Network Layer Mobile IP Slides adapted from Prof. Dr.-Ing. Jochen H. Schiller and W. Stallings 1
Mobile IP - Definition Mobile IP (MIP) is a modification to IP that allows nodes to continue to receive datagrams no matter where they happen to be attached to the Internet 2
3 Mobile IP Concept Mobile IP adds mobility support to the Internet network layer protocol IP. The Internet started at a time when no-one had a concept of mobile computers. The Internet of today lacks mechanisms for the support of users traveling through the world. IP is the common base for thousands of applications and runs over dozens of different networks; this is the reason for supporting mobility at the IP layer. Motivation for Mobile IP: Routing based on IP destination address, network prefix determines physical subnet Change of physical subnet implies change of IP address to have a topological correct address (standard IP) or needs special entries in the routing tables
4 Create specific routes to end-systems mobile nodes? change of all routing table entries to forward packets to the right destination does not scale with the number of mobile hosts and frequent changes in the location Changing the IP address? adjust the host IP address depending on the current location almost impossible to find a mobile host, DNS has not been built for frequent updates TCP connection break
Mobile IP Requirements Transparency mobile end-systems keep their IP address continuation of communication after interruption of link possible point of connection to the fixed network can be changed Compatibility support of the same layer 2 protocols as IP does no changes to current end-systems and routers required Mobile end-systems can communicate with fixed systems Security authentication of all registration messages Efficiency and scalability only little additional messages to the mobile system required (connection typically via a low bandwidth radio link) world-wide support of a large number of mobile systems in the whole Internet 5
Real-life Solution Take up the analogy of you moving from one apartment to another. What do you do? Leave a forwarding address with your old post-office The old post-office forwards mail to your new postoffice, which then delivers it to you 6
MIPv4: Overview MIPv4 Nodes MN (Mobile Node): Host CN (Correspondent Node): Host HA (Home Agent): Router FA (Foreign Agent): Router MIPv4 Address HoA (Home Address): MN CoA (Care-of-Address): FA CNP 7/50
MIPv4 Agents Home Agent (HA) & Foreign Agent (FA) CNP 8/50
Home Address (HoA) and Care-of Address (CoA) CNP 9/50
Protocols Operation Agent Discovery Registration Data Transfer CNP 10/50
MIPv4: Control Operations Agent Discovery MN FA (CoA) ICMP Agent Solicitation & Advertisement Registration to HA (via FA) MN FA HA Over UDP (destination port 434) Data Tunneling CN => HA (HoA) => FA (CoA) => MN IP-in-IP Tunneling,.. CNP 11/50
Mobile IP in detail MN FA HA MIPv4 CN MN FA HA MIPv6 CN 1 3 -- CoA and HA Discovery -- 2 1. CoA Discovery 2. HA Discovery Request 3. HA Discovery Reply 1 3 -- CoA and HA Discovery -- 2 1. CoA Discovery 2. HA Discovery Request 3. HA Discovery Reply 5 -- Registration Procedure -- 4 4. HA Registration through FA 5. HA Registration Ack. -- MN is Registered with HA -- 5 -- Registration Procedure -- 4 4. HA Registration BU 5. HA Registration BU Ack. -- MN is Registered with HA -- 8a 10a -- CN starts communication with MN -- 6 7 8 10 9 6. Data Packet 7. IP-in-IP Encapsulation 8. Tunneled Data 8a Detunnelled Data 9. Binding Update 10. IP-in-IP tunneling 10a. Detunnelled Data 8 10 -- CN starts communication with MN -- 6 7 9 6. Data Packet 7. IP-in-IP Encapsulation 8. Tunneled Data 9. Binding Update 10. Binding Ack -- MN starts communication with CN -- -- Discovery and Registration as above -- -- MN starts communication with CN -- -- Discovery and Registration as above -- 6a 6a. Data Packet 6a 6a. Data Packet -- Signals 6-10a as above -- -- Signals 6-10 as above -- 12
Discovering the care-of address Discovery process built on top of an existing standard protocol: router advertisements Router advertisements extended to carry available care-of addresses called: agent advertisements Foreign agents (and home agents) send agent advertisements periodically A mobile host can choose not to wait for an advertisement, and issue a solicitation message 13
