DMM H. Chan
Internet-Draft X. Wei
Intended status: Informational Huawei Technologies
Expires: January 9, 2017 J. Lee
Sangmyung University
S. Jeon
Instituto de Telecomunicacoes
F. Templin
Boeing Research and Technology
July 8, 2016
Distributed Mobility Anchoring
draft-chan-dmm-distributed-mobility-anchoring-08
Abstract
This document defines distributed mobility anchoring. Multiple
anchors and nodes are configured with appropriate mobility functions
and work together to enable mobility solutions. Example solution is
mid-session switching of the IP prefix anchor. Without ongoing
session requiring session continuity, a flow can be started or re-
started using the new IP prefix which is allocated from the new
network and is therefore anchored to the new network. With ongoing
session, the anchoring of the prior IP prefix may be relocated to the
new network to enable session continuity.
Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 9, 2017.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
3. Distributed anchoring . . . . . . . . . . . . . . . . . . . . 5
3.1. Distributed anchoring configurations . . . . . . . . . . 5
3.2. Distributed anchoring behaviors and message information
elements . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.1. Location management behaviors and message information
elements . . . . . . . . . . . . . . . . . . . . . . 9
3.2.2. Forwarding management behaviors and message
information elements . . . . . . . . . . . . . . . . 10
4. Example mobility solutions with distributed anchoring . . . . 12
4.1. IP mobility support only when needed . . . . . . . . . . 12
4.1.1. Not needed: Changing to the new IP prefix/address . . 13
4.1.2. Needed: Providing IP mobility support . . . . . . . . 14
4.2. IP prefix/address anchor switching to the new network . . 16
4.2.1. Centralized control plane . . . . . . . . . . . . . . 17
4.2.2. Hierarchical network . . . . . . . . . . . . . . . . 20
4.2.3. Hierarchical network with anchoring change . . . . . 22
5. Security Considerations . . . . . . . . . . . . . . . . . . . 23
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1. Normative References . . . . . . . . . . . . . . . . . . 24
8.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
A key requirement in distributed mobility management [RFC7333] is to
enable traffic to avoid traversing single mobility anchor far from
the optimal route. Distributed mobility management solutions do not
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make use of centrally deployed mobility anchor
[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 the mobile node moves, or when changing
operation and management requirements call for mobility anchor
switching, thus avoiding non-optimal routes. This draft proposes
distributed mobility anchoring to enable making such route changes.
Distributed mobility anchoring employs multiple anchors in the data
plane. In general, the control plane function may be separate from
the data plane functions and be centralized but may also co-located
with the data plane function at these distributed anchors. Different
configurations (Section 3.1) of distributed anchoring are then
possible. Yet the distributed anchors need to have expected
behaviors (Section 3.2).
A mobile node (MN) attached to an access router of a network may be
allocated an IP prefix which is anchored to that router. It may then
use the IP address configured from this prefix as the source IP
address to run a flow with its correspondent node (CN). When there
are multiple anchors, the flow may need to select the anchor when it
is initiated (Section 4). Using an anchor in 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 address no longer
belongs to the new network of attachment of the MN. Whether the flow
needs 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 reiniated with a new IP address
anchored in the new network (Section 4.1.1). On the other hand, if
the ongoing IP flow cannot cope with such change, the IP address
anchoring can be moved from the original network to the new network
(Section 4.2).
2. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "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 base
specification [RFC6275], the Proxy Mobile IPv6 specification
[RFC5213], and the DMM current practices and gap analysis [RFC7429].
This includes terms such as mobile node (MN), correspondent node
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(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 term:
Home network of an application session (or of an HoA): the network
that has allocated the IP address (HoA) used for the session
identifier by the application running in an MN. An MN may be
running multiple application sessions, and each of these sessions
can have a different home network.
IP prefix/address anchoring: An IP prefix, i.e., Home Network Prefix
(HNP), or address, i.e., Home Address (HoA), allocated to a mobile
node is topologically anchored to a node when the anchor node is
able to advertise a connected route into the routing
infrastructure for the allocated IP prefix.
Internetwork Location Management (LM) function: managing and keeping
track of the internetwork location of an MN. The location
information may be a binding of the IP advertised address/prefix,
e.g., HoA or HNP, to the IP routing address of the MN or of a node
that can forward packets destined to the MN. It is a control
plane function.
