1. Spring 2000Nitin BahadurDistributed Systems1 Internet Mobility Presented by: Nitin Bahadur

2. Spring 2000Nitin BahadurDistributed Systems2 References Mary Baker, Xinhua Zhao, Stuart Cheshire, Jonathan Stone, Supporting mobility in Mosquitonet, Proceedings of USENIX, Technical Conference, 1996. Stuart Cheshire and Mary Baker, Internet Mobility 4x4, SIGCOMM ‘96. Kevin Lai, Mema R., Diane Tang, Xinhua Zhao, Mary Baker, Experiences with a Mobile Testbed, Proceedings of WWCA ‘98.

3. Spring 2000Nitin BahadurDistributed Systems3 References C. Perkins, IP Mobility Support for IPv4, Internet Draft, draft-ietf-mobileip-rfc2002-bis-01.txt, Jan 2000. C. Perkins, Route optimization in Mobile IP, Internet Draft, deaft-ietf-mobileip-opim-09.txt, Feb 2000. David Maltz, Pravin Bhagwat, MSOCKS: An Architecture for transport layer mobility, IEEE INFOCOM ‘98.

4. Spring 2000Nitin BahadurDistributed Systems4 Outline Motivation and Challenges Some proposed solutions IP Mobility Routing Optimizations Security Issues Recent Extensions Conclusions

5. Spring 2000Nitin BahadurDistributed Systems5 Motivation Ubiquitous connectivity, continuous connectivity. Ability to maintain current conversations/connections during movement. Move from one kind of network to another. Move to networks that do NOT provide support for mobility.

6. Spring 2000Nitin BahadurDistributed Systems6 Challenges Movement causes change in IP address Problems with TCP connections Maintaining transparency Efficient routing to new location of mobile host Security issues

7. Spring 2000Nitin BahadurDistributed Systems7 Some Solutions Use Host specific routes - possible with IPv6. Link Layer solutions –Limited to a single medium –A new solution for every medium –Compatibility issues with other mediums Use extended DNS to register COA with DNS –Information propagation time –Global change in DNS

8. Spring 2000Nitin BahadurDistributed Systems8 Basic Terminology Mobile Host (MH) Correspondent Host (CH) Home Agent (HA) Foreign Agent (FA) Care of Address (COA) Internet CHHA FA MH

9. Spring 2000Nitin BahadurDistributed Systems9 Split TCP Two TCP connections, CH HA MH Transport Layer mechanism Internet TCP - I TCP - II HACH

10. Spring 2000Nitin BahadurDistributed Systems10 Split TCP Two TCP connections instead of one Changed end points HA acks. packets to CH even before MH has received them. Home agent is responsible for final packet delivery Multiple traversal through the TCP protocol stack HA needs to maintain a TCP connection for every TCP connection of all its mobile hosts

11. Spring 2000Nitin BahadurDistributed Systems11 TCP Splicing Two TCP connections, CH HA MH Transport Layer mechanism Acks are sent on TCP-I to CH only when MH sends them on TCP-II Internet HA TCP - I TCP - II CH

12. Spring 2000Nitin BahadurDistributed Systems12 TCP Splicing + The scheme works like 1 TCP connection + Location transparency is maintained - Multiple traversal through the TCP protocol stack - HA still needs to maintain a TCP connection for every TCP connection of all its mobile hosts

13. Spring 2000Nitin BahadurDistributed Systems13 Mobility using Foreign Agent MH obtains COA from FA FA discovery using Agent Advertisement or Agent Solicitation messages MH host registers COA with HA through FA HA intercepts packets for MH HA encapsulates and sends packets to FA FA decapsulates packets and sends it to MH Everything done at IP level……no TCP Same mechanism in the reverse direction This is called Bidirectional tunneling

14. Spring 2000Nitin BahadurDistributed Systems14 Mobility using Foreign Agent FA Internet HACH

15. Spring 2000Nitin BahadurDistributed Systems15 Encapsulation: IP in IP Encapsulation maintains consistency in Source and Destination address fields. Allows MH to receive packets as it moves from network to network. Source = CH Destn = MH Source = HA Destn = MH Source = CH Destn = COA Source = CH Destn = MH HAFA DATA

16. Spring 2000Nitin BahadurDistributed Systems16 Encapsulation Issues IP encapsulation and automatic decapsulation is dangerous How can one verify if the inner packet has a source address if claims to be ! Encapsulation can cause packet fragmentation –TCP breaks data in chunks of 1460 bytes and gives it to IP –Encapsulation will automatically lead to packet fragmentation in such cases. So extra overhead.

