Re: AD Evaluation: draft-ietf-dmm-requirements

Le 30/01/2014 18:08, h chan a écrit :
> Alex,
>
> Is the following correct?
>
> Mobility support is needed, for example, when a mobile host or a
> mobile router moves and an application in the mobile host or in a
> host that moves with the router cannot cope with a change in the IP
> address of the mobile node.

Makes better sense, thanks.

But still uses that word 'Mobile Node' which is confusing.  How about this:

> Mobility support is needed, for example, when a Mobile Host or a
> Mobile Router moves and an application in the Mobile Host or in a
> host or router that moves with that Mobile Router cannot cope with a
> change in the IP address of the mobile host or of that Mobile
> Router.

It would be more precise.

But even then, it does not hold, because a Host that moves with the
Mobile Router is not that much influenced by the change of IP address of
that MR.  When the MR changes its IP address, the Host feels it just
like some other interruption in the path to another CN.  These kinds of
interruptions (link up/down) happen often in the fixed networks and yet
Hosts continue to work.

It is possible, for example, to have a Mobile Router move, have NAT (not
mobility management), change IP address, and the Hosts and Routers in
that moving network will continue working ok.

It is also possible for MR to not have NAT, and forward packets with an
address which is not topological correct in that network.  These packets
will reach their destinations (provided there's no ingress filtering),
and the replies will not arrive.  Some applications do not need packets
to return.  One can very well have a vehicle which streams the video of
its front camera to some particular server in the Internet, and change
its IP address at each access.  This does not require Mobile IP nor NAT.

I think it is impossible to stay meaningful in one phrase talking both
Mobile Host and Mobile Router at the same time.  I think we need maybe
two phrases.

> Mobility Support on a Mobile Host is needed, for example, when a
> Mobile Host moves and an arbitrary application in the Mobile Host
> cannot cope with a change in the IP address of that Mobile Host
> [paste socket error message here].
>
> Mobility Support on a Mobile Router is needed, for example, when a
> Mobile Router moves together with a set of Hosts and Routers, and
> arbitrary applications in the Hosts and Routers need to maintain
> their IP address fixed regardless of the change of the IP address of
> the Mobile Router, and the Access Router performs ingress filtering,
> and reachability of these Hosts and Routers at a fixed IP address is
>  necessary.

