mobile ip, Mobile COmmunication Internet Protocol
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Mobile IP adds mobility support to the Internet network layer protocol IP. It allows nodes to continue receiving datagrams no matter where they are attached to the Internet. Mobile IP uses home agents and foreign agents to tunnel packets to a mobile node's current location, represented by its care-of address. When away from its home network, a mobile node registers its care-of address with its home agent. The home agent intercepts packets destined for the mobile node and tunnels them to the care-of address using encapsulation. This allows the mobile node to maintain its home IP address while connecting via foreign networks.
mobile ip, Mobile COmmunication Internet Protocol
- 1. EPL476 Mobile Networks Mobile Network Protocols Instructor: Dr. Vasos Vassiliou Slides adapted from Prof. Dr.-Ing. Jochen H. Schiller and W. Stallings
- 3. 3 Mobile IP (I) 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. 4 Mobile IP (II) 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
- 5. 5 Mobile IP (III) Requirements to Mobile IP: 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
- 6. 6 Mobile IP (IV) 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
- 7. 7 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 post-office, which then delivers it to you
- 8. 8 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”
- 9. 9 Mobile IP (V) Terminology: Mobile Node (MN) • system (node) that can change the point of connection to the network without changing its IP address Home Agent (HA) • system in the home network of the MN, typically a router • registers the location of the MN, tunnels IP datagrams to the COA Foreign Agent (FA) • system in the current foreign network of the MN, typically a router • forwards the tunneled datagrams to the MN, typically also the default router of the MN
- 10. 10 Mobile IP (VI) Care-of Address (COA) • address of the current tunnel end-point for the MN (at FA or MN) • actual location of the MN from an IP point of view • can be chosen, e.g., via DHCP Correspondent Node (CN) • communication partner
- 11. 11 Mobile IP in detail … Combination of 3 separable mechanisms: Discovering the care-of address Registering the care-of address Tunneling to the care-of address
- 12. 12 CN 2. HA Discovery Request 3. HA Discovery Reply 4. HA Registration through FA 5. HA Registration Ack. 1. CoA Discovery MN HA 1 2 3 -- MN is Registered with HA -- 4 55 -- CoA and HA Discovery -- -- Registration Procedure -- -- CN starts communication with MN -- 6. Data Packet 7. IP-in-IP Encapsulation 8. Tunneled Data -- Signals 6-10a as above -- 8 77 6a. Data Packet -- MN starts communication with CN -- 8a Detunnelled Data 9. Binding Update 6a6a -- Discovery and Registration as above -- FA 8a 66 10 10. IP-in-IP tunneling 99 10a 10a. Detunnelled Data CN 2. HA Discovery Request 3. HA Discovery Reply 4. HA Registration BU 5. HA Registration BU Ack. 1. CoA Discovery MN HA 1 2 3 -- MN is Registered with HA -- 4 55 -- CoA and HA Discovery -- -- Registration Procedure -- -- CN starts communication with MN -- 6. Data Packet 7. IP-in-IP Encapsulation 8. Tunneled Data -- Signals 6-10 as above -- 8 77 6a. Data Packet -- MN starts communication with CN -- 9. Binding Update 6a6a -- Discovery and Registration as above -- FA 66 10 10. Binding Ack 99 MIPv4 MIPv6 Mobile IP in detail
- 13. 13 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
- 14. 14 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
- 15. 15 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?
- 17. 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. 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 IP-within-IP Using IP-within-IP, home agent inserts a new IP header in front of the IP header of any datagram
- 19. 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
- 21. 21 (current physical network for the MN) home network (physical home network for the MN) Mobile IP (VII) Example network Internet router HA MN router FA foreign network routerend-system CN
- 22. 22 Mobile IP (VIII) Data transfer to the mobile system Internet home network foreign network FA HA MN receiver 1 2 3 sender CN 1. Sender sends to the IP address of MN, HA intercepts packet 2. HA tunnels packet to COA, here FA, by encapsulation 3. FA forwards the packet to the MN
- 23. 23 foreign network home network Mobile IP (IX) Data transfer from the mobile system Internet HA MN sender receiver CN 1. Sender sends to the IP address of the receiver as usual, FA works as default router FA 1
- 24. 24 Mobile IP (XIII) Optimization of packet forwarding: Triangular routing • sender sends all packets via HA to MN • higher latency and network load Solutions – optimization • HA informs a sender about the location of MN • sender learns the current location of MN • direct tunneling to this location • big security problems!
