Re: [Mip4] Differences between Low Latency Handovers and FMIPv4
"Qiang Zhang/Aber" <qzhang@aber-networks.net> Fri, 18 March 2005 20:09 UTC
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From: Qiang Zhang/Aber <qzhang@aber-networks.net>
To: "Karim El-Malki (AL/EAB)" <karim.el-malki@ericsson.com>, "Charles E.Perkins " <charliep@iprg.nokia.com>, Mobile IPv4 Mailing List <mip4@ietf.org>
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Subject: Re: [Mip4] Differences between Low Latency Handovers and FMIPv4
Date: Fri, 18 Mar 2005 15:05:49 -0500
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Cc: Rajeev Koodli <rajeev.koodli@nokia.com>
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Hello, All >From an implementor point of view, since there is already a llh draft in experimental standard, it will be interesting to debate on the technical pros/cons between, or if they are having a lot similarity, can those be combined? http://www.ietf.org/internet-drafts/draft-ietf-mobileip-lowlatency-handoffs-v4-09.txt and http://www.ietf.org/internet-drafts/draft-koodli-fmipv4-00.txt Thanks Qiang ----- Original Message ----- From: "Karim El-Malki (AL/EAB)" <karim.el-malki@ericsson.com> To: "Charles E.Perkins " <charliep@iprg.nokia.com>; "Mobile IPv4 Mailing List " <mip4@ietf.org> Cc: "Rajeev Koodli" <rajeev.koodli@nokia.com> Sent: Friday, March 18, 2005 9:11 AM Subject: RE: [Mip4] Differences between Low Latency Handovers and FMIPv4 Following Henrik's note I'll expand on the technical issues. As I wrote in my previous email I cannot quite see the major difference between these drafts. Your new draft considers link-layer triggers just as FMIPv6 and Low Latency in order to improve performance. You describe AP scanning etc. which is not different from the existing approach. An IP interface becoming available is just a way of implementing a mobile trigger right? You describe tunnelling between FAs which is covered by the pre-reg/post-reg. combination scenario in Low Latency. One other mechanism was however pointed out a while back: sending the mobile registration to create the FA-FA tunnel AFTER L2 handoff. I assume that this is the mechanism you want to add since the advantages you note below are applicable to that scenario? This wasn't covered in low latency because it was covered by the PFANE mechanism in route optv4. Have you considered PFANE? I think the rest is covered already by pre-reg, post-reg and the combined mechanism. /Karim -----Original Message----- From: mip4-bounces@ietf.org To: Mobile IPv4 Mailing List Cc: Rajeev Koodli Sent: 2005-03-18 00:47 Subject: [Mip4] Differences between Low Latency Handovers and FMIPv4 Hello folks, FMIPv4 is a straightforward adaptation of the Fast Handovers for Mobile IPv6 specification. The intention is to utilize the same design for IPv4 networks, but that requires different packet formats. We would like the [mip4] WG to standardize these packet formats. Both the FMIPv6 and FMIPv4 draft mentioned here have been implemented and offer the performance needed for real-time handovers. Below, we offer a list of some differences between our FMIPv4 spec and the previously published Low Latency Handovers ("LLH") specification for Mobile IPv4. 1) We believe that FMIPv4 will avoid the pitfalls documented in the paper from Kempf et al. which were described quite a while back. 2) Tight coupling to L2 triggers: The entire LLH process is very tightly coupled to L2 triggers, to the extent that the protocol does not work without such triggers. In contrast, FMIPv4 can make use of such triggers, but entire protocol operation does not depend on the availability and tight coupling of L2 triggers. For instance, the standard Linux function ll_handoff() indicates to IP layer that an interface has become available. FMIPv4 code for FBU from the new link can be invoked within ll_handoff(). 3) Changes to L2 triggers: In addition to the reliance on L2 triggers in LLH, the triggers themselves need to be modified to include parameters such as new FA IP address, MN IP address, their MAC addresses etc. within the triggers themselves. This would require changes to whatever L2 triggers are available on _all_ links where such triggers are supported. This is not at all required for FMIPv4 operation. Nor does the spec recommend such changes. 