[ofa-general] Service ID scope in IB Arch Spec A3.2.2 is incorrect, right?

[Sean Hefty]

Scott Guthridge wrote:
> IB Architecture Spec, r1.2 section A3.2.2 says [emphasis added]:
> 
>    Each *port* on a CA may support a set of services. ... Since *not all
>    ports* support the same set of services...
> 
> and later:
> 
>    "it is the combination of the Port GID and Service ID that identifies a
>    particular service provider"
> 
> 
> But this seems to contradict chapter 12 (communication management) and
> chapter A8 (device management) which consistently associate services with
> channel adapters, not ports.  See 12.6.5 table 99 (CA GUID), 12.6.8 table
> 103 (CA GUID), 12.9.9 connection state table (CA GUID), etc.  Similarly,
> figure 309 "I/O Components and Relationships" in section A8.2.3 that shows
> the DM agent being a component of the I/O Unit, and because the I/O unit is
> associated with a single TCA, it follows that the DMA belongs to the
> channel adapter, not to a particular port.
> 
> The CM implementation in OFED 1.2 supports this notion that services are
> defined per CA, not per port in that ib_create_cm_id doesn't take a port
> number.

In short, I really don't know the answer here.

Automatic path migration allows a connection to migrate between ports on 
the same HCA.  So, from at least that view, a service can be viewed as 
being defined per CA, not per port.  However, service records are tied 
to a specific port.

Also, the IB CM is not required to be implemented on each port; CM 
support is a per port attribute.  Viewing the CM as a service is per 
port, not per CA.

I'd need to verify this, but I don't think that a connection request 
architecturally even has to be received on the port that the connection 
will use.  I wouldn't interpret too much from the ib_create_cm_id API. 
The use of the CA GUID in CM req/rep message helps detect 
stale/duplicate connections, since QPs are per HCA, and not per port.

I'm not sure how this relates into section A8.

> So am I correct that A3.2.2 has it wrong?  Would it be right to say that
> with respect to provided services, all ports of a given CA are equal?

I don't believe you can say this.  The port attributes can be different. 
  The ports could be on different subnets.  An SM could be running on 
one port, but not another.  Etc.

- Sean