- 25. 25 Mobile IP (XIV) Change of FA • Packets on-the-fly during the change can be lost • new FA informs old FA to avoid packet loss, old FA forwards remaining packets to new FA • this information also enables the old FA to release resources for the MN
- 26. 26 Mobile IP (XV) Change of the foreign agent with the optimized mobile IP CN HA FAold FAnew MN t request update ACK data data MN changes locationregistration update ACKdata data data warning update ACK data data registration
- 27. 27 Mobile IP (XVI) Reverse tunneling: Internet receiver FA HA MN home network foreign network sender 3 2 1 1. MN sends to FA 2. FA tunnels packets to HA by encapsulation 3. HA forwards the packet to the receiver (standard case) CN
- 28. 28 Mobile IP (XVII) Mobile IP with reverse tunneling Router accept often only “topological correct“ addresses (firewall!) • a packet from the MN encapsulated by the FA is now topological correct • furthermore multicast and TTL problems solved (TTL in the home network correct, but MN is to far away from the receiver) Reverse tunneling does not solve • problems with firewalls, the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking) • optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (double triangular routing) The standard is backwards compatible • the extensions can be implemented easily and cooperate with current implementations without these extensions • Agent Advertisements can carry requests for reverse tunneling
- 29. 29 [modified from Ericsson Tech. Rep. 11/0362-FCB, Dec Mobile IP in detail
- 30. type = 16 length = 6 + 4 * #COAs R: registration required B: busy, no more registrations H: home agent F: foreign agent M: minimal encapsulation G: GRE encapsulation r: =0, ignored (former Van Jacobson compression) T: FA supports reverse tunneling reserved: =0, ignored Agent advertisement preference level 1 router address 1 #addresses type addr. size lifetime checksum COA 1 COA 2 type = 16 sequence numberlength 0 7 8 15 16 312423 code preference level 2 router address 2 . . . registration lifetime . . . R B H F M G r reservedT
- 31. Registration t MN HAregistrationrequest registration reply t MN FA HAregistrationrequest registrationrequest registration reply registration reply
- 32. Mobile IP registration request home agent home address type = 1 lifetime 0 7 8 15 16 312423 T x identification COA extensions . . . S B DMG r S: simultaneous bindings B: broadcast datagrams D: decapsulation by MN M mininal encapsulation G: GRE encapsulation r: =0, ignored T: reverse tunneling requested x: =0, ignored
- 33. Mobile IP registration reply home agent home address type = 3 lifetime 0 7 8 15 16 31 code identification extensions . . .Example codes: registration successful 0 registration accepted 1 registration accepted, but simultaneous mobility bindings unsupported registration denied by FA 65 administratively prohibited 66 insufficient resources 67 mobile node failed authentication 68 home agent failed authentication 69 requested Lifetime too long registration denied by HA 129 administratively prohibited 131 mobile node failed authentication 133 registration Identification mismatch 135 too many simultaneous mobility bindings
- 34. Encapsulation original IP header original data new datanew IP header outer header inner header original data
- 35. 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 Care-of address COA IP address of HA TTL IP identification IP-in-IP IP checksum flags fragment offset lengthDS (TOS)ver. IHL IP address of MN IP address of CN TTL IP identification lay. 4 prot. IP checksum flags fragment offset lengthDS (TOS)ver. IHL TCP/UDP/ ... payload
- 36. 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 care-of address COA IP address of HA TTL IP identification min. encap. IP checksum flags fragment offset lengthDS (TOS)ver. IHL IP address of MN original sender IP address (if S=1) Slay. 4 protoc. IP checksum TCP/UDP/ ... payload reserved
- 37. Generic Routing Encapsulationoriginal header original data new datanew header outer header GRE header original data original header Care-of address COA IP address of HA TTL IP identification GRE IP checksum flags fragment offset lengthDS (TOS)ver. IHL IP address of MN IP address of CN TTL IP identification lay. 4 prot. IP checksum flags fragment offset lengthDS (TOS)ver. IHL TCP/UDP/ ... payload routing (optional) sequence number (optional) key (optional) offset (optional)checksum (optional) protocolrec. rsv. ver.CRK S s RFC 1701 RFC 2784 (updated by 2890) reserved1 (=0)checksum (optional) protocolreserved0 ver.C
- 38. 38 Route Optimizations Enable direct notification of the corresponding host Direct tunneling from the corresponding host to the mobile host Binding cache maintained at corresponding host
- 39. 39 Route optimizations (contd.) 4 types of messages Binding update Binding request Binding warning Binding acknowledge
- 40. 40 Binding Update When a home agent receives a packet to be tunneled to a mobile host, it sends a binding update message to the corresponding host When a home agent receives a binding request message, it replies with a binding update message Also used in the the smooth-handoffs optimization
- 41. 41 Binding Update (Contd.) Corresponding host caches binding and uses it for tunneling subsequent packets Lifetime of binding? Corresponding host that perceives a near-expiry can choose to ask for a binding confirmation using the binding request message Home agent can choose to ask for an acknowledgement to which a corresponding host has to reply with a binding ack message
- 42. 42 Binding warning When a foreign agent receives a tunneled message, but sees no visitor entry for the mobile host, it generates a binding warning message to the appropriate home agent When a home agent receives a warning, it issues an update message to the corresponding host What if the foreign agent does not have the home agent address (why?) ?
