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CPSC 441: Computer Communications Instructor: Anirban Mahanti Office: ICT 745 Email: mahanti@cpsc.ucalgary.ca Class Location: MFH 164 Lectures: Tuesday, Thursday 8:00 am

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CPSC 441: Computer Communications

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Cpsc 441 computer communications l.jpg
CPSC 441: Computer Communications

Instructor: Anirban Mahanti

Office: ICT 745

Email: mahanti@cpsc.ucalgary.ca

Class Location: MFH 164

Lectures: Tuesday, Thursday 8:00 am

Text Book: “Computer Networking: A Top Down Approach Featuring the Internet”, 3rd edition, Jim Kurose, Keith Ross Addison-Wesley.

Slides are adapted from the companion web site of the book.

CPSC 441: Introduction


Roadmap l.jpg
Roadmap

  • What is a Computer Network?

  • Applications of Networking

  • Classification of Networks

  • Layered Architecture

  • Network Core

  • Delay & loss in packet-switched networks

  • Internet Structure

  • Transmission Media (self study)

  • History (self study)

CPSC 441: Introduction


Computer network l.jpg
Computer Network?

  • “interconnected collection of autonomous computers connected by a single technology” [Tanenbaum]

  • What is the Internet?

    • “network of networks”

    • “collection of networks interconnected by routers”

    • “a communication medium used by millions”

    • Email, chat, Web “surfing”, streaming media

  • Internet Web

CPSC 441: Introduction


The nuts and bolts view of the internet l.jpg

millions of connected computing devices: hosts, end-systems

PCs workstations, servers

PDAs phones, toasters

running network apps

communication links

fiber, copper, radio, satellite

Links have different bandwidth

routers: forward packets

Packet: a piece of messg.

router

workstation

server

mobile

local ISP

regional ISP

company

network

The “nuts and bolts” view of the Internet

CPSC 441: Introduction


Roadmap5 l.jpg
Roadmap

  • What is a Computer Network?

  • Applications of Networking

  • Classification of Networks

  • Layered Architecture

  • Network Core

  • Delay & loss in packet-switched networks

  • Internet Structure

  • Transmission Media (self study)

  • History (self study)

CPSC 441: Introduction


Applications 1 l.jpg

end systems (hosts):

run application programs

e.g. Web, email

at “edge of network”

client/server model

client host requests, receives service from always-on server

e.g. Web browser/server; email client/server

Client/server model is applicable in an intranet.

Applications (1)

CPSC 441: Introduction


Applications 2 l.jpg
Applications (2)

  • peer-peer model:

    • No fixed clients or servers

    • Each host can act as both client & server

  • Examples: Napster, Gnutella, KaZaA

CPSC 441: Introduction


Applications 3 l.jpg
Applications (3)

  • WWW

  • Instant Messaging (Internet chat, text messaging on cellular phones)

  • Peer-to-Peer

  • Internet Phone

  • Video-on-demand

  • Distributed Games

  • Remote Login (SSH client, Telnet)

  • File Transfer

CPSC 441: Introduction


Cool appliances l.jpg
“Cool” Appliances

IP picture frame

http://www.ceiva.com/

Web-enabled toaster+weather forecaster

World’s smallest web server

http://www-ccs.cs.umass.edu/~shri/iPic.html

CPSC 441: Introduction


Roadmap10 l.jpg
Roadmap

  • What is a Computer Network?

  • Applications of Networking

  • Classification of Networks

  • Layered Architecture

  • Network Core

  • Delay & loss in packet-switched networks

  • Internet Structure

  • Transmission Media (self study)

  • History (self study)

CPSC 441: Introduction


A classification of networks l.jpg
A Classification of Networks

  • Local Area Network (LAN)

  • Metropolitan Area Network (MAN)

  • Wide Area Network (WAN)

  • Wireless LANs & WANs

  • Home Networks

CPSC 441: Introduction


Local area network lan l.jpg

company/univ local area network (LAN) connects end system to edge router

Ethernet:

shared or dedicated link connects end system and router

10 Mbs, 100Mbps, Gigabit Ethernet

deployment: institutions, home LANs happening now

LANs: chapter 5

Local Area Network (LAN)

CPSC 441: Introduction


Metropolitan area network man l.jpg
Metropolitan Area Network (MAN)

A Cable TV Network is an example of a MAN

Typically 500 to 5,000 homes

cable headend

home

cable distribution

network (simplified)

CPSC 441: Introduction


Cable network architecture overview l.jpg
Cable Network Architecture: Overview

cable headend

home

cable distribution

network (simplified)

CPSC 441: Introduction


Cable network architecture overview15 l.jpg

server(s)

Cable Network Architecture: Overview

cable headend

home

cable distribution

network

CPSC 441: Introduction


Wide area network wan l.jpg

Spans a large geographic area, e.g., a country or a continent

A WAN consists of several transmission lines and routers

Internet is an example of a WAN

Wide Area Network (WAN)

CPSC 441: Introduction


Wireless networks l.jpg

shared continentwireless access network connects end system to router

via base station aka “access point”

wireless LANs:

802.11b (WiFi): 11 Mbps

wider-area wireless access

provided by telco operator

3G ~ 384 kbps

Will it happen??

