[openib-general] Re: RDMA connection and address translation API

[Michael S. Tsirkin]

Quoting r. Roland Dreier <rolandd at cisco.com>:
> Subject: Re: RDMA connection and address translation API
> 
>     Michael> Wouldnt it be better to use some bits in the service ID
>     Michael> field for this?
> 
> This would also be OK.  But Annex 3 of the IBA spec has already
> defined the service ID field without any reserved bits we can use.

What about using an Externally Administrated Service ID?
Openib gets
Service ID = 0x1H00 1405 XXXX XXXX
where H is any digit.

> For example, if the first byte is 0x01, then the IETF is allowed to
> use any value they want for the rest of the service ID.

Would not an IETF specified service already use some specific format
for CM private field?

> So if we want to keep backwards compatibility with the spec, this
> approach might be difficult.

I'm not sure I understand. Do envision using the new CM REQ message to
connect to an existing application?

> Anyway, what's the disadvantage of using a reserved bit or two from
> the CM REQ?

I agree that using reserved bits in the CM REQ will work.

I simply noted that Service ID is de facto used to specify the private
data format.  For example if you put anything other that the SDP HH
message in the private data, and attempt to connect to 
Service ID = 0x0000 0000 0001 XXXX
then an IB spec 1.2 compatible SDP implementation will respond and will
interpret the private data wrongly.

-- 
MST