IEEE 802:2001 pdf free download

IEEE 802:2001 pdf free download.IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture.
6.2.1 Service access points (SAPs)
Multiple-link service access points ([SAPs) provide interface ports to support multiple higher layer users above the LLC sublayer.
The MAC sublayer provides a single MAC service access point (MSAP) as an interface port to the LLC sublayer in an end station. In general. the MSAP is identified (for transmission and reception) by a single individual MAC address and (for reception by the LAN-wide broadcast MAC address; it can also be identified (for reception) by one or more group MAC addresses. Clause 9 provides details of how these MAC addresses are constructed and used: see also ISO/IEC 15802-I.
A user of LLC is identified by. at a minimum, the logical concatenation of the MAC address field and the LLC address field in a frame. See ISO/IEC 8&)2-2 and ISO/IEC TR 11802-I far a description of LLC addresses.
The Physical layer provides an interface port to a single MAC station, and in the case of ISLANs and
MANS. ii may optionally offer isochronous bearer services at multiple Physical service access points
(PhSAPs). See 11.3 for a more detailed description of ISLAN and MAN PhSAP addressing requirements.
6.2.2 LLC sublayer
The LLC sublayer standard. lSO/IEC 8802-2, describes three types of operation for data communication between service access points: unacknowledged connectionless-mode (type I), connection-mode (type 2), and acknowledged connectionless-rnode (type 3).
With type I operation, information frames are exchanged between LLC entities without the need for the prior establishment of a logical link between peers. The LLC sublayer does not provide any acknowledgments for these LLC frames, nor does it provide any flow control or error recovery procedures.
LLC type I also provides a TEST function and an Exchange Identification (XID) function. The capability to act as responder for each of these functions is mandatory: This allows a station that chooses to support initiation of these functions to check the functioning of the communication path between itself and any other station, to discover the existence of other stations, and to find out the LLC capabilities of other stations.
With type 2 operation, a logical link is established between pairs of LLC entities prior to any exchange of information frames. In the data transfer phase of operation, information frames are transmitted and delivered in sequence. Error recovery and flow control are provided, within the LLC sublayer.
type 3 operation, information frames are exchanged between LLC entities without the need for (he prior establishment of a logical link between peers. However, the frames are acknowledged to allow error recovery and proper ordering. Further. type 3 operation allows one station to po11 another for data.
NOTE—ISOIIEC 8802-2 defines tour classcs of LLC. each ol which groups together support for a different combination of LLC ypes. All classes include mandatory support of type I.