terminal independent mobility for ip (timip)

Terminal IndependentMobility for IP

(TIMIP)

Juitem@TeNET, KNU

12 JUL 2002

Terminal Independent Mobillity for IP


Abstract

• 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 macro-mobility• TIMIP uses context-transfer mechanisms compati

ble with those of SeaMoby WG’s 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 andto cross between router domains

• Layer-3 Mobility– Internet-wide mobility at the cost of more complex management– Several IP micromobility models

• MIP• HAWAII• CIP• These three proposals require change of legacy IP protocol stacks to

support mobility aware capability


IP Mobility in IETF

• Overview IP mobility in IETF– Mobile IP– Cellular IP– Handoff Aware Wireless Access Internet

Architecture


Mobile IP

• RFC 2002• Terminal has two address

– HAaddr• 홈망에서 사용 , 불변

– CoAddr• 외부 망에 있는 동안 임시적으로 사용 , 망에 따라 변화• FA 의 router advertisement message 를 통해 획득

• HA & FA– HA 는 MT 로 오는 모든 패킷을 받아 HAaddr 로 또는 CoAddr 로

터널링– FA 는 터널을 통해 받은 패킷을 decapsulation 하여 MT 로 전달

• Triangular Routing & IP tunneling are difficult to integrate with RSVP


TunnelingTunnelingHomeNetwork

Mobile IP

TunnelingTunnelingCoreNetwork TunnelingTunnelingForeign

Network

HA FA

MT

Orig

Dst=Haddr(MT)

Dst=Haddr(MT)

Dst=CoAddrTunneling


HAWAII• Special forwarding entries are installed on specific routers aware of the locat

ion of specific terminal

• Each domain is structured according to a hierarchy of nodes• Each domain owns a root gateway(Domain Root Router) => HA 역할

• MT 로 보내어지는 패킷은 일반적인 라우팅 프로토콜을 사용하여 먼저 DRR에 도착 , 그 다음 HAWAII 프로토콜 사용

• Domain 내에서 이동할 시에는 IP 주소를 유지 , 터널링 되지 않음

• Path 는 모바일 터미널의 일반적인 MIP registration message 에 의해 trigger된다 .

• Domain 간의 이동시 Foreign Domain 의 DRR 이 FA 역할을 하여 CoAddr할당 및 터널링 되는 패킷을 수신


HAWAII

TunnelingTunnelingCoreNetwork

Router athierachicallevel 1

Homedomainrootrouter

Intra domainhand over

Inter domainhand over

Foreigndomainrootrouter

Accesspoint


CIP• CIP 는 handover 를 predict 하기 위해 layer-2 정보를 이용

MIP 와 HAWAII layer-3 handover 과정은 MIP signaling 에 의해 trigger-> latency high, significant packet loss

• 마크로이동성은 MIP 를 이용하여 지원하고 마이크로 이동성은 CIP프로토콜을 이용하는 방식

• 이동 노드의 위치를 관리하기 위해 페이징 캐쉬와 라우팅 캐쉬를 사용– 페이징 캐쉬

• 서비스 지역내의 idle 상태의 호스트들의 대강의 위치정보저장– 라우팅 캐쉬

• 서비스 지역내의 액티브 이동 호스트의 위치를 짧은 시간단위로 추적하고 관리– Soft hand off 사용

=> 패킷이 전달 될 때에는 두 개의 캐쉬의 정보를 이용하여 이동 노드까지의 경로를 설정한 후 전달 . 시스템의 과부화 방지


CIP – soft hand off

C

A

B

E

D

F

GR

X: from C

X: from G

Global Internet with Mobile IP

FA

Gatewayrouter

X: from F,G

X: from F

X

C

A

B

E

D

F

GR

X: from C

X: from G

Global Internet with Mobile IP

FA

Gatewayrouter

X: from F,G

X: from F

X

•Time out 시 엔트리 삭제

•Data packet 에의한 갱신


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 various OS & version)

• AP 에서 layer-2 hand off 기법을 사용하면 Terminal 과 AP 사이에 special IP layer signaling 이 필요치 않게된다 .(TIMIP)


