What Is the Internet?

Transcription

1 Ch 3B: The Internet

2 What Is the Internet? The Internet is a network of independent but connected devices all over the world. People talk as if "the Internet" and "the World Wide Web" are the same thing, but they are not. The World Wide Web is the collection of interlinked website documents (such as HTML files) that you can view with a web browser by typing addresses like: Most web pages are written with HTML (hypertext markup language) and interpreted by your browser using HTTP (hypertext transfer protocol).

3 How did the Internet get started? Let s start our tech timeline! Mark your birthday on the timeline Mark your first device (Gameboy, Gamecube, ipod, etc) on your timeline Mark and label your current device(s) on the date for the current year

4 The internet has its roots in a U.S. Department of Defense project. It transitioned into a nonprofit civilian operation. Here are some dates you should be familiar with: 1957 The Soviet Union launched Sputnik, the first man-made satellite. In response to this show of Soviet superiority, the U.S. government resolved to improve scientific and technical infrastructure. ( New Math period a result of this). Another resulting initiative was the Advanced Research Projects Agency (ARPA) 1969 the ARPANET was created to help scientists communicate and share valuable computer resources. It connected the computers at UCLA, the Sandford Research Institute the University of Utah, and UCSB

5 The National Science Foundation (NSF) used ARPANET technology to create a larger network, linking entire Local Area Networks (LANs) at each site. ***Linking two or more networks creates an internetwork, or internet. 1990s software developers created new user-friendly Internet access tools because before that, finding information was NOT easy and access was limited to a limited number of educators and scientists. Accounts also became available to anyone willing to pay a monthly subscription fee.

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7 How big is the internet today? Today, the book estimates 500 million nodes and more than 2 billion users. Estimated that the Internet handles more than an exabyte (1,074 gigabytes) of data every DAY.

8 Who oversees the internet today? No single person, organization, company, or government runs the internet. At one time, the internet was composed of many regional networks, established in countries throughout the world. Gradually, these networks have fallen under the control of large telecommunications companies (EX Comcast, AT&T, NTT Communications)

9 The glue that holds the internet together is a set of standard protocols Each country can develop laws, policies, and regulations for networks within their jurisdiction. Local governments can shut down servers in their jurisdiction that violate copyright laws and distribute inappropriate content. However, every internet node MUST have a unique address in order to send and receive data (assigned by ICANN) These set of standard protocols were developed to make it possible for data to travel across borders, called Internet governance. Evolved through common agreement among network providers.

10 What is ICANN? ICANN is The internet corporation for Assigned Names and Numbers This organization supervises Internet addressing. It is headquartered in Los Angeles and subject to oversight by the U.S. Department of Commerce. It has the power to globally shut down access to a server In 2014, the Department of Commerce sought approval to transfer its authority to an international organization.

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12 What is the Internet Infrastructure? A network of networks, organized into tiers. Tier 1 networks are at the top of the hierarchy, followed by Tier 2 and Tier 3 networks. As a consumer, you are subject to the fees, policies, and technologies of the tiers that provide you service. The way these networks fit together is referred to as the Internet Infrastructure. Tier 1 networks form the internet backbone: AT&T CenturyLink Verizon NTT Communications. ****These have a system of high capacity routers and fiber-optic communication links providing the main routes for data speeding across the Internet.

13 Networks that form the Internet are maintained by Internet Service Providers (ISPs) that supply routers and other data communication equipment, as well as physical and wireless channels to carry data. ISPs exchange data at Internet exchange Points (IXPs) Tier 2 or Tier 3 networks are generally what consumers connect to. Comcast Merit Swiss-Com

14 The internet is NOT free. ISPs make a substantial investment in equipment and the cable or wireless infrastructures to connect consumers. The largest providers have close to 200,000 miles of cables installed across continents and over the ocean floor. They also are subject to transport fees, especially when shipping u through higher tiers. That is why consumers are charged for access

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17 What is a packet? Files are chopped up into small pieces called packets. A packet is a parcel of data that is sent across a computer network. Each packet contains the address of its sender, the destination address, a sequence number, and some data. When packets reach their destination, they are reassembled into the original message according to the sequence of numbers.

18 Packet Switching Divides a message into several packets that can be routed independently to their destination. Packets from many different messages can share a single communication channel, or circuit. Packets are shipped over the circuit on a first-come, first-served basis. If some packets from a message are not available, the system does not need to wait for them. Instead, the system moves on to send packets from other messages. The result is a steady stream of data.

19 The Internet: Packets, Routing and Reliability 5DDxco3UdsFegvuB7&index=4 Is the Internet made up of made of direct, dedicated connections? Do packets travel along the Internet on a fixed path? Each packet has the Internet address of and. Where its going Where it came from Special computers on the Internet called act like traffic managers to keep packets moving through networks smoothly. If one route is congested, individual packets may travel routes. As part of the, every router keeps track of multiple paths for sending packets, and it chooses the cheapest available path for each piece of data based on destination IP address for the packet. Often the best route for data to travel isn't necessarily the most. Having options for paths makes the network. This is the basis for a key principle of the Internet is. Transmission Control Protocol (TCP) Internet Protocol (IP) routers manages the sending and receiving of all your data as packets. No No, it might even change in the midst of a computer to computer convo Different Fault Tolerant direct Reliability

20 How are packets created? TCP (Transmission Control Protocol) is responsible for dividing files into chunks, adding headers containing the info for reassembling packets, and verifying that the data was not corrupted in transit (error checking). When TCP is used, data will reliably reach its destination. User Datagram Protocol (UDP) is faster than TCP but does not perform error checking and cannot reorder packets if the are received out of order. These are suitable mostly for applications in which a little bit of data lost is not critical, such as streaming video and music, or internet-based multiplayer games and voice calls.

