Chapter6 The Internet 1

In search box, enter command promptAt c:\ prompt enter

ping alpha.fdu.edu– Are you connected to the Internet?– Is the destination host alive on the Internet– How many packets were sent? (4 in windows),

lost, received– The average latency in milli-sec; min. max. avg– IP address translation for the destination given

The Internet

History of Internet

• Impetus of Cold War– Sputnik showed Russia’s advanced technology– Russia had detonated an atom bomb

• Desire for a decentralized, robust, alternative communications network

• Decision for a packet switching network– AT&T’s telecommunications monopoly had a

circuit switching networkChapter6 The Internet 2

ARPA sponsored ARPANet

• 1969 Four universities linked together– Gradually expanded to other sites

• Linked LANs and WANs together (internet)

– 1990 – FDU connected through dial-up to Rutgers

• Initially command line interface

• “Archie” became a command line search tool for anonymous ftp sites

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Commercializing the Internet

• The Internet was “given” to NSFNet and eventually to Network Service Providers – Each NSP maintains its own infrastructure– High speed fiber-optic links; high capacity

routers for directing traffic– NSPs are connected at network access points– AT&T, British Telecom, Deutsche Telekom,

Verizon

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NSPs and ISPs

• NSPs may also be ISPs – lease lines to public

• NSPs may lease internet connections to Internet Service Providers– Internet connections are leased to public on

monthly basis or by time consumed– Typically ISPs are AT&T, Verizon, MSN,

Comcast, British Telcom

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ISP services• Internet connection

• E-mail server (possibly with virus protection)

• Perhaps server for subscriber web sites– Maintains web pages

• Perhaps server for chat groups, instant messaging, FTP, music file sharing, etc.

• News, Ads

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Public connection to the Internet

• Computer connected to (perhaps internal) modem and/or router.– Computer may be connected to a LAN which is

then connected to the Internet– Connects to the ISP’s (edge) router– ISP is connected to NSP– NSPs are connected through the Internet

backbone infrastructure

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Internet Protocols

• Communication protocol is a set of rules for defining network services– TCP/IP is the main protocol suite for Internet

communication• Search window: View Network connections/ click

on any icon that shows a connection

• properties

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TCP/IP attributes• TCP/IP is in public domain, free, extensible

• Handles addressing packets (using IP) on the Internet

• Handles addressing services (using TCP ports) on your system

• TCP breaks message unit into packets

• IP and TCP add headers for error detection, sequencing, addressing

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IP

• IPv4 provides 32 bits for IP addresses– About 4.3 billion– This is not enough, partially because there is a

class structure imposed on the addresses

• European and Asian countries spearheaded the development of IPv6– 128 bits provided enough even if every

device in your house has a static IP address

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Static and Dynamic Addresses

• On FDU’s system, our desktop IP addresses are “leased” – may be periodically changed

• Web servers must have static IP addresses. These are registered in a central database (DNS)

• There are security advantages of leased, non-static addresses

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Network Connection Details

• In search bar, write “view network connections”

• Click on the icon that shows a connection– General/ details– IP address(es)– DHCP– DHCP server – DNS server

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Some Other Internet Protocols• UDP (User Datagram Protocol)

– less reliable, less complex alternative to TCP• HTTP (Hypertext Transfer Protocol)

– Web GUI for information sharing and linking• FTP (File Transfer Protocol)• SMTP (Simple Mail Transfer Protocol

– and POP (Post Office Protocol) - mail transport• VoIP – (Voice over IP)• BitTorrent (distributed file sharing)

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Every email address and web site has a top-level domain

• fdu.edu– FDU’s top-level domain is edu

• Top level domains of edu, gov, mil restricted in US

• Unrestricted domains include com, org, biz

– In most countries, country code is top-level– DNS for each top-level domain translates the

words into IP addresses– Fdu domain information is stored at DNS

• Who.is/whois

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Port addresses

• Each computer (system) on the Internet has an IP address

• Each service has a port– In command prompt, type netstat (or netstat –a

for UDP and TCP) (netstat –n for ports on both ends)

– 80 is a well-known port for web services– User processes are assigned ports dynamically

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Setting up a web site• Get your own domain name (Internet Corporation

for Assigned Names and Numbers - ICANN) – Or get a domain name from a regional registry

– Fees range from $10 to $100 with perhaps other services includes

• “parking” is reserving a name for later use

• Internet Assigned Numbers Authority (IANA) delegated the last 5 blocks of IPv4 address space to regional registries on 2/11

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Try Tracert on Windows

• Go to command prompt

• Tracert google.com– returns number of “hops”; path taken

• Compare to ping (latencies don’t match)

• To identify IP owners try– who.is/whois or nslookup– You may not be successful

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Connection speed

• Dial-up lines provide top speeds of 56 kbps– Upstream speed is slower than downstream

– Asymmetric Internet connection

– Yet, servers need high upstream speed

• DSL, cable, FIOS, WiMAX, cellular phones– FIOS advertises up to 50/25Mbps

– WiMAX from Sprint advertises up to 40Mbps

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Different types of connectivity

