RE: [Mip4] RE: Differences between Low Latency Handovers and FMIP v4

[Narayanan Vidya-CVN065 <vidya at motorola.com>]

James,
I'll repeat one of my earlier questions here. What happened to your draft on post-MIT? Wasn't it trying to provide a host-based all-L3 handover optimization? 

Vidya

-----Original Message-----
From: James Kempf [mailto:kempf at docomolabs-usa.com] 
Sent: Tuesday, March 22, 2005 11:40 AM
To: Narayanan Vidya-CVN065; 'Karim El-Malki \\(AL/EAB\\)'; Rajeev Koodli
Cc: mip4 at ietf.org
Subject: Re: [Mip4] RE: Differences between Low Latency Handovers and FMIP v4


I think this whole discussion about L2 triggers and LLH is a red herring. People are taking the wording "L2 trigger" too literally. It doesn't actually have to be a protocol message in the L2 protocol, it just must be indication that handover has occured or will occur. The handover indication doesn't have to include all the L3 information in Table 1 in one L2 message. It can be deduced. For example, using something like CARD or even the RtPrxy messages, the MN can build up a table of AP L2 address to FA address map, and use that. I believe that is what Karim means when he says that FMIP also needs this kind of information. Unless an FMIP MN has some way to know that a handover has occured or will occur, there's no FBU. And unless it has some information about what new subnet the MN is in or will be, it can't put that information into the FBU to tell the old FA where to send packets.

I still believe there's value for FMIPv4, believe it is superior to LLH if host based all-L3 handover optimization is required, and support work on it; however, this whole argument of FMIP v.s. LLH strikes me as being something like the medieval argument about how many angles can dance on the head of a pin. Wireless LAN deployments are increasingly going in the direction of wireless LAN switches (60% of new purchases and practically all upgrades), and these switches already have nonstandardized solutions for "IP Mobility", which, in effect, means tunneling L2 frames in L3 between subnets. Unfortunately, vendors would like to keep it that way, since having a standardized solution means that enterprise customers and service providers would be free to mix and match solutions and less likely to go single supplier. So FMIP is likely to be of limited interest for WLAN deployments going forward. Perhaps 3GPP2 is interested in it? Though they already have their own solution in the A!
 10/A11 interface, which looks strikingly like the solution adopted by the WLAN switch vendors.

Anyway, if this WG was serious about its charter to focus on deployment, it would start up an activity to standardize WLAN switching "IP mobility".

            jak


----- Original Message ----- 
From: "Narayanan Vidya-CVN065" <vidya at motorola.com>
To: "'Karim El-Malki \(AL/EAB\)'" <karim.el-malki at ericsson.com>; "Rajeev Koodli" <rajeev at iprg.nokia.com>
Cc: <mip4 at ietf.org>
Sent: Monday, March 21, 2005 5:56 PM
Subject: RE: [Mip4] RE: Differences between Low Latency Handovers and FMIP v4


