Section+2+-+Week+10+-+How+the+Internet+Works


 * WEEK 10**

__Keywords from "Networks" PDF__
Bandwidth- a communications channel like your CATV cable carries packets at a constant speed Slides 1-20
 * Protocols** - rules that ensure the orderly and accurate transmission and reception of data; start and end transmission, recognize error, sent data at the appropriate speed, and identify the correct senders and recipients
 * Handshaking** - protocols helps help network devices negotiate and establish communications
 * Packets** - the process by which you send a file or an e-mail over a network,the file is actually broken up into small pieces. It is a "parcel" of dad that is sent across a computer network
 * Packet Switching** - the technology of dividing a message into several packets that can be routed or independently to their destination to avoid out-of-service or congested links
 * Circuit Switching** - establishes a dedicated, private link between one telephone and another for the duration of a call; more efficient alternative to circuit switching
 * TCP/IP (Transmission Control Protocol/Internet Protocol**) - breaks messages into packets and addresses them for the transmission over the Internet
 * HTTP (Hypertext Transfer Protocol)** - Exchanges information over the web
 * FTP (File Transfer Protocol)** - Transfers files between local and remote host computers
 * POP (Post Office Protocol)** - Transfers mail from an e-mail server to a client inbox
 * SMTP (Simple Mail Transfer Protocol)** - transfers e-mail messages from client computers to an e-mail server
 * IMAP (Internet Mail Access Protocol)** - an alternative to POP
 * TELNET (Telecommunications Network)** - allows users who are logged on to one host to access another host
 * SSL (Secure Sockets Layer)** - Provides secure data transfer over the Internet
 * Ethernet** - broadcasts data packets to all networks is accepted only by the device to which it is addressed
 * CSMA/CD Protocol (Carrier Senese Multiple Access with Collision Detection)** - takes care of situation in which two network devices attempt to transmit packets at the same time
 * Uplink Port** - simple step up from a basic single-humb network is to connect several hubs
 * Wi-Fi Network -** transmits data as radio waves over predefined frequencies, much like cordless phones.
 * War Driving/LAN-Jacking** - occurs when hackers cruise around with a Wi-Fi equipped notebook computer that is set up to search for Wi-Fi signals coming from home or corporate Wi-Fi networks. War drivers can access and use unsecured Wi-Fi networks
 * WEP (Wired Equivalent Privacy)** - essential step in making Wi-Fi-transmitted data useless to intruders
 * Wi-Fi card** - transmitter, receiver, and antenna to transmit signals
 * Wireless Access Point** - provides a central point for data transmitted over a wireless network by broadcasting signals to any devices with compatible Wi-Fi cards
 * Bluetooth** - short-range wireless network technology that is designed to make its own connections between electronic devices - without wires, cables or any direct action from a user
 * Network Service Providers (NSPs)** - such as AT&T, backbone links and routers are maintained by NSPs
 * ISP (Internet Service Provider)** - operates network devices that handle the physical aspect of transmitting and receiving data from your computer
 * Ping - (Packet Internet Grouper)** - sends a signal to a specific Internet address and waits for a reply.
 * Traceroute** - records packet's path, including intermediate routers from your computer to its destination
 * Domain name-** An easy to remeber name that translates into a computer IP address
 * Top level domain-** ex: ".com" ".org" ".edu" .com would imply the host name is owned by a commercial busniess
 * Voiceband modem-** Usually refferred to as a modem, converts the digital signals from your computer into signals that can travel through telephone lines.
 * DSL(Digital Subscriber Line)-** a high speed, digital, always on internet access technology that uses standard phonelines to transport data
 * ISDN (Integrated Services Digital Network)-** connections move data faster that a dial-up connection, but not as fast as DSL or cable modems
 * DOCSIS (Date over cable service interface specification)-** a security technology that filters packets to certain ports, including the port the windows operating system uses for network
 * DSS (digital sattellite servcie)-** uses a geosynchronous or low-earth sattellite to transmit television, voice, or computer data directly to and from a sattelite dish or base station owned or leased by an individual
 * WAP (Wireless access protocol)-** a communications protocol that provides wireless internet access from handheld devices, such as cell phones and pda's
 * Cellular-ready modems**- packaged as PC cards that slip easily into the PCMCIA port of a notebook or tablet computer
 * Client/server – contains servers and clients
 * Peer-to-peer (P2P) – every computer is considered an equal
 * A network is a collection of computer systems configured to share digital data and resources
 * LANs extend across limited to geographical area.
 * Internetwork: collection of autonomous networks
 * a **transmitter** encodes the message as a signal
 * the **receiver** extracts a signal from the communications channel and converts it back into the form of a message
 * Messages are encoded as a stream of binary numbers **(0s and 1s)**
 * **Signals** are transmitted as electro-magnetic energy.
 * **CLIENT**- system requesting services
 * **SERVER**-( system that receives and handles requests from many clients concurrently

