Computer Networks PDF

Networks Chapter 18 This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Class Objectives 1. Computer Networks 2. Internet 3. Connecting to the Internet 4. World Wide Web 5. Wireless Networks 6. Satellites This content is p...

Networks Chapter 18 This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Class Objectives 1. Computer Networks 2. Internet 3. Connecting to the Internet 4. World Wide Web 5. Wireless Networks 6. Satellites This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Computer Networks This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher What is a computer network? This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher  Medium to connect computers Need a transmission media Physical Wireless This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Most common way to connect computers? This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher LAN Connects devices within a relatively small, single geographic location Two to several hundred devices One geographic area only Communication lines can be placed where the organization wants The distinguishing characteristic of a LAN is that it is in a single location This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Components Switch special purpose computer that receives and transmits messages on the LAN Network Interface Card (NIC) hardware that connects device’s circuitry to the cable MAC address - Unique identifier This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher WLAN This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Other Types of Computer Networks This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher How do we connect Vancouver and Toronto offices? This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher WAN Connect devices at different geographical locations Two or more separated sites Uses communication networks from vendors Licensed by government This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher  WAN Toronto Vancouver Calgary Winnipeg This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Internet www.makeuseof.com This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Internet This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher The Internet and intranets Network of networks, or global WAN Connect LANs, WANs, and other internets The Internet (with an upper-case letter I) is used for emailing and web browsing Intranets are private networks of networks Protocols: to transmit data seamlessly across all these networks, there is a variety of communication methods and conventions are created which are set of rules that communicating devices follow This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher  Internet service provider (ISP): Organization or firm that provides access to the Internet. Providers connect to one another, exchanging traffic and ensuring that messages can get to any other computer that’s online and willing to communicate. The Internet was designed to be redundant and fault-tolerant—if one network, connecting wire, or server stops working, everything else should keep on running. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher The IP Address IP address: Value used to identify a device that is connected to the Internet. The IP address can be used to: Identify a user’s physical location Tailor search results Customize advertising The still widely used format is IPv4 and is expressed as four numbers (from 0-255), separated by three periods: 216.3.128.12 This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Connecting to the Internet This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Cable Broadband coaxial cable: Insulated copper cable used by cable television providers. Has shielding that reduces electrical interference. Allows cable signals to travel longer distances without degrading and with less chance of interference. Limitation—requires customers to share bandwidth with neighbors. Cable is getting faster and cable firms are: Creating so-called fiber-copper hybrids that run high-speed fiber- optic lines into neighborhoods, then use lower-cost but still relatively high-speed, copper infrastructure over short distances to homes. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher DSL: Phone Company Copper digital subscriber line (DSL): Broadband technology that uses the wires of a local telephone network. Speeds vary depending on the technology deployed. Limitation—uses standard copper telephone wiring that lacks the shielding used by cable. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Fiber: A Light-Filled Glass Pipe to Your Doorstep fiber to the home (FTTH): Broadband service provided via light- transmitting fiber-optic cables. Fastest last-mile technology and works easily over long distances. Limitation—need to build fiber infrastructure from scratch and the cost of buildout is enormous. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher How do computers send data over the internet? Computers are digital understand 0 and 1 Telephone lines or Cable copper wires use analog signals and Fibre cables use light How can we transmit digital data from computers over these networks? This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Modem This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Components to connect to WAN or Internet This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher World Wide Web This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher WWW The World Wide Web Not the same thing as the Internet. W3 is an application that uses Internet for transport A system of universally accepted standards for storing, retrieving, formatting, and displaying information via a client/server architecture. Hypertext Transfer Protocol (HTTP) is the protocol used for websites Browser – software application allowing users to access the web This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher The URL: “What Are You Looking For?” URL (uniform resource locator): Identifies resources on the Internet along with the application protocol needed to retrieve it. Often used interchangeably with “Web address.” hypertext transfer protocol (http): Application transfer protocol that allows Web browsers and Web servers to communicate with each other. protocol: Enables communication by defining the format of data and rules for exchange. SMTP, or simple mail transfer protocol, which is a server to hold e-mail. FTP: Application transfer protocol that is used to copy files from one computer to another. