A Discussion on The Internet

Georgios EllinasDepartment of Electrical and Computer Engineering

University of Cyprus

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Outline

What is the Internet?History of the InternetEvolution of the InternetInternet Growth (1969-2004)

Domain Name System (DNS)What is it?How does it work?

TCP/IP What are they?Why are they needed?

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History of Communication

The Telegraph (1837)The Telephone (A. Bell 1876)Radio Broadcasting (1920’s)Television Broadcasting (1950’s)Geostationary Satellite communications (1960’s)Computer communications (1970’s)Optical communications (1980’s)Internet and mobile communications (1990’s)

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What Is the Internet?

A network of networks, joining many government, university and private computers together and providing an infrastructure for the transport of data between any two entities connected to this network.

Uses TCP/IP protocols and packet switching .

Runs on any communications substrate.

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Example of Intercity and Transoceanic Networks

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• 160 10G (moving towards 40G) DWDM Channels per fiber pair• NZ-DSF, Corning E-LEAF fiber• Dispersion compensation at amplifiers• BER < 10-13

Gateway/Regen

1 2 3 4 5

2.5G, 10G, 10GigE Waves

100km Erbium Amplifiers

Gateway/Regen600 km Maximum

Amplifier Site

Long Distance Transport

ADM or Optical Switch for Protected Private Line Services

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Brief History of the Internet

1968 - DARPA (Defense Advanced Research Projects Agency) creates ARPAnet1970 - First five nodes: (UCLA, Stanford, UC Santa Barbara, U of Utah, and BBN)Focused around academia and researchPrimarily in North AmericaNon-for profit Used for email and file transfer (ftp) – No world wide web (www)1974 - TCP specification by Vinton Cerf1984 – On January 1, the Internet with its 1000 hosts converts en masse to using TCP/IP for its messaging1989 - Tim Berners-Lee at CERN in Geneva proposes hypertext system that will run across the Internet on different operating systems. This becomes the World Wide Web…1993 – Mosaic was created

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From Simple, But Significant Ideas Bigger Ones Grow1940s to 1969

1945 1969

We can accessinformation using

electronic computers

We do it reliably with “bits”, sending and receiving data

We can do it cheaply by using Digital circuits etched in silicon.

We can accomplish a lot by having a vast network of computers to use for

accessing information and exchanging ideas

We will prove that packet switching works over a WAN.

Packet switching can be used to send digitized data though

computer networks

Hypertext can be used to allow rapid access to text data

Copyright 2002, William F. Slater, III, Chicago, IL, USA

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From Simple, But Significant Ideas Bigger Ones Grow1970s to 1995

1970 1995

Ideas from1940s to 1969

We need a protocol for Efficient and Reliable transmission of

Packets over a WAN: TCP/IP

The ARPANET needs to convert to a standard protocol and be renamed to

The Internet

Computers connected via the Internet can be used more easily if hypertext links are enabled using HTML

and URLs: it’s called World Wide Web

The World Wide Web is easier to use if we have a browserto browse web pages, running in a graphical user interface context.

Great efficiencies can be accomplished if we useThe Internet and the World Wide Web to conduct business.

Copyright 2002, William F. Slater, III, Chicago, IL, USA

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Internet Growth Trends

1977: 111 hosts on Internet1981: 213 hosts1983: 562 hosts1984: 1,000 hosts1986: 5,000 hosts1987: 10,000 hosts1989: 100,000 hosts1992: 1,000,000 hosts2000: Over 407 million users2001: 150 – 175 million hosts2001: 31 million domain names (100 Tbit of data)2002: over 200 million hosts – 840 million usersBy 2010, about 80% of the planet will be on the Internet

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Growth of Internet Hosts *Sept. 1969 - Sept. 2002

0

50,000,000

100,000,000

150,000,000

200,000,000

250,000,000

9/69

01/71

01/73

01/74

01/76

01/79

08/81

08/83

10

/8511

/86

07/88

01

/89

10/89

01

/91

10/91

04

/92

10/92

04

/93

10/93

07

/94

01/95

01

/96

01/97

01

/98

01/99

01

/0108

/02

Time Period

No.

of H

osts

The Internet was not known as "The Internet" until January 1984, at which timethere were 1000 hosts that were all converted over to using TCP/IP.

