NETWORK ELEMENTS

Network - Two or more computers joined together that share resources.

LAN - Local Area Network

Limited to a specific area.
Usually contained within a single building or work area.
Usually divided into smaller workgroups.
Private

WAN - Wide Area Network

Crosses Metropolitan or larger areas.
Speeds are generally slower than on a LAN.
On-demand connection; LANs are usually permanently connected.
Public and private transport.
May be centralized or distributed.

Workstation - a computer that can request resources from the network.

Client - anything that asks for network resources. A printer might be a client.

Server - Provides resources to the clients on the networks. All servers include hardware and software to ensure data integrity and the capability to support a large number of clients.

Includes these servers:

File server
Print server
Proxy server
Application server
Web server
Mail server
Fax server
Remote Access server
Telephony server

Hosts - Any device that has a TCP/IP address.

Architecture

Peer to Peer - All computers on the network are equal to each other.

Each user is responsible for security.
Limited number of computers on the network.
Each user is responsible for backup and data integrity.

Client/Server - Centralized control Network with one (or more) computers controlling the others.

Usuully more organized.
Security is controlled at one point.
Servers have data integrity and backup functions built in.
Better performance and can support huge numbers of users.

Network Attached Storage - Storage device that is easy to plug into a network the provide additional storage. Usually easily configured and very fast to set up.

Physical Topology - A physical map of the network. How the hardware is laid out.

Most common:

Bus
Ring
Star
Mesh
Wireless

Logical Topology - How the data flows in a network. May be entirely different from the physical topology.

Bus Topology - All computers are on a single cable in a line.

Terminators on the end to prevent echo.
Easy to install.
Inexpensive.
Single fault bring the entire network down.
Difficult to troubleshoot.

Star Topology

Spoke and hub model.
New stations added easily.
Single cable failure does not bring down the whole network.
Easy to troubleshoot.
More cables make it more expensive to install.
Only a single point of failure, the hub.

Ring Topology

Simple to design.
Easy to implement.
Any fault brings down the entire network.
Difficult to reconfigure.

Mesh

All machines are concected to all others.
Very expensive to implement.
Very difficult to set up due to numerous cables.
Extremely fault tolerant due to redundant connections.

Wireless

ad-hoc - network forms whenever two machines with proper devices come within proximity to each other.
Multipoint - Numerous devices communicate with a single WAP. Configured to communicate only with the one WAP.
802.11 - Wireless standard. Covered IR as well as RF networks.

Backbone

The main structure to which all components connect
Usually uses high speed technology such as fiber optic or 100 megabit ethernet.
Lower segments usuall connect directly to the backbone.
Servers usually connect directly to the backbone.

Segment

A short section of the network that is connected to the backbone.
Workstations connect to the segment.
Segments are usually derived by workgroup function.

Selection of topology

Cost
Ease of maintenance
Ease of installation
Fault tolerance

Physical Media

Coaxial Cable

Thick Ethernet - 10base5, RG-8, 1/2" in diameter. DIX connectors or N connectors.
Thin Ethernet - 10base2, RG-58, 1/4" in diameter. BNC connectors
Signal Bounce - Echo of a data from the end of the copper.
prevented by using a terminator at the end of the cable. A resistor.
One end of the cable should be grounded, not both.

Twisted Pair

Multiple twisted wires inside a larger cover.

Twisted to reduce crosstalk between wires.

STP/UTP - Shielded twisted pair, unshielded twisted pair
10baseT - Star configured network configuration.
Uses RJ 45 connector

Cheap
Easy to work with
permits reasonably high tranmission rates

Category 1 - 2 twsited pair. POTS wiring
Category 2 - 4 twisted pair - 4Mbps
Category 3 - 4 twisted pair - 10Mbps
Category 4 - 4 twisted pair - 16Mbps
Category 5 - 4 twisted pair - 100Mbps
Category 6 - 4 twisted pair - 1000Mbps

Cable descriptions

NbaseX - N=Mb/s, base or broadband, X=length or cable cable description.

Fiber Optic

Immune to EMI and RFI.
Heavily armored to resist breakage.
Many diiferent connectors but ST (straight tip) most common.
SC (square connector) also common.
Fiber is the only way to cover very long distances (about 2 miles).
More expensive and more difficult to install.

Common Network Connectivity Devices

NIC - Network Interface Card.

Hub - Broacasting device. All signals received are sent all the other computers.

Switch - Sends directly from the sneding to the receiving device. Does not broadcast.

Bridge - Used to connect two network segments together. Will not allow traffic to pass that does not need to go to the other segment.

Router - Makes intelligent decisions about routing. Monitors system performance and available routes. Adjusts traffic to the best route. Keeps a table as to the best route which is updated constantly.

Gateways - Connects dissimilar network environments. Translates dissimlar protocols.

Other

Modem - POTS Modulator/demodulator

DSL - Data over voice connection. Operates at a higher frequency over the same line.

Cable - Data over cable TV lines.

ISDN Terminal Adapter - Similar to DSL, except that the data is always digital.

CSU/DSU - Used to connect the local LAN or WAN to a T1 or other fully digital line. DSU (Data Service Unit) does the actual data transmission through the CSU (Channel Service Unit).

Vocabulary

 

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