Network Working Group H. Yokota
Internet-Draft KDDI Lab
Intended status: Standards Track K. Chowdhury
Expires: November 15, 2010 R. Koodli
Cisco Systems
B. Patil
Nokia
F. Xia
Huawei USA
May 14, 2010
Fast Handovers for Proxy Mobile IPv6
draft-ietf-mipshop-pfmipv6-14.txt
Abstract
Mobile IPv6 (MIPv6) [RFC3775] provides a mobile node with IP mobility
when it performs a handover from one access router to another and
fast handovers for Mobile IPv6 (FMIPv6) [RFC5568] are specified to
enhance the handover performance in terms of latency and packet loss.
While MIPv6 (and FMIPv6 as well) requires the participation of the
mobile node in the mobility-related signaling, Proxy Mobile IPv6
(PMIPv6) [RFC5213] provides IP mobility to nodes that either have or
do not have MIPv6 functionality without such involvement.
Nevertheless, the basic performance of PMIPv6 in terms of handover
latency and packet loss is considered not any different from that of
MIPv6.
When the fast handover is considered in such an environment, several
modifications are needed to FMIPv6 to adapt to the network-based
mobility management. This document specifies the usage of Fast
Mobile IPv6 (FMIPv6) when Proxy Mobile IPv6 is used as the mobility
management protocol. Necessary extensions are specified for FMIPv6
to support the scenario when the mobile node does not have IP
mobility functionality and hence is not involved with either MIPv6 or
FMIPv6 operations.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 15, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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material may not have granted the IETF Trust the right to allow
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Without obtaining an adequate license from the person(s) controlling
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not be created outside the IETF Standards Process, except to format
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Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Proxy-based FMIPv6 Protocol Overview . . . . . . . . . . . . . 7
4.1. Protocol Operation . . . . . . . . . . . . . . . . . . . . 8
4.2. Inter-AR Tunneling Operation . . . . . . . . . . . . . . . 15
4.3. IPv4 Support Considerations . . . . . . . . . . . . . . . 17
5. PMIPv6-related Fast Handover Issues . . . . . . . . . . . . . 18
5.1. Manageability Considerations . . . . . . . . . . . . . . . 18
5.2. Expedited Packet Transmission . . . . . . . . . . . . . . 18
6. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 20
6.1. Mobility Header . . . . . . . . . . . . . . . . . . . . . 20
6.1.1. Handover Initiate (HI) . . . . . . . . . . . . . . . . 20
6.1.2. Handover Acknowledge (HAck) . . . . . . . . . . . . . 22
6.2. Mobility Options . . . . . . . . . . . . . . . . . . . . . 24
6.2.1. Context Request Option . . . . . . . . . . . . . . . . 24
6.2.2. Local Mobility Anchor Address (LMAA) Option . . . . . 25
6.2.3. Mobile Node Link-local Address Interface
Identifier (MN LLA-IID) Option . . . . . . . . . . . . 26
6.2.4. Home Network Prefix Option . . . . . . . . . . . . . . 27
6.2.5. Link-local Address Option . . . . . . . . . . . . . . 27
6.2.6. GRE Key Option . . . . . . . . . . . . . . . . . . . . 27
6.2.7. IPv4 Address Option . . . . . . . . . . . . . . . . . 27
6.2.8. Vendor-Specific Mobility Option . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.1. Normative References . . . . . . . . . . . . . . . . . . . 32
10.2. Informative References . . . . . . . . . . . . . . . . . . 32
Appendix A. Applicable Use Cases . . . . . . . . . . . . . . . . 33
A.1. PMIPv6 Handoff Indication . . . . . . . . . . . . . . . . 33
A.2. Local Routing . . . . . . . . . . . . . . . . . . . . . . 33
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 41
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1. Requirements notation
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].
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2. Introduction
Proxy Mobile IPv6 (PMIPv6) [RFC5213] provides IP mobility to a mobile
node that does not support Mobile IPv6 [RFC3775] mobile node
functionality. A proxy agent in the network performs the mobility
management signaling on behalf of the mobile node. This model
transparently provides mobility for nodes within a PMIPv6 domain.
Nevertheless, the basic performance of PMIPv6 in terms of handover
latency and packet loss is considered not any different from that of
Mobile IPv6.
Fast Handovers for Mobile IPv6 (FMIPv6) [RFC5568] describes the
protocol to reduce the handover latency for Mobile IPv6 by allowing a
mobile node to send packets as soon as it detects a new subnet link
and by delivering packets to the mobile node as soon as its
attachment is detected by the new access router. This document
extends FMIPv6 for Proxy MIPv6 operation to minimize handover delay
and packet loss as well as to transfer network-resident context for a
PMIPv6 handover. [RFC5568] is normative for this document, except
where this document specifies new or revised functions and messages.
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3. Terminology
This document reuses terminology from [RFC5213], [RFC5568] and
[RFC3775]. The following terms and abbreviations are additionally
used in this document.
Access Network (AN):
A network composed of link-layer access devices such as access
points or base stations providing access to a MAG (Mobile Access
Gateway) connected to it.
Previous Access Network (P-AN):
The access network to which the Mobile Node (MN) is attached
before handover.
New Access Network (N-AN):
The access network to which the Mobile Node (MN) is attached
after handover.
Previous Mobile Access Gateway (PMAG):
The MAG that manages mobility related signaling for the mobile
node before handover. In this document, the MAG and the Access
Router are co-located.
New Mobile Access Gateway (NMAG):
The MAG that manages mobility related signaling for the mobile
node after handover. In this document, the MAG and the Access
Router (AR) are co-located.
Local Mobility Anchor (LMA):
The topological anchor point for the mobile node's home network
prefix(es) and the entity that manages the mobile node's binding
state. This specification does not alter any capability or
functionality defined in [RFC5213].
Handover indication:
A generic signaling message, sent from the P-AN to the PMAG that
indicates a mobile node's handover. While this signaling is
dependent on the access technology, it is assumed that Handover
indication can carry the information to identify the mobile node
and to assist the PMAG to resolve the NMAG and the new access
point or base station to which the mobile node is moving to.
The details of this message are outside the scope of this
document.
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4. Proxy-based FMIPv6 Protocol Overview
This specification describes fast handover protocols for the network-
based mobility management protocol called Proxy Mobile IP (PMIPv6)
[RFC5213]. The core functional entities defined in PMIPv6 are the
Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG). The
LMA is the topological anchor point for the mobile node's home
network prefix(es). The MAG acts as an access router (AR) for the
mobile node and performs the mobility management procedures on its
behalf. The MAG is responsible for detecting the mobile node's
movements to and from the access link and for initiating binding
registrations to the mobile node's local mobility anchor. If the
MAGs can be informed of the detachment and/or attachment of the
mobile node in a timely manner via e.g., the lower layer signaling,
it will become possible to optimize the handover procedure, which
involves establishing a connection on the new link and signaling
between mobility agents, compared to the baseline specification of
PMIPv6.
