| DMM | H. Chan, Ed. |
| Internet-Draft | X. Wei |
| Intended status: Informational | Huawei Technologies |
| Expires: June 18, 2017 | J. Lee |
| Sangmyung University | |
| S. Jeon | |
| Sungkyunkwan University | |
| A. Petrescu | |
| CEA, LIST | |
| F. Templin | |
| Boeing Research and Technology | |
| December 15, 2016 |
Distributed Mobility Anchoring
draft-ietf-dmm-distributed-mobility-anchoring-03
This document defines distributed mobility anchoring in terms of the different configurations, operations and parameters of mobility functions to provide different IP mobility support for the diverse mobility needs in 5G Wireless and beyond. A network or network slice may be configured with distributed mobility anchoring functions according to the needs of mobility support. In the distributed mobility anchoring environment, multiple anchors are available for mid-session switching of an IP prefix anchor. To start a new flow or to handle a flow not requiring IP session continuity as a mobile node moves to a new network, the flow can be started or re-started using a new IP prefix which is allocated from and is therefore anchored to the new network. For a flow requiring IP session continuity, the anchoring of the prior IP prefix may be moved to the new network. The mobility functions and their operations and parameters are general for different configurations. The mobility signaling may be between anchors and nodes in the network in a network-based mobility solution. It may also be between the anchors and the mobile node in a host-based solution. The mobile node may be a host, but may also be a router carrying a network requiring network mobility support.
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Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved.
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A key requirement in distributed mobility management [RFC7333] is to enable traffic to avoid traversing a single mobility anchor far from an optimal route. Distributed mobility management solutions do not rely on a centrally deployed mobility anchor in the data plane [Paper-Distributed.Mobility]. As such, the traffic of a flow SHOULD be able to change from traversing one mobility anchor to traversing another mobility anchor as a mobile node (MN) moves, or when changing operation and management requirements call for mobility anchor switching, thus avoiding non-optimal routes.
Companion distributed mobility management documents are already addressing the architecture and deployment [I-D.ietf-dmm-deployment-models], source address selection [I-D.ietf-dmm-ondemand-mobility], and control-plane data-plane signaling [I-D.ietf-dmm-fpc-cpdp]. Yet in 5G Wireless and beyond, the mobility requirements are diverse, and IP mobility support is no longer by default with a one-size-fit-all solution. In different networks or network slices, different kinds of mobility support are possible depending on the needs. It may not always be obvious on how to best configure and use only the needed mobility functions to provide the specific mobility support. This draft defines different configurations, functional operations and parameters for distributed mobility anchoring and explains how to use them to make the route changes to avoid unnecessarily long routes.
Distributed mobility anchoring employs multiple anchors in the data plane. In general, control plane functions may be separate from data plane functions and be centralized but may also be co-located with the data plane functions at the distributed anchors. Different configurations of distributed mobility anchoring are described in Section 3.1. For instance, the configurations for network-based mobility support in a flat network, for network-based mobility support in a hierarchical network, for host-based mobility support, and for NEtwork MObility (NEMO) basic support are described respectively in Section 3.1.1, Section 3.1.2, Section 3.1.3 and Section 3.1.4. Required operations and parameters for distributed mobility anchoring are presented in Section 3.2. For instance, location management is described in Section 3.2.1, forwarding management is described in Section 3.2.2.
An MN attached to an access router of a network or network slice may be allocated an IP prefix which is anchored to that router. It may then use an IP address configured from this prefix as the source IP address to run a flow with its correspondent node (CN). When there are multiple mobility anchors, an address selection for a given flow is first required before the flow is initiated. Using an anchor in an MN's network of attachment has the advantage that the packets can simply be forwarded according to the forwarding table. Although the anchor is in the MN's network of attachment when the flow was initiated, the MN may later move to another network, so that the IP no longer belongs to the current network of attachment of the MN.
Whether the flow needs IP session continuity will determine how to ensure that the IP address of the flow will be anchored to the new network of attachment. If the ongoing IP flow can cope with an IP prefix/address change, the flow can be reinitiated with a new IP address anchored in the new network as shown in Section 4.1. On the other hand, if the ongoing IP flow cannot cope with such change, mobility support is needed as shown in Section 4.2. A network or network slice supporting a mix of flows requiring and not requiring IP mobility support will need to distinguish these flows. The guidelines for such network or network slice are described in Section 4.1.1. The general guidelines for such network or network slice to provide IP mobility support are described in Section 4.2.1.
Specifically, IP mobility support can be provided by relocating the anchoring of the IP prefix/address of the flow from the home network of the flow to the new network of attachment. The basic case may be with network-based mobility for a flat network configuration described in Section 5.1 with the guidelines described in Section 5.1.1. This case is discussed further with a centralized control plane in Section 5.2 with additional guidelines described in Section 5.2.1. A level of hierarchy of nodes may then be added to the network configuration. Mobility involving change in the Data Plane Node (DPN) without changing the Data Plane Anchor (DPA) is described in Section 5.3 with additional guidelines described in Section 5.3.1 Mobility involving change in the DPN without changing the DPA is described in Section 5.4 with additional guidelines described in Section 5.4.1
The key words "MUST", "MUST NOT", "GLUIRED", "SHALL","SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
All general mobility-related terms and their acronyms used in this document are to be interpreted as defined in the Mobile IPv6 (MIPv6) base specification [RFC6275], the Proxy Mobile IPv6 (PMIPv6) specification [RFC5213], the "Mobility Related Terminologies" [RFC3753], and the DMM current practices and gap analysis [RFC7429]. These include terms such as mobile node (MN), correspondent node (CN), home agent (HA), home address (HoA), care-of-address (CoA), local mobility anchor (LMA), and mobile access gateway (MAG).
