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Internet

Internet. Networking. Communicating between two or more computers Bits -> voltage ->wire->voltage->Bits. Network. More than two computers. Network switch. More than two computers. Switch. Network. Who is talking to who?. Switch. Network. 1. Who is talking to who?

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Internet

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  1. Internet

  2. Networking • Communicating between two or more computers • Bits -> voltage ->wire->voltage->Bits

  3. Network • More than two computers

  4. Network switch • More than two computers Switch

  5. Network • Who is talking to who? Switch

  6. Network 1 • Who is talking to who? • Give each computer an address (integer) 0 2 Switch 75 43 42

  7. Network 1 • Who is talking to who? • Give each computer an address (integer) • Add the address to the message • Computer with that address takes the message • All others ignore the message 0 2 Switch 75 43 42 message address

  8. Internet net net net net message address

  9. Internet net net net net net ID host ID message address

  10. IP address 128.187.172.236 a computer BYU Computer Science net ID host ID message address

  11. Internet Protocol (IP) • Computer sends an IP “packet” • Other computers (routers) send it on until it reaches the destination computer • (IP address) • Each packet might get lost, may arrive in any order, may get delayed message IP Address 32 bits - 4 bytes

  12. TCP/IP • Uses IP to send packets • Keeps track of which packets have been sent • Resends packets that get lost • Keeps track of the correct order of packets • Reorders packets when they come in the wrong order

  13. Domain names • icie.cs.byu.edu • www.byu.edu • ee.utah.edu • yahoo.com • software.microsoft.com • research.microsoft.com

  14. Domain names • icie.cs.byu.edu • www.byu.edu • ee.utah.edu • yahoo.com • software.microsoft.com • research.microsoft.com com edu yahoo byu utah microsoft ee cs www icie research software

  15. Domain names • If you have a domain name, how do you find the IP address of that computer? • Maybe one computer has a list of all domain names and their IP addresses • If there are millions of computers • Who enters the data? • Who fixes the data? • Millions of requests will swamp that computer • If that computer goes down nothing works • How do we get this to scale?

  16. Domain names - scale • Use a tree! • Every node knows IP address of its parent • Every node knows the IP/domain name of its direct children com edu yahoo byu utah microsoft ee cs www icie research software

  17. DNS - domain name service • If a node doesn’t know the IP address of some domain name • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software

  18. DNS - domain name service • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software icie.cs.byu.edu wants software.microsoft.com

  19. DNS - domain name service • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software icie.cs.byu.edu wants software.microsoft.com icie asks cs

  20. DNS - domain name service • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software icie.cs.byu.edu wants software.microsoft.com cs asks byu

  21. DNS - domain name service • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software icie.cs.byu.edu wants software.microsoft.com BYU asks edu

  22. DNS - domain name service • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software icie.cs.byu.edu wants software.microsoft.com edu asks com

  23. DNS - domain name service • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software icie.cs.byu.edu wants software.microsoft.com com asks microsoft

  24. DNS - domain name service • If the domain name is one of its own, ask the correct child • If the name is not one of its own, ask the parent com edu yahoo byu utah microsoft ee cs www icie research software icie.cs.byu.edu wants software.microsoft.com microsoft knows and gives the answer

  25. DNS - making it fast • Each node remembers the most common requests for a day or two • Doesn’t need to ask again • Called “caching” com edu yahoo byu utah microsoft ee cs www icie research software

  26. DNS - managing the data • Each node can manage and change its own children without consulting anyone else • Within 2 days of the changes, everyone’s cache has been updated com edu yahoo byu utah microsoft ee cs www icie research software

  27. Other protocols • Use TCP/IP • WWW • Email • Instant messenger • FTP

  28. WWW • URL - “icie.cs.byu.edu/dan.html” • Send a message to DNS - “what is icie.cs.byu.edu?” • Use IP address to send a message to “icie.cs.byu.edu” • “GET dan.html”

  29. Email - uses TCP/IP • send a message to “bill_gates@microsoft.com” • find my mail server “mail.cs.byu.edu” • message to “mail.cs.byu.edu” to: bill_gates@microsoft.com from: olsen@cs.byu.edu subject: Hi there • mail server forwards the message to “microsoft.com” • if no answer it will keep trying for about a week

  30. Networking • Sending bytes between computers • IP - sends a packet to a particular IP address • TCP - guarantees that packets are in correct order and not lost • DNS - uses a tree to convert domain names into IP addresses • WWW - uses TCP/IP • Email - uses TCP/IP

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