Chapter 01 Introduction ■ Data Communications and Networking

Data Communications

The exchange of Information between two devices through a transmission medium

Five components of data communication

1. Message

2. Sender

3. Receiver

4. Transmission Medium

5. Set of rules (Protocol)

Message:

Information today comes in different forms such as text, numbers, images, audio, and video.

Networks

A network is a set of devices (called nodes) connected by communication links

Node

can be host (a computer, printer, cell phone) or networking devices (routers, switches, modem, etc…)

Link

is a communication pathway that transfer data from one device to another ■ Link can be wired or wireless

Type of network connections

Point-to-Point: dedicated link between two devices Multipoint : shared link between more than two devices

A network must be able to meet a certain number of criteria. The most important of these are:

1. Performance

2. Reliability

3. Security

Performance

Depends on factors such as: # of users, type of transmission medium, capabilities of Network hardware, Network software efficiency

Evaluated by: Throughput (amount of data a user can send) Delay (measured in transit time, and response time)

To have good performance,

we need more throughput and less delay

Reliability

Measured by:

Frequency of failure

Time it takes a link to recover from the failure

Security

Protecting data from unauthorized users, and damage, applying security policies for recovery from breaches and data losses

Types of Data Flow

• Simplex

• Half-duplex

• Full-duplex

Simplex:

one-way data flow like radio broadcasts or keyboards to monitors

Half-duplex:

data can travel in both directions between devices, but only one direction at a time, like a walkie-talkie where you push to talk

Full-duplex:

allows devices to send and receive data simultaneously, like a phone call, using separate channels or frequencies for each direction

Topology:

The way in which a network is physically built or The way in which devices interconnect across the network

mesh topology

Dedicated point-to-point link to every other node ▪Number of links = N(N-1)/2 ▪ Advantages ▪ Dedicated links 🡺 secure, no traffic problems (no congestion) ▪ Robust: if one link fails, the network will still work ▪Easy to discover faulty links ▪ Disadvantages? ▪ Difficult to install & update (too much wiring) ▪ Expensive (why?) ▪ Number of Network interface cards (NIC) or Number of I/O ports = (N-1 )per device ▪ Number of cables = Number of links