Chart by William F. Slater, III

Sept. 1, 2002

Dot-Com Bust Begins

Copyright 2002, William F. Slater, III, Chicago, IL, USA

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Domain Name RegistrationJan. ‘89 - Jul. ‘97

April 2001: 31,000,000 Domain Names!!!

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Statistics from the IITF Report The Emerging Digital Economy *

To get a market of 50 Million People Participating:Radio took 38 years TV took 13 yearsOnce it was open to the General Public, The Internet made to the 50 million person audience mark in just 4 years!!!

http://www.ecommerce.gov/emerging.htmReleased on April 15, 1998

* Delivered to the President and the U.S. Public on April 15, 1998 by Bill Daley, Secretary of Commerce and Chairman of the Information Infrastructure Task Force

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Internet Bandwidth

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Internet Bandwidth (2005)

Internet demographics shifting rapidlyAsia-Pacific has the largest share of Internet and mobile users and leads in advanced Internet technologies, such as broadband access and mobile dataChina has overtaken the United States as the world’s largest market for fixed-lines and mobile and soon for broadbandGlobal telecommunications epicenter shifting from North America and Western Europe to Asia-Pacific region

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Next Generation Networks

We are in a network paradigm shift…

The big picture trends

Birth of Broadband

Growth in wireless networks and mobile data services

Mobile overtakes fixed

Convergence of Internet Protocol-based networks with telephone & mobile networks

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Next Generation Networks

First phase

Growth of Internet and other IP-based networks with their requirements for bandwidth and capacity has driven rapid innovation in telecommunication access and transport networks, examples:

leveraging copper wire “last-mile” networks through digital subscriber line (“DSL”) technologiesre-architecturing of cable networks to support IP servicesadvances in optical networking technologies (e.g. PON)advances in wireless technologies (e.g., Wi-Fi, WiMax)

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Next Generation Networks

Second phase

Ongoing trend towards integration & interoperability of IP-based and PSTN network services and applicationsImpact on build-out of national telecommunications infrastructuresGlobal shift from PSTN build-out to broadband “converged” platform build-outEnabling platform for voice, video, dataBroadband - New ITU standards (DSL, cable) have brought broadband access to over 100 million new users since 1999

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DNS: Domain Name System

Internet hosts:IP address (32 bit) - used for addressing datagrams (IPv4)“name”, e.g., ww.yahoo.com - used by humans

DNS: provides translation between host name and IP address

distributed database implemented in hierarchy of many name serversDistributed for scalability & reliability

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DNS

Purpose of naming

Addresses are used to locate objectsNames are easier to remember than numbersYou would like to get to the address or other objects using a name

DNS provides a mapping from names to resources of several types

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DNS

Names and addresses in general

An address is how you get to an endpoint – Typically, hierarchical (for scaling):

950 Charter Street, Redwood City CA, 94063204.152.187.11, +1-650-381-6003

A “name” is how an endpoint is referenced –Typically, no structurally significant hierarchy

“David”, “Tokyo”, “itu.int”

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DNS

Domain names are the familiar, easy-to-remember names for computers on the Internet (e.g., amazon.com)Domain names correlate to Internet Protocol numbers (IP numbers)(e.g., 98.37.241.130) that serve as routing addresses on the InternetTypes of Internet Domains

Generic Top Level Domains (gTLDs)<.com>, <.net>, <.org> open to all persons and entities on a global basis<.int> for international treaty organizations<.arpa> for Internet Infrastructure purposes<.gov>, <.mil> for U.S. government, military<.edu> for US universitiesNew: <.info>, <.biz>, <.name>, <.areo>, <.coop>, <.museum>, <.pro>

