Part III : THEORY GUIDE Network

Protocol

Sometimes referred to as an Access Method. A set of rules and conventions for sending Information over a Network. These rules administrate the content, format, timing, sequencing, and error control of messages exchanged among Network Devices. Each Protocol has its own method of how Data is formatted when sent and what to do with it once receives, how that Data is compressed and how to check for errors in Data.

Protocol is the communication language or rule which establishes the Network within the Hosts (Nodes) on the Network. In Information Technology, a Protocol is the special set of rules that end points in a telecommunication connection use when they communicate. Protocols exist at several levels in a telecommunication connection. For example, there are Protocols for the data interchange at the hardware device level and Protocols for data interchange at the application program level. In the standard model known as OSI (Open Systems Interconnection), there are one or more Protocols at each layer in the telecommunication exchange that both ends of the exchange must recognize and observe. Protocols are often described in an industry or international standard. There are numerous types of Protocols some of them are listing below, which are mostly used:

• TCP/IP (Transmission Control Protocol/Internet Protocol): TCP/IP was originally designed for the UNIX Operating System, and it is built into all of its family (i.e., Unix-like Operating Systems), including Linux and Mac OS X. Now a day it is compatible with most of all modern Operating Systems, and thus it enables almost any system to communicate with any other system as well as all types of Network hardware and Network configurations. 

TCP/IP is the suite (set, group) of communications Protocols that is used to connect Hosts on the Internet and on most other Network Computers as well. It is also referred to as the TCP/IP Protocol Suite and the Internet Protocol Suite. 

TCP/IP takes its name from its two main Protocols: TCP & IP. TCP operates at the Transport Layer. This layer is responsible for maintaining reliable end-to-end communications across the Network. IP is a Network Layer Protocol, which is the layer just below the transport layer. 

IP Protocol deals only with Packets (i.e., the most fundamental unit of TCP/IP data transmission), TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent. 

• FTP (File Transfer Protocol): The Protocol commonly used to transfer files through a Network (Including the Internet). Basically, it is a way to copy files from one Network to another, commonly used in P2P (Peer-to-Peer) File Sharing.
• POP3 (Post Office Protocol3): POP3 (Post Office Protocol 3) is the standard Protocol for receiving E-mail. POP3 is a Client/Server Protocol in which E-mail is received and held by Internet Server. This standard Protocol is built into most popular E-mail products, such as Eudora and Outlook Express. It is also built into the Microsoft, Netscape, Yahoo & Google’s Internet Explorer Browsers. Windows Server includes the POP3 service for providing clients with Mailboxes, and for handling incoming E-mail. 

POP3 is designed to delete mail on the Server as soon as the user has downloaded it. However, some implementations allow users or an administrator to specify that mail be saved for some period of time. POP can be thought of as a ‘Store-&-Forward’ service. 

• IMAP (Internet Message Access Protocol): IMAP was developed at Stanford University in 1986. IMAP is a standard Protocol for accessing E-mail from local Server. IMAP (The latest version is IMAP Version 4) is a Client/Server Protocol in which E-mail is received and held by Internet Server. E-mail Client can view just the heading and the sender of the letter and then decide whether to download the mail. Multiple folders or mailboxes on the Server can be create and manipulate, delete messages, or search for certain parts or an entire node. IMAP also uses SMTP for retrieving E-Mail messages. It is similar to POP3 Protocol however, supports additional features not found in POP3. 

 IMAP can be thought of as a RFS (Remote File Server). POP3 can be thought of as a ‘Store-&- Forward’ service. 

• SMTP (Simple Mail Transmission Protocol): SMTP Protocol used in sending E-mail. It is usually used with one of two other Protocols, POP3 or IMAP that let the user save messages in a Server mailbox and download them periodically from the Server. In other words, users typically use a program that uses SMTP for sending E-mail and either POP3 or IMAP for receiving E-mail.
• WAP (Wireless Access Protocol): WAP is a specification for a set of communication Protocols to standardize the way that wireless devices, such as cellular telephones and radio transceivers, can be used for Internet access, including E-mail, the WWW (World Wide Web), newsgroups, and instant messaging. While Internet access has been possible in the past, different manufacturers have used different technologies.The WAP was conceived (ideas) by four companies: Ericsson, Motorola, Nokia, and Unwired Planet (now Phone.com). The Wireless Markup Language (WML) is used to create pages that can be delivered using WAP. 
• DHCP (Dynamic Host Configuration Protocol): DHCP is a communication Protocol that lets Network Administrators centrally manage and automate the assignment of Internet Protocol addresses in an organization’s Network. 

The DHCP Server assigns IP addresses from a predetermined (set) IP address range(s), called a Scope. A DHCP Scope can be defined as a set of IP addresses which the DHCP Server can allocate or assign to DHCP Clients. A Scope contains specific configuration information for Clients that have IP addresses which are within the particular Scope. Scope information for each DHCP Server is specific to that particular DHCP Server only, and is not shared between DHCP Servers. Scopes for DHCP Servers are configured by Administrators.