21 What is a communications port? A communication port is a virtual (so not physical) end point for data entering and leaving a digital device. It is an abstract concept of a doorway into which data flows. Ports work in conjunction with Internet Addresses. Computers can have up to 65,535 ports. When ports are open, data is allowed to flow freely. Ports create simulated end-to-end connections on packet-switching networks. Ports create a conceptual circuit for each type of data, as shown in the figure below

22 There and Back Again

23 Due Thursday

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25 What are Internet Addresses? Most of us think of URLS like but those these are not the underlying addresses used to transport data! Internet addresses are controlled by Internet Protocol (IP), which, along with TCP, is part of the Internet Protocol Suite. Every device on the Internet needs and IP address. IP defines two sets of addresses: IPv4 and IPv6 IPv4 is the Internet address standard that has been used since the 1980s. IPv4 uses 32 bit addresses to uniquely identify devices connected to the internet, offering 4 billion unique addresses. They are often written in decimal as four sets of three digits separated by periods.

26 4 billion might be a lot, but in 2011 that supply of addresses was completely allocated. IP addresses can be reused, but it still wasn t enough. So, another set of addresses was needed. IPv6 uses 128 bits for each address. They are often written as eight groups of four hexadecimal digits.

27 A URL, or Uniform Resource Locator, is an address for accessing specific web data located on a server (a computer hosting data for others to access). URLs can be broken into three parts:

28 The Internet: IP Addresses and DNS The Internet is a network of. The Internet is a design philosophy and an architecture expressed as a set of. A protocol is Networks Protocols A set of standards that will allow communication without trouble (if all agree to follow the rules/standards) What does a new technology need to know to use the Internet? It needs to know which protocols to use. All the different devices on the Internet have. Unique addresses What is one of the most important protocols on the Internet? Internet Protocol (IP) IP address A computers address is called. Example: Traditional IP Addresses are how long? How many bits for each part? Describe IPv4 How many bits are used by IPv6? What is DNS? Explain what it does. How are DNS servers connected? Why is DNS susceptible to cyber attacks? What is DNS spoofing? 32 bits long With 8 bits for each part Designed in 1973 Provides for more than 4 billion devices 128 bits Domain Name system. Your computer uses DNS to connect you with your internet destination. Distributed hierarchy (split up,gov,.net,.com, etc ) Originally created to be an open and public communication protocol for gov and educational purposes A hacker taps into a DNS server and changes it to match a domain name with a the wrong IP address.

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31 A Static Address is an IP address that is permanently assigned. Generally used by routers and computers on the Internet that act as servers Also used by ISPs, Web sites, Web hosting services, and servers that always need to be found at the same addresses A dynamic address is when an internet address is temporarily assigned to a device. When the device is turned off or the Internet connection is disables, the address can be recycled to another device. When the device is turned on, it is assigned a different IP address. In practice, these actually don t change very often

32 How do devices get IP addresses? An IP address is commonly automatically assigned by DHCP (Dynamic Host Configuration Protocol). Most devices are preconfigured to receive an IP address by sending a query to the network device acting as the DHCP server (EX: a local area network router). A private IP address can be allocated by any network without supervision from ICANN. However, it cannot be used to send data over the Internet. So, the data that you want to send must go through the router, which has a public IP address which is routable.

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35 The Internet was designed to be: Redundant: There are multiple pathways among the physical connections of the Internet to create redundancy. Even if one pathway is unavailable, there is still another way to transmit a message from sender to receiver. (remember Ch 3A) Hierarchical: A hierarchy is an arrangement of things with the broadest or highest category at the top and things ranked into subcategories below. These address hierarchies works like the postal system, which locates people first by state, then city, then street, then house number, then apartment, and then finally person

36 There are two hierarchical addressing systems on the Internet: domain names and IP addresses. People use domain names (like snap.berkeley.edu) to visit websites because they are easier to remember. A domain name is an easy-to-remember Internet destination such as or ceo@nike.com The mechanism for tracking domain names and their corresponding IP addresses is called the domain name system (DNS) Computers translate those domain names to IP addresses (like ) to locate and send data behind the scenes.

37 What is the domain name system? Domain Name Servers (DNS) servers are scattered around the world and maintain lists of all domain names and their corresponding IP addresses. Any user's computer only has to know where to find a root domain server (the one that knows where to find the top-level domains such as.org and.edu), and that server knows where to find the domain (like berkeley.edu), and that server knows where its subdomains are (like snap.berkeley.edu), and so on.

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39 What is a top-level domain? A domain name ends with an extension that indicates its top-level domain. Historically, the following holds true: Businesses use.com (Businesses often try to obtain all top-level domain names (Ex: nike.com, nike.org, nike.edu) to prevent fake businesses. ) Nonprofits use.org Educational institutes use.edu

40 Country codes also serve as top-level domains such as: Canada.ca United Kingdom.uk Australia.au Today, there are more top-level domains such as:.biz.co.fit.university.guru..and many more

41 The root domain may be a country code (such as.mx for Mexico) or a category code (like.gov for government). The last two segments of a domain name (like berkeley.edu) make up the primary domain, the main address for a site. Subdomains are subsections of primary domains or of other subdomains. For example:

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43 What are DNS weaknesses? DNS Spoofing is unauthorized changes to the DNS. Altering the DNS records can change the destination of the , browser connections, and download requests. Hackers use DNS spoofing so that queries for legitimate sites are directed to fake sites.

44 Weakness Cont. Domain name servers can be turned off. More commonly, a DNS server operated by your ISP will go offline because of equipment failure. You might be able to bypass DNS outages, blocks, and hacks by changing your DNS server because errors in the domain name tables might be limited to the domain name server you are using.

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