Expand Configuration and Management Manual (G06.24+)

Subsystem Description
Expand Configuration and Management Manual—523347-008
18-14
Protocol Packet Types
Connection Reset (CONN RST)
A CONN RST is a connection-establishment–reset-setup packet. This packet is sent
by $NCP at one of the two end nodes if a packet sequence problem is detected during
connection establishment.
Node Status (NODE STAT)
A NODE STAT is a connection-establishment–system-status setup packet. This packet
is sent only from C-series nodes and is exchanged by the requesting and responding
$NCP to inform the other $NCP of its respective processor status and operating
system version numbers. NODE STAT packets must be exchanged before any other
data can be exchanged over a logical connection.
Node Status Acknowledgment (NODE ACK)
A NODE ACK is a connection-establishment–system-status acknowledgment setup
packet. This packet is exchanged by the requesting and responding $NCPs to
acknowledge the receipt of a NODE STAT packet. The exchange of this packet
completes the logical connection-establishment setup between $NCP at two C-series
end nodes.
Link Request (LRQ)
An LRQ is a request data packet. LRQ packets are exchanged between Expand line-
handler processes over an open communications path. The buffer used to hold the
LRQ is not deallocated until a response to the LRQ is received.
A single request message may require multiple LRQ packets. The first LRQ includes
request-message size information. The recipient of the LRQ uses the request message
size information to allocate sufficient buffer space to receive the request message.
LRQs also include a MORE bit to indicate that additional LRQs will be sent.
Link Complete (LCMP)
An LCMP is a reply data packet. These packets are exchanged between Expand line-
handler processes over an open communications path.
A single reply message may require multiple LCMP packets. A reply message is sent
in response to each request message whether or not data is requested by the sender
of the request message (the requester). When the requester receives an LCMP, it uses
the buffer space initially allocated for the LRQ to receive the LCMP. Once all the
LCMPs have been received, the buffer is deallocated.
Note. For D-series and G-series nodes, the processor status and operating system version
numbers are sent in the connection-establishment request/reply packets.