After getting know the router on internet connectivity, there are another Communication technologies that we need to understand was bandwidth.
In analog systems, bandwidth is the difference between the highest-frequency and the lowest-frequency signal components of a transmission channel. Frequency is measured as the number of cycles per second, or Hertz (Hz). In digital systems, bandwidth indicates the data transmission in bits per second (bps), and the standard prefixes are used to indicate values such as a thousand bps (Kbps), a million bps (Mbps) and a billion bps (Gbps).
So bandwidth is a measure of the amount of data that can travel over a communication system in an allotted time frame. It may be referred to as data throughput or line speed. Bandwidth is directly proportional to the rate of communication, meaning that the greater the bandwidth, the faster the communication.
Common communications technologies
There is a wide range of networking technologies in use today. These include cable modems, digital subscriber line (DSL), Integrated Services Digital Network (ISDN), regular telephone lines, satellite connections, and wireless connections.
Cable modem
A cable modem is a modem that allows a PC to access the Internet using a cable television connection. A cable modem is always connected and is an example of a broadband medium. A broadband medium carries multiple types of transmissions. When a PC transmits digital signals, the cable modem converts the digital signals to analog signals, and it converts any incoming analog signals back to digital signals.
Digital subscriber line (DSL)
DSL is a broadband digital technology that uses regular copper phone lines to transmit and receive data. DSL uses different frequencies to those of voice, allowing you to use the same phone line for voice and data transmissions at the same time. DSL is always connected.
Integrated Services Digital Network (ISDN)
ISDN is a broadband technology that uses normal telephone lines or digital telephone lines to send data, video, and voice. Users can access an ISDN via dial-up connections. An ISDN line consists of two channels on a single pair of wires, called B channels, which can separately support speeds up to 64 Kbps. These channels can be combined to give an effective bandwidth of 128 Kbps. An ISDN line also consists of a slower control channel, called the D channel.
Regular telephone lines
Regular telephone lines are a common way to connect to an Internet service provider (ISP), using an internal or external modem that converts digital data to analog data. This modem is necessary as regular telephone lines can only transmit analog data. Typically, such lines offer a maximum possible bandwidth of 56 Kbps, but, on average, the actual value is likely to be half this. This is too slow even for most home users, which is the main reason why technologies such as ISDN are increasingly popular.
Satellite access
Satellite access provides high-speed Internet connections and is useful in remote areas, in which other types of connections aren’t possible. Unlike cable modems and DSL, satellite access is available from almost anywhere. In a typical scenario, a satellite dish – mounted on top of a building – exchanges data with an orbiting satellite, the use of which is offered by an ISP.
Wireless access
Wireless access refers to systems and devices that don’t require cables to communicate with other devices. Wireless access is useful for mobile devices – such as cellular phones – and for Internet access in remote locations, where wired transmission is impossible. Wireless access is not as common as wired data transmission because it can be expensive, and may be prone to environmental factors to which wired communication is immune.
Below are others communication (or networking) technologies, together with the maximum bandwidth available.
Asymmetric digital subscriber line (ADSL)
640 Kbps upstream and up to 6.1 Mbps downstream
Home users who require fast download speeds, but are not so concerned about upload speeds, as most of the bandwidth is from the ISP to the user
Asynchronous transfer mode (ATM) 25, 45, 155 or 622 Mbps
Used inLAN backbones
Cable modem 512 Kbps to 5 Mbps
Most suited for connection between a home or small business and an ISP
Ethernet 10 Mbps to 1 Gbps
Most popular technology for LANs. Original Ethernet specification supported 10 Mbps, later versions are the Fast Ethernet (100 Mbps) and Gigabit Ethernet (1 Gbps). The 10 Gigabit Ethernet (10GbE) is in development
Fiber distributed data interface (FDDI) 100 Mbps
A good choice for a LAN backbone
Fractional T1 The number of channels of the T1 leased times 64 Kbps but less than full T1 (1.544 Mbps)
Enterprises who do not need the bandwidth of a full T1 line
Frame relay 56 Kbps to 45 Mbps
Corporate WANs – for businesses that need to communicate internationally
G.Lite (also known as DSL Lite) From 1.544 to 6 Mbps (upstream) and 128 to 384 Kbps (downstream)
A popular version of DSL for home users because it does not require a visit from the telephone company to configure the connection
GSM mobile telephone service 9.6 to 14.4 Kbps
Wireless technology used for mobile telephones
High-bit-rate DSL (HDSL) Up to 3 Mbps
Symmetric (equal upstream and downstream bandwidths) DSL technology, used to provide dedicated WAN links for businesses
Institute of Electrical and Electronics Engineers (IEEE) 802.11b (wireless) 5.5 Mbps or 11 Mbps
A popular wireless technology, widely used in wireless LANs (WLANs)
IEEE 802.11a (wireless) Up to 54 Mbps
Considered as the successor to 802.11b, but incompatible with it
Integrated services digital network DSL (IDSL) 128 Kbps
Home users who cannot use ADSL or HDSL
Integrated services digital network (ISDN) 64 Kbps to 128 Kbps
Home users and small enterprises
Regular telephone (POTS, plain old telephone service) Up to 56 Kbps
Uses a modem to connect a home to an ISP
Synchronous optical network (SONET) 51, 155, 622, 1244, or 2480 Mbps
Most suited for backbones, different set of SONET signaling rates represented by optical carrier (OC) levels, ranging from OC-1 (52 Mbps) to OC-256 (9.6 Gbps)
T1 1.544 Mbps
Connections between large companies and branch offices or an ISP
T3 45 Mbps
Corporations that transmit large amounts of data, and require the increased bandwidth
Token Ring 4 or 16 Mbps
Most suited for LANs, but eclipsed by Ethernet, considered a legacy technology
Very-high-rate DSL (VDSL) Up to 55 Mbps (upstream) and 2.3 Mbps (downstream) over short distances (less than a mile)
Emerging DSL technology
X.25 Up to 2 Mbps, but typically 64 Kbps
Communication between mainframes and “dumb” client terminals, largely replaced by other technologies, but still used in specialist financial applications
