A BIT ABOUT NETWORKING

switch (network switch)

(reference:about.com)

Definition: A network switch is a small hardware device that joins multiple computers together within one local area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI model.

Network switches appear nearly identical to network hubs, but a switch generally contains more "intelligence" (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of that packet, and forwarding it appropriately. By delivering each message only to the connected device it was intended for, a network switch conserves network bandwidth and offers generally better performance than a hub.

As with hubs, Ethernet implementations of network switches are the most common. Mainstream Ethernet network switches support either 10 Mbps, 100 Mbps, or 10/100 Mbps Ethernet standards.

Different models of network switches support differing numbers of connected devices. Most consumer-grade network switches provide either four or eight connections for Ethernet devices. Switches can be connected to each other. Such "daisy chaining" allows progressively larger number of devices to join the same LAN.

Ethernet hub

Definition: In computer networking, a hub is a small, simple, inexpensive device that joins multiple computers together. Many network hubs available today support the Ethernet standard. Other types including USB hubs also exist, but Ethernet is the type traditionally used in home networking.

Working With Ethernet Hubs

To network a group of computers using an Ethernet hub, first connect an Ethernet cable into the unit, then connect the other end of the cable to each computer's network interface card (NIC). All Ethernet hubs accept the RJ-45 connectors of standard Ethernet cables.

To expand a network to accommodate more devices, Ethernet hubs can also be connected to each other, to switches, or to routers.

Characteristics of Ethernet Hubs

Ethernet hubs vary in the speed (network data rate or bandwidth) they support. Some years ago, Ethernet hubs offered only 10 Mbps rated speeds. Newer types of hubs offer 100 Mbps Ethernet. Some support both 10 Mbps and 100 Mbps (so-called dual-speed or 10/100 hubs).

The number of ports an Ethernet hub supports also varies. Four- and five-port Ethernet hubs are most common in home networks, but eight- and 16-port hubs can be found in some home and small office environments.

Older Ethernet hubs were relatively large in size and sometimes noisy as they contained built in fans for cooling the unit. Newer devices are much smaller, designed for mobility, and noiseless.

When To Use an Ethernet Hub

Ethernet hubs operate as Layer 2 devices in the OSI model, the same as network switches. Although offering comparable functionality, nearly all mainstream home network equipment today utilizes network switch technology instead of hubs due to the performance benefits of switches. A hub can be useful for temporarily replacing a broken network switch or when performance is not a critical factor on the network.

Ethernet

Definition: Ethernet is a physical and data link layer technology for local area networks (LANs). Ethernet was invented by engineer Robert Metcalfe.

When first widely deployed in the 1980s, Ethernet supported a maximum theoretical data rate of 10 megabits per second (Mbps). Later, Fast Ethernet standards increased this maximum data rate to 100 Mbps. Today, Gigabit Ethernet technology further extends peak performance up to 1000 Mbps.

Higher level network protocols like Internet Protocol (IP) use Ethernet as their transmission medium. Data travels over Ethernet inside protocol units called frames.

The run length of individual Ethernet cables is limited to roughly 100 meters, but Ethernet can be bridged to easily network entire schools or office buildings.

Also Known As: Fast Ethernet, Gigabit Ethernet

LAN - Local Area Network

Definition: A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other WAN.

Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. Wireless LAN and other more advanced LAN hardware options also exist.

Specialized operating system software may be used to configure a local area network. For example, most flavors of Microsoft Windows provide a software package called Internet Connection Sharing (ICS) that supports controlled access to LAN resources.

The term LAN party refers to a multiplayer gaming event where participants bring their own computers and build a temporary LAN.

Also Known As: local area network

Examples: The most common type of local area network is an Ethernet LAN. The smallest home LAN can have exactly two computers; a large LAN can accommodate many thousands of computers. Many LANs are divided into logical groups called subnets. An Internet Protocol (IP) "Class A" LAN can in theory accommodate more than 16 million devices organized into subnets.

WAN - Wide Area Network

Definition: A WAN spans a large geographic area, such as a state, province or country. WANs often connect multiple smaller networks, such as local area networks (LANs) or metro area networks (MANs).

The world's most popular WAN is the Internet. Some segments of the Internet, like VPN-based extranets, are also WANs in themselves. Finally, many WANs are corporate or research networks that utilize leased lines.

WANs generally utilize different and much more expensive networking equipment than do LANs. Key technologies often found in WANs include SONET, Frame Relay, and ATM.

Also Known As: wide area network

extranet

Definition: An extranet is a computer network that allows controlled access from the outside for specific business or educational purposes. Extranets are extensions to, or segments of, private intranet networks that have been built in many corporations for information sharing and ecommerce.

Most extranets use the Internet as the entry point for outsiders, a firewall configuration to limit access, and a secure protocol for authenticating users.

Related Resources:

Extranet Resources
Find out how to build and manage an extranet, see examples of succesful extranets in case studies, and discover the past and future of extranet networks.

Intranet Resources
Learn about building an intranet, content management, knowledge management, and hosting/outsourcing possibilities.

intranet

Definition: Intranet is the generic term for a collection of private computer networks within an organization. An intranet uses network technologies as a tool to facilitate communication between people or workgroups to improve the data sharing capability and overall knowledge base of an organization's employees.

Intranets utilize standard network hardware and software technologies like Ethernet, WiFi, TCP/IP, Web browsers and Web servers. An organization's intranet typically includes Internet access but is firewalled so that its computers cannot be reached directly from the outside.

A common extension to intranets, called extranets, opens this firewall to provide controlled access to outsiders.

Many schools and non-profit groups have deployed them, but an intranet is still seen primarily as a corporate productivity tool. A simple intranet consists of an internal email system and perhaps a message board service. More sophisticated intranets include Web sites and databases containing company news, forms, and personnel information. Besides email and groupware applications, an intranet generally incorporates internal Web sites, documents, and/or databases.

The business value of intranet solutions is generally accepted in larger corporations, but their worth has proven very difficult to quantify in terms of time saved or return on investment.

Also Known As: corporate portal, private business network

TCP/IP - Transmission Control Protocol / Internet Protocol

Definition: Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinct network protocols, technically speaking. TCP and IP are so commonly used together, however, that TCP/IP has become standard terminology to refer to either or both of the protocols.

IP corresponds to the Network layer (Layer 3) in the OSI model, whereas TCP corresponds to the Transport layer (Layer 4) in OSI. In other words, the term TCP/IP refers to network communications where the TCP transport is used to deliver data across IP networks.

The average person on the Internet works in a predominately TCP/IP environment. Web browsers, for example, use TCP/IP to communicate with Web servers.

Also Known As: Transmission Control Protocol / Internet Protocol

OSI Model - Open Systems Interconnection model

Layers of the OSI Model

Definition: The OSI model defines internetworking in terms of a vertical stack of seven layers. The upper layers of the OSI model represent software that implements network services like encryption and connection management. The lower layers of the OSI model implement more primitive, hardware-oriented functions like routing, addressing, and flow control.

