A STUDY OF RECOVERY OF APPLICATION IN MOBILE
WIRELESS ENVIRONMENT USING MOBILE AGENTS
                  Miss.T.Priya1, Mrs...
2 REFERENCE ARCHITECTURE OF                  Fig. 1 shows the reference architecture of
MOBILE DATABASE SYSTEM AND        ...
recreate the execution environment as              have registered with it. When the
  soon as possible after MU reboots. ...
When MU moves out the BS its                  unification of the log. This is called as
information are not deleted automa...
strategy reduces the recovery time with
consistent behavior in all parameters.
REFERENCES
[1 ] A.Acharya and B.R.
      Ba...
A STUDY OF RECOVERY OF APPLICATION IN MOBILE
WIRELESS ENVIRONMENT USING MOBILE AGENTS




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A STUDY OF RECOVERY OF APPLICATION IN MOBILE WIRELESS ENVIRONMENT USING MOBILE AGENTS.doc

  1. 1. A STUDY OF RECOVERY OF APPLICATION IN MOBILE WIRELESS ENVIRONMENT USING MOBILE AGENTS Miss.T.Priya1, Mrs.R.Renuka M.E.2 1. II year M.E. (computer science and Engineering) {tpriya_vlb@rediffmail.com, haripriya_vlb@yahoomail.com} 2. Lecturer, Department of CSE, KSRCT Abstract-The geographical mobility of the mobile devices makes the application recovery complex which needs to store application log for the recovery of the application. This paper focuses the application log management using the mobile agents. Index Terms-MDS, mobile agents, PCS, coordinators, log unification, application recovery 1 INTRODUCTION Wireless communication through PCS transaction to nodes, transaction execution, and updation of results from (Personal Communication Systems) or clients to server. The recovery recreates GSM (Global System for mobile the module to the prior failure execution Communications) has become the state of the application. essentials of day-to-day life. Today all Application recovery is complex than telecommunication companies improve the database recovery due to the the communication quality, availability, following reasons: reliability, security to add the data 1. Presence of multiple application management capabilities in the MDS states (Mobile Database Systems).MDS is a 2. Absence of last consistent state. database system which reach the data 3. Large no of application required to location and perform the processing and manage database processing. deliver the results since each mobile units This becomes more complex in MDS will have high work load so these MDS due to will be a useful resource to perform 1. Processing demands of mobile units. transactions. 2. Existence of random handoffs. To perform the system-level functions 3. Presence of operations connected, MDS may require different transaction disconnected, intermittent connected management techniques (concurrency modes. control, database recovery, query In this logging scheme we store, processing), different caching schemes retrieve, unify fragments of application etc. log for recovery with in the constraints of Application recovery includes number the MDS. activities like transaction arrival, fragmentation and distribution of
  2. 2. 2 REFERENCE ARCHITECTURE OF Fig. 1 shows the reference architecture of MOBILE DATABASE SYSTEM AND MDS which is based on PCS or GSM. TRANSACTION EXECUTION Fig. 1 shows the reference architecture of The mobile transaction model is MDS which is based on PCS or GSM. referred to as “mobilaction”. Mobil action is defined as Ti= {e1, e2.., en} where a transaction Ti is requested at MU is called as H-MU (home MU) and is fragmented and are execute at MU. In the When the H-MU suffers handoff means the CO also changes this increases the time to commit. So the CO module can be housed either in BS, MU, DBS, and MSC. But selection of MU is not a good choice due to the following limitations: 1. Limited storage. 2. Limited power supply. 3. Unpredictable handoffs. 4. Limited availability. 3 RECOVERY PROBLEM SPECIFICATION MDS recovery is complex due to the following reasons: 1. MU’s stability: The MU may Fig. 1 Reference architecture of MDS encounter some of the following failures limited battery power, run A set of general purpose computers are out of disk space, user physically categorized as fixed hosts and BS (Base drop the MU. So any of these Station).one or more BS are connected to events may affect the MU the BSC (Base Station Controller).BSC functionality and recovery coordinates operations commanded by algorithm must take all these in to the MSC (Mobile Switching Center). consideration. The size of the cell depends on the 2. Limited wireless bandwidth: power of the BS and also the bandwidth During the recovery MU have to of wireless communication channels.. A communicate with the BS or with DBS provides full database services it other MU so in that time if there are communicates with MU through the BS no free channels it affects the and it is installed in either BS or FH.A communication quality. MU cannot provide a reliable storage so 3. Random Handoff: This affects the for recovery it relies on either BS or FH. recovery since the location of the But to support these activities BS has to MU is not available immediately be entirely modified so we create DBS as for the communication. separate nodes in wired network that 3.1 Application Log Management could be reached by any BS at any time. An efficient recovery scheme should consume minimized resources and
