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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 recieves 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 higer layer PDU"
encapsulation
The placement of data from a higher-layer protocaol behind the header (and sometimes between trailer) of the next lower layer protocol.
frame
"a term refering 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 informatino that includes the network layer header and encapsulated data, but no headers or trailers below thenetwork layer."
Protocol data unit (pdu)
"an OSI term to refer generically to a grouping of information by a particular layer of the OSI model. More specifically, an LxPDU would imply the data and headers as defined by Layer x."
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 header and encapsulated data, with the reciving devices 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."
OSI Layers
"(1 - 7 ) Physical, Data-link, Network, transport, session, presentation, application"
Function of OSI Layer 1
"(Physical Layer) Defines the electrical, optical, cabling, connectors, and procedural details required for transmitting bits, represented as some form of energy passing over a physical medium."
Function of OSI Layer 2
(Data-Link Layer) Formats data into frames appropriate for transmission onto some physical medium. Defines rules for when the medium can be used. Defines means by which to recognize transmission errors.
Function of OSI Layer 3
"(Network Layer) Logical addressing, routing, and path determiniation."
Function of OSI Layer 4
"(Transport Layer) Provides a variety of services between two host computers, including connection establishment and termination, flow control, error recovery, and segmentation of large data blocks into smaller parts for transmission."
Function of OSI Layer 5
(Session Layer) Establishes and maintains end-to-end bidirectional flows between endpoints. Includes managing transaction flows.
Function of OSI Layer 6
(Presentation Layer) Defines the format and organization of data. Includes encryption
Function of OSI Layer 7
(Application Layer) Interfaces between network and application software. Also includes authentication services.
OSI - TCP/IP Comparison.
"TCP/IP Application Layer maps to OSI Layers 5,6,7. TCP/IP Transport Layer maps to OSI Layer 4. TCP/IP Internet Layer maps to OSI Layer 3. TCP/IP Network Access Layer Maps to OSI Layers 1,2"
Benefits of using a layerd networking model
"Less Complex ( breaks concepts into smaller parts.) Standard Interfaces, easier to learn, easier to develop, multivendor interoperability (by making products that user same standard), modular engineering (vendors can write programs that implements different layers. don't have to remake the wheel)"
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