1. 1 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS Sandro Grech Nokia Networks (Networks Systems Research) Supervisor: Prof. Raimo Kantola

2. 2 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Agenda Background [4sl] (I will go through these few slides quickly!) Foundation [5sl] Core of the thesis (own contribution) [10sl] Problem Identified! [1sl] The Internet Protocol (IP) The Internet Protocol version 6 (IPv6) Mobile IPv6 Enhancements to Mobile IPv6 Localized Mobility Management (LMM) Hierarchical LMM models Problem Statement A Non-hierarchical (flat) LMM model Evaluation Main Results Own Contribution Summary, Main Conclusions, Open Issues, and Further Work.

3. 3 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Background - The Internet Protocol (IP) IP is a connectionless network layer protocol (each datagram is routed independently on a hop-by-hop basis). IP is used to interconnect virtually any link-layer technology. IP is designed over an end-to-end paradigm: intelligence is in the end systems, not in the network!  The main intelligence in the network are the routing protocols which maintain routing tables up-to-date (used to determine the next hop towards a datagram's destination). IP is stateless -> end-to-end connections do not rely on any state being kept in some entity inside the network. As soon as some per-connection states are introduced in some network entity, then the connection will share the fate of that network entity.

4. 4 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Background - The Internet Protocol version 6 (IPv6) Main driver: exhaustion of IPv4 addresses (different estimates regarding when this will happen)  IPv6 extends the address space from 32 bits to 128 bits (we all heard this story...). IPv6 uses a streamlined header format  base header + extension headers for optional fields  faster processing inside routers. IPv6 optimizes hierarchical addressing  address hierarchy is based on the common occurrence of multiple levels of ISPs  smaller routing tables on backbone routers (currently > 100k entries). IPv6 supports stateful (DHCP) and stateless (no server required) address autoconfiguration. IPv6 requires the support of standards based security (IPSec). IPv6 flow-lables allow the provision of QoS for different traffic flows. IPv6 uses a new Neighbor Discovery mechanism (which replaces ARP).

5. 5 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Mobile IPv6 [1/2] Benefits of mobility at the IP layer - demand for data traffic is increasing and much of this data is natively IP data. - wide range of access technologies (wireless and wired)  Mobility at the IP layer allows for a unified mobility management mechanism across these technologies PROBLEM: IP addresses have a dual functionality: - IP addresses provide a means of addressing a host (interface). IP addresses are hierarchical +  allows route aggregation (leading to smaller routing tables)  if a Mobile Node (MN) becomes attached to a new router, then it must change its IP address - IP addresses are used as a means of identification at the transport layer (e.g. TCP uses IP address + port number to identify a session)  IP addresses should not change

6. 6 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Mobile IPv6 provides a solution to the identified problem by: - assigning two IP addresses to a mobile node: + a static Home Address (HoA)  used for identifying a MN + a dynamic Care-of Address (CoA)  used to maintain routability towards the MN's most recent point of attachment to the network - defining a new network entity (Home Agent, HA) which homes the HoA, and maintains a mapping (binding cache) between the HoA and CoA of MNs which are outside of the Home Network - these mappings are also maintained by Correspondent Nodes (CNs) which have an active session with a MN and are maintained by using Binding Updates (BUs) whenever there is a change in CoA. - packets from a new CN are addressed to the MN's HoA  routed to the MN's Home Network  intercepted by the HA  forwarded (tunneled) to the MN's CoA (based on the mapping inside the HA's binding cache). After this the CN will receive the MN's CoA and further packets are routed directly using the MN's CoA. Mobile IPv6 [2/2]

