SS7 NETWORK MANAGEMENT
MTP Level 3 is responsible for initiating signaling network management functions. In a general sense, these functions assist in keeping signaling units moving efficiently across the links to various signaling points in an SS7 network.
Three categories of functions exist within the MTP Level 3 layer:
1. Signaling Link Management
The Signaling Link Management function provided by MTP Level 3 has 3 procedures that operate in conjunction with Initial Alignment Procedures (IAP). When achieving link alignment, MTP Level 2 performs the IAP. Signaling Link Management includes a procedure for taking links out of service (upon notification from MTP Level 2).
The 3 Signaling Link Management procedures with the similar purpose of achieving link alignment are:
- Link Set Activation
- Signaling Link Activation
- Signaling Link Restoration
The procedure for removing a link from service is:
- Signaling Link Deactivation
Note: MTP Level 2 and Initial Alignment Procedures are addressed in the "Link Alignment" section of this module.
On the surface, the differences between the Link Set Activation, Signaling Link Activation, and Signaling Link Restoration procedures are subtle. Each involves bringing a link or set of links into service. The following table describes what each procedure aligns and when it is used. This table provides an overview of basic differences between the procedures.
| Link Set Activation | A set of links that are connected to a signaling point. | - Activating an entire set of new links for the first time.
- Restoring an entire set of links after being taken out of service for either planned or unplanned reasons. |
| Signaling Link Activation | Any single link that is connected to a signaling point. | - Activating a new link for the first time.
- Restoring a link after being taken out of service for planned reasons (e.g., maintenance). |
| Signaling Link Restoration | Any single link that is connected to a signaling point. | - Restoring a link after being taken out of service for unplanned reasons (e.g., failure). |
The Signaling Link Deactivation procedure is used to take links out of service for planned reasons. The procedure has been added to the previous table. The most important aspect at this point is when the procedure is used.
| Link Set Activation | A set of links that are connected to a signaling point. | - Activating an entire set of new links for the first time.
- Restoring an entire set of links after being taken out of service for either planned or unplanned reasons. |
| Signaling Link Activation | Any single link that is connected to a signaling point. | - Activating a new link for the first time.
- Restoring a link after being taken out of service for planned reasons (e.g., maintenance). |
| Signaling Link Restoration | Any single link that is connected to a signaling point. | - Restoring a link after being taken out of service for unplanned reasons (e.g., failure). |
| Signaling Link Deactivation | Remove any single link that is connected to a signaling point from service. | - Too many links are active in a link set. - Maintenance testing is required. |
2. Signaling Route Management
The Signaling Route Management function allows MTP Level 3 to keep signaling points notified of available signaling routes. For example, it may become necessary to re-route messages via another route through a secondary STP if a primary STP is no longer available.
The Signaling Route Management function uses four procedures:
- Transfer Prohibited
- Transfer Restricted
- Transfer Allowed
- Transfer Controlled
Each procedure generates messages (via LSSUs) that are sent out by the signaling point that performs them, keeping other points in the network updated on their status.
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