There are many ways this term is used. At its simplest, a network is a collection of connected devices.

If it is a Local Area Network (LAN), then the devices are connected to a common medium, such as coaxial cable or Unshielded Twisted Pair (UTP) or the air. A network is often called the wire, and sometimes the segment. But, watch out, because those terms are used in other ways, as well.

If a bridge or switch connects multiple Ethernet LANs, all of the connected LANs are part of the same IP network, also called a subnet, though each is a complete local network. If a router connects multiple Ethernet LANs, each of the connected LANs is a separate IP subnet.

An internetwork is most frequently defined as multiple networks interconnected by routers, though the term network is also sometimes used for this definition. In fact, the entire Internet is sometimes referred to as the Net(work).

Today, the terms IP network and IP subnet are frequently used interchangeably. Though there are some technical distinctions, most of the time, it is not really necessary to be aware of them.

In the Internet Model, the lower two layers of functionality are often referred to simply as “network access”. This is where the local frame is created and sent, hop-by-hop. Different protocols and frames are used for different link types, though all are similar.Ethernet is the most widely use local area network (LAN) type, with wireless LANs second, at least in the home or small office environment. Ethernet was standardized as 802.3. Wireless LANs were standardized as 802.11.

When there is only a single device at each end of a communication link, there aren’t many rules needed for the communication. However, when there are many devices connected to the media, it becomes more important to have an orderly way of sharing the media, so that everyone gets a chance to transmit. The protocols that define this are called Media Access Control or MAC protocols. The MAC protocol of Ethernet (802.3) is called CSMA/CD — Carrier Sense (always monitor the cable for transmissions), Multiple Access (you can see that part - all devices are connected to the same cable or hub)/Collision Detection (this part means to keep monitoring the cable, and, if a collision occurs, follow the collision procedure, to deal with it).

CSMA/CD is a form of contention, which is also used by wireless LANs. Contention means that a device will just start transmitting, whenever it has data to send, IF the media is NOT active - that is, as long as nobody else is transmitting.

Only one device can transmit at a time, or a collision will occur. Each device creates a voltage change on the cable when it transmits. If a second transmission is added, this will cause further change on the cable. This is what is meant by a collision. And, the end result is that both frames will be corrupted and will have to be retransmitted. Collisions were a normal occurence on the original Ethernet LANs, which used coaxial cable. Later, 10BaseT was defined - it uses Unshielded Twisted Pair (UTP) and hubs. 10BaseT also had collisions. In a contention environment, when there are too many users on the LAN, the network gets slow. That is because the ratio of collisions to successful transmissions goes up. Eventually, the network becomes almost unuseable.

This is why bridges were first introduced — to create multiple collision domains. But, that was when coaxial cable was the normal network medium. With 10BaseT (UTP and hub) networks, switches were added to solve the same problem. Switches, however, have many more ports than bridges and often provide a collision domain to each individual user. This means that everyone can transmit at the same time, with no danger of a collision.

If there is more than one device in a collision domain (i.e., on a switch port), the receive circuitry must be used to check for collisions while transmitting, so it is not possible to also receive data. With only a single device per switch port, there is no need to check for collisions, so full-duplex communication can be used.

Wireless LANs use a similar MAC protocol, CSMA/CA, where CA stands for Collision Avoidance, which 802.11 devices attempt to do.

Ethernet/802.3 Variations

Though many different Ethernet/802.3 variants exist, they differ primarily at the Physical Layer and they are all referred to as Ethernet. 10BaseT, 100BaseT, 1000BaseT, 10000BaseT are all called Ethernet, for example. Some have other names, as well, such as Fast Ethernet (100 Mbps) and Gigabit Ethernet (1 Gbps). Current technologies are even using Ethernet in Metropolitan Area and Wide Area networks (MANs and WANs).

Like so many networking terms, this one has several different definitions.There are two main definitions, which are quite distinct:

• Older definition - Broadband, as opposed to baseband, means having multiple frequency ranges, or channels, which can all carry information, at the same time. The analog cable TV system is an example of this definition of broadband. Baseband signals consume all available bandwidth - there is only one channel. Ethernet is baseband.
• Newer definition - Broadband, as opposed to narrowband, simply means more bandwidth! However, where the line between narrowband and broadband is drawn tends to vary. Broadband can mean anything from "faster than a telephone line" or about 64 Kbps, to greater than 45 Mbps.

There are many different types of wireless networks including cellular voice networks, satellite TV and data networks, Personal Area Networks (PANs), and wireless LANs (WLANs). The term Wi-Fi refers specifically to 802.11 WLANs. There are several existing and merging 802.11 standards, but 802.11b/g WLANs are the most common, with 802.11n approaching standardization. Wireless LANs provide the same basic functionality, as Ethernet (wired) LANs. Going from 802.11 b to g and soon to n brings higher speeds and longer distances.

Like Ethernet, WLANs use a contention media access method. In fact, 802.11 was originally referred to as Wireless Ethernet. A vendor organization called Wireless Ethernet Compatibility Alliance (WECA) was formed, to test compatibility among different products and interoperability with Ethernet LANs. The name was later changed to the Wi-Fi Alliance, after the term “Wi-Fi”, for Wireless Fidelity, caught on. Wi-Fi became associated with 802.11b and, more recently, with 802.11g, a faster version of 802.11 that is backwards compatible with 802.11b.

Three are three broadband service choices for home or SOHO users: cable, DSL, and satellite. Not all choices may be available in your area. Satellite is available in virtually all of the United States and much of the world. Cable, DSL, and satellite services have different speeds, depending upon the service offered, the number of users sharing the bandwidth of the service, and the level of congestion on the Internet. Speeds range from 100 Kbps to several Mbps. Higher speed services will cost more, in general.

Here is a little additional information about each of the choices:

• DSL stands for Digital Subscriber Link, which means that instead of the usual analog last mile to the subscriber premises (i.e., your house), it is digital. There are several different types of DSL, but all are considered to be broadband connections to your service provider. Service plans typically offer unlimited usage, on a monthly basis.
• A cable modem provides a very similar broadband connection to the service provider, but, in this case, the service provider is a cable company, instead of the telephone company. As with DSL, monthly service plans offer unlimited usage.
• Two-way satellite service is available anywhere in the United States where there is a clear view of the southern sky. It is also the only broadband service that is available for RVers now. StarBand® makes it easy for anyone to get their own installer certification. See StarBand Training and Support, for more information

See Satellite Broadband Services for more info about satellite services.

Yes, they can. And, if you have a digital service, it can be much faster than a regular dial-up connection. Usage plans vary, but many let you use your monthly allocation of minutes for either voice or data. You will need to purchase the correct cable for your phone, from your service provider. You will also need software, which is also available from your provider.

Since 2007, most of the digital cellular carriers have offered both a PC Card and a USB adapter for connecting PCs to the cellular network.