Logical Link Control (LLC) is the IEEE 802 data-link sublayer that provides media-independent data-link functions. It uses services from the Media Access Control (MAC) sublayer to provide services to the network layer. In short, LLC describes a logical service role above MAC; it is not the physical medium or the mechanism that controls access to that medium.
Where LLC fits in the network model
The data-link layer sits between the network layer and the physical transmission of data. In the IEEE 802 model described in an ISO/IEC draft technical report hosted by IEEE, the data-link layer is divided into LLC and MAC: LLC sits above MAC and interfaces with the network layer. The report describes ISO/IEC 8802-2 as containing LLC’s service description and protocol elements. Because that report dates from 1999, it is useful for explaining the model, not for establishing present-day implementation practice.
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What LLC does—and how it differs from MAC
An IEEE-hosted glossary defines LLC as “That part of the data link layer that supports media independent data link functions, and uses the services of the medium access control sublayer to provide services to the network layer.” The definition identifies both its role and its dependency: LLC provides data-link functions without being tied to one medium, while relying on MAC’s underlying services.
| Sublayer | Position | Responsibility in the cited model |
|---|---|---|
| LLC | Above MAC, toward the network layer | Provides media-independent data-link functions and uses MAC services to provide services to the network layer. |
| MAC | Below LLC, within the data-link layer | Provides the underlying sublayer services that LLC uses. |
The glossary definition does not describe LLC as the mechanism that controls access to a particular medium. That role should not be inferred from the name “Logical Link Control.”
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Historical LLC operation types
A 2000 IEEE-hosted contribution quoting IEEE 802 architecture describes three LLC operation types. These are historical protocol descriptions, not evidence that all three are choices in use across today’s networks.
- Type 1: unacknowledged connectionless. The described procedure has no acknowledgement, flow control, or error recovery.
- Type 2: connection-oriented. It establishes a logical link before information exchange, then provides in-sequence delivery, error recovery, and flow control during data transfer.
- Type 3: acknowledged connectionless. It uses acknowledgements to support recovery and ordering, and the cited description includes a polling capability.
IEEE 802.2 status and dates
IEEE’s IEEE 802.2 page says Working Group 802.2 developed the LLC standard, the group is officially disbanded, and IEEE 802.2 was withdrawn in 2010. The page says standards should refer to ISO/IEC 8802-2, which it describes as “stabilized” (active but not updated). The page displays a last-update date of 2011-07-25, so this is the status recorded there, not a fresh confirmation of the standard’s status in 2026.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the definition does not establish
The cited material defines LLC and describes its place in the IEEE 802 model, but it does not establish how prevalent particular LLC operation types are in current networks. It also does not identify a specific consumer product as an LLC product. LLC is best understood here as a networking sublayer and standard-defined function, rather than a device or a medium-access method.
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