[ih] X.25

[Dave Crocker]

On 9/29/2025 12:07 PM, Michael Grant via Internet-history wrote:
> How was it used in the early Internet?


One (Arpanet and then Internet) example was for the early stages of 
CSNet, as a dial-up path!

X.25 service, in the early 1980s, was for client/server, rather than 
peer-to-peer.  Early CSNet was strictly dial-up email exchange, as a 
gateway to Arpanet mail.  We configured use of dial-up to X.28/X.29/X.25 
services, as cheaper than regular dial-up.

CSNet had its own link layer reliable packet mechanism.  I did not 
initially worry about the size of packet the phonenet layer was using, 
compared to the X.25 packet size it ran on top of. And, of course, the 
phonenet packet was a bit larger than the X.25 packet, which effectively 
doubled our packet count.  The result was /not/ cheaper than dial-up.

I adjusted the phonenet packet size and charges got more reasonable...

d/

-- 
Dave Crocker

Brandenburg InternetWorking
bbiw.net
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