Hello, I think that SIP is a good example to clarify the idea. SIP can support mobility for SIP-based sessions at the application layer. The sessions that are initiated by SIP signaling (the INVITE procedure) can refuse IP mobility support at the network layer (if the operator prefers this choice and configures it). Then, mobility will be handled by SIP signaling (re-INVITE) at the application layer.
Some people may not agree to apply this, but it's still a simple and valid example. Best regards, Hassan On Wed, Jan 29, 2014 at 3:26 PM, Brian Haberman <[email protected]>wrote: > Anthony, > Does this requirement also include a way for the application (or > transport protocol) to request/refuse mobility support? The "when > needed" implies some type of knowledge that is either manually > configured or signaled from the upper layer. > > Regards, > Brian > > On 1/28/14 5:33 PM, h chan wrote: > > 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. > > 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] > > 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] 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]; > >>> [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] https://www.ietf.org/mailman/listinfo/dmm > >>> > >>> > >> > >> > >> _______________________________________________ dmm mailing list > >> [email protected] https://www.ietf.org/mailman/listinfo/dmm > >> > >> > > > > > > _______________________________________________ > > dmm mailing list > > [email protected] > > https://www.ietf.org/mailman/listinfo/dmm > > > > > _______________________________________________ > dmm mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/dmm > >
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