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Multicast Based Micro-mobility: Design and Evaluation Ganesha Bhaskara Network Design and Testing Lab Dept. Of EE, USC. Outline Problem Statement Related Work Architecture of M&M Design of M&M Mobility detection Handoff Performance comparison Conclusion Micro-mobility

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multicast based micro mobility design and evaluation

Multicast Based Micro-mobility: Design and Evaluation

Ganesha Bhaskara

Network Design and Testing Lab

Dept. Of EE, USC.

outline
Outline
  • Problem Statement
  • Related Work
  • Architecture of M&M
  • Design of M&M
    • Mobility detection
    • Handoff
  • Performance comparison
  • Conclusion

Ganesha Bhaskara

micro mobility
Micro-mobility

Ganesha Bhaskara

problem statement
Problem Statement
  • Better understanding of the challenges in Micro-mobility
  • Thorough evaluation of Multicast Based Micro-mobility Protocol (M&M) as a promising approach to micro-mobility through simulations, systematic (STRESS) modeling and testing
  • Compare architectural and performance issues of M&M with other micro-mobility protocols

Ganesha Bhaskara

framework of study
Framework of study
  • Architectural Issues
    • Routing mechanism
    • Route update mechanism
    • Mobility detection and handoff mechanisms
  • Performance Issues
    • Handoff delay and jitter
    • Control overhead
    • Robustness against packet loss

Ganesha Bhaskara

approaches to micro mobility
Approaches to micro-mobility
  • Hierarchical tunneling
    • Packets tunneled through tree / hierarchy of foreign agents
    • Packets are decapsulated and re-encapsulated at each hop
    • Example: Hierarchical Mobile IP
  • Mobile specific routing
    • Mobile specific routing table entries are created either by implicit or explicit signaling
    • Example: HAWAII, CIP, M&M

Ganesha Bhaskara

micro mobility protocols
Micro-mobility Protocols
  • Multicast based Micro-mobility Protocol (M&M)
  • Cellular IP (CIP)
  • Handoff Aware Wireless Access Internet Infrastructure (HAWAII)

Ganesha Bhaskara

slide9
M&M
  • MN is assigned a domain wide unicast address – Regional Care of Address (RCoA)
  • All routers map the RCoA to its corresponding and unique Multicast Care of Address (MCoA) using algorithmic mapping
  • As MN moves from one sub-domain to another, it needs to join to its MCoA to receive packets

Ganesha Bhaskara

routing and route update
Routing and Route Update
  • Multicast routing is used to route packets from border router to the mobile node
  • Packets destined to MN tunneled through multicast tree
  • Route update using Join / Prune messages

Ganesha Bhaskara

slide11
M&M

Ganesha Bhaskara

cellular ip routing
Routing Entry Creation

Routers snoop on MN originated data to maintain reverse route

Routing Cache

Routers maintain (IP address of MH,incoming interface)

Route-Update

Maintain and refresh mapping

Route update packet at regular interval if no data

Cellular IP Routing

Ganesha Bhaskara

handoff in cip
Handoff in CIP
  • Hard handoff
    • High Packet loss
    • Simple
  • Semi-soft handoff
    • Reduced packet loss
    • Duplication and reordering of packets
    • MN receives packets from both old and new BS

Ganesha Bhaskara

issues with cip
Issues With CIP
  • Two or more border routers in a domain
    • Packet to and from the MN may take different routes
      • Route establishment and update by snooping on data fails as reverse route is established from the BR through which packets exit rather than enter the domain
    • No mechanism like encapsulation / registration exists to forward to packets to the root of the tree (Rendezvous Point in PIM-SM)

Ganesha Bhaskara

hawaii path setup schemes
HAWAII (path setup schemes)
  • Cross over router – Router nearest to the MN that is in the intersection of two paths
    • Domain root router and the old BS
    • Old BS and the new BS

Ganesha Bhaskara

hawaii path setup schemes16
HAWAII (path setup schemes)
  • Forwarding schemes – packets are forwarded from old BS first and then from the cross over router
    • MSF(Multiple Stream Forwarding)
    • SSF(Single Stream Forwarding)
  • Non-Forwarding schemes
    • UNF(Unicast Non-Forwarding)
      • MN can communicate with multiple BS at a time
    • MNF(Multicast Non-Forwarding)
      • MN cannot communicate with multiple BS at a time

Ganesha Bhaskara

slide17
MSF
  • MN sends update message from new BS to Old BS (Old BS caches undeliverable packets)
  • Old BS updates routing table to forward cached and incoming packets to new BS and sends update message to next hop towards “new” BS
  • Update message diverts packets towards new BS on reaching the cross over router
  • Characteristics
    • General forwarding
    • {IP address  outgoing interface}
    • Packet reordering

Ganesha Bhaskara

slide18
MSF

Ganesha Bhaskara

hawaii msf
HAWAII (MSF)

