Transcript Terminal Independent Mobility for IP

12 JUL 2002
Terminal Independent
Mobility for IP
(TIMIP)
Juitem@TeNET, KNU
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
compatible with those of SeaMoby WG’s to
support seamless hand-off
Terminal Independent Mobillity for IP
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
– Several IP micromobility models
•
•
•
•
MIP
HAWAII
CIP
These three proposals require change of legacy IP protocol
stacks to support mobility aware capability
Terminal Independent Mobillity for IP
IP Mobility in IETF
• Overview IP mobility in IETF
– Mobile IP
– Cellular IP
– Handoff Aware Wireless Access Internet
Architecture
Terminal Independent Mobillity for IP
Mobile IP
• RFC 2002
• Terminal has two address
– HAaddr
• 홈망에서 사용, 불변
– CoAddr
• 외부 망에 있는 동안 임시적으로 사용, 망에 따라 변화
• FA의 router advertisement message를 통해 획득
• HA & FA
– HA는 MT로 오는 모든 패킷을 받아 HAaddr로 또는 CoAddr로 터
널링
– FA는 터널을 통해 받은 패킷을 decapsulation하여 MT로 전달
• Triangular Routing & IP tunneling are difficult to
integrate with RSVP
Terminal Independent Mobillity for IP
Mobile IP
Dst=CoAddr
Dst=Haddr(MT)
Tunneling
Tunneling
Core
Network
Home
Tunneling
Network
Foreign
Tunneling
Network
FA
HA
MT
Dst=Haddr(MT)
Orig
Terminal Independent Mobillity for IP
HAWAII
•
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
Each domain owns a root gateway(Domain Root Router) => HA 역할
•
MT로 보내어지는 패킷은 일반적인 라우팅 프로토콜을 사용하여 먼저 DRR
에 도착, 그 다음 HAWAII 프로토콜 사용
•
Domain 내에서 이동할 시에는 IP 주소를 유지, 터널링 되지 않음
•
Path는 모바일 터미널의 일반적인 MIP registration message에 의해
trigger된다.
•
Domain 간의 이동시 Foreign Domain의 DRR이 FA역할을 하여 CoAddr할
당 및 터널링 되는 패킷을 수신
Terminal Independent Mobillity for IP
HAWAII
Core
Tunneling
Network
Foreign
domain
root
router
Home
domain
root
router
Router at
hierachical
level 1
Access
point
Intra
domain
hand
over
Inter
domain
hand
over
Terminal Independent Mobillity for IP
CIP
•
CIP는 handover를 predict하기 위해 layer-2 정보를 이용
MIP와 HAWAII layer-3 handover 과정은 MIP signaling에 의해 trigger
-> latency high, significant packet loss
•
마크로이동성은 MIP를 이용하여 지원하고 마이크로 이동성은 CIP프로토콜
을 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 노드까지
의 경로를 설정한 후 전달. 시스템의 과부화 방지
Terminal Independent Mobillity for IP
CIP – soft hand off
•Time out시 엔트리 삭제
•Data packet에의한 갱신
X: from G
X: from F,G
E
Gateway
router
Global Internet with Mobile IP
X: from F
X: from C
C
G
R
D
A
B
F
FA
X
Terminal Independent Mobillity for IP
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)
• AP에서 layer-2 hand off 기법을 사용하면 Terminal과
AP사이에 special IP layer signaling 이 필요치 않게된다.
(TIMIP)
Terminal Independent Mobillity for IP
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
macromobility
• Mobile terminal (MT)
– Runs the user applications
– Roaming between different APs performed by layer-2
Terminal Independent Mobillity for IP
TIMIP architecture
Access
point
(level 1)
Access
router
(level 2)
Core
Tunneling
network
Access
router
(level n-x)
Access
router
(level 2)
Access
point
(level 1)
Terminal Independent Mobillity for IP
Access
network
gateway
(level n)
TIMIP details
• Registration of MT on ANG
• PowerUP process를 통한 path 설정
• Path/Routing table의 관리
• Authentication 관리
• Macromobility for Legacy Terminals
• Macromobility for MIP Terminals
• Context Transfer
• Conclusion
Terminal Independent Mobillity for IP
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
Terminal Independent Mobillity for IP
Power-UP
• MT first appears in a TIMIP domain, routing
path is created along the hierarchy of ARs
4
2
1
Tunneling
Core
Network
3
Access
point
(level 1)
Access
router
(level 2)
5
Access
router
(level n-x)
Terminal Independent Mobillity for IP
Access
network
gateway
(level n)