In order to further improve the performance during the handover, this
document specifies a bi-directional tunnel between the Previous MAG
(PMAG) and the New MAG (NMAG) to tunnel packets meant for the mobile
node. In order to enable the NMAG to send the Proxy Binding Update
(PBU), the Handover Initiate (HI) and Handover Acknowledge (HAck)
messages in [RFC5568] are extended for context transfer, in which
parameters such as mobile node's Network Access Identifier (NAI),
Home Network Prefix (HNP), IPv4 Home Address, are transferred from
the PMAG. New flags 'P' and 'F' are defined for the HI and HAck
messages to distinguish from those in [RFC5568] and to request packet
forwarding, respectively.
In this document, the Previous Access Router (PAR) and New Access
Router (NAR) are interchangeable with the PMAG and NMAG,
respectively. The reference network is illustrated in Figure 1. The
access networks in the figure (i.e., P-AN and N-AN) are composed of
Access Points (APs) defined in [RFC5568], which are often referred to
as base stations in cellular networks.
Since a mobile node is not directly involved with IP mobility
protocol operations, it follows that the mobile node is not directly
involved with fast handover procedures either. Hence, the messages
involving the mobile node in [RFC5568] are not used when PMIPv6 is in
use. More specifically, the Router Solicitation for Proxy
Advertisement (RtSolPr), the Proxy Router Advertisement (PrRtAdv),
Fast Binding Update (FBU), Fast Binding Acknowledgment (FBack) and
the Unsolicited Neighbor Advertisement (UNA) messages are not
applicable in the PMIPv6 context. A MAG that receives a RtSolPr or
FBU message from a mobile node SHOULD behave as if they do not
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implement FMIPv6 as defined in [RFC5568] at all, continuing to
operate according to this specification within the network, or
alternatively, start serving that particular mobile node as specified
in [RFC5568].
+----------+
| LMA |
| |
+----------+
/ \
/ \
/ \
+........../..+ +..\..........+
. +-------+-+ .______. +-+-------+ .
. | PMAG |()_______)| NMAG | .
. | (PAR) | . . | (NAR) | .
. +----+----+ . . +----+----+ .
. | . . | .
. ___|___ . . ___|___ .
. / \ . . / \ .
. ( P-AN ) . . ( N-AN ) .
. \_______/ . . \_______/ .
. | . . | .
. +----+ . . +----+ .
. | MN | ----------> | MN | .
. +----+ . . +----+ .
+.............+ +.............+
Figure 1: Reference network for fast handover
4.1. Protocol Operation
There are two modes of operation in FMIPv6 [RFC5568]. In the
predictive mode of fast handover, a bi-directional tunnel between the
PMAG (PAR) and NMAG (NAR) is established prior to the mobile node's
attachment to the NMAG. In the reactive mode, this tunnel
establishment takes place after the mobile node attaches to the NMAG.
In order to alleviate the packet loss during a mobile node's handover
(especially when the mobile node is detached from both links), the
downlink packets for the mobile node need to be buffered either at
the PMAG or NMAG, depending on when the packet forwarding is
performed. It is hence REQUIRED that all MAGs have the capability
and enough resources to buffer packets for the mobile nodes
accommodated by them. The buffer size to be prepared and the rate at
which buffered packets are drained are addressed in Section 5.4 of
[RFC5568]. Note that the protocol operation specified in the
document is transparent to the local mobility anchor (LMA), hence
there is no new functional requirement or change on the LMA.
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Unlike MIPv6, the mobile node in the PMIPv6 domain is not involved
with IP mobility signaling; therefore, in order for the predictive
fast handover to work effectively, it is REQUIRED that the mobile
node is capable of reporting lower-layer information to the AN at a
short enough interval, and the AN is capable of sending the Handover
indication to the PMAG at an appropriate timing. The sequence of
events for the predictive fast handover are illustrated in Figure 2.
PMAG NMAG
MN P-AN N-AN (PAR) (NAR) LMA
| | | | | |
(a) |--Report-->| | | | |
| | | | | |
| | Handover | | |
(b) | |------indication------>| | |
| | | | | |
| | | | | |
(c) | | | |----HI---->| |
| | | | | |
| | | | | |
(d) | | | |<---HAck---| |
| | | | | |
| | | | | |
| | | |HI/HAck(optional) |
(e) | | | |<- - - - ->| |
| | | #=|<===================|
(f) | | | #====DL data=>| |
| Handover | Handover | | |
(g) |<-command--|<------command---------| | |
~~~ | | | | |
~~~ | | | | |
| MN-AN connection | AN-MAG connection | |
(h) |<---establishment---->|<----establishment----->| |
| | | (substitute for UNA) | |
| | | | | |
(i) |<==================DL data=====================| |
| | | | | |
(j) |===================UL data====================>|=# |
| | | #=|<============# |
| | | #=====================>|
/ | | | | | | \
|(k) | | | | |--PBU-->| |
| | | | | | | |
|(l) | | | | |<--PBA--| |
| |<==================DL data=====================|<=======| |
| | | | | | | |
\ |===================UL data====================>|=======>| /
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Figure 2: Predictive fast handover for PMIPv6 (PMAG initiated)
The detailed descriptions are as follows:
(a) The mobile node detects that a handover is imminent and reports
the identifier of itself (MN ID) and the New Access Point
Identifier (New AP ID) [RFC5568] to which the mobile node is
most likely to move. The MN ID could be the NAI, Link-layer
address, or any other suitable identifier, but the MAG SHOULD be
able to map any access specific identifier to the NAI as the MN
ID. In some cases, the previous access network (P-AN) will
determine the New AP ID for the mobile node. This step is
access technology specific and details are outside the scope of
this document.
(b) The previous access network, to which the mobile node is
currently attached, indicates the handover of the mobile node to
the previous mobile access gateway (PMAG), with the MN ID and
New AP ID. Detailed definition and specification of this
message are outside the scope of this document.
(c) The previous MAG derives the new mobile access gateway (NMAG)
from the New AP ID, which is a similar process to that of
constructing an [AP ID, AR-Info] tuple in [RFC5568]. The
previous MAG then sends the Handover Initiate (HI) message to
the new MAG. The HI message MUST have the P flag set and
include the MN ID, the HNP(s) and the address of the local
mobility anchor that is currently serving the mobile node. If
there is a valid (non-zero) MN Link-layer Identifier (MN LL-ID),
that information MUST also be included. With some link layers,
the MN Link-local Address IID (MN LLA-IID) can also be included
(see Section 6.2.3).
(d) The new MAG sends the Handover Acknowledge (HAck) message back
to the previous MAG with the P flag set.
(e) If it is preferred that the timing of buffering or forwarding
should be later than step (c), the new MAG MAY optionally
request the previous MAG at a later and appropriate time to
buffer or forward packets by setting U flag [RFC5568] or F flag
in the HI message, respectively.
