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Networks

Networks. 15. Connecting Computers Using the Telephone Network. Local Computer. Remote Computer. CPU. CPU. Memory. Serial Port. Serial Port. Memory. Modem. Modem. Switched Telephone Network. Ethernet (CSMA/CD). Asynchronous C arrier S ense M ultiple A ccess

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Networks

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  1. Networks 15 Operating Systems: A Modern Perspective, Chapter 15

  2. Connecting Computers Using the Telephone Network Local Computer Remote Computer CPU CPU Memory Serial Port Serial Port Memory Modem Modem Switched Telephone Network Operating Systems: A Modern Perspective, Chapter 15

  3. Ethernet (CSMA/CD) • Asynchronous • Carrier Sense • Multiple Access • Collision Detection • Backoff Operating Systems: A Modern Perspective, Chapter 15

  4. Wireless • IEEE 802.11 (“WiFi”) • IEEE 802.15 (“Bluetooth”) Backbone Ad hoc networks Operating Systems: A Modern Perspective, Chapter 15

  5. Stop-and-wait Flow Control Sender transmits a frame; Sender sets a time-out on the transmission; Sender waits for an ACKnowledgment; ... if (Sender receives ACKnowledgment) continue; if (frame times-out) Retransmit timed-out frame; (a) Transmitter Receiver accepts the frame; Receiver transmit the ACKnowledgment; (b) Receiver Operating Systems: A Modern Perspective, Chapter 15

  6. ISO OSI Model Network Network Data Link Data Link Physical Physical Examples • Physical/Data Link layer networks: Ethernet, Token Ring, ATM • Network layer net: The Internet Operating Systems: A Modern Perspective, Chapter 15

  7. Network Layer • Primary purpose is to combine networks • Internet protocol (IP) is dominant protocol • Creates an internet address space • Implements packet routing across networks Host X Network A Network B Network C Host R Host S Host Y Operating Systems: A Modern Perspective, Chapter 15

  8. Addressing & Routing Host X 3b4e87 3b6209 Network A Network C 3b4e62 3b4e55 3b621a Host R Host Y • Host X does not know how to send to Host Y • Can send a frame to Host R for forwarding • What should it tell Host R? Operating Systems: A Modern Perspective, Chapter 15

  9. Addressing & Routing 128.123.234.033 128.229.244.109 Host X To: 128.229.244.006 From: 128.123.234.033 Network Layer data 3b4e87 3b6209 Network A Network C 3b4e62 3b4e55 3b621a Host R Host Y 128.123.234.063 128.123.234.188 128.229.244.006 • Host X does not know how to send to Host Y • Can send a frame to Host R for forwarding • What should it tell Host R? • Internet address spans all machines Operating Systems: A Modern Perspective, Chapter 15

  10. Addressing & Routing 128.123.234.033 To: 3b4e55 From: 3b4e87 128.229.244.109 Host X To: 128.229.244.006 From: 128.123.234.033 Network Layer data 3b4e87 3b6209 Network A Network C 3b4e62 3b4e55 3b621a Host R Host Y 128.123.234.063 128.123.234.188 128.229.244.006 • Host X does not know how to send to Host Y • Can send a frame to Host R for forwarding • What should it tell Host R? • Internet address spans all machines • Send encapsulated packet to Host R with Host Y Operating Systems: A Modern Perspective, Chapter 15

  11. Addressing & Routing 128.123.234.033 128.229.244.109 Host X 3b4e87 3b6209 Network A Network B Network C 3b4e62 3b4e55 3b621a Host R Host S Host Y 128.123.234.063 128.123.234.188 128.229.244.006 • Host X does not know how to send to Host Y • Can send a frame to Host R for forwarding • What should it tell Host R? • Internet address spans all machines • Send encapsulated packet to Host R with Host Y Operating Systems: A Modern Perspective, Chapter 15