In the OSI model, data communication starts with the top layer at the sending side, travels down the OSI model stack to the bottom layer, then traveses the network connection to the bottom layer on the receiving side, and up its OSI model stack.

The OSI model was introduced in 1984. Although it was designed to be an abstract model, the OSI model remains a practical framework for today's key network technologies like Ethernet and protocols like IP.

Also Known As: Open Systems Interconnection (OSI) reference model, OSI seven layer model

Examples: Internet Protocol (IP) corresponds to the Network layer of the OSI model, layer three. TCP and UDP correspond to OSI model layer four, the Transport layer. Lower layers of the OSI model are represented by technologies like Ethernet. Higher layers of the OSI model are represented by application protocols like TCP and UDP.

IP - Internet Protocol

Definition: IP is the primary network protocol used on the Internet, developed in the 1970s. On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.

IP supports unique addressing for computers on a network. Most networks use the IP version 4 (IPv4) standard that features IP addresses four bytes (32 bits) in length. The newer IP version 6 (IPv6) standard features addresses 16 bytes (128 bits) in length.

Data on an IP network is organized into [ipackets. Each IP packet includes both a header (that specifies source, destination, and other information about the data) and the message data itself.

IP functions at layer 3 of the OSI model. It can therefore run on top of different data link interfaces including Ethernet and Wi-Fi.

IP address

Definition: An IP address is a logical address for a network adapter. The IP address uniquely identifies computers on a TCP/IP network.

An IP address can be private - for use on a local area network (LAN) - or public - for use on the Internet or other wide area network (WAN). IP addresses can be determined statically (assigned to a computer by a system administrator) or dynamically (assigned by another device on the network on demand).

Two IP addressing standards are in use today. The IPv4 standard is most familar to people and supported everywhere on the Internet, but the newer IPv6 standard is planned to replace it and starting to be deployed.

IPv4 addresses consist of four bytes (32 bits). Each byte of an IP address is known as an octet. Octets can take any value between 0 and 255. Various conventions exist for the numbering and use of IP addresses.

Common IP (IPv4) Addresses -

• 10.0.0.1
• 127.0.0.1
• 192.168.0.1
• 192.168.1.1
• 192.168.2.1

Also Known As: IP number

VPN - Virtual Private Network

By Bradley Mitchell, About.com

Definition: A VPN utilizes public telecommunications networks to conduct private data communications. Most VPN implementations use the Internet as the public infrastructure and a variety of specialized protocols to support private communications through the Internet.

VPN follows a client and server approach. VPN clients authenticate users, encrypt data, and otherwise manage sessions with VPN servers utilizing a technique called tunneling.

VPN clients and VPN servers are typically used in these three scenarios:

1. to support remote access to an intranet,
2. to support connections between multiple intranets within the same organization, and
3. to join networks between two organizations, forming an extranet.

The main benefit of a VPN is the lower cost needed to support this technology compared to alternatives like traditional leased lines or remote access servers.

VPN users typically interact with simple graphical client programs. These applications support creating tunnels, setting configuration parameters, and connecting to and disconnecting from the VPN server. VPN solutions utilize several different network protocols including PPTP, L2TP, IPsec, and SOCKS.

VPN servers can also connect directly to other VPN servers. A VPN server-to-server connection extends the intranet or extranet to span multiple networks.

Many vendors have developed VPN hardware and software products. Some of these do not interoperate due to the immaturity of some VPN standards.

Also Known As: virtual private network

protocol (network)

Definition: A network protocol defines rules and conventions for communication between network devices. Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets.

Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received. Some protocols also support message acknowledgement and data compression designed for reliable and/or high-performance network communication. Hundreds of different computer network protocols have been developed each designed for specific purposes and environments.

Internet Protocols

The Internet Protocol family contains a set of related (and among the most widely used network protocols. Besides Internet Protocol (IP) itself, higher-level protocols like TCP, UDP, HTTP, and FTP all integrate with IP to provide additional capabilities. Similarly, lower-level Internet Protocols like ARP and ICMP also co-exist with IP. These higher level protocols interact more closely with applications like Web browsers while lower-level protocols interact with network adapters and other computer hardware.

Routing Protocols

Routing protocols are special-purpose protocols designed specifically for use by network routers on the Internet. Common routing protocols include EIGRP, OSPF and BGP.

How Network Protocols Are Implemented

Modern operating systems like Microsoft Windows contain built-in services or daemons that implement support for some network protocols. Applications like Web browsers contain software libraries that support the high level protocols necessary for that application to function. For some lower level TCP/IP and routing protocols, support is implemented in directly hardware (silicon chipsets) for improved performance.

HTTP

Definition: HTTP - the Hypertext Transfer Protocol - provides a standard for Web browsers and servers to communicate. The definition of HTTP is a technical specification of a network protocol that software must implement.

HTTP is an application layer network protocol built on top of TCP. HTTP clients (such as Web browsers) and servers communicate via HTTP request and response messages. The three main HTTP message types are GET, POST, and HEAD.

HTTP utilizes TCP port 80 by default, though other ports such as 8080 can alternatively be used.

The current version of HTTP in widespread use - HTTP version 1.1 - was developed to address some of the performance limitations of the original version - HTTP 1.0. HTTP 1.1 is documented in RFC 2068.

Also Known As: HyperText Transfer Protocol

FTP - What Does FTP Stand For?

Definition: FTP allows you to transfer files between two computers on the Internet. FTP is a simple network protocol based on Internet Protocol and also a term used when referring to the process of copying files when using FTP technology.

To transfer files with FTP, you use a program often called the "client." The FTP client program initiates a connection to a remote computer running FTP "server" software. After the connection is established, the client can choose to send and/or receive copies of files, singly or in groups. To connect to an FTP server, a client requires a username and password as set by the administrator of the server. Many public FTP archives follow a special convention for that accepts a username of "anonymous."

Simple FTP clients are included with most network operating systems, but most of these clients (such as FTP.EXE on Windows) support a relatively unfriendly command-line interface. Many alternative freeware / shareware third-party FTP clients have been developed that support graphic user interfaces (GUIs) and additional convenience features. In any FTP interface, clients identify the FTP server either by its IP address (such as 192.168.0.1) or by its host name (such as ftp.about.com).

FTP supports two modes of data transfer: plain text (ASCII), and binary. You set the mode in the FTP client. A common error when using FTP is attempting to transfer a binary file (such as a program or music file) while in text mode, causing the transfered file to be unusable.

Also Known As: File Transfer Protocol

UDP

Definition: UDP is a lightweight transport built on top of IP. UDP squeezes extra performance from IP by not implementing some of the features a more heavyweight protocol like TCP offers. Specifically, UDP allows individual packets to be dropped (with no retries) and UDP packets to be received in a different order than they were sent.

UDP is often used in videoconferencing applications or games where optimal performance is preferred over guaranteed message delivery. UDP is one of the oldest network protocols, introduced in 1980 in RFC document 768.

Also Known As: User Datagram Protocol

Related Resources:

UDP - Introduction to User Datagram Protocol
This article explains UDP, describing its place in the OSI model and the use of headers, port numbers, payloads, and checksums in UDP. The article also compares UDP with TCP.

