Introduction to TCP/IP protocols

Introduction to TCP/IP protocols

TCP/IP is made up of two different protocols, TCP, for Transmission Control Protocol, and IP, for Internet Protocol. TCP handles packet flow between systems and IP handles the routing of packets, TCP/IP is the communication protocol for the Internet. TCP/IP uses 4-byte (32-bit) addresses in the current implementations (IPv4), also called IP-numbers (Internet-Protocol numbers), to address hosts.


TCP/IP allows any two machines to communicate directly. TCP/IP developed under the Sponsorship from DARPA (Defense Advanced Research Projects Agency) in the early 1970s.

What is TCP/IP?


TCP/IP defines how electronic devices (like computers) should be connected to the Internet, and how data should be transmitted between them. TCP/IP is not limited just to these two protocols, however. Frequently, the term TCP/IP is used to refer to a group of protocols related to the TCP and IP protocols such as the User Datagram Protocol (UDP), File Transfer Protocol (FTP), Terminal Emulation Protocol (TELNET), and so on.


Transmission control Protocol (TCP):


TCP is a connection-oriented protocol; TCP incurs additional overhead to gain functions. Additional functions specified by TCP are the same order delivery, reliable delivery, and flow control. Each TCP segment has 20 bytes of overhead in the header encapsulating the Application layer data, whereas each UDP segment only has 8 bytes of overhead. TCP is the means for creating the packets, putting them back together in the correct order at the end, and checking to make sure that no packets got lost in transmission. If necessary, TCP will request that a packet be resent. Tcp works under Transport layer.


For example:


For example, when a user running a Web browser requests a page, the browser uses HTTP to send a request via TCP to the Web server. When the Web server receives the request, it uses HTTP to send the requested Web page back to the browser, again via TCP. Other Application layer protocols that use TCP include Telnet (for terminal emulation), FTP (for file exchange), and SMTP (for e-mail).


User Datagram Protocol (UDP):


UDP is a simple, connectionless protocol; it has the advantage of providing for low overhead data delivery. The pieces of communication in UDP are called datagram’s. These datagram’s are sent as “best effort” by this Transport layer protocol.


For example:


When an application needs to access a domain name such as, DNS sends a UDP packet to a DNS server to look up the domain. When the server finds the domain, it returns the domain’s IP address in another UDP packet.


* Thin layer on top of IP


* Also source and destination ports


* Ports are used to associate a packet with a specific application at each end


* Still unreliable


* Duplication, loss, out-of-orderings possible.


Internet Protocol (IP):


IP, which stands for Internet Protocol, is a Network layer protocol that is responsible for delivering packets to network devices. Internet Protocol (IP) is the method used to route information to the proper address. Every computer on the Internet has to have it own unique address known as the IP address.


Note: IP does not make physical connections between computers but relies on TCP for this function. IP is also used in conjunction with other protocols that create connections.


Address resolution Protocol (Arp):


Address Resolution Protocol (ARP) is a protocol for mapping an Internet Protocol address (IP address) to a physical machine address that is recognized in the local network, ARP is a very important part of IP networking, this is protocol used to connect network layer to data link later.


Internet Control Message Protocol (ICMP):


ICMP is a complementary protocol to IP. ICMP comes under the Network Layer of the OSI Model. ICMP is designed for sending control and test messages across IP networks. The two most important ICMP messages are Echo Request (8) and Echo Reply (0). Echo Request and Echo Reply, when “ping” the network its ICMP generate the packets.


Packet internet groper (PING):


Ping command used for check the network connectivity between hosts.


File transfer protocol (FTP):


FTP is a standers internet protocol for transferring files between computers on the internet. We commonly use FTP to transfer files from local system to remote system. FTP port no 20(data connection), 21(control connection)


Hypertext Transfer protocol (HTTP):


Http is a protocol which is used to publish text, graphic images, sound, video, and other multimedia files through World Wide Web. Using a web browser user can view the resource driven by HTTP. It’s an application protocol that runs on top the TCP/IP. HTTP port no 80.


Simple Mail Transfer Protocol (SMTP):


SMTP is used to send and receive Email across the network. SMTP port no 25.


Domain name system (DNS):


DNS server resolves IP address to host name and Host name to IP address. DNS Port no 53.


Dynamic host control protocol (DHCP):


DHCP dynamically assign IP address to the client system and manages IP lease. Port no 67.