Multiple BMCs in a system: IPMB? Redfish? MCTP?

[Vijay Khemka]

Nancy,
As IPMI is still a legacy so ipmb will still be used I guess 😊. Once MCTP starts getting supported widely and they become more stable and generic then it can be used. But currently it is still a challenge to use across all devices.

-Vijay

From: Nancy Yuen <yuenn at google.com>
Date: Wednesday, April 29, 2020 at 6:32 PM
To: Vijay Khemka <vijaykhemka at fb.com>
Cc: OpenBMC Maillist <openbmc at lists.ozlabs.org>
Subject: Re: Multiple BMCs in a system: IPMB? Redfish? MCTP?

Vijay, I wonder if IPMB would still be used in later generations or would something like MCTP be considered?
----------
Nancy


On Wed, Apr 29, 2020 at 5:42 PM Vijay Khemka <vijaykhemka at fb.com<mailto:vijaykhemka at fb.com>> wrote:
Nancy,
We have multiple hosts which has a small controller called BIC (Bridge IC). This BIC on each host connected via i2c to main BMC and communicates through ipmi messages to BMC over IPMB/i2c.

Regards
-Vijay

From: Nancy Yuen <yuenn at google.com<mailto:yuenn at google.com>>
Date: Wednesday, April 29, 2020 at 5:25 PM
To: Vijay Khemka <vijaykhemka at fb.com<mailto:vijaykhemka at fb.com>>
Cc: OpenBMC Maillist <openbmc at lists.ozlabs.org<mailto:openbmc at lists.ozlabs.org>>
Subject: Re: Multiple BMCs in a system: IPMB? Redfish? MCTP?

Neeraj, I was not considering aggregation in this case, just having the intermediate BMC "route".

Vijay, thanks.  I was wondering what your applications for IPMB were for.  What's the rationale for using IPMB vs something else?  In your multihost system, one BMC supports multiple host CPUs?  Are there also multiple BMCs?

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Nancy


On Wed, Apr 29, 2020 at 5:15 PM Vijay Khemka <vijaykhemka at fb.com<mailto:vijaykhemka at fb.com>> wrote:
Hi Nancy,
We are currently using (1) in our current multi host design. Option (3) also looks good.

Regards
-Vijay

From: openbmc <openbmc-bounces+vijaykhemka=fb.com at lists.ozlabs.org<mailto:fb.com at lists.ozlabs.org>> on behalf of Nancy Yuen <yuenn at google.com<mailto:yuenn at google.com>>
Date: Wednesday, April 29, 2020 at 3:53 PM
To: OpenBMC Maillist <openbmc at lists.ozlabs.org<mailto:openbmc at lists.ozlabs.org>>
Subject: Multiple BMCs in a system: IPMB? Redfish? MCTP?

I've talked with some people a while back (long while back) about multiple BMCs in a system.  Either for redundancy or managing separate parts of a system.   I'm wondering what other people are thinking in this area if at all.

We are considering similar designs and I'm looking into options for BMC-BMC communications.  Some BMCs may not be externally accessible. Here are some options that we've looked at:

  1.  i2c/IPMB
  2.  usbnet/Redfish
  3.  i2c/MCTP/PLDM or something else?
  4.  internal network via switch chip/Redfish or MCTP
 I'd like to reduce our use of IPMI so I want to avoid (1).

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Nancy
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