ARP - Address Resolution Protocol

Definition: ARP converts an Internet Protocol (IP) address to its corresponding physical network address. ARP is a low-level network protocol, operating at Layer 2 of the OSI model.

ARP usually is implemented in the device drivers of network operating systems. It is most commonly seen on Ethernet networks, but ARP has also been implemented for ATM, Token Ring, and other physical networks. RFC 826 documented the initial design and implementation of ARP.

ARP works on Ethernet networks as follows. Ethernet network adapters are produced with a physical address embedded in the hardware called the Media Access Control (MAC) address. Manufacturers take care to ensure these 6-byte (48-bit) addresses are unique, and Ethernet relies on these unique identifiers for message delivery. When any device wishes to send data to another target device over Ethernet, it must first determine the MAC address of that target given its IP address These IP-to-MAC address mappings are derived from an ARP cache maintained on each device. If the given IP address does not appear in a device's cache, that device cannot direct messages to that target until it obtains a new mapping. To do this, the initiating device first sends an ARP request broadcast message on the local subnet. The host with the given IP address sends an ARP reply in response to the broadcat, allowing the initiating device to update its cache and proceed to deliver messages directly to the target.

Also Known As: Address Resolution Protocol

MAC - Media Access Control and Address

Definition: MAC technology provides unique identification and access control for computers on an Internet Protocol (IP) network. In wireless networking, MAC is the radio control protocol on the wireless network adapter. MAC works at the lower sublayer of the data link layer (Layer 2) of the OSI model.

MAC assigns a unique number to each IP network adapter called the MAC address. A MAC address is 48 bits long. The MAC address is commonly written as a sequence of 12 hexadecimal digits as follows:

48-3F-0A-91-00-BC

MAC addresses are uniquely set by the network adapter manufacturer and are sometimes called "physical addresses" for this reason. The first six hexadecimal digits of the address correspond to a manufacturer's unique identifier, while the last six digits correspond to the device's serial number. MAC addresses map to logical IP addresses through the Address Resolution Protocol (ARP).

Some Internet service providers track the MAC address of a home router for security purposes. Many routers support a process called cloning that allows the MAC address to be simulated so that it matches one the service provider is expecting. This allows households to change their router (and their real MAC address) without having to notify the provider.

Also Known As: Media Access Control

adapter

Definition: A network adapter interfaces a computer to a network. The term "adapter" was popularized originally by Ethernet add-in cards for PCs.

Modern network adapter hardware exists in several forms. Besides traditional PCI Ethernet cards, some network adapters are PCMCIA devices (also know as "credit card" or "PC Card" adapters) or USB devices. Some wireless network adapter gear for laptop computers are integrated circuit chips pre-installed inside the computer.

Windows and other operating systems support both wired and wireless network adapters through a piece of software called a "device driver." Network drivers allow application software to communicate with the adapter hardware. Network device drivers are often installed automatically when adapter hardware is first powered on.

A few network adapters are purely software packages that simulate the functions of a network card. These so-called virtual adapters are especially common in virtual private networking (VPN).

Also Known As: NIC, LAN card

subnet

Definition: A subnet is a logical grouping of connected network devices. Nodes on a subnet tend to be located in close physical proximity to each other on a LAN.

Network designers employ subnets as a way to partition networks into logical segments for greater ease of administration. When subnets are properly implemented, both the performance and security of networks can be improved.

In IP networking, devices on a subnet share contiguous ranges of IP address numbers. A mask (known as the subnet mask or network mask) defines the boundaries of an IP subnet. The correspondence between subnet masks and IP address ranges follows defined mathematical formulas. IT professionals use subnet calculators to map between masks and addresses.

Also Known As: subnetwork

router

Definition: Routers are physical devices that join multiple wired or wireless networks together. Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks (as gateways do), and that the router operates at the network layer of the OSI model.

Home networkers often use an Internet Protocol (IP) wired or wireless router, IP being the most common OSI network layer protocol. An IP router such as a DSL or cable modem broadband router joins the home's local area network (LAN) to the wide-area network (WAN) of the Internet.

By maintaining configuration information in a piece of storage called the "routing table," wired or wireless routers also have the ability to filter traffic, either incoming or outgoing, based on the IP addresses of senders and receivers. Some routers allow the home networker to update the routing table from a Web browser interface. Broadband routers combine the functions of a router with those of a network switch and a firewall in a single unit.

See also > broadband routers

broadband router

Definition: A broadband router combines the features of a traditional network switch, a firewall, and a DHCP server. Broadband routers are designed for convenience in setting up home networks, particularly for homes with high-speed cable modem or DSL Internet service. A broadband router supports file sharing, Internet connection sharing, and home LAN gaming.

A broadband router follow the Ethernet standard for home networking. Traditional broadband routers required Ethernet cables be run between the router, the broadband modem, and each computer on the home LAN. The newer wireless routers also support broadband Internet access and the Ethernet standard without the need for cabling.

Several manufacturers offer broadband router products to the consumer. Features that differentiate broadband router products include the number and type of ports available on the unit for cabling computers, external modems, or other network devices.

Also Known As: residential gateway, home gateway

Networking With A Router

Using a router on broadband and/or wireless home networks

A network router is a small electronic device that allows you build a home network simply. The home router serves as the core or "centerpiece" of the network to which computers, printers and other devices can be connected. Networking with a router helps you to (for example):

• share files between computers
• share an Internet connection between computers
• share a printer
• connect your game console or other home entertainment equipment to the Internet

Routers are not necessarily required to build a network. For example, you can connect two computers directly to each other with just a cable (or without wires in some cases). Home routers offer convenience and easier maintenance as your network grows.

• Related - Connecting Two Home Computers

Choosing a Network Router

You can choose from among several different types of home network router products. The two most common types in popular usage are the 802.11b and 802.11g WiFi models. 802.11g is the newer technology, but 802.11b routers often can do the job for an even lower cost.

• More - Choosing a Wireless Router
• Gear - Top 802.11g Wireless Routers
• Gear - Top 802.11b Wireless Routers

Installing a Network Router

Network routers receive their power from an ordinary home electrical socket. When powered on, lights (LEDs) signify the unit is operating.

Network routers must be carefully configured when they are first installed. Like computers and other devices on the home network, routers must be set up with IP addresses. Routers also offer optional (but strongly recommended) security features.

Routers contain built-in software to enable setup. You access this software through your Web browser on any computer connected to the router.

• More - How To Set Up a Router

Next > Connecting Devices to A Router

DHCP - Dynamic Host Configuration Protocol

Definition: DHCP allows a computer to join an IP-based network without having a pre-configured IP address. DHCP is a protocol that assigns unique IP addresses to devices, then releases and renews these addresses as devices leave and re-join the network.

Internet Service Providers (ISPs) usually use DHCP to allow customers to join the Internet with minimum effort. Likewise, home network equipment like broadband routers offers DHCP support for added convenience in joining home computers to the LAN.

DHCP environments require a DHCP server set up with the appropriate configuration parameters for the given network. Key DHCP parameters include the range or "pool" of available IP addresses, the correct subnet masks, plus gateway and name server addresses.

