[ih] Protocol numbers (was IP version 7)

Alex McKenzie amckenzie3 at yahoo.com
Fri Dec 25 06:58:50 PST 2020


 Nope.  NOT 100kbs.  The speed of the data transfer was governed by the SIGNALS "ready for next bit" and "here's your bit".  The IMP made NO assumptions about how fast the Host could send or receive, and no assumptions about whether the speed would be constant or sporadic (for example, there might be a longer delay when accessing a new Host memory word than the delay between bits within a word).  Eventually there was a "Very Distant Host" interface designed to run over a clocked modem, but I don't think any modem with a speed higher than 50kbs was ever used.
Alex

    On Friday, December 25, 2020, 7:13:41 AM EST, Steve Crocker via Internet-history <internet-history at elists.isoc.org> wrote:  
 
 Nope.  Bit serial 100 kbs.  Specifically designed to be as simple as possible because each site had to design its own half.  100 kbs was easy to implement and fast enough to keep up with the 50 kbs IMP-IMP circuits.

I assume the description you’ve copied was just an unconscious writing error.

Steve

Sent from my iPhone

> On Dec 25, 2020, at 6:57 AM, Noel Chiappa via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> 
>> 
>> From: Brian E Carpenter
> 
>> ** "Early Experiences with the ARPANET and INTERNET in the UK", 1998
> 
> Very interesting, thanks for the pointer.
> 
> It contains one thing that I'm curious about: "the Interface Message Processor
> (IMP). This were initially attached locally to Host computers by a parallel
> interface." (bottom of pg. 2) I'm unaware of this stage; I thought they always
> used the 1822 bit-serial interface? I'd look at my copy of the BBN proposal
> (in response to the DARPA RFP), which probably talks about whether the plans
> were always for that interface, but alas my son and his wife are asleep in the
> room it's stored in, so I can't. I suppose it's possible a first IMP or so
> were prototypes, and initially used a parallel interface, later replaced by
> the 1822 interface, but I don't recall hearing about that. Can anyone expand?
> 
>    Noel
> 
> PS: That site, ban.ai/multics/, is completely mind-blowing. Check it out.
> 
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