Introduction and Netrwork Hardware
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Transcript of Introduction and Netrwork Hardware
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Chi-Cheng Lin, Winona State University
CS 313 Introduction to Computer Networking &
Telecommunication
Introduction
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Topics
Introduction Metric Units Network Hardware Network Software Reference Models Example Networks Standards and Standards
Organizations
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Introduction
First two decades of computingHighly centralized computer systems
NowA large number of SEPARATE but
INTERCONNECTED computers Computer networks
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What is Computer Network?
An INTERCONNECTED collection of AUTONOMOUS computersInterconnected: Able to EXCHANGE
INFORMATION via transmission mediaMedia: copper wire, fiber optics,
microwaves, communication satellites
Autonomous: no master/slave relationNOT autonomous:
One computer can control another one e.g., a large computer with remote printers
and terminals
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What is Telecommunication?
What is data communication?Exchange of data between two
devices via some form of transmission media
Data are represented by bits – 0s and 1s
What is telecommunication?Exchange of information over
distance using electronic equipment
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What is Telecommunication? Components of data communication
Sender, receiver, medium, message, and
Protocol: set of rules governing data communication
Key elements of a protocolSyntax
Structure/formatSemantics
MeaningTiming
When and how fast
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Data Communication
Components of data communication
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Sender ReceiverMedium
Message
Step 1: …Step 2: … :
ProtocolStep 1: …Step 2: … :
Protocol
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Distributed System vs. Computer Network Distributed system
TRANSPARENCYA collection of independent computers
appear as a single coherent system
Single model/paradigm to usersMiddleware on top of OSExample?
Computer networkNo such coherence, model, middlewareMachines visible to users
Users log onto remote machines
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Distributed System vs. Computer Network
A distributed system is a SOFTWARE system built on top of a network
Distinction between network and distributed systemSoftware (especially OS) rather than
hardware However, considerable overlap
between the two subjects
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Uses of Computer Networks
Business applicationsResource sharingCommunication mediumE-commerce
Client-server modelClient requests, server performs & then
replies E.g., one or more file servers, many
clients
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Business Applications of Networks
A network with two clients and one server.
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Client-Server Model
1
2
3
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Uses of Computer Networks Home applications
Access to remote informationOn-line publishing, digital library, WWW
Person-to-person communicationEmail, instant messaging, peer-to-peer
communication, videoconferencing, Internet phone, E-learning
Interactive entertainment Video on demand (VOD), games
E-commerceHome shopping, electronic banking and
investment, on-line auction
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Home Network Applications (2)
In peer-to-peer system there are no fixed clients and servers.
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Mobile Users
Notebook, PDA, cellular phone M-commerce Wireless networking and mobile
computing
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Metric Units
The principal metric prefixes.
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Network Hardware By transmission technology
Broadcast links smaller, geographically localized
networksPoint-to-point links
larger networks By scale
PANLANMANWAN
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Classification by Scale
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Broadcast Network
A single communication channel shared by all machines on the network
Packets (short messages) sent by any machine are “received” by all the othersAddress field of packet: whom it is intended
Message transmissionUnicast: one sends, one receivesBroadcasting: one sends, all receiveMulticasting: one sends, a group receives
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Point-to-Point Networks
Many connections between pairs of machines
Intermediate machines (called routers) might have to be visited by a packet from source to destination – more than one path is possible
Routing algorithms are importantRouting: process of finding a path
from a source to the destination(s) in the network
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Local Area Network (LAN)
Private-owned Networks Within a single building/campus Size: up to a few kilometers Characteristics
SizeRestricted by size worst-case transmission time bounded
and known in advance network management simplified
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LAN Characteristics
Transmission technologyMachines attached to a single cableSpeed/capacity (High): 10 - 100 Mbps,
Gbps Mbps/Gbps: Megabit/Gigabit per second 1 megabit=1,000,000 (not 220=1,048,576) bits
Delay (low): microseconds, nanosecondsErrors: very few
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LAN
Characteristics Topology – the way in which a
network is laid outExamples: bus, ring, tree, star, fully-
connected
Bus Ring
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LAN - Topology Bus (linear cable)
Only one machine can transmit at a timeArbitration mechanism needed to resolve
conflicts when two or more computers want to transmit simultaneouslyCentralized or Distributed
Example: IEEE 802.3 (Ethernet):Bus-based broadcast network with
decentralized control operating at 10 Mbps to 10Gbps.
If two or more packets collide, each computer just waits a random time and tries again later.
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LAN - Topology
TreeCentralized deviceExample: Ethernet w/ hubs/swtches
RingBits propagate around the ringArbitration mechanism is needed, tooExample: IEEE 802.5 (IBM Token Ring)
Ring-based LAN operating at 4 and 16 Mbps
Arbitration is based on “token” Only token holder can transmit
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LAN - Channel Allocation
Needed as all computers share one communication pathway
Static channel allocationDivide up time into discrete intervalsRun a round robin algorithmAllow each machine to broadcast only
when its time slot comes upProblem: Wasting channel capacity
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LAN - Channel Allocation
Dynamic channel allocationCentralized
A central entity determines who goes next
DecentralizeNo central entityEach machine decides for itself to
transmit or notAlgorithms needed to resolve potential
chaos
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Metropolitan Area Network (MAN)
Covers city Examples
Cable TV networkIEEE 802.16 high-speed wireless
Internet access
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Metropolitan Area Networks
A metropolitan area network based on cable TV.
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Wide Area Network (WAN)
Country or continent Components
Host (end system) Machine running user (application)
programs
Communication subnet (subnet) Connecting hostsCarrying messages from host to host
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WAN - Subnet Components
Transmission linesMove bits between machines
Switching elementsSpecialized computers that connect
two or more transmission linesDetermine out going line for incoming
dataROUTER
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WAN - Hosts and Subnet
: Host
: Router
H1
H2
R1 R2
R3 R4
R5 R6
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WAN - Architecture
Contains numerous cables or telephone lines
Each cable connects a pair of routers Two routers must communicate
indirectly if they are not connected by a cable
There might be more than one route between two hosts and it might change from time to timeE.g., Route from H1 to H2
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WAN - Architecture
An intermediate router in a WANReceives a packet in its entiretyQueues the packet until required
output line is freeForwards the packet
Subnet using the principle above is calledStore-and-forward or packet-switched
subnet
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Wide Area Networks
A stream of packets from sender to receiver.
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Topology – LANs vs WANs Local networks
Bus, Ring, StarTree
WANs typically irregular
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WAN - Broadcast Systems Satellite system
Each router has an antennaSometimes routers are connected to
a substantial point-to-point subnet, with some of them having a satellite antenna
Inherently broadcast
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Wireless Network
System interconnectionExample: Bluetooth
Wireless LANsEasy to install IEEE Standard 802.11
Wireless WANsIEEE Standard 802.16
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Wireless Networks
Bluetooth configuration Wireless LAN
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Wireless Network
Combinations of wired and wireless networking (e.g., flying LAN)
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Home Network Categories Computers
Desktop PC, PDA, shared peripherals Entertainment
TV, DVD, VCR, camera, stereo, MP3 Telecomm
Telephone, cell phone, intercom, fax Appliances
Microwave, fridge, clock, furnace, aircon Telemetry
Utility meter, burglar alarm, babycam
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Internetwork What is internetwork?
A collection of interconnected networks "Internet" and "internet"
internet: internetworkInternet: the worldwide internetwork using
TCP/IP protocol suiteThe “Big Picture”
http://navigators.com/internet_architecture.html
Problem: Communication between networks with different SW/HWSolution: Gateways
Machines connect different, incompatible networks
Connection and translation