Search Engine Indexing PageRank equation: PR(A) = ( 1-d ) + d( PR(Ti)/C(Ti) + ... + PR(Ti)/C(Tn) ) 1. What is the dampening factor? 2. What is PR(X)? 3. What is C(X) 4. What is Ti to Tn?

1. The probability a user does not follow any links, normally set to 0.85 2. The PageRank of X 3. Number of outbound links on page X 4. Incoming pages

Section 5 - Networks and Web Technologies Flashcards by Rose Rutledge

Search Engine Indexing

What is a search engine?

Systems that locates resources on the Internet

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Search Engine Indexing

What is an index?

A record of the resources located on the Internet/World Wide Web

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Search Engine Indexing

What is a web crawler/spider?

Software that creates an index

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Search Engine Indexing

What process does the web crawler go through?

Visits a web page and follows all the links on that page
Then follows all the links on those pages
Repeat

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Search Engine Indexing

What are meta tags?

A list of keywords or concise phrases specified by the website owner that are built into each webpage which effect the chances of a webpage from being found during a search

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Search Engine Indexing

What factors effect a page’s chance of being placed high in the results list?

Keywords in the <title> tag</title>
The age of your website and date of last update (or frequency of updates)
The number and relevancy of keywords appearing in <h1> tags and
The relevancy of the domain name to the conten
PageRank

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Search Engine Indexing

PageRank equation:
PR(A) = ( 1-d ) + d( PR(Ti)/C(Ti) + … + PR(Ti)/C(Tn) )

What is the dampening factor?
What is PR(X)?
What is C(X)
What is Ti to Tn?

The probability a user does not follow any links, normally set to 0.85
The PageRank of X
Number of outbound links on page X
Incoming pages

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Search Engine Indexing

What steps are taken using the PageRank algorithm to find the PageRank of multiple unknowns?

Start by guessing each PageRank as 1
Substitute the values into the PageRank equation
Update the guesses based on the answer
Repeat until the guesses and the answers match

EXAMPLE
Iteration 1:
PR(A) = 0.15 + 0.85( 1/3 + 1/1 ) = 1.283
PR(B) =0.15 + 0.85( 1/1) = 1
PR(C) =0.15 + 0.85( 1/3 ) = 0.433
PR(D) = 0.15 + 0.85( 1/3 ) = 0.433

Iteration 2:
PR(A) = 0.15 + 0.85( 1/3 + 0.433/1 ) = 0.801PR(B) =0.15 + 0.85( 1.283/1) = 1.241
PR(C) =0.15 + 0.85( 1/3 ) = 0.433
PR(D) = 0.15 + 0.85( 1/3 ) = 0.433

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Structure of the Internet

What is a Uniform Resource Locator (URL)?

The full address of an Internet resource

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Structure of the Internet

What is an internet registrar?

A company that holds records of all existing website names and the details of those domains that are currently available to purchase

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Structure of the Internet

What is an internet registry?

A global organisation governed by the Internet Corporation for Assigned Names and Numbers (ICANN)
Has worldwide databases that hold records of all the domain names currently issued to individuals and companies, as well as their details
Allocate IP addresses and keep track of which address(es) a domain name is associated with as part of the Domain Name System (DNS)

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Structure of the Internet

What is the Domain Name System (DNS)?

A catalogue of all domain names and IP addresses in a series of global directories

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Structure of the Internet

What does a domain name do?

Identifies the area/domain that an internet resource resides in

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Structure of the Internet

What is a Fully Qualified Domain Name (FQDN)?

A domain name is one that includes the host server name
(e.g. www, mail, ftp)

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Structure of the Internet

What is an Internet Protocol (IP)?

A unique address that is assigned to a network device

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Internet Communication

What is a MAC address?

A unique identifier assigned to a Network Interface Controller (NIC)

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Structure of the Internet

What is a Wide Area Network (WAN)?

A network spread over a large geographical area

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Structure of the Internet

What is a Local Area Network (LAN)?

A network that consists of a number of computing devices on a single site or in a single building

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Structure of the Internet

What is physical bus topology?

A LAN topology where all computers are connected to a single cable

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Structure of the Internet

What is the advantage of using bus topology?

1 point

Inexpensive to install as it requires less cable and no additional hardware

Structure of the Internet

What are the disadvantages of using bus topology?

If the main cable fails, network data can no longer be transmitted to any nodes
Performance degrades with heavy traffic
Low security - all computers on the network can see all data transmissions

Structure of the Internet

What is physical star topology?

