CS 3830 Day 6 Introduction 1-1. Announcements Program 2 posted this afternoon (due date will be week of 9/24) Introduction 1-2.

CS 3830

Day 6

Introduction 1-1

Announcements

Program 2 posted this afternoon (due date will be week of 9/24)

Introduction 1-2

Introduction 1-3

The bad guys can use false source addresses

IP spoofing: send packet with false source address

Used in conjunction with DoS attacks What if hacker not on the same subnet?

A

B

C

src:B dest:A payload

Introduction 1-4

The bad guys can record and playback

record-and-playback: sniff sensitive info (e.g., password), and use later (man-in-the-middle) password holder is that user from system

point of view

A

B

C

src:B dest:A user: B; password: foosrc:C dest:A user: B; password: foo

Introduction 1-5

Network Security more throughout this course chapter 8: focus on security cryptographic techniques: obvious uses

and not so obvious uses

Introduction 1-6

Chapter 1: roadmap

1.1 What is the Internet?1.2 Network edge

end systems, access networks, links

1.3 Network core circuit switching, packet switching, network structure

1.4 Delay, loss and throughput in packet-switched networks

1.5 Protocol layers, service models1.6 Networks under attack: security1.7 History

Introduction 1-7

Internet History

1961: Kleinrock – queueing theory shows effectiveness of packet-switching

1964: Baran - packet-switching in military nets

1967: ARPAnet conceived by Advanced Research Projects Agency

1969: first ARPAnet node operational

Who had the first computer on the net?

1972: ARPAnet public

demonstration NCP (Network Control

Program) first host-host protocol

first e-mail program ARPAnet has 15 nodes

1961-1972: Early packet-switching principles

Introduction 1-8

Internet History

1970: ALOHAnet satellite network in Hawaii

1974: Cerf and Kahn - architecture for interconnecting networks

1976: Ethernet at Xerox PARC

late70’s: proprietary architectures: DECnet, SNA, XNA

late 70’s: switching fixed length packets (ATM precursor)

1979: ARPAnet has 200 nodes

Cerf and Kahn’s internetworking principles: minimalism, autonomy -

no internal changes required to interconnect networks

best effort service model stateless routers decentralized control

define today’s Internet architecture

1972-1980: Internetworking, new and proprietary nets

Introduction 1-9

Internet History

1983: deployment of TCP/IP

1982: smtp e-mail protocol defined

1983: DNS defined for name-to-IP-address translation

1985: ftp protocol defined

1988: TCP congestion control

new national networks: Csnet, BITnet, NSFnet, Minitel

100,000 hosts connected to confederation of networks

1980-1990: new protocols, a proliferation of networks

Introduction 1-10

Internet History

Early 1990’s: ARPAnet decommissioned

1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)

early 1990s: Web HTML, HTTP: Berners-Lee 1994: Mosaic, later

Netscape late 1990’s:

commercialization of the Web

Late 1990’s – 2000’s: more killer apps: instant

messaging, P2P file sharing

network security to forefront

est. 50 million+ hosts backbone links running at

Gbps

1990, 2000’s: commercialization, the Web, new apps

Introduction 1-11

Internet History

2007: ~500 million hosts Voice, Video over IP P2P applications:

BitTorrent, Skype, etc. more applications:

YouTube, gaming wireless, mobility

Current: ? Do some

research and find some interesting statistics

Introduction 1-12

Introduction: SummaryCovered a “ton” of material! Internet overview what’s a protocol? network edge, core,

access network packet-switching

versus circuit-switching Internet structure

performance: loss, delay, throughput

layering, service models security history

You now have: context, overview,

“feel” of networking more depth, detail

to follow!

2: Application Layer 13

Chapter 2: Application layer

2.1 Principles of network applications

2.2 Web and HTTP 2.3 FTP 2.4 Electronic Mail

SMTP, POP3, IMAP

2.5 DNS

2.6 P2P applications 2.7 Socket

programming with TCP 2.8 Socket

programming with UDP

2: Application Layer 14

Chapter 2: Application LayerOur goals: conceptual,

implementation aspects of network application protocols: transport-layer

service models client-server

paradigm peer-to-peer

paradigm

learn about protocols by examining popular application-level protocols: HTTP FTP SMTP / POP3 / IMAP DNS

programming network applications socket API (Java)

2: Application Layer 15

Chapter 2: Application layer

2.1 Principles of network applications

2.2 Web and HTTP 2.3 FTP 2.4 Electronic Mail

SMTP, POP3, IMAP

2.5 DNS

2.6 P2P applications 2.7 Socket

programming with TCP 2.8 Socket

programming with UDP

2.9 Building a Web server

2: Application Layer 16

Application architectures

Client-server Peer-to-peer (P2P) Hybrid of client-server and P2P

2: Application Layer 17

Client-server architecture

server: always-on host permanent IP address server farms for

scalingclients:

communicate with server may be intermittently

connected may have dynamic IP

addresses do not communicate

directly with each other

client/server

2: Application Layer 18

Pure P2P architecture

no always-on server arbitrary end systems

directly communicate peers are

intermittently connected and change IP addresses

Highly scalable but difficult to manage

peer-peer

2: Application Layer 19

Hybrid of client-server and P2PSkype

voice-over-IP P2P application centralized server: finding address of

remote party: client-client connection: direct (not through

server) Instant messaging

chatting between two users is P2P centralized service: client presence

detection/location• user registers its IP address with central

server when it comes online• user contacts central server to find IP

addresses of buddies

2: Application Layer 20

Processes communicating

Process: program running within a host.

within same host, two processes communicate using inter-process communication (defined by OS).

processes in different hosts communicate by exchanging messages

Client process: process that initiates communication

Server process: process that waits to be contacted

Note: applications with P2P architectures have client processes & server processes