RUBIN@GRAF.POLY.EDU (David Rubin) (05/16/89)
I am in the process of setting up a link between two P4200's via our campus PBX. I am trying to figure out the proper settings to configure the PBX's data connection. Right now we are using a 56k leased line. What I need to know are: - Baud rate (i.e. 56k or 57.6k or does it really matter) - Protocol (BiSync, HDLC, or SDLC) Any help would be appreciated. -- Dave Rubin - rubin@graf.poly.edu Polytechnic University
tvm@proteon.com (Tom Miceli) (05/17/89)
All the p4200 expects of the PBX is to receive two clocks (transmit and receive), and that data be passed unaltered. Be sure that the PBX is not trying to understand, compress, re-packetize, or interpret the data. Sure, the framing is HDLC/SLDC (only difference is that SLDC requires length to be a multiple of 8 bits), but the contents are not. If there is a configuration option, you should be very suspicious that the PBX is trying to be a packet switch, rather than a pipe. (The advantage of the packet switch approach is that bandwidth is not used constantly on the PBX trunk circuits.) Of course, it is free to use the capacity while the p4200 is just sending idles between packets.
tvm@proteon.com_ (Tom_Miceli) (05/17/89)
Message-Id: <8905171206.AA11760@monk.proteon.com> In-Reply-To: David Rubin's message of Mon, 15 May 89 17:05:17 EDT <8905152110.AA -------------------------------------------------------------------------------- All the p4200 expects of the PBX is to receive two clocks (transmit and receive), and that data be passed unaltered. Be sure that the PBX is not trying to understand, compress, re-packetize, or interpret the data. Sure, the framing is HDLC/SLDC (only difference is that SLDC requires length to be a multiple of 8 bits), but the contents are not. If there is a configuration option, you should be very suspicious that the PBX is trying to be a packet switch, rather than a pipe. (The advantage of the packet switch approach is that bandwidth is not used constantly on the PBX trunk circuits.) Of course, it is free to use the capacity while the p4200 is just sending idles between packets.
medin@NSIPO.NASA.GOV ("Milo S. Medin", NASA ARC NSI Project Office) (05/18/89)
Actually, the p4200 is very fussy about modem control signals (as it should be!), and some PBX's may not support all of the signals it's looking for. There is an excellent description of what signals are used in the hardware reference manual... Be sure and check your cable carries the required signals. thanks, Milo PS For what it's worth, we ran p4200's over a 19.2 Kb Northern Telecom digital PBX sync. link, and it worked fine after the PBX was strapped to deal with the modem control signals it SHOULD have been producing...