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Networks & Data communications_2 (Local Area Networks (LAN) (Most of…
Networks & Data communications_2
Local Area Networks (LAN)
Most of the computers are personal computers or workstations
Routers & perhaps gateways are used to connect the LAN to other networks
Typically ranging in size from a single room to multiple buildings in
close range
of each other
Create separate LANs for different departments or for different business functions is done to minimise extraneous traffic on the network
A network that connects computers & other supporting devices over a rel
small localised area
Most modern LANs are based on one of the Ethernet protocol standards
Ethernet Hubs
Physical layer device where all of the connections are tied together inside the hub
Signals are broadcast to every device connected to the hub
A passive central connection device used to simplify wiring & maintenance
Use of hubs is declining because switches often provide better performance
Based on bus topology
Wireless Ethernet
(WiFi)
Central access point transmits & receives radio waves to communicate with the nodes
Radio space must be shared btwn the nodes
Central access point is similar to a hub but is an active node
Possible for stations to be out of range or blocked by buildings or other obstacles
-hidden node & out-of-range conditions
Radio-based compatible extension to the Ethernet standard
Some NICs support multiple radio frequencies
Metropolitan Area Networks
(MAN)
Often there is a desire to create network links
to connect locations that would require
running wires through someone else's property
Begins to resemble a WAN
Edge connection - a connection at
an access point on the customer's
premises that connects to a provider
Requires services from a
service provider or public carrier
Campus Area Network
(CAN)
Network type btwn a LAN & a MAN
No of interconnected buildings clustered together
A network larger in geographical scope than a LAN but within a range of < 30 miles or 50 km
Wide Area Networks (WAN)
The carrier network is sometimes
represented as a collection
of private virtual networks
Primary reasons
for WAN's
Org requires data communication
links btwn widely spread facilities
& btwn an org & its external contacts
Org requires fast access to the internet,
either as a consumer or as a provider
of internet services, or both
Distinguishing feature is the extensive
reliance on service providers to provide
the required connectivity btwn nodes
Extranet - a connection btwn a
business & its business partners
that usually uses the internet
as a medium for its activities
Facilitate communications btwn
users & applications over
large geographical distances
Packet Routing
Virtual circuit
Mulit-link channel path used to
send packets btwn two end nodes
Intermediate nodes may be
shared with other channel paths
Packet switching
Each packet is routed from node to node
independently based on various criteria
Circuit switching
Dedicated channel btwn source
& destination for duration of connection
Router & Gateways
Routers
Specialised devices used to interconnect networks
& pass packets from one network to another
Operation
When a packet arrives at an
input port, the processor decides
where the packet is to be directed
A switch is set to direct the packet
to the correct output port
Gateways
Same as routers but connect
dissimilar
networks together
Convert packet headers
for the dissimilar networks
Standards Organisations
IETF
International standards based on
RFCs (request for comments)
Internet Engineering Task Force
ICANN
IP address allocation
, domain name
registration, protocol parameter assignment
Management of domain name
& root server systems
Internet Corporation for Assigned
Names & Numbers
IEEE
Ethernet standards - Ethernet (802.3),
WiFi (802.11), Bluetooth (802.15)
& WiMax (802.16)
Institute for Electrical & Electronics Engineers
IANA
Internet Assigned Numbers authority
Registers application layer port no's &
specific parameter values used in
internet protocol headers
ISO
greater than 17,000 standards including
the OSI Reference Model
International Organisation for Standardisation