> However, X.25 had significant limitations, and was married to the telephone network in uncomfortable ways (both in that it relied on leased lines and in that X.25 was in many ways designed as a direct analog to the telephone network).
This is a bit harsh.
I downloaded Minix updates, and indeed my first Linux kernel disk images, over an X.25 network.
X.25 was one of the first packet-switching protocols - predating IPv4 by a few years - and therefore is very much NOT an analog to telephone (circuit-switched, predominantly, historically and at the time) networks. (Okay, there were VC's, let's not muddy the waters.)
I recall in the early/mid 1990's a colleague hunting down a weird X.25 network utilisation pattern, where a customer was establishing and tearing down connections at a rapid rate of knots. Details are fuzzy, it was a long time ago, but IIRC the customer had worked out how to embed payload in the connection establishment header, but at the far end was refusing that connection (while ingesting the payload). Billing was done based on connection establishment and subsequent transfer. Great (loophole) success, etc.
TFA touches on SNA (IBM's System Network Architecture) but doesn't seem to attribute as much blame to it as I believe we should. SNA was, coincidentally, a 7-layer model. The obvious distinction, to modern minds anyway, is the hierarchical vs peer relationship between entities on a network. (An interesting question to ask graduates is to define a network -- this historical view disparity is objectively fascinating in the contemporary context where peer addressability is an assumed function of same.)
This is a bit harsh.
I downloaded Minix updates, and indeed my first Linux kernel disk images, over an X.25 network.
X.25 was one of the first packet-switching protocols - predating IPv4 by a few years - and therefore is very much NOT an analog to telephone (circuit-switched, predominantly, historically and at the time) networks. (Okay, there were VC's, let's not muddy the waters.)
I recall in the early/mid 1990's a colleague hunting down a weird X.25 network utilisation pattern, where a customer was establishing and tearing down connections at a rapid rate of knots. Details are fuzzy, it was a long time ago, but IIRC the customer had worked out how to embed payload in the connection establishment header, but at the far end was refusing that connection (while ingesting the payload). Billing was done based on connection establishment and subsequent transfer. Great (loophole) success, etc.
TFA touches on SNA (IBM's System Network Architecture) but doesn't seem to attribute as much blame to it as I believe we should. SNA was, coincidentally, a 7-layer model. The obvious distinction, to modern minds anyway, is the hierarchical vs peer relationship between entities on a network. (An interesting question to ask graduates is to define a network -- this historical view disparity is objectively fascinating in the contemporary context where peer addressability is an assumed function of same.)