(f) If the F flag is set in the previous step, a bi-directional
tunnel is established between the previous MAG and new MAG and
packets destined for the mobile node are forwarded from the
previous MAG to the new MAG over this tunnel. After
decapsulation, those packets MAY be buffered at the new MAG. If
the connection between the new access network and new MAG has
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already been established, those packets MAY be forwarded towards
the new access network, which then becomes responsible for them
(e.g., buffering or delivering depending on the condition of the
mobile node's attachment); this is access technology specific.
(g) When handover is ready on the network side, the mobile node is
triggered to perform handover to the new access network. This
step is access technology specific and details are outside the
scope of this document.
(h) The mobile node establishes a physical link connection with the
new access network (e.g., radio channel assignment), which in
turn triggers the establishment of a link-layer connection
between the new access network and new MAG if not yet
established. An IP layer connection setup may be performed at
this time (e.g., PPP IPv6CP) or at a later time (e.g., stateful
or stateless auto address configuration). This step can be a
substitute for the Unsolicited Neighbor Advertisement (UNA) in
[RFC5568]. If the new MAG acquires a valid new MN LL-ID via the
new access network and a valid old MN LL-ID from the previous
MAG at step (c), these IDs SHOULD be compared to determine
whether the same interface is used before and after handover.
When the connection between the mobile node and new MAG is PPP
and the same interface is used for the handover, the new MAG
SHOULD confirm that the same interface identifier is used for
the mobile node's link-local address (this is transferred from
previous MAG using the MN LLA-IID option at step (c), and sent
to the mobile node during the Configure-Request/Ack exchange).
(i) The new MAG starts to forward packets destined for the mobile
node via the new access network.
(j) The uplink packets from the mobile node are sent to the new MAG
via the new access network and the new MAG forwards them to the
previous MAG. The previous MAG then sends the packets to the
local mobility anchor that is currently serving the mobile node.
(k) The new MAG sends the Proxy Binding Update (PBU) to the local
mobility anchor, whose address is provided in (c). Steps (k)
and (l) are not part of the fast handover procedure, but shown
for reference.
(l) The local mobility anchor sends back the Proxy Binding
Acknowledgment (PBA) to the new MAG. From this time on, the
packets to/from the mobile node go through the new MAG instead
of the previous MAG.
According to Section 4 of [RFC5568], the previous MAG establishes a
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binding between the Previous Care-of Address (PCoA) and New Care-of
Address (NCoA) to forward packets for the mobile node to the new MAG,
and the new MAG creates a proxy neighbor cache entry to receive those
packets for the NCoA before the mobile node arrives. In the case of
PMIPv6, however, the only address that is used by the mobile node is
MN-HoA (Mobile Node's Home Address), so the PMAG forwards mobile
node's packets to the NMAG instead of the NCoA. The NMAG then simply
decapsulates those packets and delivers them to the mobile node.
FMIPv4 [RFC4988] specifies forwarding when the mobile node uses the
home address as its on-link address rather than the care-of address.
The usage in PMIPv6 is similar to that in FMIPv4, where the
address(es) used by the mobile node is/are based on its HNP(s).
Since the NMAG can obtain the Link-layer address (MN LL-ID) and
HNP(s) via the HI message (also the interface identifier of the
mobile node's link-local address (MN LLA-ID) if available), it can
create a neighbor cache entry for the Link-local Address and the
routes for the whole HNP(s) even before the mobile node performs
Neighbor Discovery. For the uplink packets from the mobile node
after handover in (j), the NMAG forwards the packets to the PMAG
through the tunnel established in step (f). The PMAG then
decapsulates and sends them to the local mobility anchor.
The timing of the context transfer and that of packet forwarding may
be different. Thus, a new flag 'F' and Option Code values for it in
the HI and HAck messages are defined to request forwarding. To
request buffering, 'U' flag has already been defined in [RFC5568].
If the PMAG receives the HI message with the F flag set, it starts
forwarding packets for the mobile node. The HI message with the U
flag set MAY be sent earlier if the timing of buffering is different
from that of forwarding. If packet forwarding is completed, the PMAG
MAY send the HI message with the F flag set and the Option Code value
being 2. By this message, the ARs on both ends can tear down the
forwarding tunnel synchronously.
The IP addresses in the headers of those user packets are summarized
below:
In Step (f),
Inner source address: IP address of the correspondent node
Inner destination address: HNP or Mobile Node's IPv4 Home
Address (IPv4-MN-HoA)
Outer source address: IP address of the PMAG
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Outer destination address: IP address of the NMAG
In Step (i),
Source address: IP address of the correspondent node
Destination address: HNP or IPv4-MN-HoA
In Step (j),
- from the mobile node to the NMAG,
Source address: HNP or IPv4-MN-HoA
Destination address: IP address of the correspondent node
- from the NMAG to the PMAG,
Inner source address: HNP or IPv4-MN-HoA
Inner destination address: IP address of the correspondent node
Outer source address: IP address of the NMAG
Outer destination address: IP address of the PMAG
- from the PMAG to the LMA,
Inner source address: HNP or IPv4-MN-HoA
Inner destination address: IP address of the correspondent node
Outer source address: IP address of the PMAG
Outer destination address: IP address of the LMA
In the case of the reactive handover for PMIPv6, since the mobile
node does not send either the FBU or UNA, it would be more natural
that the NMAG sends the HI to the PMAG after the mobile node has
moved to the new link. The NMAG then needs to obtain the information
of the PMAG beforehand. Such information could be provided, for
example, by the mobile node sending the AP-ID on the old link and/or
by the lower-layer procedures between the P-AN and N-AN. The exact
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method is not specified in this document. Figure 3 illustrates the
reactive fast handover procedures for PMIPv6, where the bi-
directional tunnel establishment is initiated by the NMAG.
PMAG NMAG
MN P-AN N-AN (PAR) (NAR) LMA
| | | | | |
(a) ~~~ | | | | |
~~~ | | | | |
| MN-AN connection | AN-MAG connection | |
(b) |<--establishment-->|<-------establishment------>| |
| | |(substitute for UNA and FBU)| |
| | | | | |
| | | | | |
(c) | | | |<-----HI-------| |
| | | | | |
| | | | | |
(d) | | | |-----HAck----->| |
| | | | | |
| | | | | |
(e) | | | #=|<=======================|
| | | #================>|=# |
|<====================DL data======================# |
| | | | | |
(f) |=====================UL data===================>|=# |
| | | #=|<================# |
| | | #=========================>|
| | | | | |
/ | | | | | | \
|(g) | | | | |--PBU-->| |
| | | | | | | |
|(h) | | | | |<--PBA--| |
| |<====================DL data====================|<=======| |
| | | | | | | |
\ |=====================UL data===================>|=======>| /
Figure 3: Reactive fast handover for PMIPv6 (NMAG initiated)
The detailed descriptions are as follows:
(a) The mobile node undergoes handover from the previous access
network to the new access network.
