wasc@cgch.UUCP (Armin Schweizer) (08/23/89)
IMPORTANT: read this to save you days of work!
Dear colleagues!
With our Hewlett Packard 4972A LAN analyzer we are very happy,
since it allows us to monitor our Internet- and DECnet- networks
very accurately.
However we had a hard time, since we couldn't get our DECnets
running over Ethernet clean of collisions (we thought). We measured
and replaced whatever we could --> no success --> frustration.
Now we found, that our LAN analyzer is indicating collisions
when there are none! (so the NCP on the VAX machines told the
truth).
Hewlett Packard informed us, that this is indeed not due
to a defective hardware, but will show up when you are
measuring at DELNIs.
We have further investigated on this:
- when will this problem be removed?
- is the reason DECs incompatibility with the IEEE 802.3
heartbeat? (DEC says, they will move to IEEE soon!?!)
- is the problem showing up in DELNIs only? Or also
at H400x etc.?
Does anybody know a cure or workaround for this problem?
Kind regards
Armin
Armin R. Schweizer, CIBA-GEIGY AG, R1045.P.06, WRZ
4002 Basel / Switzerland
phone: -41-61-697'79'46ron@ron.rutgers.edu (Ron Natalie) (08/24/89)
The problem is that multiport transcievers like the DELNI will blip all the SQE lines when generating the heartbeat for any of the ports. Since the HP is just sitting their passively waiting for collisions, it can't really tell (well, I guess it could) that it was seeing someone else's heartbeat. I'm not sure about DELNI's, but I believe you can solve this problem on some boxes by making sure the actual transceiver the DELNI is connected to does not have heartbeat turned on. Noticeably, since we have this problem a lot, we carry around a two transciever Ethernet segment that we plug the stand alone units into for connection to the HP analyzer. -Ron
meggers@orion.cf.uci.edu (mark eggers) (08/24/89)
Another way to shut off the heartbeat is to plug in an Ethernet 'loopback' connector into the network port. Then tell the DELNI that it is attached to a network. No heartbeat from the network - no heartbeat on the DELNI. The connector should have been a part of your DELNI package. We found out about this at Notre Dame when we started to plug DEMPRs into standalone DELNIs. Performance was terrible. Connecting the loopback connector and switching the DELNI to network connected mode solved the problem.
eric@ists.ists.ca (Eric M. Carroll) (08/24/89)
In some randomly numbered article meggers@orion.cf.uci.edu (mark eggers) writes: >Another way to shut off the heartbeat is to plug in an Ethernet 'loopback' >connector into the network port. Then tell the DELNI that it is attached >to a network. No heartbeat from the network - no heartbeat on the DELNI. > >The connector should have been a part of your DELNI package. We found out >about this at Notre Dame when we started to plug DEMPRs into standalone >DELNIs. Performance was terrible. Connecting the loopback connector and >switching the DELNI to network connected mode solved the problem. Now this is fascinating. About 6 months ago I inherited a problem where I had 3 Cabletron repeaters pluged into a DELNI (a Cabletron MT-800) in LOOPBACK mode with heartbeat (SQE) OFF. There is no known chapter and verse outlawing it, but everyone I discuss this with says *yuck*. Cabletron said it should work. But I consistently achieved 50% packet loss rates through two of the three legs. I eliminated all possible combinations of cables, repeaters fiber modems and DELNIs. Nothing worked. Finally I eliminated the DELNI and replaced it all with a multimedia multiport repeater. That solved my problem.
hedrick@geneva.rutgers.edu (Charles Hedrick) (08/27/89)
DELNI is a specific DEC product. I would prefer to have that term used only for actual DELNI devices, made by DEC. The generic term is multiport transceiver, or if you want to abbreviate, simply multiport. If we start using DELNI as a generic term, then it's going to be ambiguous whether people are reporting problems that are specific to the Digital(TM) brand DELNI multiport or not.
ron@hardees.rutgers.edu (Ron Natalie) (08/27/89)
DEC's documentation on the DEREP warns against plugging it into DELNI's. Sure enough they're right. It'll run plugged into a cabletron MT-800, but not into a DELNI. (BTW the repeater indicates that it wants the heartbeat, it lights the red light if you don't turn it on, but this appears to have no effect on the unit's operation). -Ron
smb@ulysses.homer.nj.att.com (Steven M. Bellovin) (08/28/89)
In article <Aug.27.09.04.01.1989.1047@hardees.rutgers.edu>, ron@hardees.rutgers.edu (Ron Natalie) writes: > DEC's documentation on the DEREP warns against plugging it into > DELNI's. Sure enough they're right. It'll run plugged into > a cabletron MT-800, but not into a DELNI. It would probably work if the DELNI was plugged into a no-heartbeat transceiver, i.e., the DEC H4000-BA. The DEMPR documentation specifically requires such a transceiver be used, in fact.
meggers@orion.cf.uci.edu (mark eggers) (08/28/89)
As has been pointed out, this problem only occurs with the DELNI multiport
transceiver. The problem is that you cannot configure heartbeat as you
would like.
In the DEC manuals, there is a warning about plugging DEREPs into DELNIs
(repeaters into multiport transceivers). Since DEMPRs (multiport thinwire
Ethernet repeaters) count as a repeater [I think], plugging a multiport
thinwire repeater into a DELNI causes problems unless the DELNI is plugged
into a nonheartbeat generating transceiver (H4000 from DEC is one example).
Since the cascading of up to eight DEMPRs on a DELNI is part of the DEC
wiring plan, the fact that this won't work without either attaching the
DELNI to an H4000 transceiver (documented) or using a loopback connector
on the ninth port (UNDOCUMENTED) is a bit annoying.
Please note that the above incompatibilty (hearbeat vs. no heartbeat) is
only a problem with DEC DEMPRs (thinwire multiport repeaters), and DELNIs
(multiport transceivers) as far as I know. The corresponding Cabletron
setup (MR-9000s and MT-800s) can be configured to work (heartbeat is
configurable on the ninth port).
Disclaimer: UCI is not responsible for the nonsense that I may post
on the net. I am just a user of both DEC and Cabletron
equipment. Thanks goes to the DEC technical support
pointing out what I needed to do to get things running.
/mde/