In a client-server protocol model, location query and update
messages may be exchanged between a Location Management client
(LMc) and a Location Management server (LMs).
With separation of control plane and data plane, the LM function
is in the control plane. It may be a logical function at the
control plane node, control plane anchor, or mobility controller.
It may be distributed or centralized.
Forwarding Management (FM) function: packet interception and
forwarding to/from the IP address/prefix assigned to the MN, based
on the internetwork location information, either to the
destination or to some other network element that knows how to
forward the packets to their destination.
This function may be used to achieve indirection. With separation
of control plane and data plane, FM may split into a FM function
in the data plane (FM-DP) and a FM function in the control plane
(FM-CP).
FM-DP may be distributed with distributed mobility management. It
may be a function in a data plane anchor or data plane node.
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FM-CP may be distributed or centralized. It may be a function in
a control plane node, control plane anchor or mobility controller.
Security Management (SM) function: The security management function
controls security mechanisms/protocols providing access control,
integrity, authentication, authorization, confidentiality, etc.
for the control plane and data plane.
This function resides in all nodes such as control plane anchor,
data plane anchor, mobile node, and correspondent node.
3. Distributed anchoring
3.1. Distributed anchoring configurations
The mobility functions may be implemented in different configurations
of distributed anchoring in architectures separating the control and
data planes. The separation as described in
[I-D.wt-dmm-deployment-models] has defined 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. Some
configurations are described in [I-D.sijeon-dmm-deployment-models].
Figure 1 shows 4 configurations of network-based mobility management.
In each configuration, an MN is allocated an IP prefix/address IP1
and 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.
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(a) (b) (c) (d)
+-----+ +-----+
|LMs | |LMs |
+-----+ +-----+
+------------+ +------------+ +------------+ +------------+
|CPA: | |CPA: | |CPA: | |CPA: |
|FM-CP, LM | |FM-CP, LMc | |FM-CP, LMs | |FM-CP, LMp |
+------------+ +------------+ +------------+ +------------+
+------------+ +------------+ +------------+ +------------+
|DPA(IPa1): | |DPA(IPa1): | |DPA(IPa1): | |DPA(IPa1): |
|anchors IP1 | |anchors IP1 | |anchors IP1 | |anchors IP1 |
|FM-DP | |FM-DP | |FM-DP | |FM-DP |
+------------+ +------------+ +------------+ +------------+
+------------+ +------------+
|CPN: | |CPN: |
|FM-CP, LMc | |FM-CP, LMc |
+------------+ +------------+
+------------+ +------------+
|DPN(IPn1): | |DPN(IPn1): |
|FM-DP | |FM-DP |
+------------+ +------------+
+------------+ +------------+ +------------+ +------------+
|MN(IP1) | |MN(IP1) | |MN(IP1) | |MN(IP1) |
|flow(IP1,..)| |flow(IP1,..)| |flow(IP1,..)| |flow(IP1,..)|
+------------+ +------------+ +------------+ +------------+
Figure 1. (a) FM-CP and LM at CPA, FM-DP at DPA; (b) Separate LMs,
FM-CP and LMc at CPA, FM-DP at DPA; (c) FM-CP and LMs at CPA, FM-DP
at DPA, FM-CP and LMc at CPN, FM-DP at DPN; (d) Separate LMs, FM-CP
and LMp at CPA, FM-DP at DPA, FM-CP and LMc at CPN, FM-DP at DPN.
In Figures 1(a), 1(b), 1(c), and 1(d), the IP address of the MN, IP1,
is anchored to the DPA which has the IP prefix/address IPa1. The
data plane is distributed so that there may be multiple instances of
the DPA (not shown). The control plane may either be distributed 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).
In Figure 1(a) and Figure 1(b), the network is flat with FM-DP at the
distributed DPA.
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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 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 are at the CPA.
The LMs may be centralized whereas the LMc may be distributed or
centralized according to whether the CPA is distributed or
centralized.
In Figure 1(c) and Figure 1(d), the network is hierarchical where
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.
