Lecture 15

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Lecture 15

  1. 1. <ul><li>What if we use a Mobile computer in an internet straight away? </li></ul><ul><li>Host sends the IP packet with the destination address and other fields. </li></ul><ul><li>The destination address determines the sub-net that the host belongs to and also the host address. </li></ul><ul><li>Ex., 129.13.42.99 specifies that the physical subnet with prefix 129.13.42 is to be connected to. </li></ul><ul><li>If the receiver has moved outside the subnet area, the packet will not reach. </li></ul><ul><li>Thus, a host needs a topologically correct address. But if the host keeps changing the physical address, it is impossible to keep track of it. </li></ul><ul><li>**** Mobile IP is the answer to these issues****** </li></ul>Mobile Network Layer
  2. 2. <ul><li>Routing </li></ul><ul><ul><li>based on IP destination address, network prefix (e.g. 129.13.42) determines physical subnet </li></ul></ul><ul><ul><li>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 </li></ul></ul><ul><li>Specific routes to end-systems? </li></ul><ul><ul><li>change of all routing table entries to forward packets to the right destination </li></ul></ul><ul><ul><li>does not scale with the number of mobile hosts and frequent changes in the location, security problems </li></ul></ul><ul><li>Changing the IP-address? </li></ul><ul><ul><li>adjust the host IP address depending on the current location </li></ul></ul><ul><ul><li>almost impossible to find a mobile system, DNS updates take to long time </li></ul></ul><ul><ul><li>TCP connections break, security problems </li></ul></ul>Mobile Network Layer
  3. 3. Requirements to Mobile IP <ul><li>Transparency </li></ul><ul><ul><li>mobile end-systems keep their IP address, Mobility to be transparent to higher layers. </li></ul></ul><ul><ul><li>continuation of communication after interruption of link possible </li></ul></ul><ul><ul><li>point of connection to the fixed network can be changed </li></ul></ul><ul><li>Compatibility </li></ul><ul><ul><li>support of the same layer 2 protocols as IP </li></ul></ul><ul><ul><li>no changes to current end-systems and routers required </li></ul></ul><ul><ul><li>mobile end-systems can communicate with fixed systems </li></ul></ul><ul><li>Security </li></ul><ul><ul><li>authentication of all registration messages </li></ul></ul><ul><li>Efficiency and scalability </li></ul><ul><ul><li>only little additional messages to the mobile system required (connection typically via a low bandwidth radio link) </li></ul></ul><ul><ul><li>world-wide support of a large number of mobile systems in the whole Internet </li></ul></ul>
  4. 4. Terminology <ul><li>Mobile Node (MN) </li></ul><ul><ul><li>system (node) that can change the point of connection to the network without changing its IP address </li></ul></ul><ul><li>Home Agent (HA) </li></ul><ul><ul><li>system in the home network of the MN, typically a router </li></ul></ul><ul><ul><li>registers the location of the MN, tunnels IP datagrams to the COA </li></ul></ul><ul><ul><li>The tunnel for the packets for the MN starts at the HA. </li></ul></ul><ul><ul><li>HA maintains a location registry. The current COA informs the HA about the current location of the MN. </li></ul></ul><ul><li>Foreign Agent (FA) </li></ul><ul><ul><li>system in the current foreign network of the MN, typically a router </li></ul></ul><ul><ul><li>forwards the tunneled datagrams to the MN, typically also the default router for the MN </li></ul></ul><ul><li>Care-of Address (COA) </li></ul><ul><ul><li>address of the current tunnel end-point for the MN (at FA or MN) </li></ul></ul><ul><ul><li>actual location of the MN from an IP point of view </li></ul></ul><ul><ul><li>can be chosen, e.g., via DHCP </li></ul></ul><ul><li>Correspondent Node (CN) </li></ul><ul><ul><li>communication partner, CN can be a fixed or a mobile node. </li></ul></ul>
