Networking with Windows

Networking Technologies Comparing Cable, DSL, and ISDN

More users are connecting to the Internet and other networks using something other than a LAN or a dialup modem connection. The general availability of high-speed broadband services has allowed many users to move away from dialup connections to an always-on, dedicated connectivity technology. The three most popular alternatives to dialup connectivity are Digital Subscriber Line (DSL), Integrated Services Digital Network (ISDN), and cable.

The common thread among these three services is that they are all transmitted across analog systems. DSL and ISDN transmit digital data across the analog POTS (Plain Old Telephone Service) lines of the telephone company. Cable transmits its digital data across a coaxial cable system, which is primarily used to carry analog (and now some digital) television signals. The processes of installing and configuring the hardware is similar for all three types of broadband services, except for the type of hardware that is used in the connection. All of these services are, in effect, providing a LAN connection as far as the PC is concerned.

The one unique step that is common to each of these connectivity technologies and their hardware — DSL, ISDN, and cable — is the need to install the proper device driver on the PC to facilitate the communications between the service's interface and the PC. Whether the interface device is a DSL modem, an ISDN terminal adapter, or a cable modem, this device is what the PC's NIC is connected to for its network connection.

Broadband Hardware

The data speeds and types of hardware that are used to interface the broadband carrier lines to a home or office PC are listed here.

DSL/ISDN/Cable Connectivity Technologies Service

Hardware Device

Cable

Modem

Asymmetrical DSL (ADSL)

Modem or bridge

Symmetrical DSL (SDSL)

Bridge or router

Basic-Rate ISDN (BRI)

Network terminators or terminal adapters

2

Symmetrical versus Asymmetrical DSL It's not a big deal for the A+ exams, but in case you're wondering, some differences exist between the two primary flavors of DSL. Symmetrical DSL gets its name from the fact that the same data speed is used to transmit and receive. In other words, the same speed is used to upload and to download, making this service very fast.

Asymmetrical DSL refers to the fact that this type of DSL uses different data speeds to upload and download. For example, a common service of ADSL is about 128 kilobits per second (Kbps) for upload and 384 to 512 Kbps for download. Anytime that you see DSL referred to generically (such as DSL or xDSL), the reference is typically to ADSL.

Working without a Wire In addition to the connectivity technologies that are discussed in the preceding section, you should know about two more connectivity technologies for the A+ OS Technologies exam: wireless networking and satellite Internet access. Of the two technologies, we would recommend being more knowledgeable about wireless networking, at least for the time being. You don't need to be an expert at either for the current exam version. However, this is likely to change in the future.

Networking with Windows

3 The most common standards used for networking PCs are the WiFi standards. With all of the wireless and satellite technologies, it is the hardware that interfaces the PC to the network that is different — not the entries in the PC's network configuration. They all use expansion card NICs (wireless NICs with a small antennae on the back of the PC) or PC card-type network adapters that interface to wireless hubs and network access points (NAPs).

Beaming It down from Above For those who live miles from the nearest telephone connection or ISP and have some southerly exposure, an alternative to wire-based or short-range wireless services is satellite Internet access. Companies such as StarBand (Dish Network, www.starband.com) and SatCast (DirectTV, www.direcpc.com) offer a two-way satellite link to the Internet. This service connects to a PC through a USB port and is configured just like a LAN connection.

Automatically Assigning IP Addresses IP addresses are comprised of four sets of numbers, and each set is separated by a period. An IP address is 32 bits long, and each of the 4 numbers is 8 bits long. The highest possible IP address is 255.255.255.255, because the highest value that can be represented in 8 bits is 255. Each of the four 8-bit numbers is called an octet, which means a set of 8. The portions of an IP address are referred to as the first, second, third, and fourth octets.

An IP address can be assigned as a static IP address (a fixed PC location) or as a dynamic IP address (changeable). A static IP address is permanently assigned to a node when it is added to the network. Static IP addresses work as long as the network doesn't move, the NIC is not interchanged with other PCs, and the network is never reconfigured.

Networking with Windows

4 Because most networks change (and they change fairly frequently), it's good practice to assign IP addresses dynamically. Each PC that is attached to the network and is configured to obtain an IP address automatically requests and is assigned an IP address to use for a specific length of time by a Dynamic Host Configuration Protocol (DHCP) server. Beginning with Windows 95, all versions of Windows include a DHCP client.

Using APIPA On occasion, a network PC boots up and finds that the DHCP server is not available. When this happens, the PC continues to poll for a DHCP server using different wait periods. The Automatic Private IP Addressing (APIPA) service allows the DHCP client to automatically configure itself until the DHCP server is available and the client can be configured to the network. APIPA allows the DHCP client to assign itself an IP address in the range of 169.254.0.1 to 169.254.254.254 and a Class B subnet mask of 255.255.0.0. The address range that is used by APIPA is a Class B address that Microsoft has set aside for this purpose.

Speaking Foreign Network Languages When configuring a network PC, another consideration is what client interfaces must be installed to allow the PC to communicate with all resources on the network. For example, if Apple Computer or NetWare servers are on the network, the PC must have the applicable clients and linkware to be able to interact with them.

Appletalk was officially deprecated as of Macintosh OS 9. The Macintosh Open Transport and Rendezvous protocols are now used instead.

You need to know the following network terms for the Networking Environment.

AppleTalk: This is Apple Computer's proprietary network protocol suite. IPX/SPX: This is a Novell NetWare proprietary protocol suite that is used as the native network operating system prior to Version 5 of NetWare, which uses TCP/IP as its native protocol. NetBEUI/NetBIOS: The NetBIOS Extended User Interface (NetBEUI — pronounced "net booey") is an enhanced version of the NetBIOS network operating system. NetBEUI is still used by many manufacturers as a network operating system on local networks that don't connect to the Internet.

Networking with Windows