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The word protocol is derived form the Greek word "protocollon" which means a leaf of paper glued to manuscript volume (HUH?!). In computing protocol means a set of rules, a communication language or set of standards between two or more computing devices. Protocols exist at several levels o the OSI (open system interconnectivity) layers model. On the internet, tehre is a suite of protocols known as TCP/IP protocols that are consisting of transmission control protocol, internet protocol, file transfer protocol, dynamic host configuration protocol, Border gateway protocol and a number of other protocols.

Protocol Properties

Different protocols perform different functions so it is difficult to generlise the properties of the protocol. There are some basic properties of most of the protocols.

• Detection of the physical (wired or wireless connection)
• Handshaking
• How to format a message
• How to send and receive a message
• Negotiation of the various connections
• Correction of the corrupted or improperly formatted messages.
• Termination of the session.

The widespread use of the communication protocols is a prerequisite to the internet. The term TCP/IP refers to the internet protocols suite and a pair o the TCP and IP protocols are the most important internet communication protocols. Most protocols in communication are layered together where the various tasks listed above are divided. Protocols in communication are layered together where the various tasks listed above are divided. Protols stacks refer to the combination of the different protocols. The OSI reference model is the conceptual model that is used to represent the protocol stacks. There are different network protocols that perform different functions. Following is the grouping and descriptions of the more commonly used protocols.

The Transport Layer

In computer networking, the Transport Layer provides end-to-end communication services for applications within a layered architecture of network components and protocols. The transport layer provides convenient services such as connection-oriented data stream support, reliability, flow control, and multiplexing. Transport layers are contained in both the TCP/IP model, which is the foundation of the Internet, and the Open Systems Interconnection (OSI) model of general networking. The definitions of the Transport Layer are slightly different in these two models. The Transport Layer is responsible for delivering data to the appropriate application process on the host computers. This involves statistical multiplexing of data from different application processes, i.e. forming data packets, and adding source and destination port numbers in the header of each Transport Layer data packet. Together with the source and destination IP address, the port numbers constitutes a network socket, i.e. an identification address o the process-to-process communication. In the OSI model, this function is supported by the Session Layer. Put simply the functions defined in the Transport Layer is to provide for the reliable transmission of data segments, as well as teh disassembly and assembly of the data before and after transmission.

DNS

Domain Name System (DNS) is a database system that translates a computer’s fully qualiied domain name into an IP address.

Networked computers use IP address to locate and connect to each other, but IP addresses can be difficult for people to remember. For example, on the web, it’s much easier to remember the domain name www.amazon.com than it is to remember its corresponding IP address (207.171.166.48). DNS allows you to connect to another networked computer or remote service by using its user-friendly domain name rather than its numberical IP address. Conversely, Reverse DNS (rDNS) translates an IP address into a domain name.

The DNS is a hierarchical naming system built on a distributed database of computers, services, or any resource connected to the Internet or a private network. It associates various infomration with domain names assigned to each of the participating entities. Most importantly, it translates domain names meaningful to humans into the numberical identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide. The Domain Name System (DNS) makes it possible to assign domain names to groups of Internet resources and users in a meaningful way, independent o each entity’s physical location. Because of this, World Wide Web (WWW) hyperlinks and Internet contact information can remain consistent and constant even if the current Internet routing arrangements change or the participant uses a mobile device.

In general, the DNS also stores other types of information, such as the list of mail servers that accept email or a given Internet domain. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component o the functionality of the Internet.

Wireless Communications

A wireless local area network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network.

Wireless LANs have become popular in the home due to ease of installation, and the increasing popularity of laptop computers. Public businesses such as coffee shops and malls have begun to offer wireless access to their customers; often for free. Large wireless network projects are being put up in many major cities: New Yorkk, for instance, has begun a pilot program to provide city workers in all five boroughs of the city with wireless internet access.

802.11/802.11x (WiFi)

This is a series of network standards developed by IEEE that speciies how two wireless devices communicate over the air with each other. Using the 802.11 standard, computers or devices that have the appropriate wireless capability communicate via radio waves with other computers or devices. There are many variations of the 802.11 standard including 802.11a (up to 54 Mbps), 802.11b (up to 11 Mbps), 802.11g (54 Mbps and higher) and 802.11n (up to 300 Mbps).

A designation of 802.11 a/b/g on a computer or device indicates it supports all three standards. The newest standard, 802.11n, uses multiple transmitters and receivers, known as MIMO (multiple-input multiple-output), to reach speeds from 2 to 10 times faster than 802.11g. The 802.11 standard oten is called the wireless Ethernet standard because it uses techniques similar to the Ethernet standard to specify how physically to configure a wireless network. Thus, 802.11 networks easily can be integrated with wired Ethernet networks. When an 802.11 network access the Internet, it works in conjunction with the TCP/IP network standard.

