Re: draft-ietf-ipoib-link-multicast-03.txt

"H.K. Jerry Chu" wrote:
> 
> Kanoj,
> ...
> <snip>
> 
> >Of course, if the typical case is that join/attach will not fail
> >(ie the number of mcg's are not too great), we can probably punt
> >on this, but at least with a note that a limit on the number of
> >IP multicast groups exists depending on member hca's and fabric
> >(switch/SM) capability.
> 
> How about adding the following note to the draft regarding this
> vunerability?

Jerry,

Looks good, just one comment below. 

> 
> 11.0 New Vunerability in IB Multicast
> 
>    Many IB multicast functions are subject to new types of failure due
>    to resource constrains compared to Ethernet multicast. This includes
>    the creation of an IB multicast group, the join call, both the
>    "SendOnlyNonMember", the "FullMember", and the "NonMember" joins, and
>    the attaching of a QP to a multicast group.
> 
>    In general, these failure conditions are implementation dependent,
>    and are believed to be rare. Usually a failure can be propagated back
>    to a foreground operation to cause the operation to fail. But some IB
>    multicast functions are not tied to any foreground operation, making
>    their failures difficult to notice. E.g., if an IP multicast router
>    attempts to "NonMember" join a newly created multicast group in the
>    local subnet, but the join call fails, packet forwarding for that
>    particular multicast group will likely to fail silently without the
>    notice of local multicast senders. This type of problems add more
>    vulnerability to the already unreliable IP multicast operations.
> 
>    Implementations should log error messages upon any IB multicast
>    failure.  Network administrators should be aware of this
>    vulnerability, and preserve enough multicast resources if IP
>    multicast will be used heavily, or a certain degree of reliability is
>    expected.

How about somehow adding in verbiage like (this takes care of the most
likely cause of above mentioned failure): E.g, making sure the IP multicast 
router is using an HCA with ample IBA multicast resources.  

Thanks.

Kanoj

> 
> Thanks,
> 
> Jerry
> 
> >
> >Thanks.
> >
> >Kanoj