Q:Whats the purpose of Inter Repeater Links?

Q:Whats the purpose of Inter Repeater Links?

Post by Konstantin Ryvki » Wed, 04 Feb 1998 04:00:00



Hi All,

I have read in plenty of manuals that 5-4-3 rule must be followed while
connecting 10Base2 (and 10Base5) segments.
And only 3 of them can be populated, the others are so called IRL.

Of course I understand that this is the way the standard goes, but what's
the purpuse of these IRL?
Why should not I populate the rest 2 segments?
What's the physical (logical) limitation?

Anyone, can you explain me.
Or just give the link to the reference where the question "Why" is answered.

Thanks in advance for Your time.

If (Q==FAQ) then sorry();

--
Konstantin Ryvkin

St. Petersburg, Russia

 
 
 

Q:Whats the purpose of Inter Repeater Links?

Post by G. Herrmannsfel » Wed, 04 Feb 1998 04:00:00



>I have read in plenty of manuals that 5-4-3 rule must be followed while
>connecting 10Base2 (and 10Base5) segments.
>And only 3 of them can be populated, the others are so called IRL.
>Of course I understand that this is the way the standard goes, but what's
>the purpuse of these IRL?
>Why should not I populate the rest 2 segments?
>What's the physical (logical) limitation?
>If (Q==FAQ) then sorry();

Maybe Q==FAC, but anyway,

In the old days, there was coaxial ethernet and FOIRL, Fiber Optic Inter
Repeater Link.  You can put multiple taps on a coax cable, but not an an
optical fiber.  Collision detect is slightly slower on coax, compared to
cables with separate transmit and receive lines, like fiber and twisted
pair.  In a twisted pair net, all segments count as IRL.  

In any case, that is the rule if your 10base5 segments are 500m long,
and with 50m AUI cables.  If not, you may be able to have five segments,
and still satisfy the rules.  If you really want to know, you have to
use the Model 2 rules.

If you use only 10baseT, even with 150m cables, you can still satisfy
the model 2 rules with six segments and five repeaters.  (The 6-5-0 rule?)

If you have FOIRL longer than 500m, or 10baseFP, 10baseFB, or 10baseFL,
you should also use model 2 rules.  

With a long 10baseFL cable, you might only be allowed one repeater!

I hope this helps,

-- glen

 
 
 

1. Q:Inter-repeater link/DECrepeater 90C

I an wanting to configure a 150m piece of thinwire cable as an
inter-repeater link.  At one end I have Isolan gear - and EC/4
with a coax line card in it.

The other end is not yet purchased, but I am thinking of a
DECrepeater 90C :

|
|--EC/4 ------------------------------- DECrepeater 90C
|                                        |  |  |  |
|                                        |  |  |  |
campus                                  thinwire strands to various
backbone                                parts of a building.

Can someone confirm that this will work, and in particular that a
DECrepeater 90C can be used as one end of an inter repeater link ?

Thanks,
________________________________________________________________________________
Martyn Brown, Senior Computer Consultant          Phone: 64.3.3252811 extn 8012
Centre for Computing and Biometrics                 Fax: 64.3.3252944
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