[comp.dcom.telecom] An Introduction to ISDN

chip@chinacat.unicom.com (Chip Rosenthal) (10/08/90)

In article <13087@accuvax.nwu.edu> BRUCE@ccavax.camb.com (Barton F. 
Bruce) writes:

>the framing bit also (under ESF) can carry a small amount of
>network managment data.

That "facilities data link" seems to be a frequently underutilized
feature.  Part of the problem is that different carriers and
organizations (and vendors) have defined different standards for what
should appear in this channel.  Another problem is that the carriers
standards usually define a way for them to monitor performance of the
user equipment, but don't provide users' the ability to monitor the
performance of their network.  That is, the carriers are happy to take
information, but not give it, and thus many folks are unhappy about
that missing capability as well.

(I've been away from the specs and pubs and TR's for almost a year
now.  Maybe the situation has improved.)

The big thing ESF gets you which is used universally is a six-bit CRC
to provide a check on each 24-frame superframe.


Chip Rosenthal  <chip@chinacat.Unicom.COM>
Unicom Systems Development, 512-482-8260