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  • 1. TCP/IP and DoD Model
  • 2. TCP/IP and the DoD Model  The DoD model is a condensed version of the OSI model.  Instead of 7 layers, the DoD model is composed of four layers  Process/Application layer  Host-to-Host layer  Internet layer  Network Access layer
  • 3. TCP/IP and the DoD Model Application Presentation Session Transport Network Data Link Physical Process/ Application Host-to-Host Internet Network Access
  • 4. TCP/IP and the DoD Model  Process/Application layer  Protocols used to integrate various activities of the upper layers of the OSI model  Defines protocols for nod-to-node application communication  Also controls user-interface specifications  Host-to-Host layer  Performs same functions as OSI Transport layer  Provides end-to-end communication
  • 5. TCP/IP and the DoD Model  Internet layer  Performs same functions as OSI Network layer  Logical (IP) addressing and routing  Network Access layer  Monitors data exchange between the host and the network  Handles hardware addressing  Defines protocols for the physical transmission of data
  • 6. TCP/IP and the DoD Model  Various different network protocols operate at different layers of the DoD model
  • 7. TCP/IP and the DoD Model  Process/Application Layer Protocols  Telnet  Provides terminal emulation  Allows a user on a remote machine to access the resources of another remote machine  File Transfer Protocol (FTP)  Allows for files to be transferred between computers  Also operates as a program: allows users to perform file tasks  Limited to directory and file management; no remote execution
  • 8.  Trivial File Transfer Protocol (TFTP)  A stripped-down, stock version of FTP  No directory browsing abilities  Can only PUT and GET files  Network File System  Protocol to allow systems to share files across a network  Allows different types of files systems to interoperate for file sharing
  • 9.  Simple Mail Transfer Protocol (SMTP)  Protocol for sending e-mail  Uses a queue method for mail deliver  Line Printer Daemon (LDP)  Protocol for printer sharing; print spooling via TCP/IP  X Windows  Protocol for writing cluster and servers apps based on a GUI  Allows a program to run on a computer and have the display on another computer using a server
  • 10.  Simple Network Management Protocol (SNMP)  Collects and manipulates valuable network data  Polls devices on a network for a network station  Used to notify of network events or changes  Domain Name Service  Resolves hostnames to IP addresses  Operates with Fully Qualified Domain Name (FQDN)  Can also append domain suffixes
  • 11.  Dynamic Host Configuration Protocol (DHCP)  Simplifies network address management  Protocol to automatically assign network information to hosts  IP address  Subnet mask  Domain name  Default gateway (routers)  Windows Internet Naming Service (WINS) information
  • 12.  Dynamic Host Configuration Protocol (DHCP)  DHCP Process  1. DHCP client broadcasts a DHCP Discover message looking for a DHCP server.  2. The DHCP server that receives the broadcast will respond to the client with a unicast DHCP Offer message.  3. The client will then broadcast back to the server as DHCP Request asking for an IP address.  4. The server makes the assignment and finalizes with a unicast DHCP Acknowledgement.
  • 13.  Process/Application Layer Protocols  Dynamic Host Configuration Protocol (DHCP)  DHCP Process Client Server Client broadcasts DHCPDiscover Server unicasts DHCPOffer Client broadcasts DHCPRequest Server unicasts DHCPACK
  • 14.  Host-to-Host Layer Protocols  Transmission Control Protocol (TCP)  Full-duplex, connection-oriented, reliable, and accurate protocol  Used to break large blocks of application information into segments  Segments and sequenced and number before transmission  Before transmission, the TCP stack creates a virtual circuit between its stack and the other computers TCP stack  Receipt of transmission is verified with acknowledgements  Reliability comes at a price: overhead
  • 15.  Host-to-Host Layer Protocols  User Datagram Protocol (UDP)  Scaled-down model of TCP; sometimes called thin protocol  Doesn’t offer the features of TCP  Reliability, acknowledgements, etc.  Provides for more traffic with less overhead  No sequencing, no acknowledgements  Some situations benefit from UDP instead of TCP  SNMP  Video data
  • 16.  Host-to-Host Layer Protocols  TCP vs. UDP
  • 17.  Internet Layer Protocols  Internet Protocol (IP)  Is essentially the Internet layer; all other protocols exist to support IP  Has a complete picture view of the network; allows IP to make routing and forwarding decisions  Receives segments from the Host-to-Host layer and fragments these into packers before transmissions
  • 18.  Internet Protocol (IP)  ICMP  Provide hosts with information about network problems  Encapsulated within IP datagrams  Ping, Traceroute, etc.  Address Resolution Protocol (ARP)  Finds the hardware address of a host using the IP address  Broadcasts the local network attempting to find the machine with the IP address
  • 19.  Internet Protocol (IP)  Reverse Address Resolution Protocol (RARP)  Finds the IP address of a host given the hardware address  Very useful for diskless machines  Proxy Address Resolution Protocol (Proxy ARP)  Allows hosts to utilize more than one default gateway  Increases traffic on the network  A better alternative is Cisco’s Hot Standby Router Protocol (HSRP)