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AAUI adapters and 10/100(/1000) Ethernet switches

macclassic

Well-known member
If it helps my Allied Telesyn International adapter has a SQE heartbeat switch on one side re: http://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet/46786-12.html 

"The SQE heartbeat is designed to fix the problem in earlier versions of Ethernet where a host does not know if a transceiver is connected. It does this by providing about one usec of collision after the end of a transmission. The Ethernet controller in the host will record this event, and set a flag where the host can check on it.

Heartbeat/SQE is only returned from the transceiver to the host or unit to which it is connected. It is not put on the net.

Heartbeat must be disabled for repeaters or the net will go down, due to repeaters repeating the carrier. It does not matter what type of carrier, they just repeat it. If heartbeat is on, the following occurs:


    1. Repeater transmits to port A.
    2. Repeater stops transmit to port A.
    3. Port A returns heartbeat.
    4. Repeater indicates carrier.
    5. Repeater repeats carrier to all other ports and does a fragment extend which expands the 1 usec to 9.6 usec.
This in itself is not a problem, bandwidth is simply wasted. Some repeaters will count the heartbeat as a collision, and partition after 32 transmits to that segment.

At times, a host will record this event as a collision or framing error, and think the packet will have to be resent, wasting more bandwidth. It might even think that there are no good packets, and that all of them have errors.

If there are two stations with heartbeat on, then the extended fragments will collide with each other. After 32 transmits to the pair, both segments will shut down due to auto-partition. This will happen almost immediately after the first packet is sent, since they will be echoing back and forth the same fragment until one or both segments partition.

At times, a host will record the returned extended fragment heartbeat as a collision, framing error, or slot violation, and believe that it will have to retransmit, using more bandwidth.

Summary
  • The heartbeat is local only between the transceiver and some sort of host system.
  • If the host system is a computer, bridge, or router, the heartbeat is a function of whether the user enables it, and whether the software and hardware support SQE.
  • If the host system is a repeater, hub, or concentrator, the heartbeat must be off. This also includes concentrators with internal briges or routers.

IMG_1157.JPGIMG_1158.JPG

 

gsteemso

Well-known member
Huh! Very interesting! The article I was reading about the internals of UTP Ethernet (I think it was on Wikipedia, was about a week ago and I forget the details) mentioned a heartbeat, but made it sound like the function is inherent to every Ethernet link (the point-to-point part, not the whole network). Who knows, maybe on the newer stuff it is.

 

Paralel

Well-known member
I have the same Farallon AAUI ethernet adapater pictured, works perfectly on my PB 540c.

 
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gsteemso

Well-known member
I just made an interesting (if potentially embarrassing) discovery. Both of my dud Farallon transceivers have a teeny little slide switch recessed into one side. I’m guessing, from the relative ages of things people have posted pictures of in this thread, that it is likely a heartbeat on/off switch. I wouldn’t have discovered it save for the fact that both units have unsealed cases, i.e., some prior owner cracked the plastic welds that hold the clamshells on, so they fall apart if shaken around. The switch is so small and deeply recessed that you can’t tell it’s there with the shell on even when you already know about it. Alas, the two remain duds regardless of the switch position—looks like I’ve quite definitely been had.

Looking on the bright side, I picked up a second Asanté transceiver for about a dollar from the AS-IS bins at Re-PC, and it even works! SUCCESS!

 

CelGen

Well-known member
Man, I wish the recycling centers up north had a cable bin as amazing as RE-PC's. It's always an adventure rooting through that and you ALWAYS find something.

CRW_7281.jpg.68af7f7d464c7ee855312740573011a8.jpg


 

Paralel

Well-known member
Ha, I have the same glasses.

I like the idea of a cord bin. I maintain my own, but I'm always looking for rare cords. One absolutely never knows when they might need a given cable. I have run into some pretty bizarre situations in the past where I had a very odd cable that saved the day.

 
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Cory5412

Daring Pioneer of the Future
Staff member
I haven't ever had any problems with any AAUI transceiver. It's literally just an Ethernet cable with special ends. The two-port EtherWave ones are sort of weird, but really, it's just wired up as a hub.

It's also a bad idea to use a hub these days, so take that for what you wil. A couple of old Macs that you just want to chain together for whatever reason will probably not suffer that much.

I have connected my 6100 to the gigabit Ethernet ports on my CenturyLink/Qwest branded Actiontec VDSL2 modems with no problems. (I have also connected an Asante EN/SC Micro on the back of my PowerBook 180, both directly to the modem, and through the EtherWave on the 6100, with no troubles.)

The real problem with some networking kit begins with (usually) third party Ethernet cards and adapters that contain live equipment (Hubs, etc) that did not properly conform to Ethernet standards. So it probably depends on which particular machine or Ethernet adapter you used. The solution there tends to be to just connect those devices to a hub, through an Etherwave (heh) or to a 10/100 or 10-megabit switch.

Also, it is of course possible to just get non-working AAUI adapters, in the same way that an Ethernet cable can go bad.

 
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gsteemso

Well-known member
These Farallon ones of mine have numerous high-pin-count microchips on the board. Are you sure they are just glorified cables? The two factoids seem incompatible.

 

Cory5412

Daring Pioneer of the Future
Staff member
Which Farallon ones? The EtherWaves with two RJ45 connectors, or the simpler ones?

Even with more complexity than a simple cable, they're definitely media adapters for what's ultimately the same logical data transmission format, which just happens to have been carried over a few different physical media at the time.

 

gsteemso

Well-known member
As was mentioned briefly much earlier in the thread, these are not Etherwave units, just the plain-Jane Farallon AAUI transceivers with no special model name. I suppose all those chips could be line drivers and such. It just seemed like a surprising amount of complexity for something without, so far as I am aware, a microcontroller in it.

 

techknight

Well-known member
Well FWIW, Ethernet from the olden days, that I was aware of, had 2 standards. 568-A and 568-B. 

I only know B by heart, O/W-O-G/W-B-B/W-G-BR/W-BR

 

Unknown_K

Well-known member
I still have a decent kit to make Ethernet wires, tester, rj45 ends, cat5 spool, and even anti snag jackets.

 

rsolberg

Well-known member
Haha! Techknight, it's the 'A' configuration that's ingrained in my mind:

g/w, g, o/w, b, b/w, o, br/w, b.

Reverse the green and orange pairs for 'B'. 'A' on one end, 'B' on the other makes a crossover cable. I seem to remember the 'A' configuration was slightly superior for riser (vertical) runs, but I suspect that textbook was written in Cat-3 days.

 

NJRoadfan

Well-known member
Pretty much everything is wired for 568B these days. The most annoying job site I encountered was when a jerk wired RJ-45 jacks in a non-standard way, likely in a bid to maintain job security (he was fired about a month before I got there). I was wondering why none of the plugs I made worked, well the wiring at the switch end was.... interesting. Plus he didn't even punch down all the pairs! He only wired two pairs and if I recall, they weren't even matched twisted pairs. Ugh.

 

techknight

Well-known member
that only makes things 50 million times worse. haha. 

Especially if they did not match the pairs correctly, then we get crosstalk on adjacent-like signals. WEEEEEEE

 
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