1. Slide 15-1 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 15 Networks

2. Slide 15-2 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Connecting Computers Using the Telephone Network Serial Port Serial Port Memory CPU Serial Port Serial Port Memory CPU Switched Telephone Network Modem Local ComputerRemote Computer

3. Slide 15-3 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Ethernet (CSMA/CD) Asynchronous Carrier Sense Multiple Access Collision Detection Backoff

4. Slide 15-4 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Wireless Backbone IEEE 802.11 (“WiFi”) IEEE 802.15 (“Bluetooth”) Ad hoc networks

5. Slide 15-5 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 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

6. Slide 15-6 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 ISO OSI Model Network Data Link Physical Network Data Link Physical Physical/Data Link layer networks: Ethernet, Token Ring, ATM Network layer net: The Internet Examples

7. Slide 15-7 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 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 Host R Host S Host Y Network BNetwork CNetwork A

8. Slide 15-8 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Addressing & Routing Host X Host R Host Y Network CNetwork A 3b4e87 3b4e623b4e553b621a 3b6209 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?

9. Slide 15-9 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Addressing & Routing Host X Host R Host Y Network CNetwork A 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 3b4e87 3b4e623b4e553b621a 3b6209 128.123.234.033 128.123.234.188128.229.244.006 128.229.244.109 128.123.234.063 To: 128.229.244.006 From: 128.123.234.033 Network Layer data

10. Slide 15-10 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Addressing & Routing Host X Host R Host Y Network CNetwork A 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 3b4e87 3b4e623b4e553b621a 3b6209 128.123.234.033 128.123.234.188128.229.244.006 128.229.244.109 128.123.234.063 To: 3b4e55 From: 3b4e87 To: 128.229.244.006 From: 128.123.234.033 Network Layer data

11. Slide 15-11 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Addressing & Routing Host X Host R Host Y Network CNetwork A 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 3b4e87 3b4e623b4e553b621a 3b6209 128.123.234.033 128.123.234.188128.229.244.006 128.229.244.109 128.123.234.063 Host S Network B

12. Slide 15-12 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Addressing & Routing Host X Host R Host Y Network CNetwork A 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 3b4e87 3b4e623b4e553b621a 3b6209 128.123.234.033 128.123.234.188128.229.244.006 128.229.244.109 128.123.234.063 To: 3b621a From:... To: 128.229.244.006 From: 128.123.234.033 Network Layer data Network B

13. Slide 15-13 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 ISO OSI Model Transport Network Data Link Physical Transport Network Data Link Physical Physical/Data Link layer networks: Ethernet, Token Ring, ATM Network layer net: The Internet Transport layer net: TCP-based network Examples

14. Slide 15-14 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 ISO OSI & TCP/IP MAC ISO OSI Network ISO OSI TLI ISO OSI Session ISO OSI packet ISO OSI frame Ethernet ARPAnet IP ARPAnet TCP ISO OSI Session ISO OSI packet IP frame Ethernet packet

15. Slide 15-15 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 First-Level Domain.edu.colorado.cs anchor pawnee neon.edu Domain.colorado Domain.cs Domain Supports TCP Uses UDP Domain Name Server (DNS)

16. Slide 15-16 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Sharing Names (5623, 56, 2046) (3456, 77, 6785) (9876, 88, 3434) (31978, 12, 1234) Port 1234 Process A on Host #12 on Net #31978 Bind The OS on Host #12 on Net #31978 send(…,(31978, 12, 1234), …); Process B Process A Transport Layer Global Address Space 0x001a4772

17. Slide 15-17 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 Internet and Protocols Internetworking = Internet Protocol Model ■ ■ ■ FTP TCP UDP IP NET 1 2 n HTTPNVTFTP Data Link Physical Network Transport Session

18. Slide 15-18 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 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

19. Slide 15-19 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 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

20. Slide 15-20 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 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

21. Slide 15-21 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 TCP: Connection-Oriented  Definitions -- Connection-Oriented Connection-oriented service is modeled after the telephone system Pick up & dial the number Talk Hang up

22. Slide 15-22 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 ISO OSI Model Presentation Session Transport Network Data Link Physical Presentation Session Transport Network Data Link Physical 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 Examples

23. Slide 15-23 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 ISO OSI Model Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical 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 Examples

24. Slide 15-24 Copyright © 2004 Pearson Education, Inc. Operating Systems: A Modern Perspective, Chapter 15 A Firewall Organization’s Intranet Firewall Internal Host Internet