Network Protocols

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 Application layer

  • Provides protocols that allow software to send and receive information and present meaningful data to users.
  • Used by end-user software.
  • Examples: Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Domain Name System (DNS), Simple Mail Transfer Protocol (SMTP), and Post Office Protocol (POP).


Hypertext Transfer Protocol (HTTP):

  • Data protocol used in World Wide Web (Communication between web clients and servers).
  • Communication between client computers and web servers is done by HTTP requests and receiving HTTP responses.
  • Hypertext Transfer protocol Secure (https) is a combination of Hypertext Transfer Protocol (HTTP) with the Secure Socket Layer (SSL)/ Transport Layer Security (TLS) (authentication and security protocol).
File Transfer Protocol (FTP):
  • Refers to a group of rules that govern how computers transfer files one system to another over the internet.
  • FTP uses three different modes: block, stream, and compressed.

  • Stream Mode: It is the default mode. In steam mode, the data is transferred from FTP to TCP in stream bytes.
    • Block Mode: In block mode, the data is transferred from FTP to TCP in the form of blocks, and each block followed by a 3-byte header.
    • Compressed Mode: This mode is used to transfer big files.  Compressed mode is used to decrease the size of the file into small and send it on the internet.



    Domain Name System (DNS):
    • It is a phonebook of the internet.
    • Translates domain names to IP addresses so browsers can load internet resources.
    • Eliminates the need for humans to memorize IP addresses.
    Simple Mail Transfer Protocol (SMTP):
    • It is a set of communication guidelines that allow software to transmit an electronic mail over the internet.
    • Program used for sending messages to other computer users based on e-mail address.
    • Provides a mail exchange between users on the same or different computers.
    • Main purpose: used to set up communications rules between servers.  
    Post Office Protocol (POP):
    • Protocol used to retrieve email from a mail server.
    • Two types of protocols: POP3 and IMAP.
    Telnet protocol:
    • Provides a standard method for terminal devices and terminal-oriented processes to interface.
    • Used for terminal emulation programs, terminal-to-terminal communication and inter-process communication and also for other protocols to establish a protocol control channel.
    Transport Layer:
    Second layer in TCP/IP model and fourth layer in the OSI model.




    Transport layer protocol:

    Transmission Control Protocol (TCP):
    • Provides acknowledgement of the received packets.
    • Relies on a three-way handshake (synchronization, synchronization acknowledgement and final acknowledgement).
    Three-way handshake:


    • Step 1: The client establishes a connection with a server. It sends a segment with SYN and informs the server about the client should start communication, and with what should be its sequence number.

    • Step 2: Server responds to the client request with SYN-ACK signal set. (ACK helps you to signify the response of segment that is received and SYN signifies what sequence number it should able to start with the segments.)

    • Step 3: The client acknowledges the response of the Server, and they both create a stable connection will begin the actual data transfer process.


    User Datagram Protocol (UDP):
    • Does not provide acknowledgement of the sent packets.
    • Used in video and voice streaming.
    Network layer Protocol:

    Address Resolution Protocol (ARP):
    • Used to associate an Ip address with the MAC address.
    Reverse Address Resolution Protocol (RARP):
    • Protocol which is used to obtain the IP address from a server.
    Internet Control Message Protocol (ICMP):
    • Used to send notifications of IP datagram problems back to the sender.
    • Handles both control and error messages.
    • Communicates the error message to the sender. ICMP messages causes the errors to be returned back to the user processes.
    • Internet Group Message Protocol (ICMP)

    It supports two types of communication:
    1. Unicasting: It is a communication between one sender and one receiver.
    2. Multicasting: Communication between one sender and large number of receivers.
    • used to support multicasting and identify the hosts in a LAN that are the members of the group.
    Internet Protocol (IP):
    • Protocol or a set of rules for routing and addressing packets of data.
    Network Access Layer: Lowest Layer of the TCP/IP protocol hierarchy.
    • The protocols in this layer provide the means for the system to deliver data to the other devices on a directly attached network.
    • Can encompass the functions of all two layers of the OSI reference Model.
    Ethernet:
    • Standard communication protocol used to create local area networks.
    • Transmits and receives data through cables.
    • facilitates network communication between two or more different types of network.
    Types:
    1. Fast ethernet: High speed internet and can transmit or receive data at about 100 Mbps.
    2. Gigabit Ethernet: Transfers data at a higher speed of about 1000 Mbps or 1Gbps
    3. 10-Gigabit Ethernet: More advanced and high speed network with a transfer rate of 10 Gigabit/second.
    4. Switch element: Requires a switch or hub.
    Types of IP Address:
    1. Public and private: Indicative of location of the network. Static and dynamic indicate permanency.
    2. Static IP address: It is manually created and does not change.
    3. Dynamic IP Address: Assigned by Dynamic Host Configuration Protocol (DHCP) server and is subject to change. 
    Subnetting: Technique for partitioning a single physical network into multiple smaller sub-networks.

    Default gateway or gateway: Connects local devices to other networks.

     
    Classful routing and classless routing:




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