DMAP-FR: Integrated Mobility and Service Management with Failure Recovery Support for Mobile IPv6 Systems

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DMAP-FR Integrated Mobility and Service
Management withFailure Recovery Support for
Mobile IPv6 Systems

• Greg Bilodeau
• Mike Reed

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What is DMAP-FR?

• An extension of Dynamic Mobility Anchor Points
  (DMAP)
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• DMAP is an extension of Hierarchical Mobile IPv6
  (HMIPv6)
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• HMIPv6 is an extension of Mobile IPv6

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Mobile IPv6

• Mobility in IPv6 Networks.
• MIPv6 is expected to have wide deployment in the
  future for all-IP mobile systems.
• More mobile apps will access multimedia and data
  services over IP

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Mobile IPv6 - Advantages over MIPv4

• Specialized "foreign agent" routers not needed.
• Support for route optimization fundamental part
  of protocol.
• Packets sent to mobile node (MN) sent using IPv6
  routing header rather than IP encapsulation
• Dynamic home agent (HA) discovery mechanism
  returns single reply to the mobile node.

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Mobile IPv6 - Problems

• Does not solve local or hierarchical forms of
  mobility management.
• Effective mobility and service management schemes
  to reduce network traffic needed.
• Fault tolerance for service continuity despite
  network router failures.

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Hierarchical MIPv6

• Allows local mobility handling.
• Designed to reduce the amount of signalling
  traffic between the MN and home agent (HA) and
  correspondent nodes (CNs).
• Utilizes local home agents called mobile anchor
  points (MAPs).

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Hierarchical MIPv6 - MAPs
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Advantages of HMIPv6 and MAPs

• Unlike FA in IPv4, MAPs not required on every
  subnet.
• Limit the amount of IPv6 signalling traffic
  outside the local domain
• Allow MNs to hide their location from CNs.
• MN may chose which MAP (or MAPs) to associate
  with.

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Disadvantages of HMIPv6 and MAPs

• Static domain in terms of number of subnets
  covered.
• Single point of failure.
• While mobility is addressed, service and
  performance management is not considered.

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Dynamic Mobile Anchor Points (DMAP)

• Integrated mobility and service management.
• MN not only determines which MAP to bind to, it
  determines which access router (AR) acts as a
  MAP.
• MAP binding based on both mobility and service
  requirements of the specific MN.

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Dynamic Mobile Anchor Points (DMAP)

• Location handoff MN moves across subnet boundary
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• Service handoff MN moves across DMAP domain
  boundary
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• MAP domain size number of subnets in region
  covered by the MAP

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Dynamic Mobile Anchor Points (DMAP)
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Dynamic Mobile Anchor Points (DMAP) - The Tradeoff

• Choosing a MAP "further" from the MN decreases
  the number of service handoffs, but increases the
  triangular routing overhead and location handoffs
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• Choosing a MAP "closer" to the MN reduces
  the intra-subnet routing, but increases
  the frequency of  service handoffs

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Dynamic Mobile Anchor Points (DMAP) - Finding
Optimal MAP

• MN must be capable of collecting required
  statistical information.
• Goal is the minimization of "communication cost"
  per time unit.

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Dynamic Mobile Anchor Points (DMAP) - Performance
Evaluation
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Dynamic Mobile Anchor Points (DMAP) - Performance
Evaluation

• Calculating MN2DMAP
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• F(Mark(Xs)1) returns the number of hops between
  the current subnet and the DMAP separated
  byMark(Xs)1 subnets.
• The argument of the F(x) function is added by 1
  to satisfy the initial condition that Mark(Xs)
  0 in which the DMAP has just moved into a new
  service area, so at the first subnet crossing
  event, the distance between the DMAP and the
  subnet is one subnet apart

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Dynamic Mobile Anchor Points (DMAP) - Performance
Evaluation

• Calculating NewDMAP
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• As MN must inform HA and all N client nodes of
  new RCoA

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Dynamic Mobile Anchor Points (DMAP) - Performance
Evaluation

• Calculating average communication overhead
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• Includes delays between CN and DMAP, DMAP to AR
  of current subnet, and wireless link between AR
  and MN

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Dynamic Mobile Anchor Points (DMAP) - Performance
Evaluation

• Calculating average location change overhead
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Dynamic Mobile Anchor Points (DMAP) - Performance
Evaluation

• Total communication cost per time unit 
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Dynamic Mobile Anchor Points (DMAP) - Performance
Evaluation
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DMAP-FR

• Dynamic Mobility Anchor Points Fault Recovery
• The addition of fault tolerance to DMAP.

