Introduction 1-1

COSC6377: Computer Networks

Rong Zhengrzheng@cs.uh.edu

Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition. Jim Kurose, Keith RossAddison-Wesley, July 2004.

Introduction 1-2

Introduction

Overview of the course Basic concepts and structures in

computer networking Network architecture

Introduction 1-3

Computer Networks

A computer network is a system for communication among two or more computers What amounts to “computers”? What kind of communication? – “digital” System: both software & hardware Examples?

Our focus is on the Internet

Introduction 1-4

History of the Internet

61-72: development of packet switching 72-80: Proprietary networks and internetworking

Multiple packet switching networks “Networks of networks”: earlier development of TCP, UDP, IP ALOHA, Ethernet

80-90: proliferation of networks Standardization of networking protocols TCP/IP, DNS etc NSF builds NSFNET as backbone, links 6 Supercomputer

centers, 1.5 Mbps, 10,000 computers 90’s: Internet explosion

94: NSF backbone dismantled, multiple private backbones Emergence of World Wide Web (invented by Time Berners-Lee)

Introduction 1-5

Internet “Hall of Fame”

Al Gore, former vice president of USA Vinton G. Cerf and Robert E. Kahn

2004 Turing Award winner “For pioneering work on internetworking, including the design and implementation of the Internet's basic communications protocols, TCP/IP, and for inspired leadership in networking”

Turing lecture: http://www.acm.org/sigs/sigcomm/sigcomm2005/webcast.html

David Clark et al “end2end arguments” Van Jacobson, TCP congestion control Robert Metcalfe, inventor of Ethernet …

Introduction 1-6

Growth of the Internet

Number of Hosts on the Internet:

Aug. 1981 213Oct. 1984 1,024Dec. 1987 28,174 Oct. 1990 313,000 Oct. 1993 2,056,000Apr. 1995 5,706,000Jan. 1997 16,146,000Jan. 1999 56,218,000Jan. 2001 109,374,000Jan 2003 171,638,297

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10

100

1000

10000

100000

1000000

10000000

100000000

1000000000

19811984198719901993199619992002

Data available at: http://www.isc.org/

Introduction 1-7

Growth of the Internet

Traffic on Internet (in TB/mo)

1990 1.01991 2.01992 4.41993 8.31994 16.31996 1,5001997 2,500 - 4,0001998 5,000 - 8,0001999 10,000 - 16,0002000 20,000 - 35,0002001 40,000 - 70,0002002 80,000 - 140,000 1

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100

1000

10000

100000

1000000

1990

1992

1994

1997

1999

2001

Andrew Odlyzko, “Internet traffic growth: Sources and implications”

Introduction 1-8

Growth of the Internet

Internet bandwidth Nielsen’s law: 50% each year Projected

Introduction 1-9

Introduction 1-10

What is Next Big Thing?

I wish I have the answer Technology

Wireless broadband networks Optical switching networks (?)

Application VOIP Peer-to-peer applications Online gaming

• Sony’s EverQuest servers host 600,000 PC gamers

Introduction 1-12

What will be covered?

Network architecture, services, apps TCP/IP

Protocol details Algorithms Performance analysis

Ethernet, Wireless networks Multimedia networks

QoS scheduling Signaling

Network security Basic knowledge Attacks and counter-measures

Network management

Introduction 1-13

What will not be covered?

Socket programming (chap 2.7-2.9) Physical layer technologies (chap 1.4) Cellular networks Multicast routing (chap 4.7) ATM, frame relay, PPP (chap 5.7-5.8)

The emphasis is no only on “how” but also “why”

Knowledge base Reasoning behind the design

Introduction 1-14

Logistics

Textbook, reference book Office hour Homework, project policy Grade Prerequisite test:

What are the OSI-ISO layers? How is it related to the practice in the Internet?

What is protocol? What is the difference between packet

switching and circuit switching? Sockets

Introduction 1-15

Introduction

Overview of the course Basic concepts and structures in

computer networking Network architecture

Introduction 1-16

What’s the Internet: “nuts and bolts” view End systems

Host computer Network applications

Access networks Local area networks communication links

Network core: routers network of networks

local ISP

companynetwork

regional ISP

router workstation

servermobile

Introduction 1-17

What’s the Internet: “nuts and bolts” view Protocols control sending,

receiving of msgs e.g., TCP, IP, HTTP, FTP,

PPP

Internet: “network of networks” loosely hierarchical public Internet versus

private intranet

Internet standards RFC: Request for comments IETF: Internet Engineering

Task Force

local ISP

companynetwork

regional ISP

router workstation

servermobile

Introduction 1-18

Network Components (Examples)

Fibers

Coaxial Cable

Links Interfaces Switches/routers

Ethernet card

Wireless card

Large router

Switch

Introduction 1-19

Juniper Routers

Introduction 1-20

Internet structure: network of networks

roughly hierarchical at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T,

Cable and Wireless), national/international coverage treat each other as equals

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-1 providers interconnect (peer) privately

NAP

Tier-1 providers also interconnect at public network access points (NAPs)

Introduction 1-21

Tier-1 ISP: e.g., Sprint

Sprint US backbone network

Seattle

Atlanta

Chicago

Roachdale

Stockton

San Jose

Anaheim

Fort Worth

Orlando

Kansas City

CheyenneNew York

PennsaukenRelay

Wash. DC

Tacoma

DS3 (45 Mbps)OC3 (155 Mbps)OC12 (622 Mbps)OC48 (2.4 Gbps)

Introduction 1-22

Internet structure: network of networks

“Tier-2” ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet tier-2 ISP is customer oftier-1 provider

Tier-2 ISPs also peer privately with each other, interconnect at NAP

Introduction 1-23

Internet structure: network of networks

“Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems)

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP

Local and tier- 3 ISPs are customers ofhigher tier ISPsconnecting them to rest of Internet

Introduction 1-24

Internet structure: network of networks

a packet passes through many networks!

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP