DHCP-based Fast Handover protocol

1
DHCP-based Fast Handover protocol
draft-ogawa-fhopt-00.txt

• NTT Network systems laboratories
• 2005. 3. 8
• Takeshi Ogawa

62nd IETF - Minneapolis Mobopts RG
2
Outline

• Motivation
• Problem statement
• Proposed protocol
• HO sequence example
• Test system current situation

3
Motivation

• IP layer Fast Handover function is needed for
  real time application.
• A protocol, that realize FH function inexpensive
  and that will be available soon, is required.
• FMIP(MIPSHOP) and Fast RA(DNA) can reduce IP
  layer HO time.
• However, there are 4 problems in both method.

4
Problems of FMIP and Fast RA (1/3)

• Many facilities to be up graded (expensive)
• With FMIP or Fast RA, all of ARs in service
  area MUST be up graded, and the ARs need to
  exchange messages for HOs.
• So, the number of facilities to be upgraded may
  be numerous, and connectivity between every pair
  of different venders and kinds of ARs shall be
  assured.
• The fewer facilities to be upgraded the better,
  and less correlation between facilities is better.

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Problems of FMIP and Fast RA (2/3)

• 2. Handling of stateful address (not defined yet)
• Plain IP nodes (usually) uses DHCP to get
  stateful IP addresses.
• With FMIP, a new stateful IP address to be
  used after handover is distributed by
  PrRtAdv message (introduced in FMIP).
• We suppose unified method is better.
• With Fast RA, there is no function to
  distribute stateful IP addresses quickly.
• ... as long as I know.

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Problems of FMIP and Fast RA (3/3)

• Security association (SA) set-up method between
  MN and NAR. (being discussed in Mobopts now)
• With FMIP, FBU messages MUST be authenticated
  by AR to prevent service from being stolen.
• However, the SA setup method for it is not
  defined, it might take long time...
• 4. How to reduce L2 HO time. (not defined yet)
• In the FMIP and the Fast RA, there is no
  function to reduce the L2 HO processing time.

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Proposed DHCP-based FH protocol

• With the protocol, DHCP server sends "Fast
  Handover Options" to MN before handovers.
• Those options include essence of FMIP, link layer
  and IP layer information, to be used by the MN
  after handovers, so that the MN can complete HO
  sequence quickly.

CN
CN
Fast HO function
HA
HA
IPv6 network
Fast HO function
IPv6 network
DHCP server
AR
AR
AR
AR
AR
AR
AR
AR
MN
MN
Current FMIP and Fast RA
Proposed method
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It solves the 4 problems (1/2)
It is based on DHCP so,

• Facilities to be up graded
• Fewer than FMIP and Fast RA (inexpensive)
• With this protocol plain access routers (if
  they have the DHCP relay function) can be used.
• 2. Handling of stateful address
• Unified in DHCP manner. (defined)
• SA set-up method
• Not problem with this protocol.
• SA between MN and DHCP server can be used
  after handover. (no problem)
• (usually the DHCP server is not changed)

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It solves the 4 problems (2/2)
Furthermore,
4. L2 HO time Reduced by sending L2
information to MN before HO. (defined
(wireless LAN)) For example, wireless LAN
channel number used by new APs are sent to a
MN, and the MN can search for the notified
channel only instead of all channels and
can reduce layer 2 HO time.
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Seamless HO for MIP sequence example with this
protocol
MN (DHCP client)
DHCP server
PAR
CN
HA
Fast Handover options
DHCP REQUEST/REPLAY
BU/BA
Users IP packets
Tunnel Bufferring (Moor)
HO trigger
Search available channel only
BU/BA (request buffering)
Layer2 switch
It could be less than a hundred
millisecond(?) (wireless LAN to wireless LAN HO)
802.11i
NAR
Access authentication
BU/BA (request sending)
Opt DAD (Moor)
Users IP packets
NS(DAD)
Standard messages
DHCP CONFIRM/REPLY
No need if the MN is still in same DHCP-domain
Proposed messages
Defined in other draft
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Test system implementing status
We are currently implementing the test system in
Linux. The basic protocol functions are to be
checked by the end of March.
MobileIPv6 HomeAgent (HA)
DHCPv6 server
CN
DHCPv6 (Server/Client) Sourceforge (Version 0.10)
MobileIPv6 (MN/HA) MIPL (Version 2.0)
OS Linux FedoraCore 3, kernel 2.6.8.1
Wireless LAN Atheros, madwifi (CVS)
L2SW
CISCO 3745
L2SW
L2SW
AP1
AP2
AP3
MN
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Summary

• A DHCP-based FH protocol is proposed.
• Main functions of it are ported from FMIP.
• It could offer FH function inexpensive and would
  be available soon if you give me a help.
• Any comments welcome!
• Thank you in advance!

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Annex
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Functions of proposed method

• It has 5 main Functions.
• (A), (B) and (C) are almost the same as FMIP,
  but (D) and (E) are new functions that FMIP does
  not offer.

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Functions of proposed protocol

• RA proxying function and (B) DHCP proxying
  function.
• Fast Handover Options carry information to MNs
  on old links, which are to be carried by the
  standard RA and DHCP IA options on new links, and
  MNs do not need to exchange RS/RA and DHCP
  solicit messages on new links.

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Functions of proposed protocol

• (C) Movement detection function
• A unique ID for link (L3-information-ID) is
  introduced. Fast Handover Options carry new AP's
  ID (e.g., BSSID) and its corresponding
  L3-information-ID to MNs on old links, and MNs
  can detect movement using those IDs without NUD
  on a new link.

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Functions of proposed protocol

• (D) Layer 2 information distribution function
• Fast Handover Options also carry new link
  information, for example, wireless LAN channel
  number used by new APs, and MNs can search for
  the notified channel only instead of all channels
  and can reduce layer 2 handover.

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Functions of proposed protocol

• (E) Confirm Message solicit function
• A unique ID for DHCP-domains is also
  introduced.
• Fast Handover Options carry the IDs, and a MN
  can know whether it has entered a new DHCP-domain
  after handover. If the MN is still in the same
  DHCP-domain, it does not need to send a confirm
  Message to a DHCP server on a new link.

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Functions not supported

• Smooth HO function
• Tunnel Buffering may be applied
• Prevent interruption during DAD
• Opt DAD may be applied.
• Quick user authentication
• To be discussed but out of scope of this
  protocol now.
• Context Transfer of AR
• This protocol can not offer this function.