Networks Basics
Network : connecting two nodes or more to each other.
What is the benefit of networks ?
The benefit of networks is resources (services) sharing.
What about Computer Networks ?
Sharing of resources (services) on computer networks.
Resources (services) in computer networks can be :
- Hardware (like printer).
- Software (like files, DB).
Networks Basics(Cont…)
Every peripheral needs an interface to connect it to the computer.
Examples of peripherals :
Mouse, keyboard, monitor, media.
Media is peripheral, so it needs NIC (like ethernet card).
Network Interface Card (NIC) : An expansion board that provides a network
communication connection to and from a PC. Many newer desktop and laptop
computers have an ethernet NIC built into the motherboard.
Networks Basics(Cont…)
The NIC (network adapter) performs the following functions :
- Receives data from the computer's operating system and converts it
into electrical signals that are transmitted onto the cable.
- Receives electrical signals from the cable and translates them into
data that the computer's operating system can understand.
- Determines whether data received from the cable is intended for the
computer.
- Controls the flow of data between the computer and the cabling
system.
Networks Types
Networks are divided into 3 types :
1. Local Area Networks (LANs).
2. Wide Area Networks (WANs).
3. Metropolitan Area Networks (MANs).
Networks Types(Cont…)
Local Area Networks (LANs) are designed to :
- Operate within a limited geographical area.
- Allow multi-access to high bandwidth media.
- One single interface for each host (Point to multipoint).
- Control the network privately under local administration
(installation, troubleshooting, developing).
- Provide full-time connectivity to local services.
- Connect Physically adjacent devices.
- All the devices must be owned by the customer.
Networks Types(Cont…)
Wide Area Networks (WANs) are designed to :
- Operate over wide geographical area.
- Allow access over serial interfaces operating at lower speeds.
- Provide full time and part time connectivity.
- Connect devices separated over wide, even global areas.
- There is an fee paid to the provider.
Networks Types(Cont…)
Peer-to-Peer vs. Client/Server Architecture
In peer-to-peer networks, the connected computers have no centralized
authority. From an authority viewpoint, all of these computers are equal. In
other words, they are peers. If a user of one computer wants access to a
resource on another computer, the security check for access rights is the
responsibility of the computer holding the resource.
Each computer in a peer-to-peer network can be both a client that requests
resources and a server that provides resources.
In peer-to-peer network each user is responsible for local backup. Security
considerations are minimal. A limited number of computers are involved.
Peer-to-Peer vs. Client/Server
Architecture(Cont…)
Peer-to-Peer vs. Client/Server
Architecture(Cont…)
In contrast to a peer-to-peer network, a client/server network uses a network
operating system designed to manage the entire network from a centralized
point, which is the server. Clients make requests of the server, and the server
responds with the information or access to a resource.
Network Topologies
There is five main topologies that are used to design the networks :
1. Bus.
2. Ring.
3. Star.
4. Mesh.
5. Hybrid.
Network Topologies(Cont…)
Bus
- Not fault tolerant.
- Broadcasts.
- Collisions.
- Bad wires.
Network Topologies(Cont…)
Ring
- Not fault tolerant.
- Broadcasts.
- No collisions.
- Difficult to implement.
- Cost.
- low speed.
Network Topologies(Cont…)
Star
- Broadcasts Depends on the device used.
- Collisions depends on the device and wires used.
- Easy to implement.
- Medium cost.
Network Topologies(Cont…)
Mesh
- Fault tolerant.
- Very high cost.
- There is a limitation in the number of PC’s.
- Very difficult to implement.
Network Topologies(Cont…)
You should balance the following considerations when choosing a physical
topology for your network :
- Cost.
- Ease of installation.
- Ease of maintenance.
- Cable fault tolerance.
Network Topologies(Cont…)
Bandwidth and Throughput
In the world of communications bandwidth is the gap between the highest and
lowest frequencies employed by network signals.
In the world of computer bandwidth is the :
- amount of information that can flow through a network connection
in a given period of time.
- data-carrying capacity of a network or data transmission medium.
Bandwidth available for LANs :
- 10 Mbps.
- 100 Mbps.
- 1000 Mbps.
- 10000 Mbps.
Bandwidth and Throughput(Cont…)
Throughput is the rate of information arriving at, and possibly passing
through, a particular point in a network system.
Throughput is the actual measured bandwidth.
Bandwidth and Throughput(Cont…)
Transfer time calculation :
Transfer time = (size of data) / (bandwidth)
T = S / BW
Typical Media Types
Although it is possible to use several forms of wireless networking, such as
radio frequency and infrared, the majority of installed LANs today
communicate via some sort of cable.
We’ll look at three types of cables :
- Coaxial.
- Twisted pair.
- Fiber optic.
Typical Media Types(Cont…)
Typical Media Types(Cont…)
Typical Media Types(Cont…)
Typical Media Types(Cont…)
Typical Media Types(Cont…)
Typical Media Types(Cont…)