delni networking questions
mor...@fnalv1.fnal.gov
Does a Delni count as a repeater when figuring out ethernet rules?
Beyond that let me explain what I am about to try and ask the general
feeling about how good of an idea it is. I have an 8 port twisted pair
repeater hooking several of my computers together and to the outside
world. I also have two decserver 200s, one of which is currently
connected (and full) via a 10bT to AUI MAU (ACCTON if that makes any
difference).
When I first got the 8 port repeater I wasn't given a cross-over
cable to connect it to the network at large. On a hunch I plugged
the wall cable into an etherwave, the AUI end of the etherwave into
an Alpha and the other twisted pair from the etherwave into the
repeater. IT WORKED! It also had the side effect of giving me one
more connection.
repeater
wall_______etherwave____| | | | | | | |
| | | | | | | | |
computer 6 computers and DS200
On the other side of the wall are 11 x-terminals, a couple of
computers, our DECnet and Internet connections. It strikes me as a
BAD (TM) idea to have all that network traffic going through the
etherwave.
Well I did get a crossover cable, but now I would have to give up
a slot on the repeater and what I want to do is add another DECserver.
Somewhere in the bureaucracy (I hope) is another repeater that will
permanently end this problem but in the meantime (i.e. 1-6 months)
I would like to use the MAU to hook one of the repeater ports to the
Delni, and then connect the Delni to the two DS200s and to a computer.
repeater Delni
wall___| | | | | | | |_____| | | |
6 computers 2 DS200s and computer
Comments, suggestions, flames?
Thanks for any input you can give me.
Robert Morphis
sys...@physics.niu.edu
Malcolm Dunnett
rkoe...@csc.com (Robert Koehler) writes:
>
> : Does a Delni count as a repeater when figuring out ethernet rules?
>
> No. It counts as 8 trasceivers. If you're connecting it to a thick-wire,
> leave space between it and any other taps as if it were 8 taps.
I don't believe this is true. The tap spacing has to do with the
electrical characteristics of the physical connection to the wire, and the
reflections it generates. The type of equipment attached to the tap should
be irrelevant.
>
> I'm not sure why, but if your not using the female port at the end the DELNI
> is suppose to work better with the port enabled and one of those terminator
> blocks pulgged into it than with it disabled.
>
This is only true if you are trying to hang 802.3 repeaters off one of the
DELNIs ports. The problem is that the DELNI in local mode sends the SQE test
(heartbeat) signal out on all its ports, repeaters don't expect this signal
and treat the reception of it as a collision ( the same is true if you attach
the DELNI to a backbone using a transceiver with SQE enabled ). By putting
the DELNI into global mode and attaching a loopback connector to the
uplink port you simulate a backbone attachment via a transceiver without
SQE and thus avoid the problem.
--
=============================================================================
Malcolm Dunnett Malaspina University-College Email: dun...@mala.bc.ca
Computer Services Nanaimo, B.C. CANADA V9R 5S5 Tel: (604)755-8738
mor...@fnalv1.fnal.gov
>mor...@fnalv1.fnal.gov wrote:
>: hello,
>
>: Does a Delni count as a repeater when figuring out ethernet rules?
>
>No.
good
>I'm not sure why, but if your not using the female port at the end the DELNI
>is suppose to work better with the port enabled and one of those terminator
>blocks pulgged into it than with it disabled.
ah, I was wondering why it was configured that way... (The female port had
not been used but I am using it now.
Thanks for the info.
I went ahead and hooked it up as diagrammed in my last post and reproduced
below:
repeater DELNI
wall___| | | | | | | |_____| | | |
| | | | | | | | |
6 computers 2 DS200s and computer
with the repeater being hooked via a utp to aui transciever to the
aforementioned female port of the Delni. The DS200s work just fine,
but the computer doesn't boot, it tests everything then sends out
a request for a boot (the boot node is on the repeater) and sits there
retrying occasionally.
so I tried something I didn't think would work...
repeater DELNI
wall___| | | | | | | |_____| | |
| | | | | | | |
5 computers| 2 DS200s
|
|(utp)
etherwave
| |
|(utp) |(aui)
computer computer(this being the computer that had been
hooked to the DELNI)
which worked just fine, now that I think about it I guess
it makes some sense that it would work.
