===== Open Systems Interconnection (OSI) Model =====
[[dido:public:ra:xapend:xapend.a_glossary:start| Return to Glossary ]]


The **Open Systems Interconnection (OSI) Model** is a conceptual and logical layout that defines network communication used by systems open to interconnection and communication with other systems.

The model is broken into seven subcomponents, or layers, each of which represents a conceptual collection of services provided to the layers above and below it. The **OSI Model** also defines a logical network and effectively describes computer packet transfer by using different layer protocols.

The **OSI Model** may also be referred to as the seven-layer **OSI Model** or the seven-layer model.

<figure ocsilayer>
{{  :dido:public:ra:xapend:xapend.a_glossary:o:screen_shot_2022-01-17_at_7.35.48_pm.png?200  |}}
<caption>The Seven Layers of the OSI Model.</caption>
</figure>

The Seven Layers are:

^   Layer   ^   Name             ^  Examples  |
^  7        | [[dido:public:ra:xapend:xapend.a_glossary:a:applayer]]       | <WRAP>
[[dido:public:ra:xapend:xapend.a_glossary:s:snmp]], 
[[dido:public:ra:xapend:xapend.a_glossary:h:http]], 
[[dido:public:ra:xapend:xapend.a_glossary:f:ftp]]
</WRAP>|
^  6        | [[dido:public:ra:xapend:xapend.a_glossary:p:presentlayer]]   | [[dido:public:ra:xapend:xapend.a_glossary:e:encryption]], [[dido:public:ra:xapend:xapend.a_glossary:a:ascii]], [[dido:public:ra:xapend:xapend.a_glossary:p:png]], [[dido:public:ra:xapend:xapend.a_glossary:m:midi]] | 
^  5        | [[dido:public:ra:xapend:xapend.a_glossary:d:datalinklayer]]  | Syn/Ack | 
^  4        | [[dido:public:ra:xapend:xapend.a_glossary:n:netlayer]]       | [[dido:public:ra:xapend:xapend.a_glossary:t:tcp]], [[dido:public:ra:xapend:xapend.a_glossary:u:udp]], [[dido:public:ra:xapend:xapend.a_glossary:p:port | Port Numbers]] | 
^  3        | [[dido:public:ra:xapend:xapend.a_glossary:s:sessionlayer]]   | [[dido:public:ra:xapend:xapend.a_glossary:i:ip]], [[dido:public:ra:xapend:xapend.a_glossary:r:router]] |
^  2        | [[dido:public:ra:xapend:xapend.a_glossary:t:transportlayer]] | [[dido:public:ra:xapend:xapend.a_glossary:n:netcabling]], [[dido:public:ra:xapend:xapend.a_glossary:r:rj45]], [[dido:public:ra:xapend:xapend.a_glossary:w:wifi]] |
^  1        | [[dido:public:ra:xapend:xapend.a_glossary:p:physicallayer]]  | [[dido:public:ra:xapend:xapend.a_glossary:m:mac]], [[dido:public:ra:xapend:xapend.a_glossary:s:switch | Switches]] |


Source: [[https://www.techopedia.com/definition/24205/open-systems-interconnection-model-osi-model ]]