[Info-vax] Ethernet history Was: Re: booting vaxstation off alpha

[Paul Sture]

In article <kfeiuh$de9$1 at Iltempo.Update.UU.SE>,
 Johnny Billquist <bqt at softjar.se> wrote:

> On 2013-02-12 23:10, Chris Scheers wrote:
> > IIRC, CI is a form of token ring.  In particular, it has various "slots"
> > that circulate that are allocated to applications.
> 
> Nope. CI works similar to ethernet. It just checks if the line is free 
> before starting to transmit.
> However, it is also different than ethernet in that each node has an 
> individual delay once the path goes silent, and you can only grab the 
> path if it's been silent "long enough", which is different for each 
> node. And collisions are detected by the fact that all messages on CI 
> are expected to be ACKed by the receiver. If no ACK comes back, you 
> retransmit.
> 
> As for allocation of traffic by type, this is totally up to the OS, and 
> CI itself don't give a damn. DEC defined SCA as the communications layer 
> on top of CI, and SCA have datagrams, messages and block data.

I cannot let a mention of Token Ring and ethernet in the same post go by 
without mentioning the following article:

"Ethernet at 40: Its daddy reveals its turbulent youth
Bob Metcalfe: How Token Ring and 'IBM's arrogance' nearly sank Big Blue"

http://www.theregister.co.uk/2013/02/09/metcalfe_on_ethernet/

-- 
Paul Sture