cyamamot@aludra.usc.edu (Cliff Yamamoto) (09/21/90)
I've been thinking about gettinng a 9.6Kb modem, but w/ all these
standards, I'm confused. I'm not too interested which is better or
more popular, just what the *heck* is each one? Can anyone shed
some light on the following:
V.32 - Is this *real* 9600 baud at full duplex?
V.22bis - ????
V.22 - Was this the "fake" 9600 that ran 300 baud in one direction but
9600 baud in the other, and used some 'ping-pong' algorithm to
see who sends at 9600 baud?
V.21 - ????
V.13 - ????
V.23 - ????
PEP - Don't know what each letter means, but this is some proprietary
Trailblazer error correction and/or compression technique used
by Telebit? Does it substitute the V.42 and/or V.42bis?
HST - Is this another proprietary error correction and/or compression
technique from US Robotics?
Bell103 - I think this is what defines the 300 baud analog modulation and
demodulation characteristics.
Bell212 - And this defines the 1200 baud full duplex analog characteristics.
Bell202 - Was this 1200 baud half duplex analog characteristics?
V.42 - Some sort of error control, does it ONLY run with V.32? Can
it work without any data compression?
V.42bis - Data compression. Does it NEED to have V.42 to work properly?
Does this V.42bis only work at 9600 baud and faster?
MNP2-4 - Error control from Microcom? Like V.42 but different capabilities.
Does it ONLY run with V.32?
MNP5 - Data compression from Microcom? Does this work with MNP2-4?
Does it only work at 9600 baud and faster?
V.25bis - ????
Yes, these are a lot of questions, but I'm sure there must be someone
out there who'd like to know about this stuff. I guess I'd like to see
some hierarchy diagram too like:
Serial | Compression | Error | Analog | Band-limited
Data | Algorithm | Correct | Mod/Demod | carrier
------------------------------------------------------------
+--> MNP5 ---> MNP2-4 -+
RS232 ----> V.42bis ---> V.42 --> V.32 -----> phone-line
| |
+--> V.22bis ---> none --> V.22 -+
(just an example)
Is that diagram even correct? I am used to the encapsulated format of
TCP/IP and I guess I'm expecting this modem stuff to be the same. Also
as a side question, do all these "multi-CCITT/MNP" modems use DSP? Is
it better if the modem has a DSP chip in it? I understand the data
compression (V.42bis/MNP5) requires a lot of CPU power. What do the
more powerful modems use? (80188/68000).
Thanks for any and all responses. If I get enough email, I will compile
all posted replies and email replies into a summarized post.
Regards,
Cliff Yamamoto