> Karim,
> I have a rather stupid question. All the triggers listed in table 1 of 
> LLH
list some L3 parameter or another that needs to be present in the trigger. This suggests to me that any kind of L2 trigger that is needed for LLH (Pre-reg or post-reg) requires the presence of the appropriate parameter listed in the "Parameters" row of the table.
>
> Am I missing something here?
>
> Vidya
>
> -----Original Message-----
> From: mip4-bounces at ietf.org [mailto:mip4-bounces at ietf.org] On Behalf 
> Of
Karim El-Malki \(AL/EAB\)
> Sent: Monday, March 21, 2005 5:20 PM
> To: Rajeev Koodli
> Cc: mip4 at ietf.org
> Subject: RE: [Mip4] RE: Differences between Low Latency Handovers and
FMIPv4
>
>
> >>I understand your point that you took FMIPv6 and applied
> >>it to v4 to make FMIPv4. But that doesn't make it substantially 
> >>different from Low Latency. Your spec does use link-layer triggers 
> >>to be able to send the RtSolPr. An interface coming up in the MN is 
> >>used just the same in Low Latency and is defined as a mobile trigger 
> >>in Low Latency (L2-LU). PRE-REG involves the MN getting such a 
> >>mobile trigger and sending a PrRtSol and receiving a PrRtAdv. What's 
> >>the difference compared to your spec?
> >>
> >>
> >As I explained below (and also itemized in the List below), the 
> >essential difference is that LLH requires L2 to provide L3 
> >information (nFA, MN IP addresses, their MAC addresses etc.) via 
> >various L2-*T type of triggers. This is a Big difference for us since 
> >we do not wish to change L2 to implement fast handovers. Both FMIPv6 
> >and FMIPv4 work without requiring such changes to L2.
>
> That's not correct.
> Let's take the case where the L3 handoff is initiated before L2 
> handoff. Taking WLAN for example, in LLH the MN gets info from L2 
> (e.g.
AP scan) and sends a PrRtSol to get a PrRtAdv containing information of the subnet it may move to. I can't see any change required to L2. Where is the difference compared to what you have described? The only difference is that we definied all "handoff hints" as L2 triggers, just as a result of the AP scan is defined as a mobile trigger. The LLH spec doesn't mandate the presence of all trigger types in all cases. It depends on what the L2 has to offer.
>
> >>The messages are even called the same. Nothing special
> >>or L2-dependent about this L2 trigger. For example PRE-REG
> >>
> >>
> >Well, the essential difference is what requirements LLH imposes on L2 
> >triggers. Table 1 in LLH specifies what information is expected from 
> >L2 triggers including the nFA, MN IP addresses from the various L2-*T 
> >triggers.
>
> LLH can work with different types of L2 triggers (which is very 
> different
from requiring L2 changes) and supports the case you have described in FMIPv4. Table 1 specifies the different types of triggers that LLH can utilise. Note that it includes very simple triggers that work even on WLAN. It is wrong to say that all triggers in Table 1 are required on all L2s for LLH to work.
>
> >>can be applied to WLAN using AP scans. I don't think that the 
> >>difference in packet formats makes it a substantially different spec 
> >>from low latency.  Also, the other case you are considering involves 
> >>an L3 handoff that happens after the MN attaches to the new link. 
> >>This cannot really be considered a "fast" handoff, which would 
> >>instead be where the handoff happens before or in parallel with the 
> >>L2 handoff.
> >>
> >>
> >Perhaps you have missed something.. The FMIP design allows movement 
> >detection and router/FA discovery phases to be done prior to L2 
> >handover. The "reactive" handover we refer to is the one where the 
> >FBU is sent from the new link. But, the MN uses the neighborhood 
> >information via Proxy Router messages to determine movement detection 
> >and router/FA config information of the
> >new subnet. So, your description above is not accurate.
>
> Note that I first addressed the L3-movement-before-L2 (where I am 
> saying
that FMIPv4 is no different from LLH) and then I wrote "the other case you are considering....". Am I incorrect in saying that FMIPv4 also supports the L3-handoff-after-L2-handoff case? I think I had read that case in FMIPv4 (i.e. FBU sent from new link). That's why I had asked about PFANE.
>
> >>This L3-handoff-after-L2-handoff was already covered in the route 
> >>optv4 spec using PFANE. You may have missed the question so I'll 
> >>repeat it: did you consider the PFANE? Why aren't you just reusing 
> >>the PFANE (Previous FA Notification
> >>Extension) work for that scenario?
> >>
> >>
> >Please see above. The key difference with respect to Previous FA 
> >(what used to be Previous AR notification in v6) Notification is that 
> >you don't incur delays due to movement detection and
> >router/FA discovery.
>
> If you are only considering the L3-handoff-before-L2-handoff case then
there are very little differences between FMIPv4 and LLH for the reasons given above.
>
> >So, apart from the independence from L2 to provide L3 information, 
> >the other crucial difference is the decoupling of neighborhood 
> >discovery from the actual handover signaling. This not only reduces 
> >the number of signaling messages
> >during the handover itself, but also makes the reactive fast handovers
> >possible.
>
> Again I can't see the crucial difference from LLH.
> The ND messages are basically the same (even almost called the same):
PrRtSol and PrRtAdv. LLH uses standard MIPv4 naming (Registration Request and Reply) while FMIPv4 achieves the same result but calls this an FBU. Tunnelling between FAs is supported in both specs. LLH furthermore supports anticipated HA updating or "local" HA updating (regional registrations). It seems to me that to make things "faster" one would want to update the local/global HA directly if possible since FA-FA routing can be inefficient in a tree-like network structure compared to updating a local HA. I am curious to understand why you have eliminated that option in FMIPv4 compared to LLH. Measurements performed on FMIPv6+HMIPv6 integration prove that it makes sense to combine local/global HA updating with the FMIP mechanism. /Karim
>
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