Terminal Independent Mobility for IP (TIMIP)

António Grilo, Pedro Estrela, Mário Nunes, INESCIST, PORTUGALIEEE 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

New Architecture for IP mobility in wireless New Architecture for IP mobility in wireless access networksaccess networks

Based on principles similar to those in the Based on principles similar to those in the CIP and HAWAII architecturesCIP and HAWAII architectures

Suited for Suited for micro-mobilitymicro-mobility scenarios scenarios Still usingStill using MIP for macromobility MIP for macromobility TIMIP uses TIMIP uses context-transfer mechanismscontext-transfer mechanisms to

support seamless hand-off

Introduction Layer-2 MobilityLayer-2 Mobility

• Easy to accomplish & already supported (eg. Wireless LAN)Easy to accomplish & already supported (eg. Wireless LAN)• Does not allow terminalDoes not allow terminal

to roam between different LANs andto roam between different LANs andto cross between router domainsto cross between router domains

Layer-3 MobilityLayer-3 Mobility• Internet-wide mobility at the cost of more complex Internet-wide mobility at the cost of more complex

mmanagementanagement• Macromobility scenariosMacromobility scenarios

MIPMIP• micromobility micromobility scenariosscenarios

HAWAIIHAWAII CIPCIP

• These three proposals require change of legacy IP protocol These three proposals require change of legacy IP protocol stacks to support mobility aware capabilitystacks to support mobility aware capability

Overview IP Mobility in IETF

• Mobile IPMobile IP• HAWAIIHAWAII• Cellular IPCellular IP

Overview IP Mobility in IETFMobile IPMobile IP

Mobile IP• Could be used in both micromobility and macromo

bility scenarios.

• Terminal has two address home address (HAddr) care-of address (CoAddr)

• HA & FA Home agent (HA) Foreign agent (FA)

• Tunnel

TunnelingTunnelingHomeNetwork

Overview IP Mobility in IETFMobile IPMobile IP

TunnelingTunnelingCore Network TunnelingTunnelingForeign

Network

HA FA

Orig

TunnelingMT

(CoAddr)

Original PacketSrc=Orig, dst= HAddr

Tunneled PacketSrc=Orig, dst= CoAddr

Original PacketSrc=Orig, dst= HAddr

Overview IP Mobility in IETFMobile IPMobile 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 HAWAIIHAWAII

• HAWAII• (Handoff-Aware Wireless Access Internet Infrastructure)

• HAWAII was proposed in order to solve the QoS and efficiency issues of MIP

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

Retain same address when moving within domain. MIP procedure is used when the terminal moves to a foreign d

omain.

HAWAIIHAWAII

TunnelingTunnelingCore Network

Router athierachical

level 1

Intra domainhand over

Inter domainhand over(MIP)

Foregindomain

rootrouter

Accesspoint

MT MTMT

Homedomain

rootrouter

Overview IP Mobility in IETF Cellular IPCellular IP

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 IPCellular IP

Paging cachesPaging caches Routing cachesRouting caches

C

A

B

E

D

F

GR

X: from C

X: from G

Global Internet with Mobile IP

FA

Gatewayrouter C

A

B

E

D

F

GR

X: from C

Global Internet with Mobile IP

FA

Gatewayrouter

X: from F,GX: from F,GX: from F

MT

Paging-update

G times out

TIMIP

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) The root AR, interfacing with the core IP network Perform mobility management functions to support MIP-

based macromobility

• Access router (AR) Each AR incorporates mobility management functions

• Access point (AP) Is an AR that directly communicates to MT

• Mobile terminal (MT) Runs the user applications Roaming between different APs performed by layer-2

TIMIP- Architecture

Accesspoint

(level 1)

Accesspoint

(level 1)

Accessrouter

(level 2)

Accessrouter

(level 2)

Accessrouter

(level n-x)

Accessnetworkgateway(level n).

TunnelingTunnelingCore network

...

...

...

MT

MT

MT

MT

TIMIP

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 th

e APs, avoids the need for special IP layer signaling between the terminal and the AP.

TIMIP- Registration Info on ANG for MT

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.

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 RoutingUpdate/RoutingUpdateAck messages reaches the ANG, completes t

he routing path

TIMIP- Power UP

Accesspoint

(level 1)

Accesspoint

(level 1)

Accessrouter

(level 2)

Accessrouter

(level 2)

Accessrouter

(level n-x)

Accessnetworkgateway(level n).

TunnelingTunnelingCore network

...

...

...

MT

1

2

RoutingUpdate

updates routing table

RoutingUpdateACK3RoutingUpdate

RoutingUpdateACK

updates routing table

RoutingUpdate

RoutingUpdateACK

4 5

TIMIP- Power UP

Routing Update/ACK message includes timestamp • All APs are synchronized by means of the Network Ti

me 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 SignatureRequest messageSignatureRequest message

• <IP of MT, IP of ANG, rand, timestamp><IP of MT, IP of ANG, rand, timestamp> SignatureReply messageSignatureReply message

• <SigReq fields,128-bit MD5 message digest calculated <SigReq fields,128-bit MD5 message digest calculated with authentication key>with authentication key>

TIMIP- Micromobility

1~4. Same as the power up procedure. 5. Crossover AR sends MT the RoutingUpdate message th

rough old routing path. 6. APs Exchange of RoutingUpdate/RoutingUpdateAck m

essages down to the old AP, deleting the old entry relative to the MT.

TIMIP- Micromobility

Address Resolution Protocol (ARP) in TIMIP If the source and destination is in the same domain but a

ssociated 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

HAForeign ANG

MT(MIP proxy)

Keydatabase

Registration

AuthenticationRequest<ANG IP,HA IP,MIP Registration Request,timestamp> ANG IP,HA IP

K1, k2AuthenticationReply

<ANG IP,HA IP,MD5(k2,MIP Registration Request),timestamp>

MIP RegistrationRequest

MIP RegistrationReplyMD5(k2,MIP registration reply)

(mobile-home authentication extension)

MD5(k1,AuthenticationReply)

AuthenticationRequest<ANG IP,HA IP,MIP Registration Reply(except the mobile-home authentication extension),timestamp>

MD5(k1,AuthenticationRequest)

AuthenticationReply<ANG IP,HA IP,MD5(k2,MIP Registration Reply),timestamp>Match?

MD5(k1,AuthenticationReply)

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

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

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

SHACK

SHIN

SHREQ

SHREP

Old AP address

Old AP New AP Legacy MT

SHREP-Ack

U-SHREP To MT

SHIN : Seamless Handover InitiateSHACK : Seamless Handover AcknowledgementSHREQ : Seamless Handover RequestSHREP : Seamless Handover ReplyU-SHREP : Unsolicited Seamless Handover Reply

Conclusion In TIMIP, power-on and handoff are inferred from In TIMIP, power-on and handoff are inferred from layer 2layer 2 noti noti

fication at the wireless access points.fication at the wireless access points.

It can be implemented as an independent application with It can be implemented as an independent application with nno impact on the IP protocol stacko impact on the IP protocol stack..

Combined Ideas from CIP & HAWAIICombined Ideas from CIP & HAWAII• Ideas from CIPIdeas from CIP

Refreshing of routing paths is performed by data packets sent by MT.• Ideas from HAWAIIIdeas from HAWAII

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