chapter 4. understand network connectivity. peer-to-peer network & client-server network ...
TRANSCRIPT
Prepared by Saher H. Mohammed 2
Understand network connectivity.
Peer-to-Peer network & Client-Server network
Understand network topology
Star, Bus & Ring topology
Understand congestion control techniques
Network equipment
Chapter Objective
Prepared by Saher H. Mohammed 3
The arrangement of nodes (hosts, machines, computers,
printers, etc.) is called topology.
The way the networks are arranged, constructed is called
topology.
Network Connectivity Basics
Node 1 Node 2 •This is called a n = 2 network•If both the nodes are computers, then it is called a point-to-point network
Prepared by Saher H. Mohammed 4
Network consist of two or more nodes, connected by one or
more channels.
When many computers and peripherals are connected to a
common communication channel, it is called a multi-point
network or multi-node network.
Network Connectivity Basics
Node 1 Node 4Node 2 Node 3
Printer
Prepared by Saher H. Mohammed 5
Any devices such as a hard disk or printer that are accessed
and used by all the nodes on the network are called shared
resources.
Two kinds of relationship exist between the connected nodes
Peer-to-Peer network.
Cooperative processing.
Distributed processing.
Client – Server network.
Relationship between Nodes
Prepared by Saher H. Mohammed 6
In a Peer-to-Peer network, all the computers in the network are of
same standing (level) and neither is a master or a slave (Server-
Client).
A way to enhance the use of resources is cooperative processing,
the sharing of processing tasks between two or more processors,
either within or between computers.
Distributed processing is the dispersion of the data processing
among computers in multiple sites.
Peer-to-Peer network
Prepared by Saher H. Mohammed 7
In Client - Server relationship, the nodes are not equal. One
node is the Server (master) and the rest of the nodes are
Clients (slave).
All the clients request service from the server, such as file
space, common printer, and shared processing.
Client – Server Architecture
Prepared by Saher H. Mohammed 8
Client – Server Architecture
Hub
Client
Client
Client
Client
Client
Server
Prepared by Saher H. Mohammed 9
In the client – server architecture, if the clients have no
storage nor the processing capabilities, then the clients are
called dumb terminal.
Example old mainframes systems.
In current client – server architecture, most of the clients have
processing capabilities.
Client – Server Architecture
Prepared by Saher H. Mohammed 10
The client – server architecture is the basis for the current
day Local Area Networks and Wide Area Network.
In client – server architecture, the client can be of two types
Thin Client – they have very limited processing and storage
capabilities.
Example – Smart phones.
Fat Client – they have large storage and processing capabilities.
Example – Desktop and Laptops.
Client – Server Architecture
Prepared by Saher H. Mohammed 11
Client – Server Architecture
Hub
Client - Laptop
Client – Smart phone
Client - IPad
Client - Desktop
Client - Laptop
Server
Prepared by Saher H. Mohammed 12
Advantages
Resource sharing.
Share processing.
Easy maintenance.
Client – Server Architecture
Prepared by Saher H. Mohammed 13
Network Operation systems
Example Microsoft Windows 2003/2008 Server OS.
A networking device
Hub, Switch, Router.
Network Interface Card (NIC)
Media (Wire)
Components of a Network
CATegory Definition
Means Usage
3 10BaseT
10 Mbps on baseline Ethernet
5 100BaseT
100 Mbps on baseline Fast Ethernet
6 1000BaseT
1000 Mbps on baseline
Giga Ethernet
Prepared by Saher H. Mohammed 14
Geographical arrangement of a network’s components is also
called a topology.
Topology can be of two types
Physical Topology – how the wiring is laid out.
Electrical Topology – how the nodes use the path.
Toplology
Prepared by Saher H. Mohammed 15
The most common type of the network topology.
All the cables from the end nodes (clients and server) are
connected to a central point – Hub or a Switch.
Star Topology
Client - PC
Client - Laptop
Client - Scanner
Client - Printer
Client - PC
Active Node
Client
Client
Server Client
Client Hub
Prepared by Saher H. Mohammed 16
In the star topology, the end nodes acquire the attention of
the central node before communication can take place, this
process is called polling.
One disadvantage of star topology is congestion.
If the central active node is busy, then the network becomes
congested.
Star Topology
Prepared by Saher H. Mohammed 17
In a bus topology, all the nodes are connected to a single,
central wire called as bus.
One major drawback of a bus topology is the single point of
failure.
If the central wire fails, then the entire network breaks down.
Bus Topology
Prepared by Saher H. Mohammed 19
In the ring topology, each node is connected to the one
above node and the one below node.
All the messages pass around the ring and each transmitted
node will see part of the message.
