Network Working Group F. Xia
Internet-Draft B. Sarikaya
Intended status: Informational Huawei USA
Expires: February 10, 2011 August 9, 2010
Prefix Management for Mobile IPv6 Fast Handover on Point-to-Point Links
draft-ietf-mipshop-fmip-ptp-00
Abstract
Mobile IPv6 Fast Handovers specification currently does not
explicitly define prefix management over point-to-point links when a
mobile node uses a prefix to formulate a new care-of-address. In
this document a mechanism is developed for a previous access router
to request unique prefixes from a new access router, and in turn, the
previous access router advertises the prefixes to the mobile node for
a new care-of-address configuration. Extensions to Mobile IPv6 Fast
Handovers specification are also specified in this document.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 10, 2011.
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
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
4. Prefix Management on Point-to-Point Links . . . . . . . . . . 5
4.1. Predictive mode . . . . . . . . . . . . . . . . . . . . . 5
4.2. Reactive Mode . . . . . . . . . . . . . . . . . . . . . . 6
5. HI and Hack Extensions . . . . . . . . . . . . . . . . . . . . 7
5.1. HI Extension . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. HAck Extension . . . . . . . . . . . . . . . . . . . . . . 7
5.3. Dedicated Prefix Option . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
9.2. Informative references . . . . . . . . . . . . . . . . . . 9
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Mobile IPv6 Fast Handovers (FMIPv6) [RFC5568] aims at reducing the
handover latency by reducing the time to configure a new care-of
address (NCoA) for a mobile node(MN). In FMIPv6, the MN formulates a
prospective NCoA when it is still present on a link of a previous
access router (PAR).
[RFC4968] provides different IPv6 link models that are suitable for
IEEE802.16 based networks and provides analysis of various
considerations for each link model and the applicability of each link
model under different deployment scenarios. [RFC5121] specifies the
addressing and operation of IPv6 over the IPv6 specific part of the
packet convergence sublayer of IEEE Std 802.16e [802.16e], and point-
to-point link model is recommended. Also, 3GPP and 3GPP2 have
adopted the point-to-point link model based on the recommendations in
[RFC3314].
In this document, we first explain the problems associated with
FMIPv6 on point-to-point links followed by a detailed description of
prefix management for FMIPv6 operation on point-to-point links.
In Section 3 we describe why the point-to-point link address
formation procedures are needed in FMIPv6, in Section 4 we define a
procedure that a new access router (NAR) can use to dynamically
assign unique prefixes in point-to-point links and in Section 5 we
define necessary messages/options for the operation in Section 4.
2. 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].
The terminology in this document is based on the definitions in
[RFC5568], in addition to the ones specified in this section.
point-to-point link model: In this model, a set of layer 2 transport
connections between a MN and an access router (AR) are treated as
a single link. Each link is allocated a separate, unique prefix
or a set of unique prefixes by the AR. Please refer to [RFC4968]
for details.
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shared link model: In this model, one or more prefixes are shared by
mobile nodes for constructing their global IPv6 addresses. Please
refer to [RFC4968] for details.
dedicated prefix: In point-to-point link model, a unique prefix used
by a MN for formulating a NCoA while the MN is still on a PAR's
link.
3. Problem Statement
The following are operations relating to prefix management as per
[RFC5568]:
o Movement detection. The protocol enables a MN to quickly detect
that it has moved to a new subnet by providing the new access
point and the associated subnet prefix information when the MN is
still connected to its current subnet. For instance, the MN may
discover available access points using link-layer specific
mechanisms (i.e., a "scan" in WLAN) and then request subnet
information corresponding to one or more of those discovered
access points. The MN sends a Router Solicitation for Proxy
Advertisement (RtSolPr) to its access router to resolve one or
more Access Point Identifiers (AP-ID)to subnet-specific
information. In response, the access router sends a Proxy Router
Advertisement (PrRtAdv) message containing one or more [AP-ID, AR-
Info] tuples, which the MN can use in readily detecting movement:
when attachment to an access point with AP-ID takes place, the MN
knows the corresponding new router's coordinates including its
prefix, IP address, and L2 address.
o NCoA configuration. AR-Info contains the access router's L2 and
IP addresses, and the prefix valid on the interface to which the
Access Point (identified by AP-ID) is attached. With the prefix
provided in the PrRtAdv message, the MN formulates a prospective
NCoA.
