Signaling point configurations

The MTP 3 layer can be configured as a signal transfer point (STP) or as a signaling endpoint (SP). The primary difference between STP operation and SP operation is the handling of messages received from signaling links by the MTP 3 layer but addressed to other destinations.

When configured as an STP, MTP 3 searches for an outbound route to the message destination, and if found, routes the message over an outbound link. When configured as an SP, the MTP 3 layer discards such messages.

When configured as an STP, the MTP 3 layer also performs the additional signaling route management procedures required of an STP. These procedures involve notifying adjacent SPs when they can no longer route messages to a particular destination through that STP due to failures or congestion (transfer prohibited or restricted), and notifying them again when normal communication with the concerned destination is restored (transfer allowed).