Internet protocol suite (TCP/IP)

TCP/IP (transmission control protocol/Internet protocol) is the suite of communications protocols that is used to connect hosts on the Internet and on most other computer networks as well. It is also referred to as the TCP/IP protocol suite and the Internet protocol suite.A protocol is a mutually agreed-upon format for doing something. With regard to computers, it most commonly refers a set of rules (i.e., a standard) that enables computers to connect and transmit data to one another; this is also called a communications protocol.TCP/IP was originally designed for the UNIX operating system, and it is built into all of its descendants (i.e., Unix-like operating systems), including Linux and Mac OS X. Network operating systems that have their own networking protocols, such as Novell's Netware, also support TCP/IP.TCP/IP is designed to make a network robust and automatically recover from the failure of any device on the network. Moreover, it allows the construction of very large networks that require little central management.TCP/IP takes its name from its two main protocols: transmission control protocol (TCP) and Internet protocol (IP). TCP operates at the transport layer, i.e., the middle layer in the seven layer OSI (open systems interconnection) reference model. This layer is responsible for maintaining reliable end-to-end communications across the network. IP, in contrast, is a network layer protocol, which is the layer just below the transport layer.Whereas the 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.The great success of TCP/IP is the result of the advantages that it offers over other network protocols and protocol suites, including the following:

(1) It is a freely available protocol and not a secret protocol that is owned by a single company. This makes it possible for anyone with sufficient technical knowledge to improve it.(2) It is compatible with virtually all modern operating systems, and thus it enables almost any system to communicate with any other system.(3) It is also compatible with virtually all types of computer hardware and network configurations.(4) It is a routable protocol, which means that it can determine the most efficient path for every packet as it moves through the network. This makes TCP/IP highly scalable and thus the size of the network virtually unlimited (e.g., the Internet).(5) It provides reliable data delivery. Reliable means that it can guarantee that the data is delivered to its intended destination (e.g., through the use of error checking and the retransmission of corrupted or missing packets).

(6) The use of a single (and relatively simple) addressing scheme, referred to as IP addressing, allows administrators to transfer their knowledge of TCP/IP to any TCP/IP network without the need to learn a new addressing scheme.

The roots of TCP/IP can be traced back to a 1974 article by two Internet pioneers, Vint Cerf and Bob Kahn, titled A Protocol for Packet Network Interconnection, which described TCP. At that time, a communications language called network control protocol (NCP) was used by hosts on the ARPANET (Advanced Research Projects Agency Network), the precursor to the Internet. NCP had numerous limitations, including lack of sufficient robustness, for the still small, but rapidly expanding, supernetwork.

Open Systems Interconnection (OSI)

OSI (Open Systems Interconnection) is a standard description or "reference model" for how messages should be transmitted between any two points in a telecommunication network. Its purpose is to guide product implementors so that their products will consistently work with other products. The reference model defines seven layers of functions that take place at each end of a communication. Although OSI is not always strictly adhered to in terms of keeping related functions together in a well-defined layer, many if not most products involved in telecommunication make an attempt to describe themselves in relation to the OSI model. It is also valuable as a single reference view of communication that furnishes everyone a common ground for education and discussion.Developed by representatives of major computer and telecommunication companies beginning in 1983, OSI was originally intended to be a detailed specification of interfaces. Instead, the committee decided to establish a common reference model for which others could develop detailed interfaces, that in turn could become standards. OSI was officially adopted as an international standard by the International Organization of Standards (ISO). Currently, it is Recommendation X.200 of the ITU-TS.The main idea in OSI is that the process of communication between two end points in a telecommunication network can be divided into layers, with each layer adding its own set of special, related functions. Each communicating user or program is at a computer equipped with these seven layers of function. So, in a given message between users, there will be a flow of data through each layer at one end down through the layers in that computer and, at the other end, when the message arrives, another flow of data up through the layers in the receiving computer and ultimately to the end user or program. The actual programming and hardware that furnishes these seven layers of function is usually a combination of the computer operating system, applications (such as your Web browser), TCP/IP or alternative transport and network protocols, and the software and hardware that enable you to put a signal on one of the lines attached to your computer.

OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lower three layers (up to the network layer) are used when any message passes through the host computer. Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host. The seven layers are:Layer 7: The application layer...This is the layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. (This layer is not the application itself, although some applications may perform application layer functions.)Layer 6: The presentation layer...This is a layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text). Sometimes called the syntax layer.Layer 5: The session layer...This layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination.Layer 4: The transport layer...This layer manages the end-to-end control (for example, determining whether all packets have arrived) and error-checking. It ensures complete data transfer.Layer 3: The network layer...This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding.Layer 2: The data-link layer...This layer provides synchronization for the physical level and does bit-stuffing for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management.Layer 1: The physical layer...This layer conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier.

File Transfer Protocol(FTP)

File Transfer Protocol (FTP) is a standard Internet protocol for transmitting files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to download programs and other files to your computer from other servers.As a user, you can use FTP with a simple command line interface (for example, from the Windows MS-DOS Prompt window) or with a commercial program that offers a graphical user interface. Your Web browser can also make FTP requests to download programs you select from a Web page. Using FTP, you can also update (delete, rename, move, and copy) files at a server. You need to logon to an FTP server. However, publicly available files are easily accessed using anonymous FTP.Basic FTP support is usually provided as part of a suite of programs that come with TCP/IP. However, any FTP client program with a graphical user interface usually must be downloaded from the company that makes it. You can use FTP to exchange files between computer accounts, transfer files between an account and a desktop computer, or access online software archives. Keep in mind, however, that many FTP sites are heavily used and require several attempts before connecting.

Universal Plug and Play(UPnP)

Universal Plug and Play (UPnP) is a standard that uses Internet and Web protocol s to enable devices such as PCs, peripherals, intelligent appliances, and wireless devices to be plugged into a network and automatically know about each other. With UPnP, when a user plugs a device into the network, the device will configure itself, acquire a TCP/IP address, and use a discovery protocol based on the Internet's Hypertext Transfer Protocol ( HTTP ) to announce its presence on the network to other devices. For instance, if you had a camera and a printer connected to the network and needed to print out a photograph, you could press a button on the camera and have the camera send a "discover" request asking if there were any printers on the network. The printer would identify itself and send its location in the form of a universal resource locator ( URL ).The camera and printer would use Extensible Markup Language ( XML ) to establish a common language, or "protocol negotiation", to talk to each other and determine capabilities. Once a common language was established, the camera would control the printer and print the photograph you selected. Microsoft, one of 29 companies sponsoring UPnP, hopes that UPnP will make it as easy to plug a device or appliance into a home or small business data network as it is to plug a lamp into an electrical outlet.Universal Plug and Play is an open industry standard that Microsoft, a leading promoter of the standard, describes as "seamless proximity networking" that provides "standardization on the wire rather than in the devices," using existing Internet standards.

Internet Small Computer System Interface(iSCSI)

Internet small computer systems interface (iSCSI) is a networking standard for linking data storage components over a network, usually in storage area networks (SANs).SCSI is an established medium of fast communication between components. It communicates with physically separated components over an Internet Protocol network. ISCI uses Transmission Control Protocol (TCP) ports 80 and 3260.In a storage area network (SAN), disk storage is usually consolidated into a single box containing the controller and a large number of disks. A portion of this mega disk, called a logical unit number (LUN), is then presented to a server for storage. An example is a Windows server on a corporate local area network (LAN).A mega disk appears to the Windows operating system as a locally attached physical disk. It is necessary to tell the Windows server that the LUN is a local disk and not merely a mapped network drive. Many applications (such as those by Oracle) refuse to work with mapped drives. Therefore, it is necessary to find a way to allow the Windows OS to recognize the LUN as a local disk and to allow the transfer of data on the LUN back to the mother megadisk. All this is accomplished using iSCSI.A small program called the iSCSI initiator sits on the Windows server and is activated when the OS boots up. The initiator enables Windows to see the LUN as a local disk. The initiator is also responsible for sending specially formatted SCSI commands over the IP-based network. These commands are known as command descriptor blocks (CDBs).Although the execution will be different, the concept is exactly the same for other operating systems such as Unix or Linux, or for environments other than SANs.Network File System (protocol)

