object Identifier: "{joint-iso-ccitt mhs(6) group(6) 157}"



I had a somewhat similar problem with my CGS boxes running 8.1 over a
T1 microwave circuit using Phoenix 1536 DSU's. When I first attempted
to bring this connection up, I had problems somewhat similar to the
ones you described. The T1 circuit passed BERT (Firebird 6000) tests
with flying colors (no errors in 3 days), and worked fine with a 
Proteon router, but would not work satisfactorily with the cisco. I
spoke with some other people here who use ciscos with Phoenix 1536's
and noted that they were using the 1344Kbps clock speed instead of
1536 Kpbs on their DSU's. I tried the 1344Kbps setting and everything
worked great!

I contacted cisco customer service (cs@cisco.com) with this 
information and received an immediate response. In summary, cisco 
uses HDLC over the T1, and at 1536Kbps the cisco does not maintain
a minimum 1's density over the T1. By reducing the data rate to 1344
Kbps bit stuffing is performed and everything works fine.

Cisco also suggested that I could operate at 1536 if I could invert
the data stream, thus maintaing a minimum 1's density.

I haven't ever tried the cisco phone support, but I have been 
exceptionally pleased with the response time and quality of the
email support (cs@cisco.com). I have used cisco cs several times
in this manner and in all cases I received a response within 2 hours.
I wish all the companies I deal with were as good as this.....


Dave Yoest
LAN Section Supervisor
NASA/Goddard Space Flight Center
Greenbelt Md.

dyoest@zaphod.gsfc.nasa.gov
dyoest@128.183.4.5