this post was submitted on 06 Jan 2024
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It was an evolution of previous protocols and only marginally better/faster than, say, ymodem.
It was useful, but was it really ahead of its time?
Hmmโฆ I remember zmodem being noticeably faster, more reliable, and flexible compared to its predecessors. But I think of it as ahead of its time inasmuch as what followed seemed a definite step back. Internet-based protocols which replaced it were quite a bit slower due to latency issues and what not, and it would take quite some time for new approaches to surface. Today, we have the like of bittorrent which does leap ahead in many ways but that was a long time coming.
Technically speaking, it wasn't replaced by IP-based utilities, since they have different functions. Zmodem is intended for sending binary files over an ASCII-based (7-bit) serial line, whereas the Internet-based protocols send files over IP, which is a packet-based networking protocol. That's where the performance difference comes in, since TCP/IP has significant overhead in the form of TCP and IP headers in each 1500-byte packet, plus extra processing costs on each end. That overhead brings with it far more flexibility in connecting to any arbitrary host on the network to transfer files, not just the two on either end of a serial line.
(It wasn't even replaced, since it's still available on my computer right now, installed as a dependency of something or other. I think the last time I used it was to transfer a file to an embedded device.)
i think zmodem would resume/reattempt when transfers started to fail or drop.
Xmodem and ymodem would do some retries. But xmodem specifically allowed resuming. And the ability for terminals to auto-downlpad if they got a particular byte sequence
Probably incremental, but I'll tell you this: I certainly remember the benefit of ZMODEM-90 with MobyTurbo over YMODEM-g.
I haven't thought of that protocol feature in about 20+ years. Saved so much extra time transferring over long-distance ($$$).
Just a casual reminder that 20 years ago is 2004. Not trying to correct you or anything, just sharing in the existential dread I felt reading this.
Yep, 2004 is about right, going through terminal emulators and reminiscing on old protocols that no longer mattered because of broadband and TCP/IP. Time flies, that's for sure.