by mortiz


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Adjacent-Layer Interaction
The general topic of how on one computer, two adjacent layers in a networking architectural model work together, with the lower layer providing services to the higher layer.
Decapsulation
On a computer that receives data over a network, the process in which the device interprets the lower-layer headers and, when finished with each header, removes the header, revealing the next-higher-layer PDU.
Encapsulation
The placement of data from a higher-layer protocol behind the header (and in some cases, between a header and a trailer) of the next-lower-layer protocol. For example, an IP packet could be encapsulted in an Ethernet header and trailer before being sent over an Ethernet.
Frame
A term referring to a data-link header and trailer, plus the data encapsulated between the header and trailer.
Networking Model
A generic term referring to any set of protocols and standards collected into a comprehensive grouping that, when followed by the devices in a network, allows all the devices to communicate. Examples include TCP/IP and OSI.
Packet
A logical grouping of information that includes the network layer header and encapsulated data but specifically does not include any headers and trailers below the network layer.
Protocol Data Unit (PDU)
A generic term referring to the header defined by some layer of a networking model, and the data encapsulated by the header (and possibly trailer) of that layer, but specifically not including any lower-layer headers and trailers.
Same-Layer Interaction
The communication between two networking devices for the purposes of the functions defined at a particular layer of a networking model, with that communication happening by using a header defined by that layer of the model. The two devices set values in the header, send the hader and encapsulated data, with the receiving device(s) interpreting the header to decide what action to take.
Segment
In TCP, a term used to describe a TCP header and its encapsulated data (also called an L4PDU). Also in TCP, the process of accepting a large chunk of data from the application layer and breaking it into smaller pieces that fit into TCP segments. In Ethernet, a segment is either a single Ethernet cable or a single collision domain (no matter how many cables are used).
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