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
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