Subject: [Ipoverib] link descriptor in address resolution packets

From: Vivek Kashyap <[email-masked]>
Date: Tue, 15 Jan 2002 16:37:10 -0800 (PST)

I feel the argument on including the LIDs vs. GIDs is
        revolving round two issues:

	GIDs : Why are they needed ?

                They cannot be justified by saying that IP subnets can
                span IB subnets because no benefit has been listed.
                Nor is the IB specification anywhere near providing
                such an infrastructure.

	LIDs : Get from SA

                It is wrong to link LID lookup to getting the
                information from the SA because other information is
                kept at the SA. This is because the other information
                can be got in implementation dependent way. The two
                are disjoint.

        How about agreeing to disagree and do the following in
        address-resolution packets:

	GID + QPN + Cap flags + LID

        The order is as specified above. Those that don't want to use
        the LID can ignore it in received packets and not record it in
        their information. All they are asked to do is record their
        own LID when sending the address-resolution request/reply.
        They ignore the LID in the request/reply they receive. Note
        that this format has nothing to do with the format in which
        the link address is recorded in the system.

	That should work for all implementations.

Vivek

-- 
Vivek Kashyap
Linux Technology Center, IBM
[email-masked] 
[email-masked] 
503 578 3422 (o)

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From: Yaron Haviv <[email-masked]>
Date: Wed, 16 Jan 2002 04:02:16 +0200

Vivek, as you could see I back you in the need for LID
However I'm sure we must have the GID as the primary address
There is a need for IP spanning IB this is what I hear from many of the data
centers I visit
As noted in few of the emails there are also few other reasons for GID

We need to maintain the tables by the GID, however I support taking the LID
to return the answer to the caller (avoiding the SM)
I'm not sure that we could take the LID from the packet since someone might
forward it somehow (like and ARP server or something like that)

No one mentioned in the arguments the additional latency caused by going to
the SM (for the LID)
As a central resource that probably has queuing it might take time
Not to mention the latency in IP span IB case (needing to resolve all the
path)

Give Vivek a break, lets put the LID in the header

Yaron

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Vivek Kashyap
Sent: Wednesday, January 16, 2002 2:37 AM
To: [email-masked]
Cc: [email-masked]
Subject: [Ipoverib] link descriptor in address resolution packets

        LIDs : Get from SA

Vivek