Network topology

Topology

Presented ByEngr. Md. Fazlul Kader

Assistant Professor, Dept. of APECE

University of Chittagong, Bangladesh

The Institute of Chartered Accountants of Bangladesh

Contents

Network Topology

Communication Protocol

Engr. Md Fazlul Kader

Network Topology

A network topology is how computers, printers

and other devices are connected over a network.

It is the layout pattern of interconnections of the

various elements (links, nodes, etc.) of a

computer network.

Network topologies may be physical or logical. Physical topology means the physical design of a

network including the devices, location and cable installation.

Logical topology refers to how data is actually transferred in a network as opposed to its physical design.


Main Types of Physical Topologies

Linear Bus (point-to-multipoint) topology

Star topology

Ring topology

Tree(Extended Star) topology

Mesh topology

Hierarchical topology


Linear Bus

A linear bus topology consists of a main run of

cable with a terminator at each end

All nodes(file server, workstations, and

peripherals) are connected to the linear cable.

Ethernet and LocalTalk networks use a linear

bus topology


Linear Bus


Linear Bus

Advantages of a Linear Bus Topology

Easy to connect a computer or peripheral to a linear bus.

Requires less cable length than a star topology.

Disadvantages of a Linear Bus Topology

Entire network shuts down if there is a break in the main

cable.

Terminators are required at both ends of the backbone

cable.

Difficult to identify the problem if the entire network shuts

down.

Not meant to be used as a stand-alone solution in a large

building.


Star Topology

A star topology is designed with each node (file server, workstations, and

peripherals) connected directly to a central network hub or concentrator.

Data on a star network passes through the hub or concentrator before

continuing to its destination.


Star Topology

Advantages of a Star Topology

Easy to install and wire.

No disruptions to the network then connecting or

removing devices.

Easy to detect faults and to remove parts.

Disadvantages of a Star Topology

Requires more cable length than a linear topology.

If the hub or concentrator fails, nodes attached are

disabled.

More expensive than linear bus topologies because of

the cost of the concentrators or hub.


Ring topology

Alternatively referred to as a ring network,

The ring topology is a computer network configuration where each

network computer and device are connected to each other forming a

large circle (or similar shape).

Each packet is sent around the ring until it reaches its final destination.

Today, the ring topology is seldom used.


Ring topology

Advantages of Ring Topology

1) This type of network topology is very organized.

2) Even when the load on the network increases, its performance is better than

that of Bus topology.

3) There is no need for network server to control the connectivity between

workstations.

4) Additional components do not affect the performance of network.

5) Each computer has equal access to resources.

Disadvantages of Ring Topology

1) Each packet of data must pass through all the computers between source

and destination. This makes it slower than Star topology.

2) If one workstation or port goes down, the entire network gets affected.

3) Network is highly dependent on the wire which connects different

components.


http://www.ianswer4u.com/2011/05/network-topology-types-of-network.html

http://www.ianswer4u.com/2011/05/bus-topology-advantages-and.html

http://www.ianswer4u.com/2011/05/star-topology-advantages-and.html

Tree Topology

A tree topology combines characteristics of linear

bus and star topologies.

It consists of groups of star configured workstations

connected to a linear bus backbone cable

Tree topologies allow for the expansion of an

existing network, and enable schools to configure a

network to meet their needs.


Tree Topology


Tree Topology

Advantages of a Tree Topology

Point-to-point wiring for individual segments.

Supported by several hardware and software venders.

Disadvantages of a Tree Topology

Overall length of each segment is limited by the type of

cabling used.

If the backbone line breaks, the entire segment goes

down.

More difficult to configure and wire than other

topologies.


Hierarchical Topology

The Hierarchical Topology is much like the Star Topology, except

that it doesn’t use a central node.

This type of topology suffers from the same centralization flaw as the

Star Topology.

If the device that is on top of the chain fails, consider the entire

network down.

Obviously this is impractical and not used a great deal in real

applications.


Mesh Topology

The Full-Mesh Topology It connects every single node together. This will create the most redundant

and reliable network around- especially for large networks.

If any link fails, we (should) always have another link to send data through.