Agent advertisements Foreign agents send advertisements to advertise available care-of addresses Home agents send advertisements to make themselves known Mobile hosts can issue agent solicitations to actively seek information If mobile host has not heard from a foreign agent its current care-of address belongs to, it seeks for another care-of address 14
Agent advertisement MIP does not use a new packet type for agent advertisement; it uses the router advertisement packet of ICMP, and appends an agent advertisement message. CNP 15/50
Registering the Care-of Address Once mobile host receives care-of address, it registers it with the home agent A registration request is first sent to the home agent (through the foreign agent) Home agent then approves the request and sends a registration reply back to the mobile host Security? 16
Registration Illustration 17
Home agent discovery If the mobile host is unable to communicate with the home agent, a home agent discovery message is used The message is sent as a broadcast to the home agents in the home network 18
Tunneling to the Care-of address When home agent receives packets addressed to mobile host, it forwards packets to the care-of address How does it forward it? - encapsulation The default encapsulation mechanism that must be supported by all mobility agents using mobile IP is IPwithin-IP Using IP-within-IP, home agent inserts a new IP header in front of the IP header of any datagram 19
Tunneling (contd.) Destination address set to the care-of address Source address set to the home agent s address After stripping out the first header, IP processes the packet again 20
Tunneling Illustration 21
Encapsulation original IP header original data new IP header new data outer header inner header original data
Encapsulation I Encapsulation of one packet into another as payload e.g. IPv6 in IPv4 (6Bone), Multicast in Unicast (Mbone) here: e.g. IP-in-IP-encapsulation, minimal encapsulation or GRE (Generic Record Encapsulation) IP-in-IP-encapsulation (mandatory, RFC 2003) tunnel between HA and COA ver. IHL DS (TOS) IP identification TTL IP-in-IP IP address of HA Care-of address COA ver. IHL DS (TOS) IP identification TTL lay. 4 prot. IP address of CN IP address of MN length flags fragment offset IP checksum length flags fragment offset IP checksum TCP/UDP/... payload
Encapsulation II Minimal encapsulation (optional) avoids repetition of identical fields e.g. TTL, IHL, version, DS (RFC 2474, old: TOS) only applicable for non fragmented packets, no space left for fragment identification ver. IHL DS (TOS) length IP identification flags fragment offset TTL min. encap. IP checksum IP address of HA care-of address COA lay. 4 protoc. S reserved IP checksum IP address of MN original sender IP address (if S=1) TCP/UDP/... payload
Mobile IPv6 (MIPv6) MIPv6 = MIPv4 + IPv6 Major Differences from MIPv4 FA in MN No FA for MIPv6 CoA: IP address of MN By DHCPv6 or IPv6 Stateless Auto-Configuration Route Optimization To solve the Triangular Routing Problem Provided by default MN CN CNP 25/50
MIP: Triangular Routing Problem CNP 26/50
MIPv6: Route Optimization CNP 27/50
MIPv6: Binding Update Binding Update to HA Using IPSEC: MN and HA have a security association AH (Authentication Header) ESP (Encapsulating Security Payload) Binding Update to CN Return Routability (RR) procedure For Security Binding Update (BU) procedure Route Optimization CNP 28/50
MIPv6: Binding Update CNP 29/50
MIPv6: RR (Return Routability) CNP 30/50
MIPv6: Changes to IPv6 New IPv6 Protocol (Header) Mobility Header: a new IPv6 extension header To carry MIPv6 Binding Update messages How is in the MIPv4? New Option in Destination Option Header Home Address Option New Type in Routing Header Type 2 Routing Header New ICMP Messages ICMP HA Address Discovery Request/Reply ICMP Mobile Prefix Solicitation/ Advertisement CNP 31/50
MIPv6: IPv6 Header CNP 32/50
MIPv6: Mobility Header A New Extension Header of IPv6 Messages for Return Routability Home Test Init Message Care-of Test Init Message Home Test Message Care-of Test Message CNP Messages for Binding Update Binding Update Message Binding Acknowledgement Message Binding Error Message Binding Refresh Request Message 33/50
MIP Extensions Mobile IPv4 (MIPv4) Low-Latency Handover for MIPv4 (FMIPv4) Regional Registration for MIPv4 (HMIPv4) Mobile IPv6 (MIPv6) Fast Handover for MIPv6 (FMIPv6) Hierarchical MIPv6 (HMIPv6) CNP 34/50
FMIPv6: Fast Handover for MIPv6 CN PAR NAR signaling signaling MN CNP 35/50