(b) The mobile node establishes a connection (e.g., radio channel)
with the new access network, which triggers the establishment of
the connection between the new access network and new MAG. The
MN ID is transferred to the new MAG at this step for the
subsequent procedures. The AP-ID on the old link (Old AP ID),
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which will be provided by either the mobile node or the new
access network, is also transferred to the new MAG to help
identify the previous MAG on the new link. This can be regarded
as a substitute for the UNA and FBU.
(c) The new MAG sends the HI to the previous MAG. The HI message
MUST have the P flag set and include the MN ID. The Context
Request Option MAY be included to request additional context
information on the mobile node to the previous MAG.
(d) The previous MAG sends the HAck back to the new MAG with the P
flag set. The HAck message MUST include the HNP(s) and/or IPv4-
MN-HoA that is corresponding to the MN ID in the HI message and
SHOULD include the MN LL-ID, only if it is valid (non zero), and
the local mobility anchor address that is currently serving the
mobile node. The context information requested by the new MAG
MUST be included. If the requested context is not available for
some reason, the previous MAG MUST return the HAck with the Code
value 131. If the F flag is set in the HI at step (c) and
forwarding is nevertheless not executable for some reason, the
previous MAG MUST return the HAck with the Code value 132.
(e) If the F flag in the HI is set at step (c), a bi-directional
tunnel is established between the previous MAG and new MAG and
packets destined for the mobile node are forwarded from the
previous MAG to the new MAG over this tunnel. After
decapsulation, those packets are delivered to the mobile node
via the new access network.
(f) The uplink packets from the mobile node are sent to the new MAG
via the new access network and the new MAG forwards them to the
previous MAG. The previous MAG then sends the packets to the
local mobility anchor that is currently serving the mobile node.
Steps (g)-(h) are the same as (k)-(l) in the predictive fast handover
procedures.
In step (c), the IP address of the PMAG needs to be resolved by the
NMAG to send the HI to the PMAG. This information may come from the
N-AN or some database that the NMAG can access.
4.2. Inter-AR Tunneling Operation
When the PMAG (PAR) or NMAG (NAR), depending on the fast handover
mode, receives the HI message with the F flag set, it prepares to
send/receive the mobile node's packets to/from the other MAG and
returns the HAck message with the same sequence number. The both
MAGs SHOULD support the following encapsulation modes for the user
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packets, which are also defined for the tunnel between the local
mobility anchor and MAG:
o IPv4-or-IPv6-over-IPv6 [IPv4PMIPv6]
o IPv4-or-IPv6-over-IPv4 [IPv4PMIPv6]
o IPv4-or-IPv6-over-IPv4-UDP [IPv4PMIPv6]
o TLV-header UDP tunneling [GREKEY]
o GRE tunneling with or without GRE key(s) [GREKEY]
The PMAG and the NMAG MUST use the same tunneling mechanism for the
data traffic tunneled between them. The encapsulation mode to be
employed SHOULD be configurable. It is RECOMMENDED that:
1. As the default behavior, the inter-MAG tunnel uses the same
encapsulation mechanism as that for the PMIPv6 tunnel between the
local mobility anchor and the MAGs. The PMAG and NMAG
automatically start using the same encapsulation mechanism
without a need for a special configuration on the MAGs or a
dynamic tunneling mechanism negotiation between them.
2. Configuration on the MAGs can override the default mechanism
specified in #1 above. The PMAG and NMAG MUST be configured with
the same mechanism and this configuration is most likely to be
uniform throughout the PMIPv6 domain. If the packets on the
PMIPv6 tunnel cannot be uniquely mapped on to the configured
inter-MAG tunnel, this scenario is not applicable and scenario #3
below SHOULD directly be applied.
3. An implicit or explicit tunnel negotiation mechanism between the
MAGs can override the default mechanism specified in #1 above.
The employed tunnel negotiation mechanism is outside the scope of
this document.
The necessary information MUST be transferred in the HI/HAck messages
to distinguish mobile node's packets for forwarding in advance or at
this time. Such information includes the HNP(s) (or IPv4-MN-HoA)
and/or GRE key(s). In the case of GRE tunneling with GRE keys being
used, for each mobility session, the NMAG selects the GRE key for the
downlink packets and the PMAG selects the GRE key for the uplink
packets. These GRE keys are exchanged between the PMAG and the NMAG
using the GRE Key option as described in [GREKEY], e.g., In the case
of the reactive mode as shown in Figure 3, the DL GRE key is
communicated in the HI message while the UL GRE key is sent in the
HAck message. For the downlink packets, the PMAG redirects mobile
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node's packets from the local mobility anchor towards the NMAG and if
the mobile node is ready to receive those packets or the N-AN can
handle them regardless of the state of the mobile node, the NMAG
SHOULD immediately send them towards the N-AN; otherwise it SHOULD
buffer them until the mobile node is ready. For the uplink packets,
the NMAG SHOULD reverse-tunnel them from the mobile node towards the
PMAG and the PMAG sends them to the local mobility anchor.
When the PMAG or NMAG receives the HI message with the U flag set, it
prepares to buffer the mobile node's packets and returns the HAck
message with the same sequence number. It MUST be followed by
another HI message with the F flag set at an appropriate time to
forward the buffered packets.
If the MAG that received the HI message encounters an erroneous
situation (e.g., insufficient buffer space), it SHOULD immediately
send the HAck message with the cause of the error and cancel all
tunneling operation.
4.3. IPv4 Support Considerations
The motivation and usage scenarios of IPv4 protocol support by PMIPv6
are described in [IPv4PMIPv6]. The scope of IPv4 support covers the
following two features:
o IPv4 Home Address Mobility Support, and
o IPv4 Transport Support.
As for IPv4 Home Address Mobility Support, the mobile node acquires
IPv4 Home Address (IPv4-MN-HoA) and in the case of handover, the PMAG
needs to transfer IPv4-MN-HoA to the NMAG, which is the inner
destination address of the packets forwarded on the downlink. For
this purpose, IPv4 Address Option described in Section 6.2.7 is used.
In order to provide IPv4 Transport Support, the NMAG needs to know
the IPv4 address of the local mobility anchor (IPv4-LMAA) to send
PMIPv6 signaling messages to the local mobility anchor in the IPv4
transport network. For this purpose, a new option called LMA Address
(LMAA) Option is defined in Section 6.2.2 so as to convey IPv4-LMAA
from the PMAG to NMAG.
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5. PMIPv6-related Fast Handover Issues
5.1. Manageability Considerations
This specification does not require any additional IP-level
functionality on the local mobility anchor and the mobile node
running in the PMIPv6 domain. A typical network interface that the
mobile node could be assumed to have is one with the cellular
network, where the network controls the movement of the mobile node.
Different types of interfaces could be involved such as different
generations (3G and 3.9G) or different radio access systems. This
specification supports a mobile node with the single radio mode,
where only one interface is active at any given time. The assigned
IP address is preserved whether the physical interface changes or not
and the mobile node can identify which interface should be used if
there are multiple ones.
