Subject: Re: [Ipoverib] GID clarifications

From: Ajoy C Siddabathuni <[email-masked]>
Date: Thu, 04 Dec 2003 18:00:05 -0800 (PST)

! As you point out, determining the sender's address is problematic in either
! case (dlpi or non dlpi): in the case of dlpi though, the onus is on the driver
! to provide the information (dlpi apps expect it), whereas in non dlpi case, 
! programs can choose to solve the problem in their own unique ways.

In either case, if the driver can determine/pass some information about the
pkt's underlying transport(ud qp in this case) hdr details to the app, then
that app will have an easier time figuring out the rest.

! Using GID0 always is one way to solve the problem for everyone, the other is 
to require 
! using GRH for every packet transmitted, but that has a performance impact and
! is thus not desirable.
! 
! > 
! > Finally, if we were to make a case with such assumptions as above, do we 
then
! > reconsider all uses of "RECOMMENDED/SHOULD" in the rfc.
! >
! 
! If there is an interop issue, or a case where some established practice or
! software breaks (due to an implementation not following recommendation), in my 
! opinion, we should think about the item seriously. 

Usually we seriously think about fixing the erring implementation, if it was
meant to interoperate; not go about rewriting specs; that said, in general
flexibility is good, but it is also well understood that going by the rfc's
recommendations will buy you interoperability; and the current wording seems
to be consistent with that.

