Chapter1

Data Communications

the exchange of data between two devices via some form of transmission medium

Effectiveness of Data Communications System

Delivery, Accuracy, Timeliness, Jitter

Components of Data Comms System

Message, Sender, Receiver, Transmission Medium, Protocol

Message

image, text, numbers, audio, video

Simplex

one way communication

Half duplex

each station can send and receive but not at the same time

Full duplex

both stations can send and receive simultaneously

Network

Interconnection of a set of devices capable of communication

Host

device like a computer, PC, server

Connecting device

router, switch, modem

Network Criteria

performance, reliability, security

Point to point

a dedicated link between decices

Multipoint

multiple devices share one link

Physical topology

how a network is laid out physically

Mesh topology

each device is linked to all other devices

Star topology

each device has a dedicated pint to point link only to a central controller

Bus topology

all devices connected by one bus

Ring topology

all devices connected to 2 others, follows a loop pattern

LAN

local area network, consists of hosts and connections

WAN

wide area network, consists of connecting devices to LANS

Protocol

defines the rules that both sender and receiver need to follow in order to communicate effectively

TCP/IP Protocol Suite

Application, Transport, Network, Data link, Physical

OSI Model

Application, Presentation, Session, Transport, Network, Data Link, Physical

Protocol Layering Principles

1. 2 Direction communication

2. two objects under each layer at both sites should be identical

Advantages of Multipoint over point to point

ease of installation and low cost

What is the unit of data at the Application layer?

message

What is the unit of data at the Network layer?

datagram

What is the unit of data at the data link layer?

Frame

Layers reached by a Router

Network, Data Link, Physical

Layers reached by a Switch

Data link, Physical

Layers reached by a Host

Application, Transport, Network, Data Link, Physical

Physical Layer

Responsible for carrying individual bits in a frame across the link

Data Link Layer

Responsible for taking a data gram and moving it across the link

Network Layer

Creates a connection between source and destination computers

Transport Layer

Gets message from the application layer, makes a packet and sends across.

Application Layer

Process to Process communication.