In Figure 1(c), LMs and FM-CP are at the CPA. In addition, there are
FM-CP and LMc at the CPN. Again, 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 1(d) differs from Figure 1(c) in that the LMs is separated
out, and a proxy LMp is added between the LMs and LMc. LMp and FM-CP
are at the CPA. Again, there are FM-CP and LMc 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 1(c) and 1(d) are shown in Figures 2(a) and 2(b) where the
role to perform mobility functions by CPN and DPN are now taken by
the MN. The MN then need to possess the mobility functions FM and
LMc.
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(a) (b)
+-----+
|LMs |
+-----+
+------------+ +------------+
|CPA: | |CPA: |
|FM-CP, LMs | |FM-CP, LMp |
+------------+ +------------+
+------------+ +------------+
|DPA(IPa1): | |DPA(IPa1): |
|anchors IP1 | |anchors IP1 |
|FM-DP | |FM-DP |
+------------+ +------------+
+------------+ +------------+
|MN(IP1) | |MN(IP1) |
|flow(IP1,..)| |flow(IP1,..)|
|FM, LMc | |FM, LMc |
+------------+ +------------+
Figure 2. (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.
In Figure 2(a) and Figure 2(b), FM-DP is at the distributed DPA as
before.
In Figure 2(a), LMs and FM-CP are at the CPA. The 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 the proxy LMp is added between the LMs and LMc. LMp and FM-CP
are at the CPA. The FMs may be centralized whereas the LMp may be
distributed or centralized according to whether the CPA is
distributed or centralized.
3.2. Distributed anchoring behaviors and message information elements
The behaviors of distributed anchoring are defined in this section in
order that they may work together in expected manners to produce a
distributed mobility solution. The needed information elements are
passed as message parameters.
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3.2.1. Location management behaviors and message information elements
It is seen in (Section 3.1) that
(1) LMs may be a separate server or may co-locate with LMc at CPA;
(2) LMc may be at CPA, CPN, or MN.
Example LM design may consists of a distributed database of LMs
servers in a pool of distributed servers. The location information
about the prefix/address of a 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 information bebaviors:
(LM:1) LM may manage the location information in a client-server
database system. The example LM database functions are:
(LM:1-1) LMc may query LMs about location information for a
prefix of MN (pull).
Parameters:
IP prefix of MN.
(LM:1-2) LMs may reply to LMc query about location
information for a prefix of MN (pull).
Parameters:
IP prefix of MN,
IP address of FM-DP/DPA/DPN to forward the packets
of the flow.
(LM:1-3) LMs may inform LMc about location information for a
prefix of MN (push).
Parameters:
IP prefix of MN,
IP address of FM-DP/DPA/DPN to forward the packets
of the flow.
(LM:1-4) LMc may inform LMs about update location
information for a prefix of MN.
Parameters:
IP prefix of MN,
IP address of FM-DP/DPA/DPN to forward the packets
of the flow.
(LM:2) The LM may be a distributed database with multiple LMs
servers. For example:
(LM:2-1) A LMs may join a pool of LMs servers.
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Parameters:
IP address of the LMs,
IP prefixes for which the LMs will host the primary
location information.
(LM:2-2) LMs may query a peer LMs about location information
for a prefix of MN.
Parameters:
IP prefix.
(LM:2-3) LMs may reply to a peer LMs about location
information for a prefix of MN.
Parameters:
IP prefix of MN,
IP address of FM-DP/DPA/DPN to forward the packets
of the flow.
3.2.2. Forwarding management behaviors and message information elements
It is seen in (Section 3.1) that
(1) FM-CP may be at CPA, CPN, MN;
(2) FM-DP may be at DPA, DPN, MN.
The FM behaviors and message information elements are:
(FM:1) With distributed FM functions, the role of FM for a flow may
pass to another FM as the DPA or DPN changes.
(FM:2) In addition to above, a flow/session may be stateful for the
required information for QoS, charging, etc. are needed.
These states need to be transferred from the old anchor to
the new anchor.
(FM:3) An anchor may act on packets on a per flow basis and perform
the changes to the forwarding path upon a change of point of
attachment of a MN:
(FM:3-1) FM filters the packets up to the granularity of a
flow.
Example matching parameters are the 5-tuple of a
flow.
(FM:3-2) FM makes the necessary changes to the forwarding
path of a flow.
Example mechanism is through forwarding table
update activated by DHCPv6-PD.