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Anatomy of a Web Address This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher So What’s the “s” about in https? Secure Sockets Layer (SSL): A security standard that creates an encrypted link between a Web server and a browser. Websites that use SSL will begin with https (note the ‘s’ at the end). This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Hosts and Domain Names The domain name is the name of the network you’re trying to connect to (usually represents an organization). The host is the computer you’re looking for on that network. Many domains have lots of different hosts. Google’s main website is served from host named “www,” but runs other hosts including those named “finance”, “calendar”, and “drive”, among many others. Host and domains are not case-sensitive. You can use a combination of upper and lower case letters and still get to your destination. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Host and Domain Names Assigning several computers to a host name helps ensure that all visits to a popular site like https://www.google.com won’t overload a single computer. load balancing: Distributing a computing or networking workload across multiple systems in order to avoid congestion and slow performance. It’s also possible for a single computer to have several host names. Some domains are further broken down into subdomains—many times to represent smaller networks or subgroups within a larger organization. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Domains Some generic top-level domain names, like “.com,” have no restrictions on use, while others limit registration. sTLDs: Sponsored top-level domains run by private agencies or organizations with established rules restricting the eligibility of registrants. There are also separate agencies that handle over 250 different two- character country code top-level domains (e.g., ”.jp” for Japan). ccTLDs: Two-character country code top-level domains. There is also another category known as geographic TLDs: Top-level domains that are not two-level country codes, but that are associated with a geographical, geopolitical, ethnic, linguistic, or cultural community. Examples include.cat (for Catalan),.paris, and.asia. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Path Name and File Name If a Web address has a path and file name: The path maps to a folder location where the file is stored on the server. The file is the name of the file you’re looking for. hypertext markup language (HTML): Language used to compose Web pages. Path and file names are case sensitive—mistype capital letters and you might get a 404 error. amazon.com/books is considered different from amazon.com/BOOKS. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher The Internet Is Full—We’ve Run Out of IP Addresses NAT (network address translation): Conserves IP addresses by mapping devices on a private network to single Internet-connected devices that acts on their behalf. Helps delay the impact of the IP address drought but slows down Internet access and is complex, cumbersome, and expensive to administer. Only long-term solution is to shift to a new IP scheme—IPv6 increases the possible address space from the addresses used in the current system. IPv6 is not backward compatible with IPv4 and transition has been very slow. When IPv6 is deployed, some of the benefits may include potentially improving speed, reliability, and security of the Internet. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher The DNS: The Internet’s Phone Book domainINTERNET DIRECTORY name service SERVICE (DNS): Internet THAT directory ALLOWS service that allows devices and services DEVICES to be AND named andTO SERVICES discoverable. BE NAMED AND Distributed database that looks up host and domain names and returns the actual IP address for them. DISCOVERABLE Likened to a big, hierarchical set of phone books capable of finding Web and e- mail servers and more. These “phone books” are called nameservers—and when they work together to create the DNS, they can get you anywhere you need to go online. The system also remembers what’s it’s done so next time your computer can pull this out of a storage space called a cache: Temporary storage space used to speed computing tasks. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Finding an IP Address This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Wireless Networks This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Wireless Mobile wireless service from cell phone access providers is delivered via cell towers. Providers require a wireless spectrum: Electromagnetic frequencies used for wireless communication. Most mobile cell phone services have to license spectrum. High-stakes regional bidding wars whenever governments put new spectrum up for license. More bandwidth is needed for mobile devices. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Average Demand Usage by Function Usage Demand Voice calls 4 MB/hr. Web browsing 40–60 MB/hr. Podcasts 60 MB/hr. YouTube 200–400 MB/hr. Conventional mobile phones use an estimated 100 MB/month, iPhones 560 MB/month, and iPads almost 1 GB/month. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Wireless (continued) Mobile phone services usually have a number, followed by a G (for generation). The bigger the “G,” the faster and more reliable. Incompatible worldwide 3G or third-generation technologies has been replaced by higher-bandwidth 4G (fourth-generation) mobile networks. The winner in 4G technologies is LTE (long-term evolution). U.S. average download speeds above 40 Mbps and upload speeds near 20 Mbps are now common. Source: Bohdan Populov/Shutterstock.com This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher 5G: A Faster Wireless Network, but Not All 5G Is the Same Carriers have begun rolling out 5G services. Faster, more reliable, and have higher overall capacity than 4G networks. Infrastructure and devices needed to be upgraded. Transmission points are much smaller than the massive towers used to support 4G, allowing 5G access to be built in places such as on top of traffic lights. Complications include: Operating expenses are proving much costlier than previously expected. Many 5G firms in the U.S. planned to use technology from the Chinese firm Huawei, which was banned by the Trump Administration. Devices designed to work with certain carriers don’t work with others. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher 5G: A Faster Wireless Network, but Not All 5G Is the Same (continued) 5G may be a catalyst for all sorts of applications: self-driving automobiles emergency response communication Telemedicine “bespoke” network offerings for VR, AR, and high-speed game streaming smart city sensors for things like traffic routing, air and water monitoring, and community safety This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher 5G: A Faster Wireless Network, but Not All 5G Is the Same (continue, 2) A wireless provider's 5G speed is also highly related to the wireless spectrum that the firm has licensed. T-Mobile has been known to have some of the highest and most reliable mobile 5G speeds, working both inside and outside buildings at transfer rates between 100Mbps and 250Mbps. The rise of “5G Home Internet” (5G fixed wireless) An antenna is attached to the side of home or apartment building. Fastest form of fixed 5G, mmWave, uses smaller-wave spectrums Limitation—can’t reliably penetrate building walls This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Satellites This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Satellite Wireless and Schemes to Reach the Remote Terrestrial wireless are provided by earthbound base stations like cell phone towers. Possible via satellite First residential satellite services were only used for downloads Later some services were based on satellites in geosynchronous earth orbit—GEO: Travel at roughly 22,000 miles above the earth’s service. This point keeps them in a fixed orbit synched to a given point on the rotating earth’s surface, but the distance produces a transmission latency of about half a second in each direction. Satellite systems show promise in providing high-speed access to underserved parts of the world, but few satellite broadband providers have been successful so far. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher To Infinity and Beyond: SpaceX Starlink and the Awesome Power Wielded by Elon Musk's Firms One firm has delivered on the promise of globe-spanning broadband— SpaceX through its Starlink effort. Older satellite telecom efforts launched equipment to rotate in GEO over 22,000 above Earth’s surface. Starlink satellites are LEO, spinning around the globe at only about 350 miles up. Starlink is so fast that it is considered by Source: Kent Weakley/Shutterstock.com many to be a viable alternative to terrestrial (ground-based) networks. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher To Infinity and Beyond: SpaceX Starlink and the Awesome Power Wielded by Elon Musk's Firms (continued) Since equipment is no longer in a fixed position above a spot, satellites zoom in and out of range Pass signals to each other using lasers On the ground, customers use pizza-box-sized antennas that reposition based on the extraterrestrial dance of transmission equipment above. Starlink has over 4,500 operational commercial satellites. SpaceX plans to launch over 42,000 satellites in the next few years. Launches have been occurring roughly once a week, with as many as sixty satellites sent skyward each time. Residential customers are currently averaging above 75 Mbps download and 12 Mbps upload for Starlink’s lowest-cost plan. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher To Infinity and Beyond: SpaceX Starlink and the Awesome Power Wielded by Elon Musk's Firms (continued, 2) Many stakeholders worry about Starlink's overwhelming footprint and the risk for collision that might set off a cascading catastrophe. Kessler Effect: A feared cascading effect when colliding space debris hits existing objects, creating additional debris and additional collisions. Some claim the light pollution from Starlink’s Source: Ke.Be/Shutterstock.com network makes it more difficult to observe objects that might collide with Earth. Others claim Starlink satellites interfere with their ability to conduct basic ground-based astronomy using earthbound telescopes. This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher To Infinity and Beyond: SpaceX Starlink and the Awesome Power Wielded by Elon Musk's Firms (continued, 3) Musk thinks Starlink will tap into a huge market. 42 million people in rural U.S. lack access to high-speed broadband About 3 billion people planet-wide aren’t yet online Currently available on every continent Widely used throughout the globe, and enabler for regions that have no access or have lost access to the Internet due to war or disaster— This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher Thank you! This content is protected and may not be shared, uploaded, or distributed © Ahmad Bisher