The Network File System (NFS) is a client/server application that lets a computer user view and optionally store and update file on a remote computer as though they were on the user's own computer. The user's system needs to have an NFS client and the other computer needs the NFS server. Both of them require that you also have TCP/IP installed since the NFS server and client use TCP/IP as the program that sends the files and updates back and forth. (However, the User Datagram Protocol, UDP, which comes with TCP/IP, is used instead of TCP with earlier versions of NFS.)NFS was developed by Sun Microsystems and has been designated a file server standard. Its protocol uses the Remote Procedure Call (RPC) method of communication between computers. You can install NFS on Windows 95 and some other operating systems using products like Sun's Solstice Network Client.Using NFS, the user or a system administrator can mount all or a portion of a file system (which is a portion of the hierarchical tree in any file directory and subdirectory, including the one you find on your PC or Mac). The portion of your file system that is mounted (designated as accessible) can be accessed with whatever privileges go with your access to each file (read-only or read-write).NFS has been extended to the Internet with WebNFS, a product and proposed standard that is now part of Netscape's Communicator browser. WebNFS offers what Sun believes is a faster way to access Web pages and other Internet files.

Remote Sync(RSYNC)

Rsync (Remote Sync) is a most commonly used command for copying and synchronizing files and directories remotely as well as locally in Linux/Unix systems. With the help of rsync command you can copy and synchronize your data remotely and locally across directories, across disks and networks, perform data backups and mirroring between two Linux machines.

Some advantages and features of Rsync command

It efficiently copies and sync files to or from a remote system. Supports copying links, devices, owners, groups and permissions. Its faster than scp (Secure Copy) because rsync uses remote-update protocol which allows to transfer just the differences between two sets of files. First time, it copies the whole content of a file or a directory from source to destination but from next time, it copies only the changed blocks and bytes to the destination. Rsync consumes less bandwidth as it uses compression and decompression method while sending and receiving data both ends.

Unison Best Usenet BrowserUsenet. its filled with interesting things. but it can be overwhelming.unison 2 makes it easy to read, look, listen, and download.Find Groups Use the "Directory" to search for relevant groups.Or, use "All Groups" to find your favorites Add groups to your sidebar for quick access Set group options like auto-loading and offline reading

Read Messages Use the Thread View to read all messages at once Thread lines make it easier to see who replied to what View and post messages in HTML or Plain Text

Work with Files Files are magically grouped together for downloading See images, music, files, and messages in one view "Smart Downloading" skips unneeded recovery sets

Much More Use the Search Browser to find files and NZBs Built-in UnPAR/UnRAR/Join, no external tools needed Set up Rules to manage your messages Upload binary files in one automated click Preview music by streaming it directly off the serverAppleTalk

AppleTalk is a proprietary suite of networking protocols developed by Apple Inc. for their Macintosh computers. AppleTalk included a number of features that allowed local area networks to be connected with no prior setup or the need for a centralized router or server of any sort. Connecting together AppleTalk equipped systems would automatically assign addresses, update the distributed namespace, and configure any required inter-networking routing. It was a plug-n-play system.AppleTalk was released in 1985, and was the primary protocol used by Apple devices through the 1980s and 90s. Versions were also released for the IBM PC and compatibles, and the Apple IIGS. AppleTalk support was also available in most networked printers (especially laser printers), some file servers and a number of routers.The rise of TCP/IP during the 1990s led to a re-implementation of most of these types of support on that protocol, and AppleTalk became unsupported as of the release of Mac OS X v10.6 in 2009. Many of AppleTalk's more advanced auto-configuration features have since been introduced in Bonjour, while Universal Plug and Play serves similar needs.