Devices running DHCP client software can then automatically retrieve these settings from DHCP servers as needed. Using DHCP on a network means system administrators do not need to configure these parameters individually for each client device.

Also Known As: Dynamic Host Configuration Protocol

gateway

Definition: A network gateway is an internetworking system capable of joining together two networks that use different base protocols. A network gateway can be implemented completely in software, completely in hardware, or as a combination of both. Depending on the types of protocols they support, network gateways can operate at any level of the OSI model.

Because a network gateway, by definition, appears at the edge of a network, related capabilities like firewalls tend to be integrated with it. On home networks, a broadband router typically serves as the network gateway although ordinary computers can also be configured to perform equivalent functions.

See also - What Is a Default Gateway?

How To Set Up a Network Router

This guide explains how to set up a router for home computer networks. The exact names of configuration settings on a network router vary depending on the model and whether it is wired or wireless. However, this general procedure will guide you through the process for the common kinds of home network equipment.

Difficulty: Average

Time Required: 1 hour

Here's How:

1. Choose a convenient location to begin installing your router such as an open floor space or table. This does not need to be the permanent location of the device. Particularly for wireless routers, you may find it necessary to re-position the unit after installing it as the cables / signals may not reach all areas needed. At the beginning, its better to choose a location where it's easiest to work with the router and worry about final placement later.
2. Plug in the router's electrical power source, then turn on the router by pushing the power button.
3. (Optional) Connect your Internet modem to the router. Most network modems connect via an Ethernet cable but USB connections are becoming increasingly common. The cable plugs into the router jack named "WAN" or "uplink" or "Internet." After connecting the cable, be sure to power cycle (turn off and turn back on) the modem to ensure the router recognizes it.
4. Connect one computer to the router. Even if the router is a wireless model, connect this first computer to the router via a network cable. Using a cable during router installation ensures the maximum reliability of the equipment. Once a wireless router installation is complete, the computer can be changed over to a wireless connection if desired.
5. Open the router's administration tool. From the computer connected to the router, first open your Web browser. Then enter the router's address for network administration in the Web address field and hit return to reach the router's home page.
   
   Many routers are reached by either the Web address "http://192.168.1.1" or "http://192.168.0.1" Consult your router's documentation to determine the exact address for your model. Note that you do not need a working Internet connection for this step.
6. Log in to the router. The router's home page will ask you for a username and password. Both are provided in the router's documentation. You should change the router's password for security reasons, but do this after the installation is complete to avoid unnecessary complications during the basic setup.
7. If you want your router to connect to the Internet, you must enter Internet connection information into that section of the router's configuration (exact location varies). If using DSL Internet, you may need to enter the PPPoE username and password. Likewise, if you have been issued a static IP address by your provider (you would need to have requested it), the static IP fields (including network mask and gateway) given to you by the provider must also must be set in the router.
8. If you were using a primary computer or an older network router to connect to the Internet, your provider may require you to update the MAC address of the router with the MAC address of the device you were using previously. Read How to Change a MAC Address for a detailed description of this process.
9. If this is a wireless router, change the network name (often called SSID). While the router comes to you with a network name set at the factory, you will never want to use this name on your network. Read How to Change the Router SSID for detailed instructions.
10. Verify the network connection is working between your one computer and the router. To do this, you must confirmed that the computer has received IP address information from the router. See How to Find IP Addresses for a description of this process.
11. (If applicable) Verify your one computer can connect to the Internet properly. Open your Web browser and visit a few Internet sites such as http://compnetworking.about.com/.
12. Connect additional computers to the router as needed. If connecting wirelessly, ensure the network name (SSID) of each is computer matches that of the router.
13. Finally, configure additional network security features as desired to guard your systems against Internet attackers. These WiFi Home Network Security Tips offer a good checklist to follow.

Tips:

1. When connecting devices with network cables, be sure each end of the cable connects tightly. Loose cables are one of the most common sources of network setup problems.

What You Need:

• A network router (wireless or wired)
• Network adapters installed on all devices to be connected to the router
• A working Internet modem (optional)
• A Web browser installed at least one computer in the network

What Is a Default Gateway?

Question: What Is a Default Gateway?

You will sometimes see the term default gateway on network configuration screens in Microsoft Windows.

Answer: In computer networking, a default gateway is the device that passes traffic from the local subnet to devices on other subnets. The default gateway often connects a local network to the Internet, although internal gateways for local networks also exist.

Internet default gateways are typically one of two types:

• On home or small business networks with a broadband router to share the Internet connection, the home router serves as the default gateway.
• On home or small business networks without a router, such as for residences with dialup Internet access, a router at the Internet Service Provider location serves as the default gateway.

Default network gateways can also be configured using an ordinary computer instead of a router. These gateways use two network adapters, one connected to the local subnet and one to the outside network. Either routers or gateway computers can be used to network local subnets such as those in larger businesses.

In Microsoft Windows, the IP address of a computer's default gateway can be accessed in the 'ipconfig' or 'winipcfg' utilities (see sidebar).

PCMCIA - Personal Computer Memory Card International Association

Definition: PCMCIA is an industry organization best know for developing a standard network adapter using the PC Card form factor. The PC Card form factor was designed for thinness, and PCMCIA is therefore especially well suited for notebook computers. Most notebooks contain two PCMCIA slots that hold one or two of these cards.

PC Cards come in three types. All PC Cards have the same width and length - 54.0 millimeters wide and 85.6 millmeters long - but vary in thickness:

• Type 1 - 3.3 millimeters thick
• Type 2 - 5.0 millimeters thick
• Type 3 - 10.5 millimeters thick

Ethernet PCMCIA network adapters were originally all Type 2 PC Cards. These cards feature a dual-speed or Fast Ethernet jack and sometimes a second jack for an onboard dial-up modem. Type 1 PC Cards cards generally contain computer memory and Type 3 cards generally contain disk storage.

Type 2 PC Cards are too thin to fit a full-sized Ethernet (RJ-45) jack and/or a full-sized phone (RJ-11) jack. Instead, Type 2 Ethernet PCMCIA cards require proprietary jacks and short external cables called dongles that interface a proprietary jack to a standard one.

However, an increasing number of PCMCIA Ethernet adapters are now being built using the Type 3 form factor. Being twice as thick as Type 2 adapters, Type 3 adapters work without dongles because they fit a full-sized Ethernet (RJ-45) jack and/or a full-sized phone (RJ-11) jack. One Type 3 ("double high") adapter fills both PCMCIA slots in a notebook computer.

Also Known As: PC Card; Personal Computer Memory Card International Association; People Can't Memorize Computer Industry Acronyms

dongle

Definition: In computer networking, a dongle is a short network cable that joins a PCMCIA adapter to a network cable. Dongles typically attach to either a RJ-45 connector for Ethernet networking or an RJ-11 connector for dial-up networking. Dongles tend to run no longer than about six inches.

The term "dongle" also has become popular in USB networking, referring to the USB cable that extends from a USB peripheral.

