Transcript Terminal Independent Mobility for IP (TIMIP) António Grilo, Pedro

Terminal Independent Mobility for IP (TIMIP)
António Grilo, Pedro Estrela, Mário Nunes, INESCIST, PORTUGAL
IEEE Communication Magazine - December 2001
報告者：林靖祐
學 號：m9356022
2005/05/03
Outline


Introduction
Overview IP Mobility in IETF
• Mobile IP
• HAWAII
• Cellular IP

Terminal Independent Mobility for IP (TIMIP)
•
•
•
•

Power up
Micromobility
Macromobility
Context transfer
Conclusion
Introduction
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
New Architecture for IP mobility in
wireless access networks
Based on principles similar to those in the
CIP and HAWAII architectures
Suited for micro-mobility scenarios
Still using MIP for macromobility
TIMIP uses context-transfer mechanisms
to support seamless hand-off
Introduction

Layer-2 Mobility
• Easy to accomplish & already supported (eg. Wireless LAN)
• Does not allow terminal
to roam between different LANs and
to cross between router domains

Layer-3 Mobility
• Internet-wide mobility at the cost of more complex
management
• Macromobility scenarios
 MIP
• micromobility scenarios
 HAWAII
 CIP
• These three proposals require change of legacy IP protocol
stacks to support mobility aware capability
Overview IP Mobility in IETF
• Mobile IP
• HAWAII
• Cellular IP
Overview IP Mobility in IETF
Mobile IP

Mobile IP
• Could be used in both micromobility and
macromobility scenarios.
• Terminal has two address
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home address (HAddr)
care-of address (CoAddr)
• HA & FA
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Home agent (HA)
Foreign agent (FA)
• Tunnel
Overview IP Mobility in IETF
Mobile IP
Tunneling
MT
Tunneled Packet
Src=Orig, dst= CoAddr
Home
Tunneling
Network
Tunneling
Foreign
Tunneling
Core Network
Network
Original
FAPacket
Src=Orig, dst= HAddr
HA
(CoAddr)
Original Packet
Src=Orig, dst= HAddr
Orig
Overview IP Mobility in IETF
Mobile IP

Mobile IP problems
• Triangulation and IP tunneling are
difficult to integrate with RSVP.
• Triangulation may cause a significant
increase in end-to-end transmission
delay.
Overview IP Mobility in IETF
HAWAII
• HAWAII
• (Handoff-Aware Wireless Access Internet Infrastructure)
• HAWAII was proposed in order to solve the QoS
and efficiency issues of MIP
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Special forwarding entries are installed on specific
routers aware of the location of specific terminal
Each domain is structured according to a hierarchy of
nodes, forming a logical tree
Each domain owns a root gateway
• (Domain Root Router) => HA
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Retain same address when moving within domain.
MIP procedure is used when the terminal moves to a
foreign domain.
HAWAII
Tunneling
Core Network
Foregin
domain
root
router
Home
domain
root
router
Router at
hierachical
level 1
Access
point
Intra domain
hand over
MT
Inter domain
hand over(MIP)
MT
MT
Overview IP Mobility in IETF
Cellular IP
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Each domain is composed of a number of CIP nodes
structured in a tree.
The CIP nodes maintain routing cache and paging cache.
MIP procedure is used
when the terminal moves
to a foreign domain.
Overview IP Mobility in IETF
Cellular IP
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Paging caches
Routing caches
X: from
from F,G
G
X:
F
E
Gateway
router
Global Internet with Mobile IP
X: from C
G
R
D
A
MT
B
FA
G times out
C
F
Paging-update
TIMIP
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Terminal Independent Mobility for IP (TIMIP)
• Can be totally implemented in the network
nodes and work transparently to the IP layer of
the terminals.
• TIMIP domain is an IP subnet organized as a
logical tree of access routers whose root is the
access network gateway (ANG)
TIMIP- Different Elements
• Access network gateway (ANG)
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The root AR, interfacing with the core IP network
Perform mobility management functions to support MIPbased macromobility
• Access router (AR)
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Each AR incorporates mobility management functions
• Access point (AP)
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Is an AR that directly communicates to MT
• Mobile terminal (MT)
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Runs the user applications
Roaming between different APs performed by layer-2
TIMIP- Architecture
...
...
MT
MT
MT
MT
Tunneling
Core network
Access
network
gateway
(level n).
Access
router
(level 2)
Access
point
(level 1)
Access
router
(level n-x)
Access
point
(level 1)
...
Access
router
(level 2)
TIMIP
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All IETF proposals for IP mobility require the mobile
terminals to use a mobility-aware protocol stack
• Mobile terminals notify handoff by means of special IP
layer signaling
• Replace the protocol stack of all legacy terminals can
be a hard task (considering OS & version)

TIMIP
• Coupling the IP layer with layer-2 handoff mechanisms
at the APs, avoids the need for special IP layer
signaling between the terminal and the AP.
TIMIP- Registration Info on ANG for MT
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In order for a terminal to be recognized by the
TIMIP network, it has to be registered.
Information ANG keep on each MT
• MAC address
• IP address
• MIP capability
• IP address of the MIP home agent
• Authentication key
• Authentication option
Once these data is configured at the ANG, it is
forwarded to the APs so that they are able to know
the IP address of newly associated terminals based
on MAC add
TIMIP- Power UP