The Partial-Mesh Topology The Partial-Mesh Topology is much like the full-mesh, only we don’t connect

each device to every other device on the network. Instead we only implement a

few alternate routes.


Mesh Topology

Advantages of Mesh topology

1) Data can be transmitted from different devices simultaneously. This

topology can withstand high traffic.

2) Even if one of the components fails there is always an alternative

present. So data transfer doesn’t get affected.

3) Expansion and modification in topology can be done without

disrupting other nodes.

Disadvantages of Mesh topology

1) There are high chances of redundancy in many of the network

connections.

2) Overall cost of this network is way too high as compared to other

network topologies.

3) Set-up and maintenance of this topology is very difficult. Even

administration of the network is tough.Engr. Md Fazlul Kader



Considerations when choosing a topology

Reliability of the entire system

Expandability of the system

Cost involved

Availability of the communication lines

Delays involved in routing information from

one node to another


Communication Protocol

A protocol is a set of rules and procedures

established to control transmission between two

points so that the receiver properly interpret the

bit stream transmitted by the sender.

Key Elements

Syntax

Semantics

Timing


Protocol Elements:

Syntax

Refers to the structure and format of the data,

meaning the order in which they are presented.

For example: A simple protocol might expect

The first 8 bits of the data to be the address of the

sender,

The second 8 bits to be the address of the receiver

The rest of the stream to be the message itself


Protocol Elements:Semantics

Semantics relates to the meaning of each

section of bits.

How is a specified pattern to be interpreted; and

what action is to be taken based on that

interpretation?

For instance does an address identify the route to

be taken or the final destination of the message?


Protocol Elements:Semantics

Timing refers to two vital characteristics:

when data should be sent and

how fast they can be sent.

For example if a sender produces data at 100

Mbps but the receiver can process data at only 1

Mbps, the transmission will overload the receiver

and data will be largely lost.


Roles of ProtocolFunctions for the efficient and error free transmission

Data Sequencing

It refers to breaking a long transmission into smaller blocks

and maintaining control

Data Routing

Routing algorithms are designed to find the best paths

between sources and destinations

Flow Control

A communication protocol prevents a fast sender from

overwhelming a slow receiver

Error Control

Detect errors and recover routines

Common Method of error correction: Retransmission


Roles of ProtocolFunctions for the efficient and error free transmission

Precedence and order of transmission

Rules to condition all stations about when to transmit their data and

when to receive data from other stations

Connection Establishment When two stations of a network want to communicate with each other,

the communication protocol establishes and verifies a connection

between them

Data Security

IT prevents access of data by unauthorized users

Log Information

Data communication software develop log information which

consists of all jobs and data communication tasks that have

taken place


The OSI Reference Model

The OSI model is based on a proposal

develop by ISO as a first step toward

international standardization of the protocols

used in the various layers.

The model is called ISO OSI (Open Systems

Interconnection) Reference Model.

Open system is a system open for

communication with other systems.

The OSI model has 7 layers

The OSI Reference Model

Layer Function Protocols

Network

Components7 Application Allows access to network services that support

applications;Provides application services for

File Transfer, Email, Remote Login

DNS; FTP;

SMTP;

TELNET;

Gateway

6 Presentation Translates from application to network format

and vice-versa. Format and encrypts/decrypts

data to be sent across a network

Gateway

5. Session Establishes, maintains and ends sessions

across the network. Deals with session and

connection coordination

NetBIOS Gateway

4. Transport Responsible for end to end error recovery and

flow control. Ensures complete data transfer.

TCP, UDP Gateway

3. Network Creates logical paths for transmitting data from

node to node. Include switching, routing and

forwarding

IP; RIP; Router

2. Data Link Handles data frames between the Network and

Physical layers. Two sublayers: Medium

Accesses Control (MAC) And Logical Link

Control (LLC)

802.3 CSMA/CD (Ethernet)802.5 Token Ring

Bridge

Switch

1. Physical Transmits raw bit stream over physical cable IEEE 802.2

ISDN

Repeater

Hubs

Amplifier

THANK YOU


Education

Network topology