Protocols

What is a Protocol?

• A protocol is an agreed format which allows devices to communicate. It is effectively a set of rules.
• These rules can include the following:
• Handshakes, The point at which 2 devices establish their readiness to communicate.
• How the sending device will indicate when it's finished sending.
• How a recieving device will indicate when it's recieved the data.
• Types of error checking to be used.
• Agreement on the data compression method that will be used.

Types of Protocol

• FTP- File Transfer Protocol
• HTTP - Hyper Text Transfer Protocol
• IMAP - Internet Message Access Protocol
• SMTP - Simple Mail Transport Protocol
• The standard network protocol that is used when data is transported between hosts.
• The underlying protocol used by the world wide web
• The standard protocol used by email clients to retrieve email messages from a mail server.
• The TCP/IP protocol used in sending and recieving email. As it is limited in its ability to queue messages at the recieving end, it is usually used in unison with another protocol.

Packets

• Anything sent between computers is divided up into packets.
• These packets will split the data being sent up between them and they will all go by various different routes to the recipient.
• The packets are always reasonably small in size and are rather numerous.
• The packets are all put back together again when they get to the recipient.
• So the client knows when all the packets have arrived the last one is called a frame.

Data link layer

• This is sometimes called the internet interface layer, it is where most LAN and wireless LAN tech are defined.
• The layer usually consists of device drives within the operating system and the NIC attached to the system.
• The Data Link Layer handles the movement of data in and out across a physical link within the network.
• The most commonly used protocols for the Data Link Layer are:
• ARP(Address Resolution Protocol)
• PPP(Point to Point Protocol)
• The Data Link Layer encodes bits into packets prior to their transmission and decodes them back into bits when they arrive at their destination.