The term "dongle" has an older, much less common in non-network computing, pertaining to software security.

Pronunciation: DONG-ul

firewall

Definition: A network firewall protects a computer network from unauthorized access. Network firewalls may be hardware devices, software programs, or a combination of the two.

Network firewalls guard an internal computer network (home, school, business intranet) against malicious access from the outside. Network firewalls may also be configured to limit access to the outside from internal users.

Network Firewalls and Broadband Routers

Many home network router products include built-in firewall support. The administrative interface of these routers include configuration options for the firewall. Router firewalls can be turned off (disabled), or they can be set to filter certain types of network traffic through so-called firewall rules.

Network Firewalls and Proxy Servers

Another common form of network firewall is a proxy server. Proxy servers act as an intermediary between internal computers and external networks by receiving and selectively blocking data packets at the network boundary. These network firewalls also provide an extra measure of safety by hiding internal LAN addresses from the outside Internet. In a proxy server firewall environment, network requests from multiple clients appear to the outsider as all coming from the same proxy server address.

Also Known As: proxy, gateway

ICMP

Definition: ICMP is a network protocol useful in Internet Protocol (IP) network management and administration. ICMP is a required element of IP implementations. ICMP is a control protocol, meaning that it does not carry application data, but rather information about the status of the network itself. ICMP can be used to report:

• errors in the underlying communications of network applications
• availability of remote hosts
• network congestion

Perhaps the best known example of ICMP in practice is the ping utility, that uses ICMP to probe remote hosts for responsiveness and overall round-trip time of the probe messages. ICMP also supports traceroute, that can identify intermediate "hops" between a given source and destination.

Also Known As: Internet Control Message Protocol

Ping

Definition: Ping is the name of a standard network utility packaged with popular network operating systems. The utility can be used to determine if a remote device (such as Web or game server) can be reached on the network and, if so, roughly how fast the current connection is.

Traditional pings are implemented with the Internet Control Message Protocol (ICMP), although it is possible to achieve a similar effect with UDP or other protocols. Ping utilities send requests to the designated computer at periodic intervals and measure the time it takes for a respone packet to arrive. A number of popular "ping tools" that add features to the operating system commands are available on the Net today. By manipulating the contents of ICMP packets, hackers have also used ping utilties to take down servers in the so-called "Ping of Death" attack.

Also Known As: Packet Internet Gopher

network address

Definition: A network address serves as a unique identifier for a computer on a network. When set up correctly, computers can determine the addresses of other computers on the network and use these addresses to send messages to each other.

One of the best known form of network addressing is the Internet Protocol (IP) address. IP addresses consist of four bytes (32 bits) that uniquely identify all computers on the public Internet.

Another popular form of address is the Media Access Control (MAC) address. MAC addresses are six bytes (48 bits) that manufacturers of network adapters burn into their products to uniquely identify them.

bit

Definition: A bit is the smallest unit of data transfer on a computer network. Bits represent the two binary values "on" or "off." Bits are often stored on computers as the digital numbers '1' and '0', but in networking, bits can also be "encoded" by electrical signals and pulses of light.

In computer networking, some network protocols send and receive data in the form of bit sequences. These are called bit-oriented protocols. Examples of bit-oriented protocols include PPP.

Though sometimes written in decimal or byte form, network addresses like IP addresses and MAC addresses are ultimately represented as bits in network communications.

Finally, special digital numbers called "keys" are often used to encrypt data on computer networks. The length of these keys is expressed in terms of number of bits. The greater the number of bits, the relatively more effective that key is in protecting data. In wireless network security, for example, 40-bit WEP keys proved to be relatively insecure but the 128-bit or larger WEP keys used today are much more effective.

Also Known As: binary digit

WEP - Wired Equivalent Privacy

Definition: WEP is a protocol that adds security to wireless local area networks (WLANs) based on the 802.11 Wi-Fi standard. WEP is an OSI Data Link layer (Layer 2) security technology that can be turned "on" or "off." WEP was designed to give wireless networks the equivalent level of privacy protection as a comparable wired network.

WEP is based on a security scheme called RC4 that utilizes a combination of secret user keys and system-generated values. The original implementations of WEP supported so-called 40-bit encryption, having a key of length 40 bits and 24 additional bits of system-generated data (64 bits total). Research has shown that 40-bit WEP encryption is too easy to decode, and consequently product vendors today employ 128-bit encryption (having a key length of 104 bits, not 128 bits) or better (including 152-bit and 256-bit WEP systems).

When communicating over the wire, wireless network equipment uses WEP keys to encrypt the data stream. The keys themselves are not sent over the network but rather are generally stored on the wireless adapter or in the Windows Registry.

Regardless of how it is implemented on a wireless LAN, WEP represents just one element of an overall WLAN security strategy.

Also Known As: Wired Equivalent Privacy

Wi-Fi - Wireless Fidelity

Definition: Wi-Fi is the industry name for wireless LAN (WLAN) communication technology related to the IEEE 802.11 family of wireless networking standards. To some, the term Wi-Fi is synonymous with 802.11b, as 802.11b was the first standard in that family to enjoy widespread popularity. Today, however, Wi-Fi can refer to any of the established standards: 802.11a, 802.11b, 802.11g and 802.11n.

The Wi-Fi Alliance (see sidebar) certifies vendor products to ensure 802.11 products on the market follow the various 802.11 specifications. Unfortunately, 802.11a is not compatible with 802.11b/g, so the Wi-Fi market remains somewhat fragmented.

Also Known As: wireless fidelity

WLAN

Definition: WLANs provide wireless network communication over short distances using radio or infrared signals instead of traditional network cabling.

A WLAN typically extends an existing wired local area network. WLANs are built by attaching a device called the access point (AP) to the edge of the wired network. Clients communicate with the AP using a wireless network adapter similar in function to a traditional Ethernet adapter.

Network security remains an important issue for WLANs. Random wireless clients must usually be prohibited from joining the WLAN. Technologies like WEP raise the level of security on wireless networks to rival that of traditional wired networks.

Also Known As: wireless LAN

Examples: For WLANs that connect to the Internet, Wireless Application Protocol (WAP) technology allows Web content to be more easily downloaded to a WLAN and rendered on wireless clients like cell phones and PDAs.

server

Definition: A network server is a computer designed to process requests and deliver data to other (client) computers over a local network or the Internet.

Network servers typically are configured with additional processing, memory and storage capacity to handle the load of servicing clients. Common types of network servers include:

• Web servers
• proxy servers
• FTP servers
• online game servers

Numerous systems use this client / server networking model including Web sites and email services. An alternative model, peer-to-peer networking enables all computers to act as either a server or client as needed.

Apache

Definition: Apache is generally recognized as the world's most popular Web server (HTTP server). Originally designed for Unix servers, the Apache Web server has been ported to Windows and other network operating systems (NOS). The name "Apache" derives from the word "patchy" that the Apache developers used to describe early versions of their software.

The Apache Web server provides a full range of Web server features, including CGI, SSL, and virtual domains. Apache also supports plug-in modules for extensibility. Apache is reliable, free, and relatively easy to configure.