LAN (Local Area Network) __Two types of signals:__ __Broadband__ __Narrowband/baseband__
 * WAN (Wide Area Network)
 * MAN (Metropolitan Area Network)
 * PAN (Personal Area Network)
 * Analog
 * Digital
 * multiple signals transmitted on the same channel simultaneously
 * channel is divided into separate frequency bands, each capable of carrying a signal
 * employs [the entirety of its available] bandwidth for one signal

Slides 21-40

__Bandwidth__


 * • The bandwidth of a communications channel determines its capacity to transmit data—it’s analogous to the size of plumbing pipes (10MB, 100MB, 1GB, 10GB)
 * • Analog signals may contain independent waveforms of various frequencies
 * • The number of frequencies supported by a channel determines its bandwidth
 * • The bandwidth of a digital channel is usually measured in bits per second (bps)

__Sending Information__


 * When you transmit data, it is broken up into small pieces called packets
 * A packet is a parcel of data that is sent across a network
 * Has the address of its sender
 * Has the address of the destination
 * Has some data
 * When packets reach their ultimate destination, they are put back together into the data that was originally transmitted

__Data can be sent in two ways:__
 * Synchronous protocols
 * Asynchronous protocols

ì The message is made of separate data packets, each addressed to the destination ì Packets are transmitted over any available connection to the destination ì The receiving node reassembles the message
 * Packet Switching

Key words Communications network- the combination of hardware,software, and connecting links that transport data Shared resources-hardware,software, and data available to authorized network users PAN-personal area network and it refers to the interconnection of personal digital devices within a range of 30 feet MAN-metropolitan area network is a public high-speed network capable of voice and data transmission within a range of about 50 miles LAN-local area network is a data communications network that typically connects personal computers within a very limited geographical area WAN-wide area network covers a large geographical area and typically consists of several smaller networks, which might use different computer platforms and network technologies NAN-neighborhood area network provides connectivity within a limited geographical area, usually spread over several buildings client/server network-contains one or more computers configured with server software, and other computers configured with client software that access the servers workstations/client computers-computers running client software peer-to-peer network- treats every computer as an "equal" so that workstations can store network data server-a computer that is connected to a network and that serves or distributes resources to network users host computer- any computer that provides services to network users modem-network device connected to a computer that converts the digital signals from a computer into signals that can travel over a network modulation-changing the characteristics of a signal Demodulation-changes a signal back to its original state cable modem-type of modem used for TV Network Interface card-small circuit board that converts the digital signals from a computer into signals that can travel over a network transceiver- a wireless network sends and recieves data hub-broadcast data to workstations and peripherals routers- connect one network to another repeater-network device that amplifies and regenerates signals so that they can retain the necessary strength to reach their destination communications channel-physical path or a frequency for a signal transmission wired network-travels from one device to another through cables wireless network- travels through the air
 * Repeaters
 * boost the signal strength over transmission medium
 * Bridges
 * isolate LANs from unnecessary traffic, but connect LANs to neighboring networks

Slides 41-57

Protocols Communications protocol - a set of rules for efficiently transmitting data from one network node to another Best known protocol: TCP/IP (internet protocol suite) – set of protocols used for the internet Sending computer: prepares data for transmission Receiving computer: strips the packets of addressing information; reassembles the data from the packets TCP/IP is the glue that holds the Internet together Numbers are hard to remember, so host computers also have names called domain names; a domain names corresponds to an IP address; domain name system Internet 2- consortium of government, industry, and education The consortium- establishes network capabilities to support national research National LambdaRail- High-speed national network running on fiber Wireless Networks infrared broadcasting radio frequency broadcasting spread spectrum (cell telephony) direct sequence spread spectrum (DSSS) frequency hopping spread spectrum (FHSS) Using “ping” or “traceroute,” one can discover the length of time that data is in transit On average, data within the US usually arrives at its destination 110-120 milliseconds (ms) after it is sent Network Monitors Keep track of network traffic, number of packets, packet size, collisions, re-transmissions, etc. Enable planning for growth and quality Network Analyzers Randomly dissect packets, analyze problems, and determine the source of errors Portals Web entry stations that offer quick and easy access to a variety of services Consumer portals include search engines, e-mail services, chat rooms, references, news headlines, shopping malls, and other servicesCorporate portals on intranets serve the employees of particular corporations Vertical portals are targeted at members of a particular industry or economic sector Nets Intranets, extranets, electronic data interchange (EDI)
 * The IP part of TCP/IP defines the format for the addresses that identify computers on the Internet
 * These addresses are called IP addresses
 * An IP address is a series of numbers, such as 204.127.129.001
 * ISPs need static IP addresses