FMIPv6: Operations Handover Initiation L2 Triggers, RtSolPr, PrRtAdv Between MN and AR Tunnel Establishment HI (Handover Initiate) and HACK Between PAR and NAR Packet Forwarding PAR => NAR (data buffering at NAR) FBU, FBack NAR => MN: FNA (Fast NA) CNP 36/50
FMIPv6: Operational Flows CNP 37/50
HMIPv6: Overview Motivations Localized (Regional) Mobility Management Hierarchical MIP: MN HA HMIP: MN MAP HA MAP: Mobility Anchor Point IP Address (CoA) RCoA (Regional CoA): in the MAP region LCoA (On-Link CoA): in the AR region CNP 38/50
HMIPv6: Architecture HA CN MAP RCoA AR1 MN LCoA_1 AR2 Movement LCoA_2 CNP 39/50
HMIPv6: Operations MN When entering an AR region in the MAP domain, it gets LCoA (AR region) and RCoA (MAP region) RCoA does not change in the MAP domain Local Binding Update (LBU) to MAP Bind LCoA & RCoA to MAP MAP (Acting as a local HA) Only the RCoA need to be registered with CN/HA Relay all packets between MN and HA/CN CNP 40/50
HMIPv6: MAP Tunnel (MAP MN) HA CN MAP AR1 MN AR2 Outer header Inner header LCoA MAP RCoA CN Home Addr CNP 41/50
Hierarchical MIP HMIPv4 HMIPv6 MN FA1 RFA1 GFA -- CoA and HA Discovery -- HA/CN MN MA HA/CN 1 3 5d 4a 9 10a 2 -- Registration Procedure -- 4b 4c 5b 5a 5c -- MN moves from FA1 to FA2 -- FA2 RFA2 COS 6 7 8 10 11 11a 4d 1. CoA Discovery 2. HA Discovery Request 3. HA Discovery Reply 4a. Registration Request 4b. Registration Request w/extension 4c. Registration Request w/extension 4d. Registration Request 5a. Registration Reply 5b. Registration Reply w/extension 5c. Registration Reply w/extension 5d. Registration Reply -- MN is Registered with HA -- 6. Reg Reg w/ Previous FA Notification 7. Reg. Reg w/ Hierarchical FA ext. 8. Reg. Reg w/ Hierarchical FA ext. 9. BU to previous FA 10. BU to Crossover Router 10a. BU Ack 1 3 5 7 -- CoA and HA Discovery -- 2 -- Registration Procedure -- 4 4 6 1. CoA Discovery 2. HA Discovery Request 3. HA Discovery Reply -- Sequential Method -- 4. MA Registration BU 5. MA Reg. BU Acknowledgement -- MN is Registered with MA -- 6. HA Registration BU 7. HA Reg. BU Acknowledgement -- MN is Registered with HA -- -- Encapsulated Method -- 4. MA/HA Registration BU 12 11. BU to Crossover Router 11a. BU ack 12. Reply 7 6 5 5. HA Registration BU 6. HA Reg. BU Acknowledgement 7. HA Reg. BU Acknowledgement -- MN is Registered with HA and MA-- 42
MIP in Real World: 3GPP2 (CDMA) CNP 43/50
MIP in 3GPP2 CNP 44/50
Proxy MIPv6 (PMIPv6) Network-based Localized Mobility Management
Why Network-based? Host-based MIPv4/v6 has not been yet deployed that much. Why host-based MIP is not deployed yet? Too heavy specification for a small terminal RFC 3344 (MIPv4): 99 pages RFC 3775 (MIPv6): 165 pages Battery problem Waste of air resource No Stable MIPv4/v6 stack executed in Microsoft Windows OS CNP 46/50
PMIPv6 IETF NETLMM WG Internet Draft Proxy Mobile IPv6, draft-ietf-netlmm-proxymip6-00.txt (2007) GOAL This protocol is for providing mobility support to any IPv6 host within a restricted and topologically localized portion of the network and without requiring the host to participate in any mobility related signaling. CNP 47/50
Technical Background Host-based vs. Network-based Mobility HA HA Route Update Route Update AR AR Movement Host-based Mobility Movement Network-based Mobility CNP 48/50
Proxy MIPv6 Overview IP Tunnel A IPinIP tunnel LMA and MAG. LMA: Localized Mobility Agent MAG: Mobile Access Gateway MN s Home Network Prefix (MN-HNP) CAFE:1:/64 MAG1 LMA Home Network MN s Home Network (Topological Anchor Point) Host A MAG2 LMM (Localized Mobility Management) Domain LMA Address (LMAA) That will be the tunnel entrypoint. MN s Home Network Prefix (MN-HNP) CAFE:2:/64 CNP Host B MN Home Address (MN-HoA) MN continues to use it as long as it roams within a same domain Proxy Care of Address (Proxy-CoA) The address of MAG. That will be the tunnel end-point. Proxy Binding Update (PBU) Control message sent out by MAG to LMA to register its correct location 49/50
Proxy MIPv6 Overview No host stack change for IP mobility Avoiding tunneling overhead over the air Re-use of Mobile IPv6 PMIPv6 is based on Mobile IPv6 [RFC3775] Only supports Per-MN-Prefix model Unique home network prefix assigned for each MN. The prefix follows the MN. CNP 50/50
