Chapter 2 1

Topologies

Chapter 2

Chapter 2 2

Chapter Objectives

Explain the different topologies Explain the structure of various topologies Compare different topologies

Chapter 2 3

Recall

LAN types are Ethernet, Token Ring, Token bus and Fiber Distributed Data Interface (FDDI).

OSI layers are Physical, Data Link, Network, Transport, Session, Presentation and Application layer

The factors of network selection criteria are Performance, Reliability and Security

Standards organization is unit which develops, maintains, improves, amends and revises standards

Chapter 2 4

Introducing Topologies

Topology refers to physical or logical arrangement of network

Physical topologies are Single Node Bus Star Ring Mesh Tree Hybrid

Chapter 2 5

Single Node Topology - I

Single device, at times device called dumb terminal is connected to the server

Devices operates on files from server and returns them back after completing task

Chapter 2 6

Single Node Topology - II Advantages:

Easy to install, configure and manage

Least expensive

Single cable is required

Disadvantages:

Network consists of single device

Dumb terminal is dependent on server

Chapter 2 7

Bus topology - I

All devices are connected to a common cable called trunk

Maximum segment length of cable is 200 m Maximum of 30 devices per segment

Chapter 2 8

Bus topology - II

Server is at one end and devices are at different positions

50 ohm terminator is used Devices are not responsible for data transmission Number of collisions are more Daisy chain method can be used to add more

devices

Chapter 2 9

Bus topology - III

Advantages:

Installation of devices is easy

Requires less cable compared to star topology

Less expensive and works better for smaller networks

Disadvantages:

If backbone breaks, entire network gets down

Difficult to isolate problems

Limited number of devices

Chapter 2 10

Star Topology - I Each device is connected to a central device called

hub through cable Data passes through hub before reaching

destination

Chapter 2 11

Star Topology - II

Advantages:

Easy to install, configure, manage and expand

Centralized management

Addition or removal of device does not affect the whole network

Disadvantages:

Requires more cable

Failure of hub affects entire network

More Expensive

Chapter 2 12

Case Study 1

Hyderabad branch of the MoneyMaker bank has built an insurance department in such a way that each device is connected to one another. This department consists of seven agents. It is required that agents should handle only their specific clients since the information is confidential. But in the existing topology the data is not secured. So, Smith, the network administrator, wants to switch over to other topology.

Chapter 2 13

Problem

Design a new type of network for this department.

Chapter 2 14

Suggested Solution

The current topology implemented by the bank is mesh in which information is shared between different devices. To obtain security of data star network seems to be the best choice. It also provides ease of troubleshooting, centralized management and ease of reconfiguration.

Chapter 2 15

Ring Topology - I

Devices are connected in a closed loop

All devices have equal access to media

Device waits for its turn to transmit

Most common type is Token Ring

Chapter 2 16

Ring Topology - II

Advantages:

Data travels at greater speed

No collisions

Handles large volume of traffic

Disadvantages:

More cabling is required compared to bus

One faulty device affects the entire network

Addition of devices affect network

Chapter 2 17

Dual Ring Topology

Consists of two independent primary and secondary rings

Secondary ring is redundant, used only when primary stops functioning

Chapter 2 18

Mesh Topology - I

Used in WANs to interconnect LANs

Every device is connected to every other device

Use routers to determine the best path of communication

Chapter 2 19

Mesh Topology - II

Types

Full mesh Partial mesh

Full mesh topology – All devices are connected to each other

Partial mesh topology - Some devices are connected to only those with whom they exchange most of the data

Chapter 2 20

Mesh Topology - III

Advantages:

Improves fault tolerance

Failure of one link does not affect entire network

Centralized management is not required

Disadvantages:

Difficult to install and manage

Each link from one device to other requires individual NIC

Very much expensive

Chapter 2 21

Tree Topology - I

Connects groups of star networks

Devices are wired to root hub

Root hub is connected to second level devices

Lowest level devices are smaller computers

Chapter 2 22

Tree Topology - II

Advantages: Easy to add new

devices Point-to-point wiring for

each device Fault detection is easy

Disadvantages: Difficult to configure If backbone breaks,

entire network goes down

More expensive

Chapter 2 23

Hybrid Topology - I

Combines two or more different physical topologies Commonly Star-Bus or Star-Ring Star-Ring uses Multistation Access Unit (MAU)

Chapter 2 24

Hybrid Topology - II

Advantages:

Used for creating larger networks

Handles large volume of traffic

Fault detection is easy

Disadvantages:

Installation and configuration is difficult

More expensive than other topologies

More cabling is required

Chapter 2 25

Case Study 2

MoneyMaker Bank at Mumbai has implemented a star topology in their IT department. All computers are connected to the central switch. In the Loan department, all computers are connected in closed loop format. Network administrator, John wants to connect these two networks so that data can be shared among different departments.

Chapter 2 26

Problem

Connect two different departments

Chapter 2 27

Suggested Solution

The administrator can join these two star and ring networks to form a hybrid network with the help of Multistation Access Unit (MAU). It is a centralized hub. Ensure that there is no break in the link between two computers in a ring network and switch in star network is working properly.

Chapter 2 28

Summary - I

Network is an interconnection of many communicating entities that are connected for the purpose of data communication

Topology describes the way in which networking devices are connected to each other

Physical topologies are how the wires are interconnected, while logical topology is how the network behaves and interoperates

Different types of topologies are Single Node, Star, Bus, Ring, Mesh, Tree and Hybrid

Chapter 2 29

Summary - II

In a single node topology, just a single device called dumb terminal is connected to the server

Bus topology connects each device to a single cable and at either end of the cable terminator is used to remove unsent data from the cable

In star topology, multiple devices are connected to a central connection point known as hub or switch

In a ring topology, data travels around the loop in one direction and passes through each device

Chapter 2 30

Summary - III

In a mesh topology, every device is connected to each and every node in the network with many redundant interconnections at least two paths to and from every node

Tree topology connects multiple star networks to other star networks using bus topology

Hybrid topology is a combination of different topologies such as Star-Bus or Star-Ring