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network administration
Networking Basics: Networking Overview A network is two or more computers that have been connected for the purposes of exchanging data and sharing resources.

After completing this lesson, you should be able to: Define basic networking terms, Identify top-level Internet domain names, Identify server types. Many types of computer networks exist, but you need only be concerned with the following:

Peer-to-peer network: This type of network includes two or more PCs that are connected to share data files, a printer, or other resources.

Local area network (LAN): A small business or corporate department may install a LAN that interconnects from two to hundreds of PCs, using permanently installed cabling or perhaps a wireless technology. Wide-area network (WAN): A corporation may maintain a WAN using dialup, leased, or other dedicated communication means. You should also be familiar with the following network terminology and characteristics:

Topology: The geometric arrangement of any network is its topology. The most common topologies are the bus, star, and ring topologies. Protocol: To operate efficiently, any communications-based system must have an established set of rules — its protocol — to govern its operation. Popular protocols for LANs are TCP/IP and IPX/SPX Data packets: Data, messages, and tokens that are transmitted on any network must conform to the size and format prescribed under the network's protocol. Data packets also vary between network operating systems (NOSs) on the same protocol. Architecture: A network can be classified as being either a peer-to-peer or a client/server architecture. When all nodes on a network are equal and resources are shared equally, the network is a true peer-to-peer network. When one computer is designated to host programs or files for the rest of the network, it is a server, and the other nodes are clients. Media: Nodes on a network are connected by twisted-pair copper wire, coaxial cable, fiber-optic cable, or wireless radio wave connections. Server: This is a network computer from which workstations (clients) access and share files, printers, communications, and other services. Servers can be dedicated to a single service, such as file servers, print servers, application servers, Web servers, and so on. Servers can also be the software that performs, controls, or coordinates a service or resource. Node: This is any addressable network point, including workstations, peripherals, or other network devices. The term node is commonly used interchangeably with workstation.

Workstation: This is a personal computer that runs application or utility software and uses data that is stored locally or provided by a network server to which it is connected by a cable or media. Workstations are also known as clients. The Network's Domains A domain has several different uses. The three common uses of domains in networking are the following: Windows NT/2000/XP domain: A logical group of computers with centralized security and administration. Internet domain: An element of the Domain Name Server (DNS) naming hierarchy. NetWare domain: The memory segment within NetWare that is used to separate NetWare Loadable Modules (NLMs) from the operating system.

Internet Domains The highest level of generalized domains defined by DNS is standardized to group domain names by their organization type or geographical location. The generic top-level domains (gTLDs) that are used on the Internet are listed here.

Network Domains Servers and workstations are classified into domains by the role that they play on the network. Network domains, domain controllers, and the names of the resources in a domain are important things to know for the exam.

In the context of a Windows NT Server, Windows 2000 Server, or a Windows Server 2003 network, a domain is a collection of hardware and software resources and the user accounts that have access to them. The resources may include multiple servers, printers, CD-ROM drives, RAIDs, and other devices that are attached to the network. Several types of servers can exist on a network, each one performing a different task for the network and its workstations. A server is usually thought of as a computer, but a server is actually the software that performs, controls, or coordinates a service or resource. One computer can physically house many different software servers. To network clients, each server can appear to be a completely separate device, when that is not usually the case. The table below lists the most common types of servers that are implemented on a network.

Networking Devices A Network Devices Primer The A+ Hardware Technology exam focuses on the hardware that is used to connect a PC to a network, which boils down to the network interface card (NIC) and the cabling to which it attaches. However, other hardware devices are used on a network to improve the network's performance or to provide an interface between different types of networks, and you should at least review these for background.

Cabling the Network

For one computer to carry on a conversation with another computer, both computers must be able to transmit and receive electrical impulses that represent commands or data. The computers and peripherals of a network are interconnected with a transmission medium to enable data exchange and resource sharing. Cable media has laid the foundation on which networks grew — literally. The following types of cabling are used on most networks:

Coaxial (coax): This is similar to the cable that is used to connect your TV set to the cable television service. Two types of coaxial cable are used on networks: thick coaxial cable (commonly called 10Base5, ThickWire, or ThickNet) and thin coaxial cable (10Base2, ThinWire, or ThinNet). Fiber-optic: With this cable, glass or polymer fibers carry modulated pulses of light to represent digital data signals. Although a few different types of polymer cables exist, you care about only one specific kind: fiber-optic. Fiber-optic cable is also known as 10BaseF or 100BaseF cable. Passing around the Signals These devices play a key role in the performance of the network. You don't need to memorize them, but you should understand how they're used:

Repeater: This electronic echo machine has no function other than to retransmit whatever it hears, literally in one ear and out the other. A repeater is used to extend the signal distance of the cable by regenerating the signal.

