Digital Network
P1.1
PSTN Hierarchy,
International Gateway
Exchanges
National Exchanges
Regional Exchange
Primary switching
Centre
Local Exchanges
or central office
Subscriber Lines
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P1.2 A
ISDN Services
There are two main services associated with ISDN – Basic Rate Interface (BRI) and
Primary Rate Interface (PRI). Both services consist of multiple channels over which
data can be sent (known as B channels) and also include a signaling channel (the D
channel). The D channel is used for control and signaling purposes, such as setting
and tearing down ISDN call. Referred to as “out-of-band” signaling, this method
ensures that other ISDN calls do not interfere with existing connections, that
bandwidth on the B channels is reserved for data only, and ultimately results in
quicker call setup and teardown.
There are two types of services associated with ISDN:
•
BRI
•
PRI
Basic Rate Interface (BRI) ISDN
Basic Rate Interface ISDN is made up of two 64 Kbps B channels that are used for
sending and receiving data in full duplex, and one 16K D channel for signalling. In
total, an ISDN BRI interface provides 144K of bandwidth (64+64+16). ISDN BRI is
often referred to as 2B+D. Many Cisco router models include built-in BRI interfaces,
but they can also be added using modular WAN interface cards.
Primary Rate Interface (PRI) ISDN
For companies with higher bandwidth requirements, ISDN Primary Rate Interface
(PRI) service exists. In North America, PRI service consists of 23 64 Kbps B
channels, and one 64Kbps D channel, for a total possible bandwidth of 1.544Mbps
(T1 equivalent). In Europe, PRI service consists of 30 B channels and 1 D channel,
for a total bandwidth of 2.048Mbps (E1 equivalent). ISDN PRI interfaces are
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Digital Network
typically implemented as modular WAN interfaces on Cisco routers, although some
models do include built-in PRI ports
Videoconferencing
Videoconference (also known as a video teleconference) is a set of interactive
telecommunication technologies which allow two or more locations to interact via
two-way video and audio transmissions simultaneously. It has also been called visual
collaboration and is a type of groupware. It differs from videophone in that it is
designed to serve a conference rather than individuals.
It is capable of communicating with almost all commercially available conferencing
systems over ISDN lines (digital telephone lines). It can also be used for conferencing
over the Internet but this is much less reliable.
High speed file transfer
High speed file transfer the high bit rate speeds of ISDN make file transfer application
a snap.
Performance, The use of ISDN to connect LANs and enable remote access to LANs
and LAN based services is feasible and offers bit rates to users of up to 128 kbps,
which is adequate for many sorts of computer based 'multimedia' sessions.
ISDN is seen by many in the industry as the ramp through which multimedia
networking will gain acceptance. The installed base of ISDN is growing rapidly
(30,000 line per month in Germany). ISDN is able to provide connections throughout
the world. In Europe there are 'Euro-ISDN' agreements between operators. In the
USA the use of the Web is driving the growth of ISDN in some states.
Internet Access
We support unlimited access using dual channel, bonding on ISDN lines - giving
128kbps BOTH upstream and downstream, with fast call connect times, all the
features of the Standard Dial-up account and usage without caps. When our
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Digital Network
broadband offering becomes available in your area you can move to it while keeping
your email and website addresses.
Remote Backup
Remote Backup is the process of transmitting your files, via a network connection, to
a geographically remote location where they can be stored safely for later retrieval.
Remote Backup addresses both the execution and physical security concerns of a
company wishing to prevent data loss. Since the process is entirely network-based, the
scope for human error
remote backup could be done via ISDN or using faster fixed-line connections, but the
cost was prohibitive, both for potential service providers, and for many potential
customers.
LAN to LAN connectivity
LAN-LAN interface policy is specified at the boundary between sub-networks which are
in the same geographic location
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P1.2 B
ISDN reference points R,S,T,U AND V
R
A communication reference point between a non-ISDN compatible TE and a TA.
S
A communication reference link between the TE or TA and the NT equipment.
T
A communication reference point between user switching equipment and a Local
Loop Terminator.
U A communication reference point between the NT equipment and the LE. This
reference point may be referred to as the network boundary when the FCC definition
of the Network terminal is used.
V The interface point in an ISDN environment between the line termination and the
exchange termination.
The functional grouping of ISDN is Network termination 1 (NT1), Network
termination 2 (NT2) and terminal equipments.
TE1: Specialized ISDN terminals are referred to as terminal equipment type 1 (TE1).
Ex. Digital telephone, Integrated voice/data terminals and digital facsimile equipment.
Or whatever it is that we hook up to the ISDN phone line.
TE2: Non - ISDN terminals such as DTE that predate the ISDN standards are referred
to as terminal equipment type 2 (TE2). Ex. Terminal with physical interface as RS232 and host computers with X.25 interface. This is the old analog telephone. Or oldstyle fax machine. Or modem. Or whatever we use to hook up to the analog phone
line. It can also be other communications equipment that is handled by a TA.
