On 31/07/09 19:58, Todd Rimmer wrote:
>> Yossi Etigin wrote:
>  
>> What if we query the remote port LMC once, when the path is resolved,
>> and then
>> use it to mask the LID until the path is refreshed again?
> 
> Doing the LMC query when the PathRecord query is made makes, sense.
> 
> I assume you are proposing a query of the SA for the PortInfoRecord?
> 
> Note that a direct query of the remote SMA would be a bad idea and has at 
> least the following issues:
> 1. There are limited VL15 queuing resources and no VL15 flow control, hence 
> if multiple nodes queried the same SMA at the same time, packet loss could be 
> significant which would impact SM operation as well (note how carefully the 
> recent opensm work for parallel queries has had to tune operations to SMAs)
> 2. If MKey security is enabled, the client will not (and should not) know the 
> MKey of the remote SMA and hence can't make a query.
> 3. The intent of the IB Architecture is for the SM to be the only entity 
> which interacts with SMAs.  A handful of diagnostic tools (like ibdiagnet) 
> may be an acceptable exception, but it would not be recommended to make 
> non-SM queries of an SMA as part of a normal protocol.
> 

Actually I wasn't sure which is better, but given all these issues SM should be 
the one and not the SA.

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