The term Wi-Fi (wireless fidelity) identifies any network based on the 802.11 series of standards. Wi-Fi Certified products are guaranteed to be able to communicate with each other. Most of today’s computers and many personal mobile devices, such as smart phones and handheld game consoles, are Wi-Fi enabled. One popular use o the Wi-Fi network standard is in hot spots that ofter mobile users the ability to connect to the Internet with their Wi-Fi enabled wireless computers and devices. Many homes and small businesses also use Wi-Fi to network computers and devices wirelessly. In open or outdoor areas free from interference, the computers or devices should be within 300 feet of each other. In closed areas, the wireless network range is about 100 feet. To obtain communications at the maximum distances, you may need to install extra hardware.

Some entire cities are set up as Wi-Fi mesh network, in which each mesh node routes its data to the next available note until the data reaches its destination – usually an Internet connection. A Wi-Fi mesh network is more flexible than a hot spot because each node in a mesh network does not have to be directly connected to the internet.

WAP

The Wireless Application Protocol (WAP) is a standard, specifically a protocol, that specifies how some mobile devices such as smart phones can display the content of Internet service such as the Web, e-mail, and chat rooms. For example, users can check weather, sports scores, and headline news from their WAP-enabled smart phone. To display a Web page on a smart phone, the phone should contain a microbrowser. WAP works in conjunction with the TCP/IP network standard. WAP uses a client/server network. The wireless device contains the client software which connects to the Internet access provider’s server. On WAP-enabled devices, data transfer rates range from 9.6 to 153 Kbps depending on the type of service. However, WAP is gradually becoming obsolete, as more advanced phones enter the market. Most new phones today are able to access websites using 3G/4G mobile communication and computer style browsers with standard HTTP. This has come about with the advancement of mobile hardware and graphics processing.

Bluetooth

Bluetooth is a network standard, specifically a protocol, that defines how two Bluetooth devices use short-range radio waves to transmitt data. The data transfers between devices at a rate of up to 3 Mbps. To communicate with each other, Bluetooth devices oten must be within about 10 meters but can be extended to 100 meters with additional equipment.

A Bluetooth device contains a small chip that allows it to communicate with other Bluetooth devices. Examples of Bluetooth-enabled devices can include desktop comptuers, notebook computers, handheld computers, smart phones, PDAs, headsets, keyboards, mouse devices, microphones, digital cameras, and printers. For computers and devices not Bluetooth-enabled, you can purchase a Bluetooth wireless port adapter that will convert an existing USB port or serial port into a Bluetooth port.

Wired Communications

Wired Communication refers to the transmission of data over a wire-based communication technology. Examples include telephone networks, cable television or internet access, and fiber-optic communication. Alternativelt, communication technologies that don’t rely on wires to transmit data are considered wireless. In computer networking, a wire protocol reers to a way of getting data from point to point: A wire protocol is needed if more than one application has to interoperate. In contrast to transport protocols at the transport level (like TCP or UDP) the term ‘wire protocol’ is used to describe a common way to represent inormation at the application level.

Ethernet

Ethernet is a network standard that speciies no central computer or device on the network (nodes) should control when data can be transmitted; that is, each node attempts to transmit data when it determines the network is available to reveive communications. If two computers on an Ethernet network attempt to send data at the same time, a collision will occur, and the comptuers must attempt to send their messages again.

Ethernet is based on a bus topology, but Ethernet networks can be wired in a star pattern. The Ethernet standard defines guidelines or the physical configuration of a network, e.g. cabling, network cards, and nodes. Today, Ethernet is the most popular network standard or LANs because it is relatively inexpensive and easy to install and maintain.

Ethernet networks often use cables to transmit data. At a 10 Mbps (million bits per second) data transfer rate, the orginal Ethernet standard is not very fast by todays standards. A more recent Ethernet standard, called Fast Ethernet, has data transfer rate of 100 Mbps, ten times faster than the original standard. Gigabit Ethernet provides an even higher speed of transmission, with transfer rates of 1 Gbps (1 billion bits per second). The 10-Gigabit Ethernet standard supports tranfter rates up to 10 Gbps.

802.2

IEEE 802.2 is the IEEE 802 standard for defining Logical Link Control (LLC), wich is the upper portion o the data link layer of the OSI Model. The LLC sublayer presents a uniform interface to the user of the data link service, usually the network layer. Beneath the LLC sublayer is the Media Access Control (MAC) sublayer, which is dependant on the particular medium being used (Ethernet, token ring, FDDI, 802.11, etc).