In addition, this document uses the following terms:
The mobility functions may be implemented in different configurations of distributed mobility anchoring in architectures separating the control and data planes. The separation described in [I-D.ietf-dmm-deployment-models] has defined the home control plane anchor (Home-CPA), home data plane anchor (Home-DPA), access control plane node (Access-CPN), and access data plane node (Access-DPN), which are respectively abbreviated as CPA, DPA, CPN, and DPN here.
Different networks or different network slices may have different configurations in distributed mobility anchoring.
The configurations also differ depending on the desired mobility supports: network-based mobility support for a flat network in Section 3.1.1, network-based mobility support for a hierarchical network in Section 3.1.2, host-based mobility support in Section 3.1.3, and NEtwork MObility (NEMO) based support in Section 3.1.4.
Figure 1 shows two different configurations of network-based mobility management for a flat network.
(a) (b)
+-----+
|LMs |
+-----+
+------------+ +------------+
|CPA: | |CPA: |
|FM-CP, LM | |FM-CP, LMc |
+------------+ +------------+
+------------+ +------------+ +------------+ +------------+
|DPA(IPa1): | |DPA(IPa2): | |DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | |anchors IP2 | ... |anchors IP1 | |anchors IP2 | ...
|FM-DP | |FM-DP | |FM-DP | |FM-DP |
+------------+ +------------+ +------------+ +------------+
+------------+ +------------+
|MN(IP1) | |MN(IP1) |
|flow(IP1,..)| |flow(IP1,..)|
+------------+ +------------+
Figure 1. Configurations of network-based mobility management for a flat network (a) FM-CP and LM at CPA, FM-DP at DPA; (b) Separate LMs, FM-CP and LMc at CPA, FM-DP at DPA.
Figure 1 also shows a distributed mobility anchoring environment with multiple instances of the DPA.
There is an FM-DP function at each of the distributed DPA.
The control plane may either be distributed (not shown) or centralized. When the CPA co-locates with the distributed DPA there will be multiple instances of the co-located CPA and DPA (not shown).
There is an FM-CP function at the CPA.
An MN is allocated an IP prefix/address IP1 which is anchored to the DPA with the IP prefix/address IPa1. The MN uses IP1 to communicate with a CN not shown in the figure. The flow of this communication session is shown as flow(IP1, ...) which uses IP1 and other parameters.
In Figure 1(a), LM and FM-CP co-locate at CPA.
Then LM may be distributed or centralized according to whether the CPA is distributed (not shown) or centralized.
Figure 1(b) differs from Figure 1(a) in that the LM function is split into a server LMs and a client LMc.
LMc and FM-CP co-locate at the CPA.
The LMs may be centralized whereas the LMc may be distributed or centralized according to whether the CPA is distributed (not shown) or centralized.
Figure 2 shows two different configurations of network-based mobility management for a hierarchical network.
(a)
+------------+
|CPA: |
|FM-CP, LMs |
+------------+
+------------+ +------------+
|DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | |anchors IP2 | ...
|FM-DP | |FM-DP |
+------------+ +------------+
+------------+
|CPN: |
|FM-CP, LMc |
+------------+
+------------+ +------------+ +------------+ +------------+
|DPN(IPn11): | |DPN(IPn12): | |DPN(IPn21): | |DPN(IPn22) |
|FM-DP | |FM-DP | ... |FM-DP | |FM-DP | ...
+------------+ +------------+ +------------+ +------------+
+------------+ +------------+
|MN(IP1) | |MN(IP2) |
|flow(IP1,..)| |flow(IP2,..)|
+------------+ +------------+
Figure 2(a). Configurations of network-based mobility management for a hierarchical network with FM-CP and LMs at CPA, FM-DP at DPA; FM-CP and LMc at CPN, FM-DP at DPN.
(b)
+-----+
|LMs |
+-----+
+------------+
|CPA: |
|FM-CP, LMp |
+------------+
+------------+ +------------+
|DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | |anchors IP2 | ...
|FM-DP | |FM-DP |
+------------+ +------------+
+------------+
|CPN: |
|FM-CP, LMc |
+------------+
+------------+ +------------+ +------------+ +------------+
|DPN(IPn11): | |DPN(IPn12): | |DPN(IPn21): | |DPN(IPn22) |
|FM-DP | |FM-DP | ... |FM-DP | |FM-DP | ...
+------------+ +------------+ +------------+ +------------+
+------------+ +------------+
|MN(IP1) | |MN(IP2) |
|flow(IP1,..)| |flow(IP2,..)|
+------------+ +------------+
Figure 2(b). Configurations of network-based mobility management for a hierarchical network with separate LMs, FM-CP and LMp at CPA, FM-DP at DPA; FM-CP and LMc at CPN, FM-DP at DPN.
Figures 2 also shows a distributed mobility anchoring environment with multiple instances of the DPA.
In the hierarchy, there may be multiple DPN's for each DPA.
There is FM-DP at each of the distributed DPA and at each of the distributed DPN.
The control plane may either be distributed (not shown) or centralized.
When the CPA co-locates with the distributed DPA there will be multiple instances of the co-located CPA and DPA (not shown).
When the CPN co-locates with the distributed DPN there will be multiple instances of the co-located CPN and DPN (not shown).
There is FM-CP function at the CPA and at the CPN.
MN is allocated an IP prefix/address IP1 which is anchored to the DPA with the IP prefix/address IPa1. It is using IP1 to communicate with a correspondent node (CN) not shown in the figure. The flow of this communication session is shown as flow(IP1, ...) which uses IP1 and other parameters.
In Figure 2(a), LMs and FM-CP are at the CPA. In addition, there are FM-CP and LMc at the CPN.
