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?
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