  5. 5. Two Possibilities for COA Location <ul><li>Foreign Agent COA : COA located at the FA. </li></ul><ul><ul><li>COA is the IP address of the FA. FA is the tunnel end point and forwards packets to the MN. </li></ul></ul><ul><ul><li>Many MNs using the FA can share the COA. </li></ul></ul><ul><li>Co-located COA </li></ul><ul><ul><li>If the MN temporarily acquires an additional IP address, this IP address can act as COA. One problem with co-located MNs is that it uses additional IP address which is scarce generally. </li></ul></ul>
  6. 6. Example network Internet router router router end-system FA HA MN home network foreign network (physical home network for the MN) (current physical network for the MN) CN
  7. 7. Data transfer to the mobile system Internet sender FA HA MN home network foreign network receiver 1 2 3 1. Sender sends to the IP address of MN, HA intercepts packet (proxy ARP) 2. HA tunnels packet to COA, here FA, by encapsulation 3. FA forwards the packet to the MN CN
  8. 8. Data transfer from the mobile system Internet receiver FA HA MN home network foreign network sender 1 1. Sender sends to the IP address of the receiver as usual, FA works as default router CN
  9. 9. Overview CN router HA router FA Internet router 1. 2. 3. home network MN foreign network 4. CN router HA router FA Internet router home network MN foreign network COA
  10. 10. Further definitions … <ul><li>Mobile Node(MN): </li></ul><ul><li>It is a mobile device or Router that can change its point of attachment to internet by the use of Mobile IP. </li></ul><ul><li>Correspondent Node(CN) : This is a partner needed for communication. CN can be fixed or mobile. </li></ul><ul><li>Home Network : Subnet that the MN belongs to. No mobile IP support is needed within the home network. </li></ul><ul><li>Foreign Network : Current network that the mobile is visiting. </li></ul><ul><li>- Can have a Care of Address (COA) that can act as a tunnel for sending the packets to an MN. </li></ul><ul><li>- Can be a default router for the MN </li></ul><ul><li>- Can provide security </li></ul><ul><li>- Typically, it is implemented on the router for the subnet that the MN attaches to. </li></ul><ul><li>COA : Marks the tunnel end point; IT is the IP address of the FA. </li></ul>
  11. 11. Further definitions … <ul><li>IP Packet Delivery </li></ul><ul><li>CN wants to send an IP packet to MN </li></ul><ul><li>CN does not need to know the IP address of MN. MN is the destination address. </li></ul><ul><li>The internet routes the packet to the router of the home network that the packet belongs to. </li></ul><ul><li>HA intercepts the packet, being aware that MN is not in its home network. </li></ul><ul><li>The packet is encapsulated and tunneled to the COA. A new header is put in front of the old IP header showing COA as the new destination and HA as the source of the encapsulated packet. </li></ul><ul><li>The Foreign Agent(FA) now decapsulates the packet, I.e, removes the additional header and forwards the original packet with CN as source and MN as destination to MN. </li></ul>
  12. 12. Network Integration <ul><li>Agent Advertisement </li></ul><ul><ul><li>HA and FA periodically send advertisement messages into their physical subnets </li></ul></ul><ul><ul><li>MN listens to these messages and detects, if it is in the home or a foreign network (standard case for home network) </li></ul></ul><ul><ul><li>MN reads a COA from the FA advertisement messages </li></ul></ul><ul><li>Registration (always limited lifetime!) </li></ul><ul><ul><li>MN signals COA to the HA via the FA, HA acknowledges via FA to MN </li></ul></ul><ul><ul><li>these actions have to be secured by authentication </li></ul></ul><ul><li>Advertisement </li></ul><ul><ul><li>HA advertises the IP address of the MN (as for fixed systems), i.e. standard routing information </li></ul></ul><ul><ul><li>routers adjust their entries, these are stable for a longer time (HA responsible for a MN over a longer period of time) </li></ul></ul><ul><ul><li>packets to the MN are sent to the HA, </li></ul></ul><ul><ul><li>independent of changes in COA/FA </li></ul></ul>
  13. 13. Agent Advertisement <ul><li>Foreign Agents(FSs) and Home Agents(HAs) Advertise their presents periodically via the Agent Advt Messages. - beacon broadcast to the subnet. </li></ul><ul><li>Upper part of the packet represents the ICMP (Advt Intenet Control Message Protocol) </li></ul><ul><li>Lower part represents the mobility. </li></ul>