Hub: This device is used to connect workstations and peripheral devices to the network. Each workstation or device is plugged in to one of the hub's ports. A hub receives a signal from one port and passes the signal on to all of its other ports and therefore to the device or workstation that's attached to the port. For example, if an 8-port hub receives a signal on port 4, the hub immediately passes the signal to ports 1, 2, 3, 5, 6, 7, and 8. Hubs are common to Ethernet networks.

Bridge: Bridges are used to connect two different LANs or two similar network segments, to make them operate as though they were one network. The bridge builds a bridging table of physical device addresses that is used to determine the correct bridging or MAC (Media Access Control) destination for a message. Because a bridge sends messages only to the part of the network on which the destination node exists, the overall effect of a bridge on a network is reduced network traffic and fewer message bottlenecks.

Router: This device sends data across networks using the logical or network address of a message to determine the path that the data should take to arrive at its destination.

Switch: A switch is a device that segments a network. The primary difference between a hub and a switch is that a switch does not broadcast an incoming message to all ports, but instead sends the message out only to the port on which the addressee workstation exists based on a MAC table that is created by listening to the nodes on the network. Gateway: This is a combination of hardware and software that enables two networks with different protocols to communicate with one another. A gateway is usually a dedicated server on a network, because it typically requires large amounts of system resources. The following types of gateways exist:

Address gateway: Connects networks with different directory structures and file-management techniques. Protocol gateway: Connects networks that use different protocols. This is the most common type of gateway. Format gateway: Connects networks that use different data format schemes, for example, one that uses the American Standard Code for Information Interchange (ASCII) and another that uses Extended Binary-Coded Decimal Interchange Code (EBCDIC, an IBM propriety alternative).

Network Interface Card The Network Interface Card (NIC) The network interface card (NIC), also known as a network adapter.

The NIC is a physical and logical link for a PC to a network. It is installed inside the computer in an open expansion slot. NICs are available for most of the expansion bus architectures, so getting a card for an available slot is easy. The most commonly used bus for NICs is the PCI (Peripheral Component Interconnect) bus, but many legacy ISA (Industry Standard Architecture) cards are still in use.

The setup that is needed for the NIC is controlled by two factors: the PC itself and the NOS (network operating system, such as Windows NT/2000 or Novell NetWare). If you have the choice, do yourself a big favor and use the same brand and model of NIC in every PC on the network. The NIC is a translator that works between the network and the PC. Networks transmit data in a serial data format (1 bit at a time), and the data bus of the PC moves data in a parallel format (8 bits at a time). The NIC acts as a go-between to convert the signal from serial to parallel format or from parallel to serial format, depending on its direction. The NIC also formats the data as required by the network architecture. The NIC attaches a PC or other networked device to the network cabling and the network system. The primary purposes of the NIC are to serve as a transceiver — a device that transmits and receives data to and from other NICs (installed in the other networked nodes and devices) — and to connect to the network cabling. You should know the NIC characteristics outlined on the following pages. MAC (Media Access Control) address: Each NIC is physically encoded with a unique identifying address that is used to locate it on the network. This address is 48 bits (6 bytes) long. System resources: A NIC is configured to the computer with an IRQ, an I/O address, and a DMA channel. A NIC commonly uses IRQ3, IRQ5, or IRQ10, and an I/O address of 300h. Data bus compatibility: NICs are designed with compatibility to a particular data bus architecture. ISA (Industry Standard Architecture) and PCI (Peripheral Component Interconnect) cards are the most common.

Data speed: The NIC must be compatible with the data speed of the network. The data transfer speeds of a network are determined by several factors, including the cable media, the network topology, and the network connectivity devices that are in use.

For example, a Token Ring network uses STP cable — the workstations attach to the network through MAUs (Multistation Access Units) — and typically runs at either 4 Mbps or 16 Mbps. An Ethernet network uses UTP cable (or coax), attaches its workstations through hubs or switches, and most commonly runs at either 10 Mbps or 100 Mbps.

Many NICs have the ability to sense the data speed in use. A NIC designated as a 10/100 NIC has the ability to autosense between a 10-Mbps and a 100-Mbps network. Newer systems now support data speeds of 1,000 Mbps (or 1 Gbps), and newer NICs now support an autosensing 10/100/1000 port.

Connectors: Several different connectors are used to join NICs to network cabling. The type of connector that is used depends mostly on the type of cable in use.

