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Mobility in the Internet

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  1. TML,TKK, Helsinki, Finland Chittaranjan Hota, PhD Department of Computer Science and Information Systems Birla Institute of Technology & Science, Pilani Rajasthan, 333031, INDIA E-mail: Mobility in the Internet

  2. Military Response Mobile Computing: Why? Nokia E61 Home Security Gambling Home medical care E-learning Sports Streaming Movies

  3. Markets for IP Mobility [Source:Cisco]

  4. Mobile Wireless Devices Laptop Smartphone Media Player Palmtop Digital Camera Mobile Router Personal Digital Assistant Notebook Pager Gaming Console

  5. Is it Portable Networking? • Portable Networking requires connection to same ISP • Technologies • Bluetooth • Short range, low cost radio links between mobile devices • Wireless Ethernet (802.11) • MAC Layer technology • Cellular • Cellular Digital Packet Data, 3G

  6. Outline • Will Address • Internet architecture and Motivation for Mobile IP • Mobile IPv4, HMIP, HAWAII, Cellular IP, MIPv6, i3, TCP Indirect, SIP, NEtworkMObility, HMIPv6 etc. • Low level protocol details including message formats and headers • Comparison on the basis of location updates, handoff latency, and signaling overhead • Won’t cover • IP Routing (Link state, Distance vector, OSPF, BGP, RIP etc.) • Wireless Networks • IPv4, and IPv6 Protocol details • Security and QoS issues related to Mobile IP

  7. Internet Architecture

  8. Tier 3 ISP local ISP local ISP local ISP local ISP local ISP local ISP local ISP NAP Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISP Internet: Network of Networks Tier 1 ISP Tier 1 ISP Tier 1 ISP

  9. How do you contact a mobile friend? • search all phone books? • call her parents? • expect her to let you know where she is? I wonder where Alice moved to? Consider a friend frequently changing addresses, how do you find her?

  10. Motivation: Mobile IP 223.1.1.* Internet IP Address: Hierarchical (Net ID, Host ID) Mobile IP: Locator, and Identifier 122.1.3.*

  11. No mobility High mobility Moderate mobility mobile user, passing through multiple access point while maintaining ongoing connections (like cell phone) mobile user, connecting/ disconnecting from network using DHCP. mobile wireless user, using same access point Mobility Classification Protocols

  12. Mobility Global Macro Micro MIP (1996) Hierarchical MIP (1996) Cellular IP (1998) Hawaii (1999) Dynamic Mobility Agent (2000) TeleMIP (2000) Time (evolutionary path) MIPv6 (2001) TMIP (2001) HMIPv6 (2001) Intra-subnet Inter-domain Intra-domain Mobility Classification Protocols

  13. Mobility: Approaches • Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. • routing tables indicate where each mobile is located • no changes to end-systems • Let end-systems handle it: • indirect routing: communication from correspondent to mobile node goes through the home agent • direct routing: correspondent gets foreign address of mobile, sends directly to mobile

  14. Mobility: approaches • Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. • routing tables indicate where each mobile located • no changes to end-systems • let end-systems handle it: • indirect routing: communication from correspondent to mobile goes through home agent • direct routing: correspondent gets foreign address of mobile, sends directly to mobile not scalable to millions of mobiles

  15. Mobile IP (MIPv4) Foreign Network B R Home network A Foreign Agent R Internet Home Agent Network C R Correspondent Node C

  16. Type=10 | code | checksum reserved Step1:Agent Discovery M, G bit: Minimal, Generic encapsulation H,F bits: home or foreign agent R bit: registration required B bit: Busy Agent Advertisement V bit: Van Jacob Header compression Agent Solicitation With TTL=1

  17. Step 2: Registration Minimal Encapsulation format Reg. request format Reg. reply format

  18.  Step 2: Registration Foreign Network B R Home Network A Mobile Node R Foreign Agent Internet Home Agent Network C R • Foreign agent sends Binding Update • Home Agent replies with Binding Acknowledgement Correspondent Node C

  19. Mobility binding table at Home Agent Home address Care-of address Lifetime (sec) 150 … … … Step 2: Registration (Example) Visitor List at Foreign Agent

  20. visited network: 79.129.13/24 home agent foreign agent ICMP agent adv. HA: COA: Mobile node MA: COA: 79.129.1 3.2 …. registration req. registration req. COA: HA: COA: MA: HA: Lifetime: 9999 MA: identification:714 Lifetime: 9999 …. identification: 714 encapsulation format …. registration reply registration reply time HA: MA: HA: Lifetime: 4999 MA: 6 Identification: 714 Lifetime: 4999 encapsulation format Identification: 714 …. …. Step 2: Registration (Example)