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(FM:3-3) FM reverts the previously made changes to the
forwarding path of a flow when such changes are no
longer needed, e.g., when ongoing flows using an IP
prefix/address requiring session continuity have
closed.
Example mechanism is through expiration of
DHCPv6-PD.
(FM:4) An anchor may discover and be discovered such as through an
anchor registration system:
(FM:4-1) FM registers and authenticates itself with a
centralized mobility controller.
Parameters:
IP address of DPA and its CPA;
IP prefix anchored to the DPA.
(FM:4-2) registration reply: acknowledge of registration and
echo the input parameters.
(FM:4-3) FM discovers the FM of another IP prefix by
querying the mobility controller based on the IP
prefix.
Parameters:
IP prefix of MN.
(FM:4-4) when making anchor discovery FM expects the answer
parameters as: IP address of DPA to which IP prefix
of MN is anchored; IP prefix of the corresponding
CPA.
(FM:5) With separation of control plane function and data plane
function, these function must work together.
(FM:5-1) CPA/FM-CP sends forwarding table updates to DPA/FM-
DP.
Parameters:
new forwarding table entries to add;
expired forwarding table entries to delete.
(FM:5-2) DPA/FM-DP sends to CPA/FM-CP about its status and
load.
Parameters:
state of forwarding function being active or not;
loading percentage.
(FM:6) An anchor can buffer packets of a flow in a mobility event:
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(FM:6-1) CPA/FM-CP informs DPA/FM-DP to buffer packets of a
flow.
Trigger:
MN leaves DPA in a mobility event.
Parameters:
IP prefix of the flow for which packets need to be
buffered.
(FM:6-2) CPA/FM-CP on behalf of a new DPA/FM-DP informs the
CPA/FM-CP of the prior DPA/FM-DP that it is ready
to receive any buffered packets of a flow.
Parameters:
destination IP prefix of the flow's packets;
IP address of the new DPA.
4. Example mobility solutions with distributed anchoring
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 that network. It 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 to choose from. 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.
4.1. IP mobility support only when needed
IP mobility support may be provided only when needed instead of being
provided by default. The simplest configuration in this case is
shown in Figures 1(a) and 1(b) in Section 3.1 for which the LM and FM
functions are 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].
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4.1.1. Not needed: Changing to the new IP prefix/address
When IP mobility support is not needed for a flow, the LM and FM
functions are not utilized so that the configuration from Figures
1(a) and 1(b) in Section 3.1 simplifies to that shown in Figure 3.
Net1 Net2
+---------------+ +---------------+
|AR1 | |AR2 |
+---------------+ +---------------+
|CPA: | |CPA: |
|---------------| |---------------|
|DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | |anchors IP2 |
+---------------+ +---------------+
+...............+ +---------------+
.MN(IP1) . move |MN(IP2) |
.flow(IP1,...) . =======> |flow(IP2,...) |
+...............+ +---------------+
Figure 3. Changing to the new IP prefix/address. MN running a flow
using IP1 in 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 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 3, a flow initiated while the MN was in Net1 has terminated
before the MN moves to a new network Net2. After moving to Net2, the
MN uses the new IP prefix anchored in Net2 to start a new flow. The
packets may then be forwarded without requiring IP layer mobility
support.
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The call flow is outlined in Figure 4.
MN p-AR n-AR CN
|MN attaches to p-AR: | | |
|acquire MN-ID and profile | |
|--RS---------------->| | |
| | | |
|<----------RA(HNP1)--| | |
| | | |
Allocated prefix HNP1
IP1 address configuration
| | | |
|<-Flow(IP1,IPcn,...)-+--------------------------------------------->|
| | | |
|MN detaches from p-AR| | |
|MN attaches to n-AR | | |
| | | |
|--RS------------------------------>| |
| | | |
|<--------------RA(HNP2)------------| |
| | | |
Allocated prefix HNP2
IP2 address configuration
| | | |
|<-new Flow(IP2,IPcn,...)-----------+------------------------------->|
| | | |
Figure 4. A flow uses the IP allocated from the network at which the
MN is attached when the flow is initiated.
The security management function in the anchor node at a new network
must allow to assign a valid IP prefix/address to a mobile node.
