[rescue] RE: Time division and collision domains!
rescue at sunhelp.org
Tue Jun 26 14:10:03 CDT 2001
One question, does USB have synchronization, so as to avoid *collisions*.
You can not get 10 Mb/s through a 10 Mb/s ethernet port - period. Even crossover connections are less than 10 Mb/s. Put multiple systems with dynamic and bursty traffic, and your total average through-put will drop quickly.
When an Ethernet device has a packet to send, it does, and if there was already another device using the Ethernet "backbone", the device attempting to communicate will not only clobber the packet that was being sent (I think), but the attempting device will wait a random period of time and then attempt again. This is collison detect.
I suspect USB uses some sort of sync signal, and devices consume time slices.
You can not, AFAIK, get Quality of Service out of Ethernet - period.
(I just had to explain to a Visual Basic programmer about formatted printing/Pring Using in BASIC - yesh - isn't it a shame what passes for a "technical" education these days...)
Date: Tue, 26 Jun 2001 07:25:08 +0100
From: David Cantrell <david at cantrell.org.uk>
To: rescue at sunhelp.org
Subject: Re: [rescue] I'm one happy geek
Reply-To: rescue at sunhelp.org
"Joshua D. Boyd" <jdboyd at cs.millersville.edu> wrote:
> Is ethernet really adequate for such devices? I saw USB more as replacing
> PS/2, ADB, Serial, parallel, and to a lesser extent SCSI for low bandwidth
> With ethernet, you'd have to buy large switches, which aren't that cheap.
Why? What if you used exactly the same topology as with USB, using cross-
over cables? Ethernet chipsets are better-developed, and even at only
10Mbps (which would keep costs down) it's still faster.
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