1. 1 TCP/IP Internetting

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4. 4 ä Subnet layer ä Links stations on same subnet ä Often IEEE LAN standards ä PPP for telephone connections ä TCP/IP specifies almost any subnet standard ä For LANs, etc., specifies OSI ä OSI further subdivides into Physical, Data Link Application Transport Internet Subnet Data Link Physical TCP/IPOSI

5. 5 TCP/IP Internetting ä Internet layer: ä Links stations across internets ä Main standard is the Internet Protocol (IP) ä Dominant protocol for routers Application Transport Internet Subnet

6. 6 TCP/IP Internetting ä Transport layer: ä Links computers, even if different platforms ä Main standards are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) ä Application layer: ä Links application programs even if from different vendors ä Many standards, because many applications ä SMTP for e-mail; HTTP for the WWW, etc. Application Transport Internet Subnet

7. 7 Universal Addressing ä Each host has a unique IP Number ä 32-bit binary number ä Goes in the IP header’s source and destination fields ä 10000000101010110001000100001101 ä Impossible to remember DestinationSource IP Packet 4 Bytes

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10. 10 Subnet Mask ä Problem: IP numbers do not include subnetting ä Solution: Create a second number: a Subnet Mask ä Define which bits of the IP address refer to subnets vs. hosts on subnet ä Subnet mask is 32 bits long, in dot quad format ä See the class meeting on Windows TCP/IP for basic IP and Subnet Mask concepts. Windows TCP/IP Windows TCP/IP

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13. 13 Routers ä Routers also get IP addresses ä So packets can be sent to them for routing ä Has network ID of the network on which it sits ä Must be assigned a host ID ä Example: 128.171.17.1 Default Router IP Packet for Delivery Another Router 128.171.17.1 128.171.17.104

14. 14 Routers ä Subnets can have Multiple Routers ä There is usually a default router for packet delivery ä Default router is used if no router is specified ä Routers are sometimes called gateways in TCP/IP Default Router IP Packet for Delivery Other Router

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16. 16 Routing Protocols There are no “master” routers. Each router works independently to do routing. This requires each router to build a “routing table” that contains information about the locations of other routers. There are no “master” routers. Each router works independently to do routing. This requires each router to build a “routing table” that contains information about the locations of other routers. Routing Table Routing Table

17. 17 Routing Protocols Routing protocols allow routers to exchange information in their routing tables. Routing protocols allow routers to exchange information in their routing tables. Routing Table Routing Table

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19. 19 Peer Control Among Routers ä Routers Communicate Among Themselves ä To coordinate their actions without central control ä Share knowledge of network connectivity ä Common standards are RIP, OSPF, BGP Router Coordination Message

20. 20 Routing Protocols ä RIP - Router Information Protocol Router Information Protocol Router Information Protocol ä High overhead, but simple and OK for small networks ä OSPF - Open Shortest Path First Open Shortest Path First Open Shortest Path First ä Optimizes routing, but complex ä BGP - Border Gateway (Router) Protocol Border Gateway (Router) Protocol Border Gateway (Router) Protocol ä Used in Internet Backbone Routers Internet BackboneInternet Backbone ä Read Cisco routers for an overview Cisco routersCisco routers

21. 21 Autonomous Systems Autonomous Router Border Router RIP or OSPF RIP or OSPF BPG Border Router Organization can select any routing protocol to synchronize its autonomous (internal) routers. RIP and OSPF are common. Border routers that link autonomous systems normally use BPG. Autonomous System

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23. 23 Error Handling ä TCP/IP a comprehensive set of error handling processes ä The Internet Control Message Protocol (ICMP) is used to send error messages. ä Hosts, Routers send ICMP messages to one another if a problem occurs ä “Host not found” is a common ICMP error message. Host Router ICMP Error Message

24. 24 Internet Control Message Protocol (ICMP) The Internet Control Message Protocol (ICMP) is for delivering supervisory messages among hosts and routers The Internet Control Message Protocol (ICMP) is for delivering supervisory messages among hosts and routers

25. 25 Internet Control Message Protocol (ICMP) “Host Unreachable” Error Messages

26. 26 Internet Control Message Protocol (ICMP) Source Quench Flow Control “Source Quench” tells host to reduce transmission rate. Flow Control “Source Quench” tells host to reduce transmission rate.

27. 27 Internet Control Message Protocol (ICMP) “Echo Request” “Echo Response” Source host can ask questions of destination hosts. “Echo Request” asks if the other host is reachable. Destination host sends back “Echo Response.” Ping Ping Usually implemented with “Ping”Ping program. Source host can ask questions of destination hosts. “Echo Request” asks if the other host is reachable. Destination host sends back “Echo Response.” Ping Ping Usually implemented with “Ping”Ping program.

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29. 29 Autoconfiguration ä Autoconfiguration Server has a bank of addresses ä When a PC “logs in,” it gets a temporary IP number. ä Popular standards are DHCP (in Windows NT) and RARP ä Large stations receive permanent addresses DHCP Request for Address DHCP Response: Your Temporary Address is 127.171.17.35 DHCP Server

30. 30 Autoconfiguration Protocol Source Host Auto- Configuration Host Source host sends Autoconfigutation Request Message to the autoconfiguration host “My 48-bit MAC subnet address is X. Please give me a 32-bit IP host address.” Autoconfiguration Request Message

31. 31 Autoconfiguration Protocol Source Host Auto- Configuration Host Autoconfiguration host sends back a Autoconfiguration response message. “Computer at MAC Address X, your 32-bit IP host number is ‘110100…’.” Autoconfiguration Response Message

32. 32 Autoconfiguration Protocols ä RARP: Reverse Address Resolution Protocol ä Older autoconfiguration protocol ä Bootp ä Another older protocol ä DHCP ä Dynamic Host Configuration Protocol ä Built into Windows NT Server

33. 33 Domain Name Service ä Hosts also have IP host names ä Voyager.cba.hawaii.edu ä Like nicknames ä IP packets require formal IP numbers to put in their source and destination fields ä If tell your software the IP host name, it must look up the IP number

34. 34 Domain Name Service ä Program knowing a host name sends request to Domain Name Service (DNS) Server; receives IP Number DNS Request for Voyager.cba.hawaii.edu DNS Response: 128.171.17.13 DNS Server

35. 35 Domain Name System (DNS) Source Host DNS Host DNS Request Message Source host sends DNS Request Message to DNS host. “I need the 32-bit IP host number for the host named voyager.cba.hawaii.edu.” Source host sends DNS Request Message to DNS host. “I need the 32-bit IP host number for the host named voyager.cba.hawaii.edu.”

36. 36 Domain Name System (DNS) Source Host DNS Host DNS Host DNS Response Message DNS host returns a DNS Reply Message. “The 32-bit host number is 128.171.44.53”. DNS host returns a DNS Reply Message. “The 32-bit host number is 128.171.44.53”.

37. 37 Domain Name System (DNS) Source Host DNS Host DNS Host  Each network has a DNS host  May also have a secondary DNS host  Network DNS host may only know the IP names and numbers of local hosts on the network  For other IP names, contacts another DNS host, especially root DNS hosts, which should have extensive information  Each network has a DNS host  May also have a secondary DNS host  Network DNS host may only know the IP names and numbers of local hosts on the network  For other IP names, contacts another DNS host, especially root DNS hosts, which should have extensive information