4.1.2. Needed: Providing IP mobility support
When IP mobility is needed for a flow, the LM and FM functions in
Figures 1(a) and 1(b) 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 4.2 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. 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 permanent IP prefix/address is not used. The
flow may then use the new IP prefix in the network where the flow is
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being initiated. Routing is again kept simpler without employing IP
mobility and will remain so as long as the MN has not moved away from
that network.
The call flow in this case is outlined in Figure 5.
MN p-AR n-AR CN
|MN attaches to p-AR: | | |
|acquire MN-ID and profile | |
|--RS---------------->| | |
| | | |
|<----------RA(HNP1)--| | |
| | | |
Allocated prefix HNP1
IP1 address configuration
| | | |
|<-Flow(IP1,IPcn,...)-+--------------------------------------------->|
| | | |
|MN detach from p-AR | | |
|MN attach to n-AR | | |
| | | |
|--RS------------------------------>| |
IP mobility support such as that described in next sub-section
|<--------------RA(HNP2,HNP1)-------| |
| | | |
|<-Flow(IP1,IPcn,...)---------------+------------------------------->|
| | | |
Allocated prefix HNP2
IP2 address configuration
| | | |
Flow(IP1,IPcn) teminates
| | | |
|<-new Flow(IP2,IPcn,...)-----------+------------------------------->|
| | | |
Figure 5. A flow uses the IP allocated from the network at which the
MN is attached when the flow is initiated.
To provide IP mobility support with distributed anchoring, the
distributed anchors may need to message with each other. When such
messaging is needed, the anchors may need to discover each other as
described in the FM behaviors and information elements (FM:2) in
Section 3.2.2.
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Then the anchors need to properly forward the packets of the flows as
described in the FM behaviors and information elements (FM:1) in
Section 3.2.2.
If there are in-flight packets toward the old anchor while the MN is
moving to the new anchor, it may be necessary to buffer these packets
and then forward to the new anchor after the old anchor knows that
the new anchor is ready. Such are described in the FM behaviors and
information elements (FM:4) in Section 3.2.2.
4.2. IP prefix/address anchor switching 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 6.
Net1 Net2
+---------------+ +---------------+
|AR1 | |AR2 |
+---------------+ +---------------+
|CPA: | |CPA: |
|LM:IP1<-->IPa2 | |LM:IP1<-->IPa2 |
|---------------| |---------------|
|DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | move |anchors IP2,IP1|
|FM:DHCPv6-PD | =======> |FM:DHCPv6-PD |
+---------------+ +---------------+
+...............+ +---------------+
.MN(IP1) . move |MN(IP2,IP1) |
.flow(IP1,...) . =======> |flow(IP1,...) |
+...............+ +---------------+
Figure 6. 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 session continuity by moving the anchoring of the original
IP prefix/address of the flow to the new network. An example is in
the use of BGP UPDATE messages to change the forwarding table entries
as described in [I-D.mccann-dmm-flatarch] and also for 3GPP Evolved
Packet Core (EPC) network in [I-D.matsushima-stateless-uplane-vepc].
However, the response time and scalability of using a distributed
routing protocol to update forwarding tables may be controversial.
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Use of a centralized routing protocol with a centralized control
plane as described in Section 4.2.1 will be more scalable.
The location management provides information about which IP prefix
from an AR in the original network is being used by a flow in which
AR in a new network. Such information needs to be deleted or updated
when such flows have closed so that the IP prefix is no longer used
in a different network. The LM behaviors are described in
Section 3.2.1.
The FM functions are implemented through the DHCPv6-PD protocol.
Here the anchor behavior to properly forward the packets for a flow
as described in the FM behaviors and information elements FM:1 in
Section 3.2.2 is realized by changing the anchor with DHCPv6-PD and
also by reverting such changes later after the application has
already closed and when the DHCPv6-PD timer expires. If there are
in-flight packets toward the old anchor while the MN is moving to the
new anchor, it may be necessary to buffer these packets and then
forward to the new anchor after the old anchor knows that the new
anchor is ready. Such are described in the FM behaviors and
information elements FM:4 in Section 3.2.2. The anchors may also
need to discover each other as described in the FM behaviors and
information elements FM:2.
The security management function in the anchor node at a new network
must allow to assign the original IP prefix/address used by the
mobile node at the previous (original) network. As the assigned
original IP prefix/address is to be used in the new network, the
security management function in the anchor node must allow to
advertise the prefix of the original IP address and also allow the
mobile node to send and receive data packets with the original IP
address.
