The document discusses the TCP/IP and DoD models. It explains that the DoD model has 4 layers instead of the 7 layers in the OSI model. The 4 layers are the Process/Application layer, Host-to-Host layer, Internet layer, and Network Access layer. It then provides details on protocols that operate at each of these layers, such as TCP and UDP at the Host-to-Host layer, and IP at the Internet layer.

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)