LAN/WAN
LAN-based Internet connectivity can be established in various ways. If it is a small organization, you can use a dial-up connection and then distribute the Internet connectivity among multiple computers. When you need to configure Internet connectivity for a LAN, typically a computer or device is configured to act as a gateway.
The primary task of a gateway is to perform routing between networked computers and the Internet. A gateway is simply responsible for sending and receiving data packets. You can also configure dedicated connections such as ISDN, DSL, or cable-based Internet connectivity for WAN connections.
ISDN
ISDN is a digital architecture that defines hardware and call-setup schemes for end-to-end connectivity. This technology can carry video, voice, and data for transmission to the specified destination. ISDN uses two separate channels for in-band and out-of-band signaling.
ISDN lines have a faster call setup than LANs because both channels are separate. A dedicated D channel is used for out-of-band signaling. Compared to normal telephone lines, which use the same channel for in-band and out-of-band signals, ISDN is faster.
The three different types of ISDN services are:
Primary Rate Interface (PRI) — Consists of 23 B channels and one D channel (64 Kbps) in North America and Japan for a total bandwidth that is equivalent to one T1 leased line, or 30 B channels and one D channel in Europe, Australia and most of the rest of the world with the slightly higher capacity E1.
Basic Rate Interface (BRI) — Consists of two B channels which provide a data transfer speed of 64 Kbps and one D channel which provides the data transfer speed of 16 Kbps.
Broadband ISDN — Offers transfer rates of up to 633 Mbps and uses coaxial or fiber-optic cables.
Broadband Technologies
Broadband provides high-speed connectivity over the internet. Technologies such as Digital Subscriber Line (DSL), cable, and satellite provide high-speed Internet connectivity. To learn more about each broadband technology, click the bullet points.
DSL
Cable
Satellite
DSL
DSL describes the broad category of Internet access technologies that use telephone wire to transmit signals to and from the Internet. There are several variants of DSL available in the market. Asynchronous DSL is capable of downstream transfers of 8 Mbps and upstream transfers of 1 Mbps.
The other forms of DSL provide speeds from 144 Kbps to 1.5 Mbps downstream and 128 Kbps to 512 Kbps upstream.
DSL connections use standard RJ-11 connectors between the modem and the ISP. An advantage of DSL is that the existing UTP telephone cables can be used to connect the DSL modem to an RJ-11 wall socket.
Cable
Cable modem-based Internet connections always use standard coaxial cable to establish a direct connection to the Internet. A cable modem connects to a computer by using an RJ-45 Ethernet cable or a USB cable.
Satellite
Satellite technology can cover large geographic areas because no cables are required for its implementation. The disadvantage of satellite technology is that it is slower than cable, ISDN, or DSL. The satellites and receiving dishes need to be aligned, or the signal will be noisy and weak. A common problem with satellite communication is delay. Signals take time to reach and then return from the satellite. This delay is known as latency. Bad weather also affects communications using satellite technology.
There are two types of satellite-based connections: one-way and two-way. One-way uses a dial-up modem and an ISP. In a one-way connection the computer connects to an Indoor Receive Unit (IRU), which connects through a coaxial cable to the satellite dish. A two-way uses two satellites to send and receive information. In a two-way connection, an Indoor Transmit Unit (ITU) is used along with an IRU. A coaxial cable can be used with the IRU, ITU, and satellite dishes.
Dial-Up Access
Dial-up access uses the telephone system to allow communication between computers. Dial-up networking uses analog modems that convert the parallel digital signals generated by a computer into serial analog signals suitable for transmission over telephone wires. Dial-up connections can transmit data at speeds up to 56.6 Kbps.
For dial-up networking, you can use either an internal or external modem. An internal modem is installed inside the computer's system case in an expansion slot on the motherboard. It's equipped with its own interfacing circuitry. An external modem is installed outside the computer. It connects to a serial port of the computer using an RS-232 cable. An external modem uses the interfacing circuitry of the serial port.
Wireless
Wireless devices connect to the Internet through an access point. Wireless-based Internet connectivity is used in hotels, airports, or restaurants where customers can use the access points to connect to the Internet. This type of Internet connectivity is often a paid service.
There are several wireless specifications:
The 802.11a wireless standard supports a maximum speed of 54 Mbps at a frequency of 5 GHz.
The 802.11b wireless standard supports a maximum speed of 11 Mbps at a frequency of 2.4 GHz.
The 802.11g wireless standard supports a maximum speed of 54 Mbps at a frequency of 2.4 GHz. The 802.11g standard is compatible with the 802.11b standard, ensuring backward compatibility. 802.11g access points can work with 802.11b wireless network adapters and vice-versa.
The Bluetooth wireless standard supports a maximum speed of 400 Kbps at a frequency of 2.4 GHz.
Bluetooth
Bluetooth, defined by the IEEE as standard 802.15, is a wireless network protocol intended to provide convergence between wireless-enabled devices such as computers, printers, keyboards, mice, cellular telephones, and PDAs. Bluetooth is the best wireless communication technology to communicate with multiple devices.
Bluetooth wireless range depends on the class of the Bluetooth device:
Class I: provides communication with a maximum distance of 100 meters.
Class II: provides communication with a maximum distance of 10 meters.
Class III: provides communication at short distance and is rarely used today.
Infrared
Infrared technology is a wireless technology used to send and receive information by using electromagnetic radiation in the infrared band. Infrared provides relatively short-range communication up to 12 feet with a data transfer rate of less than 4 Mbps.
Infrared is the cheapest wireless technology. Modern laptops come with built-in support for infrared. The Infrared Data Association (IrDA) is the authority that defines protocol standards and specifications for short-range communication using infrared light.
Cellular
Cellular technology is a radio technology made up of many cells. A transmitter is used to serve these cells, which provide radio coverage over a wide area. Several types of cellular technology can be used, such as Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA).
CDMA technology uses wide frequency channels to send messages that are decoded at the receiving end. TDMA technology divides time slots among different users so they can share the same radio frequency.
General Packet Radio Service
General Packet Radio Service (GPRS) is a wireless technology used in mobile devices to transfer data. GPRS technology operates at a speed of 115 Kbps. This technology is useful for sending and receiving e-mail and for browsing the Web.
VoIP
Voice over IP (VoIP) technology is used to carry voice signals over IP telephony. This technology allows you to make voice calls through a broadband Internet connection. VoIP calls costs less than calls made through the Public Switched Telephone Network (PSTN), but VoIP voice quality is reduced.
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