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 Who is talking to who? Give each computer an address (integer) Switch 0 1 2 75 4243

7. Network 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 Switch 0 1 2 75 4243 messageaddress

8. Internet message address net

9. Internet message address net net IDhost ID

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

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 edu com byuutah yahoo microsoft cswww icie software research ee

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 edu com byuutah yahoo microsoft cswww icie software research ee

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 edu com byuutah yahoo microsoft cswww icie software research ee

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 edu com byuutah yahoo microsoft cswww icie software research ee 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 edu com byuutah yahoo microsoft cswww icie software research ee 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 edu com byuutah yahoo microsoft cs www icie software research ee 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 edu com byu utah yahoo microsoft cs www icie software research ee 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 edu com byu utah yahoo microsoft cs www icie software research ee 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 edu com byu utah yahoo microsoft cs www icie software research ee 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 edu com byu utah yahoo microsoft cs www icie software research ee 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” edu com byuutah yahoo microsoft cswww icie software research ee

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 edu com byuutah yahoo microsoft cswww icie software research ee

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