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CThe OSI Model of the EIB Communication Stack
 
 
  The figure shows how the EIB communication stack (for typical devices) is structured according to the OSI 7-layer model. This is also reflected in the frame structure shown in the table. The physical layer and link layer obviously depend on the characteristics of the physical medium. For medium access control, EIB prescribes optimised Carrier Sense Multiple Access (CSMA). As explained above, the precise mechanism may be highly optimised for the particular medium. The Destination Address Flag (DAF) simply distinguishes between Group and Device Oriented telegrams.



double indirection of Shared Variable (SV) "Group" Addressing in the EIB communication stack


  When receiving a message, the node's Link Layer checks the destination address to find out whether or not the device has to process the message any further.

Through the Network Protocol Control Information (NPCI), Network Layer controls the hop count; for devices other than routers or bridges, it is trivial.

Transport Layer manages logical communication relationships, which can be:

  1. one-to-many connectionless ("group" multicast)
  2. one-to-all connectionless (broadcast)
  3. one-to-one connectionless
  4. one-to-one connection-oriented

It provides the mapping between addresses and an abstract internal representation, the Communication_Reference_ID (cr_id).All services are mapped transparently across Session and Presentation Layer, which are reserved.

Application Layer implements the API for client/server management of EIB networks (see below). In the case of Group Addressing, Application Layer deals with the assignment of a group cr_id to a local instance of a Group Communication Object (or shared variable), for receiving (one-to-n) and for sending (one-to-one).