ccnet lec 02 networks around
TRANSCRIPT
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Lecture
02Computer Communications& Networks
Networks around us
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Categories of Networks:
We can categorize networks in so many ways, e.g.with respect to:
Geographical coverage area
Technology/protocols used
Fixed vs. wireless
Telecomm vs. Data Comm
Well start to understand networks initially bydividing them on the basis of their coverage area
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Networks Coverage Area:
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Networks: cont
Personal Area NetworkUp to 10s of meters
Bluetooth (IEEE 802.15)
Local Area NetworkUp to 1 kilometer
Ethernet (802.3), Token Ring (802.5), WLAN (802.11)Metropolitan Area Network
Up to 10s of kilometers
WiMAX (802.16)
Wide Area NetworkUp to hundreds/ thousands of kilometersCan be a private network
InternetGlobal scale public network
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Personal Area Networks: (PANs)
BluetoothTM
IEEE 802.15 StandardDefines three classes:
Class-1 = 100m
Class-2 = 10m
Class-3 = 1m
Has Master-Slave architecture
A Master can have sevenslaves
IEEE = Institute of Electrical and Electronic Engineering
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Local Area Networks: (LANs)
Small geographical coverage areaBuilding or small campus
Usually the organization that uses LAN also owns it
Maintenance is organizations responsibility
Initial connectivity cost is high
Available Data rates are higher
Error rates are low
Isolated network; less data security threats to face
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LAN Topologies:
Network Topology:Physical interconnection of computer systems
Wired Topologies:
Bus (Horizontal)
Ring
Star
Tree (Hierarchical)
Wireless Topologies:
Centralized (Infrastructure mode)
Distributed (ad hoc mode)
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Star Topology: (Example)
IEEE 802.3 StandardNodes interconnected viasome central node
Central node called
Hub or SwitchMost widely used wiredtopology
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Bus or Horizontal Topology:
Earlier version of IEEE 802.3 Standard (Ethernet)All nodes connected via a shared medium
Signal transmitted by one node is received by all othernodes on the LAN
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Ring Topology:
IEEE 802.5 StandardNodes interconnectedwith each other in a ringshape
Data flow is usuallyunidirectional
Modern form is FDDI
FDDI = Fiber DistributedData Interface
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Wireless LANs:
(Centralized) (Distributed)
IEEE 802.11 WLAN StandardETSI HiperLAN Standard
Two configurations are possible
Centralized (Access Point serves as infrastructure)
Distributed (No infrastructure required, ad hoc mode)
ETSI = European Telecommunication Standards Institute
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Metropolitan Area Networks: (MANs)
Covering 30-50 km areaWhole city
Number of remote areas
Wired MANs could not get popularity
Wireless MANs are expected to get the market
IEEE 802.16 Standard (WiMAX)(recently largely deployed in Pakistan by Wateen, Mobilink, PTCL)
IEEE 802.20 Standard(Support for high speed mobility)
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Wireless MAN:
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Wide Area Networks:
Large geographical areaNormally a public network
Connecting millions of people
Prevailing technologiesCircuit switching
Packet switching
Frame relay
Asynchronous Transfer Mode (ATM)
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WAN Architecture:
Intermediate switching nodes in core network forward packets of endnodes located at edges of the network
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Circuit Switching:
Dedicated communication path is established forthe duration of the conversation
Path consists of sequence of physical linesbetween the nodes
Data generated by source is transmitted only onthis path
It is fast, no delay at intermediate nodes
Example: Telephone network
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Circuit Switching: cont
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Packet Switching:
No dedicated path is reserved
Data is divided into a sequence of small packets
All packets doesnt necessary to pass from same path
Some extra information (header) is attached with each
packetAt each node packet is stored briefly and then transmitted tothe next hop
Some delays at intermediate nodes are introduced so, it is
slow but link utilization is improvedExample: Internet
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Packet Switching: cont
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Packet Switching: cont
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Differences b/w Circuit & Packet Switching:
Circuit-switching Packet-Switching
Guaranteed capacity No guarantees (best effort)
Capacity is wasted if data isbursty
Better utilization of capacity
Before sending data, path isestablished
Send data immediately
All data in a single flow followsame path
Different packets of flow mightfollow different paths
No reordering; constant delay; nopacket drops
Packets may be reordered,delayed, or dropped
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Questions ???
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