  14. 14. Agent Advertisement 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 preference level 1 router address 1 #addresses type addr. size lifetime checksum COA 1 COA 2 type = 16 sequence number length 0 7 8 15 16 31 24 23 code preference level 2 router address 2 . . . registration lifetime . . . R B H F M G r reserved T ICMP : Internet Control Message Protocol Mobility Extension
  15. 15. Agent Advt Packet <ul><li>Type : set to 9 </li></ul><ul><li>Code =0 if the agent also routes packets from non-mobile nodes </li></ul><ul><li>=16 if it does not route anything other than mobiles nodes </li></ul><ul><li>#addresses: no. of addresses advertised with this packet </li></ul><ul><li>Addresses follow. </li></ul><ul><li>Life time: length of time that these advts are valid. </li></ul><ul><li>Mobile extensions : </li></ul><ul><li>- type : set to 16 </li></ul><ul><li>- length = 6 + 4*no. of addresses. </li></ul><ul><li>- sequence no. : total no. of advts sent since initialisation. </li></ul><ul><li>- COA 1, COA 2… : COAs advertised. </li></ul>
  16. 16. Agent Solicitation <ul><li>If no advertisements are received in a specified interval, and if an MN has not received a COA by any other means, MN must send Agent Solicitation messages. </li></ul><ul><li>MN searches for a FN through these messages. When MNs are moving at a good pace, <1 sec interval solicitations are required so that packets are not lost. </li></ul><ul><li>If a MN does not receive reply to its solicitations, it must reduce the solicitation interval to avoid flooding of network traffic. </li></ul><ul><li>At the End of Advts and Solicitation: </li></ul><ul><li>MN receives a COA, either for a FA or for a co-located COA. </li></ul>
  17. 17. Registration <ul><li>The main purpose of Registration is to inform HA of the current location for correct forwarding of packets. </li></ul><ul><li>If the COA is at the FA </li></ul><ul><li>- MN sends a registration request via contained in COA to FA. </li></ul><ul><li>FA forwards this request to HA. </li></ul><ul><li>HA sets up a mobility binding that contains MN’s home IP address and the current COA. </li></ul><ul><li>Registration expires after the life time. </li></ul><ul><li>After setting up mobility, the FA sends a reply back to FA that forwards the same to MN </li></ul>
  18. 18. Registration <ul><li>If the COA is collocated… </li></ul><ul><li>MN sends the request directly to HA and vice versa. </li></ul>
  19. 19. Registration t MN HA registration request registration reply t MN FA HA registration request registration request registration reply registration reply Registration of the MN via FA (Case 1) Registration Directly (If COA is collocated) (Case 2)
  20. 20. Registration <ul><li>Case-1: </li></ul><ul><li>MN sends the Reg request to FA. FA forwards this to HA </li></ul><ul><li>HA sets up a mobility binding that contains MN’s home IP address and the current COA. </li></ul><ul><li>After setting up mobility binding, the HA sends a reply back to FA and FA forwards the same to MN. </li></ul><ul><li>Case –2: </li></ul><ul><li>MN sends a Reg. Request to HA and HA replies to this request. </li></ul>
  21. 21. Mobile IP Registration Request (UDP packet format) home agent home address type = 1 lifetime 0 7 8 15 16 31 24 23 T x identification COA extensions . . . 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 Having received a COA, MN has to register with HA. The main purpose of registration is to inform the HA of the current location for for correct forwarding of packets. S B D M G r
  22. 22. Mobile IP Registration Request (UDP packet format) <ul><li>Type set to 1 : Registration required </li></ul><ul><li>S bit enabled : MN can specify if it wants the HA to retain the prior mobility bindings, It allows simultaneous bindings </li></ul><ul><li>B set to 1 : indicates that MN also wants to receive the broadcast packets which have been received by the HA in the home network. </li></ul><ul><li>D Bit : indicates that the MN uses a collocated COA and it carries out decapsulation at tunel end point. </li></ul><ul><li>M & G : Whether minimal encapsulation or general encapsulation is required. </li></ul><ul><li>T indicates reverse tunneling. R & x are set to zero in this case. </li></ul>
