Introduction - I ntroduction to Ne tworking pute twork What...

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 the Internet
•
Readings
–
Chapter 1

Computer Networks CSci232: Introduction 2
What is a Network?
There are many 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 one circuit
•
original telephone network
•
Analogy: railroads and trains
•
Packet Switching
–
divide information 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
•