5.2. Expedited Packet Transmission
The protocol specified in this document enables the NMAG to obtain
parameters which would otherwise be available only by communicating
with the local mobility anchor. For instance, the HNP(s) and/or
IPv4-MN-HoA of a mobile node are made available to the NMAG through
context transfer. This allows the NMAG to perform some procedures
that may be beneficial. The NMAG, for example, SHOULD send a Router
Advertisement (RA) with prefix information to the mobile node as soon
as its link attachment is detected (e.g., via receipt of a Router
Solicitation message). Such an RA is recommended, for example, in
scenarios where the mobile node uses a new radio interface while
attaching to the NMAG; since the mobile node does not have
information regarding the new interface, it will not be able to
immediately send packets without first receiving an RA with HNP(s).
Especially, in the reactive fast handover, the NMAG gets to know the
HNP(s) assigned to the mobile node on the previous link at step (d)
in Figure 3. In order to reduce the communication disruption time,
the NMAG SHOULD expect the mobile node to keep using the same HNP and
to send uplink packets before that step upon the mobile node's
request. However, if the HAck from the PMAG returns a different HNP
or the subsequent PMIPv6 binding registration for the HNP fails for
some reason, then the NMAG MUST withdraw the advertised HNP by
sending another RA with zero prefix lifetime for the HNP in question.
This operation is the same as described in Section 6.12 of [RFC5213].
The protocol specified in this document is applicable regardless of
whether link-layer addresses are used between a mobile node and its
MAG. A mobile node should be able to continue sending packets on the
uplink even when it changes link. When link-layer addresses are
used, the mobile node performs Neighbor Unreachability Detection
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(NUD) [RFC4861], after attaching to a new link, probing the
reachability of its default router. The new router should respond to
the NUD probe, providing its link-layer address in the solicited
Neighbor Advertisement, which is common in the PMIPv6 domain.
Implementations should allow the mobile node to continue to send
uplink packets while it is performing NUD.
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6. Message Formats
This document defines new Mobility Header messages for the extended
HI and Hack and new mobility options for conveying context
information.
6.1. Mobility Header
6.1.1. Handover Initiate (HI)
This section defines extensions to the HI message in [RFC5568]. The
format of the Message Data field in the Mobility Header is as
follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+
| Sequence # |
+-+-+-+-+-------+---------------+-------------------------------+
|S|U|P|F|Resv'd | Code | |
+-+-+-+-+-------+---------------+ |
| |
. .
. Mobility options .
. .
| |
+---------------------------------------------------------------+
(Note:P=1)
IP Fields:
Source Address
The IP address of PMAG or NMAG
Destination Address
The IP address of the peer MAG
Message Data:
Sequence # Same as [RFC5568].
S flag Defined in [RFC5568] and MUST be set to zero in this
specification.
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U flag Buffer flag. Same as [RFC5568].
P flag Proxy flag. Used to distinguish the message from that
defined in [RFC5568] and MUST be set in all new message
formats defined in this document when using this protocol
extension.
F flag Forwarding flag. Used to request to forward the packets
for the mobile node.
Reserved Same as [RFC5568].
Code [RFC5568] defines this field and its values 0 and 1. In
this specification, with the P flag set, this field can
be set to zero by default or the following values:
2: Indicate the completion of forwarding
3: All available context transferred
Code value 3 is set when the transfer of all necessary
context information is completed with this message. This
Code value is used in both cases where the context
information is fragmented into several pieces and the
last fragment is contained in this message and where the
whole information is transferred in one piece.
Mobility options:
This field contains one or more mobility options, whose encoding and
formats are defined in [RFC3775].
Required option
In order to uniquely identify the target mobile node, the
mobile node Identifier MUST be contained in the Mobile Node
Identifier Option.
The transferred context MUST be for one mobile node per message. In
addition, the NMAG can request necessary mobility options by the
Context Request Option defined in this document.
Context Request Option
This option MAY be present to request context information
typically by the NMAG to the PMAG in the NMAG-initiated fast
handover.
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6.1.2. Handover Acknowledge (HAck)
This section defines extensions to the HAck message in[RFC5568]. The
format of the Message Data field in the Mobility Header is as
follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+
| Sequence # |
+-+-+-+---------+---------------+-------------------------------+
|U|P|F|Reserved | Code | |
+-+-+-+---------+---------------+ |
| |
. .
. Mobility options .
. .
| |
+---------------------------------------------------------------+
(Note:P=1)
IP Fields:
Source Address
Copied from the destination address of the
Handover Initiate message to which this message
is a response.
Destination Address
Copied from the source address of the Handover
Initiate message to which this message is a
response.
Message Data:
The usages of Sequence # and Reserved fields are exactly the same as
those in [RFC5568].
U flag Same as defined in Section 6.1.1.
P flag Used to distinguish the message from that defined in
[RFC5568] and MUST be set in all new message formats
defined in this document when using this protocol
extension.
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F flag Same as defined in Section 6.1.1.
Code
Code values 0 through 4 and 128 through 130 are defined
in [RFC5568]. When the P flag is set, the meaning of
Code value 0 is as defined in this specification, 128
through 130 are reused, and 5, 6, 131 and 132 are newly
defined.
0: Handover Accepted or Successful
5: Context Transfer Accepted or Successful
6: All available Context Transferred
128: Handover Not Accepted, reason unspecified
129: Administratively prohibited
130: Insufficient resources
131: Requested Context Not Available
132: Forwarding Not Available
Mobility options:
This field contains one or more mobility options, whose encoding and
formats are defined in [RFC3775]. The mobility option that uniquely
identifies the target mobile node MUST be copied from the
corresponding HI message and the transferred context MUST be for one
mobile node per message.
Required option(s) All the context information requested by the
Context Request Option in the HI message SHOULD be present
in the HAck message. The other cases are described below.
In the case of the PMAG-initiated fast handover, when the PMAG sends
the HI message to the NMAG with the context information and the NMAG
successfully receives it, the NMAG returns the HAck message with Code
value 5. In the case of the NMAG-initiated fast handover, when the
NMAG sends the HI message to the PMAG with or without Context Request
Option, the PMAG returns the HAck message with the requested or
default context information (if any). If all available context
information is transferred, the PMAG sets the Code value in the HAck
message to 6. If more context information is available, the PMAG
sets the Code value in the HAck to 5 and the NMAG MAY send new HI
message(s) to retrieve the rest of the available context information.
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If none of the requested context information is available, the PMAG
returns the HAck message with Code value 131 without any context
information.
6.2. Mobility Options
6.2.1. Context Request Option
This option is sent in the HI message to request context information
on the mobile node. If a default set of context information is
defined and always sufficient, this option is not used. This option
is more useful to retrieve additional or dynamically selected context
information.
Context Request Option is typically used for the reactive (NMAG-
initiated) fast handover mode to retrieve the context information
from the PMAG. When this option is included in the HI message, all
the requested context information SHOULD be included in the HAck
message in the corresponding mobility option(s) (e.g., HNP, LMAA or
MN LL-ID mobility options).
