Overview 1-1

Lec 1: Internet Overview

ECE5650

Overview 1-2

Intenet

Physical Connectivity Topology Access network and physical media

Layered Internet Protocol Stack History

Overview 1-3

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

millions of connected computing devices: hosts = end systems

running network apps communication links

fiber, copper, radio, satellite

transmission rate = bandwidth

routers: forward packets (chunks of data)

local ISP

companynetwork

regional ISP

router workstation

servermobile

Overview 1-4

What’s the Internet: a service view Distributed applications:

Web, email, games, e-commerce, file sharing

Network protocols: used by applications to control sending, receiving of msgs: TCP, IP, HTTP, FTP, PPP Internet standards

• RFC: Request for comments• IETF: Internet Engineering Task

Force

Communication services provided to apps: Connectionless unreliable connection-oriented reliable

Overview 1-5

A closer look at network structure: network edge:

applications and hosts network core:

routers network of networks

access networks, physical media: communication links

Overview 1-6

The network edge: end systems (hosts):

run application programs e.g. Web, email at “edge of network”

Programs in end-systems use the serivce of the Internet to send msgs to each other client/server model

• client host requests, receives service from always-on server; e.g. web, email

peer-peer model:• minimal (or no) use of dedicated

servers• e.g. Gnutella, KaZaA, Skype, BitTorrent

Overview 1-7

The Network Core

Physical connectivity of local area networks mesh of interconnected

routers Logical connectivity:

how is data transferred through net?

Overview 1-8

Internet structure: network of networks

roughly hierarchical at center: “tier-1” ISPs or Internet backbone

networks (e.g., MCI, Sprint, AT&T, Cable and Wireless), national/international coverage, connect to large tier-2 ISPs and to all tier-1 ISPs and many customer networks.

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).

Overview 1-9

Commercial Internet ISP Connectivity Roughly hierarchical

Divided into tiers Tier-1 ISPs are also called

backbone providers, e.g., AT&T, Sprint, UUNet, Level 3, Qwest, Cable & Wireless

An ISP runs (private) Points of Presence (PoP) where its customers and other ISPs connect to it

E.g., MCI has 4,500 PoP called private peering

ISPs also connect at (public) Network Access Point (NAP)

called public peering

Overview 1-10

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

NAPs (Network Access Points) are complex high-speed switching networks often concentrated at a single building. Operated by 3rd party telecom or Internet backbone ISP-1.

PoPs (Points of Presence) are private group of routers within each ISP and used to connect it (peer it) with other up/down/equal ISPs and is the new trend in connectivity.

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 public NAPs or private POPs.

Overview 1-11

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

Overview 1-12

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

Introduction 1-13

Tier-1 ISP: e.g., Sprint

Overview 1-14

ATT Global Backbone IP Network

From http://www.business.att.com

Overview 1-15

MichNet: Statewide Backbone Nation’s longest-

running regional network

An 2.5 Gigabit (OC48c) backbone, with 24 backbone nodes

Two diverse 2.5 gigabit (2x OC48) to chicago

www.merit.edu/mn

Overview 1-16

Overview 1-17

Intenet

Physical Connectivity Structure Access network and physical media

Layered Internet Protocol Stack History

Overview 1-18

Access networks and physical media

Q: How to connect end systems to edge router?

residential access nets institutional access

networks (school, company)

mobile access networks

Keep in mind: bandwidth (bits per

second) of access network?

shared or dedicated?

Overview 1-19

Residential access: point to point access

Dialup via modem Uses existing telephony infrastructure; Home is

connected to central office up to 56Kbps direct access to router (often less) Can’t surf and phone at same time: can’t be

“always on”

telephonenetwork Internet

homedial-upmodem

ISPmodem(e.g., AOL)

homePC

central office

Overview 1-20

ADSL: asymmetric digital subscriber line up to 1 Mbps upstream (today typically < 256

kbps) up to 8 Mbps downstream (today typically < 1

Mbps) FDM: 50 kHz - 1 MHz for downstream 4 kHz - 50 kHz for upstream 0 kHz - 4 kHz for ordinary telephone

telephonenetwork

DSLmodem

homePC

homephone

Internet

DSLAM

Existing phone line:0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream data

splitter

centraloffice

Overview 1-21

Residential access: cable modems

HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream,

2 Mbps upstream network of cable and fiber attaches homes

to ISP router homes share access to router so

communication activity is visible to each other.

deployment: available via cable TV companies

Overview 1-22

Residential access: cable modems

Diagram: http://www.cabledatacomnews.com/cmic/diagram.html

Overview 1-23

Cable Network Architecture: Overview

home

cable headend

cable distributionnetwork (simplified)

Typically 500 to 5,000 homes

Overview 1-24

Cable Network Architecture: Overview

home

cable headend

cable distributionnetwork (simplified)

Overview 1-25

Cable Network Architecture: Overview

home

cable headend

cable distributionnetwork

server(s)

Overview 1-26

Cable Network Architecture: Overview

home

cable headend

cable distributionnetwork

Channels

VIDEO

VIDEO

VIDEO

VIDEO

VIDEO

VIDEO

DATA

DATA

CONTROL

1 2 3 4 5 6 7 8 9

FDM:

