[ofa-general] [PATCH 1/4] ib/ipoib: specify TClassand FlowLabelwith PR queries for QoS support

[Sean Hefty]

>MTU - at a minimum the PR must request a MTU >= than the interface
>MTU, having a MTU that is exactly equal to the broadcast group MTU
>seems fine to me. The SM should be able to do >= internally.

My thoughts on MTU (and rate) are that since it isn't carried in any of the
headers, we should be able to derive the maximum MTU from the other fields.
Plus, we've had situations in the past where a smaller MTU than the maximum
performed better than the max, so I'm hesitant to add MTU to the query.

>Flowlabel - IBA hasn't really specified what to do with this field. In
>IPv6 FlowLabel is assigned randomly by the host on a per-flow (ie
>socket) basis to allow routers to group packets into flows without
>doing deeper inspection. This becomes important when encryption is
>used and the routers can no longer access the TCP header to find
>flows.

Dropping the flow label from the query is simple enough for IPoIB.  We'll have
to consider what to do with the flowinfo field of an IPv6 address for the
rdma_cm, however.

I'd like the minimal number of fields necessary on the host side to give greater
flexibility to the SA.  Right now, we're only looking at adding traffic class
and, possibly, MTU to the IPoIB PR query.

- Sean