The default context information to request is the Home Network Prefix
Option. If the Mobile Node link-layer is available and used, the
Mobile Node Link-layer Identifier Option MUST also be requested.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+---------------+---------------+
| Option-Type | Option-Length | Reserved |
+---------------+---------------+-------------------------------+
| Req-type-1 | Req-length-1 | Req-type-2 | Req-length-2 |
+---------------------------------------------------------------+
| Req-type-3 | Req-length-3 | Req-option-3 |
+---------------------------------------------------------------+
| ... |
Option-Type TBD1
Option-Length The length in octets of this option, not including the
Option Type and Option Length fields.
Reserved This field is unused. It MUST be initialized to zero
by the sender and MUST be ignored by the receiver.
Req-type-n The type value for the n'th requested option.
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Req-length-n The length of the n'th requested option excluding the
Req-type-n and Req-length-n fields.
Req-option-n The optional data to uniquely identify the requested
context for the n'th requested option.
In the case where there are only Req-type-n and Req-length-n fields,
the value of the Req-length-n is set to zero. If additional
information besides the Req-type-n is necessary to uniquely specify
the requested context, such information follows after the
Req-length-n. For example, when the requested contexts start with
the HNP Option (type=22), the MN Link-layer ID Option (type=25) and
the Vendor-Specific Option (type=19), the required option format
looks as follows:
| ... |
+---------------+---------------+---------------+---------------+
|Option-Type=CRO| Option-Length | Reserved |
+---------------+---------------+---------------+---------------+
| Req-type-N=22 | Req-length-N=0| Req-type-N=25 | Req-length-N=0|
+---------------+---------------+-------------------------------+
| Req-type-N=19 | Req-length-N=5| Vendor-ID |
+-------------------------------+---------------+---------------+
| Vendor-ID | Sub-Type | |
+-----------------------------------------------+ |
| ... |
The first two options can uniquely identify the requested contexts
(i.e., the HNP and MN Link-layer ID) by the Req-type, so the Req-
length is set to zero; however, the subsequent Vendor-Specific Option
further needs the Vendor-ID and Sub-type to identify the requested
context, so these parameters follow and the Req-length is set to 5.
Note that the exact values in the Vendor-ID and Sub-Type follow
[RFC5094].
6.2.2. Local Mobility Anchor Address (LMAA) Option
This option is used to transfer the Local Mobility Anchor IPv6
Address (LMAA) or its IPv4 Address (IPv4-LMAA), with which the mobile
node is currently registered. The detailed definition of the LMAA is
described in [RFC5213].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Length | Option-Code | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Mobility Anchor Address ... |
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Option-Type TBD2
Option-Length 18 or 6
Option-Code
0 Reserved
1 IPv6 address of the local mobility anchor (LMAA)
2 IPv4 address of the local mobility anchor (IPv4-
LMAA)
Reserved This field is unused. It MUST be initialized to zero
by the sender and MUST be ignored by the receiver.
Local Mobility Anchor Address
If Option-Code is 1, the LMA IPv6 address (LMAA) is
inserted. If Option-Code is 2, the LMA IPv4 address
(IPv4-LMA) is inserted.
6.2.3. Mobile Node Link-local Address Interface Identifier (MN LLA-IID)
Option
This option is used to transfer the interface identifier of the
mobile node's IPv6 Link-local Address that is used in the P-AN. In
deployments where the interface identifier is assigned by the
network, or it is known to the network, this option is used to
transfer this identifier from the PMAG to NMAG.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Interface Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type TBD3
Option-Length 10
Reserved This field is unused. It MUST be initialized to zero
by the sender and MUST be ignored by the receiver.
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Interface Identifier
The Interface Identifier value used for the mobile
node's IPv6 Link-local address in the P-AN.
6.2.4. Home Network Prefix Option
This option is used to transfer the home network prefix that is
assigned to the mobile node in the P-AN. The Home Network Prefix
Option defined in [RFC5213] is used for this.
6.2.5. Link-local Address Option
This option is used to transfer the link-local address of the PMAG
(PMAG). The Link-local Address Option defined in [RFC5213] is used
for this.
6.2.6. GRE Key Option
This option is used to transfer the GRE Key for the mobile node's
data flow over the bi-directional tunnel between the PMAG and NMAG.
The message format of this option follows the GRE Key Option defined
in [GREKEY]. The GRE Key value uniquely identifies each flow and the
sender of this option expects to receive packets of the flow from the
peer AR with this value.
6.2.7. IPv4 Address Option
As described in Section 4.3, if the mobile node runs in IPv4-only
mode or dual-stack mode, it requires IPv4 home address (IPv4-MN-HoA).
This option is used to transfer the IPv4 home address if assigned on
the previous link. The format of this option follows the IPv4 Home
Address Request Option defined in [IPv4PMIPv6].
6.2.8. Vendor-Specific Mobility Option
This option is used to transfer any other information defined in this
document. The format and used values of this option follow the
Vendor-Specific Mobility Option defined in [RFC5094].
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7. Security Considerations
Security issues for this document follow those for PMIPv6 [RFC5213]
and FMIPv6 [RFC5568]. In PMIPv6, the MAG and local mobility anchor
are assumed to share security associations. In FMIPv6, the access
routers (i.e., the PMAG and NMAG in this document) are assumed to
share security associations.
The Handover Initiate (HI) and Handover Acknowledge (HAck) messages
exchanged between the PMAG and NMAG MUST be protected using end-to-
end security association(s) offering integrity and data origin
authentication. The PMAG and the NMAG MUST implement IPsec [RFC4301]
for protecting the HI and HAck messages. IPsec Encapsulating
Security Payload (ESP) [RFC4303] in transport mode with mandatory
integrity protection SHOULD be used for protecting the signaling
messages. Confidentiality protection SHOULD be used if sensitive
context related to the mobile node is transferred.
IPsec ESP [RFC4303] in tunnel mode SHOULD be used to protect the
mobile node's packets at the time of forwarding if the link between
the PMAG and NMAG exposes the mobile node's packets to more threats
than if they had followed their normal routed path.
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8. IANA Considerations
This document defines new flags and status codes in the HI and HAck
messages as well as three new mobility options. The Type values for
these mobility options are assigned from the same numbering space as
allocated for the other mobility options defined in [RFC3775]. Those
for the flags and status codes are assigned from the corresponding
numbering space defined in [RFC5568] and requested to be created as
new tables in the IANA registry (marked with asterisks). New values
for these registries can be allocated by Standards Action or IESG
approval [RFC5226].