  23. 23. Mobile IP Registration Reply home agent(addr of HA) home address(addr of MN) type = 3 lifetime 0 7 8 15 16 31 code Identification(64 bit - to match reg. Req with replies) 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
  24. 24. Encapsulation original IP header original data new data new IP header outer header inner header original data Original Header + Original Data COA
  25. 25. Encapsulation-1 – IP-in-IP Encapsulation Care-of address COA IP address of HA TTL IP identification IP-in-IP IP checksum flags fragment offset length DS (TOS) ver. IHL IP address of MN IP address of CN TTL IP identification lay. 4 prot. IP checksum flags fragment offset length DS (TOS) ver. IHL TCP/UDP/ ... payload <ul><li>Encapsulation of one packet into another as payload </li></ul><ul><ul><li>e.g. IPv6 in IPv4 (6Bone), Multicast in Unicast (Mbone) </li></ul></ul><ul><ul><li>here: e.g. IP-in-IP-encapsulation, minimal encapsulation or GRE (Generic Record Encapsulation) </li></ul></ul><ul><li>IP-in-IP-encapsulation (mandatory, RFC 2003) </li></ul><ul><ul><li>tunnel between HA and COA </li></ul></ul>New Header Original Header
  26. 26. Encapsulation-1 – IP-in-IP Encapsulation <ul><li>Ver : Ipv Ver 4 </li></ul><ul><li>IHL : Internet Header Length (length of the outer header in 32 bits) </li></ul><ul><li>DS(TOS-Type of Service) : Copied from the inner header </li></ul><ul><li>Length : length of completed encapsulated packet </li></ul><ul><li>IP Id, Flags, Fragmented Offset : No special meaning for Mobile IP </li></ul><ul><li>TTL (Time to Live) : Must be high enough so that packet can reach the tunnel end point. </li></ul><ul><li>IP-In-IP : Type of the protocol : 4 for IPv4 </li></ul><ul><li>IP Address of HA : Source Address </li></ul><ul><li>Care of Addr of COA : Tunnel exit point as destination address. </li></ul>
  27. 27. Encapsulation-II care-of address COA IP address of HA TTL IP identification min. encap. IP checksum flags fragment offset length DS (TOS) ver. IHL IP address of MN original sender IP address (if S=1) S lay. 4 protoc. IP checksum TCP/UDP/ ... payload reserved <ul><li>Minimal encapsulation (optional) </li></ul><ul><ul><li>avoids repetition of identical fields </li></ul></ul><ul><ul><li>e.g. TTL, IHL, version, DS (RFC 2474, old: TOS) </li></ul></ul><ul><ul><li>only applicable for unfragmented packets, no space left for fragment identification </li></ul></ul>
  28. 28. Generic Routing Encapsulation (GRE) Care-of address COA IP address of HA TTL IP identification GRE IP checksum flags fragment offset length DS (TOS) ver. IHL IP address of MN IP address of CN TTL IP identification lay. 4 prot. IP checksum flags fragment offset length DS (TOS) ver. IHL TCP/UDP/ ... payload routing (optional) sequence number (optional) key (optional) offset (optional) checksum (optional) protocol rec. rsv. ver. C R K S s RFC 1701 RFC 2784 reserved1 (=0) checksum (optional) protocol reserved0 ver. C <ul><li>Supports other other network layer protocols in addition to IP. </li></ul><ul><li>Allows encapsulation of the packets of one protocol suite into the payload portion of another protocol suite. </li></ul>original header original data new data new header outer header GRE header original data original header
  29. 29. Issue with Routing – Need for Optimization Japanese German Meeting at a conference in Hawaii
  30. 30. Issue with Routing – Need for Optimization <ul><li>Japanese sends a data to German </li></ul><ul><ul><li>Japanese computer sends a data to HA of German </li></ul></ul><ul><ul><li>HA in Germany encapsulates the packet and tunnels to the COA of the German Lap Top in Hawaii. </li></ul></ul><ul><ul><li>This is very inefficient since the lap tops are just meters apart. </li></ul></ul><ul><ul><li>The scheme is called Triangular Routing (CN->HA, HA->COA/MN, MN->back to CN). </li></ul></ul>
