1048 – Protocols Student Tasks

A protocol is an agreed set of about how to do something.  A network protocol is an agreed way of how to over a network.  A good communications protocol should include:

• How to set up and end a connection
• How to start and end a
• How to deal with corrupted data
• How to format the data being sent

There are a number of different protocols that are commonly used to communicate over a network.  One of them is the TCP/IP protocol.  The TCP part prepares messages for transmission and reassembles any received messages.  It does this by:

• Dividing the message into
• Adding a number
• Adding error correction information to the packet
• It examines each packet received for and fixes them if possible.
• It requests missing or packets to be resent
• It reassembles the message back into the correct sequence

The IP part of the protocol is responsible for providing the address and the source address to each packet.  It accepts data packets that have the correct address and ignore those which do not.

Another protocol is HTTP.  This is the protocol that is used on the World Wide Web / Internet.  It allows a to request individual files from a web server.  Once they are received they are rendered into a web page.  You might sometimes see web pages with HTTPS in their address.  The ‘s’ means that it is a web page.  On pages using this protocol, data is encrypted prior to being sent out of the browser to ensure that only the authorised site can read the data.

FTP is a protocol which is used to transfer (upload and download) files between a client and server on a computer network.

There are a number of protocols which are related to emails.   allows emails to be download and/or deleted from a mail server and viewed offline by an email client.  However, POP does have a number of disadvantages:

• It can only handle one
• Messages, once downloaded, cannot be viewed on the server by other devices
• It does not support complex searches of emails on the server

IMAP is similar in many ways to POP but it:

• Stores emails on the server so that they can be viewed at any time by multiple devices
• Allows complex searches to be carried out on emails
• It can handle more than one mailbox
• It can set flags to indicate if a message has been read or replied to

protocols are responsible for sending and receiving data along a network cable. The Ethernet protocol specifies:

• the performance expected of network cables, plugs and sockets
• the format of the data packets sent or received over the network
• how to deal with data collisions

When thinking about protocols we often use something called ‘the layer model’  This is a concept, not something which actually exists.  It has been developed to help people understand how the different network protocols interact with one another.  There are four layers in the model, the layer, the transport layer, the internet layer and the network access layer.  A protocol in a specific layer can only communicate with other protocols in the layers directly to it.  Some of the reasons that we use the four layer model are:

• The layer model is useful for manufacturers so that when they are developing new hardware they can ensure that it is compatible with existing protocols
• We can recognise roughly what a protocol does by knowing which layer it resides within.
• By dividing the system of protocols into layers we can focus on a particular area individually without worrying too much about the other layers.
• We can map how layers relate and interact with one another.