Apache is free software distributed by the Apache Software Foundation. The Apache Software Foundation promotes various free and open source advanced Web technologies

NOS - Network Operating System

Definition: A NOS is a network operating system. A network operating system implements protocol stacks as well as device drivers for networking hardware. Some network operating systems, like Windows 98 Second Edition, also add custom networking features like Internet Connection Sharing (ICS).

Network operating systems have existed for more than thirty years. The UNIX® operating system was designed from the beginning to support networking. In its early forms, Windows did not support networking, so Novell NetWare became the first popular network operating system for the personal computer (Windows 95 and Windows for Workgroups were Microsoft's first network operating system products). Today, nearly any consumer operating system qualifies as a NOS due to the popularity of the Internet and the obvious need to support Internet Protocol (IP) networking at a minimum.

Also Known As: network operating system

Web Servers

Web server applications provide network access to Web pages and other intranet and Internet content.

Microsoft Internet Infor...

Apache Web Server
Apache consistently rates as the world's most popular Web server. It is full-featured, reliable, and free.

Crash

Definition: The term "crash" refers to a critical failure in a computer, network device, or software running on these (such as a network operating system or application). Crashes often occur with little or no warning. As evidenced by the number of different synonyms employed over the years, crashes have a long and colorful history in computer networking.

A crash can manifest itself in many different ways. The computer may "freeze" or "hang" indefinitely when a crash occurs, or it may display any number of obscure error messages. In Windows operating systems, a crash usually causes the infamous "blue screen of death" to appear. To recover from a crash, often a person must power down and restart their computer (as in the case of blue screens) or their network device(s).

Also Known As: crash and burn, fatal error, bomb, blow-up, core dump, blue screen of death (BSOD), ABEND

MTU

Definition: The MTU is the maximum size of a single data unit (e.g., a frame) of digital communications. MTU sizes are inherent properties of physical network interfaces, normally measured in bytes. The MTU for Ethernet, for instance, is 1500 bytes. Some types of networks (like Token Ring) have larger MTUs, and some types have smaller MTUs, but the values are fixed for each physical technology.

Higher-level network protocols like TCP/IP can be configured with a maximum packet size, a parameter independent of the physical layer MTU over which TCP/IP runs. Unfortunately, many network devices use the terms interchangeably. On both home broadband routers and Xbox Live enabled game consoles, for example, the parameter called MTU is in fact the maximum TCP packet size and not the physical MTU.

In Microsoft Windows, the maximum packet size for protocols like TCP can be set in the Registry. If this value is set too low, streams of network traffic will be broken up into a relatively large number of small packets that adversely affects performance. Xbox Live, for example, requires the value of MTU (packet size) by at least 1365 bytes. If the maximum TCP packet size is set too high, it will exceed the network's physical MTU and also degrade performance by requiring that each packet be subdivided into smaller ones (a process known as fragmentation). Microsoft Windows computers default to a maximum packet size of 1500 bytes for broadband connections and 576 bytes for dialup connections.

Performance problems may also occur if the TCP "MTU" setting on the home broadband router differs from the setting on individual devices connected to it.

Also Known As: Maximum Transmission Unit

byte

Definition: A byte is a sequence of bits. In computer networking, some network protocols send and receive data in the form of byte sequences. These are called byte-oriented protocols. Examples of byte-oriented protocols include TCP/IP and telnet.

The order in which bytes are sequenced in a byte-oriented network protocol is called the network byte order. The maximum size of a single unit of transmission for these protocols, the Maximum Transmission Unit (MTU), is also measured in bytes. Network programmers routinely work both with network byte ordering and MTUs.

Bytes are used not only in networking, but also for computer disks, memory, and central processing units (CPUs). In all modern network protocols, a byte contains eight bits. A few (generally obsolete) computers may use bytes of different sizes for other purposes.

The sequence of bytes in other parts of the computer may not follow the network byte order. Part of the job of the networking subsystem of a computer is to convert between the host byte order and network byte order when needed.

ISP - Internet Service Providers

Definition: An ISP is a company that supplies Internet connectivity to home and business customers. ISPs support one or more forms of Internet access, ranging from traditional modem dial-up to DSL and cable modem broadband service to dedicated T1/T3 lines.

More recently, wireless Internet service providers or WISPs have emerged that offer Internet access through wireless LAN or wireless broadband networks.

In addition to basic connectivity, many ISPs also offer related Internet services like email, Web hosting and access to software tools.

A few companies also offer free ISP service to those who need occasional Internet connectivity. These free offerings feature limited connect time and are often bundled with some other product or service.

modem

Definition: Traditional modems used in dial-up networking convert data between the analog form used on telephone lines and the digital form used on computers. Standard dial-up network modems transmit data at a maximum rate of 56,000 bits per second (56 Kbps). However, inherent limitations of the public telephone network limit modem speeds to 33.6 Kbps or lower in practice.

Broadband modems that are part of cable and DSL Internet service use more advanced signaling techniques to achieve dramatically higher network speeds than traditional modems. Broadband modems are sometimes called "digital modems" and those used for traditional dial-up networking, "analog modems." Cellular modems that establish Internet connectivity through a digital cell phone also exist.

Also Known As: MODulator dEModulator

Kbps / kbps, Mbps, Gbps

Definition: One kilobit per second (Kbps) equals 1000 bits per second (bps). Kbps is also written as “kbps” that carries the same meaning. Likewise, one megabit per second (Mbps) equals one million bps and one Gigabit equals one billion bps.

Network performance is best measured in bps, but sometimes numbers are given in bytes per second (Bps). Then, one KBps equals one kilobyte per second, one MBps equals one megabyte per second, and GBps equals one gigabyte per second. Many times people write KBps, for example, when they mean Kbps, and it is important to be clear on this distinction.

Examples: V.90 modems support data rates up to 56 Kbps. Traditional Ethernet supports data rates up to 10 Mbps and Fast Ethernet 100 Mbps. Gigabit Ethernet supports 1000 Mbps or 1 Gbps.

Also Known As: Kb/sec, Kb/s, Mb/sec, Mb/s, Gb/sec, Gb/s

kilobyte, megabyte, gigabyte

Definition: A kilobyte equals 1024 (or 2¹⁰) bytes. Likewise, a megabyte (MB) equals 1024 KB or 2²⁰ bytes and a gigabyte (GB) equals 1024 MB or 2³⁰ bytes.

The meaning of the words kilobyte, megabyte, and gigabyte change when they are used in the context of network data rates. A rate of one kilobyte per second (KBps) equals 1000 (not 1024) bytes per second. One megabyte per second (MBps) equals one million (10⁶, not 2²⁰) bytes per second. One gigabyte per second (GBps) equals one billion (10⁹, not 2³⁰) bytes per second.

To avoid some of this confusion, networkers typically measure data rates in bits per second (bps) rather than bytes per second (Bps) and use the terms kilobyte, megabyte, and gigabyte only when referring to disk space.

Examples: "This eight gigabyte disk only has 200 megabytes of free space left."

