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WAN Technologies

Chapter 16

Chapter 16

2

Chapter Objectives


I


Differentiate between the types of network switching


Explain the Public Switched Telephone System


Discuss the Mobile Telephone System


Explain point
-
to
-
point WANs


Describe the X.25 protocol


Chapter 16

3

Chapter Objectives


II


Explain Frame Relay


Explain ATM


Explain the ISDN protocol and BISDN


Explain the FDDI protocol


Explain satellite communication


Chapter 16

4

Recall


I


Router is an Internetworking device used to link two
different networks


Two types of NAT are:


Static NAT


Dynamic NAT


Proxy server is a computer that allows network
users to make an indirect network connection to
different network services


Chapter 16

5

Recall


II


Types of proxies are:


Transparent proxies


Reverse proxies


Anonymous proxies


Zones of Internet explorer:


Internet zone


Local Intranet zone


Trusted Sites zone


Restricted Sites zone

Chapter 16

6

Recall


III


Applications of Internet:


World Wide Web


Electronic mail


File Transfer Protocol


TELNET

Chapter 16

7

Types of Switching

Switching

Circuit Switching

Message Switching

Packet Switching


Switching is a process of moving the data through a
series of intermediate steps rather than moving from
the start point directly to the end point.

Chapter 16

8

Circuit Switching


Direct physical connection established between sender
and receiver before data transmission


Allows a fixed rate of transmission


Major drawbacks are:


Unused transmission is wasted


Unused bandwidth cannot be used by any other
transmission

Chapter 16

9

Message Switching


No direct physical connection established between
sender and receiver


Message routed through the intermediate nodes


This technology is also known as store and forward
method

Chapter 16

10

Packet Switching


Message to be transmitted broken into units called
packets


Packet contains addressing information


Packets are carried on virtual circuits. Virtual circuits
are temporary connections over which the sending
and receiving stations communicate

Chapter 16

11

Connectionless Services


Before transmitting the packets, actual connection
not established between the sender and the receiver


Each packet considered as an independent unit


Each packet treated as a complete message


Packets follow different routes to reach destination

Chapter 16

12

Connection
-
oriented Services


Before transmitting packets, communication link
established


Packets follow same route to reach destination


For transmission, uses Switched Virtual Circuit
(SVC) or Permanent Virtual Circuit (PVC)

Chapter 16

13

Public Switched Telephone Network


Telephone system that uses copper wires to carry
analog voice data is called Public Switched
Telephone Network (PSTN)


Telephone services carried by the PSTN are often
called as Plain Old Telephone Service (POTS).


Services offered by POTS are follows:


Bi
-
directional


Ringing signals and dial
-
tone


Operator services



Chapter 16

14

Structure of Telephone System


I


Telephone system consists of following major
components:


Local loops


Analog twisted pairs going into houses
and businesses


Switching offices


Place where the calls moved from
one trunk to another


Trunks


Switching offices connected using digital
fiber optics called trunks


Chapter 16

15

Structure of Telephone System


II


Typical circuit route for a medium
-
distance call:

Chapter 16

16

Point to Point WANs


Two remote devices connected using a line
available from a public network


Public network can be a telephone network


Services basically provided at the physical layer


Users responsible for the data link layer protocols


Chapter 16

17

Physical Layer


To accomplish point
-
to
-
point connection between
two devices at the physical layer, use the following
services:


Modem technology


Digital Subscriber Line (DSL)


Cable modem


T
-
line


E1 Lines


SONET

Chapter 16

18

Data Link Layer


Concerned with data transfer


Protocol needed for reliable connection


A protocol is needed at this layer to have a reliable
point
-
to
-
point connection. For reliability, uses Point
-
to
-
Point Protocol (PPP)


For establishing, maintaining and terminating the
link, uses Link Control Protocol (LCP)


For providing flexibility to PPP, uses Network
Control Protocol (NCP)

Chapter 16

19

X.25 Protocol


Connection
-
oriented packet
-
switching protocol


Defines the way in which the connections between
the user devices and the network devices are
established and maintained.


Used in the packet
-
switched networks (PSNs) such
as the telephone companies.

Chapter 16

20

X.25 Devices


X.25 network devices are:


Data terminal equipment (DTE)


Data circuit
-
terminating equipment (DCE)


Packet
-
switching exchange (PSE)


Chapter 16

21

X.25 Virtual Circuits


X.25 virtual circuits are:


Switched Virtual Circuits (SVCs)


Permanent Virtual Circuits (PVCs)


Chapter 16

22

Frame Relay


High performance WAN protocol, faster than X.25


Operates at the physical and data link layer of the
OSI reference model


Does not involve error correction and network flow
control operations


Frame relay virtual circuits are:


Switched Virtual Circuits (SVCs)


Permanent Virtual Circuits (PVCs)


Chapter 16

23

Frame Relay Devices


The devices attached to the Frame Relay WAN for
transmission of data packets are, Data terminal
equipment (DTE) and Data circuit
-
terminating
equipment (DCE).

Chapter 16

24

Case Study


I


The head office of the MoneyMaker bank in Mumbai
is integrated with all its branches using the FDDI
technology. All the transactions are carried out using
this network. Due to congestion in the network the
bank is losing critical data which has become a
major area of concern for the bank.

Chapter 16

25

Problem


Data loss due to congestion in FDDI network
technology.

Chapter 16

26

Suggested Solution


All the branches should be integrated using the
Frame Relay technology. Frame Relay provides a
congestion control mechanism.

Chapter 16

27

Asynchronous Transfer Mode (ATM)


Cell
-
switching and multiplexing technology which
combines the benefits of both circuit switching and
packet switching


Transmits data, voice and video signals
simultaneously over the same communication lines


Before transmission, this information is converted
into fixed size cells

Chapter 16

28

ATM Devices


ATM network consists of two devices:


ATM Switch


ATM endpoint

Chapter 16

29

ATM Services

ATM Services

Permanent

Virtual

Circuits

(PVC)

Switched

Virtual

Circuits

(SVC)

Connectionless

Service

Chapter 16

30

ATM Reference Model


Reference model comprises of the following:


ATM layers


ATM planes



Chapter 16

31

Integrated Services Digital Network
(ISDN)


Involves digital telephony and data
-
transport
services offered by the regional telephone carriers


Permits transmission of voice, data, text, graphics,
music and video over existing telephone lines


Consists of following devices:


Terminals


Terminal Adapters


Network Termination Devices


Chapter 16

32

ISDN Devices

Chapter 16

33

ISDN Services


The information transmitted over the ISDN network
travels through the three logical digital communication
channels:


B
-
Channel
-

Carries user service information that
includes digital data, video and voice. It is the basic
user channel


D
-
Channel
-

Carries signals and data between the
user and the network.


H
-
Channel
-

Performs the same functions as that of
the B
-
Channels and operates at data rate of 64 Kbps.

Chapter 16

34

Broadband ISDN (BISDN)


Extension of ISDN


Used for technologies such as video conferencing
and file transfer


Provides two types of services as follows:


Interactive Services


Distributive Services

Chapter 16

35

Case Study


II


All the branches of MoneyMaker bank have to send
daily transaction details to the Mumbai branch. The
size of this file is very large. The bank uses a regular
telephone line and a standard modem to send this
file.

Chapter 16

36

Problem


Slow data transmission

Chapter 16

37

Suggested Solution



Setup an ISDN. Certain things are required to set
up an ISDN service which includes, a ISDN
modem or router, Service Profile Identifiers
(SPIDs) from the telephone company, the name
of the switch or the network type the phone
company uses, and account information from the
ISDN service provider.

Chapter 16

38

Fiber Distributed Data Interface


Based on ring topology and token passing


Two optical fibers used as follows:


Multimode optical fiber


Single
-
mode optical fiber


Two types of copper cables used as follows:


Category 5 Unshielded Twisted Pair copper wiring


IBM Type 1 Shielded Twisted Pair copper wiring

Chapter 16

39

Satellite Communication


Two parts of satellite communication are:


Uplink



Transmitter consisting of a ground
-
based
part


Transponder


The satellite
-
based part reflecting
signals towards receivers


Advantages:


Satellites can cover large areas of earth


I
t is commercially attractive


It is preferred instead of cables as maintenance
of cables is expensive and difficult

Chapter 16

40

Polling


Communication technique which determines when a
terminal is ready to send data


Round robin sequence is used by the computer to
continuously interrogate its connected terminals


Communication system comprises of the following:


A Master station


Number of slave stations each communicating with
the master station


A two
-
way transmission line connecting the master
station and the slave stations

Chapter 16

41

ALOHA


A simple communications scheme in which each
transmitter or source in a network sends data
whenever there is a frame to send is called as
ALOHA


Next frame sent only if the first frame reaches the
destination successfully


If the frame fails to reach the receiver, it is sent
again


Types of ALOHA:


Pure aloha


Slotted aloha

Chapter 16

42

Summary
-

I


WAN covers a large geographical area and consists
of two or more local area networks (LANs)


Circuit switching, message switching and packet
switching are types of switching technologies used
by WAN


Leased lines are the permanent point
-
to
-
point links
used for data communication


Circuit switching networks establish a direct physical
connection between a sender and a receiver before
communication occurs

Chapter 16

43

Summary


II


In message switching, each switch stores the whole
message and forwards it to the next switch


Packet switching network transmits messages in the
form of packets


The telephone system that uses copper wires to
carry analog voice data is called Public Switched
Telephone Network (PSTN)


Multiplexing is the technique that allows the
simultaneous transmission of multiple signals across
a single data link

Chapter 16

44

Summary


III


X.25 is a connection
-
oriented packet
-
switching
protocol which was earlier used by the Internet


Frame relay is a high performance WAN protocol
which operates at the physical and data link layers
and uses fiber optic cable and ISDN for digital data
transmission


ATM transmits data, voice and video signals
simultaneously over the same communication lines


ISDN digitizes the telephone network, to transmit the
information over the existing telephone wires


Chapter 16

45

Summary


IV


BISDN which an extension to ISDN used for high
speed data transfer application such as video
conferencing and the ATM technology for
transmitting information


FDDI is based on ring topology and token passing


Polling is a communication technique which
determines when a terminal is ready to send data