Introduction network Protocol

A protocol is a set of rules that governs the communications between computers on a network

These rules include guidelines that regulate:

– the method of access, – types of cabling and– speed of size data transfer

PROTOCOL =

SET OF RULES ABOUT

COMMUNICATIONS BETWEEN NETWORKS!

The most common protocols are:

Ethernet Local Talk Token Ring FDDI ATM

Protocol = a formal description of a set of rules and conventions that govern how devices on a network exchange information

Did you ever wonder what HTTP in web addresses was about? It stands for HyperText Transfer Protocol

Ethernet

Most widely used Uses an access method

called CSMA/CD (Carrier Sense Multiple Access/Collision Detection

What does that mean?

Each computer in the network ‘listens’ to the cable before sending anything through the network. If the network is clear, the computer will transmit.

If another computer is already transmitting on the cable, the computer will wait and try again when the line is clear

A bit like waiting for some one to get off the telephone

Ethernet (continued)

A collision happens if two computers attempt to transmit at the same time.

– Each computer then backs off and waits a random amount of time before attempting to retransmit

– .It is normal to have collisions using this method, – but the delays caused by collisions and transmissions is small, and

does not effect speed of transmission on the network

CSMA/CD =Carrier Sense Multiple

Access /Collision Detection

Ethernet (continued)

Ethernet protocol allows for data to be transmitted over twisted pair, coaxial or fiber optic cable at a speed of 10 Mbps

(more on that later)

Fast Ethernet

To allow for faster transmission, the Ethernet protocol has developed a new standard that supports 100 Mbps

Fast Ethernet requires the use of more expensive equipment and network cards

Gigabit Ethernet

The Ethernet protocol has also developed a new standard that allows transmission of 1 Gbps (gigabit per second)

One gigabit per second = one

thousand megabits per

second

Local Talk

Local Talk is a network protocol that was developed by Apple for Macintosh computers

Local Talk uses the CSMA/CA – Carrier Sense Multiple Access with Collision Avoidance – It works in a similar way to CSMA/CD

It is a lot slower than Ethernet (only 230 Kbps)

Token Ring

Token ring protocol involves ‘token-passing’.

It is not as popular as Ethernet protocol

A single electronic ‘token’ moves around the ring from

one computer to the next. If a computer wishes to transit

and receives an empty token, it attaches data to the token which then proceeds around the ring until it comes to the computer the data is meant

for.

FDDI

Stands for Fiber Distributed Data Interface

Is used mainly to connect two or more LANs, often over large distances

Can operate over fiber optic cable at 100 Mbps

ATM- Asynchronous Transfer Mode

Transmit data at a speed of 155 Mbps and higher Works by transmitting all data in small packets of

fixed size (other protocols transfer variable size packets)

Like FDDI , is most often used to connect two or more LANs

Where does TCP/IP fit into all this?

TCP/IP is the protocol that is used for the transmission of information over the Internet

IP (Internet Protocol) - the main delivery system for information over the Internet

TCP (Transport Control Protocol) - used to break apart and rebuild information that travels over the Internet

In Chapter 3 We will look into this protocol in details.