Ganesha Bhaskara

slide20
MNF
  • MN sends route update to new BS
  • New BS sends route update hop by hop towards old BS
  • Cross over router multicasts data to both old and new BS for a short interval of time
  • Characteristics
    • Packet duplication and reordering

Ganesha Bhaskara

slide21
MNF

Ganesha Bhaskara

related work conclusions
Related Work ….. Conclusions
  • Simulations of M&M, CIP and HAWAII have been done using
    • UDP and TCP traffic
    • Simple wireless model (loss less , zero delay)
    • Simple tree topologies
  • Conclusions
    • Micro-mobility schemes incur significantly less packet loss than Mobile IP
    • Secondary optimizations like MSF, SSF (as in HAWAII) or semi soft handoff (as in CIP) reduce packet loss even further

Ganesha Bhaskara

drawbacks
Drawbacks
  • Lacks systematic study of factors affecting performance parameters
  • Simple wireless models can mask events that can cause protocols to fail
  • Simple tree topologies hides routing inefficiencies

Ganesha Bhaskara

contributions of this study
Contributions of This Study
  • Systematic study of factors affecting performance parameters using
    • Detailed wireless model (802.11)
    • Rich set of topologies (tree and mesh like)
  • Design guidelines for M&M (functional requirements for protocol correctness)
  • Performance evaluation using detailed packet level simulations

Ganesha Bhaskara

design issues in m m
Design Issues in M&M
  • Routing and Route update
    • Choice of multicast protocol
    • Effect of mechanisms of multicast protocol on routing efficiency
  • Mobility detection and Handoff mechanism
    • Algorithms for the same
    • Interaction of the above with mechanisms of multicast protocol

Ganesha Bhaskara

choice of multicast protocol
Choice of Multicast Protocol
  • M&M represents a sparse membership scenario
  • Broadcast and prune protocols not suitable
  • Minimize resource usage
    • Our choice PIM-SM

Ganesha Bhaskara

pim sm
PIM-SM
  • Rendezvous Point (RP)
    • RP bootstrap and election algorithm
    • Placement of RP affects routing efficiency
  • Registration mechanism
    • Any BR can send packet to RP
    • No restriction on entry point of packets into a domain

Ganesha Bhaskara

design of mobility detection and handoff
Design of Mobility Detection and Handoff
  • Design for correctness
    • Protocol should setup routes to deliver packets to the MN
      • Protocol should be able to recover from loss of states / control packets to deliver data
  • Design for performance
    • Once the protocol satisfies the correctness conditions, the protocol can be tweaked for better performance
      • Low handoff delay
      • Low packet loss etc

Ganesha Bhaskara

mobility detection and handoff
Mobility Detection and Handoff
  • Mobility Detection
    • Process by which Mobile Node (MN) finds out that it has moved into the coverage area of another Base Station (BS) and it needs to initiate handoff
  • Handoff
    • Process by which routes are updated such that packets are delivered to the new BS

Ganesha Bhaskara

mobility detection
Mobility Detection

Ganesha Bhaskara

mobility detection32
Mobility Detection
  • BS assisted - using beacons
    • Beacon contains subnet / DR information
    • BS broadcasts beacons periodically
    • MN detects mobility when it receives new beacon
    • MN initiates handoff to the appropriate base station depending on the handoff algorithm
    • Transmission of beacons from adjacent BS should not be synchronized as they will collide in the overlapping region

Ganesha Bhaskara

issues in mobility detection
Issues in Mobility Detection
  • What triggers handoff ?
    • Power of received beacons
      • How many beacons to sample ?
    • If power information is not available
      • Handoff on first new beacon ?
      • Handoff after receiving “n” beacons from new BS ?
  • More handoff algorithms ……. beyond the scope of this study

Ganesha Bhaskara

issues in mobility detection34
Issues in Mobility Detection
  • Why is it important ?
    • Sampling “n” beacons may take hundreds of milliseconds
      • MN could have crossed the overlap region before handoff is initiated
    • But link delays typically of the order of tens of millisecond
  • Faster the mobility detection, the better

Ganesha Bhaskara

handoff
Handoff
  • Approaches to handoff
    • Network assisted handoff
    • MN assisted handoff
  • Network assisted handoff
    • MN sends ICMP packet to DR with its RCOA
    • DR maps the RCOA to MCOA using algorithmic mapping
    • DR sends a join to MCOA group
    • DR decapsulates unicast IP packet from the multicast packet

Ganesha Bhaskara

handoff36
Handoff
  • MN assisted handoff
    • MN needs to be aware that M&M scheme is being used
    • On detecting mobility, the MN sends a join to its multicast group
    • MN needs to decapsulate the unicast IP packet from the multicast packet

