Introduction to Networking

TCP/IP Protocols

The TCP/IP model is based on standard protocols that were developed by the Department of Defense (DoD) in the 1960s. It contains 4 layers, unlike the 7 layers in the OSI model. The four layers are:

  • Process/Application Layer
  • Host-to-Host/Transport Layer
  • Internet Layer
  • Network Access/Link Layer

  • TCP/ IP is the protocol suite used for communication between hosts in most local computers and the internet.
  • TCP/IP is supported and included in many OS, i.e., Windows 7, XP, Vista, MAC OS, LINUX, AND UNIX.
  • The TCP/IP protocol suite was developed before the OSI model.

A list of some protocols is explained below,

1. TCP (Transfer Control Protocol)

The transport layer uses TCP or UDP protocol for data transmission.

This protocol is connection oriented and provides the reliability to data transfer. The sender cannot send the data until the connection is established between the sender and receiver.TCP divides data into small packets called segments.

Features of TCP

  • Connection opening
  • Flow control
  • Sequencing
  • Acknowledgment
  • Error deduction (by checksum method)
  • Connection closing

2. UDP (User Datagram Protocol)

This protocol is not connection-oriented and does not provide higher reliability to data transfer. The sender can send the data without establishing a connection between the sender and receiver. To transfer data UDP provides the following functionality on data.

  • Source port address
  • Destination port address
  • Total length of data in bytes
  • Checksum (16-bit error detection)

It provides only the basic functionality of end-to-end delivery of data. It does not provide the sequence number to segments that way it cannot re-order the packets at receiving end.

3. DHCP (Dynamic Host Configuration Protocol)

  •  It is a protocol used to dynamically assign an IP address to any node or device on a network.
  • The servers that assign and manage the dynamic IP addresses, called DHCP servers.
  • The workstations that are dynamically assigned IP addresses by DHCP servers are called DHCP clients.
  • DHCP software’s resides on clients and servers to manage the dynamic assignment of IP addresses.
  • Range of IP addresses to be assigned to the clients is specified when DHCP servers are configured.
  • DHCP servers assigned IP addresses to DHCP clients from assignable list.
  • DHCP servers can assign IP addresses in three different ways.

Automatic Allocation: The server always attempts to assign the same IP address to a given host or node, i.e., mail server, because other hosts may have saved its internal address.

Dynamic Allocation: Each time the clients log onto the network, Dynamically, an IP address is assigned to it from the available list of IP addresses.

Manual Allocation: A network administrator assigns address to a particular host or node.

4. DNS (Domain Name System)

This protocol is used in the presentation layer. The IP address is difficult to remember for user. The domain names are alphabetic and are easier to remember.  Domain name server resolves this issue.

  • We just use the name of the website, i.e., Facebook, YouTube etc. and DNS finds out their relevant IP address.
  • For example, the domain name www.example .com may translate to
  • Domain name server must updated periodically to include new domain names.

5. SMTP (Simple Mail Transfer protocol)

SMPT provides the facilities for mail exchange between users on the same or different computers. It supports the following.

  • For Sending a message to one or more computers
  • Sending messages that include text, voice, video, or graphics
  • Sending messages to users on networks outside the internet.

6. Firewalls

  • A firewall is a set of components used to restrict access to data and information on the network.
  • It may consist of hardware and software.
  • Firewalls are used to restrict unauthorized users from accessing the resources of an organization.
  • Packets are blocked if they are sent from unauthorized users.
  • The major kinds of firewalls include include packet filtering and proxy firewalls.

Some other protocols are given below.

  • HTTP (hypertext transfer protocol): All webpages from the internet are accessed through http protocol.
  • FTP: to send files on the remote server.