-=> Quoting Craig Ford to John Roberts <=-

 CF> Don't confuse V.42 with the error control functions it defines (ie.
 CF> LAP-M, and the "alternate" protocol which is equivalent
to MNP service
 CF> levels 2-4), V.42 is predominately a scheme for negotiating error
 CF> control methods. 

V42 is _entirely_ a scheme for negotiating error control methods

 CF> provisions are intrinsically made to accomodate modems which support
 CF> MNP 2-4, and additional measures are included to accomodate virtually
 CF> any other scheme.

These are not "intrinsic" provisions.  They're laid down in spec, in
black and white

 CF> If LAP-M is negotiated, the modems will also attempt to negotiate
 CF> V.42bis. If the "alternate" protocol defined by V.42 is negotiated,
 CF> V.42bis can also be negotiated on top of it (Microcom has published
 CF> procedures for accomplishing this), but it is rarely implemented.

There is nothing in V42 which would or should command the then CCITT
recommended compression method (V42bis) to be switched off.  V42bis is
not "on top of" anything.  V42bis is entirely seperate from V42.  It's
not "can" also be negotiated either.  It _must_ be available for
negotiation

As to being "rarely implimented", both V42/LAP-M
and V42/MNP-2-3 or -4 are commonplace.  MNP-2 or -3  or -10 may be
commanded in place of -4 as the EC.  Using V42bis as compression too.
MNP-4 _must_ be available for compliance.  V42bis _must_ be
available for compliance as well...

rgdZ
Richard


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