• Fixed internet access– Desktop is connected through wall socket to

roof-mounted antenna or wire to ISP

• Portable Internet access– Wireless router in your house links your

laptops to Internet, for example

• Mobile Internet access – cell-phone or laptop that connects to base station

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Fixed Internet Access

• Dial-up

• RJ-11 port on computer connected to telephone line through telephone wall jack– Internal or external modem – Modem (modulator/demodulator) converts

digital signals (pulses) to analog signals (continuous electromagnetic waves)

– Modem and ISP negotiate (handshake)

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Fixed Internet Access

• DSL, ISDN, T1 lines– More expensive, faster than dial-up– DSL is provided by the local telephone

company, linked to the ISP• Not available in all areas – depends on the distance

from the switching station (5km max)

• Phone and computer can share connection

• Uses existing phone lines

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Fixed Internet Access

• Cable Internet Service (Comcast, Cox)– Connected through LAN port (or USB port)

• Coaxial cable installed (or used from cable TV)

– Local customers are all connected to the same bus, perhaps via a metro ethernet (MAN)

• Download speed decreases with more users

• Potential for users to access each other’s data

– Always-on connection

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Satellite Internet Service

• Geosynchronous satellites are 22,000 m above the equator

• Latency can be 1 second or more

• Teledesic, Iridium-low orbit satellite ISPs– Require a satellite dish and a modem – Satellites may offer a type of fixed wireless

service– Use microwave frequencies – line-of-sight

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WiMax fixed wireless service

• IEEE 802.16 / Ethernet-compatible

• Microwave towers sending signals to dishes– Line of sight– Either a roof antenna is hard wired to clients in

the house– or customers may be able to communicate with

tower through wireless – must be line of sight

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Downstream speeds

• Dial-up 56Kbps

• ISDN 128Kbps

• DSL 384K to 8Mbps

• Cable 5-30 Mbps

• Satellite 1-1.5 Mbps

• WiMAX 70 Mbps (advertises 40 Mbps)

• FIOS – up to 50 MbpsChapter6 The Internet 25

Portable & mobile Internet access• Wi-Fi equipped computers can connect to

any “hotspot” – Some ISPs offer hotspot service plans

• Not interchangeable

– Local hotspots may be free or usable by-fee– Wi-Fi is not really portable in that you cannot

easily move from one hotspot to another– Mobile Wi-Fi would provide for hand-offs

• Security is always an issueChapter6 The Internet 26

Wi-MAX

• If you are within the area of your transmitting tower, your access to the internet, perhaps by a laptop, is portable

• Mobile Wi-MAX is being worked on to provide handoffs for users

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Smartphone Internet access

• Portable and mobile; transparent handoffs

• 4G cellular technology advertises speed of perhaps 6Mbps– PCWorld tested devices – only Verizon reached

this speed for download (5 Mbps for upload)– Issues of Size of display, Security/

confidentiality, Coverage, Cost

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Internet Services• Vo/IP (such as phone service through a

cable company) – Download Skype for Windows 7 for free

• Includes free computer to computer calls

• Cost for connecting to land lines

• Real-time messaging is also available

– Concern about security of Skype (always on unless you pull the plug out)

– Ekiga – open source alternative

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VoIP

• Transmits voice with IP/packet switching

• Quality can vary – Packets can be lost or delayed– Most VoIP connections need power

• Land lines do not require power connection as long as their handsets are not cordless

– 911 systems cannot automatically identify caller

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Cellular Data Service

• HSUPA (3rd generation cellular networking)– High-Speed Uplink Packet Access– Voice and data– 2-5.75 Mbps uplink data rate– WAP (wireless application protocol) to access

Internet through cellular phones, PDAs, etc.• Simplified versions of web sites

• Low-resolution screens

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FTP, the Web and BitTorrent• ftp

– open ftp://ftp.swfwmd.state.fl.us/pub/– Login anonymous; password: email address

• Web download (restricted upload)

• BitTorrent– Swarm of computers sharing in distributing

packets of a large file using peer-to-peer• Computer is freed as soon as it sends all of its

packets off Chapter6 The Internet 32

Internet Security

• An Oxymoron?

• Attackers are constantly attempting to “hack” your machines

• Always on computers are always at risk

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Connecting through open ports

• Port probe (port scan) – i.e. nmap – free, open source software– Port scanning software can probe 30,000

computers/minute– Sends connection requests to all TCP ports

• Does it get any response?

• Use netstat –a to find a list of open ports

• “listening” services (ftp, http) typically do respond

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What to do against port attacks?

• Close any services (and their ports) that you are not using

• Turn off your computer when you are not using it

• Get good protection software (firewalls, virus protection)

• Patch/ update your OS and security software

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Other measures

• Turn off guest account

• Turn off file sharing, if possible

• Use a router with NAT addresses

• Use VPNs if possible– Place VPN client in windows search bar for

FDU VPN service

• Encrypt your files

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Other Internet issues

• Corrupted web sites

• Infected mail

• Downloading infected files

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Societal concerns

• Pornographic sites

• Violent computer games

• Gambling

• Cyber bullying

• Posted knowledge of bomb making, etc.

• This behavior was available before the Internet, but the Internet makes it easier

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Free Speech as a positive force

• “Should governments be allowed to block access to web sites [and the web] based on local religions, politics, and customs?” p.347

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