  21. foreign-agent-to-mobile packet packet sent by home agent to foreign agent: a packet within a packet (Tunnel) dest: dest: dest: mobile replies directly to correspondent packet sent by correspondent dest: Step 3: Indirect Routing via Tunneling • Home agent broadcasts ARP request which causes all nodes in the Home network to update their ARP caches to map the mobile nodes IP address to the home agents link level address. Permanent address: Care-of address:

  22. Route Optimization Messages Binding Acknowledgement Binding update Binding warning Binding request

  23. visited network home network Internet Binding update First Packet to mobile host 4 2 1 3 CN Route Optimization (Operation 1: Binding Cache)

  24. visited network Subsequent packets to the mobile host home network Internet CN 4 5 3 Route Optimization (Operation 1: Binding Cache)

  25. Route Optimization (Operation 2: Smooth handoff)

  26. 2 1 5 4 3 Route Optimization (Operation 2: Smooth handoff) foreign network visited at session start Binding Warning home network Binding Update FA Internet Binding Update New Foreign network New FA CN

  27. Route Optimization (Operation 3: Establishing Registration keys) • If the FA and Mobile node share a security association, the FA can choose the new registration key • If the HA and the FA share a security association, the HA can choose the new registration key • If the FA has a Public key, the HA can supply a new registration key • If the Mobile node includes its’ Public key in the registration request, the FA can choose the new registration key • The Mobile node and its’ FA can execute a D-H key exchange protocol to get a new registration key

  28. 5 1 2 4 3 Route Optimization (Operation 4: Special Tunnels) No visitor list or Binding cache Special Tunnel same home network FA1 rebooted [(FA1, MH), (CN, MH),…] Internet Binding Update [(CN,FA1), (CN, MH),…] New Foreign network FA2 CN

  29. Ingress Filtering Correspondent, home agent on same network. Packet from mobile host is deemed "topologically incorrect" correspondent host home agent • Routers which see packets coming from a direction from which they would • not have routed the source address are dropped (external domain)

  30. Reverse Tunneling CN Internet MH cannot make a tunnel directly to CN HA COA Home Network FA MH Pro: Firewall and Ingress Filtering problems removed Con: Lengthy Routing Path (double triangular), increase in congestion

  31. Other Issues in Mobile IP • How does a Mobile node acquire a care-of-address in the foreign network? • By DHCP, Router advertisements, Manually • If Home agent does not reply to registration request • Send the request to broadcast address (redundancy) • Reducing registration frequency (in high mobility scenario) • FAs into a multicast group, into an anycast group, Hierarchy • Source Routing Option to avoid Tunneling and triangular routing • Not feasible as the load on intermediate routers will be more • Security(denial of service attack by bogus registration request) • Authentication using MD5 hashes • Replay attacks are prevented by (timestamp or nonce)

  32. Problems with MIPv4 • Authentication with FA is difficult as it belongs to another organization • Guaranteeing QoS to a flow of packets is difficult because of triangulation and tunneling. • Triangular routing and frequent handoffs cause significant end-to-end delay (Micro-mobility helps a bit) • High signaling load on HA if mobile node moves frequently. • To support Global mobility, all routers should have FA and HA functionality (solved with a reduced scope in Macro-mobility). • For some applications, it may be important to track the location of mobile nodes : causes huge power and signaling load. • Paging (the maintenance of information when the node is idle) is not supported by MIP. (Paging is a procedure that allows a wireless system to search for an idle mobile host when there is a message destined to it, such that the mobile user does not need to register its precise location to the system whenever it moves) • User perceptions of Internet reliability. • If FQDN of the Mobile node has many IP addresses, which one to choose?

  33. Hierarchical Mobile IP (HMIP) MH@FA1 Localizing Registrations HA Internet MH@FA2 MH@FA3 FA1 MH@FA4 MH@FA6 MH@FA5 FA3 FA2 Lineage <FA4, FA2, FA1> FA6 FA5 MH@VL MH@VL <FA6, FA3, FA1> FA4 <FA5 FA2, FA1> Common ancestor = FA1 (nearest) Common ancestor = FA2 (nearest)

  34. New AP answers reg. req AP Updates routers CN DHCP Server Router at Level1 IP Routing AP Internet Foreign domain root router AP Router at Level1 3 4 5 2 MH IP tunnel Home domain root router Co-located COA 1 Registering with HA Handoff-Aware Wireless Access Internet Infrastructure (HAWAII) • User mobility is restricted to administrative domain • MH implements MIP, but host based routes inside the domain • In the foreign domain, MH retains a single co-located COA

  35. Cellular IP (CIP) • Two handoffs (hard and semisoft), and paging is supported. • Semisoft handoff uses layer 2 signal strength (of AP) to earlier trigger layer 3 procedures hence minimizing packet loss. • Regular data packets transmitted by MHs maintain reverse path routes. • Each CIP node maintains routing cache and paging cache. CN CIP Routing IP Routing MH Internet CIP Gateway CIP Nodes IP tunnel CIP Domain HA • Initial registration at CIP gateway requires authentication of MH (MH key :MD5(Net Key, IP Addr)

