Chapter 6 CS104

Soviet Union launched Sputnik. First Man-made satellite.
Connected Computers at UCLA, Stanford Research Institute, University of Utah, University of California at Santa Barbara.
Connection two or more networks creates an internetwork. Or internet.
Popularity of Internet
Rose in 1990s due to software developers making user friendly, internet access tools.
internet size today
500 million nodes , 2 billion users.
internet backbone
Network of high-capacity communications links that provides the main routes for data traffic across the internet.
Network service providers
NSPs. Maintain the backbone links and routers of the internet. Examples AT&T, British Telecom, etch.
Network Access Points
NAPs. Where NSP equipment is linked to begin its travel to a provider and then its destination.
Internet service provider
ISP. Compan that offers Internet access to individuals, businesses, and smaller ISPs.
ISP operate
routers, communication equipment, other network devices that handle the physical aspects of transmitting and receiving data between their subscribers and the internet.
contains circuitry that converts the data-carrying signals from your computer to signals that can travel over various communications channels. Computer can communicate with an ISP through a combination of router and modem or just a modem.
Transmission Control Protocol. Creates connections and exchanges packets of data.
Internet Protocol. Provides devices with unique addresses.
User Datagram Protocol. Alternative data transport to TCP used for DNS. Voice over IP, and file sharing.
Hypertext Transfer Protocol. Exchanges information over the Web.
File Transfer Protocol. Transfers files between local and remote host computers.
Post Office Protocol. Transfers files between local and remote host computers.
Simple Mail Transfer Protocol. Transfers mail form an e-mail server to a client inbox.
Voice over Internet Protocol. Transmits voice conversations over the internet.
Internet Relay Chat. Transmits text messages in real time between online users.
BitTorrent. Distributes files using scattered clients rather than a server.
Primary protocol suite responsible for message transmission on the internet.
Protocol suite
Combination of protocols that work together.
Transmission Control Protocol. Breaks a message or file into packets.
Internet Protocol. Responsible for addressing packets so that they can be routed to their destination. Context of the internet TCP/IP addresses or IP addresses or Internet addresses are the same. Each part of the IP address is used to get the exact destination.
static IP address
Permanently assigned IP address for a computer.
dynamic IP address
Temporarily assigned IP address for a computer.
Why doesn’t everyone have the same IP address?
Many IP addresses are reserved for special purposes. Dynamic IP addresses are assigned as needed and can be reused whenever needed.
How to get a dynamic IP address?
Every time you connect to your provider you are assigned one.
Always-on connection.
Linked to your ISP and is online whenever your computer and modem are on, even if you are not actively accessing the Internet.
domain name
key component of web addresses, email addresses, and addresses on the web called URLs.
top-level domain
Domain name ends with an extension that indicates the top level domain.
unrestricted use, usually commercial business
unrestricted use. usually commercial businesses
restricted to North American educational institutions.
restricted to U.S. government agencies.
Unrestricted use
Restricted to organizations established by international treaties.
Restricted to U.S. Military agencies.
Available for sites that cater to mobile devices such as smartphones.
Unrestricted use; traditionally for Internet administrative organization.
Unrestricted use; traditionally for professional and non profit organizations.
Domain Name System
(DNS) Every domain name corresponds to a unique IP address that has been entered into this huge database.
domain name server
Any computer that hosts the DNS database.
Prefixes on a URL
Correspond to protocols, ports and services offered by Internet Computers.
Communications port
can be described as a virtual device because it is a physical circuit or mechanism, but rather an abstract concept that allows a computer to perform more than one time of a service.
Internet Corporation for Assigned Names and Number. Recognized by the United States and other governments as the global organization that coordinates technical management of the internet’s Domain Name System.
Elapsed time for data to make a round trip from point A to point B and back to point A. Usually less than 100ms, increases for overseas transmissions.
Packet Internet Groper. Sends signal to a specific Internet address and waits for a reply. If it receives a reply it measures how long it took for a round trip.
Records a packet’s path in addition to its round-trip speed. You can use it to analyze the latency of your data as it hops from one Internet router to the next.
Upstream speed
Rate of data that is uploaded from your computer to the Internet.
Downstream speed
rate of data downloaded to your computer.
asymmetric internet connection
when upstreat speeds differ from downstream speeds.
symmetric internet connection
When upstream and downstream speeds are the same.
Fixed internet access
links computer to an ISP from a stationary point such as a wall socket or roof-mounted antenna.
Portable Internet access
allows you to easily move your access device, as in the case of vehicle-mounted satellite dishes that can be deployed when vehicle is parked.
mobile internet access
allows you to use the internet as you are on the go, such as using a cell phone to collect your e-mail while you are traveling by train.
dial-up connection
fixed internet connection that uses a voiceband modem and telephone lines to transport data between your computer and your ISP.
voiceband modem
usually referred to simply as a modem. converts signals from your computer into audible analog signals that can travel over telephone lines.
Speed of voiceband modem
theoretical 56 Kbps but usually tops out at 44 Kbps. Voice band connections are assymmetrical, upload speeds usually tap out at 33 Kbps. You can only use this connection to send data or talk. Not both. Still able to use with a digital phone.
Integrated Services Delivery Network. Type of fixed Internet connection that moves data at speeds of 64Kbps or 128 Kbps over ordinary phone lines. symmetric speed. usually a telephone company or a ISDN service provider can give you this service.
ISDN terminal adapter.
