IEEE 802.3-1990 pdf free.Information processing systems — Local area networks Carrier sense multiple access withcollision detection (CSMA/CD) access method and physical layer specifications.
IEEE 802.3 diagrams contain the authoritative statement of the functions theydepict; when apparent conflicts between descriptive text and state diagramsarise, the state diagrams are to take precedence. This does not override, how-ever, any explicit description in the text that has no parallel in the state dia-grams.
The models presented by state diagrams are intended as the primary speci-fications of the functions to be provided. It is important to distinguish, however, between a model and a real implementation. The models are optimizedfor simplicity and clarity of presentation,while any realistic implementationmay place heavier emphasis on efficiency and suitability to a particular implementation technology. It is the functional behavior of any unit that mustmatch the standard,not its internal structure. The internal details of themodel are useful only to the extent that they specify the external behaviorclearly and precisely.
Service Specification Method and Notation. The service of a layer orsublayer is the set of capabilities that it offers to a user in the next higher(sub)layer. Abstract services are specified here by describing the serviceprimitives and parameters that characterize each service. This definition ofservice is independent of any particular implementation (see Fig 1-3).
Specific implementations may also include provisions for interface inter-actions that have no direct end-to-end effects. Examples of such local interactions include interface flow control，status requests and indications，errornotifications，and layer management. Specific implementation details areomitted from this service specification both because they will differ from implementation to implementation and because they do not impact the peer-to-peer protocols.
Classification of Service Primitives. Primitives are of two generictypes:
(1)REQUEST. The request primitive is passed from layer N to layer N-1 torequest that a service be initiated.
(2) INDICATION. The indication primitive is passed from layer N-1 tolayer N to indicate an internal layer N-1 event that is significant to layer N.This event may be logically related to a remote service request,or may becaused by an event internal to layer N-1.IEEE 802.3 pdf download.