17. Spring 2000Nitin BahadurDistributed Systems17 Mobility without Foreign Agent MH obtains a COA using DHCP MH registers COA with HA directly MH performs encapsulation and decapsulation Internet CHHA

18. Spring 2000Nitin BahadurDistributed Systems18 Implementation in MosquitoNet Altered the route lookup function ip_rt_route Mobile Policy Table helps in combination with ip_rt_route is used for making routing decisions

19. Spring 2000Nitin BahadurDistributed Systems19 Home Agent Functionality Maintaining information about MH’s current location Acting as an ARP proxy for MH –ARP…. to get link-layer address for an IP address –Proxy ARP….. done to answer a new ARP request on behalf on MH –Gratuitous ARP…. done to update ARP information of MH in all nodes Forwarding packets to CH and MH

20. Spring 2000Nitin BahadurDistributed Systems20 Movement of MH away from home network Detection by MH –received a different agent advertisement message –stopped receiving agent advertisement messages Disable ARP Register with FA or HA HA performs Gratuitous ARP on behalf of MH

21. Spring 2000Nitin BahadurDistributed Systems21 Movement of MH to home network Re-enable ARP De-register itself with HA HA performs Gratuitous ARP on behalf of MH

22. Spring 2000Nitin BahadurDistributed Systems22 Advantages of using Foreign Agent No need for a temporary COA for every MH If MH leaves foreign network, then Inflight packets can de directed by FA to new location of MH –Less packet loss Less complexity in MH

23. Spring 2000Nitin BahadurDistributed Systems23 Advantages of NOT using Foreign Agent MH can visit networks without a foreign agent FA is not a bottleneck or single point of failure No need for a FA on each network

24. Spring 2000Nitin BahadurDistributed Systems24 Triangular Routing Proposed by Mobile IP working group CH sends packets to HA which forwards it to MH MH sends directly packets to CH HA CH Internet CH MH CH HA COA CH MH

25. Spring 2000Nitin BahadurDistributed Systems25 Problems with Routing Techniques Bidirectional tunneling and Triangular routing –Inefficient, increase in RTT, increase in path length –HA is a bottleneck and a single point of failure –Source address filtering problem with triangular routing

26. Spring 2000Nitin BahadurDistributed Systems26 Source Address Filtering Problem Foreign network might not allow transit traffic Source = MH != foreign network Destination = CH != foreign network => TRANSIT TRAFFIC => DROP IT !

27. Spring 2000Nitin BahadurDistributed Systems27 Source Address Filtering Problem Filtering at CH network Source = MH = CH network But packet has come from a different network …..hmmm….drop it !

28. Spring 2000Nitin BahadurDistributed Systems28 Routing Optimizations - I Similar to triangular routing MH encapsulates packet to avoid source-address filtering problem Better than triangular routing and bidirectional tunneling !

29. Spring 2000Nitin BahadurDistributed Systems29 Routing Optimizations - I HA CH Internet CH MH HA COA CH MH CH COA CH MH CH

30. Spring 2000Nitin BahadurDistributed Systems30 Routing Optimizations - I Direct delivery to CH Valid source address, so no source address problem Location transparency is maintained Will work in all situations CH needs to have decapsulation capability Indirect delivery for CH Will fail if CH border router does not admit packets from current (foreign) network of MH

31. Spring 2000Nitin BahadurDistributed Systems31 Routing Optimizations - II Direct delivery mechanism Both MH and CH encapsulate packets and send directly to each other

32. Spring 2000Nitin BahadurDistributed Systems32 Routing Optimizations - II HA CH Internet CH MH CH COA CH MH CH MH

33. Spring 2000Nitin BahadurDistributed Systems33 Routing Optimizations - II HA CH Internet MH CH COA CH MH CH MH CH

34. Spring 2000Nitin BahadurDistributed Systems34 Routing Optimizations - II Direct delivery between CH and MH Valid source address, so no source address problem CH needs to have en (de)capsulation capability CH needs to be aware of current location of MH Will fail if CH border router does not admit packets from current (foreign) network of MH Validity of encapsulated packet ?

