scope:

For the purpose of compatible interconnection of data processing equipment using the IEEE 802 MAC Service supported by interconnected IEEE 802 LANs (see 3.4) using different or identical Media Access Control methods, this standard specifies a general method for the operation of MAC Bridges. To this end it

a) Positions the bridging function within an architectural description of the MAC Sublayer.

b) Defines the principles of operation of the MAC Bridge in terms of the support and preservation of the MAC Service, and the maintenance of Quality of Service.

c) Specifies the MAC Internal Sublayer Service provided by individual LANs to the Media Access Method Independent Functions that provide frame relay in the Bridge.

d) Identifies the functions to be performed by Bridges, and provides an architectural model of the internal operation of a Bridge in terms of Processes and Entities that provide those functions.

e) Establishes the requirements for a protocol between the Bridges in a Bridged LAN to configure the network, and specifies the distributed computation of a Spanning Tree active topology.

f) Specifies the encoding of the Bridge Protocol Data Units (BPDUs).

g) Establishes the requirements for Bridge Management in the Bridged LAN, identifying the managed objects and defining the management operations.

h) Establishes the requirements for a protocol between Bridges in a Bridged LAN to configure multicast filtering information, and specifies the means of registering and distributing multicast filtering information by means of the GARP Multicast Registration Protocol (GMRP).

i) Specifies the encoding of GMRP protocol data units.

j) Specifies performance requirements and recommends default values and applicable ranges for the operational parameters of a Bridge.

k) Specifies the requirements to be satisfied by equipment claiming conformance to this standard.

l) Specifies criteria for the use of MAC-specific bridging methods.

m) Specifies enhancements to the operation of Spanning Tree protocol, and to the other mechanisms that support reconfiguration of the physical and filtering connectivity, in order to allow support for rapid reconfiguration of Bridged LAN connectivity.

This standard specifies the operation of MAC Bridges that attach directly to IEEE 802 LANs, as specified in the relevant MAC standards for the MAC technology or technologies implemented.

The configuration protocol and associated algorithm required for the distributed computation of a Spanning Tree active topology referred to in item e) appears in two forms in this standard. Clause 8 specifies a version of the Spanning Tree algorithm and protocol that is consistent with the specification contained in IEEE Std 802.1D, 1998 Edition; Clause 17 specifies the Rapid Spanning Tree Algorithm and Protocol; this version offers a significant reduction in the time taken to reconfigure the active topology of the Bridged LAN in the face of changes to the physical topology or its configuration parameters. The two versions of the algorithm and protocol are capable of interoperating within the same Bridged LAN; hence, it is not necessary for implementations to support both versions of the Spanning Tree algorithm and protocol.

In view of the improved performance offered, it is recommended that the Rapid Spanning Tree algorithm and Protocol is supported in preference to the original version in new MAC Bridge implementations.

NOTE 1-The original version of the Spanning Tree algorithm and protocol has been retained in this standard to allow implementations that pre-date the availability of the Rapid Spanning Tree Algorithm and Protocol to continue to claim conformance to IEEE Std 802.1D.

The specification of Remote Bridges, which interconnect LANs using Wide Area Network (WAN) media for the transmission of frames between Bridges, is outside the scope of this standard.

NOTE 2-Remote MAC Bridging is specified in ANSI/IEEE Std 802.1G, 1998 Edition (ISO/IEC 15802-5:1998) [B1]².

²The numbers in brackets preceded by the letter B correspond to those of the bibliography in Annex G.