[openib-general] QoS RFC - Resend using a friendly mailer

[Eitan Zahavi]

Hi Todd,
 
> While using the Service ID is an interesting idea, the problem is the
Service ID values
> are not well defined by IBTA.  Rather each endpoint is permitted to
define its own,
> potentially transient set of Service ID values.  The Service ID values
are discovered via
> Service Records in the SA or Device Management queries which get their
data from
> the IOU.
[EZ] Actually there are quite a few rules for how service IDs are made.
Different service vendors are supposed to use different Service-IDs. 
Also this RFC does enforce using Service-IDs in cases where they are not
defined. But it does provide the means to do that when such service are
defined. So in no way you can say it breaks existing implementations.
Just provide a way for applications that do make a constant use of
Service-IDs benefit from that property.

> 
> Hence while a few service ID values are well defined (such as those
for SDP), many
> are not (such as those for MPI, uDAPL, SRP, etc) and may vary between
both
> hardware and software suppliers.  Many are likely to be duplicated
between different
> vendors target devices (for example a uDAPL target application may
duplicate values
> used by an SRP target) and this would not be a problem provided both
applications
> were never run on the same IB Node target device.  Some might even
change on each
> reboot (IBTA spec implies this could be a 64 bit pointer or context in
the target),
> although I'm not aware of any which do.
> 
> I believe it is for the above reasons that IBTA chose not to make
ServiceID part of the
> PathRecord and MultiPathRecord queries.
> 
> As Roland suggest, before implementing a non-standard approach, IBTA
should be
> engaged to define an appropriate extension to the standard.  Such
extensions would
> need to be carefully defined to avoid breaking existing applications
and fabrics.
[EZ] You are welcome to join IBTA and work on this too.
> 
> Todd Rimmer
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