Proxy MIPv6 Overview Overall Procedures 1. MN moves and attaches to an access router 2. After authentication, MAG (access router) identifies MN 3. MAG obtains MN s profile containing the Home Address..etc 4. MAG sends the Proxy Binding Update to LMA on behalf of MN 5. MAG receives the Proxy Binding Ack. from LMA 6. MAG sends Router Advertisements containing MN s home network prefix Stateless Case: MN will still configure (or maintain) the same as its home address. Stateful Case: the network will ensure that it always gets its home address. 51/50
Proxy MIPv6 Overview DHCP Relay Agent MN Access to a new IP link MAG MN-Identifier AAA Server (Policy Store) DHCP Server LMA MN-Identifier AAA Request In case that profile store does not have MN Home Prefix MAG emulates the MN s home link Router Advertisement AAA Reply + Policy Profile Proxy Binding Update Proxy Binding Ack. (MN Home Prefix) Tunnel Setup DHCP Request DHCP Response DHCP Request DHCP Response This can be omitted when stateless configuration is used. 52/50
Proxy MIPv6 Proxy Registration LMA needs to understand the Proxy Registration. Proxy Binding Update Proxy Binding Acknowledgement 53/50
Proxy MIPv6 Tunnel Management LMA-MAG tunnel is a shared tunnel among many MNs. 1:1 relation m:1 relation One tunnel is associated to multiple MNs Binding Caches. Life-time of a tunnel should not be dependent on the life time of any single BCE. LMA s Prefix-based Routing LMA will add prefix routes to MN s home network prefix over the tunnel. CNP 54/50
Proxy MIPv6 MAG Operation It emulates the home link for each MN. After the access authentication, MAG will obtain MN s profile which contains: MN s home address MN s home network prefix LMA address..etc. It establishes a IPv6/IPv6 tunnel with the LMA. All the packets from MN are reverse tunneled to its LMA All the packets from the tunnel are routed to MN. Router Advertisement should be UNICASTed to CNP an MN 55/50
Proxy MIPv6 MN Operation Any MN is just a IPv6 host with its protocol operation consistent with the base IPv6 specification. All aspects of Neighbor Discovery Protocol will not change. When MN attaches to a new AR, it receives a Router Advertisement message from the AR with its home prefix. Throughout the PMIP domain, MN using DHCP procedure or in stateless address configuration mode, will obtain the same home address. CNP 56/50
Proxy MIPv6 Data Transport LMA-MAG Tunneling/Reverse Tunneling MN MAG LMA CN MN sends a packet to CN MAG sends to MN MAG forwards to LMA LMA forwards to MAG LMA sends to CN CN sends packet to MN IPv6 header (src=mag_addr, dst=lma_addr) IPv6 header (src=mn_addr, dst=cn_addr) Payload IPv6 header (src=lma_addr, dst=mag_addr) IPv6 header (src=cn_addr, dst=mn_addr) Paylaod CNP 57/50
MIPV6 EXPERIMENTAL EVALUATION 58
Protocol Handover Signaling Mobile Node Foreign Agent Home Agent Corespondent Node Router Solicitation Router Advertisement Binding update Neighbor Solicitation Neighbor Advertisement Binding Acknowledgement L2 Latency L3 Movement Detection DAD Home Test Init Care-of Test Init Home Test Care-of Test Registration Delay Binding update Binding Acknowledgement
Handover Latency Analysis Signaling Link Layer Establishment Delay (D L2 ): The time required by the physical interface to establish a new association. This is the L2 handover between access routers. Movement Detection (D RD ): The time required for the mobile node to receive beacons from the new access router, after disconnecting from the old AR. Duplicate Address Detection (D DAD ): The time required to recognize the uniqueness of an IPv6 address. BU/Registration Delay (D REG ): The time elapsed between the sending of the BU from the MN to the HA and the arrival/transmission of the first packet through the new access router.
Handover Latency Analysis The handover delay for MIPv6 can analytically be computed as: D MIPv6 =D L2 + D RD + D DAD + D REG The delays can be further broken down to: D MIPv6 = (T PRB + T AUTH + T RASS ) + (T RSOL + T RADV ) + D DAD + (T HBU + T HBA + 2T HOTI + 2T HOT + T CBU + T CBA )
Techniques to reduce overall handoff latency L2 Trigger Optimistic Duplicate Address Detection Fast Beacons Fast Solicited Router Advertisements
2001:1a18:1:9:: MN MIPv6 Testbed IPv6 Network 2001:1a18:1:10:: MN The experimental testbed consists of three wireless LANs connected through an IPv6 cloud. FA Visited subnet CN Correspondent subnet 2001:1a18:1:2:: HA Home subnet Twenty experiments were run for each configuration and the average times are computed and analyzed.
