| DMM | H. Chan, Ed. |
| Internet-Draft | X. Wei |
| Intended status: Informational | Huawei Technologies |
| Expires: November 10, 2017 | J. Lee |
| Sangmyung University | |
| S. Jeon | |
| Sungkyunkwan University | |
| A. Petrescu | |
| CEA, LIST | |
| F. Templin | |
| Boeing Research and Technology | |
| May 9, 2017 |
Distributed Mobility Anchoring
draft-ietf-dmm-distributed-mobility-anchoring-05
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 address configured from the new IP prefix which is 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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A key requirement in distributed mobility management [RFC7333] is to enable traffic to avoid traversing a single mobility anchor far from an optimal route. The traffic of a flow SHOULD then 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 [I-D.geng-netslices-architecture], 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.
As an MN attaches to an access router and establishes a link between them, a /64 IPv6 prefix anchored to the router may be assigned to the link for exclusive use by the MN [RFC6459]. The MN may then configure a global IPv6 address from this prefix and use it as the source IP address in a flow to communicate with 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. However, after the flow has been initiated, the MN may later move to another network, so that the IP address 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 both requiring and not requiring IP mobility support will need to distinguish these flows. The guidelines for the network or network slice to make such a distinction 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 distributed mobility management for a flat network.
The features common to both Figures 1(a) and 1(b) are:
(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.
In Figure 1(a), LM is at the 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 separate server LMs and a client LMc at the CPA. Then, 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.
In addition to the dmm feature already described in Figure 1, Figure 2 shows that there may be multiple instances of DPN, each with an FM-DP function, for each DPA in the hierarchy. Also when the CPN, each with an FM-CP function, is co-located with the distributed DPN there will be multiple instances of the co-located CPN and DPN (not shown).
In Figure 2(a), LMs is at the CPA and LMc is at the CPN. Then, LMs may be distributed or centralized according to whether the CPA is distributed or centralized.
Figure 2(b) differs from Figure 2(a) in that the LMs is separated out, and a proxy LMp at the CPA is added between the seaparate LMs and LMc at the CPN. Then, 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. Figures 3(a) and 3(b) can be obtained by simply collapsing CPN, DPN and MN from the respective Figures 2(a) and 2(b) into the MN in Figure 3 which now possesses the mobility functions FM and LMc that were performed previously by the CPN and the DPN.
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. Figures 4(a) and 4(b) can be obtained by simply changing the MN from the respective Figures 3(a) and 3(b) into the MR carrying a mobile network consisting of mobile network nodes (MNNs) in Figure 4.
An IP prefix/address IPn1 anchored to the MR is assigned for use by the MNN in the mobile network. The MNN uses IPn1 to communicate with a correspondent node (CN) not shown in the figure. The flow of this communication session is shown as flow(IPn1, ...), meaning it uses IPn1 and other parameters.
To enable the MR to anchor and to assign the IP prefix IPn1, the DPA delegates the prefix using DHCPv6-PD to the MR.
The operations of distributed mobility anchoring are defined in order that they might work together 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 only those operations 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 list above only gives the minimal set of the required parameters. 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), an IP prefix from the attached network is assigned to the MN's interface. 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 assigned 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)---| | | | | | | Assigned prefix IP1 | | | IP1 address configuration | | | | | | |<-Flow(IP1,IPcn,...)-+--------------------------------------------->| | | | | |MN detaches from AR1 | | | |MN attaches to AR2 | | | | | | | |--RS------------------------------>| | | | | | |<--------------RA(IP2)-------------| | | | | | Assigned prefix IP2 | | | IP2 address configuration | | | | | | |<-new Flow(IP2,IPcn,...)-----------+------------------------------->| | | | |
Figure 6. Re-starting a flow to use the IP prefix assigned 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 both requiring and not requiring IP mobility support will 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 both 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], [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)---| | | | | | | Assigned 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,...)---------------+------------------------------->| | | | | Assigned prefix IP2 | | | IP2 address configuration | | | | | | Flow(IP1,IPcn) terminates | | | | | | |<-new Flow(IP2,IPcn,...)-----------+------------------------------->| | | | |
Figure 7. A flow continues to use the IP prefix 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 both 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 both 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 at IPa1 | |LM:IP1 at IPa2 | | changes to | | | | IP1 at 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 both 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 both 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-DPs 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 at 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 the LM and the FM-CP in a centralized control plane whereas the FM-DPs are distributed.
