Before we discuss networking protocols and hardware, let's examine a few critical concepts.
Addressing
Bandwidth
Status Indicators
Full- and Half-Duplex
Addressing
Addressing is the assignment of IP addresses to hosts on a network. There are two categories of IP addresses: public and private.
An Internet Service Provider (ISP) provides public IP addresses used over the Internet. You have to purchase public IP addresses from an ISP.
Private IP addresses are available free of charge and are used on a LAN. You cannot use private IP addresses over the Internet.
Bandwidth
Bandwidth is the rate at which information travels from one location to another over a channel. Bandwidth is typically measured in Megabits per second (Mbps), Kilobits per second (Kbps), or bits per second (bps).
The amount of information that can be sent at any time depends on the available bandwidth at that time — the higher the bandwidth, the greater the amount of information that can be passed from one location to another.
Status Indicators
Status indicators are used to determine whether a network device such as a Network Interface Card (NIC) or a switch is working properly. You can diagnose network device problems with status indicators.
A NIC has two indicator lights: a link indicator and an activity indicator that provide information on the status of the link and on network activity, respectively. A switch has indicator lights that show whether the device is working properly.
Full- and Half-Duplex
A full-duplex connection can send and receive data over two separate circuits at the same time. A half-duplex connection has a single circuit; it can either send data or receive data, but cannot perform both actions at the same time.
If an application requires two-way communication, you should use a full-duplex connection. A full-duplex connection will let the application perform more efficiently.
Network Architectures
Network architecture is a collective term that denotes a collection of protocols, topologies, and access methods. Examples of network architectures include the Ethernet and Token Ring topologies. The pages that follow provide more detail about these architectures.
Ethernet
Ethernet is a group of standards used in a LAN. The naming standard is the same for different Ethernet types. The first number of each standard indicates the transmission speed in Mbps, the middle section indicates the signaling type, and the last section indicates the transmission medium.
For example, in a 100BaseTX model, the "100" indicates that the network can transmit data at 100 Mbps. "Base" indicates that the network uses the baseband transmission method — meaning only one signal is sent over the network medium at a time. "TX" indicates that a twisted-pair cable is used as the network medium. T can also indicate twisted-pair cable, and F, FL, FX, LX, and SX indicate fiber optic cable. In the Ethernet standards 10Base2 and 10Base5, the "2" indicates thinnet coaxial cable and "5" indicates thicknet coaxial cable.
Standard Ethernet implementations include 10Base2, 10Base5, 10BaseT, and 10BaseF. Fast Ethernet runs at a maximum of 100 Mbps; its implementations include 100BaseT, 100BaseTX, and 100BaseFX. Gigabit Ethernet runs at a maximum of 1000 Mbps; its implementations include 1000BaseT, 1000BaseCX, and 1000BaseFX.
Token Ring
Token Ring networks can be of Type 1 or Type 3. Type 1 networks normally use STP cables and operate at 4 or 16 Mbps. Type 3 networks use UTP cables; they also operate at 4 or 16 Mbps.
Network Protocols
A network is an interconnection of computers that use the same or different network protocols. A protocol is a set of rules that determine how computers communicate over a network. Protocols are grouped according to their functions.
Some commonly-used protocols include:
TCP/IP
NWLINK IPX/SPX (Internetwork Packet Exchange/Sequence Packet Exchange)
NETBEUI/NetBIOS (NetBIOS Extended User Interface/Network Basic Input/Output System)
TCP/IP
TCP/IP is a standard set of rules used for communication in large networks. TCP/IP is managed through two different hierarchical structures. First is the IP address hierarchy, which uniquely identifies a host such as a computer, printer, or router in a network. Second is the TCP hierarchy, a transport-level protocol responsible for providing reliable data delivery over the network.
TCP/IP is included with Windows 9x, Windows ME, Windows NT, Windows 2000, and Windows XP. Communication over the Internet requires TCP/IP.
Three major fields have to be configured for TCP/IP: the IP address, the subnet mask, and the default gateway. These are described on the pages that follow.
IP Addresses
An IP address is a 32-bit number that is a combination of four 8-bit numbers known as octets. This 32-bit number is in the abc.abc.abc.abc format, where abc is a decimal number in the range of 0 to 255. An example of an IP address is 202.10.100.1.
A network administrator can assign an IP address manually, or a computer can be configured to attain its IP address automatically from a server on the network by using the Dynamic Host Configuration Protocol (DHCP).
Subnet Masks
The subnet mask divides a large TCP/IP network into smaller networks. A subnet defines all computers that have a common network prefix. IP addresses have a network section that identifies the network to which the computer belongs and a node section that identifies the network address of the computer. A network can be categorized into classes, with each class being allowed to use a defined set of IP addresses. To learn more about each class, click the bullet points.
