Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!uflorida!gatech!hubcap!ncrcae!heath
From: heath@ncrcae.Columbia.NCR.COM (Robert Heath)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: v.25 bis
Message-ID: <3980@ncrcae.Columbia.NCR.COM>
Date: 5 Dec 88 20:02:53 GMT
References: 
Reply-To: heath@ncrcae.Columbia.NCR.COM (Robert Heath)
Organization: NCR Corp., Engineering & Manufacturing - Columbia, SC
Lines: 29

In article  ddp+@ANDREW.CMU.EDU (Drew Daniel Perkins) writes:
>I was reading looking at the CCITT Red Book "Recommendations of the V Series"
>(Volume VIII - Fascicle VIII.1) today and noticed an interesting protocol
>"Recommendation V.25 bis, Automatic Calling and/or Answering Equipment on the
>GSTN Using the 100-Series Interchange Circuits".  
>Does anyone know of
>anything that supports this protocol?  

A number of modem manufacturers
such as Anderson-Jacobsen, Concord Data, NEC, etc. support the protocol.
The NCR TOWER series supports the v.25bis dialing protocols when you 
order SDLC/HDLC support.

>Is there a good reason why it isn't
>common?  I'm thinking that it might be very usefull for dialing sync modems,
>dialing ISDN Terminal Adaptors, connecting sync port selectors, etc.
>
One drawback  is that the dialing interface occurs at the data link 
control (DLC) level, which is usually not open to user programming.  
They introduce some new handshaking at protocol levels which have
been frozen for years.  In synchronous networks that most open layers 
are much higher up in the protocol stack. 

For a full discussion of v.25bis, see my article "Synchronous dialing
modems are advancing at full tilt", in the Nov. '87 issue of 
Data Communications magazine.

	Robert Heath
	heath@ncrcae.Columbia.NCR.COM