WAP/GPRS in Europe

To the wired network

router

base

station

mobile

hosts

Wireless Networks

CPSC 441: Introduction


Home networks l.jpg

Typical home network components: continent

ADSL or cable modem

router/firewall/NAT

Ethernet

wireless access

point

Home networks

wireless

laptops

to/from

cable

headend

cable

modem

router/

firewall

wireless

access

point

Ethernet

(switched)

CPSC 441: Introduction


Internetworking l.jpg
“internetworking”? continent

  • internetwork – interconnection of networks – also called an “internet”

  • Subnetwork – a constituent of an internet

  • Intermediate system – a device used to connect two networks allowing hosts of the networks to correspond with each other

    • Bridge

    • Routers

  • Internet is an example of an internetwork.

CPSC 441: Introduction


Roadmap20 l.jpg
Roadmap continent

  • What is a Computer Network?

  • Applications of Networking

  • Classification of Networks

  • Layered Architecture

  • Network Core

  • Delay & loss in packet-switched networks

  • Internet Structure

  • Transmission Media (self study)

  • History (self study)

CPSC 441: Introduction


Layered architecture why l.jpg
Layered Architecture: Why? continent

  • Networks are complex with many pieces

    • Hosts, routers, links, applications, protocols, hardware, software

  • Can we organize it, somehow?

  • Let’s consider a Web page request:

    • Browser requests Web page from server

    • Server should determine if access is privileged

    • Reliable transfer page from server to client

    • Physical transfer of “bits” from server to client

CPSC 441: Introduction


Motivation continued l.jpg

Application continent

Services

Application

Services

Communication

Service

Communication

Service

Network

Services

Network

Services

Motivation Continued …

Application logic

Reliable delivery

Transfer “bits”

Web Client

Web Server

CPSC 441: Introduction


Motivation continued23 l.jpg
Motivation Continued … continent

Dealing with complex systems:

  • explicit structure allows identification, relationship of complex system’s pieces

    • layered reference model for discussion

  • modularization eases maintenance, updating of system

    • change of implementation of layer’s service transparent to rest of system

    • e.g., change in gate procedure doesn’t affect rest of system

  • layering considered harmful?

CPSC 441: Introduction


Layers protocols interfaces l.jpg

Application continent

Services

Application

Services

Communication

Service

Communication

Service

Network

Services

Network

Services

Layers, Protocols, Interfaces

Application logic

protocol

Layer

Interface

Reliable delivery

protocol

Layer

Interface

Transfer “bits”

protocol

Web Server

Web Client

CPSC 441: Introduction


Reference models l.jpg
Reference Models continent

  • Open Systems Interconnection (OSI) Model

  • TCP/IP Model

CPSC 441: Introduction


Reference models 2 l.jpg
Reference Models (2) continent

CPSC 441: Introduction


Internet protocol stack l.jpg

application: continent supporting network applications

FTP, SMTP, STTP

transport: host-host data transfer

TCP, UDP

network: routing of datagrams from source to destination

IP, routing protocols

link: data transfer between neighboring network elements

PPP, Ethernet

physical: bits “on the wire”

application

transport

network

link

physical

Internet protocol stack

CPSC 441: Introduction


Layering logical communication l.jpg

Each layer: continent

distributed

“entities” implement layer functions at each node

entities perform actions, exchange messages with peers

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

Layering: logical communication

CPSC 441: Introduction


Layering logical communication29 l.jpg

E.g.: transport continent

take data from app

add addressing, reliability check info to form “datagram”

send datagram to peer

wait for peer to ack receipt

analogy: post office

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

data

data

data

ack

Layering: logical communication

transport

transport

CPSC 441: Introduction


Layering physical communication l.jpg

network continent

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

data

data

Layering: physical communication

CPSC 441: Introduction


Protocol layering and data l.jpg

M continent

M

H

H

H

H

H

H

H

H

H

H

H

H

t

t

t

n

l

n

l

t

n

t

n

t

M

M

M

M

application

transport

network

link

physical

application

transport

network

link

physical

M

M

Protocol layering and data

Each layer takes data from above

  • adds header information to create new data unit

  • passes new data unit to layer below

source

destination

message

segment

datagram

frame

CPSC 441: Introduction


To be continued l.jpg
To be Continued … continent

  • What is a Computer Network?

  • Applications of Networking

  • Classification of Networks

  • Layered Architecture

  • Network Core

  • Delay & loss in packet-switched networks

  • Internet Structure

  • Transmission Media (self study)

  • History (self study)

CPSC 441: Introduction


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