Overview 1-27

Company access: local area networks

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

LANs: chapter 5

Overview 1-28

Wireless access networks

shared wireless access network connects end system to router via base station aka “access point”

wireless LANs: 802.11a/b/g (WiFi): 11 Mbps ~54Mbps 802.11n: 100~200Mbps (theoretically

up to 300Mbps) wider-area wireless access

provided by telco operator 3G ~ 384 kbps

• Will it happen?? WAP/GPRS in Europe

WiMAX ~100Mbps ~10 miles

basestation

mobilehosts

router

Introduction 1-29

Home networks

Typical home network components: DSL or cable modem router/firewall/NAT Ethernet wireless access point

wirelessaccess point

wirelesslaptops

router/firewall

cablemodem

to/fromcable

headend

Ethernet

Introduction 1-30

Physical Media

Bit: propagates betweentransmitter/rcvr pairs

physical link: what lies between transmitter & receiver

guided media: signals propagate in solid

media: copper, fiber, coax

unguided media: signals propagate freely,

e.g., radio

Twisted Pair (TP) two insulated copper

wires Category 3: traditional

phone wires, 10 Mbps Ethernet

Category 5: 100Mbps Ethernet

Introduction 1-31

Physical Media: coax, fiber

Coaxial cable: two concentric copper

conductors bidirectional baseband:

single channel on cable legacy Ethernet

broadband: multiple channels on

cable HFC

Fiber optic cable: glass fiber carrying

light pulses, each pulse a bit

high-speed operation: high-speed point-to-point

transmission (e.g., 10’s-100’s Gps)

low error rate: repeaters spaced far apart ; immune to electromagnetic noise

Introduction 1-32

Physical media: radio

signal carried in electromagnetic spectrum

no physical “wire” bidirectional propagation

environment effects: reflection obstruction by objects interference

Radio link types: terrestrial microwave

e.g. up to 45 Mbps channels

LAN (e.g., Wifi) 11Mbps, 54 Mbps

wide-area (e.g., cellular) 3G cellular: ~ 1 Mbps

satellite Kbps to 45Mbps channel

(or multiple smaller channels)

270 msec end-end delay geosynchronous versus low

altitude

Overview 1-33

Intenet

Physical Connectivity Topology Access network and physical media

Layered Internet Protocol Stack History

Overview 1-34

What’s a protocol?human protocols: “what’s the time?” “I have a question” introductions

network protocols: machines rather than

humans all communication

activity in Internet governed by protocols

A protocol is a set of rules that govens how two or more communicating parties are to interact. It defines:

- msg format- order of msgs sent & received- actions taken on msg transmission &

receipt

Protocol “Layers”

Networks are complex! many “pieces”:

hosts routers links of various

media applications protocols hardware,

software

Layered Protocol Modular approach to

network functionality

Examples:• Taking an airplane trip• Mailing service

Overview 1-35

Overview 1-36

Internet protocol stack application: supporting network

applications FTP, SMTP, HTTP

transport: process-process data transfer TCP, UDP

network: host-host data transfer IP

link: data transfer between neighboring network elements PPP, Ethernet

physical: bits “on the wire”

application

transport

network

link

physical

Overview 1-37

messagesegment

datagram

frame

sourceapplicatio

ntransportnetwork

linkphysical

HtHnHl M

HtHn M

Ht M

M

destination

application

transportnetwork

linkphysical

HtHnHl M

HtHn M

Ht M

M

networklink

physical

linkphysical

HtHnHl M

HtHn M

HtHnHl M

HtHn M

HtHnHl M HtHnHl M

router

switch

Encapsulation

Characteristics of Layering

Layering positives: Each layer relies on services from layer

below and exports services to layer above Interface defines interaction Hides implementation - layers can change

without disturbing other layers (black box)

Layering negatives: duplicate functionality and inter-dependency.

Overview 1-38

Overview 1-39

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

1972: ARPAnet

demonstrated publicly NCP (Network Control

Protocol) first host-host protocol

first e-mail program ARPAnet has 15 nodes

1961-1972: Early packet-switching principles

Overview 1-40

Initial ARPANET

1965-1968 ARPANET plan,

implemented by BBN (Bolt, Beranek, Newman): packet switch to build IMP

1969 ARPANET

commissioned: 4 nodes, 50kbps

Overview 1-41

Initial Expansion of the ARPANET

Dec. 1969 Mar. 1971July 1970

Apr. 1972 Sept. 1972RFC 527: ARPAWOCKY; RFC 602: The Stockings Were Hung by the Chimney with Care

Overview 1-42

Internet History

1970: ALOHAnet satellite network in Hawaii

1973: Metcalfe’s PhD thesis proposes Ethernet

1974: Cerf and Kahn – archi. for interconnecting networks Initially, named NCP Later, split to TCP/IP

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

2005 ACM Turing Award“A protocol for packet network

interconnection”, IEEE Trans. on Communications Technology, vol.22(5), 627-641

1972-1980: Internetworking, new and proprietary nets

Overview 1-43

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

Overview 1-44

Internet History

Early 1990’s: ARPAnet decommissioned

1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) 1992, 1 million hosts

early 1990s: Web hypertext [Bush 1945,

Nelson 1960’s] 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, peer2peer file sharing (e.g., BitTorrent, YouTube)

network security to forefront

Today: 400 million users, 150

countries backbone links running at

10 Gbps

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

Overview 1-45

Number of Hosts on the Internet:

Aug. 1981 213Oct. 1984 1,024Dec. 1987 28,174 Oct. 1990 313,000 Jul. 1993 1,776,000Jul. 1996 19,540,000Jul. 1999 56,218,000Jul. 2004 285,139,000Jan. 2005 317,646,000Jul. 2005 353,284,000 About 2B users out of 6.8B people,

from 16M in 1995, 350M in 2000,1B in 2005

Growth of the Internet

Overview 1-46

Summary

Physical Connectivity Topology Access network and physical media

Layered Internet Protocols History