Chapter16. Networking Principles

8/22/2019 Chapter16. Networking Principles

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For internal circulation of BSNL only

E1-E2 Management

Chapter 16

Networking Principles, LAN, Intranet, Internet


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Networking Principles

Reasons why computers need to be

networked are -

to share resources like files, printers, modems, fax

machines etc.

to share application software like MS Office, AdobePublisher etc.

increase productivity by sharing data amongst users


Communication Link


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LAN

Local Area Networks (LAN) is a small network

which allows easy access to other computers or

peripherals

Characteristics of a LAN -1) Physically limited distance (< 2km)

2) High bandwidth (> 1mbps)

3) Inexpensive cable media (coax or twisted pair)

4) Data and hardware sharing between users

5) Owned by the user


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Study of LAN


Study of LAN

LAN Topologies

Medium access

control technique

Transmission

medium /Network

Components


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A) LAN Topologies

Bus topology is multipoint.

One long cable acts as a backbone to link all the devices

in the network.

Nodes are connected to bus by drop lines and taps.


Tap Tap Tap Tap

Cable EndCable End

Drop line Drop line Drop line Drop line

Flow of Data

1. BUS TOPOLOGY


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A) LAN Topologies

The central hub in the tree is an active hub.

An active hub contains a repeater.

The secondary hubs can be active or passive.


2. TREE TOPOLOGY

HUB

HUB HUB


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A) LAN Topologies

Messages are passed from one host to the next until theyreach the destination host.

Typically messages pass the whole way around the ring and

are checked and removed by the hosts that sent them


3. RING TOPOLOGY

Data flow

A

B

C

D

APacket meant

for A will

reach to System A


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A) LAN Topologies

Each device has a dedicated point-to-point link to a centralcontroller, called a hub.

The Hub acts as an exchange point


4. STAR TOPOLOGY

HUB


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B) Medium Access Control

Controlling access is needed to provide for an orderly

and efficient use of the transmission medium. This is

the function of medium access control (MAC) protocol.

Two Types:

1. Centrally Access Control

2. Distributed Access Control (Used in LAN)



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LAN uses

the Asynchronous (dynamic) approach

Round Robin

Reservation

Contention



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Round Robin

Each station in turn is

given an opportunity

to transmit in logicalsequence

Useful when the data

traffic has a stream

or bursty characteristic

Reservation Well suited for

stream traffic

A station wanting to

transmit, reserves

future slots for an

extended or even an

indefinite period

ContentionAppropriate for the

bursty traffic

In this technique, no

control is required todetermine whose turn

it is; all stations

contend for time.

These techniques are

by nature distributed.



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Bus Topology Ring Topology Switched

Topology

Round

Robin

Token Bus

(IEEE 802.4) Polling

(IEEE 802.11)

Token Ring

(IEEE 802.5& FDDI)

Request/ Priority

(IEEE 802.12)

Reservation DQDB

(IEEE 802.6)

___ ___

Contention CSMA/CD

(IEEE 802.3)

CSMA

(IEEE 802.11)

___ CSMA/CD

(IEEE 802.3)

Standardized Medium Access Control Techniques



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MACcontrol

DestinationMAC

Address

SourceMAC

Address

LLC PDU CRC

DSAP SSAP LLC control Information

MAC Frame Format


I/G DSAP value C/R SSAP value

MAC Frame

LLC PDU

1 octet

1 or 2 Variable

LLC PDU with generic MAC Frame format


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MAC Frame Format

The MAC layer receives a block of data from the LLC layer and is

responsible for performing functions related to medium access and

for transmitting the data.

MAC implements these functions, by making use of protocol data

unit at its layer

The fields of this frame MAC control: Contains any protocol control information needed for

the functioning of the MAC protocol.

Destination MAC Address:

Source MAC Address:

LLC: The LLC Data from the next higher layer.

CRC: The cyclic redundancy check field (This is an error-detecting

code)



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C) Network Components

Puts the data into packets and

transmits packet onto the

network.

May be wired or wireless


1. Network Interface Cards (NICs)


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The choice of cable depends upon1. cost 4. Speed

2. distance 5. Bandwidth

3. Number of computers involved


2. Cabling

Twisted - Pair CableCoaxial cable

Optical Fiber


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It amplify the incoming signal received from

one segment and send it to all other

attached segments & allows the distance

limitations of network cabling to be

extended.

Repeaters also allow isolation of segments

in the event of failures or fault conditions.

Repeaters simply allows to extend network

distance limitations. It does not give anymore bandwidth or allow to transmit data

faster.


3. Repeater


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Bridges interconnect Ethernet segments. Most bridges support filtering

and forwarding & Spanning Tree Algorithm.

Follows the IEEE 802.1D specification standard

learns about the network and the routes & Packets are passed onto

other network segments based on the MAC layer.

The bridge builds up internal table to determine which segment incoming

frames should be forwarded to..


4. Bridges

Network Segment A

Network Segment B


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A device that connects any number of LANs. It uses standardized

protocols to move packets to their destination using routing tables

More sophisticated than bridges, connecting networks of different types

Forwards data depending on the Network address (IP), not the Hardware

(MAC) address. and thus can have multiple network clients.

Resides on network layer of the OSI model


5. Router


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Routing

Routable Protocols

DECnet

IP

IPX

OSI

XNS

DDP (AppleTalk)

Protocols which are not routableLAT (local area transport,

NetBEUI



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An unintelligent network device that sends

one signal to all of the stations connected

All computers/devices takes the data that

comes into a port and sends it out all the

other ports in the hub.

hubs are used to add and remove

computers in the network.

Ports are 10BaseT type

Resides on Layer 1 of the OSI model


6. HUB


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Ethernet and fast Ethernet (CSMA/ CD)

carrier-sense multiple access with collision detection (CSMA/CD).

The most commonly used medium access control technique forbus/ tree and star topologies

In bus topology, with CSMA/CD the data transmits at 10 Mbps,.

follows IEEEs 802.3 specification.


SN Traditional topology Linear Bus

1 Other Topologies Star Bus

2 Type of Architecture Baseband

3 Access Method CSMA/ CD4 Specifications IEEE 802.3

5 Transfer Speed 10 Mbps or 100 Mbps

6 Cable Types Thicknet, Thinnet, UTP

Ethernet Features


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Chapter16. Networking Principles