Signaling Aal; Sscop - 3Com CoreBuilder 7000 Operation Manual

114 C 5: E
HAPTER STABLISHING

Signaling AAL

SSCOP

ATM C
HANNELS
(see "Update Protocol Timer Resolution" on page 212 in the
Management Guide).
The signaling described previously takes place in signaling channels kept
separate from the channels used for data transmission. The SAAL
(Signaling AAL) is the adaptation layer used in these signalling channels.
The SAAL provides a reliable transmission service to the signalling layer
above it, since this layer does not possess any error-compensation
mechanisms of its own. This is implemented using SAAL's service-specific
convergence sub-layer, the SSCOP protocol (Service Specific
Connection-Oriented Protocol).
The SSCOP has a message set of 16 messages called PDUs (Protocol Data
Units) together with a set of watchdog timers. The SD and SDP PDUs
carry the signaling protocol described previously. The watchdog timers
allow the system to continue operating when a response to a message is
not received within an expected time interval.
Table 30 shows the SSCOP PDU set according to type.
Table 30 SSCOP PDUs According to Type
Function
Establishment
Release
Resynchronization
Reject
Assured data transfer
Unassured data transfer
PDU Description
BGN Request initialization
BGAK Request Acknowledgment
END Disconnect Command
ENDAK Disconnect Acknowledge
RS Resynch Command
RSAK Resynch Acknowledgment
BGREJ Reject initialization request
SD Sequenced data
SDP Sequenced data with ack request
POLL Sending status with receive status
polling
STAT Receive status
USTAT Unsolicited receive status
UD Unnumbered data packets