The SCTP layer provides transport functionality for higher protocol layers over IP. It is responsible for the reliable transfer of M3UA and higher level SS7 messages between two IP endpoints.
SCTP consists of messages that govern communications between SCTP functions and the lower layers on the TX board. The messages perform the following tasks:
The binding phase establishes the higher layer application (M3UA) as the user of the SCTP interface, an SCT SAP. M3UA sends a single bind request message to SCTP, for which there is a bind confirmation response. Similarly, SCTP binds with its lower layer (IP) through a transport SAP (TSAP). This binding is performed automatically by the SCTP and M3UA layers at startup.
The application establishes an SCTP association when directed to by M3UA. It initiates a four message handshake with the peer endpoint. When completed successfully, SCTP sends a connection up indication to M3UA.
After the SCTP layer returns a connection up message to M3UA, M3UA initiates the sending of ASPUP (ASP UP) and ASPAC (ASP Active) messages to allow the transfer of higher level messages.
M3UA sends a data request message to SCTP to request transmission of an SS7 packet on a particular association. When the message is acknowledged by the far exchange, there is no corresponding notification sent to the application.
SCTP sends a data indication message to notify M3UA of an incoming data packet.
In addition to general parameters, the SCTP layer consists of the following configurable entities:
An SCT service access point (SCT SAP) defines the interface between SCTP and M3UA. It is the upper SAP for SCTP and the lower SAP for M3UA. Only one SCT SAP is defined for an SCTP layer.
The SCTP API lets you perform the following actions on the SCT SAP:
Initialize configuration parameters
Configure the SCT SAP for SCTP
Obtain configuration information
Obtain status information
Obtain statistical information
For more information, see SCTP management function summary.
A transport service access point (TSAP) defines the interface between SCTP and the IP/Ethernet layer. It is the lower SAP for SCTP. Only one TSAP is defined for an SCTP layer.
The following illustration shows the SCT SAP and TSAP defined for SCTP:
The SCTP API lets you perform the following actions on the TSAP:
Initialize configuration parameters
Configure the TSAP for SCTP
Obtain configuration information
Obtain status information
Obtain statistical information
For more information, see SCTP management function summary.