The security management function in the mobile node must allow to
configure the original IP prefix/address used at the previous
(original) network when the original IP prefix/address is assigned by
the anchor node in the new network. The security management function
in the mobile node also allows to use the original IP address for the
previous flow in the new network.
4.2.1. Centralized control plane
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
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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 configuration in Figures 1(a) and 1(b) in
Section 3.1 for which FM-CP and LM are centralized and FM-DP's are
distributed. applies here. Figure 7 shows its implementation where
LM is a binding between the original IP prefix/address of the flow
and the IP address of the new DPA, whereas FM uses the DHCPv6-PD
protocol.
Net1 Net2
+----------------------------------------------------------------------+
| CPA: |
| LM:IP1<-->IPa2 |
| FM-CP |
+----------------------------------------------------------------------+
+---------------+ +---------------+
|AR1 | |AR2 |
+---------------+ +---------------+
|DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | move |anchors IP2,IP1|
|FM:DHCPv6-PD | =======> |FM:DHCPv6-PD |
+---------------+ +---------------+
+...............+ +---------------+
.MN(IP1) . move |MN(IP2,IP1) |
.flow(IP1,...) . =======> |flow(IP1,...) |
+...............+ +---------------+
Figure 7. IP prefix/address anchor switching to the new network with
with LM and FM-CP in a centralized control plane whereas the FM-DP's
are distributed.
The call flow in Figure 8 shows that MN is allocated HNP1 when it
attaches to the p-AR. A flow running in MN may or may not need IP
mobility. If it does, it may continue to use the previous IP prefix.
If it does not, it may use a new IP prefix allocated from the new
network.
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MN p-AR n-AR DHCP Servers CN
|MN attaches to p-AR: | | | |
|acquire MN-ID and profile | | |
|--RS---------------->| | | |
|<----------RA(HNP1)--| | | |
| | | Allocate MN-HNP1 |
IP addr config | | | |
| | | | |
|<-Flow(IP1,IPcn,...)-+--------------------------------------------->|
| | | | |
|MN detach from p-AR | | | |
|MN attach to n-AR | | | |
| | | | |
|--RS------------------------------>| | |
| | | | |
| |------DHCPv6 release-------------->| |
| | | | |
| | |--DHCPv6 PD request->| |
| | |<-DHCPv6 PD reply--->| |
| | | | |
| forwarding table updates | |
| | | | |
|<--------------RA(HNP2,HNP1)-------| | |
| | | Allocate MN-HNP2 |
IP addr config | | | |
| | | | |
|<-Flow(IP1,IPcn,...)---------------+------------------------------->|
| | | | |
| Flow(IP1,IPcn,...) terminates | | |
| | | | |
| | DHCPv6-PD timeout | |
| | | | |
| forwarding table updates | |
| | | | |
| | | | |
|<-new Flow(IP2,IPcn,...)-----------+------------------------------->|
| | | | |
Figure 8. 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 p-AR to n-AR, the p-AR as a DHCP client may send
a DHCP release message to release the HNP1. It is now necessary for
n-AR 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
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provide its previous network prefix information by including it to
the RS message [I-D.jhlee-dmm-dnpp].
Knowing that MN is using HNP1, the n-AR sends to a DHCP server a
DHCPv6-PD request to move the HNP1 to n-AR. The server sends to n-AR
a DHCPv6-PD reply to move the HNP1. Then BGP route updates will take
place here.
In addition, the MN also needs a new HNP in the new network. The
n-AR may now send RA to n-AR, with prefix information that includes
HNP1 and HNP2. The MN may then continue to use IP1. In addition,
the MN is allocated the prefix HNP2 with which it may configure its
IP addresses. Now for flows using IP1, packets destined to IP1 will
be forwarded to the MN via n-AR.
As such flows have terminated and DHCP-PD has timed out, HNP1 goes
back to Net1. MN will then be left with HNP2 only, which it will use
when it now starts a new flow.