Alex

>
> H Anthony Chan
>
> -----Original Message----- From: Alexandru Petrescu
> [mailto:[email protected]] Sent: Thursday, January 30,
> 2014 2:13 AM To: h chan; [email protected] Subject: Re: [DMM] AD
> Evaluation: draft-ietf-dmm-requirements
>
> Le 29/01/2014 20:45, h chan a écrit :
>> Alex
>>
>> How about the following:
>>
>> REQ2:  Using and not Using Network-layer mobility support
>>
>> DMM solutions MUST enable network-layer mobility
>>
>> but it MUST be possible to not invoke it.
>>
>> Mobility support is needed, for example,
>>
>> when an application (of a MN or a host in a mobile network of a
>> MR)
> ^a LFN (because just 'host' may be confused with Mobile Host; and
> also because within the moving network there is also one or several
> Routers - not hosts.)
>
>> cannot cope with a change in the
>>
>> IP address of the mobile node when the node moves.
> ^Mobile Host or of the Mobile Router moves (because when the 'node'
> moves it may mean that the 'host' in the moving network moves, and
> that doesn't change its IP address).
>
>> Yet a mobile node can often be stationary,
>>
>> and mobility support can also be provided at other layers.
>>
>> It is then not always necessary to maintain a
>>
>> stable IP address or prefix.
>>
>> Can the text in red be valid for both host or router?
>
> Yes and no.  I agree with it, but I'd prefer the suggested
> modifications.
>
> Alex
>
>>
>> When the node is a router:
>>
>> an application (of a host in a mobile network) may not be able to
>> cope with a change in the IP address of the MR when the MR moves.
>>
>> When the node is a host
>>
>> an application (of a MN) may not be able to cope with a change in
>> the IP address of the MN when the MN moves.
>>
>> H Anthony Chan
>>
>> -----Original Message----- From: Alexandru Petrescu
>> [mailto:[email protected]] Sent: Wednesday, January 29,
>>  2014 12:30 PM To: h chan; [email protected] Subject: Re: [DMM] AD
>> Evaluation: draft-ietf-dmm-requirements
>>
>> Le 28/01/2014 23:33, h chan a écrit :
>>
>>> Let us try to include MR.
>>
>>>
>>
>>> How about the following
>>
>>>
>>
>>> REQ2:  Network-layer mobility support when needed
>>
>>>
>>
>>> DMM solutions MUST enable network-layer
>>
>>> mobility when needed.
>>
>>> Such mobility support is needed, for
>>
>>> example, when an application or a host cannot cope with a
>> change in the
>>
>>> IP address when a node moves.  However, it is not always
>> necessary to maintain a
>>
>>> stable IP address or prefix.
>>
>>>
>>
>>> Here, the node can be a mobile host or a mobile router.
>>
>> I am not sure the term 'node' is agreed to cover both an MH and an
>> MR.
>>
>> I think in all descriptions it would be clearer if we just said MH
>>  when we meant Mobile Host and MR when we meant Mobile Router.
>>
>> Le me paraphrase this text in RFC6275:
>>
>>> This document specifies a protocol that allows nodes to remain
>>
>>> reachable while moving around in the IPv6 Internet.  Without
>>> specific
>>
>>> support for mobility in IPv6 [6], packets destined to a mobile
>>> node
>>
>>> would not be able to reach it while the mobile node is away from
>>> its
>>
>>> home link.
>>
>> There is a clear ambiguity in the 'mobile node' used above. Because
>> if we talk moving networks then often the packets are destined (the
>> contents of the destination address) to a LFN, not to the MR.
>>
>> If that 'node' were a Mobile Router (not a Mobile Host) it
>> completely misses the case when packets are destined to the LFN,
>> which is not an MH nor an MR.
>>
>> The phrase should rather say:
>>
>> 'packets destined to a MH (or to a LFN behind a MR) would not be
>> able
>>
>> to reach it while that MH (or the MR and LFN) is away from its
>> home
>>
>> link.'
>>
>> This kind if expression would be clearer.
>>
>> Alex
>>
>> 'packets destined to a [LFN] or to the Mobile Host, or to the
>> Mobile Router, would not be able to reach it while the Mobile
>> Router is away from its home link'.
>>
>>> A host can be a mobile host or a host in a LFN.
>>
>>> An application can be running on a mobile host or a on a host in
>>> a LFN.
>>
>>> A MR also does not need to maintain stable IP address or prefix
>>> when
>> there are no hosts attached to it or when there are no active
>> applications running in the hosts of its network.
>>
>>>
>>
>>> Any comments/changes/corrections?
>>
>>>
>>
>>> H Anthony Chan
>>
>>>
>>
>>>
>>
>>> -----Original Message-----
>>
>>> From: Alexandru Petrescu [mailto:[email protected]]
>>
>>> Sent: Tuesday, January 28, 2014 1:27 PM
>>