Any ideas as to why the computer (DEC 3000 m 600 AXP running VMS) wouldn't
boot through the DELNI?
>Bob Koehler | CSC/SSD/MITG
>rkoe...@csc.com |
Ron Natalie
network issues of that. A DELNI doesn't count as a repeater
(it isn't one). It's only configuration issue is that it
eats 5 meters off your AUI cable length and DEC doesn't recommend
cascading more that two of them together.
-Ron
Robert Koehler
: hello,
: Does a Delni count as a repeater when figuring out ethernet rules?
No. It counts as 8 trasceivers. If you're connecting it to a thick-wire,
leave space between it and any other taps as if it were 8 taps. If you're not
connecting it to a thick-wire, just consider it like a set of 8 AUI-thickwire
transcievers tapped an isolated thick-wire, except you don't have to worry
about storing the cable or having bad taps.
I'm not sure why, but if your not using the female port at the end the DELNI
is suppose to work better with the port enabled and one of those terminator
blocks pulgged into it than with it disabled.
------------------------------------------------------------------------------
Bob Koehler | CSC/SSD/MITG
rkoe...@csc.com |
Terry Kennedy, Operations Mgr.
> This is only true if you are trying to hang 802.3 repeaters off one of the
> DELNIs ports. The problem is that the DELNI in local mode sends the SQE test
> (heartbeat) signal out on all its ports, repeaters don't expect this signal
> and treat the reception of it as a collision ( the same is true if you attach
> the DELNI to a backbone using a transceiver with SQE enabled ). By putting
> the DELNI into global mode and attaching a loopback connector to the
> uplink port you simulate a backbone attachment via a transceiver without
> SQE and thus avoid the problem.
DELNI's are strange beasts. There isn't a category for "transceiver fanout
units" in Ethernet II, and I don't think there is in 802.3 either (and in any
case, the DELNI is not an 802.3 device).
They made sense when backbones were thinkwire and transceivers were multi-
hundred-$ H4000's that were huge. These days it's trivial to get $24 mini
transceivers (like the Allied Telesyn MX10 and MX20) and use either BNC thin-
wire or twisted pair and an inexpensive hub.
I've seen all sorts of abberant Ethernet operation when DELNIs are used,
which went away when the network was modified to eliminate the DELNI(s).
Terry Kennedy Operations Manager, Academic Computing
te...@spcvxa.spc.edu St. Peter's College, Jersey City, NJ USA
+1 201 915 9381 (voice) +1 201 435-3662 (FAX)
Ron Natalie
: mor...@fnalv1.fnal.gov wrote:
: : hello,
: : Does a Delni count as a repeater when figuring out ethernet rules?
: No. It counts as 8 trasceivers. If you're connecting it to a thick-wire,
: leave space between it and any other taps as if it were 8 taps.
There is absolutely *NO* reason to do this. A DELNI isn't a tap, it's a
AUI fanout.
-Ron
Bob Lombard
r...@topaz.sensor.com (Ron Natalie) wrote:
>Robert Koehler (rkoe...@csc.com) wrote:
>: mor...@fnalv1.fnal.gov wrote:
>: : hello,
>
>: : Does a Delni count as a repeater when figuring out
ethernet rules?
No.. it is an AUI fan-out box. It does not count as a repater or
a tap.
