Internet DRAFT - draft-mun-mipshop-efh-fast-mipv6
draft-mun-mipshop-efh-fast-mipv6
Mipshop Working Group Youngsong Mun
Internet-Draft Seonggeun Ryu
Expires: January 9, 2013 Kyujin Lee
Soongsil University
July 10, 2012
Enhanced Fast Handover for Mobile IPv6
based on IEEE 802.11 Network
draft-mun-mipshop-efh-fast-mipv6-06.txt
Abstract
In MIPv6 [1], whenever a mobile node changes its attached point,
handover process should be followed to inform its home agent and
correspondent of a MN's current location. The handover process is
decomposed into layer 2 and layer 3 handovers again, and these two
handovers are accomplished sequentially, which causes long latency
problem. This problem is a critical issue in MIPv6. To make up for
this, we propose an enhanced Fast Handover scheme to reduce the
overall latency on handover, revising the Fast Handover [2].
Especially, several messages in layer 3 are sent in one frame during
layer 2 handover.
Status of this Memo
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This Internet-Draft will expire on January 22, 2012.
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Table of Contents
1. Introduction.....................................................3
2. Terminology......................................................3
3. Background Information...........................................5
3.1. IEEE 802.11 Network
3.2. Fast Handover for Mobile IPv6
3.3. A scheme using Fast Handover based on IEEE 802.11
4. Proposed Protocol Details........................................7
5. Message Formats..................................................9
6. Security Considerations..........................................9
7. Conclusions......................................................9
8. References.......................................................9
9. Authors' Addresses..............................................10
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1. Introduction
As the advancement of wireless communication, requirements on the
wireless Internet and mobility support are increasing. To support
mobility, Mobile IPv6 (MIPv6) [1] has been proposed by the Internet
Engineering Task Force (IETF). In MIPv6, when a mobile node (MN)
moves to other subnetwork, it needs certain process, a handover,
which causes long latency problem. There have been many researches to
reduce the handover latency in MIPv6, such as a Fast Handover [2] and
a hierarchical MIPv6 [3]. Still, aforementioned mechanisms are not
appropriate to satisfy real-time traffic. We propose a enhanced fast
handover scheme (EFH) to reduce the handover latency, modified from
the Fast Handover scheme based on IEEE 802.11 [4].
In the Fast Handover, handover latency is smaller than the one of
MIPv6, and packets from a CN to the MN are not lost during the
handover because a tunnel is formed between a previous access router
(PAR) and a new access router (NAR) before the layer 2 handover, and
the NAR will buffer packets destined to the MN through the tunnel.
The Fast Handover scheme, however, needs more signal packets and
buffering. In the EFH, handover latency and signal packets are
reduced than the Fast Handover due to multiple signal packets in one
frame.
2. Terminology
This document borrows all of the terminology from Mobile IPv6 [1] and
Mobile IPv6 Fast Handovers [2], with the following additional terms
from the 802.11 specification [4].
Mobile Node (MN)
A Mobile IPv6 host.
Correspondent Node (CN)
A IPv6 host communicating with MN.
Access Point (AP)
A Layer 2 device connected to an IP subnet that offers
wireless connectivity to a MN. An Access Point Identifier
(AP-ID) refers the AP's L2 address. Sometimes, AP-ID is
also referred to as a Base Station Subsystem ID (BSSID).
Access Router (AR)
The MN's default router.
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Previous Access Router (PAR)
The MN's default router prior to its handover.
New Access Router (NAR)
The MN's anticipated default router subsequent to its
handover.
Previous CoA (PCoA)
The MN's Care of Address valid on PAR's subnet.
New CoA (NCoA)
The MN's Care of Address valid on NAR's subnet.
Handover
A process of terminating existing connectivity and
obtaining new IP connectivity.
Layer 2 handover
Movement of a MN's point of Layer 2 connection from one
wireless access point to another.
Layer 3 handover
Movement of a MN between FAs which involves changing the
care-of address (CoA) at Layer 3.
Router Solicitation for Proxy Advertisement (RtSolPr)
A message from the MN to the PAR requesting information
for a potential handover.
Proxy Router Advertisement (PrRtAdv)
A message from the PAR to the MN that provides
information about neighboring links facilitating
expedited movement detection. The message also acts as a
trigger for network-initiated handover.
Fast Binding Update (FBU)
A message from the MN instructing its PAR to redirect its
traffic (towards NAR).
Fast Binding Acknowledgment (FBack)
A message from the PAR in response to FBU.
Fast Neighbor Advertisement (FNA)
A message from the MN to the NAR to announce attachment,
and to confirm use of NCoA when the MN has not received
FBACK.
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Handover Initiate (HI)
A message from the PAR to the NAR regarding a MN's
handover.
Handover Acknowledge (HAck)
A message from the NAR to the PAR as a response to HI.