List of Equipment and Software Mobile Node Home Agent Foreign Agent Corresponded Node IBM ThinkPad T42p Acer Veriton 9100 Dell Optiplex GX1 Dell Optiplex GX1 Intel Pentium M 1.86GHz Intel Pentium 4 1500MHZ Intel Pentium III 50OMHz Intel Pentium III 500MHz 2048 cache 256 cache 512 cache 512 cache Atheros AR5212 802.11abg NIC D-Link, PCI IEEE802.11b card, GWL-520, Atheros chipset Auto channel Channel 1 Channel 6 LINUX, Fedora Core 5, kernel 2.6.16 MIPL v2.02
MIPv6 Testbed Parameters Parameter Value Parameter Value mtu 1500 MinRouterAdv 0.03-1s (0.5) autoconf 1 MaxRouterAdv 0.07-1.5s (1.5) forwarding 1 (MN=0) DAD On / Off (On) Home / Co Test Init 1 Beacon Interval 50-100 ms (100) Rt. Solicitation 1 BU 1.5
Handoff Latency time We forced the MN to perform hard handoff with the command iwconfig We measured the handoff time as follows: D L2+RD= T RECEPTIONOFRA - T IWCONFIG D DAD =T BUHA -T RECEPTIONOFRA D REG =D HAREG +D CNREG D HAREG =T BACKHA -T BUHA D CNREG =T BACKCN -T BUCN
Results With default values of RA=0.5-1.5, DAD on, Beacon Interval 100 ms the Total Handoff Time is DMIPv6 = 3.68 sec. D L2+RD =0.612s, D DAD = 1.414s and D REG = 1.651s The major share in the handover latency goes to D REG. The BU and registration functions account for 45% of the total delay. The DAD function takes another 38% and the movement detection (including the L2 delay) accounts for the rest 17%.
Results DAD component contribution to the MIPv6 Handover Latency Handoff Latency RA=0.5-1.5 1=DAD on+beacon Interval=100ms 2=DAD on+beacon Interval=60ms 3=DAD off+beacon Interval=100ms 4=DAD off+beacon Interval=60ms REG-CN REG-HA DAD L2+RD Total Handoff Latency(sec) 4 3.5 3 2.5 2 1.5 1 0.5 0 1 2 3 4 When the DAD function is switched off the respective delay is reduced by almost 1sec which is the default timer value for this operation. If we operate in a controlled environment where the probability of duplicate addresses is negligible, then we can discard the DAD function and achieve a decrease in the total MIPv6 delay of at most one second.
Results Router Advertisement Interval effect on handover component latencies Handoff Latency RA Interval 1=0.03-0.07, 2=0.04-0.08, 3=0.07=0.11, 4=0.1-0.5, 5=0.5-1.5 REG-CN REG-HA DAD L2+RD 1.8 1.6 Latency(sec) 1.4 1.2 1 0.8 0.6 0.648477 0.4 0.2 0.1512074 0.16558 0.162878 0.30285 0 1 2 3 4 5 The change in the RA interval only affects the combined D L2 + D RD. We observe a 200-400% reduction in the corresponding delay between the default and lower values.
Results Router Advertisement Interval effect on overall handover latency. The effect on the overall handover delay is not as dramatic since the contribution of the D RD delay to the total is only 17%.
Results 0,7 Router Advertisement and Beacon Interval L2 and RD Delays 1=0.1-0.3RA, 2=0.2-0.6RA, 3=0.3-0.9RA, 4=0.4-1.2RA, 5=0.5-1.5RA 0,6 L2 and RD Delays 0,5 0,4 0,3 0,2 0,1 0 Beacon Interval=100 Beacon Interval=80 Beacon Interval=60 1 2 3 4 5 Adjust the ranges using MinRouterAdvintervals between 0.1 and 0.5 sec. 300% reduction in an almost linear manner. The figure is appended with plots of different Beacon Intervals, which do not provide any insight to their importance.
Results Handover delay vs Router Advertisement and Beacon interval L2 Handoff (Beacon Interval-Router Adv) L2 Handoff 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 100 80 Beacon Interval 60 0 0.3 0.6 0.9 1.2 Max Router Advertisement Combined contribution of RA interval and Beacon interval on lower layer delays. 1.5 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2