In order to transmit, a node must possess a token.
At any time, only one node can have a token.
Ring Topology
Prepared by Saher H. Mohammed 21
Collision occurs when two or more nodes transmit at the
same time.
Collision can make all the communication in the network to
stop.
There are two methods of collision control
Collision Avoidance.
Collision Detection.
Collision Control
Prepared by Saher H. Mohammed 22
In a star topology, all the end nodes are connected to a
central node. So, before communicating, the end nodes must
get the attention of the central node – polling.
Central node will poll/ query all the end nodes to check if some end
node is ready to transmit or the central node is ready to receive any
message from the end nodes.
The end nodes will poll/ query the central node to signal that they are
ready to transmit, and will wait till the central node is ready.
Collision Avoidance – Star Topology
Prepared by Saher H. Mohammed 23
Only one node in the ring topology will have the token, only
that node will have the permission to send the messages.
Once the node is finished with sending the message, it will
release the token for the other nodes to use.
In the ring topology, messages are passed from one node to
the next until the messages reaches the destination.
Collision Avoidance – Ring Topology
Prepared by Saher H. Mohammed 24
Collision detection – react to the collisions, instead of
avoiding it.
The bus topology uses carrier sense multiple access/
collision detection (CSMA/ CD).
Carrier sense is the primary way of gaining the access to the
central wire/ bus.
Collision Detection – Bus Topology
Prepared by Saher H. Mohammed 25
The node willing to transmit will sense the carrier (central
wire). If there are no signals on the carrier, the node will
broadcast the message.
All the nodes in the network will get the message, but only
the correct recipient will be able to access the message.
Collision Detection – Bus Topology
Prepared by Saher H. Mohammed 26
To build a network, certain networking devices are used
Repeater.
Hub.
Switch.
Router.
Gateway.
Bridge.
Network Equipments
Prepared by Saher H. Mohammed 27
A repeater is a simple hardware device that receives a weak
signal and regenerates it.
Since the repeater creates a new signal, the distortion or
attenuation is removed and the signal is made stronger.
Repeaters are used at Layer 1( Physical) of the OSI Model.
Repeaters are generally used to extend the coverage of a
network by extending the length of the segment.
Repeater
Prepared by Saher H. Mohammed 29
A hub is a hardware device that physically connects multiple
cables, providing a common connection point.
Hubs are passive devices. They will forward a message to all
the nodes connected via the ports.
Hubs will divide the bandwidth among all the nodes.
Hubs are used at Layer 1( Physical) of the OSI Model.
Hub
Prepared by Saher H. Mohammed 31
A switch is a special type of hub.
A switch is an active device.
Switch operates at the second layer (DLL) of OSI model.
A switch will forward the packets only the correct destination.
A switch will not divide the bandwidth, thus the transmission
speed is higher.
Switch
Prepared by Saher H. Mohammed 33
A bridge is software or a hardware device that connects two
LAN’s or two segments of the same LAN.
Bridge is a layer 2 (DLL) device.
Two LAN’s or the two segments of the same LAN must use
the same data link protocol.
Example (Ethernet, Token, Ring)
Bridges
Prepared by Saher H. Mohammed 34
Transparent Bridge: Connects two LAN’s that use the same
data link protocol.
Ethernet network– Ethernet network.
Token ring network – Token ring network.
Translating Bridge: Connects two LAN’s that use different data
link protocol.
Ethernet network– Token ring network.
Token ring network – Ethernet network.
Bridges Types
Prepared by Saher H. Mohammed 36
Routers are hardware devices used to forward the data
packets between different networks.
Routers intelligent devices, they have routing protocols and
store the path information in the routing tables.
Routers operate at the third layer (Network) of OSI model.
Router
Prepared by Saher H. Mohammed 37
Routers can be static or dynamic.
Static – the routing table cannot be changes.
Dynamic – the routing table can change depending on the situation to
find the next best route.
Routers
Prepared by Saher H. Mohammed 39
A gateway is a node on a network that serves as an entrance
to another network.
Gateway is a device that uses software to connect networks
with different architecture by performing protocol conversion
at the application level.
Gateway operates at all the 7 layers of the OSI Model.
Gateways
Prepared by Saher H. Mohammed 41
Network Device OSI Layer
Repeater Layer 1 – Physical Layer
Hub Layer 1 – Physical Layer
Switch Layer 2 – Data Link Layer
Bridge Layer 2 – Data Link Layer
Router Layer 3 – Network Layer
Gateway All 7 Layers
OSI Levels of Network Devices
Prepared by Saher H. Mohammed 42
Gateways
Routers
Switches
Comparison
Going up from switches – Routers – Gateways, the capabilities, complexities and the cost increases.