LMs may be distributed or centralized according to whether the CPA is distributed or centralized. The CPA may co-locate with DPA or may separate.
Figure 2(b) differs from Figure 2(a) in that the LMs is separated out, and a proxy LMp is added between the LMs and LMc.
LMp and FM-CP co-locate at the CPA.
FM-CP and LMc co-locate at the CPN.
The LMs may be centralized whereas the LMp may be distributed or centralized according to whether the CPA is distributed or centralized.
Host-based variants of the mobility function configurations from Figures 2(a) and 2(b) are respectively shown in Figures 3(a) and 3(b) where the role to perform mobility functions by CPN and DPN are now taken by the MN. The MN then needs to possess the mobility functions FM and LMc.
(a) (b)
+-----+
|LMs |
+-----+
+------------+ +------------+
|CPA: | |CPA: |
|FM-CP, LMs | |FM-CP, LMp |
+------------+ +------------+
+------------+ +------------+ +------------+ +------------+
|DPA(IPa1): | |DPA(IPa2): | |DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | |anchors IP2 | ... |anchors IP1 | |anchors IP2 | ...
|FM-DP | |FM-DP | |FM-DP | |FM-DP |
+------------+ +------------+ +------------+ +------------+
+------------+ +------------+
|MN(IP1) | |MN(IP1) |
|flow(IP1,..)| |flow(IP1,..)|
|FM, LMc | |FM, LMc |
+------------+ +------------+
Figure 3. Configurations of host-based mobility management (a) FM-CP and LMs at CPA, FM-DP at DPA, FM and LMc at MN; (b) Separate LMs, FM-CP and LMp at CPA, FM-DP at DPA, FM and LMc at MN.
Figure 3 shows 2 configurations of host-based mobility management with multiple instances of DPA for a distributed mobility anchoring environment.
There is an FM-DP function at each of the distributed DPA.
The control plane may either be distributed (not shown) or centralized.
When the CPA co-locates with the distributed DPA there will be multiple instances of the co-located CPA and DPA (not shown).
There is an FM-CP function at the CPA.
The MN possesses the mobility functions such as FM and LMc.
The MN is allocated an IP prefix/address IP1 which is anchored to the DPA with the IP prefix/address IPa1. It is using IP1 to communicate with a CN not shown in the figure. The flow of this communication session is shown as flow(IP1, ...) which uses IP1 and other parameters.
In Figure 3(a), LMs and FM-CP co-locate at the CPA.
The LMs may be distributed or centralized according to whether the CPA is distributed (not shown) or centralized.
Figure 3(b) differs from Figure 3(a) in that the LMs is separated out and the proxy LMp is added between the LMs and LMc.
LMp and FM-CP co-locate at the CPA.
The LMs may be centralized whereas the LMp may be distributed or centralized according to whether the CPA is distributed (not shown) or centralized.
Figure 4 shows two configurations of NEMO basic support for a mobile router.
(a) (b)
+-----+
|LMs |
+-----+
+------------+ +------------+
|CPA: | |CPA: |
|FM-CP, LMs | |FM-CP, LMp |
+------------+ +------------+
+------------+ +------------+ +------------+ +------------+
|DPA(IPa1): | |DPA(IPa2): | |DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | |anchors IP2 | |anchors IP1 | |anchors IP2 |
|DHCPv6-PD | |DHCPv6-PD | ... |DHCPv6-PD | |DHCPv6-PD | ...
| IPn1| | IPn2| | IPn1| | IPn2|
|FM-DP | |FM-DP | |FM-DP | |FM-DP |
+------------+ +------------+ +------------+ +------------+
+------------+ +------------+
|MR(IP1) | |MR(IP1) |
|anchors IPn1| |anchors IPn1|
|FM, LMc | |FM, LMc |
+------------+ +------------+
+------------+ +------------+
|MNN(IPn1) | |MNN(IPn1) |
|flow(IPn1,.)| |flow(IPn1,.)|
+------------+ +------------+
Figure 4. Configurations of NEMO basic support for a MR. (a) FM-CP and LMs at CPA, FM-DP at DPA, FM and LMc at MR; (b) Separate LMs, FM-CP and LMp at CPA, FM-DP at DPA, FM and LMc at MR.
Figure 4 shows 2 configurations of host-based mobility management for a MR with multiple instances of DPA for a distributed mobility anchoring environment.
There is an FM-DP function at each of the distributed DPA.
The control plane may either be distributed (not shown) or centralized.
When the CPA co-locates with the distributed DPA there will be multiple instances of the co-located CPA and DPA (not shown).
There is FM-CP function at the CPA.
The MR possesses the mobility functions FM and LMc.
MR is allocated an IP prefix/address IP1 which is anchored to the DPA with the IP prefix/address IPa1.
A mobile network node (MNN) in the mobile network is allocated an IP prefix/address IPn1 which is anchored to the MR with the IP prefix/address IP1.
The MNN is using IPn1 to communicate with a correspondent node (CN) not shown in the figure. The flow of this communication session is shown as flow(IPn1, ...) which uses IPn1 and other parameters.
In Figure 4(a), LMs and FM-CP co-locate at the CPA.
The LMs may be distributed or centralized according to whether the CPA is distributed (not shown) or centralized.
Figure 4(b) differs from Figure 4(a) in that the LMs is separated out and the proxy LMp is added between the LMs and LMc.
LMp and FM-CP co-locate at the CPA.
The LMs may be centralized whereas the LMp may be distributed or centralized according to whether the CPA is distributed (not shown) or centralized.
The operations of distributed mobility anchoring are defined in order that they may work together in expected manners to produce a distributed mobility solution. The needed information is passed as mobility message parameters, which must be protected in terms of integrity. Some parameters may require a means to support privacy of an MN or MR.
