Network topology
-
Upload
chittagong-university -
Category
Education
-
view
73 -
download
0
Transcript of Network topology
Topology
Presented ByEngr. Md. Fazlul Kader
Assistant Professor, Dept. of APECE
University of Chittagong, Bangladesh
The Institute of Chartered Accountants of Bangladesh
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.
Engr. Md Fazlul Kader
Main Types of Physical Topologies
Linear Bus (point-to-multipoint) topology
Star topology
Ring topology
Tree(Extended Star) topology
Mesh topology
Hierarchical topology
Engr. Md Fazlul Kader
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
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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
Engr. Md Fazlul Kader
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
Engr. Md Fazlul Kader
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
Engr. Md Fazlul Kader
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?
Engr. Md Fazlul Kader
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.
Engr. Md Fazlul Kader
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
Engr. Md Fazlul Kader
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
Engr. Md Fazlul Kader
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