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CS 313 Introduction to Computer Networking & Telecommunication

CS 313 Introduction to Computer Networking & Telecommunication. (Teach Yourself) The TCP/IP Internet (in 60 minutes). Topics. Introduction Internetwork Layer Transport Layer Application Layer How is a Message Delivered TAKE CS 413 IN FALL 2011. Introduction. The Internet

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CS 313 Introduction to Computer Networking & Telecommunication

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  1. CS 313 Introduction to Computer Networking & Telecommunication (Teach Yourself) The TCP/IP Internet (in 60 minutes) Chi-Cheng Lin, Winona State University

  2. Topics • Introduction • Internetwork Layer • Transport Layer • Application Layer • How is a Message Delivered • TAKE CS 413 IN FALL 2011

  3. Introduction • The Internet • Internetworking using the TCP/IP protocol suite • internet = internetworking • ARPANET, 1960 • Packet-switching • Point-to-point • Expanded to become the backbone of the Internet

  4. Introduction The Internet is an interconnected collection of many networks.

  5. Internet Network Layer Design Principles • Make sure it works • Keep it simple • Make clear choices • Exploit modularity • Expect heterogeneity . . .

  6. Internet Network Layer Design Principles . . . • Avoid static options and parameters • Look for good design (not perfect) • Strict sending, tolerant receiving • Think about scalability • Consider performance and cost

  7. Internetwork Layer Protocols • ARP (Address Resolution Protocol) • IP (Internet Protocol) • ICMP (Internet Control Message Protocol) • For a router to report datagram problem back to source • IGMP (Internet Group Management Protocol) • Multicasting

  8. ARP • Physical address is needed to deliver a message to the destination • ARP: Given an IP address of a computer, find its physical address • Q: How does source ask destination without knowing destination address? • A: Broadcasting ARP request • Q: How does destination answer? Broadcasting back? A: _______ • ARP only works on the same network • Q: How can a message be delivered to a destination on another network • A: Router answers ARP request! • Q: How can ARP’s performance be improved (i.e., to reduce the broadcasting traffic)? • A: one of our favorite mechanisms in CS  _________ • Q: What if a host reconfigured? • A: Gratuitous ARP

  9. Note that a router has more than one IP addresses! Two switched Ethernet LANs joined by a router

  10. IP • Transmission mechanism used by the TCP/IP • Unreliable, connectionless datagram protocol • Best-effort service • Reliability? • Provided by upper layers (e.g., TCP or …)

  11. The IP Version 4 Protocol The IPv4 (Internet Protocol) header.

  12. The IP Version 4 Protocol Some of the IP options.

  13. IP Addresses An IP prefix.

  14. Classful IP Addresses IP address formats

  15. IP Addresses • IP address is hierarchical, not flat • Two parts: network and host • Theoretically • How many networks of a particular class is possible? • How many hosts are in a network of a particular class? • Class #Networks #Hosts/Network A 27 224 B 214 216 C 221 28 • Actual numbers might be less, because of …

  16. IP Addresses Special IP addresses

  17. IP Addresses • Dotted decimal format • 32 bits are grouped into 4 bytes • Each byte is represented in decimal • Two adjacent bytes are concatenated using a dot • Example: 10001010 00011000 00101000 00000001 • Dotted decimal format: • Which class is it in? • Network address: • Host address:

  18. Internet Control Protocols The principal ICMP message types.

  19. Transport Layer • Two protocols • UDP (User Datagram Protocol) • Connectionless • TCP (Transmission Control Protocol) • Reliable, connection-oriented stream protocol • IP • Host-to-host • TCP or UDP • Port-to-port (application-to-application, process-to-process)

  20. UDP header

  21. The TCP Segment Header

  22. Application Layer Protocols • Domain Name System (DNS) • Translate name to IP address • Electronic mail • Simple Mail Transfer Protocol (SMTP) • Internet Message Access Protocol (IMAP) • Multipurpose Internet Mail Extensions (MIME) • File Transfer Protocol (FTP) • Hypertext Transfer Protocol (HTTP) • Dynamic Host Configuration Protocol (DHCP) • And many more …

  23. (Not Too) Big Picture* • Scenario: Request to download a document from www.winona.edu • IP address of the host 198.174.76.151 • IP address of the router on the network that the host is on is 198.174.76.254 • IP address of the web site is 199.17.166.97 • IP address of the router on the network that the web site is on is 199.17.166.1 *Internet: The Big Picture (by Russ Haynal): http://navigators.com/internet_architecture.html

  24. Big Picture Protocol Stack Network Configuration 198.174.76.151 198.174.76.254 HTTP TCP IP Internet IEEE 802.3 CSMA/CD Ethernet 199.17.166.97 199.17.166.1

  25. Big Picture • Steps • Name  IP address by DNS (Domain Name System, an application layer protocol and a distributed database) • Port required to specify application: server: 80 for http (199.17.166.97:80) client: obtain a port number • Destination network address used for routing (hierarchical routing) • A connection has to be set up first (TCP or UDP?)

  26. Big Picture • Steps (cont’d) • ARP is used for 198.174.76.151 to find the “physical address” of 199.17.166.97. (What will be returned?) • Data: 198.174.76.151  198.174.76.254  intermediate routers  199.17.166.1 • When data received by 199.17.166.1, ARP is used to find the physical address of destination host 199.17.166.97 • Data: 199.17.166.1  199.17.166.97

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