[openib-general] IPoIB Loading and Starting

[Michael Krause]

At 09:16 AM 9/25/2004, Roland Dreier wrote:
>     Michael> I would have thought this would be part of the IP over IB
>     Michael> driver.  Communicate with the SM to acquire the P_Key and
>     Michael> then use that to perform Arp / ND.  Strange to require a
>     Michael> command since this gets a bit cumbersome when there are
>     Michael> many nodes in the fabric.
>
>That is a nice idea in theory but it falls down in practice.  First,
>the IPoIB driver is often loaded during the boot process, and init
>scripts may want to configure IPoIB interfaces before the SM has
>discovered the local node.

If the SM isn't up or hasn't discovered the local node, then the node isn't 
going to be communicating with anything else until this occurs.  To get 
around this race condition, one simply has an event handler associated with 
the change in state of the CA, i.e. the SM has configured the CA so there 
is a clear communication path and P_Key can be discovered.  A CA should 
know when the link is operational as it needs to find the other routing 
information in order to operate.  Hence, boot isn't really an issue if 
using the IB management methods provided in the specifications.

Note: There is nothing that prevents with using a default P_Key (same 
applies to Q_Key) - that wasn't the point.

>  Also, a node may have many P_Keys assigned, only a few of which are used 
> for IP traffic.  Administrators
>don't like to have to deal with 50+ network devices.

What does this have to do with anything?  I'm not advocating having a large 
number of P_Key for IP traffic.  The SM manages the P_Key space for IP - 
can be single P_Key or multiple.  The SM has to understand whether a CA is 
part of a given P_Key domain (same for switch ports).  This is a single 
point of management technology to start with so I don't see the 50+ or even 
48K network device problem.  The IPoverIB spec allows for multiple P_Key to 
be used or just one.  This should all be done by the SM and the CA should 
be asking it for what value to use.  It should not be done within the CA 
else the implementation is establishing management policies that were 
clearly not the intent of the IB specifications and could to 
interoperability problems or more administrative overheads.

Mike
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