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The Internet

This article explores the fundamental concepts of the Internet, including packet switching, routing, and addressing. It delves into how data is transmitted using protocols like TCP/IP, the role of routers, and the significance of IP addresses in facilitating digital communication. By breaking down complex technical jargon, the piece aims to make Internet technology accessible to those learning in retirement or anyone seeking a comprehensive overview of the evolution of the web.

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The Internet

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  1. The Internet Making a Connection: Packet Switching, Addressing and Routing

  2. Host Computer or Terminal An Internet Router Learning in Retirement - The Evolution of the Web

  3. The Internet • The Internet, or more correctly, • a digital packet-switched network using the TCP/IP set of protocols, • is • A collection of hosts (computers and other information devices) • connected by a variety of digital communications networks, consisting of • digital communication links and • switches, which are called routers. Learning in Retirement - The Evolution of the Web

  4. Protocols • Information is transmitted on the Internet as binary information, 1’s and 0’s, under the control of standardized procedures called protocols. Learning in Retirement - The Evolution of the Web

  5. The TCP/IP Suite of Protocols • Originated with ARPANET and DDN to meet US DoD requirements • Survivability • no central point of failure security • Network interoperability • accommodate heterogeneous networks and equipment • Ability to handle surge traffic • Allow priority • Be always available Learning in Retirement - The Evolution of the Web

  6. Sending Information on the Internet • Every entity (computer or router) on the Internet has an address. • The address is a 32-bit binary number • 10000110010101011111111011100011 • The IP address is usually expressed in dotted decimal form • 134.117.254.227 • Part of the address is the NetID and the remainder the HostID Learning in Retirement - The Evolution of the Web

  7. Packets • The message to be sent is packaged into packets • A packet is a like an envelope that holds a block of data • Each packet includes • The address of the sender • The address of the destination Learning in Retirement - The Evolution of the Web

  8. If the message is short • it is sent in one packet • If not • it is fragmented and • sent in a secession of packets. Learning in Retirement - The Evolution of the Web

  9. Routing (Switching) • Packets are sent independently from router to router • Each router determines the next router to be used by consulting a local directory called a routing table Learning in Retirement - The Evolution of the Web

  10. Routing at Host • If the NetID is the same as that of the originating host, the packet is handled locally • IP address is converted to the physical address of the host and the packet delivered • If not the same, a memory-resident routing table is consulted to determine next recipient of the packet Learning in Retirement - The Evolution of the Web

  11. Routing at Router • The NetID is analyzed to determine if this is last hop. • If not, the IP of the local router (using memory-resident tables) selects the best path to the destination • Packet is encapsulated again and sent one hop closer to final destination • And so on Learning in Retirement - The Evolution of the Web

  12. Routing Information • Hosts maintain sufficient information to forward packets to other hosts or interior routers within the same network • Interior routers maintain sufficient information to forward packets to hosts within the same system • Exterior routers maintain sufficient information to forward packets to other interior or exterior routers Learning in Retirement - The Evolution of the Web

  13. Routing Tables • Each router keeps its memory-resident tables with an optimum path to every destination in the system • Routing-table update involves exchange of routing table information between routers using a built-in data communications system called ICMP. • Every router in the Internet does this call the time!!!! Learning in Retirement - The Evolution of the Web

  14. Internet Control Message Protocol: ICMP • Provides feedback about problems in the communications environment • Error reporting • Reachability testing • Congestion Control Learning in Retirement - The Evolution of the Web

  15. Datagram Delivery Learning in Retirement - The Evolution of the Web

  16. Error Control • The network makes no effort to detect or correct errors in the transmitted data. • It is up to the recipient to detect errors and ask for retransmission. • This end-to-end task is handled by TCP, or the Transmission Control Protocol Learning in Retirement - The Evolution of the Web

  17. Transmission Control Protocol (TCP) • TCP provides traditional connection oriented data communications service to programs - the reliable stream transport service • TCP provides a virtual circuit, called a connection • provides flow control, error checking and interrupt capability Learning in Retirement - The Evolution of the Web

  18. TCP Services • Multiplexing • Connection Management • establish • maintain • terminate • Data Transport • Full-duplex • Timely • Ordered • Labeled • Flow controlled • Error checked Learning in Retirement - The Evolution of the Web

  19. The Domain Name Service - DNS • DNS is a hierarchical collection of directories (databases) that play a vital role in the Internet. • DNS is the directory of IP addresses, that contains the names associated with IP addresses. • Names, like sce.carleton.ca allow people to use the Internet. Learning in Retirement - The Evolution of the Web

  20. Finding an IP Address • When ask my browser to open a web page at www.sce.carleton.ca, a query is sent by my computer to the nearest DNS server (at my ISP) • If it knows the IP address it sends it back to my computer, otherwise it sends a query to the next level DNS server, maybe .ca • This continues until an answer is found or not. Learning in Retirement - The Evolution of the Web

  21. When a match is found, say 134.117.4.60 or whatever, the IP address is sent to my computer, which sends a connect message to the web site using this IP address. • Every interaction with the Internet goes through the same process. • How can the Internet sustain – and increase - its capacity???? Learning in Retirement - The Evolution of the Web

  22. THE INTERNET TCP/IP PROTOCOLS PACKET-SWITCHED NETWORKS email: Simple Mail Transport Protocol (SMTP) File Transfer Protocol (FTP) telnet: remote terminal access Internet Control Message (ICMP) Protocol DNS Domain Name Service Learning in Retirement - The Evolution of the Web

  23. Moving on Learning in Retirement - The Evolution of the Web

  24. Paths to Evolution • Fundamental Technologies • Electronics • Communications • Software • Systems Engineering • Provide better ways • to organize and use • faster processors with • more memory • at lower cost Learning in Retirement - The Evolution of the Web

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