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30 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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DC 10
-

1

DATACOMM

John Abbott College JPC

Digital Telecomm

M. E. Kabay, PhD, CISSP

Director of Education, ICSA

President, JINBU Corp


Copyright © 1998 JINBU Corp.

All rights reserved

DC 10
-

2

Digital Telecomm


Digital CPE


ISDN


ATM


Infobahn

DC 10
-

3

Digital CPE


Digital PBX


Digitized Voice


T
-
1

DC 10
-

4

Digital CPE

Digital PBX a hot seller today


Turns analog signal (voice) into digital pulses


Allows voice and data to be controlled from a
single central switch


Digital phone converts voice to bits


Codec

is Coder
-
Decoder (opposite of Modem)

DC 10
-

5

Digital CPE

Digitized Voice


Pulse code modulation (PCM)


8 Khz sampling


8 bits/sample


64Kbps data stream


Human hearing cannot distinguish digital and
analog signals


Allows full range of digital transmission
controls


error checking


signal regeneration

DC 10
-

6

Digital CPE

T
-
1


1.544 Mbps channel


24 channels using TDM


Applications


PCM on T
-
1 allows 24 voice links


need only 2 twisted pairs + special
equipment


resistant to EMI (high signal
-
to
-
noise ratio)


can be highly cost
-
effective

DC 10
-

7

Digital CPE


T
-
1 signalling


voice runs 64 Kbps


data needs 1 parity bit/byte: 56 Kbps


Multiplexers for T
-
1 lines


can share single channel among several
lower
-
speed devices


rent
fractional T
-
1

from carrier

DC 10
-

8

ISDN


Integrated Services Digital Network


Channels


Rates


Services


Trends

DC 10
-

9

ISDN


Standards still in evolution


CCITT working on intl agreements


Expect eventual hardware interoperability

DC 10
-

10

ISDN

ISDN Channels


Different bandwidths =
channels


Bearer channel (B
-
channel) 64 Kbps


D
-
channel


signalling data @ 16 Kbps or 64 Kbps


usually used for
out
-
of
-
band signalling


often relatively low usage


used for low
-
priority data; e.g., e
-
mail


A
-
channel : analog communications


C
-
channel: very low
-
speed data

DC 10
-

11

ISDN


Basic
-
Rate I/F (BRI)


2 B
-
channels + 1 D
-
channel (2B+D)


Primary
-
Rate I/F (PRI)


US/Canada: 23 B
-
channels + 1 D
-
channel


1.544 Mbps


European PRI: 30 B + D


2.048 Mbps


Other channel arrangements


A+C: hybrid I/F


voice + data for non
-
ISDN phones/terminals

DC 10
-

12

ISDN

Equipment Functions


TE1: Terminal Equipment Type 1


compatible with ISDN network


e.g., ISDN
-
compatible phone, workstation


TE2: Terminal Equipment Type 2


not compatible with ISDN network


requires
terminal adaptor

(TA) to link into
ISDN

DC 10
-

13

ISDN

Network Termination Equipment


NT1: Network Termination 1


OSI Layer 1


physical and electrical connection to
network


can be changed if digital transmission
medium changes (e.g., change to optical)


NT2: Network Termination 2



OSI Layers 2 and 3


e.g., PBX, LANs

DC 10
-

14

ISDN

ISDN Services


D
-
channel can carry info about callers


Individualized call
-
forwarding for specific
callers


Long
-
distance camp
-
on
-
busy function


Automatic routing of 800
-
calls to local outlet

DC 10
-

15

ISDN

Video


Motion Pictures Experts Group (MPEG)


Developing standards for video signal
compression


uncompressed requires 21 Mbps for
broadcast
-
quality real
-
time digital video


MPEG II requires only 7 Mbps


Video conferencing: most of image is static


send only changes


use multirate ISDN such as 384 Kbps
channels (6 B
-
channels)

DC 10
-

16

ISDN

ISDN Today


Not likely to see instant conversion of all
existing telecomm to ISDN


Primary Rate I/F (PRI) is about same cost as
T
-
1: but much more flexible


Residential customers a huge market


can have voice and data on same line


but only minority of residential customers
use existing analog services
--
so will ISDN
be commercially viable?

DC 10
-

17

ISDN

Broadband ISDN (BISDN)


In initial planning phase


Extremely high bandwidth (150 Mbps)


Real
-
time broadcast video services


Entertainment applications


Telecommuting applications

DC 10
-

18

ATM

Asynchronous Transfer Mode


Protocol for implementing BISDN


Independent of bandwidth


Data chunked into
cells


Being promoted by ATM Forum


founded 1991


consortium of many players in datacomm

DC 10
-

19

ATM

ATM Cells


53
-
bytes (bytes called
octets

in ATM)


header: 5 octets


payload: 48 octets

DC 10
-

20

ATM

Physical Transmission


SONET: Synchronous Optical Network


SONET line speeds defined in OC
-
N form


N is 51.84 Mbps


OC
-
1 = 51.84 Mbps


OC
-
3 = 155.52 Mbps


Other transmission media quite feasible

DC 10
-

21

ATM

Routing Cells


Set up equivalent of virtual circuits


Transmission path remains fixed for a
session


Headers include routing information


Virtual Channel Identifiers (VCIs)


Virtual Path Identifiers (VPIs)


Main differences from Frame Relay:


fixed cell sizes


different data formats

DC 10
-

22

Infobahn


Information Superhighway


NOT the current Internet


Usually refers to high
-
speed backbones


BISDN is chief candidate


Most of media reporting focuses on
applications, not transmission channel

DC 10
-

23

Homework


Read Chapter 10 of your textbook in detail,
adding to your workbook notes as appropriate.


Review and be prepared to define or expand all
the terms listed at the end of Chapter 10 of your
textbook (no hand
-
in required)


Answer all the exercises on page 232 of the
textbook using a computer word
-
processing
program or
absolutely legible

handwriting
(hand
in with final quiz)