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Failure Recovery Design

• Assume two things
• For each Access Router there is an overlapping
  coverage from other Access Routers since the
  failure of an AR will disconnect all Mobile Nodes
  attached to it
• in the case that a router(not a Mobility Anchor
  Point) fails or a link goes down, it can be
  handled by the recovery mechanism of the routing
  protocol.

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Failure Recovery Design Cont'd

• Based on dynamically selecting an Access Router
  as the Mobile Anchor Point of a Mobile Node. 
• It can recover from two kinds of failures
• The current Access Router can become the Mobile
  Node's DMAP if the DMAP fails
• Access Router failure/recovery can be treated as
  disconnection/reconnection. The failure of DMAP
  can be detected by not receiving the announcement
  message by timeout.

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Failure Recovery Design Cont'd
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Failure Recovery Design Cont'd

• There are Three Cases for Failure Recovery
• Failure of MN's DMAP which is not current AR.
• Failure of MN's DMAP which is current AR.
• Failure of MN's current AR.
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Failure Modes - Failure of MN's DMAP which is not
current AR

• Suppose that the MN is currently under AR2 and
  the current DMAP is AR1 (based on Figure 1). 
• In this case, the Current AR becomes the MN's
  DMAP. AR2 will inform the HA and CN's that it is
  now the DMAP.

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Failure Modes - Failure of MN's DMAP which is
current AR

• The MN is under AR1 which is the current DMAP and
  it fails. In this case, since the wireless
  coverage area of the current AR is overlapping,
  the MN could be under radio range of several
  other subnets.
• The MN will register with a new AR near by which
  will become the new MN's DMAP. AR2 will inform
  the HA and CN's  of the Regional Care of Address
  change.
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•  

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Failure Modes - Failure of MN's current AR

• The MN is under AR3 when AR3 fails and the DMAP
  is on AR1. 
• In this case the MN locates another AR, i.e. AR1,
  or AR2, to replace AR3. The MN will register with
  the new AR through a binding message.

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Performance  Analysis
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Performance  Analysis cont'd

• Using Stochastic Petri Nets because of
• their ability to deal with general time
  distribution for events
• their concise representation of the underlying
  state machine to deal with a large number of
  states
• their expressiveness to reason about a MN's
  behavior as it migrates from one state to another
  in response to events occurring in the system.

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Performance  Analysis cont'd

• The number of tokens accumulated in place Xs,
  that is, Mark(Xs), represents the number of
  subnets crossed by the MN since the MN entered a
  new service area.
• We allow it to accumulate to K (the subnet size
  we're trying to test), at which point we perform
  a service handoff.

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Petri Net Explanation

• The Mobility rate at which location handoffs
  occur is s which is the transition rate assigned
  to Moving.
• When a Mobile Node moves across a subnet area, a
  token is put in place Moves

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Petri Net Explanation cont'd

• After moving into a subnet, the Mobile Node
  obtains a new Care Of Address, and informs the
  DMAP of the Care Of Address change. 
• This is modeled by enabling and firing transition
  MN2DMAP while disabling transition Moving.
• After MN2DMAP is fired, a token in place MOVES
  flows to place Xs, representing that a location
  handoff has been completed and the DMAP has been
  informed of the Care of Address change of the
  Mobile Node.

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Petri Net Explanation cont'd

• If the Number of tokens in place Xs has
  accumulated to K then it means that the Mobile
  Node has just moved into a new service area and a
  service handoff ensues. 
• This is modeled by assigning an enabling function
  that will enable transition MovingDMAP after K
  tokens have been accumulated in place Xs.
• After transition MovingDMAP is fired, all K
  tokens are consumed and place Xs contains no
  tokens, representing the action that the DMAP has
  just moved into a new service area.
• The rate at which transition MovingDMAP fires
  depends on the cost of informing the Home Agent
  and Corresponding Nodes of the DMAP Care of
  Address change. 

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Petri Net Explanation cont'd

• The DMAP alternates between "work" and "Failure"
  states. Initially the DMAP is in the work state. 
• After some time has elapsed, the DMAP goes to the
  failure state. 
• This is modeled by transition failing. 
• Note that if the DMAP is already in place
  Failure, transition failing cannot fire.

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Petri Net Explanation cont'd

• While the DMAP is in failure mode, after time has
  elapsed representing the recovery time, the DMAP
  goes to the work state. 
• The is modeled by the transition recovering.