>>> To: h chan; [email protected] <mailto:[email protected]>
>>
>>> Subject: Re: [DMM] AD Evaluation: draft-ietf-dmm-requirements
>>
>>>
>>
>>> Le 28/01/2014 19:58, h chan a écrit :
>>
>>>> Let me try to understand the concern here.
>>
>>>>
>>
>>>> What is new in this requirement is "when needed" in contrast
>>>> to
>>
>>>> providing IP mobility by default.
>>
>>>
>>
>>> First, providing mobility by default is not a black/white
>>> alternative
>> to not providing mobility.
>>
>>>
>>
>>> It is very possible on the same machine to have Mobile IP
>>> enabled for
>> some flows and disabled for others (depending what we call a
>> 'flow').
>>
>>> It is also possible to have Mobile IP and NAT at the same time
>>> on the
>> same Mobile Router.
>>
>>>
>>
>>>> Without this requirement, mobility support may be provided by
>>
>>>> default, which is transparent to higher layers.
>>
>>>
>>
>>> Again, transparency to higher layers means we talk mobility
>> management on a Mobile Host.
>>
>>>
>>
>>> Transparency to higher layers has little meaning if we talk
>>> mobility
>> management provided on a Mobile Router (which is not a Mobile
>> Host).
>>
>>>
>>
>>>> With this requirement, assume there are separate steps in the
>>>> DMM
>>
>>>> solution. 1. A decision is made whether network-layer mobility
>>
>>>> support is needed. 2. When the need is established,
>>>> network-layer
>>
>>>> mobility support is invoked. 3. Then transparent support is
>>>> provided
>>
>>>> and is transparent to layers above IP.
>>
>>>>
>>
>>>> Transparency is clear in step 3 above.
>>
>>>
>>
>>> This looks like a trigger which enables mobility, or other times
>> disables it.
>>
>>>
>>
>>> But one can have a Mobile IP daemon and a NAT run at the same
>>> time on
>> the same machine.  There is no decision in time.
>>
>>>
>>
>>> Some decision happens at packet based on IP destination address.
>>
>>>
>>
>>>> The question however is whether the preceding steps involve
>>>> the
>>
>>>> application, so that one may question whether the entire DMM
>>>> solution
>>
>>>> (with all the steps) as a whole is transparent.
>>
>>>
>>
>>> I agree.  I am not aware of any application which talks to
>>> Mobile IP.
>>
>>> Whenever it is there it is 'transparent'.
>>
>>>
>>
>>>> So the intention of the requirement is that WHEN/AFTER the
>>>> decision
>>
>>>> is made to invoke mobility support, then the mobility support
>>>> is
>>
>>>> transparent to the application. Then we may want to check and
>>>> make
>>
>>>> sure the emphasis of this requirement does mean transparency
>>>> in this
>>
>>>> respect only.
>>
>>>
>>
>>> I disagree.
>>
>>>
>>
>>> As I said above, the word 'transparency' is dubious.  Some times
>>> it
>>>
>> may mean 'non-existent', some times it may mean light goes through
>> it but modified.
>>
>>>
>>
>>> If one wants to continue using it, then one should better
>>> qualify it
>> with 'Mobile Host', with 'Upper Layers' and with 'BSD Socket
>> Interface'.
>>
>>>
>>
>>> Because a Mobile Router doing mobility management in a
>>> transparent
>>>
>> manner on the Mobile Router for the LFN has nothing to do with
>> applications, neither with upper layers.
>>
>>>
>>
>>> Also, a Mobile Router doing NAT and Mobile IP at the same time
>>> is
>> 50%-transparent.
>>
>>>
>>
>>>>
>>
>>>> Original wording:
>>
>>>>
>>
>>>> REQ2:  Transparency to Upper Layers when needed
>>
>>>>
>>
>>>> DMM solutions MUST provide transparent mobility support above
>>>> the IP
>>
>>>> layer when needed.  Such transparency is needed, for example,
>>>> when,
>>
>>> ^on a Mobile Host.
>>
>>>> upon change of point of attachment to the network, an
>>>> application
>>
>>>> flow cannot cope with a change in the IP address.
>>
>>>
>>
>>> (it's not the application flow, it is a socket which some times
>>> may
>>
>>> break [paste here the error from the screen]; the term
>>> 'application
>>
>>> flow' in this context has little meaning)
>>
>>>
>>
>>> (an 'application flow' has no understandable meaning in
>>> practice).
>>
>>>
>>
>>>> However, it is not always necessary to maintain a stable home
>>>> IP
>>
>>>> address or prefix for every application or at all times for a
>>>> mobile
>>
>>>> node.
>>
>>> ^a Mobile Host.
>>
>>>
>>
>>> I agree.
>>
>>>
>>
>>>> I now tend to think the first sentence in this original
>>>> wording may
>>
>>>> steer the emphasis on providing transparent support, which is
>>>> not
>>
>>>> what the motivation and the problems are talking about.
>>
>>>
>>
>>> I agree.
>>
>>>
>>
>>>> The motivation and the problems are talking about when they
