MD703

Internet & Telecom Basics

How the Net Works

Key Technologies

IP Telephony

Solving the Last Mile Problem

Speed & Ubiquity Developments

What is the Internet?• A Network of Networks

– TCP/IP - standard protocol for routing & transport

• A medium of exchanging all form of digital data– text, graphics, audio, video, programs, faxes

• An infrastructure for various services– e-mail (electronic mail)– WWW (world wide web)– FTP (file transfer protocol)– UseNet newsgroups, PointCast,

games, EDI, etc.

Transmission Speeds• Bandwidth

– measure of transmission speed / capacity

• Bits & Bytes– bit - smallest form of computer memory - 1 or 0– byte - 8 bits, roughly 1 character (Latin alphabet)

• How do we measure speeds?– bps - bits per second– Kbps - kilobit, thousands of bits per second– Mbps - megabit, millions of bits per second– Gbps - gigabit, billions of bits per second

How Many People Use the Net?• We don’t know• Nua’s best guess - about 201 million at 9/99• Breakdown:

Source: nua.ie, Sept. 99

Region Users (millions)Canada & USA 112.4 millionEurope 47.15 millionAsia/Pacific 33.61 millionLatin America 5.29 millionAfrica 1.72 millionMiddle East 0.88 million

Anatomy of a URL

• URL– Uniform Resource Locator (web address)

http://www2.bc.edu/~gallaugh/directory/file.html

application protocol(http is assumed by current browsers).Others: FTP, NNTP

host computer(others@ BC:agora,www)

domain name,top level domain

user ID

directory file

case sensitive

The DNS & IP Addresses

• IP Address– Unique number identifying Internet computers. Expressed as four

numbers between 0 and 255.– ex: infoeagle.bc.edu = 136.167.2.241 (32 bit address)– IPv6: 128 bit addressing, more efficient/faster, secure

• DNS - Domain Name Service– A distributed database used to translate domain names, into

Internet Protocol (IP) Addresses.

• Registry of an Internet domain name:– currently in the US for $70 for two years (www.internic.net)

Network Interconnectionsdial-in

users (56.6 Kbps)dormusers

officeusers

dorm LAN office LANmodem pool

web serverwww2.bc.edu

BC Campus Network Backbone (10 Mbps)(IP #s 136.167.xxx.xxx domain)

Internet Leased Line through CW (4.5 Mbps, $8k/mo.)

The Internet

local ISPmicrosoft.comwhitehouse.gov

TCP/IP

• TCP/IP - the Internet’s common language

• TCP - Transmission Control Protocol. Breaks up transmissions (e-mail messages, web pages, etc.) into packets of no more than about 1500 characters each, checks the integrity of incoming packets, and reassembles packets on the other end

• IP - Internet Protocol. Routes packets.

Packet Traffic

• What’s in a packet?– source address– destination address– error checking (checksum)– time to live– options (timestamp, record route, etc.)– your data!

A Packet Switched Network at Work

E-mail message:

Prof. Gallaugher,I just wanted to let you know that I got a job based on the stuff I learned in your class...

packet1

packet2

packet3

E-mail message:

Prof. Gallaugher,I just wanted to let you know ...

packet2

packet1

packet3

packet1

packet2

packet3

packet2

packet3

R

R

R R

R

R = router

US Internet Infrastructure

Source: lbrandt@nsf.govWatch Cable & Wireless’s backbone traffic at:traffic.cwusa.com

TraceRoute from BC to Hawaii1 cs7513-honolulu.aloha.net (204.94.112.38)

1.481 ms 1.084 ms 0.942 ms2 207.170.197.201 (207.170.197.201) 72.109 ms 71.315

ms 73.781 ms3 sl-gw4-sea-5-0-T3.sprintlink.net (144.228.96.9)

75.242 ms 79.062 ms 77.557 ms4 sl-bb1-sea-0-0.sprintlink.net (144.228.90.1) 79.245

ms 74.64 ms 75.174 ms5 core2-hssi3-0.Seattle.mci.net (206.157.77.153)

