[openib-general] IPoIB Loading and Starting

[Michael Krause]

At 09:23 AM 9/27/2004, Roland Dreier wrote:
>     Michael> The SM only knows what it configures in each port.  The
>     Michael> SA is responsible for service management and it works
>     Michael> with the SM to map a given service to a P_Key.
>
>As far as I know there is no service (in the IB service record sense)
>associated to IPoIB, is there?

Additional services can be defined beyond the base IB service record.  For 
IP, the following would solve the problem:

- Have the SA define an IP service (this can be done for other protocols as 
well).  This can be done using the Service ID annex specification (much of 
this annex is focused on an endnode but for this purpose, the SA can be 
viewed as a logical endnode).  The SA registers the service providing a 
single point of management for the subnet.

- Each endnode issues request targeting the IP service identifier for each 
P_Key that is configured in the port.  The SA response determines whether 
the IP service is supported on this interface.

- For each P_Key, the endnode probes for the "all nodes" multicast address 
and joins / creates accordingly.

Given P_Key can come and go, the endnode can set up an event notification 
when the IP service is updated.  This allows dynamic configuration without 
having an administrator interact with each node.

The above approach is both scalable and relatively simple to implement and 
manage.


>     Michael> IPoverIB is required to inquire what groups are available
>     Michael> and optionally set up event notification to be informed
>     Michael> when groups are added for its particular service.  This
>     Michael> eliminates the need for local P_Key management.
>
>I don't see this requirement anywhere in the current IETF drafts,
>although I could be missing it.  In any case this seems rather ugly,
>since the only way to get a list of IPoIB multicast groups seems to be
>to query for _all_ multicast groups, filter for those that match the
>IPoIB GID format, and then attempt to join to find out which can be
>used on each local port.
>
>     Michael> In general, the IPoverIB driver should treat each new
>     Michael> all-nodes multicast group with a unique P_Key as a
>     Michael> virtual hot-plug event (this was our intent both within
>     Michael> the IETF and in the IBTA).
>
>Hmm.. this view does not seem to match the wording of the current IPoIB 
>drafts.  For example:
>
>         It is an implementation choice on how the P_Key and the scope
>         bits related to the IPoIB subnet are determined by the
>         implementation. These could be configuration parameters
>         initialized by some means by the administrator.
>
>         The methods employed by an implementation to determine the
>         P_Key and scope bits are not specified by IPoIB.

It was not specified due to the lack of standards for higher-level service 
management which partitioning is classified.  Given there is an OpenSM 
effort in flight and the Service ID spec is already in existence, it isn't 
that tough to acquire an IP service ID (or any other protocol that one 
wants to support) and implement a solution along the lines that I describe 
above.  This would lead to a more dynamic environment while reducing the 
impact to the administrator.

Mike 
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