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This lecture is part of lecture series on Data Communication Systems. It was delivered by Prof. Prajin Ahuja at Birla Institute of Technology and Science. Its main points are: Protcol, Access, Communication, Etities, Peer, Congestion, Telephony, Bandwidth, Swtiching, Multiplexing
Typology: Slides
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Introduction
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use Internet asexample
Overview: ^
what’s the Internet ^
what’s a protocol? ^
network edge ^
network core ^
access net, physical media ^
Internet/ISP structure ^
performance: loss, delay ^
protocol layers, service models ^
network modeling
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Introduction
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1.1 What
1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs1.6 Delay & loss in packet-switched networks1.7 Protocol layers, service models1.8 History
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Introduction
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What’s the Internet: “nuts and bolts” view
e.g., TCP, IP, HTTP, FTP,
PPP
loosely hierarchical public Internet versusprivate intranet ^
Internet standards^
RFC: Request for comments IETF: Internet EngineeringTask Force
local ISP companynetwork
regional ISP
router
workstation
server
mobile
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Introduction
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What’s the Internet: a service view^
Web, email, games, e-commerce, file sharing ^
communication servicesprovided to apps:^
Connectionless unreliable connection-orientedreliable
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Introduction
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Hi Hi Got thetime?2:
TCP connectionreqTCP connectionresponseGet http://www.awl.com/kurose-ross
time
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Introduction
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1.1 What
1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs1.6 Delay & loss in packet-switched networks1.7 Protocol layers, service models1.8 History
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Introduction
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run application programs e.g. Web, email at “edge of network” ^
client/server model^
client host requests, receivesservice from always-on server e.g. Web browser/server;email client/server ^
peer-peer model:^
minimal (or no) use ofdedicated servers e.g. Gnutella, KaZaA
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Introduction
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Network edge: connection-oriented service
Goal:
data transfer between end systems
Hello, hello back humanprotocol ^ set up “state” in twocommunicating hosts ^
TCP - TransmissionControl Protocol^
Internet’s connection-oriented service
TCP service
loss: acknowledgementsand retransmissions
sender won’t overwhelmreceiver
senders “slow down sendingrate” when networkcongested
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Introduction
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1.1 What
1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs1.6 Delay & loss in packet-switched networks1.7 Protocol layers, service models1.8 History
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Introduction
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mesh of interconnectedrouters
This image cannot currently be display ed.This image cannot currently be display ed. circuit switching:dedicated circuit percall: telephone net packet-switching: datasent thru net indiscrete “chunks”
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Introduction
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Network Core: Circuit Switchingnetwork resources
(e.g., bandwidth)divided into “pieces” ^
pieces allocated to calls ^
resource piece
^
dividing link bandwidthinto “pieces”^
frequency division time division
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Introduction
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frequency
time
frequency
time
Example:4 users
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Introduction
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Network Core: Packet Switchingeach end-end data stream
divided into
^
user A, B packets
network resources ^
each packet uses full linkbandwidth ^
resources used
resource contention: ^
aggregate resourcedemand can exceedamount available ^
congestion: packetsqueue, wait for link use ^
store and forward:packets move one hopat a time^ Node receives completepacket before forwarding
Bandwidth division into “pieces”
Dedicated allocationResource reservation
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Introduction
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Packet Switching: Statistical Multiplexing
Sequence of A & B packets does not have fixed
pattern
In TDM each host gets same slot in revolving TDM
frame. A
10 Mb/sEthernet
1.5 Mb/s D^
statistical multiplexing
queue of packetswaiting for output
link
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