Class A
Class A uses IP addresses ranging from 1.0.0.0 to 126.255.255.255. The first octet, 1 to 126, identifies the network as a Class A network. The rest of the address identifies the host on the network.
Class A networks can have a maximum of 126 networks, and each network can have 16,777,214 hosts, by using the default subnet mask 255.0.0.0.
Class B
Class B uses IP addresses ranging from 128.0.0.0 to 191.255.255.255. The first two octets, 128.0 to 191.255, identify the network as a Class B network. The rest of the address identifies the host on the network.
Class B networks can have a maximum of 65,534 networks, and each network can have 65,534 hosts, by using the default subnet mask of 255.255.0.0.
Class C
Class C uses IP addresses ranging from 192.0.0.0 to 223.255.255.255. The first three octets, 192.255.0 to 223.255.255, identify the network as a Class C network. The rest of the address identifies the host on the network.
Class C networks can have a maximum of 2,097,152 networks, and each network can have 254 hosts, by using the default subnet mask of 255.255.255.0.
Default Gateways
The default gateway specifies the address of the router to which the host sends all TCP/IP traffic. It also helps send TCP/IP traffic from a source computer to a target computer on a different subnet. Every computer connected in a network has the same default gateway address.
If a network consists of more than one subnet, data can still be sent to a target computer in a different subnet by using a default gateway address. The address of the default gateway is also required if the computer is connected to the Internet.
NWLINK IPX/SPX
IPX/SPX is the protocol used on Novell NetWare networks. To support the IPX/SPX protocol, Microsoft created its own version, known as NWLINK. IPX/SPX requires a network number and a frame type setting if possible.
The network number is an 8-digit alphanumeric number that uniquely identifies a network segment of the IPX/SPX network and enables IPX Internetwork routing.
The frame type is usually autodetected. If not detected, the frame type defaults to IEEE 802.2. IPX/SPX is included with Windows 9x, Windows ME, Windows NT, Windows 2000, and Windows XP.
NetBEUI/NetBIOS
NetBEUI is a modified version of the Network Basic Input/Output System (NetBIOS) developed by Microsoft for Windows networking. The NetBIOS protocol is a name resolution protocol that searches for computers on a LAN by computer name. It is used mostly in Ethernet and token ring networks.
NetBIOS sends a request as a network control block, which contains information such as the request location and the name of the destination host. NetBIOS works in two modes:
Session mode allows a connection between two computers, transfer of large messages, and error detection and recovery.
Datagram mode allows the broadcast of messages on the entire LAN.
NetBEUI is the default protocol for Windows 9x. It's a simple protocol for creating a small network in a small amount of time, because it requires little configuration. NetBEUI/NetBIOS is included with Windows 9x, Windows ME, Windows NT, Windows 2000, and Windows XP.
Networking Models
Whenever there's a need for connecting two or more computers, you require a network. The selected networking model may differ based on your requirements and the number of computers you want to install on the network. There are two basic networking models: peer-to-peer and client/server. To learn more about each model, click the bullet points.
Peer-to-peer
A network that has no dedicated servers, where individual workstations can share data or services with other workstations, is known as a peer-to-peer network. In a peer-to-peer network each computer can function as a client or a server. All computers are considered equal in functionality, and there is no central server controlling the access of resources.
Peer-to-peer networks are effective when the total number of participating workstations doesn't exceed 20. As the network grows beyond this size issues such as security, administration, and data backups tend to become problems. A peer-to-peer network architecture is more suitable for small businesses where security isn't a concern.
Client/server
The client/server model uses a network operating system to manage the network and act as a central authority for network resources. In a client/server network, there's at least one centralized server running the network operating system that allows network administrators to control the network. A client or workstation can make requests to the server for resources, and the server can fulfill or reject those requests. This provides a secure and organized network.
Windows NT, Windows 2000, and Windows 2003 networks are client/server networks. Windows 2000 and 2003 use domains to provide centralized control of security.
Network Cables
Cables connect two network devices and transfer information between them. Coaxial, twisted pair, fiber optic, and Plenum/PVC cables connect network devices on a LAN.
You can use an RS-232 serial cable, Universal Serial Bus (USB) cable, or an IEEE 1394/FireWire cable to connect two computers directly. An external modem connects to the serial port of a computer with an RS-232 cable.
USB and IEEE 1394/FireWire cables provide serial data transfers. A USB cable has only one pair of wires for data transfer; it provides half-duplex data transmission. RS-232, USB, and IEEE 1394/FireWire cables allow a serial port on one computer to be connected directly to another computer with a null-modem cable, which is a cable with specific pin contacts reversed.
