Networking in General

A Network is a combination of hardware (servers, printers, workstations, cabling) and special software that allows information to be shared.

Servers are hardware equipment that provide services to workstations such as printing and sharing of files.

Most networks can be broken down into two distinct camps. Peer-to-Peer and Server based. Server based networks require that all shared data reside on the server unlike Peer-to-Peer where data can reside on any computer connected to the network.

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1) Basics

Computers are connected together with Network Interface cards (NICs). The 4 most common topologies used for connecting are

* Ethernet
* Token Ring
* ARCnet
* FDDI

Data is transmitted using different methods of modulation.

* Amplitude-Shift Keying (ASK) is a method where the amplitude of the signal varies with time. At any particular moment the signal amplitude denotes a one or a zero. Like AM radio this modulation is very susceptible to noise.
* Frequency-Shift Keying (FSK) is a method where a certain frequency represents a one and another frequency a zero. This method has a limited rate of transmission.
* Phase-Shift Keying (PSK) uses a method of changing the phase of the signal.

There are several different ways for the data to be transmitted.

* Over coaxial cable
* Twisted pair cable
* Fiber Optic cable
* Microwave
* Infrared
* Radio

Topologies

Network Topologies are broken down into physical and logical parts.

Physical topologies include:

* Ethernet Bus - 802.3, 10Base2, 10Base5
* Token Ring Star - IEEE 802.5
* Ethernet Bus Star - 802.3 10BaseT
* Dual Counter Rotating Ring - FDDI ANSI X3T9.5

A network can be designed to be of one physical topology and have a different logical topology.

The two most used logical topologies are Ring and Bus.

In the Ring topology the data is transmitted from one node to another in a predetermined pattern.

In the Bus topology any node can transmit data in any order.

Ethernet

Ethernet is commonly configured using either coaxial cable (BNC) or twisted pair cabling (10Base-T).

With BNC the cable is connected to a Network Interface Card (NIC) with a T connector. The T-connector must be used on all NICs. Each end of the T-connector connects to the computer (node) next in line, and the two nodes at the end of the chain MUST have a terminator in place.

Note: You can NOT connect a BNC coaxial cable directly into the NIC. It will not work. Always use a T-connector and terminate the end nodes.

With 10Base-T, a twisted pair cable connects each node to a central black-box called the hub ( also known as a concentrator ). The hubs connect the nodes in a physical star topology but the logical make up is of a bus.

Ethernet Cabling

* UTP and STP with RJ45 connectors.

Token Ring Star

Token Ring Bus

FDDI

10base2

10Base2 is a 10Mbps baseband standard and defined in IEEE 802.3.

10Base2 (thin net) uses RG-58A/U or RG-58C/U coaxial cable with BNC connectors, 50ohm terminators and T-connectors for attaching the NIC to the network. One end of the network must use a grounded terminator.

Maximum distance is 185 meters (607 feet) and minimum distance between two adjacent network cards is .5 meters (1.5 feet). Total network length is 925 meters, and the maximum nodes is 30.

Note: The RG-58U is a standard TV cable wire and cannot be used on networks.