~Ajoy
 
! Is there a reason you are opposed to changing the RECOMMENDED to a REQUIRED
! in this specific case? Vivek mentioned there was inclination towards allowing
! the flexibility, and I generally agree to that; but in this case, curtailing
! the flexibility is solving a problem, without creating any new ones I am aware 
! of.
! 
! Thanks.
! 
! Kanoj
! 
! 
! 
! > thx,
! > ~Ajoy
! > 
! > !
! > ! Thanks.
! > !
! > ! Kanoj
! > !
! > ! >
! > ! > thx,
! > ! > ~Ajoy
! > ! >
! > ! > !
! > ! > ! Vivek
! > ! > !
! > ! > ! On Wed, 3 Dec 2003, Kanoj Sarcar wrote:
! > ! > !
! > ! > ! > Vivek Kashyap wrote:
! > ! > ! > >
! > ! > ! > > Kanoj,
! > ! > ! > >
! > ! > ! > > The port's GUID is it's EUI-64 identifier. A GID, in turn can be
! > formed
! > ! > using this GUID, the CA's GUID or some other value. Any GID is unique in 
the
! > IB
! > ! > fabric however only by using the port's GUID/EUI-64 identifier can one
! > uniquely
! > ! > identify the port. The other GID's, as noted, can be applied to other 
ports
! > too
! > ! > - though not concurrently. The GID formed using the EUI-64 identifier is 
the
! > ! > 'GID at index 0'. I've made note of your comment and can clarify further 
as
! > ! > needed.
! > ! > ! > >
! > ! > ! > > wrt, using only GID at index 0 as in the MAC address, there have 
been
! > ! > proponents of using the other GIDs (non EUI-64 GID).
! > ! > ! > >
! > ! > ! > > Vivek
! > ! > ! >
! > ! > ! > Vivek,
! > ! > ! >
! > ! > ! > Per IBA 1.1 section 4.1 EUI-64 subsection and 4.1.1 item 2, 
manufacturer
! > ! > assigned and
! > ! > ! > SM assigned values are required to be EUI-64 compliant (they differ 
only
! > in
! > ! > u/l bits).
! > ! > ! > Thus, all GIDs contain an EUI-64 in the lower 64 bits; thus saying 
"GUID
! > is
! > ! > its EUI-64
! > ! > ! > identifier" might be confusing. Saying "GUID using manufacturer 
assigned
! > ! > EUI-64 identifier"
! > ! > ! > or better "GID index 0" removes all confusion. I think we agree on 
the
! > ! > intent, I just
! > ! > ! > want to make sure if you use the term GUID, you do specifically 
define
! > what
! > ! > you mean
! > ! > ! > by it.
! > ! > ! >
! > ! > ! > Regarding MUST vs RECOMMENDED, is it worthwhile reconsidering given 
that
! > ! > ! >
! > ! > ! > 1. SM assigned GIDs are not that popular (anymore?)
! > ! > ! > 2. it allows determination of sender's ipoib address, thus allowing
! > ! > (receiver side)
! > ! > ! > implementations to be dlpiv2 conformant?
! > ! > ! >
! > ! > ! > Thanks.
! > ! > ! >
! > ! > ! > Kanoj
! > ! > ! >
! > ! > ! >
! > ! > ! >
! > ! > ! > > --
! > ! > ! > > Vivek Kashyap
! > ! > ! > > Linux Technology Center, IBM
! > ! > ! > > [email-masked]
! > ! > ! > > [email-masked]
! > ! > ! > > Ph: 503 578 3422 T/L: 775 3422
! > ! > ! > >
! > ! > ! > >     Kanoj Sarcar <[email-masked]>
! > ! > ! > >     Sent by: [email-masked]
! > ! > ! > >
! > ! > ! > >     12/02/2003 03:54 PM
! > ! > ! > >     Please respond to Kanoj.Sarcar
! > ! > ! > >
! > ! > ! > > Hi,
! > ! > ! > >
! > ! > ! > > It seems that certain parts of the
! > ! > ! > > draft-ietf-ipoib-ip-over-infiniband-05.txt draft might
! > ! > ! > > require clarification. For this discussion, please refer to
! > ! > ! > >
! > ! > ! > > 1. section 9.1 Link Information says:
! > ! > ! > > "The GID, if formed using the GUID, can be used to unambiguously
! > ! > ! > > identify an endpoint."
! > ! > ! > >
! > ! > ! > > 2. section 9.1.1 Link Layer Address/Hardware Address, part c) 
says:
! > ! > ! > > "It is RECOMMENDED that the GID formed by the combination of the
! > ! > ! > > IB subnet prefix and the port's GUID be included in the
! > ! > ! > > link-layer/hardware address."
! > ! > ! > >
! > ! > ! > > Can comment #2 be safely taken to mean that GID index 0 is
! > ! > ! > > being RECOMMENDED? Port GUID seems somewhat ambiguous, since I
! > ! > ! > > am not sure (after reading IBA 1.1 section 4.1) whether the
! > ! > ! > > term GUID refers only to the manufacturer assigned value that 
appears
! > ! > ! > > in lower 64 bits of GID index 0, or whether it also includes
! > ! > ! > > lower 64 bits of SM assigned GIDs at higher indices. If GID index 
0
! > ! > ! > > was really intended, the comment should explicitly state so to 
prevent
! > ! > ! > > confusion.
! > ! > ! > >
! > ! > ! > > Also, to make things simple, is it reasonable to REQUIRE
! > implementations
! > ! > ! > > to always use GID index 0 (maybe this depends on whether existing
! > ! > ! > > implementations all use GID0 only)? The reason this might be
! > ! > ! > > interesting is that when a node receives a packet without a GRH
! > ! > ! > > (whereby it already knows the sender's LID and QPN), it can 
possibly
! > ! > ! > > reverse lookup the sender's LID to identify the sender's GID index
! > ! > ! > > 0 and concatenate the sender's QPN to figure out the sender's link
! > ! > ! > > address. Thus, a receiver can always figure out the sender's 
address,
! > ! > ! > > even when a GRH is not present. This would be similar to ethernet,
! > ! > ! > > where a receiver can always determine a sender's address, and thus
! > ! > ! > > is more DLPIv2 (unitdata_indication) friendly.
! > ! > ! > >
! > ! > ! > > Regarding comment #1, what does "unambiguously identify an 
endpoint"
! > ! > ! > > mean? GIDs are unique in the subnet; and if an IP link contains
! > ! > ! > > members in multiple IBA subnets, the subnet prefixes will 
disambiguate
! > ! > ! > > which endport is being referred.
! > ! > ! > >
! > ! > ! > > Thanks.
! > ! > ! > >
! > ! > ! > > Kanoj
! > ! > ! > >
! > ! > ! > > _______________________________________________
! > ! > ! > > IPoverIB mailing list
! > ! > ! > > [email-masked]
! > ! > ! > > https://www1.ietf.org/mailman/listinfo/ipoverib
! > ! > ! >
! > ! > ! > _______________________________________________
! > ! > ! > IPoverIB mailing list
! > ! > ! > [email-masked]
! > ! > ! > https://www1.ietf.org/mailman/listinfo/ipoverib
! > ! > ! >
! > ! > ! >
! > ! > !
! > ! > ! __
! > ! > !
! > ! > ! Vivek Kashyap
! > ! > ! Linux Technology Center, IBM
! > ! > !
! > ! > !
! > ! > ! _______________________________________________
! > ! > ! IPoverIB mailing list
! > ! > ! [email-masked]
! > ! > ! https://www1.ietf.org/mailman/listinfo/ipoverib
! > !
! > ! _______________________________________________
! > ! IPoverIB mailing list
! > ! [email-masked]
! > ! https://www1.ietf.org/mailman/listinfo/ipoverib

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