Information Technology in Theory By Pelin Aksoy and Laura DeNardis

Chapter 14 Internet Architecture

Objectives

• Become familiar with important Internet technology milestones • Understand fundamental Internet architectural features such as Internet exchange points, the Domain Name System, IP addresses, and Uniform Resource Locators • Understand the technology underlying popular Internet applications Information Technology in Theory 2

Objectives (continued)

• Examine the centralized administrative functions that keep the Internet running, including management of domain names and Internet addresses • Contemplate economic and social issues associated with the Internet Information Technology in Theory 3

Internet History

• The cold war • Launch of Sputnik in 1957 • ARPA founded within the Department of Defense (DoD) • ARPANET • Packet switching by Paul Baran • TCP/IP by Vinton Cerf and Robert Kahn • The World Wide Web Information Technology in Theory 4

Internet History (continued)

• Web browser Mosaic by Marc Andreessen • Wireless access • Etc.

Information Technology in Theory 5

Internet History (continued)

Information Technology in Theory 6

Internet Architectural Components

• The Internet includes the following important technological systems and components: – Internet backbone and routers – Internet exchange points (IXPs) – The Internet Protocol (IP) – The Domain Name System (DNS) – Uniform Resource Locators (URLs) Information Technology in Theory 7

Internet Backbone and Routers

•

Internet backbone

: the global collection of high capacity trunks • Is not owned and operated by any single company or government • Rather, it is a collection of high-speed, interconnected networks run by large

network service providers

such as AT&T, British Telecom, France Telecom, Qwest, and Verizon, etc.

Information Technology in Theory 8

Internet Backbone and Routers (continued)

• The foundation of the Internet’s architecture is an enormous number of routers • The router reads the destination IP address and uses a

routing table

to look up information for how to forward the packet • A routing table is essentially a database on the router that provides information for how destinations can be reached most efficiently Information Technology in Theory 9

Internet Backbone and Routers (continued)

• The routers in one service provider’s networks can communicate with routers in other such networks because they adhere to the same

routing protocols

• These protocols enable routers to share network changes that are reflected in updates to router tables • An example of a routing protocol that provides this service is

Border Gateway Protocol

(BGP) Information Technology in Theory 10

Internet Backbone and Routers (continued)

Information Technology in Theory 11

Internet Exchange Points

• Traffic from one network flows seamlessly to other networks across the Internet through interconnection locations called

Internet exchange points

(IXPs) • The exchange point serves as a juncture at which packets from different networks are exchanged and routed toward their appropriate destinations Information Technology in Theory 12

Internet Exchange Points (continued)

•

Peering agreements

allow service providers to share the costs of shared exchange points and provide service-level agreements for characteristics such as reliability and latency, the delay that packets undergo en route to a destination Information Technology in Theory 13

Internet Exchange Points (continued)

Information Technology in Theory 14

The Internet Protocol

• The

Internet Protocol

(IP) is a critical part of TCP/IP and the circulatory system of the Internet in many ways • IP is the one protocol needed in almost every instance of information sharing over the Internet • The function of IP is to route blocks of information from a source to a destination over a complex network Information Technology in Theory 15

The Internet Protocol (continued)

• To perform this routing, IP uses a hierarchical addressing scheme that assigns a hardware independent (logical rather than physical) address to every device connected to the Internet • Recall that the IP address is software defined; it is distinct from a MAC address that is physically associated with a LAN adapter such as an Ethernet card Information Technology in Theory 16

IP Addresses

• Each device that communicates over the Internet must use a unique address known as an

IP address

• The traditional standard for IP addresses, called

IPv4

(IP Version 4), specifies 32 bits for each address • An IP address is a combination of 32 ones and zeros such as the following: 01011110000101001100001111011100 Information Technology in Theory 17

IP Addresses (continued)

• Industry convention dictates a shorthand method,

dotted decimal format

, for discussing and managing IP addresses • For example, an IP address in dotted decimal format might be 94.20.195.220

• The Internet address length of 32 bits theoretically provides 4,294,967,296 (calculated as 2 32 ) unique addresses Information Technology in Theory 18

IP Addresses (continued)

• As the Internet grew internationally and new applications such as wireless Internet access and Internet telephony emerged, the Internet Engineering Task Force (IETF) identified the possibility that the reserve of Internet addresses might be exhausted • The need for more global Internet addresses was recognized in the early 1990s Information Technology in Theory 19

IP Addresses (continued)

• The IETF engineered two initial technical approaches to conserving Internet addresses: – Classless Interdomain Routing (CIDR), which eliminated the Class A, B, and C distinctions – Network Address Translation (NAT), a technique that allowed a network device such as a router to share a limited number of public IP addresses among many devices on a private network • When a computing device on a private network accesses the Internet, NAT dynamically allocates a globally unique, temporary, public IP address for transmission over the public Internet Information Technology in Theory 20

IP Addresses (continued)

Information Technology in Theory 21

IPv6

• In addition to these address conservation strategies, the IETF selected a new standard, now called

