Subject: Re: [Ipoverib] IPoIB link address

From: "H.K. Jerry Chu" <[email-masked]>
Date: Mon, 22 Sep 2003 15:55:55 -0700 (PDT)

>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?

You should look at the link & multicast draft, not the encapsulation
draft for the Q_Key assignment. In that draft Q_Key is described as an
IPoIB link attribute shared by both IPv4 and IPv6. (See section 6.2 IPoIB
Link Q_Key.)

>
>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.

See above. Q_Key and MTU are considered "link" attributes. By definition,
IPv4 and IPv6 running on top of the same link must use the same set of
"link" attributes. If this is not clear from the current drafts we can
certainly fix it. (Well Vivek and I are working on combining the two drafts
into one. One benefit of the merge is to remove any possible inconsistency.)

Thanks for pointing this out,

Jerry (speaking obviously as a co-author not a co-chair)

>or
>2) Create a single broadcast GID to define the link.
>
>-Vandana
>  
>
>
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---

From: Vandana Rao <[email-masked]>
Date: Mon, 22 Sep 2003 21:26:04 -0700

Hi,
>IPoIB link attribute shared by both IPv4 and IPv6. (See section 6.2 IPoIB

So what you are saying is that because of what is said in the link & 
multicast draft, the 2 broadcast
groups have to have the same link attributes, i.e. the option #1 indicated 
below is the solution. If this is the case, either draft should at the very 
least make this requirement explicit.

I would prefer to have a single broadcast group for both IPv4 and IPv6 as I 
do not understand the rationale behind requiring the IPoIB driver to 
maintain IP specific information.
-Vandana

---

From: Roy Brabson <[email-masked]>
Date: Tue, 23 Sep 2003 10:10:57 -0400

> IPoIB link attribute shared by both IPv4 and IPv6. (See section 6.2 
IPoIB

This is news to me.  Even after re-reading the section, I did not realize 
that this was a requirement.  I think this is because I saw the IPv4 and 
IPv6 IPoIB links as "separate" logical entities where all IPv4 partners 
need the same Q_Key and all IPv6 partners need the same Q_Key, but the two 
do not necessarily need to match.  I agree with subsequent comments: if it 
is required that the Q_Keys for IPv4 and IPv6 must match, then it should 
be explicitly stated, and the appropriate action for an IPoIB node to take 
if this is not true should be documented.  As it is now, it is certainly 
vague enough that people are reading the same text and drawing different 
conclusions as to what the text is saying.

Roy