>>>> are not
>>
>>>> needed. The emphasis of this requirement therefore is on the
>>
>>>> capability to turn OFF unnecessary mobility support.
>>
>>>
>>
>>> In a sense I agree with the meaning.
>>
>>>
>>
>>> But when trying to turn off or on mobility support the things
>>> are not
>> like if there were a knob on/off, not even like starting/stopping
>> some daemon.  It is a matter of always having the Mobile IP
>> support on, and tweak the routing table with some particular
>> entries, and the firewalling rules to NAT some addresses or not.
>>
>>>
>>
>>>> How about the following
>>
>>>>
>>
>>>> REQ2:  Network-layer mobility support ONLY when needed
>>
>>>
>>
>>> If we understood better when it was needed...
>>
>>>
>>
>>>> DMM solutions MUST NOT provide network-layer mobility support
>>>> when
>>
>>>> NOT needed.
>>
>>>
>>
>>> I would say that Mobile IP MUST always be turned on on a Mobile
>>> Host.
>>
>>>
>>
>>>> (or if you don't like double negatives: (DMM solutions MUST
>>>> provide
>>
>>>> network-layer mobility support ONLY when needed)
>>
>>>
>>
>>> No, I would say to have it always on.  If some applications
>>> don't
>> want it then dont use it; realize that by inserting routing table
>> entries.
>>
>>>
>>
>>> One may wonder when some applications dont want it.  One answer
>>> is
>>>
>> when some applications prefer to not go through the HA in order to
>>  take advantage of the 4G pure speed.  When? For example if the HA
>>  link is too slow compared to 4G. (remark this is not the same as
>> saying that the triangular route is longer than straight, because
>> that is always true).
>>
>>>
>>
>>> This is not a request for Route Optimization.  It is an
>>> invitation to
>> analyze in deeper detail the application needs.
>>
>>>
>>
>>> One may have an application start via the HA (offer reachability)
>>> and
>> continue straight, w/o HA.  It's the same application.
>>
>>>
>>
>>> Consider a video-call like appli: you want to be reachable always
>>> at
>> the same IP address (through HA) but once the session is ongoing
>> you may not want to use it through HA if no handover in sight.
>>
>>>
>>
>>> Something like that.
>>
>>>
>>
>>> These things could be further refined if we really went into
>>> detail
>>>
>> and understood what are the needs of applications, the distinctions
>> MH-MR, etc.
>>
>>>
>>
>>>> Such transparent mobility support above the IP layer is needed,
>>>> for
>>
>>>> example, when, upon change of point of attachment to the
>>>> network, an
>>
>>>> application flow cannot cope with a change in the IP address.
>>
>>>> However, it is not always necessary to maintain a stable home
>>>> IP
>>
>>>> address or prefix for every application or at all times for a
>>>> mobile
>>
>>>> node.
>>
>>>
>>
>>> A Mobile Host never maintains a stable prefix, only a stable
>>> address.
>>
>>>
>>
>>> A Mobile Router may maintain a stable address (its HoA) and may
>> maintain a stable prefix  (its MNP).  It could also just maintain
>> stable just its MNP, but not its HoA; and vice-versa.  Is that
>> mobility?
>>
>>>
>>
>>> For each of these there is an application :-)
>>
>>>
>>
>>> Alex
>>
>>>
>>
>>>>
>>
>>>> Any comments/changes/corrections?
>>
>>>>
>>
>>>> H Anthony Chan
>>
>>>>
>>
>>>> -----Original Message----- From: dmm
>>>> [mailto:[email protected]] On
>>
>>>> Behalf Of Alexandru Petrescu Sent: Tuesday, January 28, 2014
>>>> 8:43 AM
>>
>>>> To: [email protected] <mailto:[email protected]> Subject: Re: [DMM] AD
>>>> Evaluation:
>>
>>>> draft-ietf-dmm-requirements
>>
>>>>
>>
>>>> Le 28/01/2014 02:45, h chan a écrit :
>>
>>>>> I will drop "related"
>>
>>>>>
>>
>>>>> Regarding the following
>>
>>>>>
>>
>>>>> 5. Section 5: - I am a little confused by REQ2.  It says
>>>>> that a DMM
>>
>>>>> solution should be transparent to the applications.
>>
>>>>
>>
>>>> This remark is typically true when we talk Mobile IP on a
>>>> Mobile Host
>>
>>>> and an application like firefox runs above a BSD Socket
>>>> interface.
>>
>>>>
>>
>>>>
>>
>>>>> However, the motivation talks about identifying applications
>>>>>  that do
>>
>>>>> (or do not) need mobility support from the network layer.
>>>>> That
>>
>>>>> doesn't sound transparent to me.  Am I reading this
>>>>> incorrectly?
>>
>>>>>
>>
>>>>> It appears that unless the network can find out whether the
>>
>>>>> application has need of such support, the application indeed
>>>>>  may
>>
>>>>> need to invoke mobility support or has to convey its need to
>>>>>  the
>> network.
>>
>>>>>
>>