7. 7 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Enhancements to Mobile IPv6 Target: Provide scalable, seamless ( = lossless + fast) handovers at the IP layer, particularly for real-time traffic.  the base Mobile IPv6 is only providing a foundation for this. Enhancements to the base Mobile IPv6 mechanisms: - Fast Handovers for Mobile IPv6 (FH)  speeds IP handovers by allowing a MN to start the process of obtaining a new CoA prior to disconnecting from the old Access Router - Context Transfers (CT)  Access Routers (AR) need to maintain several per-MN contexts which require several RTTs over the air to be set up. CT allows these contexts to be transferred between ARs instead of being re-established after each IP layer handover. - IP Paging  allows a MN to go dormant (saves battery consumption) without loosing reachability - Localized Mobility Management (LMM) mechanisms  see next slide

8. 8 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 LMM: Problem Scope Possible issues related to the mobility management mechanism in the base Mobile IPv6:

9. 9 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Hierarchical LMMs [1/2] Introduce additional level/s of hierarchy by introducing nodes topologically closer to the MN which handle mobility within a specified region, locally. - Hierarchical Mobile IPv6 proposes to have one node (or local mobility agent, similar to the HA) somewhere between the MN and HA which delimits a region inside which this mobility agent will act as a signaling endpoint for the MN's MIPv6 signaling. Signaling towards the HA/CNs only needs to take place when the MN transits to a region delimited by a different local mobility agent. HA CN MN AR Local Mobility Agent (LMA) Centralized location information (state) required for all DL packets towards MN Centralized location information (state) required only for first (few) DL packets towards MN

10. 10 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Hierarchical LMMs [2/2] - Mobile IPv6 Regional Registrations extends this by allowing all the routers below the root local mobility agents to be capable of acting as mobility signaling endpoints. In the optimal case the signaling would thus only need to propagate up to the crossover router (lowest common router between old and new path to MN). HA CN AR Local Mobility Agent (LMA) MN Centralized location information (state) required for all DL packets towards MN Centralized location information (state) required only for first (few) DL packets towards MN

11. 11 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Problem Statement Some problems with the hierarchical models: - downlink packets are routed using the centralized states inside local mobility agents instead of using standard routing table entries  fault tolerance of IP is compromised! - the downlink traffic needs to traverse a pre-defined path through the local mobility agents containing the location information of the MN  this becomes particularly unnatural for two communicating MNs residing under the same local mobility agent, in which case the traffic does not follow its natural shortest path. - the MN should maintain a security association with every local mobility agent which maintains a binding for the MN. - require the advertisement of different domains using broadcast messages over the bandwidth limited air interface Proposal: Design something simpler  solve the LMM problem using a different perspective (see next slide)

12. 12 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Proposal - Flat LMM Aim: Study the problems identified in slide 8 and formulate an alternative approach which does not introduce the drawbacks identified in slide 10. Outcome: Non-hierarchical (flat) LMM Outline of the proposed mechanism: - MIPv6 e-2-e signaling latencies are tackled using temporary forwarding tunnels between the MN's old and new Access Routers  short lifetime - just enough to allow the new location information to reach the peer nodes (typically < 1 s) - Signaling overhead and processing overhead are tackled by introducing a constant (MIN_MIP_BU_INTERVAL) which defines the minimum interval between two BUs sent at the MIPv6 layer  BUs exceeding this interval are sent as usual  other BUs are sent to an Anchor Access Router which maintains a mapping between the MN's old and new CoAs. This allows 'erratic' MN transitions to be handled at the network edge and only 'stable' transitions are notified e-2-e.

13. 13 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Flat LMM - comparison Flat-LMM is not based on static local mobility areas but is instead tightly coupled with the dynamic behavior of MNs. If a MN is handing over at a slow rate, then no action is taken to limit the frequency of MIPv6 signaling (note that erratic handovers are typically very local in time, e.g. turning around corners, etc...) No states need to be kept in centralized states. All routers (except for the Access Routers) are standard IP routers  robustness of IP is retained. Forwarding states are only maintained at the Access Routers (fully distributed) and are only required for a very short interval after a handover. At all other times routing is based on standard routing tables. The forwarding tunnels can be based on mechanisms defined by the Fast Handovers protocol  additional functionality is minimal.

