Alert Standard Format (ASF) Specification
Alert Standard Format (ASF) Specification v2.0 DMTF Document DSP0136
DSP0136 23 April 2003 Page 20 of 94
Contents Type Offset Value
Destination Address 6 bytes 00h
Source Address 6 bytes 06h
Frame Type 2 bytes 0Ch 0800h
MAC
Header
Version and Header Length 1 Byte 0Eh
Service Type 1 Byte 0Fh
Total Length 2 Bytes 10h
Identification 2 Bytes 12h
Flags & Fragment Offset 2 Bytes 14h
Time to Live 1 Byte 16h
Protocol 1 Byte 17h 11h
Header Checksum 2 Bytes 18h
Source IP Address 4 Bytes 1Ah
Destination IP Address 4 Bytes 1Eh
IP Header
Source Port 2 Bytes 22h
Destination Port 2 Bytes 24h 026Fh or 0298h
1
UDP Length 2 Bytes 26h
UDP Checksum 2 Bytes 28h
UDP Header
Version 1 Byte 2Ah 06h (ASF)
Reserved 1 Byte 2Bh
Sequence Number 1 Byte 2Ch
Class of Message 1 Byte 2Dh 06h (ASF)
RMCP
Header
IANA Enterprise Number 4 bytes 2Eh 4542 (ASF)
Message Type 1 Byte 32h
Message Tag 1 Byte 33h
Reserved 1 Byte 34h
Data Length 1 Byte 35h
Data Variable 36h
ASF RMCP Data
CRC 4 Bytes
3.2.2.1 RMCP Acknowledge
This message is used to acknowledge receipt of an RMCP message only if the recipient supports
the specific RMCP version in that message’s header, the message is not itself an RMCP
Acknowledge, and the header’s Sequence Number is other than FFh (no acknowledge). The
acknowledge message indicates only that the message has been received; it does not indicate
that any action has been completed.
In a typical interaction, the recipient of an RMCP message acknowledges the sender by returning
the received RMCP header with the MSB (most significant bit) of the “Class of Message” field set
to indicate an acknowledgement. Specifically, the recipient returns to the sender the first three
bytes from the received RMCP header (version, sequence number and reserved fields) with the
fourth byte modified to indicate that the message represents an RMCP Acknowledge. If RMCP
security extensions are in use and the message fails its integrity check, an RMCP Acknowledge
is not sent. The following table describes the format of an RMCP Acknowledge:
1
Refer to 3.2.3 RMCP Security-Extensions Protocol (RSP) on page 23 for the definition of the
protocol used for this port.