The IB spec says "A GID is a valid 128-bit IPv6 address (per RFC 2373)
with additional properties / restrictions defined within IBA to
facilitate efficient discovery, communication, and routing.", so I don't
think it needs to say much more. [Perhaps the IB specification should
refer to the more recent RFC 3513 that obsoletes RFC 2373...] One of
those IBA restrictions result from being limited to assigning one 64-bit
value for the upper 64-bits of the GID, called the GID prefix, per IB
subnet. If GIDs are used to represent IPv6 addresses on an IB subnet,
then only one IP subnet prefix can be mapped onto an IB subnet. This
limitation goes along with the additional work of integrating GID
management into the IP management applications for assigning IP addresses.
Restrictions on IP address assignment are removed when using the GID as
specified by the IETF IPoIB as a link layer address and IB partitions
can be used to create multiple IP links per IB subnet. Also, the IP
management application integration effort is significantly smaller.
Therefore, I recommend that a solution for mapping between IP and GIDs
not rely on GIDs being used as the IP addresses.
-David
Michael Krause wrote:
At 10:49 AM 6/30/2005, Roland Dreier wrote:
Michael> Being the person who led the addressing definition for
Michael> IB, I can state quite clearly that GID are NOT IPv6
Michael> addresses. They were intentionally defined to have a
Michael> similar look-n-feel since they were derived in large part
Michael> from Future I/O which had them as real IPv6 addresses.
Michael> But again, they are NOT IPv6 addresses.
The IBA spec seems to have a different idea. In fact chapter 4 says:
"A GID is a valid 128-bit IPv6 address (per RFC 2373)...."
I wrote the original spec here. The text was supposed to be updated
to clarify that the rest of the sentence, i.e. with additional rules,
etc. thus making it not a real IPv6 address from the IETF's
perspective but something quite close. The intention was to allow one
to manage the fabric by having mapping functions from traditional IP
management applications to IB GID to minimize the amount of work to
enable IB within a solution.
_______________________________________________
openib-general mailing list
openib-general@openib.org
http://openib.org/mailman/listinfo/openib-general
To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
