Transcript What is a process? - Fairleigh Dickinson University

The Internet
In search box, enter command prompt
At 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
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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 network
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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
–
–
–
–
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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
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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 Mbps
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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 issue
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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)
–
–
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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
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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
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•
•
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
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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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