Mobility Options
Value Description Reference
----- ------------------------------------- -------------
TBD1 Context Request Option Section 6.2.1
TBD2 Local Mobility Anchor Address Option Section 6.2.2
TBD3 Mobile Node Link-local Address
Interface Identifier Option Section 6.2.3
Handover Initiate Flags (*)
Registration Procedures: Standards Action or IESG Approval
Flag Value Description Reference
---- ----- ----------------------------------- -------------
S 0x80 Assigned Address Configuration flag [RFC5568]
U 0x40 Buffer flag [RFC5568]
P 0x20 Proxy flag Section 6.1.1
F 0x10 Forwarding flag Section 6.1.1
Handover Acknowledge Flags (*)
Registration Procedures: Standards Action or IESG Approval
Flag Value Description Reference
---- ----- ------------------------------- -------------
U 0x80 Buffer flag Section 6.1.2
P 0x40 Proxy flag Section 6.1.2
F 0x20 Forwarding flag Section 6.1.2
Handover Initiate Status Codes (*)
Registration Procedures: Standards Action or IESG Approval
Code Description Reference
---- -------------------------------------- -------------
0 FBU with the PCoA as source IP address [RFC5568]
1 FBU whose source IP address is not PCoA [RFC5568]
2 Indicate the completion of forwarding Section 6.1.1
3 All available context transferred Section 6.1.1
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4-255 Unassigned
Handover Acknowledge Status Codes (*)
Registration Procedures: Standards Action or IESG Approval
Code Description Reference
---- --------------------------------------- -------------
0 Handover Accepted or Successful Section 6.1.2
(with NCoA valid) [RFC5568]
1 Handover Accepted, NCoA not valid [RFC5568]
2 Handover Accepted, NCoA assigned [RFC5568]
3 Handover Accepted, use PCoA [RFC5568]
4 Message sent unsolicited [RFC5568]
5 Context Transfer Accepted or Successful Section 6.1.2
6 All available Context Transferred Section 6.1.2
7-127 Unassigned
128 Handover Not Accepted, reason unspecified [RFC5568]
129 Administratively prohibited [RFC5568]
130 Insufficient resources [RFC5568]
131 Requested Context Not Available Section 6.1.2
132 Forwarding Not Available Section 6.1.2
133-255 Unassigned
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9. Acknowledgments
The authors would like to specially thank Vijay Devarapalli and Sri
Gundavelli for their thorough reviews of this document.
The authors would also like to thank Charlie Perkins, Desire Oulai,
Ahmad Muhanna, Giaretta Gerardo, Domagoj Premec, Marco Liebsch, Fan
Zhao, Julien Laganier and Pierrick Seite for their passionate
discussions in the working group mailing list.
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10. References
10.1. Normative References
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5568] Koodli, R., "Mobile IPv6 Fast Handovers", RFC 5568,
July 2009.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005.
[RFC5094] Devarapalli, V., Patel, A., and K. Leung, "Mobile IPv6
Vendor Specific Option", RFC 5094, December 2007.
[IPv4PMIPv6]
Wakikawa, R., Ed. and S. Gundavelli, "IPv4 Support for
Proxy Mobile IPv6",
draft-ietf-netlmm-pmip6-ipv4-support-18.txt,
February 2010.
[GREKEY] Muhanna, A., Ed., "GRE Key Option for Proxy Mobile IPv6",
draft-ietf-netlmm-grekey-option-09.txt, May 2009.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
10.2. Informative References
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4988] Koodli, R. and C. Perkins, "Mobile IPv4 Fast Handovers",
RFC 4988, October 2007.
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Appendix A. Applicable Use Cases
A.1. PMIPv6 Handoff Indication
PMIPv6 [RFC5213] defines the Handoff Indicator Option and describes
the type of the handoff and the values to set to the option. This
document proposes one approach to determining the handoff type by the
NMAG when the handoff of the mobile node is executed.
According to [RFC5213], the following handoff types are defined:
0) Reserved
1) Attachment over a new interface
2) Handoff between two different interfaces of the mobile node
3) Handoff between mobile access gateways for the same interface
4) Handoff state unknown
5) Handoff state not changed (Re-registration)
Assuming that there is a valid MN Link-layer Identifier (MN LL-ID),
the following solution can be considered. When the NMAG receives the
MN LL-ID from the PMAG in the MN LL-ID option via the HI or HAck
message, the NMAG compares it with the new MN LL-ID that is obtained
from the mobile node in the N-AN. If these two MN LL-IDs are the
same, the handoff type falls into 3) and the Handoff Indicator value
is set to 3. If these two MN LL-IDs are different, the handoff is
likely to be 2) since the HI/HAck message exchange implies that this
is a handoff not a multi-homing, therefore the Handoff Indicator
value can be set to 2. If there is no HI/HAck exchange performed
prior to the network attachment of the mobile node in the N-AN, the
NMAG may infer that this is a multi-homing case and set the Handoff
Indicator value to 1. In the case of re-registration, the MAG, to
which the mobile node is attached, can determine if the handoff state
is not changed, so the MAG can set the HI value to 5 without any
additional information. If none of them can be assumed or there is
no valid MN LL-ID available, the NMAG may set the value to 4.
A.2. Local Routing
Section 6.10.3 in [RFC5213] describes that if EnableMAGLocalRouting
flag is set, when two mobile nodes are attached to one MAG, the
traffic between them may be locally routed. If one mobile node moves
from this MAG (PMAG) to another MAG (NMAG) and if the PMAG does not
detect the mobile node's detachment, it will continue to forward
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packets locally forever. This situation is more likely to happen in
the reactive fast handover with WLAN access, which does not have the
capability to detect the detachment of the mobile node in a timely
manner. This specification can be applied to handle this case. When
the mobile node attaches to the NMAG, the NMAG sends the HI message
to the PMAG with the 'F' flag set, which makes the PMAG realize the
detachment of the mobile node and establish the inter-MAG tunnel.
The PMAG immediately stops the local routing and sends the packets
for the mobile node to the NMAG via that tunnel, which are then
delivered to the mobile node on the new link.
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Appendix B. Change Log
Changes at -00
* Added separate sections for MH and ICMP.
* Clarified usage of HNP and IPv4-MN-HoA throughout the document.
* Added IANA Considerations.
* Added section on Other Considerations, including operation of
uplink packets when using link-layer addresses, multiple
interface usage and transmission of RA to withdraw HNP in the
event of failure of PMIP6 registration.
* Revised Security Considerations.
Changes from -00 to -01
* Removed ICMPv6-based message format.
* Clarified HI/HAck exchange in the predictive mode (step (e) in
Figure 2).
* Clarified information retrieval about the PMAG in the reactive
mode.
* Removed the extension to the GRE Key Option.
* Clarified the handoff type considerations in Appendix A.
* Home Network Prefix Option, Link-local Address Option and
Vendor-Specific Mobility Option are added.
Changes from -01 to -02
* Aligned HI/HAck message formats with
draft-ietf-mipshop-rfc5268bis-00.txt.
* Revised Section 8 removing the request for the type assignment
of HI/HAck Mobility Headers.
Changes from -02 to -03
* Updated HI/HAck message formats according to
draft-ietf-mipshop-rfc5268bis-01.txt.
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* Cleaned up Figure 2 and Figure 3.
* Moved PMIP domain boundary crossing situation in Section 4.1 to
Appendix A.3.
* Removed the alternative protocol operation with an unsolicited
HAck from Section 4.1.