The mobility needs in 5G Wireless and beyond are diverse. Therefore operations needed to enable different distributed mobility solutions in different distributed mobility anchoring configurations are extensive as illustrated below. It is however not necessary for every distributed mobility solution to exhibit all the operations listed in this section. A given distributed mobility solution may exhibit the operations as needed.
An example LM design consists of a distributed database with multiple LMs servers. The location information about the prefix/address of an MN is primarily at a given LMs. Peer LMs may exchange the location information with each other. LMc may retrieve a given record or send a given record update to LMs.
Location management configurations:
Location management operations and parameters:
The parameters indicated above are only the minimal. In a specific mobility protocol, additional parameters should be added as needed. Examples of these additional parameters are those passed in the mobility options of the mobility header for MIPv6 [RFC6275] and for PMIPv6 [RFC5213].
Forwarding management configurations:
Forwarding management operations and parameters:
Parameters:
IP mobility support may be provided only when needed instead of being provided by default. The LM and FM functions in the different configurations shown in Section 3.1 are then utilized only when needed.
A straightforward choice of mobility anchoring is for a flow to use the IP prefix of the network to which the MN is attached when the flow is initiated [I-D.seite-dmm-dma].
The IP prefix/address at the MN's side of a flow may be anchored at the access router to which the MN is attached. For example, when an MN attaches to a network (Net1) or moves to a new network (Net2), it is allocated an IP prefix from the attached network. In addition to configuring new link-local addresses, the MN configures from this prefix an IP address which is typically a dynamic IP address. It then uses this IP address when a flow is initiated. Packets to the MN in this flow are simply forwarded according to the forwarding table.
There may be multiple IP prefixes/addresses that an MN can select when initiating a flow. They may be from the same access network or different access networks. The network may advertise these prefixes with cost options [I-D.mccann-dmm-prefixcost] so that the mobile node may choose the one with the least cost. In addition, these IP prefixes/addresses may be of different types regarding whether mobility support is needed [I-D.ietf-dmm-ondemand-mobility]. A flow will need to choose the appropriate one according to whether it needs IP mobility support.
When IP mobility support is not needed for a flow, the LM and FM functions are not utilized so that the configurations in Section 3.1 are simplified as shown in Figure 5.
Net1 Net2 +---------------+ +---------------+ |AR1 | AR is changed |AR2 | +---------------+ -------> +---------------+ |CPA: | |CPA: | |---------------| |---------------| |DPA(IPa1): | |DPA(IPa2): | |anchors IP1 | |anchors IP2 | +---------------+ +---------------+ +...............+ +---------------+ .MN(IP1) . MN moves |MN(IP2) | .flow(IP1,...) . =======> |flow(IP2,...) | +...............+ +---------------+
Figure 5. Changing to the new IP prefix/address. MN running a flow using IP1 in a network Net1 changes to running a flow using IP2 in Net2.
When there is no need to provide IP mobility to a flow, the flow may use a new IP address acquired from a new network as the MN moves to the new network.
Regardless of whether IP mobility is needed, if the flow has terminated before the MN moves to a new network, the flow may subsequently restart using the new IP address allocated from the new network.
When IP session continuity is needed, even if a flow is ongoing as the MN moves, it may still be desirable for the flow to change to using the new IP prefix configured in the new network. The flow may then close and then restart using a new IP address configured in the new network. Such a change in the IP address of the flow may be enabled using a higher layer mobility support which is not in the scope of this document.
In Figure 5, a flow initiated while the MN was using the IP prefix IP1 anchored to a previous access router AR1 in network Net1 has terminated before the MN moves to a new network Net2. After moving to Net2, the MN uses the new IP prefix IP2 anchored to a new access router AR2 in network Net2 to start a new flow. The packets may then be forwarded without requiring IP layer mobility support.
An example call flow is outlined in Figure 6.
MN AR1 AR2 CN |MN attaches to AR1: | | | |acquire MN-ID and profile | | |--RS---------------->| | | | | | | |<----------RA(IP1)---| | | | | | | Allocated prefix IP1 | | | IP1 address configuration | | | | | | |<-Flow(IP1,IPcn,...)-+--------------------------------------------->| | | | | |MN detaches from AR1 | | | |MN attaches to AR2 | | | | | | | |--RS------------------------------>| | | | | | |<--------------RA(IP2)-------------| | | | | | Allocated prefix IP2 | | | IP2 address configuration | | | | | | |<-new Flow(IP2,IPcn,...)-----------+------------------------------->| | | | |
Figure 6. Re-starting a flow to use the IP allocated from the network at which the MN is attached.
A network or network slice may not need IP mobility support. For example, a network slice for stationary sensors only will never encounter mobility.
The standard functions in IPv6 already include dropping the old IPv6 prefix/address and acquiring new IPv6 prefix/address when the node changes its point of attachment to a new network. Therefore, a network or network slice not providing IP mobility support at all will not need any of the functions with the mobility operations and messages described in Section 3.2.
On the other hand, a network or network slice supporting a mix of flows requiring and not requiring IP mobility support will still need the mobility functions, which it will invoke or not invoke as needed.
The guidelines for the IPv6 nodes in a network or network slice supporting a mix of flows requiring and not requiring IP mobility support include the following:
The above guidelines are only to enable distinguishing whether there is need of IP mobility support for a flow that does not. When the flow needs IP mobility support, the list of guidelines will continue in Section 4.2.1.