76.262 ms 75.853 ms 77.16 ms6 bordercore1.Boston.mci.net (166.48.60.1) 145.921 ms

142.257 ms 142.892 ms7 boston-college.Boston.mci.net (166.48.62.14) 154.438

ms 148.711 ms 151.135 ms8 Infoeagle.bc.edu (136.167.2.146) 150.337 ms 149.579

ms 154.07 ms

1 be102 (169.226.4.1) 2 ms 1 ms 1 ms2 at-gw3-alb-1-0-T3.nysernet.net (169.130.23.5) 2 ms 3 ms 2

ms3 at-gw2-alb-0-0.nysernet.net (169.130.20.2) 2 ms 3 ms 3 ms4 at-gw1-syr-1-0-T3.nysernet.net (169.130.1.22) 6 ms 4 ms 4

ms5 at-gw1-ith-0-0-T3.nysernet.net (169.130.1.42) 7 ms 7 ms 7

ms6 at-gw2-ith-0-0.nysernet.net (169.130.60.2) 7 ms 7 ms 7 ms7 at-bb1-pen-5-0-0-T3.nysernet.net (169.130.1.121) 20 ms 20 ms

20 ms8 sl-bb6-pen-6-0-0.sprintlink.net (144.228.60.21) 21 ms 23 ms

20 ms9 core4-hssi5-0.WestOrange.mci.net (206.157.77.105) 25 ms 26

ms 25 ms10 bordercore1.Boston.mci.net (166.48.60.1) 317 ms 54 ms 110

ms11 boston-college.Boston.mci.net (166.48.62.14) 36 ms 37 ms

36 ms12 Infoeagle.bc.edu (136.167.2.146) 36 ms 37 ms 36 ms

TraceRoute from BC to Albany, NY

TCP vs. UDP

TCP - perfect transmission is critical (e.g. e-mail)TCP will request packets that are lost or

damaged

The Internet

UDP - low latency is critical (e.g. RealAudio, Video, packet streaming)Latency matters - UDP will ignore packets that

don’t arrive on time or in good shape

The Internet

UDP = User Datagram Protocol

Circuit vs. IP TelephonyCircuit Switching

Internet Telephony (e.g. Net2Phone)

IP Telephony over Private Networks (e.g. Qwest)

64 Kbps circuit, guaranteed QoS (quality of service)

packets over the Internet, variable QoS

packets over private network, improved QoS

The Internet

Private IP Network

Transmission Speeds• The last mile problem

– access to many consumers & businesses may be slow (e.g. 28.8 Kbps modem speeds)

• The contenders– faster modems - (at ISP and user end; 56 Kbps)– ISDN - (e.g. BellAtlantic; up to 128 Kbps)– GEO Satellite (e.g. DirectDuo; 400 Kbps download)– LMDS (e.g. CellularVision; 500 Kbps download)– Cable Modems (e.g. MediaOne; 1.5 Mbps download)– ADSL (e.g. AmeriTech; 1.5 - 7 Mbps download)

Bandwidth Bonanza(download speeds only)

1,500

1,500

500

400

128

56

28.8

0 200 400 600 800 1,000 1,200 1,400 1,600

ADSL (Ameritech)

Cable Modem (MediaOne)

LMDS (CellularVision)

DBS (DirectDuo)

Bonded ISDN

56 Kbps

28.8 Kbps

Satellite Schemes• GEO

– Spaceway from Hughes (2003, 2-6 Mbps)

• LEO– Teledesic

(2004, 2 to 64 Mbps)

Graphic from Byte

Fostering Speed & Ubiquity

• Caching servers– get content closer to customers– e.g. Akamai, Inktomi, Digital Island

• Dense Wave Division Multiplexing– prisms split fiber optic signal

• Wireless Access– WAP, i-mode, emerging 3G standards

• Integration of Wireless Devices– Bluetooth