3. Background Information
3.1. IEEE 802.11
IEEE 802.11 wireless LAN is the layer 2 protocol and supports
mobility in a link layer level. IEEE 802.11 handover takes place when
a MN changes its association from one access point (AP) to another
and its process consists of a search phase and an execution phase.
This handover process simply consists of the following steps [5]:
a. The MN realizes that a handoff is necessary due to degrading radio
transmission environment for the current AP.
b. Search Phase
The MN performs a scan to see what APs are available. The result
of the scan is a list of APs together with physical layer
information, such as signal strength. The MN chooses one of the
APs and performs a join to synchronize its physical and MAC layer
timing parameters with the selected AP.
c. Execution Phase
1. Authentiation phase
The MN requests authentication with the new AP. For an "Open
System", such authentication is a single round-trip message
exchange with null authentication.
2. Association phase
The MN requests association or reassociation with the new AP.
A reassociation request contains the MAC layer address of the old
AP, while a plain association request does not.
At the association(reassociation) phase, the MN's link layer is
really connected to the NAP. In some 802.11 implementations, the scan
performs far in advance of the handover and perhaps in advance of any
realtime traffic. [5]
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3.2. Fast Handover
In MIPv6, when a MN moves from one subnet to another subnet, a
certain process is needed such as a handover. The handover consists
of layer 2 and layer 3 handovers which are physical and logical
handovers, respectively. In the Fast Handover, two handovers are
interleaved to reduce a handover latency.
The Fast Handover is a scheme which improves MIPv6 handover. In the
Fast Handover, there are two modes, such as predictive and reactive
mode. In this draft, we only explain and use the predictive mode. In
the Fast Handover, several portions of the layer 3 handover are
performed prior to the layer 2 handover. In other words, the MN
performs the layer 3 handover while it connected to a PAR, and in
this case, the PAR must have information about destined AR. The PAR
establishes a tunnel between itself and a NAR and verifies MN's NCoA
through exchanging a handover initiate (HI) message and a handover
acknowledge (HAck) message. Packets that arrive at previous care-of
address (PCoA) are sent to the NAR through an established tunnel
during the handover. The tunnel is kept until MN's NCoA is registered
to a HA.
MN PAR NAR HA CN
| | | | |
|---RoSolPr--->| | | |
|<--PrRrAdv----| | | |
| | | | |
|------FBU---->| | | |
| |------HI----->| | |
| |<----HAck---- | | |
|<---FBack---- |-----FBack--->| | |
--- --- | |
Layer 2 Handover | |
--- --- | |
|-------------FNA------------>| | |
|----Binding Update to HA--------------->| |
| | | |
|<-------------Return Routability--------------->|
| | | |
|----Binding Update to CN----------------------->|
| | | |
Figure 1: MIPv6 fast handover Scheme (FMIPv6) - Predictive mode
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Figure 1 shows the Fast Handover scheme. The MN initiates the Fast
Handover scheme when a layer 2 trigger take places. The MN sends an
RtSolPr message to the PAR and receives a PrRtAdv messages for
information of the NAR. The MN creates the NCoA and sends a FBU
message with the NCoA. The PAR receives the FBU message, then sends a
HI message and receives a HAck message to verify the NCoA in the NAR
and to establish a tunnel between the PAR and the NAR. The PAR sends
FBack messages to the MN and the NAR, respectively after verification
of the NCoA. The MN performs the layer 2 handover when it receives
the FBack message. The MN sends a FNA message to NAR to inform its
movement after the layer 2 handover. Then the MN exchanges a BU and a
BA with the HA to register the NCoA. A Return Routability procedure
is performed between the MN and the CN to establish security
association, and then the MN sends Binding Update message to the CN.
After registration, the handover is finished.
3.3. A scheme using Fast Handover based on IEEE 802.11
The Fast Handover based on IEEE 802.11 wireless LAN has been studied.
[5] shows a order that layer 2 and layer 3 handover processes are
performed when the layer 2 protocol is the IEEE 802.11 wireless LAN
and the layer 3 protocol is the MIPv6 Fast Handover.
4. Enhanced Fast Handover (EFH) Details
When a MN moves into another network, a handover process should be
followed not to lose connectivity. The handover process consists of a
layer 2 and a layer 3 handovers. The layer 2 handover processes a
scan phase, authentication phase and association phase. The layer 3
handover is decomposed into creating, verifying and registering a
new address. The layer 2 and layer 3 handovers are performed
sequentially in MIPv6 while several messages related to layer 3
handover are exchanged prior the layer 2 handover and the rest of the
layer 3 handover in the Fast Handover. To perform the Fast Handover,
several signal messages are needed. These additional messages make
network traffic and use node's resources. In the EFH, the MN sends
one frame containing several signal messages related to layer 3
handover during the layer 2 handover. Therefore, the EFH can register
a new address to HA and CN more quickly than the Fast Handover.
Figure 1 shows messages of the EFH.