When IP mobility is needed for a flow, the LM and FM functions in Section 3.1 are utilized. The mobility support may be provided by IP prefix anchor switching to the new network to be described in Section 5 or by using other mobility management methods ([Paper-Distributed.Mobility.PMIP] and [Paper-Distributed.Mobility.Review]). Then the flow may continue to use the IP prefix from the prior network of attachment. Yet some time later, the user application for the flow may be closed. If the application is started again, the new flow may not need to use the prior network's IP address to avoid having to invoke IP mobility support. This may be the case where a dynamic IP prefix/address rather than a permanent one is used. The flow may then use the new IP prefix in the network where the flow is being initiated. Routing is again kept simpler without employing IP mobility and will remain so as long as the MN which is now in the new network has not moved again and left to another new network.
An example call flow in this case is outlined in Figure 7.
MN AR1 AR2 CN |MN attaches to AR1: | | | |acquire MN-ID and profile | | |--RS---------------->| | | | | | | |<----------RA(IP1)---| | | | | | | Allocated prefix IP1 | | | IP1 address configuration | | | | | | |<-Flow(IP1,IPcn,...)-+--------------------------------------------->| | | | | |MN detach from AR1 | | | |MN attach to AR2 | | | | | | | |--RS------------------------------>| | IP mobility support such as that described in next sub-section |<--------------RA(IP2,IP1)---------| | | | | | |<-Flow(IP1,IPcn,...)---------------+------------------------------->| | | | | Allocated prefix IP2 | | | IP2 address configuration | | | | | | Flow(IP1,IPcn) terminates | | | | | | |<-new Flow(IP2,IPcn,...)-----------+------------------------------->| | | | |
Figure 7. A flow continues to use the IP from its home network after MN has moved to a new network.
The configuration guidelines of distributed mobility for the IPv6 nodes in a network or network slice supporting a mix of flows requiring and not requiring distributed mobility support are as follows:
The guidelines of distributed mobility for the IPv6 nodes in a network or network slice supporting a mix of flows requiring and not requiring distributed mobility support had begun with those given as GL-mix in Section 4.1.1 and continue as follows:
IP mobility is invoked to enable IP session continuity for an ongoing flow as the MN moves to a new network. Here the anchoring of the IP address of the flow is in the home network of the flow, which is not in the current network of attachment. A centralized mobility management mechanism may employ indirection from the anchor in the home network to the current network of attachment. Yet it may be difficult to avoid unnecessarily long route when the route between the MN and the CN via the anchor in the home network is significantly longer than the direct route between them. An alternative is to switch the IP prefix/address anchoring to the new network.
The IP prefix/address anchoring may move without changing the IP prefix/address of the flow. Here the LM and FM functions in Figures 1(a) and 1(b) in Section 3.1 are implemented as shown in Figure 8.
Net1 Net2 +---------------+ +---------------+ |AR1 | |AR2 | +---------------+ +---------------+ |CPA: | |CPA: | |LM:IP1<-->IPa2 | |LM:IP1<-->IPa2 | |---------------| |---------------| |DPA(IPa1): | anchoring of IP1 is moved |DPA(IPa2): | |anchored IP1 | =======> |anchors IP2,IP1| |FM:DHCPv6-PD | |FM:DHCPv6-PD | +---------------+ +---------------+ +...............+ +---------------+ .MN(IP1) . MN moves |MN(IP2,IP1) | .flow(IP1,...) . =======> |flow(IP1,...) | +...............+ +---------------+
Figure 8. IP prefix/address anchor switching to the new network. MN with flow using IP1 in Net1 continues to run the flow using IP1 as it moves to Net2.
As an MN with an ongoing session moves to a new network, the flow may preserve IP session continuity by moving the anchoring of the original IP prefix/address of the flow to the new network. BGP UPDATE messages may be used to change the forwarding table entries as described in [I-D.templin-aerolink] and [I-D.mccann-dmm-flatarch] if the response time of such updates does not exceed the handover delay requirement of the flow. An alternative is to use a centralized routing protocol to be described in Section 5.2 with a centralized control plane.
The configuration guideline for a flat network or network slice supporting a mix of flows requiring and not requiring IP mobility support is:
The guidelines (GL-mix) in Section 4.1.1 and in Section 4.2.1 for the IPv6 nodes for a network or network slice supporting a mix of flows requiring and not requiring IP mobility support apply here. In addition, the following are required.
An example of IP prefix anchor switching is in the case where Net1 and Net2 both belong to the same operator network with separation of control and data planes ([I-D.liu-dmm-deployment-scenario] and [I-D.matsushima-stateless-uplane-vepc]), where the controller may send to the switches/routers the updated information of the forwarding tables with the IP address anchoring of the original IP prefix/address at AR1 moved to AR2 in the new network. That is, the IP address anchoring in the original network which was advertising the prefix will need to move to the new network. As the anchoring in the new network advertises the prefix of the original IP address in the new network, the forwarding tables will be updated so that packets of the flow will be forwarded according to the updated forwarding tables.
The configurations in Figures 1(a) and 1(b) in Section 3.1 for which the FM-CP and the LM are centralized and the FM-DP's are distributed apply here. Figure 9 shows its implementation where the LM is a binding between the original IP prefix/address of the flow and the IP address of the new DPA, whereas the FM uses the DHCPv6-PD protocol.
Net1 Net2 +----------------------------------------------------------------------+ | CPA: | | LM:IP1<-->IPa2 | | FM-CP | +----------------------------------------------------------------------+ +---------------+ +---------------+ |AR1 | |AR2 | +---------------+ +---------------+ |DPA(IPa1): | anchoring of IP1 is moved |DPA(IPa2): | |anchored IP1 | =======> |anchors IP2,IP1| |FM:DHCPv6-PD | |FM:DHCPv6-PD | +---------------+ +---------------+ +...............+ +---------------+ .MN(IP1) . MN moves |MN(IP2,IP1) | .flow(IP1,...) . =======> |flow(IP1,...) | +...............+ +---------------+
Figure 9. IP prefix/address anchor switching to the new network with with the LM and the FM-CP in a centralized control plane whereas the FM-DP's are distributed.