  36. Mobile IPv6 (MIPv6) • Differences between MIPv4 and MIPv6 • No FA is needed (no infrastructure change) • Address auto-configuration helps in acquiring COA • MH uses COA as the source address in foreign link, so no ingress filtering • Option headers, and neighbor discovery of IPv6 protocol are used to perform mobility functions • 128 bit IP addresses help deployment of mobile IP in large environments • Route optimization is supported by header options

  37. Extension Headers CN to MN MN to CN Upper Layer headers Data MH Mobility Header MH Type in Mobility Header: Binding Update, Binding Ack, Binding Err, Binding refresh MN, HA, and CN for Binding

  38. Binding Update and Binding Acknowledgement 8 bits 8 bits 8 bits 8 bits Payload Proto Header Length MH Type Reserved Sequence No Checksum BU Reserved Lifetime A H L K Security association required for every move Home Agent Link-local address is same as that in home address ACK Expected 8 bits 8 bits 8 bits 8 bits Next header Header Length MH Type Reserved Checksum BA Status K Sequence No Lifetime

  39. MIPv6 Operation: Mobile on Home network Conventional Routing is used

  40. MIPv6 Operation: Mobile on a Foreign network 3 2 Foreign Network 4 Stateless address Auto configuration 1 Bidirectional tunnel Duplicate address detection, Proxy neighbor discovery, and Binding cache update (Acquiring COA) 5 Update Binding Update List

  41. Mobile IPv6 Route Optimization Mobile Node • Binding Update without H, K, and L bits being set • Packet Link B Home Link Link A Router Internet (2) Link C Router (1) Router Home Agent Correspondent Node If A option is set in BU, then CN sends a BA, after which MN updates binding update list. With every packet sent, MN sends Home address in destination extension header and CN sends Home address in Routing header 2 extension header for keeping upper layers transparent from mobility.

  42. MIPv6: Dynamic Home Agent Discovery Home Agents List Preference Value Home Agent 2 6 Home Agent 1 2 1 1 2 2 Mobile Node Home Agents List Preference Value Home Agent 2 6 Home Agent 1 2 Dynamic Home Agent Address Discovery request to anycast address 1 DHAAD reply with addresses of home agents with their preferences 2

  43. MIPv6: Mobile Node Returning Home Requirement: MN should send a BU to HA with lifetime=0 and COA=Home address of mobile Problem: HA will reject MN’s home address (Duplicate address detection) as it is still defending the mobile node MN HA Neighbor solicitation Neighbor advertisement SOLUTION Binding Update Neighbor solicitation Neighbor advertisement Binding Acknowledgement

  44. Internet Indirection Infrastructure (i3) • An Overlay infrastructure. • Every packet is associated with an identifier. • Receiver receives using identifier A Trigger Movement with a different address (Natural Support for Mobility) [Source:]

  45. i3: How it Works? (A Receiver R inserts a trigger into i3) CHORD ensures O (log N ) no. of intermediate hops to reach at the destination (A Sender S sends a packet with same identifier 37, that is delivered to R) []

  46. TCP Solutions to Mobility • When MN initiates a connection, it tells the CN it’s new IP address through SYN • CN uses DNS lookup to locate a MN • TCP Migrate option is used to migrate to a new connection • (s_ip, s_port, d_ip, d_port) to (s_ip, s_port, d_ip’,d_port’) CN CN MN MN after movement (Migrate SYN, Migrate SYN/ACK, ACK)

  47. TCP Early Approach (Segmented TCP) Wired Internet FA Standard TCP Mobile TCP Mobile Host Fixed Host

  48. Indirect TCP (I-TCP) MH Socket MSR2 MH Socket MSR2 FH Socket Wireless TCP Mobile Support Router Handoff: Socket Migration and state transfer MSR2 Internet MSR1 Standard TCP Standard TCP Wireless TCP FH Socket MSR1 FH Socket MH Socket MSR1 MH Socket Fixed Host WTCP (Probe and bandwidth estimation) for blackouts Multicasting for fast handoffs Secure DNSand SYNforend-to-end Mobile Host

  49. Mobility using Session Initiation Protocol (SIP) • A Signaling Protocol • Originally used for negotiating media sessions between end systems • Media may go through different networks • Other uses: Conferencing, VoIP, Instant Messaging etc. • Elements (SIP user agent, Servers, and Gateways) • Addressing (URLs) e.g. name@domain and supports both Internet and PSTN address

  50. SIP Session Setup Example SIP User Agent Client SIP User Agent Server INVITE 200 OK ACK Media Stream BYE 200 OK