DOD TCP/IP Model

 DOD TCP/IP Model:

Layers	OSI Model		Protocols (Port or protocol numbers)		Definition
Process	Application Presentation Session		Telnet (23) FTP (21) TFTP (69) SMTP (25) SNMP (161) DNS (53) BootP NFS DHCP HTTP (80)		Telephone Network - terminal emulation File Transfer Protocol – file transfer that also allows authentication, directory browsing Trivial File Transfer Protocol – stripped down FTP used to backup and restore routers’ config Simple Mail Transfer Protocol – used to send email. POP3 (110) and IMAP (143) retrieve mail Simple Network Management Protocol – collects valuable network info by polling devices (UDP) Domain Name Service – resolves domain names into IP addresses Bootstrap Protocol – used in diskless stations that receive network info and OS from the server Network File System – allows different file system to interoperate. Uses UDP. Dynamic Host Configuration Protocol – enhanced from BootP, can provide IP, subnet, domain, gateway, DNS and WINS information. Uses UDP. Hyper Text Transfer Protocol – WWW protcol
Host-to-Host	Transport		TCP (6) UDP (17) NBP		Transmission Control Protocol – connection-oriented protocol using windowing as flow-control mechanism. Segments are numbered and the number of the last segment received is sent back in the acknowledge message. User Datagram Protocol – unreliable connection-less protocol that has less overhead than TCP. Port numbers: used by TCP and UDP. Numbers 0-1023 are well-known port numbers. Numbers 1024 to 65534 can be used by a transmitting host to initiate the communication. Name Binding Protocol – AppleTalk protocol that matches logical device names to address.
Internet	Network		IP ICMP (1) ARP RARP Routing		Internet Protocol – four-byte number used to route packets on the internet. Connectionless Protocol Internet Control Message Protocol – management protocol and message svc provider for IP. Used in “destination unreachable”, “buffer full”, “hop limit” messages, and in ping and trace. Implemented by all TCP/IP hosts. Address Resolution Protocol – retrieves a MAC address from an IP address Reverse Address Resolution Protocol – retrieves an IP address from a MAC address All routing protocols operate at this layer
Network Access		Data-Link Physical		Ethernet, FastEthernet, Token-Ring, FDDI