BackgroundIn the early 1980s, as Apple Computer, Inc. was preparing to introduce the Macintosh computer,Apple engineers knew that networks would become a critical need. They wanted to ensure that a Macintosh-based network was a seamless extension of the revolutionary Macintosh user interface.With these two goals in mind, Apple decided to build a network interface into every Macintosh andto integrate that interface into the desktop environment. Apples new network architecture was calledAppleTalk.Although AppleTalk is a proprietary network, Apple has published AppleTalk specifications in anattempt to encourage third-party development. Today, many companies are successfully marketingAppleTalk-based products, including Novell, Inc. and Microsoft Corporation.The original implementation of AppleTalk, which was designed for local workgroups, is nowcommonly referred to as AppleTalk Phase 1. With the installation of over 1.5 million Macintoshcomputers in the first 5 years of the products life, however, Apple found that some large corporationswere exceeding the built-in limits of AppleTalk Phase 1, so they enhanced the protocol. Theenhanced protocol, known as AppleTalk Phase 2, improved the routing capabilities of AppleTalk andallowed AppleTalk to run successfully in larger networks.

Technology BasicsAppleTalk was designed as a client-server distributed network system. In other words, users share network resources (such as files and printers) with other users. Computers supplying these networkresources are called servers; computers using a servers network resources are called clients.Interaction with servers is essentially transparent to the user because the computer itself determinesthe location of the requested material and accesses it without further information from the user. In addition to their ease of use, distributed systems also enjoy an economic advantage over peer-to-peer systems because important materials can be located in a few, rather than many, locations.In Figure 16-1, AppleTalk protocols are shown adjacent to the OSI layers to which they map.

Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX)Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) is a set of network protocols that provide packet switching and sequencing for small and large networks. IPX works at layer three of the Open Systems Interconnection (OSI) model and SPX works at layer 4.IPX/SPX was designed as a Transmission Control Protocol/Internet Protocol (TCP/IP) alternative. These protocols share similarities but have slight differences.IPX/SPX is compatible with local area networks (LAN) or private networks and different communication protocol functions. For example, the Routing Information Protocol (RIP) function is used to route server information, which provides optimal data routing.SPX is connection-oriented and used for routing information and connection-related functions. Like IP, IPX is connectionless and contains end-user data, such as IP addresses.Network Basic Input/Output System(NetBIOS)

NetBIOS (Network Basic Input/Output System) is a program that allows applications on different computers to communicate within a local area network (LAN). It was created by IBM for its early PC Network, was adopted by Microsoft, and has since become a de facto industry standard. NetBIOS is used in Ethernet and Token Ring networks and, included as part of NetBIOS Extended User Interface (NetBEUI), in recent Microsoft Windows operating systems. It does not in itself support a routing mechanism so applications communicating on a wide area network (WAN) must use another "transport mechanism" (such as Transmission Control Protocol) rather than or in addition to NetBIOS.NetBIOS frees the application from having to understand the details of the network, including error recovery (in session mode). A NetBIOS request is provided in the form of a Network Control Block (NCB) which, among other things, specifies a message location and the name of a destination.NetBIOS provides the session and transport services described in the Open Systems Interconnection (OSI) model. However, it does not provide a standard frame or data format for transmission. A standard frame format is provided by NetBUI.NetBIOS provides two communication modes: session or datagram. Session mode lets two computers establish a connection for a "conversation," allows larger messages to be handled, and provides error detection and recovery. Datagram mode is "connectionless" (each message is sent independently), messages must be smaller, and the application is responsible for error detection and recovery. Datagram mode also supports the broadcast of a message to every computer on the LAN.