Transcript BA 479 - Business Information Communications and Networking

BA 471 – Telecommunications and
Networking
Dr. V.T. Raja
Oregon State University
[email protected]
As presented in Dr. Marshall’s BA471 class, Winter
2006
Outline
• Introduction
– Analogy with effective human communication
• 5-layer Network Model
A theoretical framework for our day-to-day
interactions on the Internet
Some Basic Characteristics of Effective
Human Communication
• Sender/Receiver
• Messages (Words)
• Transmission Media
Air/Printed Page
• Less noisy room (or) talk loud enough
• Speak same language or have an Interpreter
Some Basic Characteristics of
Telecommunication Networks
• Source; Destination – Host
• Signals (Digital/Analog)
– Modulation (digital to analog)
– Demodulation (analog to digital)
– Done by a Modem
• Transmission Media
– (Wired/Wireless)
• Communications Protocols/Standards
Wired Transmission Media
• Coaxial (like cable TV)
• Twisted Pair
– Copper
– Shielded and twisted to reduce noise
• Fiber Optic
– Much faster
– Able to go longer distances without a repeater
– Uses light not electricity
– Multi-color lights vastly increases capacity
– Expensive
Wireless Transmission
• Infrared (as in a TV remote)
• Radio Signals (as in microwave transmissions)
• Satellites
– http://www.orbitaldebris.jsc.nasa.gov/index.html
– GEOS: Geosynchronous Earth Orbiting Satellites –
stationary orbit at 22,300 miles above the Earth
– LEOS: Low Earth Orbiting Satellites
– Closer to the Earth and reachable from mobile
devices
– 200-1,000 miles above the Earth
– Not stationary, goes around the Earth in about 90
minutes
– 60-70 LEOS are needed to cover the Earth
Network Design
How to support full connectivity?

Design the most economic internetwork
between “end-user nodes” and an existing
WAN (Wide Area network e.g. the Internet)
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WAN
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Network Design
Find an economic internetworking solution
A direct connection to
a WAN backbone node
Connection via
multiplexers
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Some Network Design Issues
Major Cost Components
Acquisition and installation costs of a MUX
 Cost of high bandwidth link between MUX
and WAN (Internet)
 Cost of low bandwidth link between enduser node and MUX


A Multiplexer (MUX) consolidates several (many?) slow links
(local networks or single nodes) connecting them to a fast link
(e.g. a WAN such as the Internet).
Network Design Management
How to design a feasible and economical
internetwork?
Find an optimal number of MUXs to interconnect all
given user nodes to some existing WAN such that ...
 All user nodes are connected
 User communication requirements are satisfied
 Capacity constraints on each MUX is not violated
 Total internetworking costs are minimized
 Topology issues are considered

Example 1
Example 2
Example 3
Theoretical Framework:
5-layer network model
•
•
•
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Application Layer (Layer-5)
Transport Layer
Network Layer
Data Link Layer
Physical Layer (Layer-1)
Protocols and addresses used at different
layers of the 5-layer network model
• HTTP (Hyper Text Transfer Protocol)
operates at the Application Layer.
– Example of an application layer address:
www.bus.oregonstate.edu
• TCP (Transmission Control Protocol)
operates at the Transport Layer.
– Example of a transport layer default port address/port
ID: 80 (Web); 25(E-mail)
Protocols and addresses used at different
layers of the 5-layer network model
• IP (Internet Protocol) operates at the
Network Layer.
– Example of an IP address: 128.192.64.224
• Ethernet operates at the data link layer.
– Example of a DLL address: 00-B0-D0-B4-54-13
Application and Transport Layers
• User interfaces with application software using:
– Application layer (e.g., web/e-mail) address
• Transport layer’s major function is:
– Packetizing
• Breaking large messages into smaller packets at source
• Reassembling packets at final destination
• Creates/appends TCP header
– Packet #
– Source/Destination Port ID
Network Layer
• Major functions of IP at network layer
are
– Addressing and
– Routing
• IP prepares IP header which contains:
– Source/Destination IP Address and
– Routing Information
Network Layer (Continued)
• Addressing
– DHCP (Dynamic Host Control Protocol) Server
•
Assigns IP addresses to client machines requesting an
IP address
– DNS (Domain Name Service) Server
•
Similar to directory assistance – used for finding
destination IP addresses.
• Routing
– Routing tables; Routers (Tracert); Routing
Protocols
Data Link Layer
• Major functions of Data Link Layer are:
– Media Access Control
• Handling message collisions
– Error Detection
– Error Correction
– Message Delineation
• Identifying beginning and ending of packets – since all
computer transmissions go out as 0s and 1s over the
physical layer
• DL layer appends a DL header and DL Trailer
Physical Layer
• Wired Media/Wireless Media: Examples
– Twisted pair; Coaxial; Fiber Optic Cables
– Microwave; Satellites and Cell phones
• Internetworking Devices: Examples
– Hubs; Multiplexers
– DSL/Cable Modems
– Switches; Routers