ccnet lec 02 networks around

8/6/2019 Ccnet Lec 02 Networks Around

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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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