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OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS

OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS. Sandro Grech Nokia Networks (Networks Systems Research) Supervisor: Prof. Raimo Kantola. Agenda. The Internet Protocol (IP) The Internet Protocol version 6 (IPv6) Mobile IPv6 Enhancements to Mobile IPv6

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OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS

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  1. OPTIMIZING MOBILITY MANAGEMENT IN FUTURE IPv6 MOBILE NETWORKS Sandro Grech Nokia Networks (Networks Systems Research) Supervisor: Prof. Raimo Kantola

  2. Agenda • 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. Background [4sl](I will go through these few slides quickly!) Foundation [5sl] Problem Identified! [1sl] Core of the thesis (own contribution) [10sl]

  3. 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. 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. 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 <network ID>+<host ID>  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. Mobile IPv6 [2/2] • 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.

  7. 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. LMM: Problem Scope • Possible issues related to the mobility management mechanism in the base Mobile IPv6:

  9. 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. CN HA Local Mobility Agent (LMA) AR AR MN Centralized location information (state) required only for first (few) DL packets towards MN Centralized location information (state) required for all DL packets towards MN

  10. Hierarchical LMMs [2/2] CN - 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 Local Mobility Agent (LMA) Centralized location information (state) required for all DL packets towards MN AR AR Centralized location information (state) required only for first (few) DL packets towards MN MN

  11. 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 asecurity associationwith every localmobility agent which maintains a binding for the MN. • - require theadvertisement of different domainsusing broadcast messages over the bandwidth limited air interface • Proposal: Design something simpler  solve the LMM problem using a different perspective (see next slide)

  12. 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. 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. Flat LMM CN HA Centralized location information (state) required for delivering THE FIRST FEW PACKETS AFTER A HANDOVER DL path SHORTLY AFTER A HANDOVER AR DL path AFTER THE NEW LOCATION INFORMATION HAS PROPAGATED END-TO-END MN

  15. 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. Main Results [1/4] m = 2x106 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. 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. 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. 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. 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. 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. Questions?

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