The anchor behavior to properly forward the packets for a flow as
described in the FM behaviors and information elements (FM:1) in
Section 3.2.2 is realized by changing the anchor with DHCPv6-PD and
undoing such changes later when its timer expires and the application
has already closed. With the anchors being separated in control and
data planes with LMs and FM-CP centralized in the same control plane,
messaging between anchors and the discovery of anchors become
internal to the control plane. However, the centralized FM-CP needs
to communicate with the distributed FM-DP as described as described
in the FM behaviors and information elements (FM:3). Such may be
realized by the appropriate messages in [I-D.ietf-dmm-fpc-cpdp].
Again, if there are in-flight packets toward the old anchor while the
MN is moving to the new anchor, it may be necessary to buffer these
packets and then forward to the new anchor after the old anchor knows
that the new anchor is ready. The corresponding FM behaviors and
information elements (FM:4) are however realized by the internal
behavior in the control plane together with signaling between the
control plane and distributed data plane.
4.2.2. Hierarchical network
The configuration for a hierarchical network is shown in Figures 1(c)
and 1(d) in Section 3.1. With centralized control and with a
centralized anchor, LM, CPA, CPN are co-located at the centralized
control, and there is an AR with the DPA function supporting multiple
forwarding switches (FW's) each with a DPN function. A mobility
event in this configuration involving change of FW but not of AR is
shown in Figure 9.
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Here the IP prefix allocated to the MN is anchored at the access
router (AR) supporting the old FW to which the MN was originally
attached as well as the new FW to which the MN has moved.
The realization of LM may bet 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:DHCPv6-PD |
+---------------+
+---------------+ +---------------+
|FW1 | |FW2 |
+---------------+ move +---------------+
|DPN(IPn1): | =======> |DPN(IPn2): |
+---------------+ +---------------+
+...............+ +---------------+
.MN(IP1) . move |MN(IP2) |
.flow(IP1,...) . =======> |flow(IP1,...) |
+...............+ +---------------+
Figure 9. Mobility without 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.
Here, the LM behaviors and information elements described in
Section 3.2.1 provides information of which IP prefix from its FW
needs to be used by a flow using which new FW. The anchor behaviors
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to properly forward the packets of a flow described in the FM
behaviors and information elements (FM:1) may be realized with PMIPv6
protocol ([I-D.korhonen-dmm-local-prefix]) or with AERO protocol
([I-D.templin-aerolink]) to tunnel between the AR and the FW.
4.2.3. Hierarchical network with anchoring change
The configuration for a hierarchical network is still shown in
Figures 1(c) and 1(d) in Section 3.1. Again, with centralized
control and with a centralized anchor, LM, CPA, CPN are co-located at
the centralized control, and there is an AR with the DPA function
supporting multiple forwarding switches (FW's) each with a DPN
function. However, the mobility event involving change of FW may
also involve a change of AR. Such configuration is shown in
Figure 10.
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 changing the IP prefix/address anchoring from AR1 to AR2 with the
mechanism as described in Section 4.2.1 and then forwarding the
packets with network hierarchy AR-FW as described in Section 4.2.2.
To change AR, AR1 acting as a DHCP-PD client may exchange message
with the DHCP server to release the prefix IP1. Meanwhile, AR2
acting as a DHCP-PD client may exchange message with the DHCP server
to delegate the prefix IP1 to AR2.
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Net1 Net2
+----------------------------------------------------------------------+
| CPA,CPN: |
| LM:IP1<-->IPa2,IPn2 |
| FM-CP |
+----------------------------------------------------------------------+
+---------------+
|Aggregate Point|
|---------------|
|FM, LM |
+---------------+
+---------------+ +---------------+
|AR1 | |AR2 |
+---------------+ +---------------+
|DPA(IPa1): | |DPA(IPa2): |
|anchors IP1 | move |anchors IP2,IP1|
|FM:DHCPv6-PD | =======> |FM:DHCPv6-PD |
+---------------+ +---------------+
+---------------+ +---------------+
|FW1 | |FW2 |
+---------------+ move +---------------+
|DPN(IPn1): | =======> |DPN(IPn2): |
+---------------+ +---------------+
+...............+ +---------------+
.MN(IP1) . move |MN(IP2,IP1) |
.flow(IP1,...) . =======> |flow(IP1,...) |
+...............+ +---------------+
Figure 10. 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.
5. Security Considerations
TBD
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6. IANA Considerations
This document presents no IANA considerations.
7. Contributors
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 Kaippallimil,
ChunShan Xiong, and Dapeng Liu.