Power Up process
•
1. The MT performs a layer-2 association
•
2. At the AP, layer-2에서 IP layer로 MT의 존재를 notify.
– MT가 MAC addr을 보내면 AP는 ANG가 보낸 terminal registration information
broadcast를 참조하여 IP를 매치시킨다
– AP는 자신의 routing entry에 MT를 등록
•
3. AP는 상위 레벨로 Routing 정보를 Update
•
4. RoutingUpdate/RoutingUpdateAck 를 사용하여 상위 레벨로 계속 갱신
되면서 routing path가 생성된다
•
5. ANG까지 도달하면 routing path creation을 중지(path가 만들어짐)
MT와 ANG가 만든 path 상에 있지 않은 AR들은 MT에 대한 routing table을
갖지 않으며, 이런 AR들이 MT로 향하는 패킷을 받게 되면 상위로 전달한다.
Terminal Independent Mobillity for IP
Routing Path
• Using RoutingUpdate/ACK message
– Message includes timestamp
– 모든 AP는 NTP로 동기화되어 있으므로 MT가 router
reconfiguration 보다 빠르게 이동할 경우에도 consistency 를
보장.
• Routing path is soft-state, refreshed by the data
packet sent by MT
• Soft-state에 의한 timeout 발생시, 해당 AR에서
– ICMP Echo Request를 source를 ANG로 set해서 MT로 보낸다
• 유효한 path라면 MT의 reply에 의해서 라우팅 테이블 유지
• 사라진 path라면 Routing Table에서 제거
(시간내에 reply를 받지 못할경우)
Terminal Independent Mobillity for IP
Authentication
• Unprotected IP networks, it allows MTs to power on with false
MAC & IP add
To avoid this, using authentication option field
– Authen.Opt field가 on이면, ANG의 DB와 MT의 키 값으로 인증
• Authentication Process
– Authentication takes place after powerup
– AP sends SignatureRequest to wellknown UDP port in the MT, to
ANG respectively
– 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>
Terminal Independent Mobillity for IP
Micromobility
Handoff between two AP s in same domain
Access
router
(level 2)
6
Access
router
(level n-x)
1
Access
router
(level 2)
2
3
Terminal Independent Mobillity for IP
Core
Tunneling
5
4
Networ
k
Access
network
gateway
(level n)
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 and 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.
Terminal Independent Mobillity for IP
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
Authentication key
» MT와 ANG인증 후, ANG와 HA인증
• ANG de-encapsulates the tunneled IP packet comes from HA
• ANG는 core network로 통하는 IP gateway 역할
Terminal Independent Mobillity for IP
Macromobility for legacy terminal
•
MT와 ANG인증
– 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.
•
ANG와 HA인증
– 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)
Terminal Independent Mobillity for IP
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 ANG
.
Terminal Independent Mobillity for IP
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 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 is configured to send a U-SHREP msg addressed to the terminal
new AP send SHREP-ack msg to old AP
Terminal Independent Mobillity for IP
Problems & Solution
• In Micro mobility
– Single subnet에서 (ex LAN) destination이 동일한
subnet내에 있지만 다른 AP를 이용할 경우
• ARP request는 destination의 MAC을 얻을 수 없다.
– 방안1. AP를 MT의 proxy ARP역할을 하도록 설정
» 설정 복잡, radio frequency에서 broadcast traffic 증가
– 방안2. AP를 ANG의 proxy로 설정
» ( 255.255.255.255for special subnet mask)
» (ANG as the default router)
» MT가 속한 local의 모든 AP로 ARP가 보내진다
Terminal Independent Mobillity for IP
Problems & Solution
• In Macromobility
– MT가 다른 TIMIP domain으로 이동할 경우 IP
Gateway 역할을 하는 ANG의 IP addr이 변경
된다
모든 TIMIP의 모든 AP가 인지할 수 있는 wellknown ANG IP로 MT를 config함으로써 해결
(well known ANG IP로 gratuitous ARP를 broadcast)
Terminal Independent Mobillity for IP
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
Terminal Independent Mobillity for IP
Reference
• Terminal Independent Mobility for IP
IEEE Communications Magazine Dec 2001
• Terminal Independent Mobile IP
draft-estrela-timip-00.txt
Expires: September 2002 March 2002
.
Terminal Independent Mobillity for IP