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Chapter
18
18.0 Remote Management Control Protocol
The Remote Management Control Protocol (RMCP) has been defined by the Distributed Management
Task Force (DMTF) for supporting pre-OS and OS-absent management. RMCP uses a simple requestresponse protocol that can deliver IPMI messages using UDP datagrams. RMCP is defined in “Alert
Standard Format (ASF) Specification version 2.0”.
The RMCP+ stack implements the Remote Management Control Protocol Plus (RMCP+) as described
in “Intelligent Platform Management Interface Specification v2.0”.
In addition to full support for IPMI 2.0, this implementation of RMCP+ is backward compatible with
RMCP (as described in “Intelligent Platform Management Interface Specification v1.5”) and provides
the following services (as described in “Intelligent Platform Management Interface Specification
v2.0”):
• RMCP+ message processing
• ASF presence ping/pong messages processing
• RMCP+ integrity, authentication, and encryption algorithms:
• Authentication algorithms supported: RAKP-none, RAKP-HMAC-SHA1, and RAKP-HMAC-MD5
• Integration algorithms supported: None, HMAC-SHA1-96, HMAC-MD5-128, and HMAC-SHA1128
• Encryption algorithms supported: None and AES-CBC-128
In addition, RMCP+ can be configured to use SCTP instead of UDP as a transport protocol to provide
a reliable transport option. Note, however, that this is a custom extension that is not compatible with
RMCP+ as defined in “Intelligent Platform Management Interface Specification v2.0”.
18.1
RMCP Client and Server Communication
RMCP messages are sent using UDP datagrams over the Ethernet. The RMCP server communicates
on management port 623 for handling RMCP requests. This is the primary RMCP port. A secondary
port, 664, is used when encryption is necessary for security.
Note:
The implementation of the RMCP server provided with the RSM firmware package listens for RMCP
packets only on port 623 (the primary RMCP port).
When an RMCP packet arrives, the RMCP server checks the packet. If it is an invalid version or not a
valid IPMI RMCP packet, the server drops the packet. If the session data in the packet is invalid, not
available, duplicated, or out of order, or slots are full, the server returns an RMCP error message to
the RMCP client. Otherwise, the server decodes the RMCP message.
If the message is the RMCP “ping” message, the server returns the RMCP “pong” message to
indicate to the client that it has successfully found an RMCP server. If the RMCP packet contains a
valid message other than “ping”, the message is forwarded through the RSM interface to the
destination indicated in the message. If the RSM receives an appropriate IPMI response from the
final destination, the RSM returns the IPMI response in a properly formatted RMCP message back to
the RMCP server, which then returns the message to the RMCP client over the network.
18.2
RMCP Modes
The RMCP server on the RSM may be configured to operate in one of two modes shown in Table 32,
“RMCP Modes”. The configuration flag is located in shm.conf configuration file and is read on system
startup.
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