Ganesha Bhaskara

handoff in m m
Handoff in M&M
  • With overlap
    • Old and new BS simultaneously receive packets from the multicast tree (Bi-casting)
    • Bi-casting gives rise to
      • Negligible packet loss
      • Packet reordering and duplication
    • Bi-casting : natural extension of multicast
    • Equivalent to MNF in HAWAII and Semi soft handoff in CIP

Ganesha Bhaskara

bi casting during handoff
Bi-casting During Handoff

RP

Ganesha Bhaskara

forwarding schemes and m m
Forwarding Schemes and M&M
  • With no overlap
    • Mechanisms similar to forwarding schemes in HAWAII need to be incorporated
  • BS, on realizing that the packets can’t be delivered to the MN can buffer packets and multicast it to the CAR set
  • Forwarding schemes will require modification to multicast protocol and may not ensure zero packet loss

Ganesha Bhaskara

issues in mobility detection and handoff
Issues in Mobility Detection and Handoff
  • Mobility detection only through beacons
    • How to interpret loss of beacons ?
      • Out of range of BS
      • Lost due to collision
    • How many lost beacons indicates MN is out of range of BS ?
  • Answer to the above questions affects correctness of the protocol and hence performance

Ganesha Bhaskara

stress
STRESS
  • Used to iterate design of M&M especially mechanisms needed for
    • Mobility detection
    • Handoff
  • Used to generate scenarios for simulation
    • Check end cases

Ganesha Bhaskara

correctness conditions
Correctness Conditions
  • As long as a mobile node is in the range of a base station, there must exist an entry corresponding to the multicast group of the mobile node, at the DR on that LAN.
    • The absence of forwarder/designated router on the LAN will lead to packet loss
  • DR on the LAN should have an entry for the multicast group only if the MN is in range of the BS
    • Violation of this condition will lead to wasted bandwidth and increase in the number of multicast states

Ganesha Bhaskara

stress model of m m
STRESS Model of M&M
  • Protocol model
    • FSM of individual components
    • Global FSM
  • Topology model
  • Error model
    • Unacceptable states of the GFSM
    • Occurs due to violation of correctness conditions
  • STRESS is used to design for correctness rather than performance

Ganesha Bhaskara

protocol model
Protocol Model
  • FSM of Mobile Node including
    • Beacon receive timer
    • Solicit timer
  • FSM of DR and beacon transmit timer

Ganesha Bhaskara

topology model
Topology Model

Ganesha Bhaskara

error model
Error Model
  • Black holes: When the mobile node moves from a base station in one sub-domain to another base station in another sub domain, packet loss may occur during handoff. Sustained loss of packets causes black holes

Ganesha Bhaskara

outcome of stress study
Outcome of STRESS Study
  • Functionality requirements
    • MN should be able to recognize loss of beacons and take steps to recover from it
    • MN should ensure that the DR on the LAN knows its presence as long as it is in the range of the BS on that LAN
    • MN should be able to handoff to the best BS
      • Violation of this condition will lead to increased number of handoffs and hence degraded performance

Ganesha Bhaskara

beacon receive timer
Beacon Receive Timer

Ganesha Bhaskara

router solicit timer
Router Solicit Timer

Ganesha Bhaskara

mobile node fsm
Mobile Node FSM

Ganesha Bhaskara

interaction of multicast and m m
Interaction of Multicast and M&M
  • DR broadcasts “host membership query” periodically
  • MN needs to report to router to keep receiving packets
  • Broadcasts may be lost due to collision
    • MN should send report to DR to suppress query timer
    • Failure to do so may lead to packet loss
      • Suppress Query timer pro-actively.

Ganesha Bhaskara

interaction of multicast and m m57
Interaction of Multicast and M&M
  • After deciding to handoff to new BS, MN should suppress the query timer to prevent
    • an expiring query timer from pruning the multicast branch to the old BS and causing packet loss
  • The membership query timeout should be greater than the time it takes for the mobile node to
    • Initiate handoff
    • Receive packets from the new BS

Ganesha Bhaskara

other observations
Other Observations
  • MN will need information from the lower layers to handoff to the best BS
    • On using beacons at IP layer and eager cell switching, handoff suffers due ping-pong effect
    • Lockout timers can cause heavy packet loss in certain mobility scenarios
  • Control messages should be given higher priority

Ganesha Bhaskara

performance
Performance
  • Handoff delay
  • Handoff jitter
  • Packet duplication
  • Packet reordering
  • Routing efficiency

Ganesha Bhaskara

definitions
Definitions
  • Handoff Delay
    • Time between last packet delivered by the old BS and the first packet delivered by the new BS
  • Handoff Jitter
    • Variation in handoff delay (usually caused by dependence of handoff delay on link and queuing delays)
  • Packet Duplication
    • The absolute number of packets duplicated under similar conditions (when traffic is CBR the number of packets duplicated is equivalent to the duration for which duplication occurs)

