BA 471 – Telecommunications and Networking Dr. V.T. Raja Oregon State University 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 – –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) Design the most economic internetwork between “end-user nodes” and an existing WAN (Wide Area network e.g. the Internet) Usernode WAN

Network Design Find an economic internetworking solution Usernode A direct connection to a WAN backbone node Usernode Connection via multiplexers

Some Network Design Issues Major Cost Components Acquisition and installation costs of a MUX Acquisition and installation costs of a MUX Cost of high bandwidth link between MUX and WAN (Internet) Cost of high bandwidth link between MUX and WAN (Internet) Cost of low bandwidth link between end- user node and MUX Cost of low bandwidth link between end- user 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). 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... 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

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Theoretical Framework: 5-layer network model 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: TCP (Transmission Control Protocol) operates at the Transport Layer. –Example of a transport layer default port address/port ID: 80 (Web); 25( )

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: Ethernet operates at the data link layer. –Example of a DLL address: 00-B0-D0-B

Application and Transport Layers User interfaces with application software using: –Application layer (e.g., web/ ) 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