To guarantee the quality of service （QoS） for different data services in metropolitan area network （MAN）

Multiple Services Ring （MSR） technique

a standard issued by ITU-T

provides a solution to QoS problem under ever growth of data services in MAN. This paper discusses the topology

protocol stacks and frame format of MSR. Based on the procedures chart of a MSR node

the emphasis is put on the functional modules of each tributary

and QoS guarantees. Finally

it also addresses the service types and networking application of MSR.