A network that has a central node - a switch or computer that acts as a router to transmit messages

Structure of the Internet

What does a switch do in a network?

A switch keeps a record of the unique MAC address of each device on the network and can identify which particular computer it should send data to

Structure of the Internet

What are the advantages of using star topology?

If one cable fails, only one station is affected - faults are isolated
Consistent performance
Higher transmission speeds give better performance
No data collisions since each station has its own cable to the server
More secure, as messages are sent directly to the central computer and cannot be intercepted by other stations
Easy to add new stations without disrupting the network

# Structure of the Internet What are the disadvantages of using star topology?

* May be costly to install due to the length of cable required * If the central device goes down, network data can no longer be transmitted to any nodes

# Structure of the Internet What is physical topology?

The design layout of the network cables/nodes

# Structure of the Internet What is logical topology?

The shape of the path the data travels in, as well as how components communicate

# Structure of the Internet What is Wi-Fi?

A local area wireless technology that enables devices to connect to a network resource or the Internet via a Wireless Network Access Point (WAP)

# Structure of the Internet What is a Wireless Network Access Point (WAP)?

A networking device that allows wireless devices to connect to a wired network

# Internet Communication What are the 4 layers of the TCP/IP stack?

1. Application 2. Transport 3. Network / Internet 4. Link

# Internet Communication What happens at the application layer of the TCP/IP stack?

* The appropriate protocol for communication is selected * (HTTP, HTTPS, FTP, etc.)

# Internet Communication What happens at the transport layer of the TCP/IP stack?

* Establishes a connection between the sending and receiving computers * The data to be sent is split into packets, each with a packet number, total packet count, and port number * If any packets are lost, this layer requests to resend them

# Internet Communication What is a port?

A port can be used to ensure the correct application is used when receiving data

# Internet Communication What happens at the network / internet layer of the TCP/IP stack?

* Both the sender's and the recipient's IP addresses are added to the packets * The data packets are sent across different routers until they reach their destination

# Internet Communication What happens in the link layer of the TCP/IP stack?

* Both the sender's and recipient's MAC addresses are added to the packets

# Internet Communication What happens once all 4 layers of the TCP/IP stack of been completed?

The steps of the stack are reversed at the recipient's computer: 1. The MAC addresses are removed 2. The IP addresses are removed 3. The port number is removed and the packets are reassembled 4. The reassembled data is then presented to the user on the application

# Internet Communication What is packet switching?

A method of communicating in which packets of data are sent across a network where other similar communications are happening simultaneously

# Internet Communication What is circuit switching?

A method of communicating in which a direct link is created between two devices for the duration of the communication

# Internet Communication What is a gateway used for?

When protocols differ between networks, a gateway is used rather than a router to translate between them

# Internet Communication What is a router used for?

Routers are used to connect at least two networks (e.g. two LANs or WANs) or to connect a LAN and its ISP’s network

# Network Security and Threats What is a firewall?

A security checkpoint designed to prevent unauthorised access between two networks

# Network Security and Threats What is packet / static filtering?

A method of controlling network access according to network administrator rules and policies by examining the source and destination IP addresses in packet headers

# Network Security and Threats What is a proxy server?

A server that intercepts all packets entering and leaving a network, hiding the network addresses of the source from the recipient, enabling privacy and anonymous surfing

# Network Security and Threats What are the 3 types of malware?

* Worm * Virus * Trojan

# Network Security and Threats What is a virus?

Viruses are capable of duplicating and spreading themselves, relying of a user to open a file in order to begin self-replicating Most viruses are stored within memory once opened, and will proceed to infect any other opened files from within the memory

# Network Security and Threats What is a worm?

Worms are capable of duplicating and spreading themselves, but do not rely on a user's interaction (e.g. opening a file) to begin doing so A worm can replicate itself and send copies to other users from a computer, typically via email

# Network Security and Threats What is a trojan?

A trojan is often hidden within files and causes few visible problems, instead acting as a back door to your computer system that the trojan's creator can exploit

# Network Security and Threats List all potential security vulnerabilies

* Phising scams (trickery used to obtain a password or other sensitive information) * Weak passwords * Lack of firewall/antivirus software * Administrative rights failing to prevent access to certain file areas * Cracks in software where data is passed from one subroutine/application to another * Buffer overflow (occurs where a program accidentally writes values to memory locations too small to handle them, inadvertently overwriting the values in neighbouring locations that it is not supposed to have access to)

# Internet Communication What is a protocol?

A set of rules that govern communication on a network