ARPA net; interface message processor (IMP) incorporates TCP/IP; first message “L” from UCLA to SRI sent by Charlie Kline. High speed backbone built by NSF to connect 5 supercomputing centers, then agreed to share bandwidth to allow other nets to connect through the backbone. 1991 NSF lifted commercial restrictions on the internet. WWW – a section of the internet developed for graphics, sound and video rather than text. 1988 Robert Morris Jr. releases internet worm affecting 10% of the 60k hosts on the internet. 1992 Jean Armour Polly coins “surfing the net.”
Chapter 24: How Local Area Networks Work
How Packets Divvy Up Data
Carrier wave; information wave; packet equivalent to carrier signal and permits bundling, addressing, error correction, organization of data packets varies to match the type of data they contain, may be called frames, segments or blocks; header = delivery IP, sender IP, number of packets, sequence number; Payload (1-1.5K); Footer/Trailer = CRC. Each packet sent separately through the best available route, the receiving computer reassembles the payload.
How Networks are Laid Out
NOS; peer-to-peer network; dumb terminal; wide area network; virtual network; topologies: bus topology, token ring, star topology.
How Network Nodes Connect
Bayonet Neill-Concelman (BNC) coaxial cable twists in twisted pair wires cancel out electrical noise. Registered jack (RJ) as in RJ 45 or RJ ; fiber optic carries 1 Gbps; reflective cladding; Ethernet packet = preamble, destination address, source address, type, data, CRC.
How Phone and Power Lines Bring LANs Home
Phone line bandwidth = 1 Mbps; power line bandwidth = 350 Kbps; phone line networks cannot cross a PBX or connect to a different phone line in the same building; power lines make a network available throughout a building; possible for computer to control other devices on a power line network.
Chapter 25: How PCs Connect to the Internet
Terminal adaptors
How a Dial Up Modem Calls the Internet
Analog local loop (maximum 36 Kbps) to public switched telephone network (maximum 64 Kbps). ADC records pulse code modulations (maximum 33.6 kbps due to analog line noise). ISP returns data (56 Kbps) uses mu-law codec to translate data into symbols (maximum 56.6 kbps –actually 53 due to power regulations). Analog local loop to DAC to data translation at computer.
How DSL Turbocharges a Phone Line
How Cable Modems Bring the Internet to Your PC
Chapter 26: How the Internet Moves Data
How Networks Talk with Each Other
Application layer; presentation layer; session layer; transport layer; network layer; data-link layer; physical layer.
How Information Travels the Internet
Network access point (NAP)
Chapter 27: How We Reach Each Other Through the Net
SMTP (simple mail transfer protocol), POP (post office protocol), Multipurpose Internet Mail Extensions (MIME); mail reflector
How Internet File Sharing Works
Traditional structure if internel is server concentric; more distributed structures are an alternative; true peer-to-peer is slower but difficult to police as software makes a computer a client and host at the same time.
How BitTorrent Spread the Wealth
BitTorrents sent randomly from many sources in a rarest-first scheme. Universe of peers and trackers exchanging and requesting bits is called a swarm. Tracker software slows down leeches and rewards seeders Trackerless trackers.
How Email Replaces Snail Mail
Attachments digitized using algorithms such as MIME, uuencode, BINHEX; DNS tells SMTP the best path for the message based on the domain of the addressee; routers determine pathway; gateways translate the data from one type of system to another.
How Chat Rooms Throw a Party
How Internet Messaging Lets You Pass Notes
Trillian
Chapter 28: How Wireless Sets PCs Free
How WiFi Spreads the Net Everywhere
Access point (AP) ; probe request; Institute of Electrical and Electronics Engineers (IEEE); WLAN; Routers deal with encrypted and addressed outer shell of messages and are destination points for content going to their WLAN; hot spots
How Cellphones Make a Call
System identification code (SID); control channel; mobile telephone switch office (MTSO); handoff; digital time division multiple access (TDMA); analog frequency division multiple access (FDMA); digital code division multiple access (CDMA); spread spectrum.
How Wireless Internet Keeps You Connected
Wireless application protocol (WAP); wireless markup language (WML); cards are translated to HTML at WAP gateway which extracts and encodes incoming data into byte code which is displayed in WML.
How Bluetooth Keeps Devices Connected
King Harold Bluetooth of Denmark, unifier of Scandinavia; link manager (LM); standby/sniffmode; page mode; inquiry mode; park mode; hold mode; 79 different hop frequencies.
How the iPhone Makes It All Slick
Gesture and multitouch; two types of touch sensors for screen: mutual capacitance and self capacitance.
Chapter 29: How the Net Provides Video and Audio on Demand
Streaming uses User Database Protocol (UDP) different from TCP in that UDP allows the connection to lose occasional packets.
How a PC Plays Streaming Audio
Click link to audio source -> Metafile -> Launch player -> player contacts server with connection speed -> server sends appropriate size file using UDP -> packets decompressed and decoded then sent to buffer -> when buffer is full audio file plays (and rebuffers if the buffer empties).