The IEEE standard adds this sublayer which adds the standard 8-bit DSAP (Destination Service Access Point) and SSAP (Source Service Access Point) labels to a given packet regardless of the network type. There is also an 8 or 16 bit control field for use in auxiliary functions such as flow control. Thre is room for 64 globally assigned

802.5 Token Ring

The token ring standard specifies that computers and devices on the network share or pass a special signal, called a token, in a unidirectional manner and in a preset order. A token is a special series of bits that function like a ticket. The device with the token can transmit data over the network. Only one token exists per network. This ensures taht only one computer transmits data at a time.

Token ring is based on a ring topology (although it can use a star topology). The token ring standard defines guidelines for the physical configuration of a network, e.g., cabling, network cards, and devices. Some token ring networks connect up to 72 devices. Others use a special type o wiring that allows up to 260 connections. The data transer rate on a token ring network can be 4 Mbps, 16 Mbps, 100 Mbps, or 1Gbps.

Internet Protocols (TCP/IP)

TCP/IP is short or Transmission Control Protocol/Internet Protocol, TCP/IP is network standard, specifically a protocol, that defines how messages (data) are routed from one end of a network to the other, ensuring the data arrives correctly. TCP/IP describes rules for dividing messages into small pieces, called packets; providing addresses for each packet; checking or and detecting errors; sequencing packets; and regulating the low of messages along the network. An Internet Protocol (IP) is a unique address or identifier o each computer or communication devices on the network and internet. Any participating computer networking device such as routers, comptuers, printers, internet fax machines and switches may have their own unique IP address. Personal information about someone can be found by the IP address. Every domain on the internet must have a unique or shared IP address.

TCP/IP has been adopted as a network standard for Internet Communications. Thus, all hosts on the Internet follow the rules defined in this standard. Internet communication also use other standards, such as the Ethernet standard, as data is routed to its destination. When a computer sends data over the Internet, the data is divided into packets. Each packet contains the data, as well as the recipient (destination), the origin (sender), and the sequence information used to reassemble the data at the destination. Each packet travels along the fastest individual available path to the recipient’s computer via communications devices called routers. This technique of breaking a message into individual packets, sending the packets along the best route available, and then reassembling the data is called packet switching.

Below are the more commonly used Internet Protocols.

HTTP

Hypertext Transfer Protocol is a method of transmitting the information on the web. HTTP basically publishes and retrieves the HTTP pages on the World Wide Web. HTTP is a language that is used to communicate between the browser and web server. The information that is transferred using HTTP can be plain text, audio, video, images, and hypertext. HTTP is a request/response protocol between the client and server. Many proxies, tunnels, and gateways can be existing between the browser and web server. The information that is transferred using HTTP can be plain text, audio, video, images, and hypertext. HTTP is a request/response protocol between the client and server. Many proxies, tunnels, and gateways can be existing between the web browser (client) and server (web server). An HTTP client initializes a request by establishing a TCP connection to a particular port on the remote host (typically 80 or 8080). An HTTP server listens to that port and receives a request message from the client. Upon receiving the request, server sends back 200 OK messages, its own message, an error message or other messages.

POP3

Post Office Protocol in computing e-mail clients such as (MS outlook, outlook express, thunderbird, etc) use POP3 to retreive emails rom the remote server over the TCP/IP connection. Nearly all the users o the Internet service providers use POP 3 in the email clients to retrieve the emails rom the email servers. Most email applications use POP protocol.

SMTP

Simple Mail Transfer Protocol is a protocol that is used to send the email messages between the servers. Most email systems and email clients use the SMTP protocol to send messages to one server to another. In configuring an email application, you ned to configure POP, SMTP and IMAP protocols in your email software. SMTP is a simple, text based protocol and one or more recipient of the message is specified and then the message is transferred. SMTP connection is easily tested by the Telnet utility. SMTP uses the by default TCP port number 25.

FTP

FTP or File Transfer Protocol is used to transfer (upload/download) data from one computer to another over the internet or through or computer network. FTP is a most commonly communication protocol for transferring the files over the internet. Typically, there are two comptuers are involved in the transferring the files a server and a client. The client computer that is running FTP client software such as CuteFTP and AceFTP etc initiates a connection with the remote computer (server). After successfully connected with the server, the client computer can perform a number of the operations like downloading the files, uploading, renaming and deleting the files, creating the new folders etc. Virtually operating system supports FTP protocols.

IMAP

The Internet Message Access Protocol known as IMAP is an application layer protocol that is used to access the emails on the remote servers. POP3 and IMAP are two most commonly used email retrieval protocols. Most of the email clients such as outlook express, thunderbird and MS outlooks support POP3 and IMAP. The email messages are generally stored on the email server and the users generally retreive these messages whether by the web browser or email clients. IMAP is generally used in the larger networks. IMAP allows users to access their messages instantly on their systems.