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Digital Network
TA: Terminal Adaptor. This lets old, TE2 stuff talk to the ISDN network. It also
adapts other kinds of equipment, like ethernet interfaces , to ISDN.
NT1: Network Termination type 1. This is the end of the line for the local phone
company, and the beginning of your house's phone network. Network termination 1
(NT1) belongs to OSI layer1, functions associated with physical and electrical
termination of the ISDN on the user’s premises.
NT2: Network Termination type 2. In most homes, this won't exist. Network
termination 2 (NT2) belongs to layer2 & 3 of OSI layer which is an intelligent device,
functions as switching and concentration functions. For a big company with private
telephone system, this would be the guts of that telephone system.
LT: Line Termination. This is the physical connection to the phone company.
ET: Exchange Termination. This is the local phone company's logical connection
from your telephones to "the phone network".
Figure 1.1 Sample ISDN Configuration Illustrates Relationships Between Devices and
Reference Points,
Figure 1.1
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P1.3 A
Oregon, USA.
Found Using: http://www.kropla.com/dialcode.htm
http://decoder.americom.com/decoderscript?handle=101&Search=503
P1.3 B
Group 2: The numbers is used
to identify the country you are
calling international exchange.
Group 1: The numbers
connects you to the
00
1
503
XXX
YYYY
Group 5: The numbers
specifies the phone line that
runs from the local exchange
into your residence international
Group 3: The Numbers is used to
specify the geographic region of
the country you are calling
international exchange.
Group 4: The numbers is used
to identify the local exchange
international exchange.
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Digital Network
This diagram shows that the local number can be divided into an exchange
code (end office switch identifier) and a port (or extension) code.
P1.3 C
Task 2
GoS =
A N / N!
A 2 A3 A N
1+ A +
+
+
2!
3!
N!
A = Traffic (Erlangs).
N = Circuits/Paths/Lines.
GoS = Grade of Service.
Residential:
Gos: No greater than 0.02 or 1 in every 50 calls lost.
A = 0.6E, N = 1
0.6 1 /1! = 0.6
0.6
= 0.375
1 + 0. 6
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A = 0.6E, N = 2
0.6 2 /2! = 0.18
0.18
= 0.101
0.6 2
1 + 0.6 +
2!
A = 0.6E, N = 3
0.6 3 /3! = 0.036
0.036
= 0.0198
0.6 2 0.6 3
1 + 0.6 +
+
2!
3!
Traffic Intensity
Number of Circuits GoS (Grade of
Service)
0.6 E
0.6 E
0.6 E
1
2
3
1 Call Lost in
Every
0.375
0.101
0.0198
Industrial:
GoS: No greater than 0.05 or 1 in every 20 calls lost.
A = 1.5E, N = 1
1.5 1 /1! = 1.5
1.5
= 0.6
1 + 1. 5
A = 1.5E, N =2
1.5 2 /2! = 1.125
1.125
= 0.310
1.5 2
1 + 1.5 +
2!
A = 1.5E, N =3
1.5 3 /3! = 0.5625
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0.5625
= 0.134
1.5 2 1.5 3
1 + 1.5 +
+
2!
3!
A = 1.5E, N =4
1.5 4 /4! = 0.211
0.211
= 0.04797
1.5 2 1.5 3 1.5 4
1 + 1.5 +
+
+
2!
3!
4!
Traffic Intensity
Number of Circuits GoS (Grade of
Service)
1.5 E
1.5 E
1.5 E
1.5 E
1
2
3
4
1 Call Lost in
Every
0.6
0.310
0.134
0.04797
A = 0.6E + 1.5E = 2.1E
Between Exchange A and B:
GoS: No greater than 0.05 or 1 in every 20 calls lost.
A = 2.1E, N =1
2.1 1 /1! = 2.1
2. 1
= 0.677
1 + 2. 1
A = 2.1E, N =2
2.1 2 /2! = 2.205
2.205
= 0.416
2.12
1 + 2.1 +
2!
A = 2.1E, N =3
2.1 3 /3! = 1.5435
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1.5435
= 0.225
2.12 2.13
1 + 2.1 +
+
2!
3!
A = 2.1E, N =4
2.1 4 /4! = 0.8103375
0.0.8103375
= 0.106
2.12 2.13 2.14
1 + 2.1 +
+
+
2!
3!
4!
A = 2.1E, N =5
2.1 5 /5! = 0.34034175
0.34034175
= 0.04255
2.12 2.13 2.14 2.15
1 + 2.1 +
+
+
+
2!
3!
4!
5!
Traffic Intensity
Number of Circuits GoS (Grade of
Service)
2.1 E
2.1 E
2.1 E
2.1 E
2.1 E
1
2
3
4
5
1 Call Lost in
Every
0.677
0.416
0.225
0.106
0.04255
Lists of Reference
1http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm#wp1020568
2.http://www.kropla.com/dialcode.htm
3.http://decoder.americom.com/decoderscript?handle=101&Search=503
4.http://www.iec.org/online/tutorials/fund_telecom/topic02.html
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