Appendix C: A Brief ISDN Glossary
ISDN PC Card – 17 Appendix C: A Brief ISDN Glossary
203
MSN
Multiple Subscriber Number. A feature that is only
available in Euro ISDN. Some telephone compa-
nies assign multiple numbers to each ISDN sub-
scriber line ordered. These MSNs are usually (but
not necessarily) in sequence starting with the
ISDN line’s primary number. Each MSN is an inde-
pendent telephone number. Each ISDN terminal
device connected to the line can be assigned one
of the line’s MSNs to permit internal call routing.
Ask your ISDN service provider whether your line
will be equipped with MSNs, and how many.
Note:
MSNs can be assigned to terminal equip-
ment without regard to specific ISDN services.
Multilink
A multilink connection is one that uses two or
more B channels as a single communication link.
The two B channels of a BRI can be bundled to
yield a data rate of 2 x 64 kbit/s. Multilink con-
nections generally result in a higher connection
charges.
NT-1
Network Terminator 1. This is the endpoint of the
ISDN network at the customer premises. The term
also denotes a device which is connected to the U
interface and provides the S/T interface to sub-
scriber equipment.
OSI reference
model
The Open Systems Interconnection model is a
standard description or “reference model” of data
transmission between any two points in a com-
munication network. Its purpose is to guide prod-
uct developers and maximize interoperability
among different products. The reference model
defines seven layers of communication functions
that take place at each end of a communications
link. Although the OSI model is not always strictly
adhered to, and related functions are not always
clearly organized in the same well-defined layers,
many if not most products involved in telecom-
munication can be described in relation to the
OSI model. It is also valuable as a uniform refer-
ence that furnishes a common ground for educa-
tion and discussion in the communications field.
Its seven layers are:
Glossary