  31. 31. Optimization of Packet Forwarding <ul><li>Triangular Routing </li></ul><ul><ul><li>sender sends all packets via HA to MN </li></ul></ul><ul><ul><li>higher latency and network load </li></ul></ul><ul><li>“ Solutions” </li></ul><ul><ul><li>sender learns the current location of MN </li></ul></ul><ul><ul><li>direct tunneling to this location </li></ul></ul><ul><ul><li>HA informs a sender about the location of MN </li></ul></ul><ul><ul><li>big security problems! </li></ul></ul><ul><li>Change of FA </li></ul><ul><ul><li>packets on-the-fly during the change can be lost </li></ul></ul><ul><ul><li>new FA informs old FA to avoid packet loss, old FA now forwards remaining packets to new FA </li></ul></ul><ul><ul><li>this information also enables the old FA to release resources for the MN </li></ul></ul>
  32. 32. Change of Foreign Agent CN HA FA old FA new MN MN changes location t Data Data Data Update ACK Data Data Registration Update ACK Data Data Data Warning Request Update ACK Data Data
  33. 33. Change of Foreign Agent <ul><li>Binding Request : CN sends a request to HA for the current location of HA </li></ul><ul><li>Binding Update : If MN has allowed dissemination of the current location, it can send an update. </li></ul><ul><li>Binding ACK : CN acknowledges this update message and stores the mobility binding. CN can directly send the data to the current foreign agent(Faold). Faold forwards the packets to MN. </li></ul><ul><li>Binding Warning : If a node decapsulates a packet for MN but it is not the correct FA for the MN, this node sends a binding warning. The recipient knows that it has to get a fresh binding. </li></ul><ul><li>Tunneling and Encapsulation is now done by CN and not HA. </li></ul>
  34. 34. Change of Foreign Agent <ul><li>MN changes the Location : </li></ul><ul><li>MN changes location and registers with a new foreign agent FAnew. </li></ul><ul><li>This registration is forwarded to HA for Location Database Update. FAnew informs FAold about the current registration of MN. This is done via an update message. Faold acknowledges it. </li></ul><ul><li>CN acknowledges this update and stores the mobility binding. </li></ul><ul><li>Now, CN can send the Data directly to FAold. </li></ul>
  35. 35. 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
  36. 36. Mobile IP with Reverse Tunneling <ul><li>Router accept often only “topological correct“ addresses (firewall!) </li></ul><ul><ul><li>a packet from the MN encapsulated by the FA is now topological correct </li></ul></ul><ul><ul><li>furthermore multicast and TTL problems solved (TTL in the home network correct, but MN is to far away from the receiver) </li></ul></ul><ul><li>Reverse tunneling does not solve </li></ul><ul><ul><li>problems with firewalls , the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking) </li></ul></ul><ul><ul><li>optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (double triangular routing) </li></ul></ul><ul><li>The standard is backwards compatible </li></ul><ul><ul><li>the extensions can be implemented easily and cooperate with current implementations without these extensions </li></ul></ul><ul><ul><li>Agent Advertisements can carry requests for reverse tunneling </li></ul></ul>
  37. 37. Mobile IP and IPv6 <ul><li>Mobile IP was developed for IPv4, but IPv6 simplifies the protocols </li></ul><ul><ul><li>security is integrated and not an add-on, authentication of registration is included </li></ul></ul><ul><ul><li>COA can be assigned via auto-configuration (DHCPv6 is one candidate), every node has address autoconfiguration </li></ul></ul><ul><ul><li>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 </li></ul></ul><ul><ul><li>MN can signal a sender directly the COA, sending via HA not needed in this case (automatic path optimization) </li></ul></ul><ul><ul><li>„ soft“ hand-over, i.e. without packet loss, between two subnets is supported </li></ul></ul><ul><ul><ul><li>MN sends the new COA to its old router </li></ul></ul></ul><ul><ul><ul><li>the old router encapsulates all incoming packets for the MN and forwards them to the new COA </li></ul></ul></ul><ul><ul><ul><li>authentication is always granted </li></ul></ul></ul>
