Total Control MP/16, Operator'S Manual

Page: 49 / 182

The Chassis MIB 3-13
the device. Because the NMC needs to support the TFTP protocol
and, as a result, the entire IP stack, a large portion of the NMC’s
operational code remains running. Moreover, the SDL
functionality is built int o the NMC’s operational code. In this way,
SNMP-initiated SDLs need not transfer an .SDL file when NMC
SDL is triggered.
Initiating NMC SDL is performed in the same manner as for
NACs—by setting the uchasCmdFunction in the uchasCmdTable
to softwareDownload(5) for slot 3. This places the NMC in an SDL
state. As a result, all subsequent SNMP agent operation is
suspended, and any incoming SNMP GET or SET requests are
immediately turned around and sent back as GET responses with a
generic error.
Executing the SDL command forces the NMC to erase its Flash
ROM. During this time, the SNMP error-status object (in response
to incoming requests) is set to 125, meaning the NMC is in an SDL
state and is erasing its Flash. Once the Flash is erased, the NMC
changes SDL state, forcing subsequent SNMP requests to be
returned with error-status objects set to 124. This is the MS’s
trigger to begin the .NAC file transfer.
The following TFTP command is issued to download the .NAC file
to the NMC:
TFTP -B NM020200.NAC
192.77.203.65=NM020200.NAC
The first TFTP data packet carries the .NAC file’s header, which the
NMC uses to validate the .NAC file. If the validation passes,
subsequent data packets are sent until the entire .NAC file is
transferred. After a complete successful .NAC file transfer, the MS
should wait for the NMC to reboot and become operational with
the newly downloaded code. If the .NAC file transfer is
unsuccessful and the TFTP transfer is aborted, the NMC will
remain in the “ waiting for SD L ” mode (blinking green Run/Fail
LED). After waiting for the NMC to re-erase its Flash ROM, the
MS may re-initiate the TFTP transfer.
There is no need to re-issue the softwareDownload(5) command. If
the MS must verify that the NMC has finished erasing Flash and is
waiting for SD L , it may issue any SNMP request and match the
124 generic error code in the corresponding response.
Note that once the NMC has erased its operational software from
the Flash devices, the NMC's network protocol stack exists only in
RAM. Power cycling the NMC at this point means that the NMC