Michael D. Voight
a Delni with some terminal servers. The Black box connects to a
CISCO 2500 router thru 10BASET. The PC can ping VAX and router with
no problem, the router can ping the PC with no problem and the
VAX can ping the PC with no problem. The router goes to the internet
and it can be pinged OK from the outside world. The DELNI is on a
Thicknet backbone and there are no problems between any other systems,
except the VAX and the CISCO. They experience 80-90 percent packet
loss when pinging each other.
Any ideas??
Al Deshotel
<<SNIP>>They experience 80-90 percent packet
>loss when pinging each other.
Something has a SQE heartbeat turned on somewhere. Or a bad cable.
DELNIs are pretty reliable and are a more or less transparent
repeater. I've got about 50 or so of them and don't have any
problems. However, there are several variants on them.
obe...@icaen.llnl.gov
desh...@hic.net (Al Deshotel) writes:
>Something has a SQE heartbeat turned on somewhere. Or a bad cable.
>DELNIs are pretty reliable and are a more or less transparent
>repeater. I've got about 50 or so of them and don't have any
>problems. However, there are several variants on them.
Please!!! DELNIs are NOT repeaters in any sense of the definition. They may be
though of as a multi-port transceiver, but never as a repeater.
R. Kevin Oberman
Energy Sciences Network (ESnet)
National Energy Research Supercomputer Center (NERSC)
Internet: obe...@es.net +1 510-422-6955
Konstantin Olchanski
>
> Please!!! DELNIs are NOT repeaters in any sense of the definition. They may be
> though of as a multi-port transceiver, but never as a repeater.
Please!!! Why a DELNI is not a repeater? What makes it different
from a "normal" repeater?
C.O.
Fred Mudgett
the answer. As I remember from a ethernet class that I attended a
repeater has a funcion of extending a ethernet segment under certian
conditions the delni (as was so eloquently put) is just a amplifier and
tranciever. That means it has no ability to "think" about the packets
that it moves the repeater on the other hand has that ability.
Fred
obe...@icaen.llnl.gov
It's not different from a "normal" repeater. It simply is not a repeater. A
DELNI is not a repeater because it does not have anything in common with a
repeater execpt a power cord and one connector (a repeater never has a male AUI
connector but may have female ones.).
It does not perform any repeater functions including the basic one of
connecting network segments. It does not do retiming or preamble re-generation.
It does not jam on collisions. (Nor is there any reason it should do any of
these functions). It does not repeat. A cat is not a horse and a DELNI is not a
Ron Natalie
: > Please!!! DELNIs are NOT repeaters in any sense of the definition. They may be
: > though of as a multi-port transceiver, but never as a repeater.
: Please!!! Why a DELNI is not a repeater? What makes it different
: from a "normal" repeater?
Because it isn't. It performs a different function entirely with different
configuration rules.
A repeater is a device that connects two lan segments together. The
topology looks like this. A repeater connects to each segment as if
it were a host, and propagates the signals accross.
|--Ethernet----------+-------| |-------+------------Ethernet---|
TRANSCEIVER TRANSCEIVER
| |
|---------REPEATER-------|
A DELNI, is a multiport transciever. It essentially is analogous to
a one of those strips that allows you to plug 8 appliances into it and
in turn into one electrical outlet...
A DELNI connects to another transciever and lets multiple hosts to all
beieve they are plugged directly into the transceiver that the DELNI
is connected to.
|--Ethernet----------+-------|
TRANSCEIVER
|
|
+---------+
| DELNI |
+---------+
| | |
HOST HOST HOST
The general rule on repeaters is that you must design your net such
that no host has more than two repeaters between it and any other host.
Also remember to shut off the SQE Test (heartbeat) on the transcievers
you plug the repeater into. (Also, you do not want to make cycles with
repeaters, i.e. parallel repeater paths).
The configuration rules on the DELNI is that it eats about 5 meters off
the allowed (typicall 50m) transceiver cable length of the devices
plugged into it.
-Ron
Robert Koehler
: In article <4eo5i7$s...@lll-winken.llnl.gov>, obe...@icaen.llnl.gov writes:
: >
: > though of as a multi-port transceiver, but never as a repeater.
