Expand Configuration and Management Manual (G06.24+)

Subsystem Description
Expand Configuration and Management Manual—523347-008
18-15
Protocol Packet Types
Link Cancel Request (LCAN)
An LCAN is a control packet that is sent in response to a user request to abort a prior
LRQ.
Data Packet Acknowledgment (ACK)
An ACK is a control packet. It is a positive acknowledgment of a data packet (either an
LRQ or an LCMP). LRQ and LCMP packets can include acknowledgments. An ACK is
only used to acknowledge data packets if no other data packets are ready to be sent.
Negative Data Packet Acknowledgment (NAK)
A NAK is a control packet. It is a negative acknowledgment of a data packet (either an
LRQ or an LCMP) and is evidence of some type of network trouble or potential
configuration mismatch.
Data Packet Enquiry (ENQ)
An ENQ is a control packet. If a data packet (either an LRQ or an LCMP) is not
acknowledged within the Expand Level 4 timeout period, the sending Expand line-
handler process sends an ENQ, and the Level 4 timer is reset and restarted. The
sending line-handler process continues to send ENQs each time the Level 4 timeout
expires until one of the following occurs:
•
The request is acknowledged.
•
The Expand Level 4 retry limit has been reached.
•
An LCMP corresponding to an LRQ is received before the LRQ is acknowledged.
Path Change Status (PCHG CMD)
A PCHG CMD is a path-status-notification change packet. It is exchanged by the
Expand line-handler processes at neighbor nodes when the path status between the
two nodes changes and there are still active lines remaining.
Path Change Status Response (PCHG RSP)
A PCHG RSP is a path-status-response change packet. It is sent by an Expand line-
handler process to another Expand line-handler process in response to a PCHG CMD
packet.
Note. You can control the Expand Level 4 timeout and retry limits by setting the L4TIMEOUT
and L4RETRIES modifiers. These modifiers are explained in Section 17, Expand Modifiers.