The example call flow in Figure 10 shows that IP1 is assigned to MN when the MN 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 assigned from the new network.
MN AR1 AR2 DHCPv6 Servers CN |MN attaches to AR1: | | | | |acquire MN-ID and profile | | | |--RS---------------->| | | | |<----------RA(IP1)---| | | | | | | Assign 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)---------| | | | | | Assign 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 assign 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 the MN with prefix information that includes IP1 and IP2. The MN may then continue to use IP1. In addition, the prefix IP2 is assigned to the MN which may configure the IP addresses of its interface. 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 both 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 both 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 (FWs). 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 assigned 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 at 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 assigned 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 both 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 both 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 (FWs).
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 at IPn2 at IPa2 |
| 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 assigned 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 applies 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 both 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 an MNN is attached and has an IP address from IPn1 assigned to its interface.
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 the MR and therefore moves with the MR.
Net1 Net2
+----------------------------------------------------------------------+
| CPA,Aggregate Router: LM:IP1 at IPa2; IPn1 at 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 an 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 both 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:
Security protocols and mechanisms are employed to secure the network and to make continuous security improvements, and a DMM solution is required to support them [RFC7333]. In a DMM deployment [I-D.ietf-dmm-deployment-models] various attacks such as impersonation, denial of service, man-in-the-middle attacks need to be prevented. An appropriate security management function as defined in Section 2 controls these security protocols and mechanisms to provide access control, integrity, authentication, authorization, confidentiality, etc.
Security considerations are described in terms of integrity support, privacy support etc. in describing the mobility functions in Section 3.2. Here the mobility message parameters used in DMM must be protected, and some parameters require means to support MN and MR privacy. The security considerations are also described in the guidelines for IPv6 nodes in various subsections in Section 4, and Section 5.
The IP address anchoring of an IP prefix is moved from one network to another network to support IP mobility Section 5.1. As is considered in the guidelines for IPv6 nodes in Section 5.1.1, the security management function needs to enable the use in the new network of attachment the IP prefix assigned from another network. Yet it must do so without compromising on the needed security to prevent the possible misuse of an IP prefix belonging to another network.
In network mobility, the MNN using an IP prefix assigned to it from the MR when the MR was in a prior network moves with the MR to a new network Section 5.5. As is considered in the guidelines for IPv6 nodes in Section 5.5.1 to support IP mobility for an ongoing flow, the security management function needs to enable the continued use of this IP prefix by the MNN with MR in the new network of attachment. Yet it must do so without compromising on the needed security to prevent the possible misuse of an IP prefix belonging to another network.
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 works 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 been received from John Kaippallimalil, ChunShan Xiong, and Dapeng Liu. Dirk von Hugo, Byju Pularikkal, Pierrick Seite have generously provided careful review with helpful corrections and suggestions.
| [I-D.geng-netslices-architecture] | 67, 4., Bryant, S. and J. Dong, "Network Slicing Architecture", Internet-Draft draft-geng-netslices-architecture-00, March 2017. |
| [I-D.ietf-dmm-deployment-models] | Gundavelli, S. and S. Jeon, "DMM Deployment Models and Architectural Considerations", Internet-Draft draft-ietf-dmm-deployment-models-01, February 2017. |
| [I-D.ietf-dmm-fpc-cpdp] | Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S., Moses, D. and C. Perkins, "Protocol for Forwarding Policy Configuration (FPC) in DMM", Internet-Draft draft-ietf-dmm-fpc-cpdp-07, March 2017. |
| [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-10, January 2017. |
| [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. |
| [RFC6459] | Korhonen, J., Soininen, J., Patil, B., Savolainen, T., Bajko, G. and K. Iisakkila, "IPv6 in 3rd Generation Partnership Project (3GPP) Evolved Packet System (EPS)", RFC 6459, DOI 10.17487/RFC6459, January 2012. |
| [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. |