A repeater gets a packet off one line, reconditions it, and transmits it to
another line, introducing delay between the incomming and outgoing packets.
It allows network wire length longer and number of stations larger than single
segment. Repeaters commonly connect like or different media (thickwire,
thinwire, 10bT). If one segment connected to a repeater goes bad, the other
segments are often protected.
A DELNI operatates as if it were a collection of transceivers connected by an
unseen thickwire. As such it copies the incomming signal as is to each
outgoing port, adding essentially no delay. It does provide for an increase
in network wire lenght or number of stations. Typically transcivers also
change media format, such as AUI to thinwire or AUI to thickwire. A DELNI is
slightly unusual in that it does not change media, but it acts as if the
thickwire were there. If one connection to a DELNI goes bad, all the stations
may see it.
Ron Natalie
: A DELNI operatates as if it were a collection of transceivers connected by an
: unseen thickwire. As such it copies the incomming signal as is to each
: outgoing port, adding essentially no delay. It does provide for an increase
: in network wire lenght or number of stations. Typically transcivers also
: change media format, such as AUI to thinwire or AUI to thickwire. A DELNI is
: slightly unusual in that it does not change media, but it acts as if the
: thickwire were there. If one connection to a DELNI goes bad, all the stations
: may see it.
Actually, a DELNI just multiplexes 8 host AUI ports into a single AUI port
with an option that you can just loop the network side around (but that part
is no different really from sticking the funny loopback with the green led
into a host).
_Ron
zrep...@alpha2.curtin.edu.au
>>
>> Please!!! DELNIs are NOT repeaters in any sense of the definition. They may be
>> though of as a multi-port transceiver, but never as a repeater.
>
>
> from a "normal" repeater?
A DELNI is just a multi-port amplifer with a gain of 1. A repeater
"knows" what a valid packet looks like, and will not respond
to garbage and noise. If the noise level is high enough to trip
the squelch circuits, a DELNI will share the grief around. A repeater
also drops a few bits from the PLL run-in at the beginning of the
packet, so too many repeaters in the path, and the data seperators
can't sync up in time to decode the packet from the wire.
~Paul
Kevin Oberman
> A DELNI is just a multi-port amplifer with a gain of 1. A repeater
> "knows" what a valid packet looks like, and will not respond
> to garbage and noise. If the noise level is high enough to trip
> the squelch circuits, a DELNI will share the grief around. A repeater
> also drops a few bits from the PLL run-in at the beginning of the
> packet, so too many repeaters in the path, and the data seperators
> can't sync up in time to decode the packet from the wire.
I think Paul knows better than this. Everything he says about a DELNI is
true, but I think he just got some wires crossed on the repeater side.
A repeater has no concept of a packet nor memory to store one. It is a
bit level device with "knowlege" of preamble and start-of-data (SFD). If
it does not see the 1-0-1-0-1-... pattern of a preamble, it ignores the
signal, but once it sees a preamble and SFD (two "1"s in a row), it will
forward noise as well as a DELNI. That means packets that are trashed by
bad hardware or late collisions or any other means will be forwarded
"as-is".
A repeater can regenerate preamble and has sufficient bit storage to
allow for this. So, while preamble bits are "eaten", at least some are
put back in. It also processes collisions and propagates them through
jams.
See 802.3, section 9.6 for several pages of just what a repeater does.
(It's actually not too ugly, as standards go, to understand and makes
interesting reading if you have access to it.)
I posted the original "a DELNI is not a repeater" message and Paul's
post does not disagree, but it might confuse some people as to just what
the capabilities of a repeater are. IT almost makes it sound like a
bridge.
--
R. Kevin Oberman
Energy Sciences Network (ESnet)
National Energy Research Supercomputer Center (NERSC)
EMAIL: obe...@es.net Phone: +1 510 422-6955