What is a Protocol

When two dissimilar computers systems communicate with each other they require a standard set of instructions for communicating with each other and these instructions are known as protocols. Protocols are the communications standards and the set of rules that source and destination computers must abide by and follow in order to communicate with each other.  They determine that how data will be transmitted between two computer computers. 

They also define the data packet size, authentication, signaling, data compression, error checking and retransmission of the packets. They also define that how the packet information will be organized while traveling over the network.

There are several types of the communication protocols and the most common network protocols are TCP/IP, POP, SMTP, SLIP, LDAP, FTP, SNMP, HTTP, PPP, PPTP, UDP, RIP, OSPF, RIP, DHCP, NNTP, ICMP and BOOTP.  Protocols are sometimes grouped into the lower level, upper level and the application protocols.  On the internet and the LAN/WAN communication networks, TCP/IP is the most common protocol. 

TCP/IP stands for Transmission Control Protocol and the Internet Protocol.  TCP/IP in fact is a suite of protocols that consists of more than 65,000 protocols. Each of the protocols in the TCP/IP stack performs different functionalities.  

In the Ethernet based networks and the on the internet, the data is divided into the small packets to make the transmission process speedy and reduce the errors.  These packets then reunite at the destination computer till all the packets are transmitted.  In the OSI (Open System Interconnectivity) model, each protocol works at different layer of the OSI layers model.

Layer 1 (Physical Layer)

Sonet, ISDN, SDH

Layer 2 (Data Link Layer)

Frame Relay, FDDI, Ethernet

Layer 3 (Network Layer)

RIP, OSPF, EGP, IPX, IPV6, ARP

Layer 4 (Transport Layer)

TCP, UDP, SPX

Layer 5 (Session Layer)

NFS, NCP, SMB

Layer 6 (Presentation Layer)

Layer 7 (Application Layer)

BOOTP, DHCP, DNS, HTTP, POP3, SSH, Telnet

Classifications of the Protocols

Protocols are classified into the following major categories.

TCP/IP

IP, TCP, UDP, SMTP, POP3, RIP, FTP, DHCP

Cellular

GPRS, GSM, WAP and CDMA

VOIP

SIP, RTP, Megaco, MGCP and H.323

General

Frame Relay, ATM, X.25, PPP,