TIMIP• TIMIP

– TIMIP can be implemented in the network nodes and work transparently to the IP layer of the terminals

– Different Elements• Access router (AR)

– A number of access routers organize access network– Each router incorporates mobility management functions

• Access point (AP)– An AR that directly communicates with the mobile terminals at the radio

interface• Access Network Gateway (ANG)

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

bility• Mobile terminal (MT)

– Runs the user applications– Roaming between different APs performed by layer-2


TIMIP architecture

TunnelingTunnelingAccesspoint(level 1)

Accesspoint(level 1)

Accessrouter(level 2)


Accessrouter(level n-x)

Accessnetworkgateway(level n)

Corenetwork


TIMIP details• Registration of MT on ANG• PowerUP process 를 통한 path 설정• Path/Routing table 의 관리• Authentication 관리• Macromobility for Legacy Terminals• Macromobility for MIP Terminals• Context Transfer• Conclusion


Registration Info on ANG for MT

• In order for a terminal to be recognized by the TIMIP network, it has to be registered.(can be accomplished by offline)

• The ANG keeps information on all mobile terminals recognized by the mobile network

• 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


Power-UP

• MT first appears in a TIMIP domain, routing path is created along the hierarchy of ARs


1

2

3

4

5

Accesspoint(level 1)





Power Up process• 1. The MT performs a layer-2 association

• 2. At the AP, layer-2 에서 IP layer 로 MT 의 존재를 notify.– MT 가 MAC addr 을 보내면 AP 는 ANG 가 보낸 terminal registration information

broadcast 를 참조하여 IP 를 매치시킨다– AP 는 자신의 routing entry 에 MT 를 등록

• 3. AP 는 상위 레벨로 Routing 정보를 Update

• 4. RoutingUpdate/RoutingUpdateAck 를 사용하여 상위 레벨로 계속 갱신되면서 routing path 가 생성된다

• 5. ANG 까지 도달하면 routing path creation 을 중지 (path 가 만들어짐 )

MT 와 ANG 가 만든 path 상에 있지 않은 AR 들은 MT 에 대한 routing table을 갖지 않으며 , 이런 AR 들이 MT 로 향하는 패킷을 받게 되면 상위로 전달한다 .


Routing Path• Using RoutingUpdate/ACK message

– Message includes timestamp– 모든 AP 는 NTP 로 동기화되어 있으므로 MT 가 router reconfigu

ration 보다 빠르게 이동할 경우에도 consistency 를 보장 .

• Routing path is soft-state, refreshed by the data packet sent by MT

• Soft-state 에 의한 timeout 발생시 , 해당 AR 에서 – ICMP Echo Request 를 source 를 ANG 로 set 해서 MT 로

보낸다• 유효한 path 라면 MT 의 reply 에 의해서 라우팅 테이블 유지• 사라진 path 라면 Routing Table 에서 제거

( 시간내에 reply 를 받지 못할경우 )


Authentication• Unprotected IP networks, it allows MTs to power on with false MAC &

IP addTo avoid this, using authentication option field– Authen.Opt field 가 on 이면 , ANG 의 DB 와 MT 의 키 값으로 인증

• Authentication Process – Authentication takes place after powerup– AP sends SignatureRequest to wellknown UDP port in the MT, to ANG re

spectively– Receive Reply both from MT& ANG– 두 메시지가 match 되면 , routing table update

• SignatureRequest message– <IP of MT, IP of ANG, rand, timestamp>

• SignatureReply message– <SigReq fields,

128-bit MD5 message digest calculated with authentication key>


MicromobilityHandoff between two AP s in same domain






6

1

23

4

5


Micromobility(Con’t)• 1~4 same as those of the power-up procedure

• 5. Exchange of RoutingUpdate / ACK messages climb up the hierarchy levels, until the crossover AR– Crossover AR(AR which belongs simultaneously to the old path an

d to the new path)– Crossover AR starts the deletion of old routing path

• AR send a RoutingUpdate message to MT through the old route path, and detects not accessible

• 6. Exchange of RoutingUpdate/ACK messages goes down the AR tree following the old path, until the OLD AP is reached.