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Petri Net Explanation cont'd

• For case 1 the DMAP fails but the current AR is
  alive, as illustrated in Figure 1.
• In this case, the current Access Router will
  become DMAP, the new DMAP will inform the Home
  Agent and Corresponding Nodes of the Regional
  Care of Address change.
• This is modeled by firing transition recovering
  with a transition rate reflecting the cost.
• Firing this transition will flush all the tokens
  in place Xs as if a service handoff had happened.
  This is modeled by a variable input arc from
  place Xs to transition recovering.

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Petri Net Explanation cont'd

• For Case2, the DMAP fails and the current Access
  Router happens to be the DMAP, as illustrated in
  Figure 1 where the MN's current AR and DMAP is
  AR1 and AR1 fails.
• In this case, the MN will register with a new AR
  near by
• The new AR  will become the Mobile Node's DMAP
  who will then inform the Home Agent and
  Corresponding nodes of the new Regional Care of
  Address.This event is also modeled by firing
  transition recovering.

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Petri Net Explanation cont'd

• For Case 3, the current AR fails but the DMAP is
  alive, as illustrated in Figure 1.
• In this case, the Mobile Node will register with
  another Access Router nearby. 
• The new Access Router then only needs to inform
  the DMAP of the Care Of Address change. 
• This event can also be modeled by transition
  recovering.
• Note that the rate to transition recovering
  depends on the system state which will be
  characterized later. 

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Characterizing rate of the Recovering transition

• When transition Recovering fires, the Mobile Node
  will contact the DMAP. If the DMAP fails and the
  current Access Router is the MAP, the Mobile Node
  will register with a new Access router near by. 
• The new access router will become the DMAP and
  inform the Home Agent and Corresponding Nodes of
  the RCoA change. 
• If the DMAP fails while the current AR is still
  alive, the current AR will become the DMAP.
• In either case the current Access Router chosen
  becomes the new DMAP and the cost involved is to
  inform the Home Agent and Corresponding nodes. 

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Characterizing rate cont'd

• Since the new DMAP is F(Mark(Xs))  g hops away
  from the failed DMAP, the cost can be
  parameterized as N b  F(Mark(Xs))   a
   F(Mark(Xs))   g  t 
• The rate transition Recovering is the reciprocal
  of this quantity.
•  

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Overall communication costs

• A Mobile Node and its DMAP determine the service
  area dynamically to minimize the overall network
  signaling costs for mobility management, service
  management and fault tolerance related operations
  incurred by the Mobile Node. There are three
  costs considered
• The service cost
• The mobility cost
• The failure recovery cost

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Overall communication cost

• CTotal Cservice  l   Cmobility  s
   Crecovery   df
• CTotal overall cost incurred per time unit
• Cservice average communication cost to service
  a data packet.
• Cmobility average communication cost to service
  a location handoff, including one that can
  trigger a service handoff.
• Crecovery the communication overhead for the
  network to recover from DMAP or AR failures.
•  l  Data packet rate between the Mobile Node and
  Corresponding node.
•  df  DMAP failure rate

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Average communication cost to perform failure
recovery

• Ci,recovery  
• gt  F(Mark(i) 1) t
• if the current AR fails while the DMAP is still
  alive
• gt   at  F(Mark(i) 1) t N(bt  F(Mark(i)
  1) t)
• if the DMAP fails 

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Cost versus K

• DMAP-FR has an optimal service area size Kopt to
  minimize the overall network traffic cost, when
  given a set of parameter values characterizing
  the mobility and service behaviors of the Mobile
  Node and failure behaviors of Access Routers in
  the Mobile IP networks. 

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Kopt versus df

• Kopt increases as  df increases. 
• The reason is that as the failure rate increases,
  the Mobile Node's DMAP likes to stay at a large
  service area to reduce the location handoff cost
  such that a location handoff will most likely
  only involve informing the DMAP of the location
  change without incurring a service handoff to
  migrate the DMAP.

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Cost difference between HMIPv6 and DMAP-FR

• The cost difference between HMIPv6 and DMAP-FR as
  a function of Service-to-Mobility Ratio.
• We observe that the cost difference between
  HMIPv6 and DMAP-FR degenerates,then sharply rises
  as SMR continues to increase.
• We conclude that DMAP-FR performs better than
  HMIPv6, especially when SMR is high.

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Conclusion

• DMAP-FR - efficient mobility and service
  management with failure recovery supporting
  Mobile IPv6 environments. 
• Devised a computational procedure to compute the
  optimal service area size that would minimize the
  overall network traffic cost.
• Compare our scheme with HMIPv6 
• Performance gain due to a proper selection of the
  best service area dynamically.

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References

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• Questions?