We assume that the MN must be able to encapsulate a BU destined to
HA,a HoTI and a CoTI messages to an 802.11 reassociation request
frame. A NAP is assumed to decapsulate the 802.11 reassociation
request frame and to forward the BU message to HA, the HoTI and the
CoTI messages to CN. The EFH only can be performed when the fast
handover is the predictive mode. Otherwise, the MN performs a MIPv6
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handover (or the reactive mode of the Fast Handover). IPsec mechanism
is employed between the MN and the HA, using current security
association (SA) when the MN sends the BU message to HA and the HoTI
message to CN.
MN PAP PAR NAP NAR HA CN
| | | | | | |
|---RoSolPr---->| | | | |
|<--PrRrAdv-----| | | | |
| | | | | | |
|------FBU----->| | | | |
| | |-------HI----->| | |
| | |<-----HAck---- | | |
|<---FBack----- |------FBack--->| | |
----| | | | | | |
^ |----Auth. Request----->| | | |
L2 |<---Auth. Response-----| | | |
Hand |--Reassociatoin Req.-->| | | |
over |<--Reassociation Res.--|--MIPv6 BU to HA->| |
----| | | |------HoTI------->|------>|
| | | |------CoTI--------------->|
|----------FNA----------------->| | |
| | | | | | |
|<---Binding Acknowledgement from HA-------| |
|<---HoTI from CN--------------------------|<------|
|<---CoTI from CN----------------------------------|
| | | | | | |
|----Binding Update to CN------------------------->|
| | | | | | |
Figure 2: The enhanced fast handover scheme (EFH)
The EFH detail is as follows:
Once authentication phase in the layer 2 handover is completed
successfully, reas-sociation phase starts. A MN sends an 802.11
reassociation request frame, which contains three messages that are
performed after the layer 2 handover; a BU, a home test init (HoTI)
and a care-of test init (CoTI) messages. Source address of layer 3
handover messages is a NCoA. Once a NAP receives the reassociation
request frame, it decapsulates that frame and forwards three
messages. Finally the BU message gets to the HA via the NAR and HoTI
and CoTI messages get to CN via the NAR. The rest of handover process
is very similar to the Fast Handover.
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5. Message Formats
To be defined.
6. Security Considerations
In this draft, the security between a MN and a AR does not specify
any particular mechanism to convey information between the MN and AR
the set of information identified in the following internet draft,
can be conveyed between the MN and the AR in a different suitable
manner outside the scope of this document (e.g. ICMP, the protocol
defined by the PANA WG, etc.).
7. Conclusions
In the MIPv6, handover latency is a critical issue. To solve this
problem, R. Koodli has proposed the Fast Handover which reduces
handover latency in the MIPv6. Still, this scheme is not appropriate
to satisfy real-time traffic, since . We propose an enhanced fast handover
scheme (EFH) to reduce the overall latency on the handover, revising
the Fast Handover. Especially, several messages related to the layer
3 handover are sent in one frame during layer 2 handover.
Currently, the Fast Handover scheme is being standardized in IETF,
and then will soon be a RFC document. The EFH scheme improves the
Fast Handover, using layer 2 handover frame. Therefore, if EFH scheme
is used with the Fast Handover sheme, a handover performance will be
improved.
8. References
[1] C. Perkins, D. Johnson, and J. Arkko, "Mobility Support in
IPv6", Request for Comments (Proposed Standard) 6275, Internet
Engineering Task Force, July 2011.
[2] R. Koodli, (editor), "Mobile IPv6 Fast Handovers", Request for
Comments (Proposed Standard) 5268, Internet Engineering Task
Force, July 2009.
[3] H. Soliman, C. Catelluccia, K. ElMalki, and L. Bellier,
"Hierarchical Mobile IPv6 mobility management (HMIPv6)",
Request for Comments (Proposed Standard) 5380, Internet
Engineering Task Force, October 2008.
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[4] "Wireless LAN Medium Access Control (MAC) and Physical Layer
(PHY) Specifications", ANSI/IEEE Std 802.11, 1999 Edition.
[5] P. McCann, "Mobile IPv6 Fast Handovers for 802.11 Networks",
Request for Comments (Informational) 4260, Internet Engineering
Task Force, November 2005.
[6] Y. Mun, J. Park, "Layer 2 Handoff for Mobile-IPv4 with 802.11",
draft-mun-mobileip-layer2-handoff-mipv4-01.txt, September 2003.
Work In Progress.
[7] M. Ergen, "IEEE 802.11 Tutorial", June 2002.
9. Authors' Addresses
Youngsong Mun
Soongsil University
Seoul Korea
Email: mun@ssu.ac.kr
Seonggeun Ryu
Soongsil University
Seoul Korea
Email: sgryu@sunny.ssu.ac.kr
Kyujin Lee
Soongsil University
Seoul Korea
Email: demian21c@nate.com
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