| 摘要 |
<p>A method of measuring loss in a multicast transmission in a network is described. Service frames including a service multicast destination address are sent from a source node towards a receiving node. A counter of the number of service frames sent is maintained at the source node. This counter is periodically read, and its value copied into a loss measurement OAM frame. The loss measurement OAM frame includes a unique identifier and an OAM destination address which is different to the service multicast destination address, and is sent from the source node towards the receiving node. Every time the sent frames counter is read, a measurement indicator frame is also sent from the source node towards the receiving node. The measurement indicator frame includes the unique identifier so that it can be related to the loss measurement OAM frame. The measurement indicator frame also includes the service multicast destination address, although the measurement indicator frame is distinguishable from the service frames. The receiving node eventually receives the loss measurement OAM frame and the measurement indicator frame, and calculates the number of lost or delayed service frames by comparing the number of service frames received at the receiving node at the time the measurement indicator frame is received with the sent frames counter value contained in the loss measurement OAM frame. The calculation is only performed when the loss measurement OAM frame and measurement indicator frame having the same identifier have been received by the receiving node.</p> |
