| Title: | FDDI - The Next Generation |
| Moderator: | NETCAD::STEFANI |
| Created: | Thu Apr 27 1989 |
| Last Modified: | Thu Jun 05 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2259 |
| Total number of notes: | 8590 |
In this FDDI configuration we experience 20-30 MAC crc errors pr. hour.
Is this acceptable, or should we look for bad cables,interfases etc. ?
If I look with an analyzer, and only look for bad crc, 95% of the bad crc
sources, origens from the "left" ethernet. Since the DB900 makes a new crc, it
must be the DB900, that is considered the source.
Perhaps 4 % of the " bad crc " comes from the left DECbridge900 down stream
neighboer, ( ALPHA H ).
I suspect that, perhaps, ALPHA H is curupting the packets from the DB900.
In this config, all the alpha's are in a cluster. Once in a while, some of the
members, looses the connection, to the cluster, ( 0 - 10 times a day )
I been asked, to check out the network. It looks fair enough, but...
Im not sure, if 20-30 crc errors pr hour is any problem to investegate.
A A A A A A A A
L L L L L L L L
P P P P P P P P
H H H H H H H H
A A A A A A A A
H 5 7 1 2 3 4 6
H H
U DECconcentrator_900 <----fiber------>DECconcentrator_900 U
B DECbridge_900 <----------fiber------------>DECbridge_900 B
DECREP 9 E E 9
900 0 T T 0 3 X DECREP
0 H H 0 900
E X 4 E
R R X 4
N N
E E
T T
The Alpha H a 2100/500 and is a PC server, and the clients are on the ethernet.
Alpha 1-7 is 3000/300 and 400. and mostly used as workstations.
-------------------
Jan.
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1798.1 | NETCAD::B_CRONIN | Tue Sep 05 1995 18:42 | 26 | ||
Hi Jan,
Yes, 20-30 errors per hour is very bad performance. It appears that
your FDDI analyzer has determined that the packets from the DB900
have crc errors. A way to confirm that is to look at the MAC that
is immediately downstream of the DB900. If that stations's CRC
counter is ticking, then the error is located between between the
DB900 and that MAC. Your suspicion that another station may be causing
the errors is also correct, as each station in the ring could corrupt
the frame as it repeats it. If that immediate downstream CRC counter
is not ticking, then the errors are happenning elsewhere, and you
need to look at each station's CRC counter and see if you can find the
one that is ticking.
The error will be in the path between the MAC counting the error, and
that MACs immediate upstream neighbor MAC. It might then be as simple
as a dirty cable, or, a bad concentrator port.
You may also be seeing link errors as well as CRC errors. Look at
the PHY counters, and see if there are any connections rejected
any LEM Errors, or any Link Error Estimates that are not equal to 15.
Any of those things may also be a clue as to the location of the
errors.
Good Luck
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