RE: IBM 8230 Token-Ring concentrator

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

Hello Russ,

*** Warning, warning, flame war approaching **************

I take issue with your statements.  I do agree with the sugesstion to evaluate 
the entire infrastructure but 
you seem to consider Ethernet to be an upgrade from Token-Ring.  Why?  The ONLY 
advantage to Ethernet is its 
price.  It is much cheaper than TR.  But then you get what you pay for -- 
Ethernet cards have much less 
intelligence on board than TR cards.  Ethernet is good for light-to-medium 
network loads; TR is good for 
medium-to-heavy network loads.

TR uses a much more civilised protocol than Ethernet which is why a lower rated 
TR network will perform 
better than a higher rated Ethernet network.  At high traffic levels 4Mbs TR 
will thrash 10Mbs Ethernet, and 
16Mbs TR will give 100Mbs Ethernet a good run for its money.  (I have just seen 
information suggesting that 
100Mbs TR is available -- must look into this.)  Here are some graphs showing 
what happens:

:font style=fixed.

T
h      |
r      |
o  1.0 |                            **********************
u      |                        ***
g   .8 |                     **      @@@@@@@@@@@@@@@@@@@@@
h      |                  **     @
p   .6 |               **    @
u      |            **   @
t   .4 |         **  @ ########
       |      ** @ ###          #### 
S   .2 |   * @ #                     ##
       |*@#                             #######
       |_______________________________________###########
           |     |     |     |      |      |      |      |
           .2    .4    .6    .8    1.0    1.2    1.4    1.6      
                                Offered Load G

* = Ideal
@ = Token-Ring
# = Ethernet

Throughput S = The amount of data successfully transmitted between nodes in the 
network.
Offered Load G = Includes not only the node-to-node data, but also any 
acknowledged packets, packets 
retransmitted due to errors, and packets associated with network management.  
The offered load is always 
greater than or equal to the throughput.

Source: Design and Organization of Computing Structures by James H. Herzog.  

Please make allowances for the poor quality graphics however you should get the 
idea.

:efont.

The basic difference is that TR allows only the device with the token to 
transmit; Ethernet lets everyone try 
and hopes only one device is _actually_ trying -- they call it collision 
detection.  

A TR device says "I've got the token, you wait your turn", "OK, I'm done, it's 
your turn now".  Ethernet says 
"Ooh, nobody's using the LAN, here I go. Oh, damn, packets have collided, flush 
the network, everybody try 
again".

I realise the protocols are a bit more complicated than I suggest but that is 
the gist of it.

The only real problem with TR is that one device may not release the token so 
other devices complain -- this 
is called beaconing. The naughty device is dropped from the ring and another 
device takes over and issues a 
new token.  This can be a time-consuming operation and the network suffers 
because of it, however, in a well 
managed network with good quality hardware and reliable operating systems, 
beaconing should be minimal.

Regards,
Simon Coulter.

//----------------------------------------------------------
// FlyByNight Software         AS/400 Technical Specialists
// Phone: +61 3 9419 0175      Mobile: +61 0411 091 400
// Fax:   +61 3 9419 0175      E-mail: shc@flybynight.com.au
// 
// Windoze should not be open at Warp speed.
//--- forwarded letter -------------------------------------------------------
> X-Mailer: Microsoft Outlook 8.5, Build 4.71.2173.0
> Date: Wed, 30 Dec 98 09:58:54 -0500
> From: "rpopeil" <russ.popeil@ac.avnet.com>
> To: MIDRANGE-L@midrange.com
> Reply-To: MIDRANGE-L@midrange.com
> Subject: RE: IBM 8230 Token-Ring concentrator
> Importance: Normal

> 
> Since you are considering new equipment why not look at a total
> infrastructure refresh.  It might be a good time to upgrade the
> infrastructure and perhaps change to fast switched Ethernet.
> 
> Russ Popeil
> IBM Certified Specialist
> Avnet Computer- Intergrated Solutions. Bottom-Line Results.
> Office: 516-677-9346 Fax: 516-677-0296
> Pager: 800-759-8888 Pin: 1651954
> Pager eMail: 1651954@skytel.com
> eMail: Russ.Popeil@avnet.com
> http://www.avnetcomputer.com

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