devices on a LAN or between two or more LANs 

TYPES OF NETWORK TOPOLOGIES 

1. BUS Topologies – This topology is an old one and essentially has each of the computers on the network daisy-chained to each other. This type of
     network is usually peer to peer and uses Thinnet (10base2)
     cabling. It is configured by connecting a “T-connector” to the
     network adapter and then connecting cables to the T-connectors
     on the computers on the right and left with a terminator at each
     end.

Advantage:

1. Cheap
2. Simple to set up
3. Less cable length than a star topology
   

Disadvantage:

1. Excess network traffic
2. A failure may affect many users
3. Problems are difficult to troubleshoot

2. STAR Topology – The star topology is probably the most commonly used 
  today. It uses twisted pair (10baseT or 100baseT) cabling
  and requires all devices are connected to the hub or con –
  centrator.

Advantage: 

1. Centralized monitoring 
2. Failures do not affect others unless it is a hub
3. Easy to modify

Disadvantage:

1. If the hub fails then everything connected to it is down
2. Requires more cable length than a linear topology
3. More expensive than a linear bus topology because of the concentrator

3. RING Topology – Looks the same as the star, except that is uses special 
  hubs and ethernet adapters. Messages in a ring network
  pass around the ring from node to node in one direction.

Advantage:

1. Equal access

Disadvantages:

1. Difficult to troubleshoot
2. Network changes affect many users
3. Failure affects many users

4. TREE Topology – A topology for LAN in which one machine is connected 
  to one or more other machines, each of which is conn –
  ected to one or more others, and so on. So the structure
  formed by the network resembles that of a tree.

PROTOCOLS – A set of rules or standards designed to enable computers to
  connect with one another and to exchange information with
  as little error as possible.

The most common Protocols are:

1. ETHERNET – The IEEE 802.3 standard for connection networks. Ethernet
     uses a bus or star topology and relies in the form of access
     known as CSMA/CD (Carrier Sense Multiple Access/Collision
     Detection) to regulate communication line traffic 
   
   Ethernet / 802.3 – The IEEE standard for 10 or 100 Mbps transmission over
     an Ethernet network. Ethernet/802.3 defines both hard
     ware and data packet construction.
   
   PACKET – A unit of information transmitted as a whole from one device to
     another on a network. 
2. FAST ETHERNET – Allow for an increase speed of transmission, a new 
     standard that supports 100 Mbps. It requires the use 
     of different, more expensive network concentrators/hub
     and network interface cards. In addition, CAT5 twisted
     pair or fiber optic cable is necessary.
3. GIGABIT ETHERNET – The IEEE standard dubbed 802.3z, which includes
     support for transmission rates of 1Gbps-1000 Mbps
     over an Ethernet network
4. LOCAL TALK – An inexpensive cabling scheme used by Apple talk networks
     to connect Apple Macintosh computers, printers and other
     peripheral devices. It allows for linear bus, or tree topology
     using twisted pair cable. The primary disadvantages is the
     speed of transmission only 230 kbps.
5. TOKEN RING – The computers are connected so that the signal travels 
     around the network from one computer to another in 
     Logical ring. It requires a star wired ring using twisted pair
     or fiber optic cable. The transmission speeds of 4 Mbps or 
     16 Mbps.  
6. FDDI (Fiber Distributed Data Interface) – Provides specification for trans –
     mission rates of 100 Mbps on network base
     on the token ring standards.
7. ATM (Asynchronous Transfer Mode) - A network protocols that transmits 
     data at a speed of 155 Mbps and higher.

CABLE TYPES:

a. 10Base5 – also known as RG-8 or RG-11 – Thicknet coaxial
  connector type (AUI/DIX) – maximum length (500 meters/1,640ft) 

b. 10Base2 – also known as RG-58 – Thinnet coaxial
  connector (BNC) – maximum length (185 meters/607ft)

c. 10BaseT – also known as CAT 3,4,5 – Twisted pair
  connector (RJ45) – maximum length (100 meters/328ft)

d. 100BaseT – also known as CAT 5 - Twisted pair
  connector (RJ45) – maximum length (100 meters/328ft)

e. 10BasedFL – also known as Fiber Optic
  connector (Fiber Optic connector) – maximum length (2 kilometers/6,562ft)

Speeds of various cable types:

• Thicknet – Transmission speed (10Mbps)
• Thinnet – Transmission speed (10Mbps)
• CAT2 Twisted Pair – Transmission speed (4Mbps)
• CAT3 Twisted Pair – Transmission speed (10Mbps)
• CAT4 Twisted Pair – Transmission speed (16Mbps)
• CAT5 Twisted Pair – Transmission speed (100Mbps)
• Fiber Optic – Transmission speed (100Mbps/1Gbps)