You'll need an adapter to perform the pin reversal required for a direct connection. When one of these adapters is used, it is possible to connect two computers through their serial ports using a standard serial cable without reversing any pin contacts in the cable.
Coaxial Cable
Coaxial cable was the most commonly used cable type in early computer networks. In modern networks coaxial cable has been replaced by UTP, STP, fiber optic, and wireless media.
Coaxial cable is half-duplex; it supports a transmission rate of 10 Mbps, which is considered slow compared to other cable types.
Unshielded Twisted Pair Cable
Unshielded Twisted Pair (UTP) cables consist of four pairs of wires with no foil shield. Examples of UTP cables are:
CAT3 T is used in 10BaseT networks; it supports transmission speeds up to 10 Mbps.
CAT5 supports transmission speeds up to 100 Mbps, but it has been phased out in favor of Category 5e. It also provides backward-compatibility to the older and much slower 10 Mbps standards.
CAT6 supports transmission speeds up to 1000 Mbps. While Category 5e also supports speeds of up to 1000 Mbps, Category 6 is recommended for best results. It also provides backward-compatibility to the older and much slower 10 Mbps standards.
Shielded Twisted Pair Cable
Shielded Twisted Pair (STP) cables consist of four pairs of insulated wires with a foil shield wrapped around the wires. STP cable is identical to UTP except for the shielding.
The metallic shield protects the cable from interference caused by fluorescent light fixtures, motors, and other electromagnetic interference (EMI) sources. STP cables can be used in any implementation where UTP cables are used, but are more expensive than UTP. STP is generally preferred only when shielding from EMI is required.
Fiber Optic Cable
Fiber optic cable can be used with Ethernet networks. It carries digital data and voice signals in the form of modulated pulses of light. There are two types of fiber optic cable:
Single Mode fiber optic cable has a thin core-diameter of 5 or 10 microns. It uses a laser to transmit one signal at a time. Practical transmission distances for single-mode fiber optic range up to 50 km.
Multi Mode fiber optic cable has a core-diameter of 50, 62.5, or 100 microns. It transmits multiple signals using a light-emitting diode (LED). Practical transmission distances for multi-mode fiber optic range up to 3,000 km.
Fiber Distributed Data Interface (FDDI) refers to fiber optic cable used in Token Ring networks.
Plenum/Polyvinyl Chloride Cable
Because it does not produce toxic fumes when it burns, Plenum/Polyvinyl Chloride (PVC) cable is used in plenum (air-filled) spaces in buildings, such as ventilation ducts. Non-plenum cables are covered with PVC that produces toxic gas when it burns. Most fire codes require plenum-rated cable in any area that carries breathable air.
Network Connectors
Each type of cable requires a specific type of connector for termination. To learn more about each type of connector, click the bullet points.
Standard connectors (SC) and Straight Tip (ST) connectors
Lucent Connector (LC) connectors
Mechanical Transfer-Registered Jack (MT-RJ) connectors
Registered Jack-11 (RJ-11) connectors
Registered Jack-45 (RJ-45) connectors
USB and IEEE1394/FireWire connectors
Standard connectors (SC) and Straight Tip (ST) connectors
Fiber optic NICs usually include an ST or SC connector. ST fiber uses a round-plug style connector, while SC fiber uses a square-block style connector. Fiber optic cable is commercially available either with the same connector at both ends or with an ST connector at one end and an SC connector at the other end.
Lucent Connector (LC) connectors
LC connectors are used with single-mode and multi-mode fiber optic cables. LC connectors use a plastic housing; they provide precise alignment through ceramic ferrules. LC connectors have a locking tab.
Mechanical Transfer-Registered Jack (MT-RJ) connectors
MT-RJ connectors are used with single-mode and multi-mode fiber optic cables. MT-RJ connectors use a plastic housing; they provide precise alignment through metal pins and plastic ferrules. MT-RJ connectors are cheaper than SC and ST connectors, and they support full-duplex communication.
Registered Jack-11 (RJ-11) connectors
RJ-11 connectors are the standard connector for telephone connections. An RJ-11 connector has four wires. It's used to create a connection between telephone-line jacks and analog modems.
Registered Jack-45 (RJ-45) connectors
RJ-45 connectors are similar to RJ-11 connectors but larger. An RJ-45 connector connects both UTP and STP cables to hubs, NICs, and various other twisted-pair networking devices. An RJ-45 connector has eight wires in four pairs. A UTP cable typically has a male RJ-45 connector on each end. These plug into female connectors built into networking devices.
USB and IEEE1394/FireWire connectors
These interfaces support instant networking. Instant networking allows two Windows XP computers to communicate simply by using a FireWire cable and the TCP/IP protocol stack. FireWire supports an end-to-end throughput of over 50 Mbps.
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