MT first appears in a TIMIP domain, routing
path is created along the hierarchy of ARs
1. MT perform a layer2 association with an AP.
2. Layer2 notifies the IP layer, triggering the routing
reconfiguration procedure.
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Layer2 sends the MAC address of the MT to the IP layer.
The MAC is matched against the information broadcast by the ANG to
find the respective IP address.
If AP has no routing table entry for the MT Update routing Table.
3~5. Creat Routing Path
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RoutingUpdate/RoutingUpdateAck messages reaches the ANG,
completes the routing path
TIMIP- Power UP
2
...
1
3
MT
RoutingUpdate
Access
point
(level 1)
updates
routing table
...
RoutingUpdateACK
RoutingUpdateACK
RoutingUpdate
Access
router
(level 2)
4
updates 5
routing table
RoutingUpdateACK
RoutingUpdate
Access
router
(level n-x)
Access
point
(level 1)
...
Access
router
(level 2)
Access
network
gateway
(level n).
Tunneling
Core network
TIMIP- Power UP
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Routing Update/ACK message includes timestamp
• All APs are synchronized by means of the Network
Time Protocol (NTP)
Routing path is “soft-state”, refreshed by the data packet
sent by MT
• ICMP EchoRequest/EchoReply messages to refresh the routing path
when no package send by MT after a predefined timeout.
• SignatureRequest/SignatureReply messages for the
security issue
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SignatureRequest message
• <IP of MT, IP of ANG, rand, timestamp>
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SignatureReply message
• <SigReq fields,128-bit MD5 message digest calculated
with authentication key>
TIMIP- Micromobility
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1~4. Same as the power up procedure.
5. Crossover AR sends MT the RoutingUpdate message
through old routing path.
6. APs Exchange of RoutingUpdate/RoutingUpdateAck
messages down to the old AP, deleting the old entry relative
to the MT.
TIMIP- Micromobility
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Address Resolution Protocol (ARP) in TIMIP
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If the source and destination is in the same domain
but associated to the different AP, the ARP request
(obtain MAC address) will not reach its destination.
Configure the MTs with a special subnet mask of
255.255.255.255 and the ANG as the default router.
(APs performing proxy ARP of the ANG with there
own MAC address)
TIMIP- Macromobility

Macro-mobility for MIP terminals
• When the MT support MIP but belongs to a different domain,
the ANG plays the role of FA.
• Handoffs between APs within the foreign domain are
handled by TIMIP micromobility procedure.
• The MT itself authenticate the MIP messages when
communicating with the HA.
• ANG broadcasts Router Advertisement message periodically
• MT receive RouterAd Msg, notify HA about the CoAddr
through the ANG
TIMIP- Macromobility
• Macro-mobility for legacy terminals
• K1：The Authentication key between the MT and ANG for TIMIP domain
• K2：The Authentication key of MT’s home network
MD5(k1,AuthenticationRequest)
MD5(k1,AuthenticationReply)
HA
Foreign ANG
MD5(k1,AuthenticationReply)
Registration
(MIP proxy)
AuthenticationRequest
<ANG IP,HA IP,MIP Registration Request,timestamp>
AuthenticationReply
MIP RegistrationRequest
MIP RegistrationReply
MD5(k2,MIP registration reply)
(mobile-home authentication extension)
ANG IP,HA IP
K1, k2
<ANG IP,HA IP,MD5(k2,MIP Registration Request),timestamp>
AuthenticationRequest
<ANG IP,HA IP,MIP Registration Reply(except the mobile-home authentication extension),timestamp>
AuthenticationReply
Match?
Key
database
MT
<ANG IP,HA IP,MD5(k2,MIP Registration Reply),timestamp>
TIMIP- Macromobility
• Macro-mobility for legacy terminals
• ANG de-encapsulates the tunneled IP packets
that come from the HA to the MT and forwards
them to the MH.
• MT must change IP gateway configuration
when moves to different domain.
• This inconvenience is avoided by configuring
the MTs with a well known ANG IP address
recognized by all APs of all TIMIP domain.
TIMIP- Context Transfer
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To assure seamless mobility, context information is
pertaining to active IP flows after routing path is
updated due to hand off
Context transfer Framework for Seamless Mobility
TIMIP- Context Transfer
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MT moves to New AP using SHIN
Required Changes
Old AP can send context info without receiving request. (using
USHREP), legacy terminal cannot provide the add of old AP to new
AP in SHIN/SHACK message
Old AP
New AP
MT
SHIN
Old AP address
SHACK
Old AP
New AP
U-SHREP
To MT
Legacy MT

SHREP-Ack
SHREQ
SHREP
SHIN : Seamless Handover Initiate
SHACK : Seamless Handover Acknowledgement
SHREQ : Seamless Handover Request
SHREP : Seamless Handover Reply
U-SHREP : Unsolicited Seamless Handover Reply
Conclusion
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In TIMIP, power-on and handoff are inferred from layer
2 notification at the wireless access points.

It can be implemented as an independent application
with no impact on the IP protocol stack.

Combined Ideas from CIP & HAWAII
• Ideas from CIP
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Refreshing of routing paths is performed by data packets sent by MT.
• Ideas from HAWAII
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Routing reconfiguration during handoff within a TIMIP domain only
needs to change the routing tables of the access routers located in
the shortest path between the new AP and the old AP.
Inter domain packet delivery does not require notification to ANG