Country Code Top Level Domains (ccTLDs)<.gh>, <.hk>,<.jp>, <.ca>, <.br>, <.de>, <.tv>,

Registration requirements vary by domain:Residency requirementPrice (or no charge)Dispute resolution policy

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DNS

DNS created in 1983 by Paul Mockapetris

A lookup mechanism for translating objects into other objects

Comprised of three componentsA “name space”Servers making that name space availableResolvers (clients) which query the servers about the name space

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DNS

DNS Features: Scalability

Queries distributed among masters, slaves, and caches

DNS Features: Reliability

Data is replicated – Data from master is copied to multiple slaves

Clients can queryMaster serverAny of the copies at slave serversClients will typically query local caches

DNS Features: DynamicityDatabase can be updated dynamically – Add/delete/modify of any recordModification of the master database triggers replication

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DNS

Concept: DNS Names

• The namespace needs to be made hierarchical to be able to scale.

• The idea is to name objects based on – location (within country, set of organizations, set of companies, etc)– unit within that location (company within set of company, etc)– object within unit (name of person in company)

• WWW.APNIC.NET (labels separated by dots)

• Domain names can be mapped to a tree (New branches at the ‘dots’)

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DNS

Concept: DNS Domains

• Domains are “namespaces”

• Everything below .com is in the com domain

• Everything below apnic.net is in the apnic.net domain and in the netdomain

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DNS

Concept: Name Servers

• Name servers answer ‘DNS’ questions

• Several types of name servers– Authoritative servers

• master (primary)• slave (secondary)

– (Caching) recursive servers• also caching forwarders

– Mixture of functionality

• Authoritative name server– Give authoritative answers for one or more zones– The master server normally loads the data from a zone file– A slave server normally replicates the data from the master via a

zone transfer

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DNS

Authoritative name server

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DNS

Recursive serverDo the actual lookups; ask questions to the DNS on behalf of the clientsAnswers are obtained from authoritative serversAnswers are stored for future reference in the cache

Concept: Resolvers

Resolvers ask the questions to the DNS system on behalf of the application

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DNS

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DNS

13 root name servers

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requesting hostcis.poly.edu

gaia.cs.umass.edu

root DNS server

local DNS serverdns.poly.edu

1

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4

5

6

authoritative DNS serverdns.cs.umass.edu

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TLD DNS server

DNS Infrastructure

Host at cis.poly.edu wants IP address for gaia.cs.umass.eduInfrastructure:

Client resolverLocal DNS serverAuthoritative DNS ServerRoot DNS ServerTop-Level Domain DNS Server

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Distributed, Hierarchical Database

Root servers and TLD servers typically do not contain hostname to IP mappings; they contain mappings for locating authoritative servers.

Root DNS Servers

com DNS servers ca DNS servers edu DNS servers

poly.eduDNS servers

umass.eduDNS servers

yahoo.comDNS servers

amazon.comDNS servers

ucalgary.caDNS servers

TLDServers

usask.caDNS servers

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DNS: Root name servers

contacted by local name server that can not resolve nameroot name server:

contacts authoritative name server if name mapping not knowngets mappingreturns mapping to local name server

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TLD and Authoritative Servers

Top-level domain (TLD) servers: responsible for com, org, net, edu, etc, and all top-level country domains uk, fr, ca, jp.

Network solutions maintains servers for com TLDEducause for edu TLD

Authoritative DNS servers: organization’s DNS servers, providing authoritative hostname to IP mappings for organization’s servers (e.g., Web and mail).

Can be maintained by organization or service provider

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Local Name Server

Each ISP (residential ISP, company, university) has one.

