This article constitutes section 1, part C, chapter 3 of the CIW Website design manager course and briefly covers: LANs and WANs (Networks)
Local Area Networks (LANs)
In most cases, a LAN is a network within one location, usually a single office building. They can extend beyond a single building but will always be within a distinct geographic area.
Wide Area Networks (WANs)
A WAN extends over a much wider geographic area and will comprise several offices interconnected by leased lines or The Internet.
Network Access Points (NAPs)
A Network Access Point is a junction between one high speed network and another. NAP connections are usually made by a router or a switch. These high speed networks provided essential connectivity for the Internet and, as such, are called Internet backbones.
Common Network Components
- Network Interface Card (NIC)
- Every computer on a network will have a NIC as this is what connects the computer to the network.
- A repeater is an amplifier that boosts the electronic signal on a cable segment extending the distance the segment may span. Repeater operate at the physical layer of the OSI/RM.
- A hub connects computers in a star-configured network. The hub serves as a concentration point for the network. Hubs operate at the physical layer of the OSI/RM.
- Bridges connect two network segments and filter the packets dependant on the destination address. Bridges operate at the data link layer of the OSI/RM.
- Routers are similar to bridges except that they operate at the network layer of the OSI/RM. Routers are protocol dependant and use the network address to determine the best route for a packet. The router will forward data from one network to another as opposed to a bridge which connects one segment to another.
- A switch directs the flow of data from one network node to another allowing these nodes to use the full bandwidth of the connection rather than sharing it with the whole network as would occur when using a hub. Switches can operate at several layers of the OSI/RM. A layer 1 switch is often called a switching hub, a layer 2 switch cab be called a LAN switch and forwards traffic based on MAC Address, A layer 3 switch is called a routing switch and forwards traffic based on layer 3 information and a layer 4 switch uses higher category information such as the TCP/UDP port that the application uses.
- A brouter is a bridge/router and incorporates the function of both. This works at layers 2 and 3 of the OSI/RM.
- A gateway, also called a protocol converter, can operate at any layer of the OSI/RM. Typically, a gateway must convert from one protocol stack to another.
- A modem is a device that allows communication over a telephone line by converting digital data into audio/analog signals. modem is an acronym for modulator/demodulator.
- Twisted Pair Cable
- A pair of copper wires twisted around each other. The twist help to cancel electro-magnetic fields thereby reducing interference. A twisted pair segment may not exceed a length of 100m. Available in two basic type: Shielded Twisted Pair (STP) and Unshielded Twisted Pair (UTP). Depending upon the category of the cable, the cable may contain several twisted pairs.
- Coaxial Cable
- Coaxial cable contains a single central wire surround by a metallic shield. The cable provides high bandwidth and is used for baseband, broadband and television networks.
- Fibre Optic Cable
- Fibre Optic cables can transmit data in the gigabits-per-second range, as they send data as pulses of light over threads of glass. There are two major type of fibre: Single mode, uses a specific wavelength and has a core of 8 to 10 microns; Multimode, uses a number of frequencies and has a larger core.
- Register Jack (RJ-45)
- Uses a crimp connector and 4 twisted pair cable and connects one node to a hub or switch.
IEEE LAN Standards
- IEEE 802.2
- The 802.2 standard divides the OSI/RM data link layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC)
- IEEE 802.3 Ethernet
- Ethernet and 802.3 are not one and the same but are used interchangeably.
- IEEE 802.3u Fast Ethernet
- Fast Ethernet supports the 100baseTX and 100baseT4 wiring standards, which require Category 5 UTP wiring to support 100 Mbps. It can also use 100baseFX fibre optic cabling.
- IEEE 802.3z and 802.3ab Gigabit Ethernet
- Gigabit Ethernet is the fastest 802.3 LAN technology and is used, primarily, for network backbones. The 802.3z flavour uses speciality copper cable and fibre optic cable. The 802.3ab flavour uses Category 5 UTP cable to achieve 1,000 Mbps.
- IEEE 802.5 Token Ring
- Originally developed by IBM Token Ring does not use CSMA/CD, rather it employs a token passing method to achieve speeds of 4 to 16 Mbps. Toke Ring uses a Star Topology with a hub-like device call a MultiStation Access Unit (MAU) to form a ring.
I regularly consult Wikipedia to affirm my understanding of any given subject.