RE: IPoIB link address

Bill,

[Vandana had asked me this question and so I brought it up with you and
Jerry. I then requested Vandana to send it to the list. So not a
coincidence :)].

I discussed it with Jerry and it is clear that the drafts are not explicit
in making it a requirement that the attributes have to be the same. There
are implementations that can work with different Q_Keys (since they choose
to support different QPs), however an implementation that cannot/does not
choose different QPs for the two protocols will have to 'work harder'
within the driver to make it work. Therefore I agree that a common set of
Q_Keys (and other attributes) needs to be an explicit requirement.
Architecturally too, a link shouldn't depend on the upper layer protocol --
whether it is v4 or v6 -- it is just a link.

How we do it has two options:

1) Two Broadcast-GIDs

   a) Explicitly require that the two broadcast-GIDs have same attribute
   values
   b) Explicitly require that both the broadcast-GIDs are always created

   This is closer to the current specification except we are adding some
   requirements.

2) One common broadcast-GID

   a) One broadcast-GID that the driver joins. [the protocol signatures can
   still be included in the multicast mappings].

   This is architecturally cleaner and may be for implementation too --
   only one broadcast-GID to be created and joined.



Vivek

--
Vivek Kashyap
Linux Technology Center, IBM
[email protected]
[email protected]
Ph: 503 578 3422 T/L: 775 3422



                                                                                                                                       
                      "bill"                                                                                                           
                      <[email protected]>        To:       "'Vandana Rao'" <[email protected]>, <[email protected]>                     
                      Sent by:                 cc:                                                                                     
                      ipoverib-admin@ie        Subject:  RE: [Ipoverib] IPoIB link address                                             
                      tf.org                                                                                                           
                                                                                                                                       
                                                                                                                                       
                      09/22/2003 04:04                                                                                                 
                      PM                                                                                                               
                                                                                                                                       
                                                                                                                                       




Vandana,

This issue has been discussed in private amongst the authors for a few
days now.  Any chance I can get an opinion from you on your preferences
between 1/2 (and why).  I'd like to get this nailed soon so we can
FINALLY get some forward progress on standards

Bill

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Vandana Rao
Sent: Monday, September 22, 2003 2:31 PM
To: [email protected]
Subject: [Ipoverib] IPoIB link address




Hi,

In the IP encapsulation draft , section 6.1.2, it is indicated that the
Q_Key used should be that of the
broadcast-GID. Which broadcast GID should be used? Specifically, if the
IPv4 and IPv6 broadcast GIDs are assigned different Q_keys, which Q_Key
should be used?

The issue with potentially allowing different Q_Key values for the 2
GIDs
is that 2 separate QPs will have to
be allocated for IPv4 and IPv6 traffic respectively and will require the

IPoIB driver to keep track of upper layer protocols.
If everyone agrees that this is a problem, there are 2 ways to address
the
issue:
1) Require the 2 broadcast GIDs to have the same attributes such as
Q_key,
MTU etc.
or
2) Create a single broadcast GID to define the link.

-Vandana



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