Intel ER8100STUS - Express 8100 Router, Reference Manual

Page: 33 / 150

Reference.bok : Chapter04 21 Wed Apr 22 10:58:08 1998
21
ISDN Concept
ISDN Services
ISDN Concept
What is ISDN? ISDN is a digital telecommunications network that allows you to send all kinds
of information, including speech and data, in much the same way as making a
telephone call. The ISDN is digital from end-to-end which improves the data
communications quality and restricted information rate resulting from the use of
analog links together with modems.
CCITT has defined an ISDN as a network, in general evolving from a telephony
Integrated Digital Network (IDN), that provides end-to-end digital connectivity
to support a wide range of services, including voice and non-voice services, to
which you have access by a limited set of standard multi-purpose user-network
interfaces.
What ISDN offers ISDN offers multiple 64 kbps or 56 kbps connections on demand with a low error
rate. This can be used in place of leased line WAN links or as a backup to leased
line WAN links. A main advantage of ISDN is that a modem is not required—
the router can be connected directly to the ISDN.
Channel types
There are two types of channels used in ISDNs:
■
B-channels
64 kbps or 56 kbps full duplex, synchronous channels for data and voice
transfer
■
D-channels
16/64 kbps signalling channels
Connection types
There are two types of connectivity:
Basic Rate Access (2B+D)
This type of connection provides two independent data (B) channels (56 kbps or
64 kbps), and a 16 kbits signalling (D) channel which is provided for communi-
cation between the router and the ISDN exchange. It is used to set up and clear
calls for both information channels. This arrangement is called 2B+D and is
equivalent to two independent telephone lines each with a 64 or 56 kbps capacity.
Up to eight terminals can be connected to the line, although only two calls can be
in progress at any one time (each using a B-channel).
Primary Rate Access (30B+D)
This type of connection is used for connecting Private Branch Exchanges (PBX)
to the ISDN. In most countries, Primary Rate Access has 30 B-channels (56 kbps
or 64 kbps) and one D-channel (64 kbps). In the USA and Japan a 23B+D ar-
rangement is used.
Note
The Intel Express 8100 Routers offer Basic Rate Access (BRA) only.