Re: [netext] Discussion about "Retransmit Message Identifier Option"//Re: Agenda Requests received

Hi  Xiangsong,

Please see inline.

On Wed, 15 Jul 2009, Xiangsong Cui wrote:

> Good idea.
>
> I have a question about item 5, "Retransmit Message Identifier Option".
> I ever posted a mail on 27 June, but it was ignored. So I copy the mail here:
>

Sorry, we missed that.

> The draft says:
> ----------------------------------------
> 1.  Introduction
>
>   The Proxy Mobile IPv6 protocol [RFC-5213] does not provide the
>   ability for the sender of a signaling message to mark retransmitted
>   messages with a proper tag, so the receiver can differentiate between
>   the original message to a retransmitted message.  This semantic is
>   important for the receiver to determine when to ignore processing a
>   retransmitted packet, or for various other reasons.
> ---------------------------------------------
>
> Is the motive is just to distinguish the original and retransmitted PBU?
>

Yes

>
> I ask this question just because I think it is unnecessary. The reason is:
>
> 1, section 6.1.7 [RFC3775] shows there is a "Sequence #" field in BU
> message, and
>   section 11.8 [RFC3775] says:
>   --------------------------------------------------------
>      Retransmitted Binding Updates MUST use a Sequence Number value
>   greater than that used for the previous transmission of this Binding
>   Update.
>   ----------------------------------------------------
>   So the BU messages are different for their sequence number.
>

We need the ability to distinguish between a original message to a
retransmitted request. Lets take the case, LMA receives a PBU and
is in the midst of processing that request and a second message
arrives. There is nothing in the message which allows the receiver
to identify this message as a retransmit of the current message
that is being processed. If you go with the seq num, or the time
stamp, each message has a different values of those options. What
we need is a tag that allows the LMA to see this marking and associate
with the earlier request. In some interop, there was a case where
the MAG was retransmitting a request and ignoring the response for
an earlier sent request. This could  be avoided, if there are such
semantics for tagging retransmitted messages.

> 2,  section 6.6 [RFC5213] says:
>     -----------------------------------------
>     6.6.  Acquiring Mobile Node's Identifier
>
>   All the network entities in a Proxy Mobile IPv6 domain MUST be able
>   to identify a mobile node, using its MN-Identifier.  This identifier
>   MUST be stable and unique across the Proxy Mobile IPv6 domain.  The
>   mobility entities in the Proxy Mobile IPv6 domain MUST be able to use
>   this identifier in the signaling messages and unambiguously identify
>   a given mobile node.  The following are some of the considerations
>   related to this MN-Identifier.
>   -------------------------------------------
>   In [RFC3775] LMA MUST distinguish the mobile node by the MN-ID.
>   PBU message format also shows there is a sequence # field in PBU
>   message and "Mobile Node Identifier option" is valid.
>
> 3, section 6.9.4 [RFC5213] has specified the rule for Retransmissions and
> Rate Limiting.
>
>
> For these reasons, I believe the LMA can recognize the duplicate PBUs.
> The LMA has been capable of making binding for the first PBU and ignore
> other PBUs for the same mobile node.
>

The rules in 6.9.4 is for addressing the MAG contention issue. Its not
about detecting duplicate messages. Its more of an out-of order delivery
issue.

>
> Do I make any mistakes? and why we need a new extension?
>

These are good questions. The goal is to have a tag on retransmitted
packets. This simple option provides such semantic. Relevant or not,
such semantics are even present in protocols such as GTP.

Regards
Sri

>
> Because I will not go to the meeting, I want to discuss the topic in list
> before the meeting.
>
> Thanks and regards
>
> Xiangsong
>
> =================================================
> ----- Original Message ----- From: <Basavaraj.Patil@nokia.com>
> To: <Basavaraj.Patil@nokia.com>; <netext@ietf.org>
> Sent: Wednesday, July 15, 2009 1:34 AM
> Subject: Re: [netext] Agenda Requests received
>
>
>>
>>  As of 7/14 the chairs have received requests for agenda slots at IETF75.
>>  We would like to encourage WG members to review the I-Ds and provide
>>  feedback on the list prior to the meeting itself.
>>
>>  -Chairs
>> 
>>
>>  Agenda requests received:
>>
>>  1. Runtime LMA Assignment Support for Proxy Mobile IPv6
>>    I-D: draft-korhonen-netext-redirect-02
>>    Jouni Korhonen - 10 Mins
>>
>>  2. Localized Routing
>>    PMIPv6 Localized Routing Problem Statement
>>    I-D: draft-liebsch-netext-pmip6-ro-ps-01.txt
>>    PS and Scope discussion    10 Mins
>>    Solutions        15 Mins
>>    Marco Liebsch et al.
>>
>>    Proxy MIP extension for local routing optimization
>>    I-D: draft-wu-netext-local-ro-02.txt
>>    Behcet Sarikaya    5 Mins
>>
>>  3. Tunnel Negotiation for Proxy Mobile IPv6
>>    I-D: draft-xia-netext-tunnel-negotiation-01.txt
>>    Frank Xia        10 Mins
>>
>>  4. Mobile Node Group Identifier Option:
>>    I-D: draft-gundavelli-netext-mn-groupid-option-01
>>    Sri Gundavelli    10 Mins
>>
>>  5. Retransmit Message Identifier Option:
>>    I-D: draft-gundavelli-netext-pmipv6-retransmit-option-00.txt
>>    Sri Gundavelli    10 Mins
>>
>>  6. Mobility session suspend
>>    I-D: draft-muhanna-netext-mobility-session-suspend-00.txt
>>    Ahmad Muhanna    10 Mins
>>
>>  7. Trace Control Support for Proxy Mobile IPv6
>>    I-D: draft-wang-netext-trace-control-00.txt
>>    Yungui Wang        10 Mins
>>
>>  8. Multihoming extensions for Proxy Mobile IPv6
>>    I-D: draft-bernardos-mif-pmip-00.txt
>>    Telemaco, Pierrick and Carlos    10 Mins
>>
>>  9. 3GPP MN-AR interface
>>    I-D: draft-melia-netext-3gpp-mn-ar-if-00.txt
>>    Telemaco                5 Mins
>>
>>  10. Service Flow Identifier in Proxy Mobile IPv6
>>     I-D: draft-hui-netext-service-flow-identifier-00.txt
>>     Min Hui        10 Mins
>>
>>  11. Connection Identifier for Proxy Mobile IPv6
>>     I-D: draft-wolfner-netext-pmip6-connid-00
>>     Jouni Korhonen    5 Mins
>>
>>  12. Bulk Re-registration for Proxy Mobile IPv6
>>     I-D: draft-premec-netlmm-bulk-re-registration-02
>>     Jouni Korhonen    5 Mins
>>
>>  13. Partial Handoff Support in PMIPv6
>>     I-D: draft-jeyatharan-netext-pmip-partial-handoff-00
>>     Mohana Jeyatharan
>> 
>>
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>
>