LLC Sublayer/MAC Sublayer Interface Service Specification

The following specifies the services required of the Medium Access Control (MAC) sub layer by the Logical Link Control (LLC) sublayer to allow the local LLC sublayer entity to exchange LLC data units with peer LLC sublayer entities. The services are described in an abstract way and do not imply any particular implementation or any exposed interface. The following are the primitives involved:

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• MA_DATA.request

• MA DA T A.indication

• MA DA T A.confirm

The following provide detailed service specification:

MA_DATA.request

Function: This primitive defines the transfer of a MSDU from a local LLC sublayer entity to a single peer LLC entity, or multiple peer LLC entities in the case of group addresses.

Semantics of the Service Primitive: The semantics of the primitive are as follows:

MA_DATA.request (

des tina tion_ address, m_sdu,

requested _ quali ty )

The destination_address parameter must specify either an individual or a group MAC entity address. It must contain sufficient information to create the DA field that is appended to the frame by the local MAC sublayer entity as well as any lower level address information. The m_sdu parameter specifies the MAC service data unit to be transmitted by the MAC sublayer entity, which includes the DSAP, SSAP, C, and information (if present) fields as specified in section 2.4, as well as sufficient lnformation for the MAC sublayer entity to determine the length of the data unit.

The requested_quality parameter specIfies the service class desired for the data unit transfer.

When Generated: This primitive is generated by the LLC sublayer entity whenever a MSDU must be transferred to a peer LLC entity or entities. This can be as a result of a request from higher layers or protocol or from a MSDU generated internally to the LLC sublayer, such as required by Type 2 operation.

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Effect of Receipt: The receipt of this primitive must cause the MAC entity to append all MAC specified fields, including DA, SA, and any fields that are unique to the particular medium access method, and pass the properly formatted frame to the lower layers of protocol for transfer to the peer MAC sublayer entity or entities.

Additional Comments: None.

MA DA T A.indication

Function: This primitive defines the transfer of a MSDU from the MAC sublayer entity to the LLC sublayer entity or entities in the case of group addresses. In the absence of errors, the contents of the m _sdu parameter are logically complete and unchanged relative to the m_sdu parameter in the associated MA_DATA.request.

Semantics of the Service Primitive: The semantics of the primitive are as follows:

MA DA T A.indication (

destination_address, source_address, m_sdu,

reception_status requested_quality )

The destination_address parameter must be either an individual or a group address as specified by the DA field of the incoming frame. The source_address parameter must be an individual address as specified by the SA field of the incoming frame.

The m_sdu parameter specifies the MAC service data unit as received by the local MAC entity. The reception_status par~meter indicates the success or failure of the incoming frame. The requested quality parameter specifies the service class desired for this data unit transfer.

When Generated: The MA_ DA T A.indication is passed from the MAC sublayer entity to the LLC sublayer entity or entities to indicate the arrival of a frame at the local

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MAC sublayer entity. Such frames are reported only if they are validly formatted, received without error, and their destination address designates the local MAC entity.

Effect of Receipt: The effect of receipt of this primitive by the LLC sublayer is unspecified.

Additional Comments: If the local MAC sublayer entity is designated by the destination address parameter of an MA _ DA T A.request, the indication primitive will also be invoked by the MAC entity to the local LLC entity. This full duplex characteristic of the MAC sublayer may be. due to unique functionality within the MAC sublayer or full duplex characteristics of the lower layers, (e.g., all frames transmitted to the broadcast address will invoke MA DA T A.indications at all stations in the network including the station that generated the request).

MA DA T A.confirm

Function: This primitive has local significance and must provide an appropriate reply to the LLC sublayer MA _ DA T A.request primitive signifying the success or failure of the request.

Semantics of the Service Primitive: The semantics of this primitive are as follows:

MA DATA.confirm (

transmission status provided_quality

The transmission_status parameter is used to pass status information back to the local requesting LLC sublayer entity. It is used to indicate the success or failure of the previous associated MA_ DA T A.request. The types of failures that can be associated with this primitive depend on the particular implementation as well as the type of Medium. Access Control sublayer that is used, (e.g., excessive collisions may be a failure returned by a CSMA/CD MAC sublayer entity). The provided _

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ity parameter specifies the service class that was provided for the data unit transfer.

When Generated: This primitive is generated in reply to an MA_DATA.request from the local LLC sublayer entity.

Effect of Receipt: The effect of receipt of this· primitive by the LLC sublayer is unspecIfied.

Additional Comments: It is assumed that sufficient information is available to the LLC sub layer to associate the confirm with the appropriate request.

2.3 LLC SUBLAYER/LLC SUBLAYER MANAGEMENT FUNCTION INTERFACE