The example call flow in Figure 10 shows that MN is allocated IP1 when it attaches to the AR1 A flow running in MN and needing IP mobility may continue to use the previous IP prefix by moving the anchoring of the IP prefix to the new network. Yet a new flow to be initiated in the new network may simply use a new IP prefix allocated from the new network.
MN AR1 AR2 DHCPv6 Servers CN |MN attaches to AR1: | | | | |acquire MN-ID and profile | | | |--RS---------------->| | | | |<----------RA(IP1)---| | | | | | | Allocate MN:IP1 | IP addr config | | | | | | | | | |<-Flow(IP1,IPcn,...)-+--------------------------------------------->| | | | | | |MN detach from AR1 | | | | |MN attach to AR2 | | | | | | | | | |--RS------------------------------>| | | | | | | | | |------DHCPv6 release-------------->| | | | | | | | | |--DHCPv6 PD request->| | | | |<-DHCPv6 PD reply--->| | | | | | | | forwarding table updates | | | | | | | |<--------------RA(IP2,IP1)---------| | | | | | Allocate MN:IP2 | IP addr config | | | | | | | | | |<-Flow(IP1,IPcn,...)---------------+------------------------------->| | | | | | | Flow(IP1,IPcn,...) terminates | | | | | | | | | | DHCPv6-PD timeout | | | | | | | | forwarding table updates | | | | | | | | | | | | |<-new Flow(IP2,IPcn,...)-----------+------------------------------->| | | | | |
Figure 10. DMM solution. MN with flow using IP1 in Net1 continues to run the flow using IP1 as it moves to Net2.
As the MN moves from AR1 to AR2, the AR1 as a DHCPv6 client may send a DHCPv6 release message to release the IP1. It is now necessary for AR2 to learn the IP prefix of the MN from the previous network so that it will be possible for Net2 to allocate both the previous network prefix and the new network prefix. The network may learn the previous prefix in different methods. For example, the MN may provide its previous network prefix information by including it to the RS message [I-D.jhlee-dmm-dnpp].
Knowing that MN is using IP1, the AR2 sends to a DHCPv6 server a DHCPv6-PD request to move the IP1 to AR2. The server sends to AR2 a DHCPv6-PD reply to move the IP1. Then forwarding tables updates will take place here.
In addition, the MN also needs a new IP in the new network. The AR2 may now send RA to AR2, with prefix information that includes IP1 and IP2. The MN may then continue to use IP1. In addition, the MN is allocated the prefix IP2 with which it may configure its IP addresses. Now for flows using IP1, packets destined to IP1 will be forwarded to the MN via AR2.
As such flows have terminated and DHCPv6-PD has timed out, IP1 goes back to Net1. MN will then be left with IP2 only, which it will use when it now starts a new flow.
The configuration guideline for a flat network or network slice with centralized control plane and supporting a mix of flows requiring and not requiring IP mobility support is:
The guidelines (GL-mix) in Section 4.1.1 and in Section 4.2.1 for the IPv6 nodes for a network or network slice supporting a mix of flows requiring and not requiring IP mobility support apply here. The guidelines (GL-mix) in Section 5.1.1 for moving anchoring for a flat network also apply here. In addition, the following are required.
The configuration for a hierarchical network has been shown in Figures 2(a) and 2(b) in Section 3.1.2. With centralized control plane, CPA and CPN, with the associated LM and FM-CP are all co-located. There are multiple DPAs (each with FM-DP) in distributed mobility anchoring. In the data plane, there are multiple DPNs (each with FM-DP) hierarchically below each DPA. The DPA at each AR supports forwarding to the DPN at each of a number of forwarding switches (FW's). A mobility event in this configuration belonging to distributed mobility management will be deferred to Section 5.4.
In this distributed mobility configuration, a mobility event involving change of FW only but not of AR as shown in Figure 11 may still belong to centralized mobility management and may be supported using PMIPv6. This configuration of network-based mobility is also applicable to host-based mobility with the modification for the MN directly taking the role of DPN and CPN, and the corresponding centralized mobility event may be supported using MIPv6.
In Figure 11, the IP prefix allocated to the MN is anchored at the access router (AR) supporting indirection to the old FW to which the MN was originally attached as well as to the new FW to which the MN has moved.
The realization of LM may be the binding between the IP prefix/address of the flow used by the MN and the IP address of the DPN to which MN has moved. The implementation of FM to enable change of FW without changing AR may be accomplished using tunneling between the AR and the FW as described in [I-D.korhonen-dmm-local-prefix] and in [I-D.templin-aerolink] or using some other L2 mobility mechanism.
Net1 Net2
+----------------------------------------------------------------------+
| CPA,CPN: |
| LM:IP1<-->IPn2 |
| FM-CP |
+----------------------------------------------------------------------+
+---------------+
|AR1 |
+---------------+
|DPA(IPa1): |
|anchors IP1 |
|FM-DP |
+---------------+
+---------------+ +---------------+
|FW1 | |FW2 |
+---------------+ FW is changed +---------------+
|DPN(IPn1): | -------> |DPN(IPn2): |
|FM-DP | |FM-DP |
+---------------+ +---------------+
+...............+ +---------------+
.MN(IP1) . MN moves |MN(IP2) |
.flow(IP1,...) . =======> |flow(IP1,...) |
+...............+ +---------------+
Figure 11. Mobility without involving change of IP anchoring in a network in which the IP prefix allocated to the MN is anchored at an AR which is hierarchically above multiple FWs to which the MN may connect.
