Why does OpenBMC use Avahi mDNS instead of SSDP - proposal

[Joseph Reynolds]

On 4/17/20 11:44 AM, Gunnar Mills wrote:
> On 4/16/2020 7:42 PM, Richard Hanley wrote:
>>
>>     > The members on the call really wanted to encourage OpenBMC to
>>     implement
>>     > SSDP instead.
>>

Thanks for helping to move this forward.  IMHO, Redfish has given us 
enough direction to move forward with OpenBMC.  I understand the debate, 
but don't have any insight or energy to contribute.  So on a purely 
practical level...

I hereby propose implementing ManagerNetworkProtocol.Oem.OpenBMC.mDNS.
Its schema would either be "Protocol" or a new "mDNSProtocol" modeled 
after SSDProtocol.
The only property I need to be readwrite is ProtocolEnabled.
This allows the BMC admin to enable and disable OpenBMC's Avahi-based 
mDNS discovery service.

- Joseph

>>
>>     It probably isn't a bad thing to be able to support SSDP, don't
>>     get me
>>     wrong, but "instead"?  Why would we want to take away service
>>     advertisement functionality, unless someone wants to explicitly
>>     disable it?
>>
>>     I can understand if they don't want to document, in the standard,
>>     a way to
>>     advertise the Redfish service over mDNS, but isn't that a different
>>     problem from what we're asking for?  Aren't we asking for a method to
>>     manage the enablement of services on the BMC, specifically our mDNS
>>     service?  So, if we still have mDNS, don't we need a way to
>>     configure it
>>     through Redfish?
>>
>> I see your point here.  I guess there might be some implicit 
>> assumption that adding it to a schema implies endorsement elsewhere.
>
> Yeah, from Jeff's reply on the thread, "The concern is if we add this 
> to ManagerNetworkProtocol, it would seem to indicate that Redfish 
> supports mDNS/DNS-SD for discovery of Redfish services, which it does 
> not (SSDP is the standard discovery mechanism). "
>
>> Discovery is probably an area where supporting a diversity of 
>> protocols is better than making a single choice.
>
> A bit over my head here, but I believe Redfish's interoperability 
> concern about supporting a second discovery protocol comes from then 
> all Redfish implementations need to implement both otherwise different 
> Redfish implementations aren't discoverable. This can be expanded to 
> OpenBMC's use of mDNS vs Redfish's SSDP and hence the ask for OpenBMC 
> to implement SSDP. A concern of compatibility of OpenBMC-based Redfish 
> implementations vs other Redfish implementations.
>
> These are all good questions. Anyone can sign up for an account and 
> post to the Redfish forum if you are interested in pursuing.
> https://redfishforum.com/thread/267/add-avahi-managernetworkprotocol
>
> Forum posts, along with new issues and proposals, are discussed on the 
> main Redfish calls, Tuesday at 1:00 PM CT and Thursday at 2:00 PM CT 
> if your company is a supporting member of Redfish.
>
> Thanks,
> Gunnar
>