Ganesha Bhaskara

definitions62
Definitions
  • Packet reordering
    • Depth of reordering
      • Max difference in sequence numbers of consecutive packet
    • Duration of reordering
  • Routing efficiency
    • Ratio of the number of hops between the point at which the packets enter the domain and the destination, to the number of hops on the shortest path

Ganesha Bhaskara

simulation scenario
Simulation Scenario
  • CBR/UDP Traffic
    • Packet interval - 10ms
    • Packet size - 512 bytes
  • Mobility
    • pattern – random
    • Speed – 40m/s
  • Number of Simulation runs - 20
  • Topology –
    • Link delay – 2,5,10ms
    • Link bandwidth – 10Mbps
    • Prune timeout – 1s
  • Wireless
    • MAC - 802.11
    • Overlap – 30m

Ganesha Bhaskara

topology 1
Topology 1

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handoff delay
Handoff Delay

Ganesha Bhaskara

reordering duration
Reordering Duration

Ganesha Bhaskara

topology 2
Topology 2

Ganesha Bhaskara

handoff delay72
Handoff Delay

Ganesha Bhaskara

reordering duration73
Reordering Duration

Ganesha Bhaskara

sub optimal routing in hawaii
Sub-optimal Routing in HAWAII
  • Routing information maintained on a hop by hop basis
  • Equivalent to “previous hop being considered as the source by the next hop”
  • Artifact of definition cross over router
  • Leads to
    • Routing inefficiency
    • Wasted bandwidth
    • Extra forwarding states in routers

Ganesha Bhaskara

performance comparison77
Performance Comparison
  • Handoff Delay
    • M&M and CIP incur negligible handoff delay
    • Handoff delay is masked due to bi-casting
    • HAWAII (MSF) incurs significant handoff delay due to buffer and forward mechanisms and it tends to increase with increase in link delay

Ganesha Bhaskara

performance comparison78
Performance Comparison
  • Handoff jitter
    • Negligible in M&M and CIP (due to bi-casting)
    • HAWAII (MSF) incurs significant jitter due to the dependence of handoff delay on the transmission, propagation and queuing delays on the links between the old and new BS
    • HAWAII (MSF) handoff jitter tends to increase with increase in link delays

Ganesha Bhaskara

performance comparison79
Performance Comparison
  • Packet duplication
    • In M&M and CIP significant number of packets are duplicated
    • The duration of duplication is the same as the duration of bi-casting
    • HAWAII incurs negligible packet duplication

Ganesha Bhaskara

performance comparison80
Performance Comparison
  • Packet reordering
    • Depth of reordering of M&M and CIP is very small as compared to that of HAWAII
    • In bi-casting, depth of reordering tends to increase with increase in the difference between the path length from the fork router to the new and old BS
    • Typically M&M and CIP incur a reordering depth of couple of packets, but reordering occurs as long as bi-casting is done
    • HAWAII (MSF) incurs significant reordering depth (10s of packets), however the duration for which the reordering occurs is small compared to that of M&M and CIP

Ganesha Bhaskara

performance comparison81
Performance Comparison
  • Routing efficiency
    • Assuming root of tree is located at the BR
      • M&M and CIP route packets using the shortest path between the root and the MN
      • Under special circumstances, HAWAII routing can be extremely sub-optimal

Ganesha Bhaskara

comparison between m m and cip
Comparison Between M&M and CIP
  • Routing mechanism is similar
    • Both use shortest path
  • CIP cannot handle situations where there are more than one BR in a domain
    • Route update by snooping fails if packets enter from a BR and exit from a different BR
  • M&M can deal with this situation as it has encapsulation and registration mechanism

Ganesha Bhaskara

conclusions
Conclusions
  • Mobility detection and handoff mechanisms have a profound effect on the performance of the micro-mobility protocol (Eg. M&M, CIP using bi-casting and HAWAII using MSF)
  • Shortest path routing used by M&M and CIP ensures minimum wastage of bandwidth

Ganesha Bhaskara

conclusions84
Conclusions
  • Multicast protocols have been STRESS (designed for correctness) tested and deployed in the Internet
    • Routing mechanism in CIP and HAWAII will have to be tested for correctness before being deployed
  • Multicast protocols have mechanisms to handle LANs in forwarding path (assert mechanism)
  • M&M unlike HAWAII and CIP, has mechanisms to handle situation where packets can enter and leave a domain through more than one BR

Ganesha Bhaskara

conclusions85
Conclusions
  • M&M will require minimum or no modification to existing multicast protocol
    • CIP and HAWAII will require addition of new routing protocols to routers
  • State scaling properties of M&M are similar to that of CIP and HAWAII

Ganesha Bhaskara

conclusions86
Conclusions

M&M is a promising approach to

micro-mobility

Ganesha Bhaskara