Macromobility for legacy terminal

• When MT(Legacy) enters a TIMIP domain

– terminal is locally authenticated and a routing path is created between the MT and the ANG

– Conferring registration information, the ANG realizes it is a foreign MT and it does not implement MIP

– Constantly, ANG must act as a MIP proxy on behalf of the MT• Notify the HA about MT’s CoAddr

– CoAddr is obtained by RegistrationRequest Msg– Registration Mgs needs Authentication, ANG does not know MT’s Authen

tication key» MT 와 ANG 인증 후 , ANG 와 HA 인증

• ANG de-encapsulates the tunneled IP packet comes from HA• ANG 는 core network 로 통하는 IP gateway 역할


Macromobility for legacy terminal

• MT 와 ANG 인증– ANG send MT authenticationReq msg

• <IP of ANG, IP add of HA, MIP Registraion Request, timestamp> which is authenticated by ANG with MD5

– MD5(K1, AuthenticationRequ)» K1 : Autientication key between MT & ANG in TIMIP domain

– MT finds K1 in key DB, obtain K2(authentication key of HA)– MT answer AuthenticationReply

• <IP of ANG, IP of HA, MD5(K2, MIP Reg Req), timestamp> which is authenticated by the terminal with MD5

– MD5(k1, Autientication Reply)– ANG send authenticated MIP Registration Request msg to HA.

• ANG 와 HA 인증– ANG send AuthenticationReq to MT

• <IP of ANG, IP of HA, MIP REG reply, timestamp> authenticated with MD5– MD5( K1, MIP Registration Repky)

– MT answer with AuthenticationReply• <IP of ANG, IP of HA, MD5, timestamp

– MD5( K2, MIP Registration Repky)


Macromobility for MIP Terminals

• When MT supports MIP, belongs to different domain ANG acts as FA– MT powers-on in the same way as legacy MTs– ANG broadcasts Router Advertisement message periodically– MT receive RouterAd Msg, notify HA about the CoA through the A

NG

.


Context Transfer• Context Transfer

– To assure seamless mobility, context information is pertaining to active IP flows after routing path is updated due to hand off

– Context information can be related to security, header compression, QoS, ans so on

– Compatible with Seamoby WG’s context transfer

– MT moves to New AP using SHIN(seamless Handover Initiate)• New AP answer ACK• New AP send SHREQ(seamless Handover Request) to old AP usin ICMP message option.• New AP receive reply from old AP

– Required ChangesOld 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 is configured to send a U-SHREP msg addressed to the terminal new AP send SHREP-ack msg to old AP


Problems & Solution

• In Micro mobility– Single subnet 에서 (ex LAN) destination 이 동일한

subnet 내에 있지만 다른 AP 를 이용할 경우• ARP request 는 destination 의 MAC 을 얻을 수 없다 .

– 방안 1. AP 를 MT 의 proxy ARP 역할을 하도록 설정» 설정 복잡 , radio frequency 에서 broadcast traffic 증가

– 방안 2. AP 를 ANG 의 proxy 로 설정» ( 255.255.255.255for special subnet mask)» (ANG as the default router)» MT 가 속한 local 의 모든 AP 로 ARP 가 보내진다


Problems & Solution

• In Macromobility– MT 가 다른 TIMIP domain 으로 이동할 경우 IP

Gateway 역할을 하는 ANG 의 IP addr 이 변경된다모든 TIMIP 의 모든 AP 가 인지할 수 있는 well-kno

wn ANG IP 로 MT 를 config 함으로써 해결(well known ANG IP 로 gratuitous ARP 를 broadcast)


Conclusion• In TIMIP, power-on and handover are inferred from layer-2

notification at the wireless access points.

• IP mobility signaling is completely implemented in the network nodes and thus transparent to the IP layer of the terminals

• MT’s authentication function can be implemented as an independent application

• Combined Ideas from CIP & HAWAII– Ideas from CIP

• Refreshing of routing paths is performed by data packets sent by MT– Ideas 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


Reference• Terminal Independent Mobility for IP

IEEE Communications Magazine Dec 2001

• Terminal Independent Mobile IPdraft-estrela-timip-00.txtExpires: September 2002 March 2002

.

terminal independent mobility for ip (timip)

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