• Subject: Re: Errors on Token Ring line
  • From: Larry Bolhuis <lbolhui@xxxxxxx>
  • Date: Wed, 12 Jan 2000 07:29:46 -0500
  • Organization: Arbor Solutions, Inc

Ray Peterson wrote:
> I think the difference you are seeing is probably just based on the way 
>things are
> actually cabled to the MSAU.  Since each port/adapter has to pass the token 
> if the destination is the next adapter it will perform better than if it has 
>to be
> passed thru three of four intermediate ports.

  I must differ! If the passing of tokens from station to station across 4
stations cut the speed in half, big token-ring networks would barely move. This
is clearly not the case.  I have seen throughput of just below 16MB in networks
with over 100 stations, all passive MAUs and easily 1 mile of total ring length.

> The good news is this can be easily improved by swapping
> out the MSAU for a Token Ring Switch.

  While this is true in larger networks, unless the 5 stations in this network
are just flooding the network with traffic, a switch will have very little 

> The switch will allow you full duplex on adapters which support that.

  True but unless you are both sending and recieving simultaneously this has
little effect.  The claimed 32MB speed of a full duplex connection assumes that
you are doing 16MB IN and 16MB OUT of the system at the same time.  Generally
this is usefull for servers where lots of clients are reading and writing all 
time.  THe AS/400 certainly qualifies here but the network in question is only 5
stations so multiple concurrent traffic is not as likely.

> Unfortunately, I think the AS/400
> adapters are half-duplex only (not 100% sure though!).  Bet Larry knows tho...

  With the rapid removal of T/R networks in my client base I have only one 
with a T/R switch.  They are using the latest 2724 PCI token-ring card.  This 
is Full Duplex capable but I'm not sure of the 2619 or 2624 card since you must
have a switch to actually find out!

  Anyway, if you can get a switch cheap on Ebay or wherever it's not gonna hurt
anything for sure but it's not going to magically solve the speed problem here.

  - Larry

Larry Bolhuis         |         What if it's True?
Arbor Solutions, Inc  |
(616) 451-2500        |  
(616) 451-2571 -fax   | 
lbolhui@ibm.net       |
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