TCP IP DOD Layer Model


Explaining Transmission Control Protocol/Internet Protocol.

TCP/IP is a protocol suite, designed to be independent from hardware and to communicate in the greatest number of environments, globally. This protocol suite allows the interaction between operating systems and different platforms, like data exchange and the sharing of resources across networks, and the decentralization of network communications through equal shares, and equal priority, between nodes.

Though it’s based on the four layer reference model typical of the DoD model that it originated from, with protocols located into those four layers- application layer, transport layer, Internet layer, and link layer, TCP/IP protocols operate similarly to OSI (Open System Interconnection), with passage of data from top layer, closer to the user, to the bottom layer.

TCP/IP layers:

• Application layer: This layer possesses used by applications to process user services or for data application exchange over network connections, but data is processed to pass to the Transport Layer.

Its functions are sometimes compared to the Application (seventh), Presentation (sixth), and Session (fifth) layers of the OSI model. Protocols like HTTP ( HyperText Transfer Protocol, web browsing), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol, e-mails) are applied at this layer.

TCP IP Model

• Transport layer: It creates a channel for data exchange, used by applications. Two main protocols are found there, TCP and UDP. Transmission Control Protocol (TCP) provides connection oriented communication, and it controls the flow of data, allowing data fragments to be sent in any order and be reassembled on reception.

To do this, it creates a bidirectional connection with the other end, after the virtual circuit set up, and both end coordinate to guarantee reliability of data transfer. User Datagram Protocol (UDP) is a connection-less protocol that doesn’t guarantee the same reliability of transmission, or reception, of data segments, that TCP does. But due to no tracking mechanism to guarantee delivery, it’s a faster protocol for transmission, and it’s used for DNS lookups and TFTP transfers.

• Internet layer: This layer is provided the transport of datagrams between networks, and the sending of incoming ones to the transport layer when it’s necessary. Data passes from the Transport Layer ends in this layer, where IP (Internet Protocol), ICMP (Internet Control Message Protocol), and ARP (Address Resolution Protocol) are located. IP performs routing and logistical addressing, ICMP is an error and status-report protocol and provides information about status, and ARP converts logistical addresses to the physical addresses.

• Link layer: The layer farthest from the end user, compared to the physical layer and the data link layer of the OCS model. Its protocols operate only on a link the host is physically connected to. It specifies hardware requirements for data transmission, checks data integrity through FCS (Frame Check Sequence), receives and transports data between physical networks hardware.

Functions included in this processes are addiction of a packed header, preparation for transmission, and those are controlled in the software device driver for the network card, and on firmware or specialized chipsets.

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