At 5:35 PM +0000 6/21/03, The Road Goes Ever On wrote: >""John Neiberger"" wrote in message >news:[EMAIL PROTECTED] >> We use ISDN for dial backup where DSL is not available and we need more >> bandwidth than a standard modem connection would provide, which is a lot >of >> locations. It seems that there is a lot of ISDN out there and plenty of >it >> being ordered, but I might be mistaken. I'd love to get rid of it because >> it has too many quirks. :-) > > >just my two cents, but ISDN is one of the old and arguably obsolete >technologies that still is quite relevant today. I prefer to sell RLAN ( ATM >host and DSL spokes ) but when the customer requires relaibale backup, ISDN >is always the choice. Happens a lot because although DSL is generally very >reliable, when a link develops troube it still can take a long time for a >telco to get around to fixing it. Sometimes over a week, in my experience. > Another two cents, but I strongly recommend studying X.25 and ISDN simply for the background they give for other protocols. I don't think, for example, you really understand FR until you understand why and how that it was stripped down from X.25, and was also designed as a low-speed access protocol to ATM. Understanding Q.931 leads to better understanding of Q.931, and, especially if you also look at Q.932, helps you understand motivations for IP telephony protocols.
I was developing some AVVID courseware and found it extremely useful to present the ISDN reference model that the students _thought_ they knew, and then started filling in the blanks that are usually skipped in pure data instruction -- such as an NT2 being the prototype for a PBX. Also usually skipped are anything going beyond (toward the carrier) the NT1. It turns out that the ISDN conceptual architecture has quite a number of interworking abstractions of what goes on in the "cloud", which again can help in understanding what IP telephony has to do. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71071&t=71071 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