In shared link model, the prefix and NCoA are manually configured in
the previous access router. This is not a problem because there is
only a small number of adjacent access routers, and the prefix is
shared by many mobile nodes. However, it becomes a big problem when
trying to configure prefixes manually in point-to-point link model.
In this model, each MN has one or more dedicated prefixes, that is,
different MNs have different prefixes. The prefixes could be
allocated dynamically. When a MN attaches to an AR, the AR should
allocate one or more dedicated prefixes for it; when the MN detaches
from the AR, the MN's prefixes are released, and can be reused by
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other MNs. The number of unique prefixes in this operation can be
huge.
NCoA formulation in point-to-point links requires a PAR to
dynamically request a dedicated prefix from a NAR, and then advertise
it to the MN using a Proxy Router Advertisement (PrRtAdv) message.
[RFC5568] does not specify such dependencies.
4. Prefix Management on Point-to-Point Links
Upon the indication of handover from the PAR to the NAR, the PAR uses
Handover Initiate (HI)/ Handover Acknowledge (HAck) message exchange
to get a dedicated prefix from the NAR. The PAR then sends this
prefix in the PrRtAdv message to the MN as described in [RFC5568].
In the PrRtAdv message, A-bit and L-bit MUST be turned on. The MN
thus uses this prefix for movement detection and NCoA configuration
as per [RFC5568].
4.1. Predictive mode
New FMIPv6 message exchange is introduced for the PAR to ask for MN's
dedicated prefix as shown in Figure 1. In [RFC5568], HI is assumed
to be sent after the Fast Binding Update (FBU) for handover
indication. Here, modified HI/Hack messages are used for prefix
request/response. Details are described in Section 5.
The NAR MAY use DHCPv6 prefix delegation to request/ release prefixes
from a DHCPv6 server. The DHCPv6 messages are triggered by the HI
for prefix request. The NAR MAY also use AAA prefix delegation to
request/ release prefixes for this MN from an AAA server. The
mechanisms for the NAR to acquire the prefixes are outside the scope
of this document.
Lifetime in Dedicated Prefix Option Figure 1 is used to prevent
prefix depletion because of erroneous movement in which the mobile
node receives a dedicated prefix prior to a handover that it is
moving to a new access point but it either moves to a different one
or it aborts movement altogether. Not until timeout of the prefix
does the NAR release it.
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MN PAR NAR DHCP/AAA
| | | Server
| | | |
|------RtSolPr------->| | |
| | HI(Prefix Request) | |
| |----------------------->|Prefix |
| | |-Request->|
| | |<-Reply---|
| | HAck(Prefix Response) | |
| |<-----------------------| |
|<-----PrRtAdv--------| | |
| | |No FBU |
| | |Release |
| | |Prefix |
|------FBU----------->|--------HI------------->| |
| |<------HAck-------------| |
| <--FBack---|--FBack---> | |
disconnect forward | |
| packets===================>| |
| | | |
| | | |
connect | | |
| | | |
|--------- UNA ------------------------------->| |
|<=================================== deliver packets |
| | |
Figure 1: Prefix Signaling
In some wireless networks, the handover control may reside in the
network even though the decision to undergo handover may be mutually
agreed between the MN and the network. In such a case, the PAR can
send an unsolicited PrRtAdv containing the link-layer address, IP
address, and dedicated prefix of the mobile node when the network
decides that a handover is imminent. In this network-initiated
handover scenario, there isn't explicit RtSolPr to trigger PAR to
request a prefix and implementation specific trigger MUST be used by
PAR to send HI message for prefix request.
4.2. Reactive Mode
In the reactive mode, there are two cases. A MN receives PrRtAdv
message or otherwise.
o The MN receives PrRtAdv message and formulates NCoA before
attaching to the NAR. The MN and the NAR operate in line with the
procedure defined in [RFC5568].
