HP Moonshot 1500 Chassis User Manual download pdf (Page 149)

Send Message command with response tracking

The Send Message command is used primarily to direct the MC to act as a proxy that translates

a message from one IPMI messaging protocol to another. The MC formats the data for the target

channel type and protocol and delivers it to the selected medium.

Media such as the IPMB do not include channel number and session information as part of their

addressing information. As a result, request messages from another channel must be delivered as

if they originated from the MC itself.

If the bridged message is a request, it is necessary for the MC to hold onto certain data, such as

originating channel and session information, so that when the response message comes back it

can reformat the response and forward it back to the originator of the request. The primary way

the MC accomplishes this is by assigning a unique sequence number to each request that it

genearates, and saving a set of information in a Pending Bridged Response table that is later used

to reformat and route a response back to the originator of the request.

The sequence number returned in the response is used to look up who generated the original

response, the saved formatting and address information. The MC then reformats and delivers the

response to the original requester and deletes the request from its list of pending responses. The

Send Message command includes a parameter that directs the MC to save translation information

for and track outstanding request messages for the purpose of routing the response back to the

originator of the Send Message command.

NOTE: With the exception of messages to SMS, when the Send Message command is used

to deliver a message to a given medium the message appears to have been originated by the MC.

This means that a controller on the IPMB can’t generically distinguish a bridged request from SMS

from a bridged request from LAN.

Table 120 Message bridging mechanism by source and destination

MC tracks pending

responses

Delivery

MechanismMessage Type and direction

noSend MessageRequest or Response from system interface to any other channel

noMC LUN 10bRequest or Response to system interface from any other channel

yesSend MessageRequest from any channel except system interface to IPMB

yesMC LUN 00bResponse from IPMB to any channel except system interface

Bridged Request Example

This example illustrates a Send Message command from the LAN being used to deliver a request

to IPMB.

The MC uses the sequence number that it places on the bridged request to identify the channel

where the request came from and where to send the response. It is important for the MC to ensure

that unique sequence numbers are used for pending requests from each channel. It is also important

that sequence numbers are unique for successive requests to a given responder. One way to

manage sequence numbers to the IPMB is to track them on a per responder basis. This can be kept

in a table of Pending Bridged Response information.

In order to get the response back to the LAN, the IPMB response must return the same sequence

number that was passed in the request. The management controller uses the sequence number to

look up the channel type specific addressing, sequence number, and security information that it

stored when the request was forwarded. For example, if the channel type is LAN then the response

message must be formatted up in an RMCP/UDP packet with the IP address of the requester, the

sequence number passed in the original request, the appropriate security key information, and so

on.

Bridging 149

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HP Moonshot 1500 Chassis User Manual Page 149

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