Control Protocol (SACP)

Control Protocol (SACP) is a message based protocol with priority control. It resides at the Application Layer of the Network Model. The priority logic underlies the Channel. Each Channel has own Data Classifier.

Message structure

Part	Field name	Length (bits)	Description
Header	Channel	2	Channel ID (Priority)
	Data Classifier	6	Data Classifier ID
	SARP	16	SARP Header part
	ACK	1	Acknowledgment flag
	TTL	4	Time to live
	Data length	11	Length of Data in bytes
Payload	Data	0-14336	Maximum is 1792 bytes

Channel (2 bits)

This is a Channel ID that specifies the priority of this Message. The smaller ID is, greater priority has the Message. For the whole channels list please check the Channel Data Classifier.

Data Classifier (6 bits)

Check the Channel Data Classifier.

SARP (16 bits)

This is an address information that contains Source and Destination IDs for Routing Protocol (SARP).

ACK (1 bit)

This is an Acknowledgment flag. If ACK=1 then this Message should be confirmed by recipient about reception.

TTL (4 bit)

Time to live (TTL) is a lifetime in seconds of Message in Network. The maximum value is 15 seconds. When TTL is up the MessageLostException will be raised.

Data length (11 bits)

This is a length of Payload part in bytes. The Message can be empty (without Payload). In this situation when Data length=0x0 Payload part is not presented in the Message.

Data (0-14336 bits)

The maximum size of Payload part is 1792 bytes.

Note

This limitation was caused by maximum numbers of Segments from Transport Protocol (SATP). 256 segments * 7 bytes of user data = 1792 bytes