DC 10 - 1 DATACOMM John Abbott College JPC Digital Telecomm M. E. Kabay, PhD, CISSP Director of...

DC 10 - 1

DATACOMM

John Abbott College JPC

Digital TelecommM. 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)