The configuration guideline for a hierarchical network or network slice with centralized control plane and supporting a mix of flows requiring and not requiring IP mobility support is:
Even when the mobility event does not involve change of anchor, it is still necessary to distinguish whether a flow needs IP mobility support.
The GL-mix guidelines in Section 4.1.1 and in Section 4.2.1 for the IPv6 nodes for a network or network slice supporting a mix of flows requiring and not requiring IP mobility support apply here. In addition, the following are required.
The configuration for the hierarchical network has been shown in Figures 2(a) and 2(b) in Section 3.1.2. Again, with centralized control plane, CPA and CPN, with the associated LM and FM-CP are all co-located. There are multiple DPAs (each with FM-DP) in distributed mobility anchoring. In the data plane, there are multiple DPNs (each with FM-DP) hierarchically below each DPA. The DPA at each AR supports forwarding to the DPN at each of a number of forwarding switches (FW's).
A distributed mobility event in this configuration involves change from a previous DPN which is hierarchically under the previous DPA to a new DPN which is hierarchically under a new DPA. Such an event involving change of both DPA and DPN is shown in Figure 12.
Net1 Net2
+----------------------------------------------------------------------+
| CPA,CPN,Aggregate Router: |
| LM:IP1<-->IPa2,IPn2 |
| FM-CP |
+----------------------------------------------------------------------+
+-----------------+
|Aggregate Router |
+-----------------+
|FM-DP |
+-----------------+
+---------------+ +---------------+
|AR1 | |AR2 |
+---------------+ +---------------+
|DPA(IPa1): | anchoring of IP1 is moved |DPA(IPa2): |
|anchored IP1 | =======> |anchors IP2,IP1|
|FM:DHCPv6-PD | |FM:DHCPv6-PD |
+---------------+ +---------------+
+---------------+ +---------------+
|FW1 | |FW2 |
+---------------+ FW is changed +---------------+
|DPN(IPn1): | -------> |DPN(IPn2): |
|FM-DP | |FM-DP |
+---------------+ +---------------+
+...............+ +---------------+
.MN(IP1) . MN moves |MN(IP2,IP1) |
.flow(IP1,...) . =======> |flow(IP1,...) |
+...............+ +---------------+
Figure 12. Mobility involving change of IP anchoring in a network with hierarchy in which the IP prefix allocated to the MN is anchored at an Edge Router supporting multiple access routers to which the MN may connect.
This deployment case involves both a change of anchor from AR1 to AR2 and a network hierarchy AR-FW. It can be realized by a combination of relocating the IP prefix/address anchoring from AR1 to AR2 with the mechanism as described in Section 5.2 and then forwarding the packets with network hierarchy AR-FW as described in Section 5.3.
To change the anchoring of IP1, AR1 acting as a DHCPv6-PD client may exchange message with the DHCPv6 server to release the prefix IP1. Meanwhile, AR2 acting as a DHCPv6-PD client may exchange message with the DHCPv6 server to delegate the prefix IP1 to AR2.
The configuration guideline (GL-cfg) for a hierarchical network or network slice with centralized control plane described in Section 5.3.1 apply here.
The GL-mix guidelines in Section 4.1.1 and in Section 4.2.1 for the IPv6 nodes for a network or network slice supporting a mix of flows requiring and not requiring IP mobility support apply here.
The guidelines (GL-switch) in Section 5.1.1 for anchoring relocation and in Section 5.2.1 for a centralized control plane also apply here.
In addition, the guidelines for indirection between the new DPA and the new DPN as described in Section 5.3.1 apply as well.
The configuration for network mobility has been shown in Figures 4(a) and 4(b) in Section 3.1.4. Again, with centralized control plane, CPA, with the associated LM and FM-CP are all co-located. There are multiple DPAs (each with FM-DP) in the data plane in distributed mobility anchoring. The MR possesses the mobility functions FM and LMc. The IP prefix IPn1 is delegated to the MR, to which a MNN is attached and is allocated with an IP address from IPn1.
Figure 13 shows a distributed mobility event in a hierarchical network with a centralized control plane involving a change of attachment of the MR from a previous DPA to a new DPA while the MNN is attached to and therefore moves with the MR.
Net1 Net2
+----------------------------------------------------------------------+
| CPA,Aggregate Router: |
| LM:IP1<-->IPa2; IPn1<-->IP1 |
| FM-CP, LM |
+----------------------------------------------------------------------+
+-----------------+
|Aggregate Router |
+-----------------+
|FM-DP |
+-----------------+
+---------------+ +---------------+
|AR1 | |AR2 |
+---------------+ +---------------+
|DPA(IPa1): | anchoring of IP1 is moved |DPA(IPa2): |
|anchored IP1 | =======> |anchors IP2,IP1|
|DHCPv6-PD IPn1 | | |
|FM-DP | |FM-DP |
+---------------+ +---------------+
+...............+ +---------------+
.MR(IP1) . MR moves |MR(IP2,IP1) |
+...............+ =======> +---------------+
.FM, LMc . |FM, LMc |
.anchors IPn1 . |anchors IPn1 |
+...............+ +---------------+
+...............+ +---------------+
.MNN(IPn1) . MNN moves with MR |MNN(IPn1) |
.flow(IPn1,...) . =======> |flow(IPn1,...) |
+...............+ +---------------+
Figure 13. Mobility involving change of IP anchoring for a MR to which a MNN is attached.
As the MR with source IP prefix IP1 moves from AR1 to AR2, mobility support may be provided by moving the anchoring of IP1 from AR1 to AR2 using the mechanism described in Section 5.2.
The forwarding table updates will take place at AR1, AR2, the aggregate router, and other affected routers such that the packet from the CN to the MNN will traverse from the aggregate router towards AR2 instead of towards AR1.
