[ofw] [PATCH] DAPL v2.0: common: increase default IB ack timer from 16 to 20

[Davis, Arlin R]

> > For larger, more congested fabrics, a larger ACK timer is needed.
> > Consumers can still change default with environment variable
> > DAPL_ACK_TIMER if they need to increase or decrease.
> >
> > This applies to SCM and UCM providers only. The CMA provider, which
> > uses rdma_cm, has no way to control ack timer with current API.
> 
> The rdma_cm uses the path lifetime to determine the QP timeout value.
> The path record can be manipulated by the user when calling
> rdma_create_ep().

I stand corrected. I guess I should have said "has no direct way". 
Yes, a user can modify path lifetime via rdma_create_ep() but there 
is no way for the user to know how much that will be manipulated and 
increased in the IB CM driver.