Protocols

Protocols

1. Application

   • HTTP (S)
     • Web pages are sent and received using the http protocol.
       • There is a variation of it called 'https' (extra s on the end), meaning 'http secure'.
         • HTTP, or "HyperText Transfer Protocol", is the protocol underlying the World Wide Web.
           • The http protocol allows a browser to request these individual files from a web server in an orderly way. Once received, they are rendered into a web page such as the one you are reading at the moment.
   • FTP
     • FTP, or 'File Transfer Protocol' is a standard network protocol used to transfer (i.e. upload and download) files between a client and server on a computer network.
   • IMAP
     • Internet Message Access Protocol (IMAP) is similar in many ways to POP but it also offers more complex commands to manage emails on the server itself.
     • Unlike POP the email remains on the server even after being downloaded to the device. This means that you can use multiple devices and perhaps view your emails using your laptop and then access them from elsewhere on your smartphone and they will still look exactly the same.
   • POP
     • Post Office Protocol (POP) allows emails to be downloaded and /or deleted from a mail server and viewed offline by an email client.
   • SMTP
     • Simple Mail Transport Protocol (SMTP) is used by the mail server itself to send and receive emails from all other mail servers across the internet.
   • the protocols in this layer provude access to email, files and websites across an ip network

2. Link

   • Bluetooth
     • This is a wireless protocol that was developed to allow devices that are very close to one another to exchange data. It works up to 10 metres, but most often the devices are within a metre of each other.
       • Some parts of bluetooth reside in the Data Link layer (its sets up the radio link) and other parts reside in the application layer (the 'discovery' part that scans for nearby devices).
   • Ethernet
     • Ethernet is a family of protocols responsible for sending and receiving data along a network cable. Ethernet works over a range of data speeds hence the reason for a family of protocols rather than just one.
       • Ethernet is the most common protocol used for putting together a local area network (LAN).
   • The protocols in this layer are responsible for actually trasnmitting and recieving data through cables or wirelessly

3. Internet

   • IP
     • When transmitting messages, this protocol is responsible for providing the destination address and to recognise incoming data packets.
       • Add the destination address to each data packet
         • Add it own address to indicate where it came from
           • Accept data packets that have its own address attached
             • Ignore all data packets that do not contain its own address
   • The ip part of the tcp/ip protocol resides in this layer. it is responsible for managing the address of source and destination locations

4. Transport

   • TCP
     • Dividing the message into packets
       • Adding a sequence number to each packet so the message can be re-assembled
         • Adding extra error-correction information, so errors can be spotted and fixed
           • Examining each packet for errors by using the extra information that was added to it
             • Fixing any errors (if possible) or requesting that the packet be re-sent
               • Spotting missing packets and requesting them to be re-sent
                 • If all packets are present, using the sequence number of each packet to re-assemble the message
   • The tcp part of the tcp/ip protocol resides in this layer. it is responsible for dividing messages into packets, adding sequence numbers and error correction infomation. it also checks and deals with errors of received data packets