The configuration guideline for a network or network slice with centralized control plane to provide network mobility is:
The GL-mix guidelines in Section 4.1.1 and in Section 4.2.1 for the IPv6 nodes for a network or network slice supporting a mix of flows requiring and not requiring IP mobility support apply here.
Here, because the MN is a MR, the following guideline is added:
The guidelines (GL-switch) in Section 5.1.1 for anchoring relocation and in Section 5.2.1 for a centralized control plane also apply here.
Again because the MN is a MR, the following guidelines are added:
The security considerations are already described in different sessions through this document. They are described in terms of integrity support, privacy support etc. in describing the mobility functions in Section 3.2. They are also described in the guidelines for IPv6 nodes in various subsections Section 4 and Section 5.
This document presents no IANA considerations.
This document has benefited from other work on mobility solutions using BGP update, on mobility support in SDN network, on providing mobility support only when needed, and on mobility support in enterprise network. These work have been referenced. While some of these authors have taken the work to jointly write this document, others have contributed at least indirectly by writing these drafts. The latter include Philippe Bertin, Dapeng Liu, Satoru Matushima, Peter McCann, Pierrick Seite, Jouni Korhonen, and Sri Gundavelli.
Valuable comments have also been received from John Kaippallimalil, ChunShan Xiong, and Dapeng Liu.
| [I-D.ietf-dmm-deployment-models] | Gundavelli, S. and S. Jeon, "DMM Deployment Models and Architectural Considerations", Internet-Draft draft-ietf-dmm-deployment-models-00, August 2016. |
| [I-D.ietf-dmm-fpc-cpdp] | Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S. and D. Moses, "Protocol for Forwarding Policy Configuration (FPC) in DMM", Internet-Draft draft-ietf-dmm-fpc-cpdp-05, October 2016. |
| [I-D.ietf-dmm-ondemand-mobility] | Yegin, A., Moses, D., Kweon, K., Lee, J., Park, J. and S. Jeon, "On Demand Mobility Management", Internet-Draft draft-ietf-dmm-ondemand-mobility-09, December 2016. |
| [I-D.jhlee-dmm-dnpp] | Lee, J. and Z. Yan, "Deprecated Network Prefix Provision", Internet-Draft draft-jhlee-dmm-dnpp-01, April 2016. |
| [I-D.korhonen-dmm-local-prefix] | Korhonen, J., Savolainen, T. and S. Gundavelli, "Local Prefix Lifetime Management for Proxy Mobile IPv6", Internet-Draft draft-korhonen-dmm-local-prefix-01, July 2013. |
| [I-D.liu-dmm-deployment-scenario] | Liu, V., Liu, D., Chan, A., Lingli, D. and X. Wei, "Distributed mobility management deployment scenario and architecture", Internet-Draft draft-liu-dmm-deployment-scenario-05, October 2015. |
| [I-D.matsushima-stateless-uplane-vepc] | Matsushima, S. and R. Wakikawa, "Stateless user-plane architecture for virtualized EPC (vEPC)", Internet-Draft draft-matsushima-stateless-uplane-vepc-06, March 2016. |
| [I-D.mccann-dmm-flatarch] | McCann, P., "Authentication and Mobility Management in a Flat Architecture", Internet-Draft draft-mccann-dmm-flatarch-00, March 2012. |
| [I-D.mccann-dmm-prefixcost] | McCann, P. and J. Kaippallimalil, "Communicating Prefix Cost to Mobile Nodes", Internet-Draft draft-mccann-dmm-prefixcost-03, April 2016. |
| [I-D.seite-dmm-dma] | Seite, P., Bertin, P. and J. Lee, "Distributed Mobility Anchoring", Internet-Draft draft-seite-dmm-dma-07, February 2014. |
| [I-D.templin-aerolink] | Templin, F., "Asymmetric Extended Route Optimization (AERO)", Internet-Draft draft-templin-aerolink-74, November 2016. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC3753] | Manner, J. and M. Kojo, "Mobility Related Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004. |
| [RFC5213] | Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K. and B. Patil, "Proxy Mobile IPv6", RFC 5213, DOI 10.17487/RFC5213, August 2008. |
| [RFC6275] | Perkins, C., Johnson, D. and J. Arkko, "Mobility Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 2011. |
| [RFC7077] | Krishnan, S., Gundavelli, S., Liebsch, M., Yokota, H. and J. Korhonen, "Update Notifications for Proxy Mobile IPv6", RFC 7077, DOI 10.17487/RFC7077, November 2013. |
| [RFC7333] | Chan, H., Liu, D., Seite, P., Yokota, H. and J. Korhonen, "Requirements for Distributed Mobility Management", RFC 7333, DOI 10.17487/RFC7333, August 2014. |
| [RFC7429] | Liu, D., Zuniga, JC., Seite, P., Chan, H. and CJ. Bernardos, "Distributed Mobility Management: Current Practices and Gap Analysis", RFC 7429, DOI 10.17487/RFC7429, January 2015. |
| [Paper-Distributed.Mobility] | Lee, J., Bonnin, J., Seite, P. and H. Chan, "Distributed IP Mobility Management from the Perspective of the IETF: Motivations, Requirements, Approaches, Comparison, and Challenges", IEEE Wireless Communications, October 2013. |
| [Paper-Distributed.Mobility.PMIP] | Chan, H., "Proxy Mobile IP with Distributed Mobility Anchors", Proceedings of GlobeCom Workshop on Seamless Wireless Mobility, December 2010. |
| [Paper-Distributed.Mobility.Review] | Chan, H., Yokota, H., Xie, J., Seite, P. and D. Liu, "Distributed and Dynamic Mobility Management in Mobile Internet: Current Approaches and Issues", February 2011. |