>>>>> The emphasis of requirement is on "when needed." So, I think
>>>>> it is
>>
>>>>> better to drop the word "transparent" as follows:
>>
>>>>>
>>
>>>>> REQ2:  Mobility support when needed
>>
>>>>>
>>
>>>>> DMM solutions MUST provide mobility support to above the IP
>>>>> layer
>>
>>>>> when needed.  Such support is needed, for example, when, upon
>>>>> change
>>
>>>>> of point of attachment to the network, an application flow
>>>>> cannot
>>
>>>>> cope with a change in the IP address.  However, it is not
>>>>> always
>>
>>>>> necessary to maintain a stable home IP address or prefix for
>>>>>  every
>>
>>>>> application or at all times for a mobile node.
>>
>>>>>
>>
>>>>> Motivation: The motivation of this requirement is to enable
>>>>> more
>>
>>>>> efficient routing and more efficient use of network resources
>>>>> by
>>
>>>>> selecting an IP address or prefix according to whether
>>>>> mobility
>>
>>>>> support is needed and by not maintaining context at the
>>>>> mobility
>>
>>>>> anchor when there is no such need.
>>
>>>>
>>
>>>> Whenever we discuss this 'transparency' paragraph I have again
>>>>  the
>>
>>>> same comments.
>>
>>>>
>>
>>>> First, I am not sure DMM is only about Mobile Hosts, or about
>>>> Mobile
>>
>>>> Routers as well.
>>
>>>>
>>
>>>> Because, if we talk Mobile Routers, then rarely an application
>>>>  runs
>>
>>>> directly on it.  Most applications would run on LFN.
>>
>>>>
>>
>>>> Transparency?
>>
>>>>
>>
>>>> If the applications run on the LFN, the change of the
>>>> attachment of
>>
>>>> the MR is 'transparent' to them, regardless whether or not MR
>>>> does
>>
>>>> something to maintain stability of that address (Mobile IP,
>>>> other).
>>
>>>>
>>
>>>> Second, this transparency may depend on the direction, or more
>>
>>>> complex 'shape' of the application flows.  Some IP flows of
>>>> some
>>
>>>> applications have very complex 'shapes', with various sets of
>>>> IP src
>>
>>>> and dst, and triangular or HA-less shapes.
>>
>>>>
>>
>>>> Take for example a video-call.  The session establishment
>>>> through an
>>
>>>> intermediary and behind NAT is followed by the ongoing 4 flows
>>>>  (2
>>
>>>> audio 2 video)... they all take different paths... each may
>>>> need or
>>
>>>> not need to go through the HA, and each has distinct behaviours
>>>> when
>>
>>>> the IP address changes, hence each would have a distinct
>>
>>>> 'transparency' requirement.  Is this _one_ application?
>>
>>>>
>>
>>>> Alex
>>
>>>>
>>
>>>>>
>>
>>>>> H Anthony Chan
>>
>>>>>
>>
>>>>> -----Original Message----- From: dmm
>>>>> [mailto:[email protected]]
>>
>>>>> On Behalf Of Brian Haberman Sent: Monday, January 27, 2014
>>>>> 7:20 AM
>>
>>>>> To: h chan; [email protected]
>> <mailto:[email protected]>;
>>
>>>>> [email protected] <mailto:[email protected]>; Peter McCann Subject: Re:
>>>>> [DMM]
>> AD Evaluation:
>>
>>>>> draft-ietf-dmm-requirements
>>
>>>>>
>>
>>>>>
>>
>>>>>
>>
>>>>> On 1/24/14 7:38 PM, h chan wrote:
>>
>>>>>> 4. Section 4: - I am not sure that it benefits the document
>>>>>> to
>>
>>>>>> label
>>
>>>>>> PS6 and PS7 as related.  Those issues are problematic on
>>>>>> their own.
>>
>>>>>> If you remove the "(related problem)" label from them, make
>>>>>> sure
>>
>>>>>> that REQ2 is updated to remove mention of "related
>>>>>> problem".
>>
>>>>>>
>>
>>>>>> The intention of the name "related problems" was not to
>>>>>> suggest
>>
>>>>>> they are less problematic, but rather to distinguish them
>>>>>> from the
>>
>>>>>> other problems directly on mobility management. Although
>>>>>> these
>>
>>>>>> problems are not directly on mobility management, the DMM
>>>>>> solutions
>>
>>>>>> can solve these additional problems. They are therefore
>>>>>> included.
>>
>>>>>> So, as long as this section is not to be interpreted as
>>>>>> limited to
>>
>>>>>> problems directly on mobility management, we can drop the
>>>>>> word
>> "related."
>>
>>>>>>
>>
>>>>>
>>
>>>>> I will leave it to the authors/WG, but I don't see a benefit
>>>>> to the
>>
>>>>> "related" tag.
>>
>>>>>
>>
>>>>> Regards, Brian
>>
>>>>>
>>
>>>>> _______________________________________________ dmm mailing
>>>>> list
>>
>>>>> [email protected] <mailto:[email protected]>
>> https://www.ietf.org/mailman/listinfo/dmm
>>
>>>>>
>>
>>>>>
>>
>>>>
>>
>>>>
>>
>>>> _______________________________________________ dmm mailing
>>>> list
>>
>>>> [email protected] <mailto:[email protected]>
>> https://www.ietf.org/mailman/listinfo/dmm
>>
>>>>
>>
>>>>
>>
>>>
>>
>>>
>>
>>>
>>
>>>
>>
>
>
>
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