Also Known As: K, KB, M, MB, "meg," G, GB, "gig"

baud

Definition: A baud is a unit of measure for analog signaling. At a minimum, one baud corresponds to one bit per second (bps) although at higher signaling speeds, multiple bits can be transfered in a single baud.

The term baud was popular in the early days of modems, but it is no longer relevant in mainstream computer networking terminology.

bps / Bps

Definition: Network performance has traditionally been measured in units of bits per second (bps). Not too many years ago, dialup network connections routinely performed at 9600 bps. As networks have greatly improved in performance, rates are now specified in Kbps (thousands of bps) or Mbps (millions of bps).

Bps (with uppercase 'B') represents bytes per second. Use of Bps, KBps, or MBps is avoided in networking as computer architectures implement a byte with differing numbers of bits; some use four bits, most use eight bits, and a few use neither.

Because eight-bit byte architectures dominate today, converting from Bps to bps involves only multiplying by eight. However, it's too easy to confuse the two acronyms and best to use 'bps' consistently.

Also Known As: bits per second, bits/sec, bits/s; bytes per second, bytes/sec, bytes/s

IPv6

Definition: IPv6 is the next generation protocol for Internet networking. IPv6 expands on the current Internet Protocol standard known as IPv4. Compared to IPv4, IPv6 offers better addressing, security and other features to support large worldwide networks.

In IPv6, IP addresses change from the current 32-bit standard and dotted decimal notation to a new 128-bit address system. IPv6 addresses remain backward compatible with IPv4 addresses. For example, the IPv4 address "192.168.100.32" may appear in IPv6 notation as "0000:0000:0000:0000:0000:0000:C0A8:6420" or "::C0A8:6420".

The most obvious benefit of IPv6 is the exponentially greater number of IP addresses it can support compared to IPv4. Many countries outside the U.S. suffer from a shortage of IP addresses today. Because IPv6 and IPv4 protocols coexist, those locales with an address shortage can easily deploy new IPv6 networks that work with the rest of the Internet. Experts believe it will take many more years before all networks fully change over to IPv6.

Other benefits of IPv6 are less obvious but equally important. The internals of the IPv6 protocol have been designed with scalability and extensibility in mind. This will allow many different kinds of devices besides PCs, like cell phones and home appliances, to more easily join the Internet in future.

Also Known As: IPng (Internet Protocol Next Generation)

port number

Definition: A port number represents an endpoint or "channel" for network communications. Port numbers allow different applications on the same computer to utilize network resources without interfering with each other.

Port numbers most commonly appear in network programming, particularly socket programming. Sometimes, though, port numbers are made visible to the casual user. For example, some Web sites a person visits on the Internet use a URL like the following:

http://www.mairie-metz.fr:8080/

In this example, the number 8080 refers to the port number used by the Web browser to connect to the Web server. Normally, a Web site uses port number 80 and this number need not be included with the URL (although it can be).

In IP networking, port numbers can theoretically range from 0 to 65535. Most popular network applications, though, use port numbers at the low end of the range (such as 80 for HTTP). The port number is included as a field within the header of each IP packet.

Note: The term port also refers to several other aspects of network technology. A port can refer to a physical connection point for peripheral devices such as serial, parallel, and USB ports. The term port also refers to certain Ethernet connection points, such as those on a hub, switch, or router.

Also Known As: port number, protocol number

RPC - Remote Procedure Call

Definition: RPC is a network programming model for point-to-point communication within or between software applications.

In RPC, the sender makes a request in the form of a procedure, function, or method call. RPC translates these calls into requests sent over the network to the intended destination. The RPC recipient then processes the request based on the procedure name and argument list, sending a response to the sender when complete. RPC applications generally implement software modules called "proxies" and "stubs" that broker the remote calls and make them appear to the programmer the same as local procedure calls (LPC).

RPC calling applications usually operate synchronously, waiting for the remote procedure to return a result. RPC incorporates timeout logic to handle network failures or other situations where RPCs do not return.

RPC has been a common programming technique in the Unix world since the 1990s. The Open Systems Foundation (OSF) Distributed Computing Environment (DCE) and Sun Microsystems Open Network Computing (ONC) libraries both were widely deployed. More recent examples of RPC technologies include Microsoft DCOM, Java RMI, and XML-RPC and SOAP.

URL

Definition: A URL is a specially-formatted text string that defines a location on the Internet. URL strings contain three parts or substrings:

1. network protocol
2. host name or address
3. file location

The network protocol substring determines the underlying Internet protocol to be used in reaching the location. These strings consist of a standard protocol name followed by the :// characters. Typical protocols found in URLs include http://, ftp://, and mailto://.

The host substring immediately follows the protocol defintion. Hosts may be defined by Internet-standard naming (DNS) or by IP address. For example, a URL of of http://compnetworking.about.com or, equivalently, http://209.143.212.20 contains the protocol and host information needed to access this Web site.

The file location portion of a URL defines the location of a network resource. Resources are files that can be plain text files, documents, graphics, or programs, and resource names are relative to a local root directory. Technically, a URL like http://compnetworking.about.com contains an implied file location of /, that Web servers like Apache automatically translate to a specific file name like index.htm. All other specific files exist in a hierarchy or directory tree underneath the root, such as the following:

RELATIVE FILE LOCATION
/library/glossary/blglossary.htm

COMPLETE URL
http://compnetworking.about.com/library/glossary/blglossary.htm

When creating HTML pages, the author can choose to use either the relative file locations or complete URLs. A user of the Internet generally works with complete URLs.

Also Known As: Uniform Resource Locator

DNS - Domain Name System

Definition: The DNS translates Internet domain and host names to IP addresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites.

DNS implements a distributed database to store this name and address information for all public hosts on the Internet. DNS assumes IP addresses do not change (are statically assigned rather than dynamically assigned).

The DNS database resides on a hierarchy of special database servers. When clients like Web browsers issue requests involving Internet host names, a piece of software called the DNS resolver (usually built into the network operating system) first contacts a DNS server to determine the server's IP address. If the DNS server does not contain the needed mapping, it will in turn forward the request to a different DNS server at the next higher level in the hierarchy. After potentially several forwarding and delegation messages are sent within the DNS hierarchy, the IP address for the given host eventually arrives at the resolver, that in turn completes the request over Internet Protocol.

DNS additionally includes support for caching requests and for redundancy. Most network operating systems support configuration of primary, secondary, and tertiary DNS servers, each of which can service initial requests from clients. ISPs maintain their own DNS servers and use DHCP to automatically configure clients, relieving most home users of the burden of DNS configuration.

Also Known As: Domain Name System, Domain Name Service, Domain Name Server

XML-RPC

Definition: XML-RPC is a network programming technique for making remote procedure calls (RPC) to software running on remote devices. XML-RPC uses XML coding for calls and sends messages using the Hypertext Transfer Protocol (HTTP).

Developers commonly use XML-RPC to develop Web services. Reusable XML-RPC libraries are widely available for Windows, Java, modern scripting languages like Perl and Python, and other enviroments. Because XML-RPC uses HTTP, these XML-RPC libraries function in firewall or proxied environments.