  38. 38. Problems with Mobile IP <ul><li>Security </li></ul><ul><ul><li>authentication with FA problematic, for the FA typically belongs to another organization </li></ul></ul><ul><ul><li>no protocol for key management and key distribution has been standardized in the Internet </li></ul></ul><ul><ul><li>patent and export restrictions </li></ul></ul><ul><li>Firewalls </li></ul><ul><ul><li>typically mobile IP cannot be used together with firewalls, special set-ups are needed (such as reverse tunneling) </li></ul></ul><ul><li>QoS </li></ul><ul><ul><li>many new reservations in case of RSVP </li></ul></ul><ul><ul><li>tunneling makes it hard to give a flow of packets a special treatment needed for the QoS </li></ul></ul><ul><li>Security, firewalls, QoS etc. are topics of current research and discussions! </li></ul>
  39. 39. Security in Mobile IP <ul><li>Security requirements (Security Architecture for the Internet Protocol, RFC 1825) </li></ul><ul><ul><li>Integrity any changes to data between sender and receiver can be detected by the receiver </li></ul></ul><ul><ul><li>Authentication sender address is really the address of the sender and all data received is really data sent by this sender </li></ul></ul><ul><ul><li>Confidentiality only sender and receiver can read the data </li></ul></ul><ul><ul><li>Non-Repudiation sender cannot deny sending of data </li></ul></ul><ul><ul><li>Traffic Analysis creation of traffic and user profiles should not be possible </li></ul></ul><ul><ul><li>Replay Protection receivers can detect replay of messages </li></ul></ul>
  40. 40. IP Security Architecture-I <ul><li>Two or more partners have to negotiate security mechanisms to setup a security association </li></ul><ul><ul><li>typically, all partners choose the same parameters and mechanisms </li></ul></ul><ul><li>Two headers have been defined for securing IP packets: </li></ul><ul><ul><li>Authentication-Header </li></ul></ul><ul><ul><ul><li>guarantees integrity and authenticity of IP packets </li></ul></ul></ul><ul><ul><ul><li>if asymmetric encryption schemes are used, non-repudiation can also be guaranteed </li></ul></ul></ul><ul><ul><li>Encapsulation Security Payload </li></ul></ul><ul><ul><ul><li>protects confidentiality between communication partners </li></ul></ul></ul>ESP header IP header encrypted data not encrypted encrypted Authentification-Header IP-Header UDP/TCP-Paket authentication header IP header UDP/TCP data
  41. 41. IP Security Architecture-II registration reply registration request registration request MH FA HA registration reply MH-HA authentication MH-FA authentication FA-HA authentication <ul><li>Mobile Security Association for registrations </li></ul><ul><ul><li>parameters for the mobile host (MH), home agent (HA), and foreign agent (FA) </li></ul></ul><ul><li>Extensions of the IP security architecture </li></ul><ul><ul><li>extended authentication of registration </li></ul></ul><ul><ul><li>prevention of replays of registrations </li></ul></ul><ul><ul><ul><li>time stamps: 32 bit time stamps + 32 bit random number </li></ul></ul></ul><ul><ul><ul><li>nonces: 32 bit random number (MH) + 32 bit random number (HA) </li></ul></ul></ul>
  42. 42. Key Distribution <ul><li>Home agent distributes session keys </li></ul><ul><li>foreign agent has a security association with the home agent </li></ul><ul><li>mobile host registers a new binding at the home agent </li></ul><ul><li>home agent answers with a new session key for foreign agent and mobile node </li></ul><ul><li>foreign agent has a security association with the home agent </li></ul><ul><li>mobile host registers a new binding at the home agent </li></ul><ul><li>home agent answers with a new session key for foreign agent and mobile node </li></ul>FA MH HA response: E HA-FA {session key} E HA-MH {session key}
  43. 43. IP Micro Mobility Support <ul><li>Micro-mobility support: </li></ul><ul><ul><li>Efficient local handover inside a foreign domain without involving a home agent </li></ul></ul><ul><ul><li>Reduces control traffic on backbone </li></ul></ul><ul><ul><li>Especially needed in case of route optimization </li></ul></ul><ul><li>Example approaches: </li></ul><ul><ul><li>Cellular IP </li></ul></ul><ul><ul><li>HAWAII </li></ul></ul><ul><ul><li>Hierarchical Mobile IP (HMIP) </li></ul></ul><ul><li>Important criteria: Security Efficiency, Scalability, Transparency, Manageability </li></ul>
