jdr@sloth.mlb.semi.harris.com (Jim Ray) (12/19/90)
We are currently experiencing problems with a few fiber links between
buidlings.
The links in question are connected via ODS 291 twisted pair box on
one net in one building to another ODS 291 twisted pair box ( using
a host port twisted pair connection ) which then connects to the remote
buidling via the fiber network port. The fiber then connects to the
remote building to a fiber tranceiver ( ODS 234 ) which then goes into
a TCL tranceiver and then to the remote lan.
--------------------- net a
| <-- tcl tranceiver
|
|_|-----|
| | ODS 291
| | Acts as a full repeater
--| |
| -------
| <------------twisted pair connecting host ports ( 10 base t )
|
---|-----|
| |
| | ODS 291 Acts as a full repeater
-------
|
| <------------ fiber
...
|
|
---
| | ODS 234 fiber tranceiver
----
|
|<--- tcl tranceiver
-------------------- remote lan a
Symptoms:
1) ping's with normal size packets work fine with about 1% loss
2) ping's with 500 byte packets have 10 % loss
3) ping's with 800 byte packets have 20 % loss
4) ping's with 1500 byte packets have 38 % loss
5) NFS of course does not like this at all -- since it opts for
large packet sizes.
6) Cisco routers connected to either side of lan a go into
hibernation mode for from 20-40 seconds or so every 5-10 minutes,
and occationally get interface resets ( keepalive time is 10
seconds -- so 3 at 10 seconds == 30 ).
7) Sniffer on either side see nothing out of the ordinary.
8) hosts pinging and being ping'd don't see high error rate ( in
netstat ).
This sounds like some type of retiming problem to me. Anyone have any
ideas?
--
Jim Ray Harris Semiconductor
Internet: jdr@semi.harris.com PO Box 883 MS 62B-022
Phone: (407) 729-5059 Melbourne, FL 32901