* Modified Code values in the HAck message in order to avoid
collision with those in draft-ietf-mipshop-rfc5268bis-01.txt.
* Clarified the usage scenarios of Context Request Option.
* Modified the description of Code values in the HAck message.
* Changed the container for the IPv4-LMAA from IPv4 Address
option to the LMAA option.
* Made Confidentiality protection "SHOULD" for context transfer.
Changes from -03 to -04
* Added more explanations about MIPv6, FMIPv6 and PMIPv6 in
Abstract.
* Moved Figure 1 to Section 4.
* More clearly indicated the FMIPv6 messages that are not
applicable in the PMIPv6 context.
* Mandated the support of IP Sec on the PMAG and NMAG in order to
protect signaling and user packets and the context information.
* Added a new section for the inter-AR tunneling operation
(Section 4.2).
* Added descriptions about the encapsulation type in Sections 4.1
and 4.3.
* Added a description about buffering requirements on the MAG in
Section 4.1.
* Added a description about the timing of L2 and L3 connection
establishments in Section 4.1.
* Added a new section for PMIPv6-related fast handover issues
(Section 5) and a description about preferable behaviors of the
mobile node and MAG to reduce packet loss.
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* Added Acknowledgments section (Section 9).
* Added a new section for local routing in Appendix (A.2).
Changes from -04 to -05
* Fixed Figure 2 (step (i)).
* Defined the Mobile Network Interface Identifier (MN-IID)
mobility option in Section 6.2.4 (swapped with old Section
6.2.5), and added it to IANA considerations (Section 8).
* Changed from SHOULD to MUST regarding the inclusion of the
MN-ID, MN-HNP, MN-IID and the LMAA options in the HI message
(step (c) in Section 4.1).
* The optional behavior of the NMAG that allows it to send uplink
packets directly to the local mobility anchor before the PBU/
PBA exchange was removed from section 4.2 (as out of scope).
* In Section A.3, the description about the HA address assignment
from the NAR to the mobile node was removed (as out of scope).
Changes from -05 to -06
* Added 'P' flag in the HI and Hack messages to distinguish them
from those in FMIPv6.
* Made editorial corrections in Section 2 (Introduction), Section
3 (Terminology), Section 4 (Protocol Overview) and Section 4.2
(Inter-AR Tunneling Operation).
* Added a description on how forwarded packets should be handled
in the access network at step (f) in Section 4.1.
* Added all types of encapsulation methods that should be
supported in Section 4.1.
* Revised the Code values for the HI message in Section 6.1.1.
* Revised the Code values for the HAck message in Section 6.1.2
and added a description of its usage at step (d) of the
reactive handover mode in Section 4.1.
* Removed the definition of the IP Address Option in Section
6.2.3 and moved to Section 6.2.7, which currently refers to the
IPv4 Home Address Option defined by RFC5555. Revised the IANA
Consideration section accordingly.
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* Removed the Option-Code from the Mobile Node Identifier (MN
IID) Option.
* Removed Appendix A.3 (Handling of PMIPv6/MIPv6 switching).
Changes from -06 to -07
* Added explanations about defining and setting the 'P' flag for
the HI and Hack messages in Sections 4 and 4.1.
* Corrected the references for the encapsulation types in Section
4.1.
* Modified the Code values for the HI message in Section 6.1.1 to
avoid overlapping with those in
draft-ietf-mipshop-rfc5268bis-01.txt.
* Modified the reference for the IPv4 Address Option from RFC5555
to [IPv4PMIPv6] in Section 6.2.7.
Changes from -07 to -08
* Corrected the reference for the TLV-header UDP encapsulation in
Section 4.1.
* Updated the version number of the reference document
[IPv4PMIPv6] and the option name defined by that document in
Section 6.2.7.
Changes from -08 to -09
* Added a paragraph at the beginning of Section 4 describing the
assumption related to the lower layer signaling.
* Added a new section on the manageability considerations in
Section 5 describing the configurations on the network and the
mobile node assumed in this document.
* Modified the assumed configuration of the MAG regarding its
link-layer address in Section 5 (Section 5.2 in version -09).
* Specified the requested option to identify the target MN for
the inter-AR tunneling in Section 6.1.1.
* Specified the default context information in the Context
Request Option in Section 6.2.1.
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Changes from -09 to -10
* Revised the document based on the comments from TSV-DIR, SEC-
DIR, OPS-DIR and GEN-ART.
+ Split the abstract section in half for readability.
+ Added the definition of Localized Mobility Anchor (local
mobility anchor) in Section 3.
+ Added the purpose of this document at the beginning of
Section 4 to make the paragraph more complete.
+ Revised the third paragraph of the Security Consideration
section for more precise expression.
+ Moved the description about the requirement to set the 'P'
flag in HI/HAck to Sections 6.1.1 and 6.1.2. Also, noted
the 'P' flag setting below the message formats.
+ Described the both 'P' and 'F' flags as newly defined ones
in Section 4.
+ Clarified the usage of the Context Request Option if a
default set of context information is defined in Section
6.2.1 (changed from "not mandatory" to "not used").
+ Modified the identifier for the interface on the MN to the
MN's link-layer ID (MN LL-ID).
+ Corrected the local routing operation of the PMAG in
Appendix A.2.
* Revised the descriptions about the encapsulation mechanism for
the inter-MAG tunnel in Section 4.2 and other related parts for
clarification.
* Also listed the new flags and status codes for the HI/HAck
messages in the IANA Considerations section.
* Elaborated on the example use of the Context Request Option in
Section 6.2.1.
Changes from -10 to -11
* Changed the term "MN Interface Identifier (MN-IID) option" to
"MN Link-local Address Interface Identifier (MN LLA-IID)
option" in Section 6.2.3. Its usage is valid only when the
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network assigns the interface identifier.
* Revised the description of the neighbor cache entry in Section
4.1 to include the MN LLA-IID.
Changes from -11 to -12
* Changed the term "HO-Initiate" to "Handover indication".
* Added the handover trigger from the PMAG to the mobile node
("Handover command") to clarify the timing of handover in
Figure 2.
* Revised IANA Considerations to include all values that are
defined in RFC5568, but not in the IANA Registry yet.
Changes from -12 to -13
* Editorial corrections.
Changes from -13 to -14
* Corrections related to [RFC2119].
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Authors' Addresses
Hidetoshi Yokota
KDDI Lab
2-1-15 Ohara, Fujimino
Saitama, 356-8502
Japan
Email: yokota@kddilabs.jp
Kuntal Chowdhury
Cisco Systems
30 International Place
Tewksbury, MA 01876
USA
Email: kchowdhury@cisco.com
Rajeev Koodli
Cisco Systems
30 International Place
Tewksbury, MA 01876
USA
Email: rkoodli@cisco.com
Basavaraj Patil
Nokia
6000 Connection Drive
Irving, TX 75039
USA
Email: basavaraj.patil@nokia.com
Frank Xia
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
USA
Email: xiayangsong@huawei.com
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