- 43. 43 Binding Update and Warning Home Agent Foreign AgentCorresponding Host Mobile Host BU BW BW BR BA
- 44. Optimization of packet forwarding Problem: Triangular Routing sender sends all packets via HA to MN higher latency and network load “Solutions” sender learns the current location of MN direct tunneling to this location HA informs a sender about the location of MN big security problems! Change of FA packets on-the-fly during the change can be lost new FA informs old FA to avoid packet loss, old FA now forwards remaining packets to new FA this information also enables the old FA to release resources for the MN
- 45. Change of foreign agent CN HA FAold FAnew MN MN changes location t Data Data Data Update ACK Data Data RegistrationUpdate ACK Data Data Data Warning Request Update ACK Data Data
- 46. Reverse tunneling (RFC 3024, was: 2344) Internet receiver FA HA MN home network foreign network sender 3 2 1 1. MN sends to FA 2. FA tunnels packets to HA by encapsulation 3. HA forwards the packet to the receiver (standard case) CN
- 47. Mobile IP with reverse tunneling Router accept often only “topological correct“ addresses (firewall!) a packet from the MN encapsulated by the FA is now topological correct furthermore multicast and TTL problems solved (TTL in the home network correct, but MN is to far away from the receiver) Reverse tunneling does not solve problems with firewalls, the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking) optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (double triangular routing) The standard is backwards compatible the extensions can be implemented easily and cooperate with current implementations without these extensions Agent Advertisements can carry requests for reverse tunneling
- 48. 48 Mobile IP and IPv6 Mobile IP was developed for IPv4, but IPv6 simplifies the protocols security is integrated and not an add-on, authentication of registration is included COA can be assigned via auto-configuration (DHCPv6 is one candidate), every node has address autoconfiguration no need for a separate FA, all routers perform router advertisement which can be used instead of the special agent advertisement; addresses are always co-located MN can signal a sender directly the COA, sending via HA not needed in this case (automatic path optimization) „soft“ hand-over, i.e. without packet loss, between two subnets is supported • MN sends the new COA to its old router • the old router encapsulates all incoming packets for the MN and forwards them to the new COA • authentication is always granted
- 49. 49 Problems with mobile IP Security authentication with FA problematic, for the FA typically belongs to another organization no protocol for key management and key distribution has been standardized in the Internet patent and export restrictions Firewalls typically mobile IP cannot be used together with firewalls, special set-ups are needed (such as reverse tunneling) QoS many new reservations in case of RSVP tunneling makes it hard to give a flow of packets a special treatment needed for the QoS Security, firewalls, QoS etc. are topics of current research and discussions!
- 50. 50 Security in Mobile IP Security requirements (Security Architecture for the Internet Protocol, RFC 1825) Integrity any changes to data between sender and receiver can be detected by the receiver Authentication sender address is really the address of the sender and all data received is really data sent by this sender Confidentiality only sender and receiver can read the data Non-Repudiation sender cannot deny sending of data Traffic Analysis creation of traffic and user profiles should not be possible Replay Protection receivers can detect replay of messages
- 51. not encrypted encrypted IP security architecture I Two or more partners have to negotiate security mechanisms to setup a security association typically, all partners choose the same parameters and mechanisms Two headers have been defined for securing IP packets: Authentication-Header • guarantees integrity and authenticity of IP packets • if asymmetric encryption schemes are used, non-repudiation can also be guaranteed Encapsulation Security Payload • protects confidentiality between communication partners Authentification-HeaderIP-Header UDP/TCP-Paketauthentication headerIP header UDP/TCP data ESP headerIP header encrypted data
- 52. Mobile Security Association for registrations parameters for the mobile host (MH), home agent (HA), and foreign agent (FA) Extensions of the IP security architecture extended authentication of registration prevention of replays of registrations • time stamps: 32 bit time stamps + 32 bit random number • nonces: 32 bit random number (MH) + 32 bit random number (HA) registration reply registration request registration request IP security architecture II MH FA HA registration reply MH-HA authentication MH-FA authentication FA-HA authentication
- 53. Key distribution Home agent distributes session keys foreign agent has a security association with the home agent mobile host registers a new binding at the home agent home agent answers with a new session key for foreign agent and mobile node FA MH HA response: EHA-FA {session key} EHA-MH {session key}
- 54. 54 Recap Host mobility and Internet addresses Post-office analogy Home agent, foreign agent, care-of address, home address Registration and Tunneling Mobile IP problems Mobile IP Optimizations Other options
Editor's Notes
- #8: Same Principle as call forwarding!
- #9: Same Principle as call forwarding!
- #12: Going back to the basic process we can have all the functions acting independently.
- #13: These diagrams show the different signaling messages needed to establish a mobile IP connection and communication. The diagram on the left is for MIPv4 and the one on the right is for MIPv6 In MIPv4 we see that the HA is the one taking care of the triangular routing, whereas is MIPv6 this responsibility is delegated to the mobile node. IPv6 and MIPv6 were designed from the beginning with mobility in mind and support these functions in a more simple way
- #30: USE POINTER Mobile IP (MIP) allows IP nodes to maintain connectivity while moving A Mobile Node (MN) is assigned a Care-of Address (CoA) when it moves to a foreign sub-network The COA can be an address obtained by the FA OR AN ADDRESS OBTAINED DYNAMICALLY The Home Agent will intercept and tunnel all packets to the MNs CoA A Foreign Agent (FA) or the MN will de-tunnel the packets and eventually set up a direct connection with the CH via an Optimal Route