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Transcript
CS 313 Introduction to Computer Networking & Telecommunication (Teach Yourself) The TCP/IP Internet (in 60 minutes) Chi-Cheng Lin, Winona State University Topics Introduction Internetwork Layer Transport Layer Application Layer How is a Message Delivered TAKE CS 413 IN FALL 2011 2 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 3 Introduction The Internet is an interconnected collection of many networks. Internet Network Layer Design Principles 1. Make sure it works 2. Keep it simple 3. Make clear choices 4. Exploit modularity 5. Expect heterogeneity ... Internet Network Layer Design Principles ... 6. Avoid static options and parameters 7. Look for good design (not perfect) 8. Strict sending, tolerant receiving 9. Think about scalability 10.Consider performance and cost 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 7 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 8 Note that a router has more than one IP addresses! Two switched Ethernet LANs joined by a router IP Transmission mechanism used by the TCP/IP Unreliable, connectionless datagram protocol Best-effort service Reliability? Provided by upper layers (e.g., TCP or …) 10 The IP Version 4 Protocol The IPv4 (Internet Protocol) header. The IP Version 4 Protocol Some of the IP options. IP Addresses An IP prefix. Classful IP Addresses IP address formats 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 … 15 IP Addresses Special IP addresses 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: 17 Internet Control Protocols The principal ICMP message types. 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) 19 UDP header 20 The TCP Segment Header 21 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 … 22 (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 23 Big Picture Protocol Stack Network Configuration 198.174.76.151 198.174.76.254 HTTP TCP IP IEEE 802.3 CSMA/CD Ethernet Internet 199.17.166.97 199.17.166.1 24 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?) 25 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 26