Intel ER8100STUS - Express 8100 Router, Reference Manual

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Reference.bok : Chapter04 22 Wed Apr 22 10:58:08 1998
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ISDN Services
ISDN Services
ISDN Services
Three types of service ISDN services are divided into three categories:
■
Bearer Services
■
Tele Services
■
Supplementary Services
Bearer Services
These are the basic transport services which transfer information between the ter-
minal/net interface. That is a connection must be set up between two routers be-
fore communication can take place. There are two types of Bearer services:
Circuit switched
These are the simplest types of Bearer services. Once a connection is established,
data is transferred over the link (B-channel) at a rate of 64 kbps (or 56 kbits for
some ISDNs).
Packet switched
If the data rate is variable, then it may not be cost-effective to pay for an
end-to-end channel for the duration of the call. In this case, data is sent in packets
and the cost is based, partly, on the volume of traffic rather than the duration of
the call.
Tele Services
These define the way in which certain standardized applications use ISDN. The
following services are defined by CCITT:
Telephony
Provides two-way, real-time speech conversation. There are two types:
■
3.1 kHz
■
7 kHz, which provides speech and sound transmission of a much higher
quality than 3.1 kHz telephony
Teletex
Enables subscribers to exchange character-coded documents automatically. It is
much faster than Telex and has a much larger character set.
Telefax 4
Provides high-speed, high-quality facsimile transmission.
Mixed Mode
This is a combination of Teletex and Telefax 4.
Videotex
Provides retrieval and mailbox functions for text and graphic information.