Coax cabling primarily uses a BNC connector. Fiber-optic cabling is rarely used for cabling to workstations because of its cost. The most commonly used connector for networking is the RJ-45 connector, which is similar to the connector on your telephone, only a little bigger. Some of the ways that you can determine whether a PC is networked are as follows: 1.Look at the back of the PC for a network port with a cable attached to it. If you find one, you have a winner — a networked PC. 2. If a network cable is not attached to the back of the PC, this doesn't mean that the PC is not a networked PC; the customer may have already disconnected the PC from the network. Question the customer to determine whether you are working on a networked PC. 3. If no network cable exists, check to see whether a NIC is installed. No NIC — no network. However, if a NIC is in the PC, you can make other checks to determine whether the PC is networked. 4. If you have access to the hard drive, search it for the telltale signs that the PC has been networked: folders or directories with names like NWCLIENT. Or look in the AUTOEXEC.BAT or CONFIG.SYS files for entries that start networking clients. (This is especially true for Novell software, which places entries in these files.) 5. If you have access to Windows 9x or 2000, use Windows Explorer to look for network drives. They usually have drive designators of E:, F:, or higher.

Working on a Networked PC You should follow these steps before and after repairing or replacing hardware on a networked PC. Action. 1.	Check to see whether the PC is logged on to the network.

Open a drive or folder on a network device. If you can open a file, the PC is logged on. If the drive is not available, the PC may be a node, but it is not logged into the network 2.	If you are working on the hard drive, make a backup of all the files. Especially important is backing up any networking information that's on the hard drive. 3.	Log off the PC as necessary. 4.	Disconnect the network cable from the NIC, and proceed with the repair of the PC. 5.	After the repair is complete, reconnect the network cable, verify that the network files are on the hard drive, and restore them if needed. 6.	Ask the customer to log on to the network to verify that all is well.

Installing and Configuring a NIC Although many manufacturers now include a NIC as a standard device in newer PC configurations, not every PC comes with a NIC installed. This is why the A+ Hardware Technology exam expects you to be able to install and configure a NIC in a PC. A NIC is installed in a PC to connect it to the network, or when a PC's NIC has gone bad. Below are the steps that are used to install a NIC in a PC.

Of course, we assume that you are wearing your ESD protection and that you used the proper steps to disconnect the PC from the network. Action. 1.	If the PC already has a NIC installed — even if it is the same manufacturer and model as the new NIC that you are installing — uninstall the NIC drivers from the operating system.

If the PC doesn't have a NIC installed, you must determine the type of slot that's available for the NIC. On most new PCs, expansion slots are usually available. 2.	If a PCI slot is open, obtain a PCI card. Otherwise, you must use an ISA or EISA (Enhanced ISA) card, depending on the expansion slots that are available. 3.	Before inserting the card in a slot, study the card's documentation to determine whether any physical configuration steps are necessary.

Most PCI cards are Plug and Play compatible but may still require a DIP switch or a jumper to be set. You must do this before installing the card. Be sure to handle the card only by its nonconnecting edges. 4.	Open the case and install the NIC in the appropriate expansion slot. 5.	The remainder of the installation, aside from replacing the case, is performed on the operating system. Hardware Expansion Slots You need to identify these expansion slots by sight on the exam, so take a good look at this figure.

Connecting a Network •Peer to Peer Networking •Server-Based Networking •Understanding Network Topologies

Network Topologies Imagine an aerial view of a network. Picture the network's general shape. The pattern of connections that ties the workstations to the network is its topology. Let's take a look at the topologies you'll encounter on the A+ exams. Ethernet: Sometimes referred to as bus topology, Ethernet uses a full range of network media (using copper or fiber optics) and operates at 10 Mbps, 100 Mbps, or 1000 Mbps (1 Gbps). The 100-Mbps Ethernet is called Fast Ethernet and 1000 Mbps Ethernet is called Gigabit Ethernet. This is the most widely used LAN technology; probably because it is the cheapest and simplest. Ethernet devices connect to either a hub or a switch that.

Star Topology: In a star topology, the computers on the network connect to a centralized connectivity device called a hub or switch. Each computer is connected with twisted-pair cable to a port on the hub. Star LANs also use the same type of wait-and-listen strategy to send data as characterized by the bus topology. Token Ring: Sometimes referred to as ring topology, Token Ring also uses copper and fiber-optic cabling, operates at 4 Mbps to 16 Mbps, and supports about 260 nodes. A Token Ring network operates reliably but can be difficult to troubleshoot. Because IBM is involved with the exams now, look for at least one Token Ring question. FDDI: (Sometimes pronounced as fiddy, but it's usually just spelled out.) FDDI stands for Fiber Distributed Data Interface. An FDDI NIC contains a laser or diode transceiver that converts its digital data into light to be transmitted on a fiber-optic network or back to a digital signal from incoming light impulses for use by the PC. FDDI is a standard of ANSI and the International Organization for Standardization (ISO) for data networks that use Token Ring topology with dual and redundant rings and data speeds of 100 Mbps.