Sends digital signals. Sometimes called an ISDN modem
Digital subscriber line. High speed digital, always-on, internet access technology that runs over standard phone lines. One of the fastest connections available to individual consumers. Variations include ADSL (asymmetric DSL), SDSL (symmetric DSL), HDSL (high bit DSL), DSL lite also.
DSL Data
Travels to and from local telephone switching station in pure digital form, by passing the bottleneck of analog switching to digital and back again.
DSL speeds
around 6 Mbps downstream from a distance of about 1.25 miles. For signal to work the connection has to be within 3 miles of your telephone company’s switching station.
DSL modem
device that connects a computer to a telephone line and converts computer data signals into signals compatible with DSL.
DSL filter
Prevents voiceband signals form interfering with DSL signals Professionally installed business DSL systems tipically use a single external filter.
Cable Internet Service
Means of distributing always-on broadband Internet access over the same infrastructure that offers cable television service. Standard speeds are 12 Mbps download and 1Mbps uploads.
Cable modem
converts your computer’s signal into one that can travel over the CATV network. Most people rent a cable modem.
(Data Over Cable Service Interface Specifications) is a data transport technology that includes security filters.
Satellite Internet Service
Means of distributing always-on, high speed asymmetric Internet access by broadcasting signals to and from a personal satellite dish. Better range than phone and cable internet service. Average speeds of 1 to 1.5 Mbps downloads but only 256 Kbps for uploads. Latency of about 1 second.
satellite modem
Device that modulates the data signals from a computer into a frequency band that can be carried to the satellite dish, where it is converted to another frequency, amplified and transmitted.
Fixed wireless internet service
Also called wireless broadband service is designed to foffer internet access to homes and businesses by broadcasting data signals over areas large enough to cover most cities and outlying areas. MAN (metropolitan area network.)
stand for Worldwide Interoperability for Microwave Access, is an Ethernet-compatible network standard designated as IEEE 802.16. Popularity growing because it offer an alternative to wired technologies. WiMAX can be deployed in rural areas where cable services. Speed 1 to 5 Mbps for downloads. Can offer less latency than satellite.
How WiMAX works
WiMAX system transmits data to and from WiMAX antennas mounted on towers. Single tower can serve a large geographical area. Towers can transmit data to subscribers they can relay data to other towers using microwave links.
Wifi hotspot
area in which the public can access a Wi-Fi network that offers internet service. Typically 2-8 Mbps for speeds. Not usually protected by WPA protection or encryption because they can’t hand out passwords to everyone. Public hotspots don’t provide acceptable mobile internet access because you have to remain within range.
Portable WiMAX
Can be used as a portable technology because Internet access is available to subscribers anywhere within the towers coverage.
Mobile WiMAX
New service that could make it possible for only haveing one cell phone and Internet access provider.
Portable satellite
Dish is usually mounted on a vehicle.
Wireless Application Protocol. Communications protocol that provides Internet access from handheld devices such as cell phones. WAP-enabled devices contain a microbrowser that displays simplified versions of popular Web sites.
Mobile Broadband
Broadband requires a fast connection, a data service subscription and mobile broadband equipment.
Cellular service providers
Provide a data service plan.
Real time messaging system
Allows people to exchange short messages while they are online
Instant messaging
one on one mesaging
group communications.
How does it work
Client/server, where client sends messsages to server and then to other client.
Technology in which a broadband internet connection is used to place telephone calls instead of the regular phone system.
Measures the variability of packet latency. network traffic and interference can delay some packets and create erratic data flow.
Packet loss
Refers to data that never reaches its destination or gets discarded because it arrives too late to be of any use.
Internet forum
Web-based online discussion site where participants post comments to discussion threads. most forums have a moderator who monitors discussion threads, weeds out disruptive participants and handles membership requests.
allows participants to modify material. Wikipedia is the best known wiki. Participants can post material pertaining to a topic and other participants can modify it.
is similar to an online diary, it is maintained by one person ( sometimes by a company or an organization) contains a series of entries on one or more topics.
short message of 140 characters long or less posted to the twitter web site. Sometimes referred to as micro blogging because the tweets are similar to blogs entries.
cloud computing
depends on a grid of servers and storage services that offer internet accessible computing services ranging from hardware to office productivity applications and complex corporate data processing.
grid computing
network of computers harnessed together to perform processing tasks. Grid computing can be public or private. best used for big complex problems.
File transfer protocol. provides a way to transfer files form one computer to another over any TCP/IP network, such as a LAN or the Internet.
FTP server
typically resides on a computer containing files that remote users might want to access.
FTP client
Such as WS_FTP, cuteFTP offers an easy to use interface for accessing FTP servers.
anonymous FTP
can be accessed by logging in without a password by using the user ID, “anonymous”
p2p file sharing
uses peer to peer protocols that allow users to obtain files from other users located anywhere on the internet.
File sharing protocol that distributes the role of a file server across a collection of dispersed computers.
any access to data or programs by hackers, criminals or other unauthorized persons. Data can be stolen, altered, system configurations can be changed to allow even more intrusions.
port probe
is the use of automated software to locate computers that have open ports and are vulnerable to unauthorized access.
software or hardware designed to filter out suspicious packets attempting to enter to leave a computer.
routable IP address
one that can be accessed by packets on the internet.
Private IP address
is a non routable IP address that can be used within a LAN, but not for Internet data transport.
Network address translation
NAT process your router uses to keep track of packets and their corresponding private or public IP addresses.
Sales representatives and telecommuters often access corporate networks from home or from a customer’s office by using a secured connection called a virtual private network or VPN.