A number of standards bodies define performance monitoring packets that can be sent from a source, processed, and responded to by a reflector. The protocols available to carry out the measurements are based on the test family type configured for the session.
Ethernet PM delay measurements are carried out using the Two Way Delay Measurement Protocol version 1 (DMMv1) defined in Y.1731 by the ITU-T. This allows for the collection of Frame Delay (FD), InterFrame Delay Variation (IFDV), Frame Delay Range (FDR), and Mean Frame Delay (MFD) measurements for round trip, forward, and backward directions.
DMMv1 adds the following to the original DMM definition:
the Flag Field (1 bit – LSB) is defined as the Type (Proactive=1 | On-Demand=0)
the TestID TLV (32 bits) is carried in the Optional TLV portion of the PDU
DMMv1 and DMM are backwards compatible and the interaction is defined in Y.1731 ITU-T-2011 Section 11 "OAM PDU validation and versioning".
Ethernet PM loss measurements are carried out using Synthetic Loss Measurement (SLM), which is defined in Y.1731 by the ITU-T. This allows for the calculation of Frame Loss Ratio (FLR) and availability.
A session can be configured with one or more tests. Depending on the session test type family, one or more test configurations may need to be included in the session to gather both delay and loss performance information. Each test that is configured shares the common session parameters and the common measurement intervals. However, each test can be configured with unique per-test parameters. Using Ethernet as an example, both DMM and SLM would be required to capture both delay and loss performance data.
Each test must be configured with a test ID as part of the test parameters, which uniquely identifies the test within the specific protocol. A test ID must be unique within the same test protocol. Again using Ethernet as an example, DMM and SLM tests within the same session can use the same test ID because they are different protocols. However, if a test ID is applied to a test protocol (like DMM or SLM) in any session, it cannot be used for the same protocol in any other session. When a test ID is carried in the protocol, as it is with DMM and SLM, this value does not have global significance. When a responding entity must index for the purpose of maintaining sequence numbers, as in the case of SLM, the test ID, Source MAC, and Destination MAC are used to maintain the uniqueness of the responder. This means that the test ID has only local, and not global, significance.