Connecting a Workstation to the Network Each network topology is associated with a network technology or protocol. Ethernet networking is the most common on a bus topology, and Token Ring is the most common on a ring structure.

The network technology in use is important because when you connect a PC to the network for the first time, you need to know the network identity requirements for a new workstation. Addressing the Network The three addressing elements that are used on a network are as follows:

MAC (Media Access Control) address: Every NIC or network adapter is assigned a unique ID called the MAC address by its manufacturer when it is made. This address is burned into the NIC's firmware and cannot be changed. The MAC address is the basis for all network addressing, and all other address types are cross-referenced to it. A MAC address is a 48-bit address that is expressed as 12 hexadecimal digits (a hex digit is comprised of 4 bits).

To display the MAC address (adapter address) of the NIC or NICs installed in a PC, you can use the WINIPCFG command on Windows 9x and Me systems or the IPCONFIG /all command on Windows 98, Me, NT, 2000, and XP systems. The results of IPCONFIG /all on a Windows XP computer are shown here and on subsequent pages.

IP (Internet Protocol) address: Many internal and all external networks use IP addresses to identify nodes on both LANs and WANs. An IP address for a network workstation combines the address of the network and the node into a 32-bit address that is expressed in four 8-bit octets (which means sets of eight). The IPCONFIG command displays the IP addressing information for a workstation on Windows 98 and all later versions. As shown here, the IPCONFIG command displays the IP address that is assigned to the workstation (in this case, 192.168.3.167), the workstation's subnet mask (which is used to differentiate between the network and host portion of an IP address), and the default gateway of the node. To run this command, open a command prompt and enter IPCONFIG on the command line.

Network names: The most common type of network name is computer names, which are also called network names. A network name is the name assigned to a workstation or other networked device and used to identify that node by other network users. For example, it is much easier to find a printer with a network name or MAIN_LASER than trying to remember the printer's MAC or IP address. Commonly, network names are NetBIOS (Network Basis Input/Output System) names. NetBIOS uses unique 15-character names that are periodically broadcast over the network so the names can be cataloged by the Network Neighborhood function. NetBIOS names are the names that show up in Windows Network Neighborhood. In the example shown here, the NetBIOS name of the computer is XPPRO1. DHCP (Dynamic Host Configuration Protocol): This protocol is used to automatically configure a network workstation with its IP address data. Each time that the workstation is logged on to the network, the DHCP server software, running on a network server or router, assigns or renews the IP configuration of the workstation. Typically, the MAC address is used to uniquely identify the workstation, and the IP address is assigned from blocks of IP addresses that have been set aside for use by internal networks. Depending on the network operating system, the IPCONFIG or WINIPCFG command can be used to view, renew, or release DHCP data.

DNS (Domain Name System): DNS is used to resolve (translate) Internet names to their IP address equivalents. For example, when you request www.MyFavoriteBlog.com from your browser's location line, a nearby DNS server (typically at your ISP) converts it to an IP address, such as 12.168.1.100, which is then used to request the data across the Internet. WINS (Windows Internet Naming Service): WINS is Microsoft's network name resolution software that converts NetBIOS names to IP addresses. Windows machines are assigned NetBIOS names, which are converted into IP addresses for use on a network using TCP/IP (Transmission Control Protocol/Internet Protocol), the foundation protocol suite of the Internet. The use of a WINS server allows nodes on one LAN segment to find nodes on other LAN segments by name.

Connecting to an Ethernet Network When a new workstation is added to an Ethernet network, the workstation identifies itself using its MAC address and computer name to the rest of the network. The workstation is also assigned an IP address (either by DHCP or some other means). Devices on the network that need to hold this addressing information, such as a switch or bridge, store the information in their MAC address tables. When requests come in for a particular IP address, the MAC address of the node is looked up and the message is sent to that workstation. This description is highly simplified, but it represents the essence of what happens. Connecting to a Token Ring Network When you add a new node to a Token Ring network, the node must first establish that its address is unique. The workstation sends out test frames with its ID address, and the system responds with its own test frames that are sent to that address. If no other node responds, the new ID address is accepted and established for the new ring node. If a duplication exists (it can happen), jumpers or DIP switches on the NIC can be used to alter the address. Other Protocols

In addition to the three network protocols (Ethernet, Token Ring, and FDDI) described earlier, other protocols can be used to interconnect PCs to other PCs or networks. For the test, you need to know the names of these protocols, their acronyms, and the scope of what they interconnect.