  12. Addressing & Routing 128.123.234.033 128.229.244.109 Host X 3b4e87 3b6209 Network A Network B Network C To: 3b621a From: ... 3b4e62 3b4e55 3b621a Host R Host Y To: 128.229.244.006 From: 128.123.234.033 Network Layer data 128.123.234.063 128.123.234.188 128.229.244.006 • Host X does not know how to send to Host Y • Can send a frame to Host R for forwarding • What should it tell Host R? • Internet address spans all machines • Send encapsulated packet to Host R with Host Y • Data Link frame is received by Host Y Operating Systems: A Modern Perspective, Chapter 15

  13. ISO OSI Model Transport Transport Network Network Data Link Data Link Physical Physical Examples • Physical/Data Link layer networks: Ethernet, Token Ring, ATM • Network layer net: The Internet • Transport layer net: TCP-based network Operating Systems: A Modern Perspective, Chapter 15

  14. ISO OSI & TCP/IP ISO OSI Session ISO OSI Session ISO OSI packet ISO OSI packet ISO OSI TLI ARPAnet TCP ISO OSI frame IP frame ISO OSI Network ARPAnet IP Ethernet packet MAC Ethernet Operating Systems: A Modern Perspective, Chapter 15

  15. Domain Name Server (DNS) .edu First-Level Domain • Supports TCP • Uses UDP .colorado .edu Domain .cs .colorado Domain anchor neon pawnee .cs Domain Operating Systems: A Modern Perspective, Chapter 15

  16. Sharing Names Transport Layer Global Address Space (5623, 56, 2046) (3456, 77, 6785) (9876, 88, 3434) (31978, 12, 1234) send(…,(31978, 12, 1234), …); Process A on Host #12 on Net #31978 Process A Process B 0x001a4772 Bind Port 1234 The OS on Host #12 on Net #31978 Operating Systems: A Modern Perspective, Chapter 15

  17. FTP HTTP NV TFTP UDP TCP IP NET NET NET ■ ■ ■ 1 2 n Internet and Protocols Internetworking = Internet Protocol Model Session Transport Network Data Link Physical Operating Systems: A Modern Perspective, Chapter 15

  18. UDP • Datagram (“connectionless”) service • Similar to disk I/O level of service • Logically associated with an IP packet & Data Link frame (but not physically) • Best-effort delivery of datagrams, but: • Datagram may be dropped (lost) • Datagrams may be delivered out of order • Efficient, relative to TCP Operating Systems: A Modern Perspective, Chapter 15

  19. UDP: Connectionless  Definitions -- Connectionless Connectionless is modeled after the postal system. Each message (letter) carries the full destination address, and each one is routed through the system independent of all the others Operating Systems: A Modern Perspective, Chapter 15

  20. TCP • Connected (or virtual circuit) protocol • Interface allows programmer to read/write a byte stream over the network • Byte stream is mapped into a series of packets • Reliable delivery • Each packet must be acknowledged • Effectively 2 packets per transmission • Must open/close a connection before use Operating Systems: A Modern Perspective, Chapter 15

  21. TCP: Connection-Oriented  Definitions -- Connection-Oriented Connection-oriented service is modeled after the telephone system Pick up & dial the number Talk Hang up Operating Systems: A Modern Perspective, Chapter 15

  22. ISO OSI Model Presentation Presentation Session Session Transport Transport Network Network Data Link Data Link Physical Physical Examples • Physical/Data Link layer networks: Ethernet, Token Ring, ATM • Network layer net: The Internet • Transport layer net: TCP-based network • Presentation/Session layer net: http/html, RPC, PVM, MPI Operating Systems: A Modern Perspective, Chapter 15

  23. ISO OSI Model Application Application Presentation Presentation Session Session Transport Transport Network Network Data Link Data Link Physical Physical Examples • Physical/Data Link layer networks: Ethernet, Token Ring, ATM • Network layer net: The Internet • Transport layer net: TCP-based network • Presentation/Session layer net: http/html, RPC, PVM, MPI • Applications, e.g., WWW, window system, numerical algorithm Operating Systems: A Modern Perspective, Chapter 15

  24. A Firewall Internet Firewall Organization’s Intranet Internal Host Internal Host Internal Host Internal Host Operating Systems: A Modern Perspective, Chapter 15

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