8. References
8.1. Normative References
[I-D.ietf-dmm-fpc-cpdp]
Liebsch, M., Matsushima, S., Gundavelli, S., Moses, D.,
and L. Bertz, "Protocol for Forwarding Policy
Configuration (FPC) in DMM", draft-ietf-dmm-fpc-cpdp-03
(work in progress), March 2016.
[I-D.ietf-dmm-ondemand-mobility]
Yegin, A., Moses, D., Kweon, K., Lee, J., and J. Park, "On
Demand Mobility Management", draft-ietf-dmm-ondemand-
mobility-07 (work in progress), July 2016.
[I-D.jhlee-dmm-dnpp]
Lee, J. and Z. Yan, "Deprecated Network Prefix Provision",
draft-jhlee-dmm-dnpp-01 (work in progress), April 2016.
[I-D.korhonen-dmm-local-prefix]
Korhonen, J., Savolainen, T., and S. Gundavelli, "Local
Prefix Lifetime Management for Proxy Mobile IPv6", draft-
korhonen-dmm-local-prefix-01 (work in progress), 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", draft-liu-dmm-deployment-scenario-05 (work
in progress), October 2015.
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[I-D.matsushima-stateless-uplane-vepc]
Matsushima, S. and R. Wakikawa, "Stateless user-plane
architecture for virtualized EPC (vEPC)", draft-
matsushima-stateless-uplane-vepc-06 (work in progress),
March 2016.
[I-D.mccann-dmm-flatarch]
McCann, P., "Authentication and Mobility Management in a
Flat Architecture", draft-mccann-dmm-flatarch-00 (work in
progress), March 2012.
[I-D.mccann-dmm-prefixcost]
McCann, P. and J. Kaippallimalil, "Communicating Prefix
Cost to Mobile Nodes", draft-mccann-dmm-prefixcost-03
(work in progress), April 2016.
[I-D.seite-dmm-dma]
Seite, P., Bertin, P., and J. Lee, "Distributed Mobility
Anchoring", draft-seite-dmm-dma-07 (work in progress),
February 2014.
[I-D.sijeon-dmm-deployment-models]
Jeon, S. and Y. Kim, "Deployment Models for Distributed
Mobility Management", draft-sijeon-dmm-deployment-
models-03 (work in progress), July 2016.
[I-D.templin-aerolink]
Templin, F., "Asymmetric Extended Route Optimization
(AERO)", draft-templin-aerolink-67 (work in progress),
June 2016.
[I-D.wt-dmm-deployment-models]
Gundavelli, S., "DMM Deployment Models and Architectural
Considerations", draft-wt-dmm-deployment-models-00 (work
in progress), April 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, DOI 10.17487/RFC5213, August 2008,
<http://www.rfc-editor.org/info/rfc5213>.
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[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <http://www.rfc-editor.org/info/rfc6275>.
[RFC7333] Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J.
Korhonen, "Requirements for Distributed Mobility
Management", RFC 7333, DOI 10.17487/RFC7333, August 2014,
<http://www.rfc-editor.org/info/rfc7333>.
[RFC7429] Liu, D., Ed., Zuniga, JC., Ed., Seite, P., Chan, H., and
CJ. Bernardos, "Distributed Mobility Management: Current
Practices and Gap Analysis", RFC 7429,
DOI 10.17487/RFC7429, January 2015,
<http://www.rfc-editor.org/info/rfc7429>.
8.2. Informative References
[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.
Authors' Addresses
H Anthony Chan
Huawei Technologies
5340 Legacy Dr. Building 3
Plano, TX 75024
USA
Email: h.a.chan@ieee.org
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Xinpeng Wei
Huawei Technologies
Xin-Xi Rd. No. 3, Haidian District
Beijing, 100095
P. R. China
Email: weixinpeng@huawei.com
Jong-Hyouk Lee
Sangmyung University
708 Hannuri Building
Cheonan 330-720
Korea
Email: jonghyouk@smu.ac.kr
Seil Jeon
Instituto de Telecomunicacoes
Campus Universitario de Santiago
Aveiro 3810-193
Portugal
Email: seiljeon@av.it.pt
Fred L. Templin
Boeing Research and Technology
P.O. Box 3707
Seattle, WA 98124
USA
Email: fltemplin@acm.org
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