XML-RPC serves a similar function to Simple Object Access Protocol (SOAP), that supports remote object method invocations using XML over HTTP.

Alternate Spellings: xmlrpc

API - Application Programming Interface

Definition: An API allows computer programmers to access the functionality of pre-built software modules. An API defines data structures and subroutine calls. Networking APIs are entry points to libraries that implement network and data communication protocols.

Traditionally, the primary networking APIs have been implemented in socket libraries. Berkeley sockets and Windows Sockets (Winsock) APIs have seen widespread use for many years. More recently, Java network APIs such as servlets and Web APIs like XML-RPC have emerged as newer network programming standards.

Also Known As: Application Programming Interface

NetBIOS

Definition: NetBIOS is a software protocol for providing computer communication services on local networks. Microsoft Windows uses NetBIOS on Ethernet or Token Ring networks.

Software applications on a NetBIOS network locate each other via their NetBIOS names. A NetBIOS name is up to 16 characters long and in Windows, separate from the computer name. Applications on other computers access NetBIOS names over UDP port 137. The provides name resolution services for NetBIOS.

Two applications start a NetBIOS session when one (the client) sends a command to "Call" another (the server) over TCP port 139 on a remote computer. Both sides issue "Send" and "Receive" commands to deliver messages in both directions. The "Hang-Up" command terminates a NetBIOS session.

NetBIOS also supports connectionless communications via UDP datagrams. Applications listen on UDP port 138 to receive NetBIOS datagrams.

NetBIOS and NetBEUI are separate but related technologies. NetBEUI extends NetBIOS with additional networking capabilities.

Also Known As: Network Basic Input/Output System

WINS - Windows Internet Naming Service

Definition: The Windows Internet Naming Service (WINS) supports name resolution, the automated conversion of computer names to network addresses, for Windows networks. Specifically, WINS converts NetBIOS names to IP addresses on a LAN or WAN.

Like DNS, the Windows Internet Naming Service employs a distributed client/server system to maintain the mapping of computer names to addresses. Windows clients can be configured to use primary and secondary WINS servers that dynamically update name/address pairings as computers join and leave the network. The dynamic behavior of WINS means that it also supports networks using DHCP.

Also Known As: Windows Internet Naming Service

workgroup

Definition: In computer networking, a workgroup is a collection of computers on a local area network (LAN) that share common resources and responsibilities. Workgroups provide easy sharing of files, printers and other network resources. Being a peer-to-peer (P2P) network design, each workgroup computer may both share and access resources if configured to do so.

The Microsoft Windows family of operating systems supports assigning of computers to named workgroups. Macintosh networks offer a similiar capability through the use of AppleTalk zones. The Open Source software package Samba allows Unix and Linux systems to join existing Windows workgroups.

Workgroups are designed for small LANs in homes, schools, and small businesses. A Windows Workgroup, for example, functions best with 15 or fewer computers. As the number of computers in a workgroup grows, workgroup LANs eventually become too difficult to administer and should be replaced with alternative solutions like domains or other client/server approaches.

P2P

Definition: The term P2P refers to "peer-to-peer" networking. A peer-to-peer network allows computer hardware and software to function without the need for special server devices. P2P is an alternative to client-server network design.

P2P is a popular technology for file sharing software applications like Kazaa, WinMX and Overnet. P2P technology helps the P2P client applications upload and download files over the P2P network services.

P2P technology can also be found in other places. Microsoft Windows XP (starting with Service Pack 1), for example, contains a component called "Windows Peer-to-Peer Networking." P2P is especially popular in homes where an expensive, decidated server computer is neither necessary nor practical.

Finally, the P2P acronym has acquired a non-technical meaning as well. Some people have described this second meaning of "P2P" as "people-to-people." From this perspective, P2P is a model for developing software and growing businesses that help individuals on the Internet meet each other and share common interests. So-called social networking technology is an example of this concept.

SMB

Definition: SMB is a network file sharing protocol. Communication over SMB occurs mainly through a series of client requests and server responses. SMB client and server software exists within nearly all versions of Microsoft Windows. File sharing systems using SMB, such as LAN Manager for UNIX, have also been produced for many non-Windows operating environments

SMB runs at a higher level on top of other network protocols such as TCP/IP, NetBEUI, or IPX. A new version of SMB, Common Internet File System or CIFS, has been developed by Microsoft for "open" use on the Internet.

Also Known As: Server Message Block, Session Message Block, CIFS

Samba

Definition: Samba is a client/server system that implements network resource sharing for Linux and other UNIX computers. With Samba, UNIX files and printers can be shared with Windows clients and vice versa. Samba supports the Session Message Block (SMB) protocol. Nearly all Windows computers include SMB support with their internal network subsystems (NetBIOS in particular).

With an appropriately-configured Samba server on Linux, Windows clients can map drives to the Linux filesystems. Likewise, the Samba client on UNIX can connect to Windows shares by their UNC name. Although differences among various operating systems (such as filesystem naming conventions, end-of-line conventions, and authentication) can limit interoperability, Samba offers a generally serviceable mechanism for resource sharing on a heterogenous network.

Also Known As: NetBIOS for UNIX

sniffer

Definition: Sniffers monitor network data. A sniffer can be a self-contained software program or a hardware device with the appropriate software or firmware programming. Sniffers usually act as network probes or "snoops." They examine network traffic, making a copy of the data without redirecting or altering it. Some sniffers work only with TCP/IP packets, but the more sophisticated tools can work with many other protocols and at lower levels including Ethernet frames.

Years ago, sniffers were tools used exclusively by network engineers. Today, however, these utilities have become popular on the Internet with hackers and the merely curious. The U.S. Federal Bureau of Investigation (FBI) has utilized a famous sniffer system called "Carnivore" to help detect illegal Internet communications.

Also Known As: network monitor

UNC

Definition: UNC provides a naming convention for identifying network resources. UNC names consist of three parts, a server name, a share name, and an optional file path, that are combined using backslashes as follows

\\server\share\file_path

The server portion of a UNC path refers to names maintained by a network naming service such as DNS or WINS. Share names can be defined by a system administrator or, in some cases, exist automatically within the local operating system.

For example, in Windows 2000 and earlier versions of Windows, the built-in share name admin$ refers to the root directory of the operating system installation (usually C:\WINNT or C:\WINDOWS). (Predefined share names in Windows generally end with a $, but this convention is not required for any new shares an administrator defines.)

Using Windows Explorer or the DOS command prompt, a person can map to the \\computer-name\admin$ UNC share and (with proper security credentials) can remotely access the directory tree under C:\WINNT or equivalent on that computer.

A person can also connect to subdirectories beneath admin$ by specifying the optional portion of the UNC name. For example, \\computer-name\admin$\system32 is the UNC name referring to C:\WINNT\system32 or equivalent on that computer.

UNC notation is used primarily for mapping network drives in the Microsoft Windows family of operating systems, although support for UNC appears in related technologies like Samba. UNC names are most commonly used to reach file servers or printers on a LAN.

Also Known As: Universal Naming Convention, Uniform Naming Convention

REFERENCE:ABOUT.COM