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Transport aspects 2

S.4.2.2 Actions for vendor-specific usage and download process

The following actions are available for vendor-specific use, but optional. If the NT does not support a given
action, it should respond with a reason code indicating "command not supported".
Get software image: Retrieve attributes of a software image instance. This action is valid for all software
image instances.
Start download: Initiate a software download sequence.
Download section: Download a section of a file.

End download: Signal the completion of a file download, providing CRC and version information for final
verification, if supported. This action causes the file to be stored in the NT's non-volatile memory.

NOTE – The download mechanism supports downloading of a zero byte file to the NT. This is done using a start
download command specifying an image size of zero, followed by an immediate end download, with a zero CRC and
also specifying an image size of zero. The action the NT takes from this messaging is beyond the scope of this annex. It
is vendor discretionary whether the NT recognizes downloading a file of size zero as a file delete operation, or as a file
replace operation, or as any other vendor discretionary operation.
Activate image: Effectuate the file, for example by loading its contents into NT hardware. If appropriate,
the hardware or application may be reinitialized. Set the is active attribute value to 1 for the target file
instance.

Commit image: Set the is committed attribute value to 1 for the target file instance, if supported. The
semantics of this operation are vendor-specific; there is no de-commit action.

S.4.3 OAM data for software management

The OAM data for software management process is transparently exchanged between ME-O and ME-R. The
messages described in the subsequent section are to be included in the payload of a datagram eoc
command (see clause 11.2.2.4.2). Each message in clause S.5 sent from ME-O to ME-R or from ME-R to ME-
O is included as payload of exactly one datagram eoc command without additional data or protocol. The
message size is limited by the maximum payload size of the datagram eoc command (up to 1018 bytes in
length).
Support of the datagram eoc command (see Table 11-6) is mandatory for Annex S.

Some of the messages in clause S.5 require a response. The response shall be sent within 300 ms. The
sending ME shall consider the message as lost if the corresponding response is not received within 400ms.
S.4.3.1 Transaction correlation identifier

The transaction correlation identifier is used to associate a request message with its response message. For
request messages, the DPU shall select a transaction identifier that avoids the possibility of ambiguous
responses from NTs. A response message carries the transaction identifier of the message to which it is
responding.
S.4.3.2 Message type field

The message type field is subdivided into four parts. These are shown in Figure S.2.

Bit
7 6 5 4 0
0 AR AK MT

Figure S.2  Message type field subdivision

Bit 7, the most significant bit, is reserved for future use by ITU-T. It shall be set to 0 by the transmitter and
ignored by the receiver.

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