IEEE Std 802.1AC pdf free download

IEEE Std 802.1AC pdf free download.Local and metropolitan area networks- Media Access Control (MAC) Service Definition.
7.1 Protocol entities, peers, layers, services, and clients
The fundamental notion of the model is that each protocol entity within a system is instantiated at one of a number of strictly ordered layers, and communicates with peer entities (operating the same or an interoperable protocol within the same layer) in other systems by using the service provided by interoperable protocol entities within the layer immediately below, and thus provides service to protocol entities in the layer above. The implied repetitive stacking of protocol entities is essentially unbounded at the lowest level and is bounded at the highest level by an application supported by peer systems. In descriptions of the model, the relative layer positions of protocol entities and services are conventionally referred to by N, designating a numeric level. The (N)-service is provided by an (N)-entity that uses the (N-1)-service provided by the (N-1)-entity, while the (N)service user is an (N+1)-entity. Figure 7-1 illustrates these concepts with reference to the MAC sublayer, which contains MAC entities that provide the MAC Service to MAC Service users.
7.2 Service interface primitives, parameters, and frames
Each (N)-service is described in terms of service primitives and their parameters, each primitive corresponding to an atomic interaction between the (N)-service user and the (N)-service provider, with each invocation of a primitive by a service user resulting in the service issuing corresponding primitives to peer service users. The purpose of the model is to provide a framework and requirements for the design of protocols while not unnecessarily constraining the internal design of systems; primitives and their parameters are limited to (but include all of) the information elements conveyed to corresponding peer protocol entities or required by other systems (and not supplied by protocols in lower layers) to identify (address) those entities and deliver the information. The parameters of service primitives do not include information that is used only locally, i.e., twithin the same system) e.g.. to identify entities or organize resources for example.7
The primitives of the MAC Service comprise a data request and a corresponding data indication, each with MAC destination address, MAC source address, a MAC Service Data Unit (MSDU) comprising one or more octets of data, and priority parameters. Taken together these parameters are conveniently referred to as a frame, although this does not imply that they are physically encoded by a continuous signal on a communication medium, that no other fields are added or inserted by other protocol entities prior to transmission, or that the priority is always encoded with the other parameters transmitted.
These points are frequently misunderstood by those unfamiliar with the reference model, who take it as simply restating common sense principles of modular engineering. Early variants of the MAC Service, for example, omitted the source MAC address parameter on the grounds that it was a fixed property of the transmitting station and should be supplied by the MAC entity itself, despite the fact that communicating peer service users (and the protocols they operate) required that information. The introduction of MAC Bridges necessitated the development of a MAC ISS with the required parameter and has led to a restatement of the service definition included in a number of standards. However the source address parameter would still have been required even if MAC Bridges did not exist. Similarly, versions of the MAC Service have included local acknowledgment primitives or status return codes for primitives issued. These play no part in defining the peer-to-peer communication and do not conform to the reference model. The scope of some IEEE 802 standards does include the definition of interfaces, particularly electrical interfaces, within systems. These play a valuable role in defining components used to build those systems, but should not be confused with OS! service interfaces.IEEE Std 802.1AC pdf download.