A proxy-based integrated cache consistency and mobility management scheme for client-server

applications in Mobile IP systems- Weiping He, Ing-Ray Chen

Group MembersSuresh Giridharpuram

Lakshman KrishnamurthyManoj Maskara

CS 5214 Spring 2010

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Topics to be covered• Motivation• Role of Proxy• Contribution of the paper• System Infrastructure• Service Handoff process• SPN Model• Parameterization & Transition Rates• Performance Metric and Cost Functions• Performance Evaluation & Comparisons• Summary

Suresh

Manoj

Lakshman

Suresh

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Motivation

• Mobile host may disconnect and reconnect• Mobile host query dynamic data such as

stock prices, weather report, etc.• Sending query to server and receiving

reply is expensive• MH can cache data objects to improve

response time• MH must ensure cache data are up-to-

date

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Motivation …cont.

• Solution is Integrated Cache and Mobility Management using proxy – MH uses invalidation reports to determine the

validity of the cache– If the cache is invalid query request is sent

uplink to the server – Per user proxy to buffer invalidation

messages if MH is disconnected– Proxy handles both service and mobility

management

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Role of Proxy• Serves as MH’s gateway foreign agent (GFA)• Proxy migrates with MH when MH crosses

regional area• Allocating extended cache space to store

service context information including cache validation report for each MH

Goal:

Identify optimal regional service area size to minimize network traffic

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Contributions of the paper(1) Integrated mobility and cache management to minimize

the overall network traffic cost for supporting mobile client-server query applications in future MIPv6 systems

(2) Identifying the optimal proxy setting including the region area size that will minimize the overall network traffic generated due to mobility and cache consistency management

(3) Benefit of integrated mobility and cache consistency management in MIPv6 compared with basic MIPv6, no-proxy and/or no-caching schemes, as well as a decoupled scheme under which mobility management and cache management are separate but optimally run

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System Infrastructure

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Service handoff

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Algorithm

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Algorithm…..cont.

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SPN Model

Objective is to find optimal K

σ

ωwωs

Rate depends on the # of subnets separating MH & the proxy

Rate depends on the cost of informing HA & CN and the cost of transferring Proxycache to new proxy location

Rate depends on the cost of informing HA & CN and the cost of transferring service context of Proxycache to new proxy location

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SPN Model ….cont.

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Parameterization

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Transition Rates

MH2Proxy Transition Rate:

MovingProxy Transition Rate:

InquiringProxy Transition Rate:

# of hops between current subnet and proxy

# hops between 2 subnets times # packets of service context info

Cost to communicate HA and N CNs

Delay for contacting the proxy

Inform HA and CNs of proxy’s CoA change

Moving proxy to current AR

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Performance Metric and cost function…1

Ctotal = λe x Cquery + σe x Cmobility + μe x Cinvalidation

σe = σ x Pwake μe = μ1+ μ2 + μ3 +…….+ μNdata

Pwake =ωs / (ωs + ωw)

λe = λq x Pwake

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Performance Metric and cost function…2

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Performance Evaluation…1

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Performance Evaluation …2

• This scheme was compared with three baseline schemes:1) A no-proxy no-caching (NPNC) scheme, 2) A proxy no-caching (PNC) scheme, and 3) A no-proxy caching (NPC) management scheme

• We also compare our scheme with a decoupled scheme that optimally but separately manages mobility and service activities.

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Performance Evaluation …3• The NPNC scheme essentially is the basic MIPv6

scheme without using a proxy for either mobility or cache management.

• The PNC scheme is the proxy-based regional registration scheme using a proxy for mobility management. – In these two schemes, the MH does not cache data objects.

• The NPC scheme uses basic MIPv6 for mobility management and cached data objects maintained by the MH for cache management, but there is no proxy used

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Performance Evaluation …4

Optimal K to minimize network traffic

Kopt decreases slowly as λq,i increases. When λq,i increases, the query cost increases and the MH prefers a small service area size to reduce the query cost.

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Performance Evaluation …5

Kopt increases as σ increases. when the mobility rate is high, the proxy likes to stay at a large service area to reduce the location handoff cost

Kopt decreases as μi increases. As μi increases, the data in the local cache are more likely to be out-of-date. MH sends more queries and more invalidation reports will be sent from the CN to the MH through the proxy. The MH will stay close to the proxy to reduce the triangular CN-proxy-MH communication cost.

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Performance Evaluation …6

Kopt decreases as the MH sleeps longer. The data in MH's local cache are more likely to be out-of-date when the MH sleeps longer. MH will stay close to the proxy to reduce the triangular CN-proxy-MH communication cost

Kopt decreases as the number of cached data objects increases. As the number of cached data objects increases, more invalidation reports will be sent from the CN to the MH. To reduce the triangular CN-proxy-MH cost the MH tends to stay closer to the proxy.

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Performance Comparison …1

Caching-based schemes (NPC and PICMM) achieve much better performance vs. non-caching-based schemes (NPNC and PNC), especially when λq,i is large.

Between the two caching-based schemes, PICMM scheme performs consistently better than NPC due to the use of a proxy for integrated cache and mobility management for extra cost saving.

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Performance Comparison …2

PICMM scheme outperforms all other schemes. PICMM uses a proxy to serve as a GFA to reduce thecost of location handoffs and the benefit is especially pronounced when the mobility rate of the MH is high.

.PICMM achieves much better performance especially when Ndata is large because caching saves much of the uplink cost for query processing.

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Performance Comparison …3

PICMM consistently performs better than NPC. However, when the data update rate is very high, most cached data objects are invalid, so queries will need to be routed to theCN. In this case, there exists a cross-over point in the update rate beyond which PICMM would perform worse than a non-caching scheme because of the CN-proxy-MH triangular cost.

PICMM incurs a higher query cost than non-caching schemes. There is a cross-over point in the sleep ratio beyond which PICMM would perform worse than a non-caching scheme.

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Proxy maintenance cost

We see that the amortized cost for maintaining the per-client proxy is at its minimum when the MH's SMR is high under which the MH moves frequently in between queries, which increases the chance of proxy maintenance.

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Performance Comparison with Decoupled scheme

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Summary• Client-side proxy with duties for both cache and mobility

management allows intelligent MHs to determine the best service areas for service handoffs to minimize the network traffic cost

• Computational procedure to compute the optimal service area size to minimize overall network traffic cost

• Compared with several no-proxy and/or no-caching schemes and a decoupled scheme and concluded that this scheme outperforms others in terms of the network traffic cost

• Computational procedure at static time to determine the optimal Kopt.

• MH can perform a simple look-up operation to determine Kopt based on data collected at runtime

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Questions???