Chapter 8 Network Basics
network - interconnection of computers, terminals, or other devices to form a path over which to communicate and share hardware, software, and other data resources.
WAN - network that spans a large geographical area such as a city, state, nation, or th world.
LAN - connects devices within a limited geographic area such as inside an office or a building.
Node - any device in a network that has a network address, and can send and/or receive data on a network
link - the connection, or circuit, established between two adjacent nodes, with no intervening nodes, is called a link.
path - a series of links that allows a connection between two nodes. Intervening nodes can exist on the path between the two target nodes.
Circuit - a complete path between a specific sender and receiver that provides an end-to-end connection.
Point-to-point link - most direct way to connect two devices on a network;
switched networks - nodes are interconnected, and data issnt
from the source to the destination by being routed through the system of
nodes. 3 classifications:
1. circuit-switching - a dedicated path is
created between two node. Entire circuit must be available.
3 phases:
a. establish a circuit
b. actual data transfer
c. circuit disconnected
2. messsage-switching - do not
require a dedicated circuit; message can be sent whether or
not receiver is available to
accept it. Msg is
stored until the receiver connects to the network, at which point message
is sent on to the correct
node. This is called store
and forward. Table 8-1, p 7
3. packet-switching - similiar to message-switching
except the msg is divided into smaller packets, which are all the same
length. 3 methods:
a. datagram services - each packet is treated independently
, meaning packets sent to the same destination may not
follow the same path therefore packets may arrive in the wrong sequence.
b. switched virtual circuit - a logical connection i s established
between 2 nodes before any packets are sent. Route is
predetermined before the packet is sent.
c. permanent virtual circuit - circuit is allocated permanently
between two nodes
broadcast networks - send info over radio waves instead of over
wires; specific type of broadcast network called packet radio network.
2 types:
1. centralized packet radio network
- has a central transmitter/receiver attached to a central computer;
all nodes in the
network communicate only
with this central node. Requires two radio channels - one for sending
and one for receiving.
2. decentralized packet radio network
- one channel is used for all transmissions.
routing - the path or route, data takes on a netwok is determined
by the type of network and the software used to send the data. The
process of deciding what path the data takes is called routing.
1. Centralized routing - one node on the network is in
charge of selecting the path for all data; this node is considered
the
network routing manager. It stores routing
tables, and any changes to an established route must be made at the central
node. Disadvantages p10
2. Distributed routing - relies on each node to calculate its own best
route. Each node contains its own routing tables
Types of Routing:
1. static - data always takes the same route from source to
destination.
2. adaptive, dynamic - selects the best current route for
data to travel.
3. broadcast - transmitting a message to all of the nodes
in a network; flooding - data is transmitted from the sender to
each node it is attached to.Every other node sends it to each node it is
attached to .
topology - is the phsycial configuration, or layout, of the nodes in the network. Also called network architecture.
Interconnected (mesh) network - every node has a point-to-point link to every other node in the network. Figure on p 12
hierarchical (tree) network - organized like a family tree or an orgranization chart, with a main computer at the top and all other devices branching out beneath
Topologies:
1. Bus - the connection of data equipment along a single
cable segment in a linear or straight line. All computers on
this type
of network will attach or tap into the main
communication line called the bus or backbone. Each device is in
effect
connected directly to every other device.
A break in the chain could bring down the network. Terminator
2. Star - each device is connected to a hub or main host
node. Independent cable segments run from the workstation to the
central connecting device creating a star configuration.
Data sent over the network is transmitted from the sending device
through the central node and on to the receiving
node.
3. Ring - connects all computer together to form a circle.
Data travels from node to node around the entire ring, in one
direction.
4. Star-wired bus - all devices are cabled to a central
connecting device in a star fashioin, all messages are
broadcast and
distributed to all devices on the bus network concurrently.
5. Tree or star-wired ring - a number of hubs or MAUs
connected together
Networks can be classified by who owns the communication equipment and
the lines that make up the network. 4 classifications:
1. private network - built by a company for its own exclusive
use; also refered to as an enterprise network
2. public network - a network built, owned, and maintained
by a common carrier; telephone system, ISPs.
Advantage - reach areas that a private network can’t
3. value added network - a specific type of public network
with added “intelligent” features to satify a customer using the
VAN. Code or speed transalation, storing and
forwarding of messages, and message encryption.
4. packet distribution network (PDN) or X.25 - a value
added network that uses packet-switching to send data on a public or
private network.
Network types:
1. LAN - covers a relatively small area; owned entirely
by the organization that installs them; data doesn’t travel over
public
communication media; not regulated by an gov.
Agency. Company has sole responsbility of network
2. WAN - located in widely dispersed geographical areas;
usually makes use of public dial-up or leased communication lines;
regulated by the gov.
Internetwork (internet) - two or more networks joined together
Internet - used to describe a global WAN of connected networks that allows public access to info and services.
WWW - part of the Internet that support multimedia
intranets - internal networks that use Internet and Web technology.
Electronic publishing of organizational informations such as telephone
directories, event calendars, and employee benefit information. Can
only be accessed by specific userss. Firewall protects against unauthorized
access. Firewall - hardware and software used to restrict access
to data on a network. Uses of Internet and intranets. 22- 24
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