  44. 44. Cellular IP <ul><li>Operation: </li></ul><ul><ul><li>„ CIP Nodes“ maintain routing entries (soft state) for MNs </li></ul></ul><ul><ul><li>Multiple entries possible </li></ul></ul><ul><ul><li>Routing entries updated based on packets sent by MN </li></ul></ul><ul><li>CIP Gateway: </li></ul><ul><ul><li>Mobile IP tunnel endpoint </li></ul></ul><ul><ul><li>Initial registration processing </li></ul></ul><ul><li>Security provisions: </li></ul><ul><ul><li>all CIP Nodes share „network key“ </li></ul></ul><ul><ul><li>MN key: MD5(net key, IP addr) </li></ul></ul><ul><ul><li>MN gets key upon registration </li></ul></ul>CIP Gateway Internet BS MN1 data/control packets from MN 1 Mobile IP BS BS MN2 packets from MN2 to MN 1
  45. 45. Cellular IP : Security <ul><li>Advantages: </li></ul><ul><ul><li>Initial registration involves authentication of MNs and is processed centrally by CIP Gateway </li></ul></ul><ul><ul><li>All control messages by MNs are authenticated </li></ul></ul><ul><ul><li>Replay-protection (using timestamps) </li></ul></ul><ul><li>Potential problems: </li></ul><ul><ul><li>MNs can directly influence routing entries </li></ul></ul><ul><ul><li>Network key known to many entities (increases risk of compromise) </li></ul></ul><ul><ul><li>No re-keying mechanisms for network key </li></ul></ul><ul><ul><li>No choice of algorithm (always MD5, prefix+suffix mode) </li></ul></ul><ul><ul><li>Proprietary mechanisms (not, e.g., IPSec AH) </li></ul></ul>
  46. 46. Cellular IP : Other Issues <ul><li>Advantages: </li></ul><ul><ul><li>Simple and elegant architecture </li></ul></ul><ul><ul><li>Mostly self-configuring (little management needed) </li></ul></ul><ul><ul><li>Integration with firewalls / private address support possible </li></ul></ul><ul><li>Potential problems: </li></ul><ul><ul><li>Not transparent to MNs (additional control messages) </li></ul></ul><ul><ul><li>Public-key encryption of MN keys may be a problem for resource-constrained MNs </li></ul></ul><ul><ul><li>Multiple-path forwarding may cause inefficient use of available bandwidth </li></ul></ul>
  47. 47. HAWAII (Handoff Aware wireless access internet infrastructure) <ul><li>Operation: </li></ul><ul><ul><li>MN obtains co-located COA and registers with HA </li></ul></ul><ul><ul><li>Handover: MN keeps COA, new BS answers Reg. Request and updates routers </li></ul></ul><ul><ul><li>MN views BS as foreign agent </li></ul></ul><ul><li>Security provisions: </li></ul><ul><ul><li>MN-FA authentication mandatory </li></ul></ul><ul><ul><li>Challenge/Response Extensions mandatory </li></ul></ul>BS 3 3 Backbone Router Internet BS MN BS MN Crossover Router DHCP Server HA DHCP Mobile IP Mobile IP 1 2 4
  48. 48. HAWAII (Handoff Aware wireless access internet infrastructure) <ul><li>Step 1: On entering the HAWAII domain, MN obtains the colocated COA </li></ul><ul><li>Step 2: MN Registers with HA </li></ul><ul><li>Step 3: When moving to another cell within a foreign domain, MN sends a Registration request to the new base station as to a foreign agent (mixing the concepts of colocated COA and foreign agent COA) </li></ul><ul><li>Step 4: The Base station intercepts the registration request and sends out a Handoff update message. Thus, all routers are reconfigured from the path from old and the new Base Sattions to the so-called cross-over router. </li></ul><ul><li>When routing has been reconfigured successfully, the base station sends a registration reply to the mobile node, again as if it were a foreign agent. </li></ul>
  49. 49. HAWAII: Security <ul><li>Advantages: </li></ul><ul><ul><li>Mutual authentication and C/R extensions mandatory </li></ul></ul><ul><ul><li>Only infrastructure components can influence routing entries </li></ul></ul><ul><li>Potential problems: </li></ul><ul><ul><li>Co-located COA raises DHCP security issues (DHCP has no strong authentication) </li></ul></ul><ul><ul><li>Decentralized security-critical functionality (Mobile IP registration processing during handover) in base stations </li></ul></ul><ul><ul><li>Authentication of HAWAII protocol messages unspecified (potential attackers: stationary nodes in foreign network) </li></ul></ul><ul><ul><li>MN authentication requires PKI or AAA infrastructure </li></ul></ul>