IPv6

(Internet Protocol Version 6), to exponentially expand the number of globally unique addresses • Shorthand notation based on the Hex system • Example of an IPv6 address in Hex shorthand notation: – FDDC:AC10:8132:BA32:4F12:1070:DD13:6921 Information Technology in Theory 22

IPv6 (continued)

• FDDC = 1111110111011100 • AC10 = 1010110000010000 • 8132 = 1000000100110010 • BA32 = 1011101000110010 • 4F12 = 0100111100010010 • 1070 = 0001000001110000 • DD13 = 1101110100010011 • 6921 = 0110100100100001 • IPv6 deployment is occurring more rapidly in Asia and other countries than in the United States Information Technology in Theory 23

The Domain Name System

• Even the shorthand dotted decimal format, which was designed to make IP addresses less unwieldy, is difficult to remember and use • Fortunately, Internet users do not have to remember numeric IP addresses while using the Internet – Instead, users can employ alphanumeric names that are easy to remember, such as

www.yale.edu

. • These are known as domain names Information Technology in Theory 24

The Domain Name System (continued)

• Each domain name has an associated IP address • Example of a domain name and an associated IP address:

cnn.com 64.236.29.120

• The DNS is like a hierarchical tree; the suffix, which is the component at the far right of any domain name, is called the top-level domain (

TLD

) Information Technology in Theory 25

The Domain Name System (continued)

• .com (for commercial businesses) • .org (for nonprofit organizations) • .edu (for educational institutions) • .gov (for the U.S. government) • .mil (for the U.S. military) • .net (for networks) • .int (for international entities) Information Technology in Theory 26

The Domain Name System (continued)

Information Technology in Theory 27

The Domain Name System (continued)

• Within a domain name, the word to the left of the top level domain is called a second-level domain • Domain names can also have third- and fourth-level domains • A method is needed to translate between alphanumeric domain names and the associated IP addresses required for routing information across the Internet • This translation is called

address resolution

and is performed by the DNS Information Technology in Theory 28

The Domain Name System (continued)

• An important architectural component of the Internet is its collection of

root name servers

, which are usually just called root servers • These servers maintain a master file, called the

root zone file

, that lists the names and IP addresses of the official DNS servers for all TLDs Information Technology in Theory 29

The Domain Name System (continued)

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Uniform Resource Locators

• A URL is a string of characters associated with a specific information resource, such as

www.ebay.com

,

www.gmu.edu

, and so on • Many URLs relate to Web access via HTTP, but note that URLs also apply to many other Internet protocols and information resources • Instead of “http,” the first part of a URL could include “ftp” for File Transfer Protocol, “news” for Usenet news, or other Internet resource types Information Technology in Theory 31

Uniform Resource Locators (continued)

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Internet Applications

• At one point, the Internet primarily allowed file sharing and electronic mail • Over time, Internet applications have expanded to the World Wide Web, text messaging, Internet telephony, multimedia file sharing, and much more Information Technology in Theory 33

E-Mail

• E-mail is a

store and forward system

that does not require the simultaneous online presence of senders and receivers • The

de facto

messaging protocol that historically has supported Internet e-mail is

SMTP

, or Simple Mail Transfer Protocol • Today messages incorporate multimedia and include attachments, thanks to newer messaging formats such as

MIME

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E-Mail (continued)

• The arrival of e-mail at a local server and its transmission from the remote server to the recipient are separate transactions that use different sets of communications protocols, known as mail retrieval protocols –

Post Office Protocol

(POP) –

Internet Message Access Protocol

(IMAP) Information Technology in Theory 35

E-Mail (continued)

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Messaging

• Unlike e-mail, text messaging generally requires both users to be online or on their mobile phones simultaneously • When you send a text message to a recipient, a window opens and displays the message on the recipient’s computing device Information Technology in Theory 37

The World Wide Web

• The Web was a revolutionary advancement over previous data-sharing tools for several reasons: – It allows many users to simultaneously access the same information – It provides hyperlinked information—clicking a textual link takes a user to another location – It combines multimedia information such as video, text, image, and sound Information Technology in Theory 38

The World Wide Web (continued)

• The Web was a revolutionary advancement over previous data-sharing tools for several reasons (continued): – It allows access to anyone connected to the Internet from any computing platform – It provides searchable information – Anyone can develop their own information site and inexpensively make it available to millions of people Information Technology in Theory 39

The World Wide Web (continued)

• The WWW uses a standard network protocol, Hypertext Transfer Protocol (

HTTP

), to establish and maintain communications over the Internet between a computer user (client) and a Web site (server) • Web interactions also require the encoding of information in a standard format called Hypertext Markup Language (

HTML

) or eXtensible Markup Language (

XML

) Information Technology in Theory 40

The World Wide Web (continued)

Information Technology in Theory 41

File Sharing and P2P

• The TCP/IP suite has historically provided a specific protocol to enable file sharing over the Internet: FTP, or File Transfer Protocol • As Internet technologies have grown, file sharing has expanded to include stored videos, audio files, and images • P2P file sharing was realized through music- and video-sharing systems • Rather than storing files on a server or large database management system, P2P technologies distribute files that are stored on the hard drives of individual users Information Technology in Theory 42