14. 14 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Flat LMM HA CN AR MN Centralized location information (state) required for delivering THE FIRST FEW PACKETS AFTER A HANDOVER DL path SHORTLY AFTER A HANDOVER DL path AFTER THE NEW LOCATION INFORMATION HAS PROPAGATED END-TO- END

15. 15 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Evaluation Aim: To evaluate the feasibility of the flat-LMM proposal Tools: Analytical models (assisted by some basic simulations (NS-2) where applicable) + some measurements from prototypes when available. Criteria: 1) quantify the network signaling overhead caused by MIPv6 signaling 2) determine the processing overhead caused by MIPv6 signaling 1+2)  what action should be taken to reduce MIPv6 signaling frequency (at the MIPv6 layer)? 3) what are the tunneling requirements introduced by the flat-LMM mechanism?

16. 16 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Main Results [1/4] m = 2x10 6 subscribers Fluid flow model: r is the rate of flow of MNs out of a region  is the density of MNs inside the region of interest V is the average velocity of MNs inside that region L is the length of the region's boundary. Result: ~22,000 BUs/s at the HA  ~18Mbits/s UL for BUs and ~18Mbits/s DL for BACKs.

17. 17 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Main Results [2/4] On an INTEL Pentium MMX 200 Mhz the processing cost of a Mobile IPv6 BU has been measured to be ~ 0.3 ms  processing capacity of c.a. 3k BUs/s  a 2Ghz processor should be capable of processing the ~20k BUs/s calculated in the previous slide. Conclusions: - Processing and signaling overhead are not appear to be as drastic as expected. - Reducing the 'erratic' handovers (as is done by the flat-LMM) should be enough to maintain processing and signaling overhead at the Mobile IP layer at a sustainable level

18. 18 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Main Results [3/4] Individual mobility modeled using the 'random waypoint algorithm' provided by NS-2. Assumptions: - square cells (for simplicity) - 50 MNs were simulated (due to long simulation time and large log files) Results (summarized):

19. 19 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Main Results [4/4] Tunneling requirements  Once again using the fluid flow model, and the results shown in the previous slide the following estimates was obtained: - the amount of simultaneous forwarding tunnels in the flat-LMM when compared to the Fast Handovers mechanism is increased by a factor of ~3.2 if MIN_MIP_BU_INTERVAL = 5 seconds or ~1.7 for MIN_MIP_BU_INTERVAL = 3 seconds. - the amount of simultaneous forwarding tunnels for an Access Router serving ca. 2,000 MNs will be ~250 if MIN_MIP_BU_INTERVAL = 5 seconds or ~130 for MIN_MIP_BU_INTERVAL = 3 seconds.

20. 20 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 My Contribution Main contributions: - Developed the non-hierarchical Localized Mobility Management model including a detailed description of potential implementation options based on different underlying protocol functionalities. - Evaluation of the proposed non-hierarchical Localized Mobility Management model using analytical models (mainly).

21. 21 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Summary, Main Conclusions, Open issues and Further Work Summary/Main Conclusions: - Mobile IPv6 may have an important role in future mobile networks. - Mobile IPv6 does not solve everything. Enhancements are required. - Hierarchical LMM models exhibit some drawbacks particularly w.r.t. robustness. - Non hierarchical LMM proposed. The main concern is the introduction of "horizontal" traffic at the edge of the network. Open issues: - Study is based on draft-15 of Mobile IPv6. Draft-16 is due to be out soon. Major changes are expected in order to overcome the security concerns associated with draft-15. Further Work: - More rigorous evaluation study based on second order models and refined assumptions. - Investigate the impact of future revisions of the Mobile IPv6 draft (soon-to-be RFC?)

22. 22 SANDRO GRECH - OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS :: grech_120202.ppt :: 12.02.2002 Questions?