4) The number of messages exchanged during handover: 4.a) Pre-reg LLH: All the messages between the MN and FAs are exchanged once the trigger event occurs. This includes two proxy router messages and a registration request and possibly registration reply on the old link. In FMIPv4, a single message (FBU) is sent once the decision to undergo handover is made. The MN need not stay on the old link once FBU is sent. 4.b) Post-reg LLH: No messages are exchanged between the MN and FA. However, since the MN does not have means to change the default router, it will continue to send packets from the new link to the oFA's MAC address, which should be dropped by the IP stack. And, consideration (3) above applies; the triggers on oFA and nFA must contain MN's IP addresses, necessitating changes to L2 where the protocol might be useful. Plus, such a mode "defers" MIPv4 operation, which is additional code on the MN. FMIPv4 works without imposing restrictions on when MIPv4 protocol messages need to be carried out. 5) Changes to MIPv4 operation: The MN changes its default access router once the registration reply is received in pre-reg LLH even if the MN is still on the oFA. So, packet forwarding needs to be carefully constructed. (In post-reg LLH on the other hand, the MN does not change its default router at all, even though it is on the nFA. This leads to different set of additional considerations). In FMIPv4, no changes to default router processing are needed. That is, the MN is free to perform and process agent/router advertisements just as any normal (mobile) node would. 6) Protocol design: The FMIPv4 protocol clearly separates movement detection, IP address and nFA configuration, and registration request phases. None of these phases is in the critical time path. The only message that is on the criticial path is the FBU message. For movement detection and IP/nFA configuration, the FMIPv4 protocol uses the Proxy Router messages, which are exchanged ahead of handover, as opposed to intitiating the handover in LLH. There are quite a few other differences to list here. In summary, Rajeev and I believe that the differences are important enough to consider a separate spec of choice to implementors. It is especially appealing to those considering FMIPv6 as well. Regards, Charlie P. -- Mip4 mailing list: Mip4@ietf.org Web interface: https://www1.ietf.org/mailman/listinfo/mip4 Charter page: http://www.ietf.org/html.charters/mip4-charter.html Supplemental site: http://www.mip4.org/ -- Mip4 mailing list: Mip4@ietf.org Web interface: https://www1.ietf.org/mailman/listinfo/mip4 Charter page: http://www.ietf.org/html.charters/mip4-charter.html Supplemental site: http://www.mip4.org/ -- Mip4 mailing list: Mip4@ietf.org Web interface: https://www1.ietf.org/mailman/listinfo/mip4 Charter page: http://www.ietf.org/html.charters/mip4-charter.html Supplemental site: http://www.mip4.org/
- [Mip4] Differences between Low Latency Handovers … Charles E.Perkins
- RE: [Mip4] Differences between Low Latency Handov… Karim El-Malki (AL/EAB)
- Re: [Mip4] Differences between Low Latency Handov… Henrik Levkowetz
- RE: [Mip4] Differences between Low Latency Handov… Karim El-Malki (AL/EAB)
- Re: [Mip4] Differences between Low Latency Handov… James Kempf
- Re: [Mip4] Differences between Low Latency Handov… Qiang Zhang/Aber
- Re: [Mip4] Differences between Low Latency Handov… Henrik Levkowetz
- [Mip4] Re: Differences between Low Latency Handov… Rajeev Koodli
- [Mip4] RE: Differences between Low Latency Handov… Karim El-Malki (AL/EAB)
- Re: [Mip4] RE: Differences between Low Latency Ha… Rajeev Koodli
- RE: [Mip4] RE: Differences between Low Latency Ha… Karim El-Malki (AL/EAB)
- RE: [Mip4] RE: Differences between Low Latency Ha… Karim El-Malki (AL/EAB)
- RE: [Mip4] RE: Differences between Low Latency Ha… Karim El-Malki (AL/EAB)
- Re: [Mip4] RE: Differences between Low Latency Ha… Rajeev Koodli