File Sharing and P2P (continued)

• P2P file sharing of any copyrighted information, including music and movies, is illegal though widespread • A series of well-publicized lawsuits, especially those brought by the Recording Industry Association of America (RIAA), have attempted to curtail downloading of copyrighted information • However, countless applications of P2P network technology are legal and hold great promise for efficiently sharing information Information Technology in Theory 43

File Sharing and P2P (continued)

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Internet Telephony

• VoIP is a cost-effective alternative to traditional telephone service and has quickly become a major Internet application • The main advantage of Internet telephony is that telephone calls are virtually free to users who already pay for an Internet connection Information Technology in Theory 45

Internet Broadcasting

• The advantage of “simulcasting” over the Internet is that the broadcast has no physical or geographical limitation • A radio station can easily broadcast over the Internet and reach a worldwide audience at very little cost without having to contend with spectrum limitations and regulations Information Technology in Theory 46

Internet Administration

• Does anyone run the Internet? • Who is in charge of the many administrative functions and standards setting that keep the Internet up and running? • The success of the Internet as an interoperable, universal communications medium requires common, compatible standards Information Technology in Theory 47

Administration of Internet Names and Numbers

• If connecting to the Internet requires an IP address, and if each address must be globally unique, someone has to be responsible for allocating and administering these resources • The IANA, under the auspices of the Internet Corporation for Assigned Names and Numbers (

ICANN

), still has centralized responsibility for the IP address space, including both IPv4 and IPv6 • The IANA, in turn, allocates large blocks of addresses to regional Internet registries (RIRs) and national Internet registries (NIRs) Information Technology in Theory 48

Administration of Internet Names and Numbers (continued)

• In 1998, the U.S. Department of Commerce issued a white paper calling for the creation of a private, nonprofit corporation to administer these names • This new entity became ICANN • The greatest controversy over ICANN has involved the questions of who should make these policy decisions and have the authority to allocate IP addresses Information Technology in Theory 49

Internet Standards Setting

• The IETF establishes common network technical specifications and standards for the Internet • The Internet standards process is complex, and involves the proposal of a draft standards specification followed by a period of iterative revision by a “working group” that anyone can join Information Technology in Theory 50

Internet Standards Setting (continued)

• Technical specifications step through a progressive approval process that begins with the designation of a proposed standard, evolves to a draft standard, and culminates in a standard • The World Wide Web Consortium (W3C) develops Web specifications • The Institute of Electrical and Electronics Engineers (IEEE) establishes Internet-related LAN standards such as the Wi-Fi specifications Information Technology in Theory 51

Internet Open Issues

• The Internet has been accompanied by a host of economic and social policy questions: – Should online sales be taxed?

– Should voice services that use Internet telephony (VoIP) be regulated and taxed, like other more traditional services?

– How might a major Internet outage or cyberterrorist attack affect nations economically?

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Internet Open Issues (continued)

• Some countries restrict or prohibit Internet access for political or religious reasons – Whose laws should apply, and how should they apply to a network that transcends national boundaries?

– In what ways will the Internet intersect with politics?

– What are the ramifications of the international digital divide, in which some countries have widespread Internet access and computing resources, and others have limited resources?

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Net Neutrality

•

Net neutrality

Internet is a phrase that has received a great deal of attention in the early twenty-first century • Net neutrality has several meanings, but it generally refers to the principle of nondiscrimination on the • According to the Net neutrality principle, a cable company that controls a residential broadband connection should not be able to serve as a gatekeeper that makes certain content more readily available to consumers Information Technology in Theory 54

Net Neutrality (continued)

• Those who oppose Net neutrality legislation argue that the Internet’s architecture is not neutral already, because of how content is presented by search companies and because of the tiered service-level pricing offered by service providers Information Technology in Theory 55

Net Neutrality (continued)

• Opponents also note that engineering quality of service (QoS) prioritization is necessary on an application basis so that latency-sensitive applications such as video and voice are given a higher transmission priority than information that is not as time sensitive, such as data Information Technology in Theory 56

Summary

• The Internet is not a single network or technology, but a collection of systems that can interconnect because they use common TCP/IP and routing protocols and common architectural approaches such as packet switching • Different service provider networks interconnect at locations called IXPs – Peering agreements dictate how they share costs and provide acceptable performance Information Technology in Theory 57

Summary (continued)

• The use of IP is arguably the defining architectural characteristic of being “on the Internet” • Devices that are connected to the Internet require an Internet address—either a 32-bit address under the IPv4 standard or a 128-bit address under the newer IPv6 standard • The DNS is a hierarchical, distributed database management system that performs the important task of address resolution Information Technology in Theory 58

Summary (continued)

• Internet applications are constantly evolving, but they fall into the broad categories of e-mail, messaging, the Web, file sharing, telephony, and Internet broadcasting • The Internet requires centralized administrative coordination, such as managing the IP address space and establishing standards Information Technology in Theory 59