Also called “default name server”

When a host makes a DNS query, query is sent to its local DNS server

Acts as a proxy, forwards query into hierarchy.Reduces lookup latency for commonly searched hostnames

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requesting hostcis.poly.edu

gaia.cs.umass.edu

root DNS server

local DNS serverdns.poly.edu

1

2

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6

authoritative DNS serverdns.cs.umass.edu

7

8

TLD DNS server

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Recursive queries

recursive query:puts burden of name resolution on contacted name serverheavy load?

iterated query:contacted server replies with name of server to contact“I don’t know this name, but ask this server”

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DNS: caching and updating records

once (any) name server learns mapping, it caches mapping

cache entries timeout (disappear) after some timeTLD servers typically cached in local name servers

Thus root name servers not often visited

update/notify mechanisms under design by IETF

RFC 2136http://www.ietf.org/html.charters/dnsind-charter.html

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DNS protocol, messages

DNS protocol : query and reply messages, both with same message format

msg headeridentification: 16 bit # for query, reply to query uses same #flags:

query or replyrecursion desired recursion availablereply is authoritative

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DNS protocol, messages

Name, type fieldsfor a query

RRs in reponseto query

records forauthoritative servers

additional “helpful”info that may be used

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Inserting records into DNS

Example: just created startup “George Networks”

Register name georgenetworks.com at a registrar (e.g., Network Solutions)

Need to provide registrar with names and IP addresses of your authoritative name server (primary and secondary)Registrar inserts two RRs into the com TLD server:

(georgenetworks.com, dns1.georgenetworks.com, NS)

(dns1.georgenetworks.com, 212.212.212.1, A)

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Transport Control Protocol (TCP)

TCP is a connection-oriented transport protocol

Sends data as an unstructured stream of bytes.

Uses sequence numbers and acknowledgment messages.

If data is lost in transit from source to destination, TCP can retransmit the data until either a timeout condition is reached or until successful delivery has been achieved.

TCP can also recognize duplicate messages and will discard them appropriately.

If the sending computer is transmitting too fast for the receiving computer, TCP can employ flow control mechanisms to slow data transfer.

TCP can also communicate delivery information to the upper-layer protocols and applications it supports.

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Internet Protocol (IP)

IP is the primary layer 3 protocol in the Internet suite:

Provides internetwork routing

Provides error reporting and fragmentation and reassembly of datagrams.

IP addresses are globally unique, 32-bit numbers assigned by the Network Information Center.

An IP address is divided into three parts:network address, subnet address, host address.

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Internet Protocol (IP)

Routing in IP Environments

Routers within the Internet are organized hierarchically. Some routers are used to move information through one particular group of networks under the same administrative authority and control. (Such an entity is called an autonomous system.)

Routers used for information exchange within autonomous systems are called interior routers, and they use a variety of interior gateway protocols (IGPs) to accomplish this end.

Routers that move information between autonomous systems are called exterior routers; they use the Exterior Gateway Protocol (EGP) or Border Gateway Protocol (BGP).

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Internet Protocol (IP)

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Internet Protocol (IP)

Routing protocols used with IP are dynamic in nature.

Dynamic routing requires the software in the routing devices to calculate routes.

Dynamic routing algorithms adapt to changes in the network and automatically select the best routes.

IP routing tables consist of destination address/next hop pairs.

IP routing specifies that IP datagrams travel through an internetwork one router hopat a time. The entire route is not known at the outset of the journey. Instead, at each stop, the next router hop is determined by matching the destination address within the datagram with an entry in the current node's routing table. Each node's involvement in the routing process consists only of forwarding packets based on internal information.

IP does not provide for error reporting back to the source when routing anomalies occur. This task is left to another Internet protocol: the Internet Control Message Protocol (ICMP.)

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ICMP

ICMP:

ICMP provides a method for testing node reachability across an internet (the ICMP Echo and Reply messages)

Provides a method for increasing routing efficiency (the ICMP Redirect message)

Provides a method for informing sources that a datagram has exceeded its allocated time to exist within an internet (the ICMP Time Exceeded message)

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IPv6

IPv6 = 128 bits of addressing

Theoretically, 1038 hostsSignificant transition effort neededRegional Internet Registries are now allocating IPv6

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Native IPv6 Infrastructure

Questions?