  50. 50. HAWAII: Other issues <ul><li>Advantages: </li></ul><ul><ul><li>Mostly transparent to MNs (MN sends/receives standard Mobile IP messages) </li></ul></ul><ul><ul><li>Explicit support for dynamically assigned home addresses </li></ul></ul><ul><li>Potential problems: </li></ul><ul><ul><li>Mixture of co-located COA and FA concepts may not be supported by some MN implementations </li></ul></ul><ul><ul><li>No private address support possible because of co-located COA </li></ul></ul>
  51. 51. Hierarchical Mobile IPv6 (HMIPv6) <ul><li>Operation: </li></ul><ul><ul><li>Network contains mobility anchor point (MAP) </li></ul></ul><ul><ul><ul><li>mapping of regional COA (RCOA) to link COA (LCOA) </li></ul></ul></ul><ul><ul><li>Upon handover, MN informs MAP only </li></ul></ul><ul><ul><ul><li>gets new LCOA, keeps RCOA </li></ul></ul></ul><ul><ul><li>HA is only contacted if MAP changes </li></ul></ul><ul><li>Security provisions: </li></ul><ul><ul><li>no HMIP-specific security provisions </li></ul></ul><ul><ul><li>binding updates should be authenticated </li></ul></ul>MAP AR MN AR MN HA binding update RCOA LCOA old LCOA new Internet
  52. 52. Hierarchical Mobile IP: Security <ul><li>Advantages: </li></ul><ul><ul><li>Local COAs can be hidden, which provides some location privacy </li></ul></ul><ul><ul><li>Direct routing between CNs sharing the same link is possible (but might be dangerous) </li></ul></ul><ul><li>Potential problems: </li></ul><ul><ul><li>Decentralized security-critical functionality (handover processing) in mobility anchor points </li></ul></ul><ul><ul><li>MNs can (must!) directly influence routing entries via binding updates (authentication necessary) </li></ul></ul>
  53. 53. Hierarchical Mobile IP: Other issues <ul><li>Advantages: </li></ul><ul><ul><li>Handover requires minimum number of overall changes to routing tables </li></ul></ul><ul><ul><li>Integration with firewalls / private address support possible </li></ul></ul><ul><li>Potential problems: </li></ul><ul><ul><li>Not transparent to MNs </li></ul></ul><ul><ul><li>Handover efficiency in wireless mobile scenarios: </li></ul></ul><ul><ul><ul><li>Complex MN operations </li></ul></ul></ul><ul><ul><ul><li>All routing reconfiguration messages sent over wireless link </li></ul></ul></ul>
  54. 54. DHCP: Dynamic Host Configuration Protocol <ul><li>Application </li></ul><ul><ul><li>simplification of installation and maintenance of networked computers </li></ul></ul><ul><ul><li>supplies systems with all necessary information, such as IP address, DNS server address, domain name, subnet mask, default router etc. </li></ul></ul><ul><ul><li>enables automatic integration of systems into an Intranet or the Internet, can be used to acquire a COA for Mobile IP </li></ul></ul><ul><li>Client/Server-Model </li></ul><ul><ul><li>the client sends via a MAC broadcast a request to the DHCP server (might be via a DHCP relay) </li></ul></ul>client relay client server DHCPDISCOVER DHCPDISCOVER
  55. 55. DHCP - protocol mechanisms time server (not selected) client server (selected) initialization collection of replies selection of configuration initialization completed release confirmation of configuration delete context determine the configuration DHCPDISCOVER DHCPOFFER DHCPREQUEST (reject) DHCPACK DHCPRELEASE DHCPDISCOVER DHCPOFFER DHCPREQUEST (options) determine the configuration
  56. 56. DHCP characteristics <ul><li>Server </li></ul><ul><ul><li>several servers can be configured for DHCP, coordination not yet standardized (i.e., manual configuration) </li></ul></ul><ul><li>Renewal of configurations </li></ul><ul><ul><li>IP addresses have to be requested periodically, simplified protocol </li></ul></ul><ul><li>Options </li></ul><ul><ul><li>available for routers, subnet mask, NTP (network time protocol) timeserver, SLP (service location protocol) directory, DNS (domain name system) </li></ul></ul><ul><li>Big security problems! </li></ul><ul><ul><li>no authentication of DHCP information specified </li></ul></ul>

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