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o The MN can't formulate NCoA before attaching to the NAR. IP
connectivity should be established first. The MN can configure
its IP address using stateless address configuration, or using
stateful address configuration. In the former case, the NAR
SHOULD send un-solicited RA to expedite MN's address
configuration. Once NCoA formulation is finished, the MN operates
according to [RFC5568].
In both cases, the MN formulates NCoA from the dedicated prefix.
Since the MN has already handed over to the NAR, this prefix is
retained.
5. HI and Hack Extensions
5.1. HI Extension
The Handover Initiate (HI),defined in [RFC5568], is a Mobility Header
message sent by one Access Router to another to initiate the process
of a MN's handover.
In [RFC5568], the PAR uses a Code value of 0 when it processes an FBU
with PCoA as source IP address, while uses a Code value of 1 when it
processes an FBU whose source IP address is not PCoA. A new Code
value of TBD1 (to be assigned by IANA) is used for the dedicated
prefix request. Dedicated Prefix Option defined in Section 5.3 MAY
be included as a hint for a requested preference. The NAR MAY
allocate a dedicated prefix based on the prefix preference in the
option. If the option is not included, the NAR allocates a prefix
according to it's discretion.
5.2. HAck Extension
Handover Acknowledgment message defined in [RFC5568] is a Mobility
Header message that MUST be sent as a reply to the Handover Initiate
message. In this document, HAck is extended as follows to respond to
a dedicated prefix request:
o One new Code value is defined. Here, a Code value of TBD2 (to be
assigned by IANA) is used for dedicated prefix response.
o Dedicated Prefix Option defined in Section 5.3 MUST be included
for prefix delegation.
5.3. Dedicated Prefix Option
This option is of the form shown in Figure 2.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Option-Code | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Dedicated Prefix Option
Type To be assigned by IANA
Length The length of the option in units of 8 octets.
Prefix Length
8-bit unsigned integer. The number of leading bits
in the Prefix that are valid. The value ranges from 0
to 128.
Option-Code
1 Dedicated Prefix
Lifetime 32-bit unsigned integer. The length of time in seconds
(relative to the time the packet is sent). A value of
all one bits (0xffffffff) represents infinity.
Prefix An IP address or a prefix of an IP address. A MN uses it
to formulate a NCoA.
6. Security Considerations
Prefix management for FMIPv6 operation on point-to-point links uses
two messages (HI/Hack) for prefix request and response. These
messages are secured using FMIPv6 security mechanisms and hence do
not introduce any new security threats and the security provided by
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FMIPv6 applies completely.
7. IANA considerations
This document extends existing HI/HAck messages, new HI Code (TBD1)
and HAck Code (TBD2) values need to be assigned by IANA.
The document also defines one new Mobility Option which needs type
assignment from the Mobility Options Type registry at
http://www.iana.org/assignments/mobility-parameters:
1. Dedicated Prefix Option described in Section 5.3.
8. Acknowledgements
The authors would like to thank Heejin Jang, Daniel Park, Vijay
Devarapalli, Rajeev Koodli, Subir Das, and Spencer Dawkins for
valuable comments.
9. References
9.1. Normative References
[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.
[RFC5121] Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S.
Madanapalli, "Transmission of IPv6 via the IPv6
Convergence Sublayer over IEEE 802.16 Networks", RFC 5121,
February 2008.
9.2. Informative references
[802.16e] Institute of Electrical and Electronics Engineer,
"Amendment for Physical and Medium Access Control Layers
for Combined Fixed and Mobile Operation in Licensed
Bands", IEEE 802.16e/D12.
[RFC3314] Wasserman, M., "Recommendations for IPv6 in Third
Generation Partnership Project (3GPP) Standards",
RFC 3314, September 2002.
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[RFC4968] Madanapalli, S., "Analysis of IPv6 Link Models for 802.16
Based Networks", RFC 4968, August 2007.
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Appendix A. Change Log
o v03 Dedicated Prefix Option made compatible with [RFC5568].
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Authors' Addresses
Frank Xia
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
Behcet Sarikaya
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: sarikaya@ieee.org
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