How a PC Displays Streaming Video
Captureboard converts analog to digital 30 fps using a codec algorithm, interframe compression, internet provider (IP) multicast – uses less bandwidth than UDP but requires a multicaster. PC receiving signals decompresses the video and split it into video and audio and these are sent to the video card and sound card respectively. Corrupted video can carry over to other frames; software compares new frames with others to detect errors and correct them.
Chapter 30: How the World Wide Web Works
How a Web Browser Opens Web Pages
Universal resource locator (URL); network solutions has the exclusive right to register domain names under agreement with NSF.
How a Web Browser Displays Pages
How Cookies Save Crumbs of Data
Cookie manager; cookie monster free program from ampsoft.net
How Google Knows Everything
Google bot crawls the web and sends full text from each page to Google’s indexing program and adds all links to its queue. Bot calculates the frequency of changes on each site and modifies the crawl rate to capture changes most effectively. Indexer stores text in a DB, each entry contains a list of pages where it appears. Google skips stop words, single digits or letters, and some punctuation marks. Index servers return a document based on relevance to a search including Page Rank where indexed terms appear if popular pages link to that page. Google’s doc servers summarize the page contents of the search results and pass them to the web servers that forward them to the searcher.
How eBay Sells Everything
Four geographically distinct mirrored data centers linked by SONET (synchronized optical network); searches are sent through search servers which send the search request to clusters of 50 db servers.
Chapter 31: How Internet Security Fights Off PC Invaders
Script kiddie.
How Computer Hackers Break Into Your PC
Hacking is methodical and incremental over the course of days or weeks; footprint analysis (publically available information); scan ports using available hacking software and map them and their relationships; a hacker uses these data to identify types of file transfer and email by sending random data to the ports often triggering a banner response that identifies the software using the port. This software is checked against online databases that list its vulnerabilities. Two ways to gain access: low tech is to trick employees into revealing their password, or use a brute force attack which uses a known username and a list of common passwords which ends either in (1) exhaustion of list, (2) lockout, or (3) access. Once access is gained, the hacker escalates privileges by looking for passwords of higher level users in the registry keys or email. Once access is achieved Trojans are uploaded to open a backdoor in the system to allow the hackers to access at will.
How Spyware Reports Everything You Do
Spyware, adware. Antivirus programs and firewalls cannot block spyware installed as a requested program so it is often bundled this way. Other spyware embeds itself in the registry where it is harder to find and more dangerous to remove. Spyware information could be stored in a cookie. Spyware opens a backchannel to send information found on your computer. Tricklers reinstall spy files as fast as they are deleted. Spybot Search and Destroy is a good spy assassin.
How Internet Firewalls Keep Out Hackers
A firewall is hardware or software; manager sets the rules to filter out unwanted intrusions, shut nonessential ports, and possibly block all inbound traffic except mail or specifically requested data. Packet filtering compares outbound addresses to a blocked list. Proxy server outside the firewall takes the hit if a dangerous transmission makes it past the filters. Stateful inspection compares key parts of each packet to a DB of known safe data, packets that fail are overwritten by subsequent packets. Firewall sends an alert and updates a security log with the type of attack, IP of orgin, and records of packets with intrusive code.
How Computer Viruses Invade Your Computer
When virus code is run it typically performs four actions: replication (boot record viruses run before the OS is loaded, program viruses insert copies of themselves following program headers); event watching (whenever a specific state exists the virus delivers its payload, without the trigger it just replicates); camouflage (nonfunctioning section of fake code that change each time it replicates or falsify header information so the program file appears to be the correct length); delivery. Memory-resident virus.
How Viruses Travel in Your Mail
Three types of mail viruses: attachment virus (must be double clicked, e.g., Loveletter, Melissa, Anna Kournikova); HTML virus (merely previewing activates the virus, e.g., Kakworm, BubbleBoy, Haptime); MIME virus (uses an OE/IE security hole and fills the email header until the buffer overflows into stack memory where the virus is executed instead of legitimate code – can run even if not seen, e.g., Nimba)
Email viruses replicate by getting names and email addresses then sending themselves out, perhaps with haphazard attachments.
How Antivirus Software Fights Back
AV software inspects master boot records, program files, macro code. Signature scanners inspect for code that matches a table of known viruses. Heuristic detectors look for time/date targeted events, routines to search for .com or .exe files and disk writes that bypass the OS. Memory-resident antivirus software install programs in RAM that operate in the background to identify behavior associated with viruses.
How Spammers Find You
Automated spiders that compile addresses from mailto: links and usenet newsgroups and chat rooms. Directory Harvest Attack sends generated email addresses to a mail server and log s any that do not produce an SMTP 550 error message.
How Antispam Software Sniffs Out Phony Email
Blacklists; junkmail filtering; content filtering; Baysian filters; whitelists; peer-to-peer shared white and black lists; spammerwocky
How Prime Numbers Protect Prime Secrets
Encryption uses two prime numbers as a private key; the product of the two primes are the public key. 128 bit encryption – no known way to factor a number larger than 80 digits. Digital signatures created by computing a message digest or hash value which is encrypted using a private key.
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