The document discusses various network topologies including physical and logical topologies. It describes common topologies like bus, ring, star, and tree and provides their advantages and disadvantages. The document also discusses hybrid topologies that combine two or more standard topologies. It recommends a star bus hybrid topology for its ease of use, monitoring, security and cost effectiveness.

1. Roshan Basnet
Student id: 306939
1.
Network topology is a systematic arrangement of computers and its elements, including its nodes and
connecting lines.
2. The two classifications of network topology are:
a.Physical topology : The mapping of the nodes of a network and the physical connections between
them – i.e., the layout of wiring, cables, the locations of nodes, and the interconnections between the
nodes and the cabling or wiring system.
b. Logical Topology : is also called as Signal Topology.It is a network computing term used to describe
the arrangement of devices on a network and how they communicate with one another.
Logical topologies are bound to network protocols and describe how data is moved across the network
3. Four most common topologies used in industry are:
Bus topology
Ring topology.
Star topology.
Tree topology
a) Bus topology: In this topology each computer or server is connected to the single bus cable
through some kind of connector.
Advantage:
1. low wiring complexity.
2. Economical and easy to manage.
Disadvantage:
1. Limited Network.
2. A cable end which is not correctly terminated can make the entire bus inoperative, especially
with a high transmission speed.

2. b) Ring Topology: In this topology each computer is connected to the network in a ring and each
computer has a unique address which is used for identification purposes. The signal passes
through each computer connected to the ring in one direction.
Advantage:
Very orderly network where every device has access to the token and the opportunity to
transmit
Performs better than a star topology under heavy network load
Can create much larger network using Token Ring.
Does not require network server to manage the connectivity between the computers
Disadvantage:
One malfunctioning workstation or bad port in the MAU can create problems for the
entire network
Moves, adds and changes of devices can affect the network
Network adapter cards and MAU's are much more expensive than Ethernet cards and
hubs
Much slower than an Ethernet network under normal load
c) Star Topology: In a star topology all computers are connected to a central hub, which controls
the network communications, and can communicate with other hubs. Range limits are about
100 meters from the hub.
Advantages
Good performance
Reliable (if one connection fails, it doesn't affect others)
Easy to replace, install or remove hosts or other devices
Disadvantages
Expensive to install
Hub

3. Extra hardware required
d) Tree Topology: This network topology is also referred as hierarchical network. In this
topology central 'root' node (the top level) is connected to more other nodes that are on
lower level in the hierarchy with a point-to-point link between each of the second level
nodes and the top level central 'root' node, while each of the second level nodes that are
connected to the top level central 'root' node will also have one or more other nodes that
are one level lower in the hierarchy (i.e., the third level) connected to it.
Advantages :
Point-to-point wiring for individual segments.
Supported by several hardware and software companies.
Disadvantage:
More complicated network.
Expensive.
3. Hybrid Topology: It is a combination of any two or more network topologies. A hybrid topology
always accrues when two different basic network topologies are connected.
1st
level
2nd
level
hub hub

4. Advantage:
It allows coexistence and cohabitation by integrating different network technology to work together.
Disadvantage: It is very expensive.
Needs frequent support to maintain them.
5.Two common type of hybrid Topology are:
• A Star ring network : The Star Ring is a combination of ring and star topologies. The hubs in a star
ring are connected in a star pattern by the main hub.
This network consists of two or more star topologies connected using a multistation access unit
(MAU) as a centralized hub.
• A Star Bus network : This networking topology uses hubs for workgroups or departmental
local area networks (LANs) which is connected by using a network bus to form a single network. Star bus
topology is a combination of star topology superimposed on a backbone bus topology.
It consists of two or more star topologies connected using a bus trunk (the bus trunk serves as the
network's backbone).
6)Some organization uses hybrid topology rather than the normal topology because of the following
reasons:

5. a) use a combination of any two or more topologies in such a way that the resulting network
does not exhibit one of the standard topologies
b) Hybrid topology allows coexistence and cohabitation by integrating different network
technology to work together.
c) Better functionality.
7)Some topology requires end points to be terminated because Without termination, when the
signal reaches the end of the wire, it bounces back and travels back up the wire. When a signal
echoes back and forth along an unterminated bus, it is called ringing. To stop the signals from
ringing, terminators are attached at either end of the segment. The terminators absorb the
electrical energy and stop the reflections.
8) In a ring topology the funtion of Token is to transmit attached data from source to destination
computer. Token frame is repeated from station to station until arriving at a station that needs to
transmit data. When a station needs to transmit data, it converts the token frame into a data frame
for transmission. Once the sending station receives its own data frame, it converts the frame back
into a token. If a transmission error occurs and no token frame, or more than one, is present, a
special station referred to as the Active Monitor detects the problem and removes and/or reinserts
tokens as necessary
9) Being a Network Designer I would suggest to go with Star Bus Topology because of easy use
,easy to monitor the network , security and cost effectiveness..