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

From: Narayanan Vidya-CVN065 <[email-masked]>
Date: Mon, 21 Mar 2005 19:56:36 -0600

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: [email-masked] [mailto:[email-masked]] On Behalf Of Karim El-Malki \(AL/EAB\)
Sent: Monday, March 21, 2005 5:20 PM
To: Rajeev Koodli 
Cc: [email-masked]
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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Mip4 mailing list: [email-masked]
    Web interface: https://www1.ietf.org/mailman/listinfo/mip4
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Supplemental site: http://www.mip4.org/

---

From: "James Kempf" <[email-masked]>
Date: Tue, 22 Mar 2005 09:40:28 -0800

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 A10/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" <[email-masked]>
To: "'Karim El-Malki \(AL/EAB\)'" <[email-masked]>; "Rajeev
Koodli" <[email-masked]>
Cc: <[email-masked]>
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.
> 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.
> 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.
> 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.
> 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.
> 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

---

From: Rajeev Koodli <[email-masked]>
Date: Tue, 22 Mar 2005 11:40:32 -0800

Hi Jim,

>host based all-L3 handover optimization is required, and support work on it;
okay.

>pin. Wireless LAN deployments are increasingly going in the direction of
:-)

>which, in effect, means tunneling L2 frames in L3 between subnets.
Looking forward, subnet mobility is crucial for scale and for deployment 
easy.

>going forward. Perhaps 3GPP2 is interested in it? Though they already have
On the contrary, wouldn't you expect the enterprises to start demanding 
interoperability
between boxes? If vendors have "holds" on enterprises for their boxes 
alone, that does not
sound like a way going forward.

>would start up an activity to standardize WLAN switching "IP mobility".
Doesn't this mean tunneling?  A switch tunneling an L2 frame in L3 
sounds sub-optimal
since it needs to "go back" through the router to reach the IP network, 
and eventually the
destination router and the switch. Anyway, why is there a need for 
standardization here?

-Rajeev

>>From: [email-masked] [mailto:[email-masked]] On Behalf Of
>>    
>>
>Karim El-Malki \(AL/EAB\)
>  
>
>>Subject: RE: [Mip4] RE: Differences between Low Latency Handovers and
>>    
>>
>FMIPv4
>  
>
>>    
>>

---

From: Henrik Levkowetz <[email-masked]>
Date: Tue, 22 Mar 2005 20:52:05 +0100

on 2005-03-22 6:40 pm James Kempf said the following:

<snip a lot of stuff on which I basically agree>

> would start up an activity to standardize WLAN switching "IP mobility".

Interesting point.  

If we do propose to take this up in the new charter proposal, do we
have people who would be willing to spend some time and energy on
this?

	Henrik

---

From: "James Kempf" <[email-masked]>
Date: Tue, 22 Mar 2005 11:58:40 -0800

(raised hand).

            jak

----- Original Message ----- 
From: "Henrik Levkowetz" <[email-masked]>
To: "James Kempf" <[email-masked]>
Cc: <[email-masked]>
Sent: Tuesday, March 22, 2005 11:52 AM
Subject: Re: [Mip4] RE: Differences between Low Latency Handovers and FMIP
v4

---

From: "James Kempf" <[email-masked]>
Date: Tue, 22 Mar 2005 12:06:31 -0800

Hi Rajeev,

> sound like a way going forward.

Well, one would hope.

> destination router and the switch. Anyway, why is there a need for

There's a bit  more of a dogleg on the routing than on something like FMIP.
With FMIP, the dogleg is from the crossover aggregation router between the
previous and new ARs and the previous and new ARs. With the WLAN switches,
there's that and between the switch and previous AR.

As for what's to standardize, essentially, these protocols work like
Postreg. So there would need to be some agreement about the inter-switch
signaling to set up the tunnel, and the actual tunnel type. I don't know
offhand what kind of tunnel is used, I suspect each switch might use a
different tunnel type.

            jak

---

From: Rajeev Koodli <[email-masked]>
Date: Tue, 22 Mar 2005 12:07:42 -0800

Hello Henrik,

I believe that we should have a single solution for subnet
mobility. And, you may be aware that MIPSHOP is
considering "AAA Keys for Handover" as one of the
mechanisms to establish MN - AR security association.
We could get the keys for IPv4 as well.
In addition, there was discussion about extending the "SEND-based
key derivation for handover" for IPv4 as well. (Disclaimer: James and
myself are co-authors on this draft).

So, we could have a PS solution for IPv4 subnet mobility, just
as MIPSHOP is attempting to define one.

My 2 cents..

-Rajeev

---

From: Rajeev Koodli <[email-masked]>
Date: Tue, 22 Mar 2005 12:13:04 -0800

>offhand what kind of tunnel is used, I suspect each switch might use a
Okay. Why do we need to standardize inter-switch communication? Are you
considering the switch also as a L3 device from a MIP MN perspective?

-Rajeev

---

From: Henrik Levkowetz <[email-masked]>
Date: Tue, 22 Mar 2005 21:28:35 +0100

Ok. So I see there is some interest, and somebody willing to do work
in the area.  I will have to check with Gab and the ADs to make sure
we agree on where the work should be done, if we take it up.

	Henrik

---

From: "James Kempf" <[email-masked]>
Date: Tue, 22 Mar 2005 12:45:51 -0800

> considering the switch also as a L3 device from a MIP MN perspective?

The fact that handover optimization was done at a switch rather than at the
router had mainly to do with practical considerations about how to bring a
product out best, I suspect. It allows one to install switches below one's
existing routers, without having to modify the routers. Thus, an easier
sale.

>From the MIP perspective, I think the FA is the place to define the
function. But I'm not sure, though now that I think of it, whether the
switch vendors would even be interested in working in MIP4. Most of their
efforts are focussed on CAPWAP, and I think they might rather want to have
the handover optimization functionality defined at the Access Controller
(AC, a functional entity that controls the access points), if they want it
at all (I think they might agree from a technical standpoint that it would
be nice).

Having the switch vendors involved is necessary, otherwise nobody will
implement it, just as has been the case with all the other proposed handover
optimization technologies up until now.

            jak