In the TMN model, specific interfaces between two TMN components communicate with one another. The TMN interfaces are as follows:

TMN Interfaces	Description
Q	The Q interface exists between two TMN–conformant functional blocks that are within the same TMN domain. The Qx carries information that is shared between the MD and the NEs that it supports. The Qx interface exists between the NE and MD; QA and MD; and MD and MD. The Q3 interface is the OS= interface. Any functional component that interfaces directly to the OS uses the Q3 interface. In other words, the Q3 interface is between the NE and OS; QA and OS; MD and OS; and OS and OS
F	The F interface exists between a WS and OS, and between a WS and MD
X	The X interface exists between two TMN–conformant OSs in two separate domains, or between a TMN–conformant OS and another OS in a non–TMN network.

Table 2. TMN Interfaces

Two other reference points, g and m, are outside the scope of TMN. They are between non–TMN entities and the non–TMN portion of the WSF and QAF, respectively.

In Figure 3, each line represents an interface between two TMN components.

Figure 3. Standard Interfaces Between TMN Components

More About the Q Interfaces

There are two classes of Q interfaces: Q3 and Qx. Figure 4 illustrates which function blocks can communicate via which Q interface.

Figure 4. Q Interfaces

Q3 Interface

The Q3 interface is the lifeline to the operations system—Q3 is the only interface that QAs, MDs, or NEs may use to communicate directly with the OS. If a QA or NE does not use the Q3 interface, it cannot communicate directly with the OS; instead, it must communicate via an MD.

Qx Interface

The Qx interface always operates with a MD. It never takes the place of a Q3 interface. The MD can interpret between local management information provided by a Qx interface and the OS information provided by a Q3 interface.