•What is a (computer/data) network?

•Statistical multiplexing–Packet switching•OSI Model and Internet Architecture•Introduction to theInternet

Introduction - I ntroduction to Ne tworking pute twork What is a(com r\/data ne tatistical m ultiple xing S t Packe switching I l rne cture OS Mode and I

Computer Networks CSci232: Introduction 1 Introduction to Networking •What is a (computer/data) network? •Statistical multiplexing–Packet switching•OSI Model and Internet Architecture•Introduction to theInternet • Readings – Chapter 1

Computer Networks CSci232: Introduction 2 What is a Network? Therearemany types of networks!  Transportation Networks  Transport goods using trucks, ships, airplanes, …  Postal Services  Delivering letters, parcels, etc.  Broadcast and cable TV networks  Telephone networks  Internet  “Social/Human networks”  …

Computer Networks CSci232: Introduction 3 Key Features of Networks  Providing certain services  transport goods, mail, information or data  Shared resources  used by many users, often concurrently  Basic building blocks  nodes (active entities): process and transfer goods/data  links (passive medium): passive “carrier” of goods/data  Typically “multi-hop”  two “end points” cannot directly reach each other  need other nodes/entities to relay

Computer Networks CSci232: Introduction 4 Data/Computer Networks  Delivery of information (“data”) among computers of all kinds  servers, desktops, laptop, PDAs, cell phones, ......  General-Purpose  Not for specific types of data or groups of nodes, or using specific technologies  Utilizing a variety of technologies  “physical/link layer” technologies for connecting nodes  copper wires, optical links, wireless radio, satellite  or even “non-electronic” means: e.g., cars, postal services, humans -- e.g., recent “delay-tolerant networks” efforts for 3 rd world countries

Computer Networks CSci232: Introduction 5 How to Build Data/Computer Networks Two possibilities  infrastructure-less (ad hoc, peer-to-peer)  (end) nodes also help other (end) nodes, i.e., peers, to relay data  infrastructure-based  use special nodes (switches, routers, gateways) to help relay data

Computer Networks CSci232: Introduction 6 Connectivity and Inter-networking • Point-to-point vs. • broadcast links/ wireless media • switched networks • connecting “clouds” (existing physical networks) – inter-networking using gateways, virtual tunnels, overlays (a) (b) base station

Computer Networks CSci232: Introduction 7 Resource Sharing in Switched Networks Multiplexing Strategies • Circuit Switching – set up a dedicated route (“circuit”) first – carry all bits of a “conversation” on onecircuit • original telephone network • Analogy: railroads and trains • Packet Switching – divideinformation into small chunks (“packets”) – each packet delivered independently – “store-and-forward” packets • Internet (also Postal Service, but they don’t tear your mail into pieces first!) • Analogy: highways and cars

Computer Networks CSci232: Introduction 8 Common Circuit Switching Methods Sharing of network resources among multiple users • Common multiplexing strategies for circuit switching • Time Division Multiplexing Access (TDMA) • Frequency Division Multiplexing Access (FDMA) • Code Division Multiplexing Access (CDMA) • What happens if running out of circuits?