Transcript NetworkPurposeTypesPackets

Unit 27:
Principles of Computer Networks
Introduction to Networks
Network Types
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Aims
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Different types of Networks revised
Understand the purpose of a computer
network
Create network drawings
Understand Packets
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What is the purpose of a network?
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Enables file sharing (should cut down on printing
costs)
Share resources, such as printers, scanners,
etc., to get more use out of office equipment
(cutting down costs)
Share software with multi-user licenses.
Perform data backups quicker and easier with
files on shared drives.
Easier and more manageable Internet
connection
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Types of Network
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LAN (Local area network)
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The definition of a LAN has become increasingly
vague over the last ten years.
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It was understood that it was interconnected
computers at one location i.e. college or a workplace.
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Know due to faster technology LAN devices can be
used over longer distances.
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A LAN can be as small as two computers by using a
simple Ethernet connection or can divided into sub
networks using switches and routers.
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Local Area Network - LAN
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Single campus
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Can be multiple networks interconnected
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No special telecommunications hardware
is necessary, as cables/signals never leave
the company’s premises
Fast data transfer rates
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reliability of transmission not always top
priority
damaged data can be re-transmitted easily
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Task
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Using Visio try to recreate the LAN shown below.
(Feel free to make it your own)
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Types of Network
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WAN (Wide area network)
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A WAN is a complex network system, comprising of
interconnected LANs.
WANs are used to connect LANs and other types of
networks together, so that users and computers in
one location can communicate with users and
computers in other locations.
WANs are often built using leased lines.
A router connects to the LAN on one side and a hub
within the WAN on the other
Network protocols including TCP/IP deliver transport
and addressing functions.
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Wide Area Network - WAN
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The rest of the planet
Slower data transfer rates (end to end)
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reliability is a high priority
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retransmission of missing data is a large overhead
extensive use of external telecommunication
systems
backbone transfer rate is now faster than LANs!
The Internet
International telecommunications
Satellite systems
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e.g. Global Positioning System - GPS
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Several options are available for WAN connectivity:
http://en.wikipedia.org/wiki/Wide_area_network
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WAN
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Janet backbone
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All UK academic institutions
access the internet via the
Janet network
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.ac.uk domain
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Funded by Joint Information
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Systems Committee (JISC)
In October 2006 SuperJANET5 was
launched after £29 million of
investment.
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It provided an upgrade path to
40GBit/s.
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Most organisations connected by
twenty WANs
Map from
http://www.janet.ac.uk/about/topology/SJ5topology-map.pdf
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WAN TECHNOLOGIES
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FRAME RELAY
ATM – ASYNCHRONOUS TRANSFER MODE
MPLS – MULTI-PROTOCOL LABELLED
SWITCHING
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FRAME RELAY
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PACKET SWITCHING
MESH CONNECTIONS
CORE OF A WAN
Monitors traffic on
system – re-routing
Directs traffic from
system to system
Cheap
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ATM
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Data cells smaller
than packets
Faster
Separate voice and
data communications
Used with Skype
Similar functions to
Frame Relay
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MPLS
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Most recent successor
Cooperates with
routing protocols
Highly adaptable
Adjusts to changes in
networks
Directs data from one
network node to
another using short
path labels not long
network addresses
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Types of Network
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MAN (Metropolitan area networks)
 A Metropolitan Area Network (MAN) is a large computer
network that spans a metropolitan area or campus. The
network size falls intermediate between LANs and WANs.
 MANs provide Internet connectivity for LANs in a
metropolitan region, and connect them to wider area
networks like the Internet.
 They typically use wireless infrastructure or optical fiber
(or fibre) connections to link their sites.
 A MAN (like a WAN) is not generally owned by a single
organisation. The MAN, its communications links and
equipment are generally owned by either a consortium of
users or by a network service provider who sells the
service to the users.
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Metropolitan Area Network - MAN
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Multiple campuses
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e.g. within a city
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small geographical area
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Australians use MANs to interconnect South
Eastern cities
Slower data transfer rates?
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need reliability of WANs with speed of LANs
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VAN – Value Added Networks
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Hosted sevice
Like a regional Post Office
Intermediatory between business partners
sharing standards or data
Transmits data by EDI or as XML
Routes, stores & delivers EDI messages
EDI – Electronic Data Interchange –
transfers electronic documents or business
data from one partner system to another
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PAN – Personal Area Netork
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Interconnects devices in an individual
person’s workspace
Wireless connections – Bluetooth
Can connect to a higher level network or
Internet
Bluetooth – short range radio waves up to
10 metres
Computers, cell phones, PDAs, headsets,
mouse or other pointing devices
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Types of Network
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Mesh network
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A netlike communications network in which
there are at least two pathways to each node.
A fully meshed network means that every
node has a direct connection to every other
node. Most mesh networks are partially
meshed and require traversing nodes to go
from each node to every other.
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Task
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Using the internet look into what a packet
is.
Create a network diagram in Visio to
represent “SuperJanet”.
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Packet
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A packet is a formatted unit of data carried by a
packet mode computer network.
Computer communications links that do not
support packets, such as traditional point-to-point
telecommunications links, simply transmit data as
a series of bytes, characters, or bits alone.
When data is formatted into packets, the bitrate
of the communication medium can better be
shared among users than if the network would
have been circuit switched.
By using packet switched networking it is also
harder to guarantee a lowest possible bitrate.
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Conclusion
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Considered the purpose of a computer
network
Revised some of the different types of
networks
Used Visio to create network diagrams
Gained an understanding of a Packet
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