mmcnew@pro-freedom.cts.COM (Monty McNew) (09/20/88)
Gynn@smoke writes: >At normal modem speeds such as 2400 bps, there is so little gain >in switching to a streaming protocol as to make it a waste of time >to implement. Do the calculations.. Streaming protocols can and do make a difference in file transfer times. If it is a direct connection (LD, Local calls etc) the difference is worth the effort. This months GEnie Livewire magazine (page 20, not talking about Y-modem G though, but xmodem 1k) says: "XMODEM (1k blocks) is a variation of the original XMODEM. The only difference is that the file is broken into 1,024 byte blocks (instead of 128 bytes for original XMODEM blocks). The major advantage of this is that the error checking is performed only once every 1,024 bytes. Less time is spent with error checking, reducing download time." It goes on to say: "Out tests show that XMODEM 1k and YMODEM downloads are about 5-10% faster than standard XMODEM." Article also points out that there is a caveat if there is an error in a block that you also have longer time re-sending since the blocks are larger. Where a streaming protocol _REALLY_ is beneficial (although XMODEM 1k or YMODEM is not streaming really) is while using PC Pursuit. If you have ever tried a 1200 baud XMODEM d/l over PC Pursuit, you soon realize that it takes a little over twice as long than if you were calling direct. Using YMODEM over a service such as this greatly reduces this time by about 35% (although I have not actually calculated it). Some BBS's won't even let you do an XMODEM d/l if you are calling via PCP, they delete your account if they catch you doing it. I understand (although I have not tried it) that ZMODEM over PC Pursuit is almost as fast a file transfer as if you were calling directly to the system. Someone else out there can fill in why it takes so long to XMODEM over PC Pursuit. I don't know the exact reason, something about the error checking over PCP's packet switching delays everything, hence the less error checking the protocol does, the less time it takes. I realize my two bits worth here have nothing to do with Y MODEM-G (I have never seen this one) but the point is, any protocol that uses larger blocks, creating less error checking time, is going to be faster. Plain and simple. If you are using PC Pursuit, the time savings are well worth it, although calling direct at 2400+ baud might not be, unless it is a very large file. UUCP: [ ihnp4 sdcsvax nosc ] !crash!pro-freedom!mmcnew ARPA: crash!pro-freedom!mmcnew@nosc.mil INET: mmcnew@pro-freedom.cts.com SLBM: 45 37 N / 122 36 W
gwyn@smoke.ARPA (Doug Gwyn ) (09/22/88)
In article <8809210141.AA02974@crash.cts.com> pnet01!pro-sol!pro-newfrontier!pro-freedom!mmcnew@nosc.mil writes: -Gynn@smoke writes: "I see no Gynn here." ->At normal modem speeds such as 2400 bps, there is so little gain ->in switching to a streaming protocol as to make it a waste of time ->to implement. Do the calculations.. Or, just watch the lights on your modem. -"Out tests show that XMODEM 1k and YMODEM downloads are about 5-10% faster -than standard XMODEM." That's about right. However, it has NOTHING to do with so-called "streaming" protocols, which was the topic of discussion. Sheesh.
blume@netmbx.UUCP (Heiko Blume) (09/24/88)
i'd like to point out, that mnp modems which are becoming more and more
common achieve a throughput of up to 7200 bps on a 2400 line utilizing
the mnp class 5 or higher. since the normal (128bytes/packet) kermit
and xmodem (etc) protocols allow a maximum of 400cps throughput regardless
of the line speed, it is important that new protocols are being invented
that avoid such restrictions. of course real streaming protocols are best
suited, especially for modems like courier hst and trailblazer, which
allow rates of up to 18000 bps.
lets get fast,
heiko
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