35. Spring 2000Nitin BahadurDistributed Systems35 Routing Optimizations - III Direct delivery mechanism Both MH and CH DO NOT encapsulate packets and send directly to each other using MH and not COA

36. Spring 2000Nitin BahadurDistributed Systems36 Routing Optimizations - III HA Internet CH MH CH

37. Spring 2000Nitin BahadurDistributed Systems37 Routing Optimizations - III HA Internet MH CH

38. Spring 2000Nitin BahadurDistributed Systems38 Routing Optimizations - III Direct delivery between CH and MH CH needs to be aware of current location of MH Invalid source address - security Location transparency ? Applicability When MH and CH are on same link layer segment

39. Spring 2000Nitin BahadurDistributed Systems39 Routing Optimizations - IV Direct delivery mechanism Both MH and CH DO NOT encapsulate packets and send directly to each other using COA and not MH

40. Spring 2000Nitin BahadurDistributed Systems40 Routing Optimizations - IV HA Internet CH COA CH

41. Spring 2000Nitin BahadurDistributed Systems41 Routing Optimizations - IV HA Internet COA CH

42. Spring 2000Nitin BahadurDistributed Systems42 Routing Optimizations - IV Direct delivery between CH and MH No encapsulation overhead CH needs to be aware of current location of MH No Location transparency Packets will be lost if MH changes location

43. Spring 2000Nitin BahadurDistributed Systems43 Routing Optimizations - IV Short lived connections such as HTTP browsing Situations where location transparency is not an issue

44. Spring 2000Nitin BahadurDistributed Systems44 Making CH intelligent Introducing mobile awareness in CH Why - for efficient routing How ? –Binding Warning messages are sent by MH to HA so that HA sends binding update message to CH –Binding update messages are sent by HA to CH whenever HA receives a tunneled packet –MH can also directly send binding update messages to CH MH can specify to HA which CH should be informed of its current location

45. Spring 2000Nitin BahadurDistributed Systems45 Gains using optimizations

46. Spring 2000Nitin BahadurDistributed Systems46 Practical implementation of optimizations Optimizations must not cause break in connection or packet loss Start with the most pessimistic routing method do –Send ICMP echo messages in background using a better method –If that succeeds switch to the better method while (no more methods)

47. Spring 2000Nitin BahadurDistributed Systems47 Security Issues For registrations and communication between HA and MH an authenticator is used Authenticator is optional for communications among HA - {CH, FA} and MH - {CH,FA} Authenticator default algorithm is 128-bit keyed MD5 Since key distribution may be a problem, messages with FA and CH may not be authenticated Replay protection done using timestamps and/or nonces

48. Spring 2000Nitin BahadurDistributed Systems48 Mobile Policy Table Performance

49. Spring 2000Nitin BahadurDistributed Systems49 Mobile Policy Table and Flexibility Supports multiple packet delivery methods simultaneously Adaptively selects the most appropriate method according to characteristics of each traffic flow Makes use of multiple network interfaces simultaneously Controls interface selection of both outgoing and incoming packets for different packet flows MH can register with HA flow specification and corresponding interface binding for that flow

50. Spring 2000Nitin BahadurDistributed Systems50 Why support multiple pkt delivery methods MH pays for extra cost of mobility support only when actually required

51. Spring 2000Nitin BahadurDistributed Systems51 Why support multiple network intefaces Smoother handoffs QoS Link asymmetry Cost and billing Privacy and Security

52. Spring 2000Nitin BahadurDistributed Systems52 Conclusion A schema for supporting ubiquitous and continuous connectivity Support for multiple packet delivery methods Use of multiple packet interfaces simultaneously Dynamic adaptation of routing optimizations MH can specify which CHs should be informed of current COA

53. Spring 2000Nitin BahadurDistributed Systems53 Issues to think about IP encapsulation overhead problem IPSec and IP-in-IP interactions Multicast for Mobile hosts….check out Alex