  3. 3. recreate the execution environment as have registered with it. When the soon as possible after MU reboots. agents are started they read the Messages that change the contents of log information created and act the log are called write events. The H- accordingly. MU records the events like • Base Agent (BaAg): This agent 1. The arrival of Ti decides which logging scheme to 2. Fragmentation of Ti be used for the current 3. Assignment of CO to a Ti environment. The BA creates an 4. Mobility history of H-MU. instance of an agent to handle 5. Dispatch of the updates to the DBS. recovery of mobilactions for each The objective of using mobile agents MU. with the MDS is to • Home Agent (HoAg): This agent 1. Reduce communication overhead. handles Mobilactions for each H- 2. Recovery time should be minimal. MU. It is responsible for 3. Easy implementation of recovery maintaining log and recovery of schemes. H-MU. 4 A MOBILE AGENT-BASED LOG • Coordinator Agent (CoAg): MANAGEMENT SCHEME This is a coordinator residing in A Mobile agent is an autonomous BS. program that suspend the execution at • Event Agent (EvAg): There are any point and resume execution from various events taking place like where is stopped in the new machine. An registration of a MU, failure of agent carries both code and the MU, handoff of MU etc. When application state. Some of the advantages any MU suffers from handoff it of the mobile agents are: can be known by the HoAg 1. Protocol Encapsulation: Mobile through this EvAg only to take agents contain own protocols in their necessary action. code itself. • Driver Agent (DrAg): During 2. Robustness and Fault Tolerance: the migration of the mobile agents When failures are detected host we need to transfer the code and system can easily dispatch the agents actual data this increases the to the other hosts for the recovery. overhead to manage this we use 3. Asynchronous and Autonomous driver agent (DrAg). Execution: Once agents are 4.1 Action of Agents When Handoff dispatched they can make the Occurs decisions independently. The HoAg moves along with the MU to the These agents do have disadvantages new BS instead of sending all its code we where high migration leads to machine send driver agent when handoff occurs. The overhead. So this must be minimized. DrAg checks whether the code for the HoAg In this architecture we have the following is present in new BS or not .If code is present agents and their logical functions: it requests the BaAg in new BS to create an instance of HoAg for this MU. If it is not • Bootstrap Agent (BsAg): This present DrAg sends request to previous BS’s agent addresses a BS failure. BaAg to take clone of HoAg and send the When a BS fails it registers in copy to the new BS to continue its operation. bootstrap agent. Once loaded this agent starts all the agents that
  4. 4. When MU moves out the BS its unification of the log. This is called as information are not deleted automatically Estimated Log Unification Time (ELUT) until it is notified by the agents of the MU. Max{BSi-LogSize/network link speed+propagation Delay} 5 FORWARD STRATEGY It also depends on the factors like The time duration between the MU whether BS is located in the same or failing and rebooting is called as different VLR. Expected Failure Time (EFT). When a 5.2 Forward Notification Scheme MU suffers from a handoff the This calculates the time spent in getting communication with the last BS is BS information from the HLR. Each disconnected only after the connection VLR stores MU’s status information with the new BS so this allows the MDS (normal, failed, forwarded).when a MU to detect the failure of the MU. MU is fails the BS informs the VLR.VLR monitored by the BS and any change in changes the status of the MU in database the situation of the MU is registered in from normal to failed. The VLR sends EvAg this makes the EFT value the information to all adjacent VLR they appropriate. When the new BS does not store the message until they receive the know the location of old Bs it is obtained denotify messages. from the HLR. If the HLR is far away it Case 1: The MU reboots in the same BS is obtained from the VLR if both BS fall where it failed. same under the control of VLR.If VLR issues denotify message to different VLR then HLR should be all VLRs. queried. If a MU crashes then the Case 2: The MU reboots in a different BS recovery of different BS needs the new but in same VLR. BS to wait until the log unification in the MU register in Bs and notified to old BS finishes. VLR. In this we provide two schemes to Case 3: The MU reboots in a different BS and a Different VLR. reduce the recovery time by unifying the log information periodically when the The MU requests for the number handoffs occurred crosses a registration then the VLR returns the predefined handoff threshold .when a identity of the previous BS and the handoff occurs the trace is transferred identity of the VLR to the HoAg of the from old BS to new B. The trace contains MU in recovered BS. The BS perform BS_ID of the new BS and log size. The log unification from the previous BS and log size updated when MU presents a new VLR sends recovery message to information. previous VLR and registration message The another scheme is to store the EFT of the MU in the new location to the old value in a variable when a MU fails it HLR. After receiving recovered message intimates the agent framework through VLR sends denotify message to all the event agent interface which starts adjacent VLRs except the MU recovered EFT clock and stopped to get recovery and removes its registration. time. 5.1 Forward Log Unification Scheme When a MU fails the trace information 6 CONCLUSION contains the log size stored in different In this paper we present the application BS’s. The HoAg based on the log size it recovery using mobile agents. Forward calculates the time needed for the
  5. 5. strategy reduces the recovery time with consistent behavior in all parameters. REFERENCES [1 ] A.Acharya and B.R. Badrinath,”Checkpointing Distributed Applications on mobile computers.”Proc. Third Int’l conf. parallel and Distributed Information Systems, pp. 73-80,1994. [2] J.Kiniry and D.Zimmerman,”A Hands- on Look at Java Mobile Agents,”IEEE Internet computing,vol. 1,no. 4,pp. 21-30,1997. [3] D.B.Lange and M.Oshima,”Seben Good reasons for Mobile Agents,”comm.. ACM,vol. 42,no. 3,1999. [4] C.Perkins,”Mobile Networking through Mobile IP,”IEEE Internet Computing,pp. 58-69,Jan.1998. [5] P. Krishna,N.H.Vaidya,and D.K.Pradhan,”Recovery in Distributed Mobile Environments,”proc.IEEE workshop Advances in parallel and Distributed Systems,Oct.1993.
  6. 6. A STUDY OF RECOVERY OF APPLICATION IN MOBILE WIRELESS ENVIRONMENT USING MOBILE AGENTS Paper Submitted By T.Priya B.Tech II year M.E. (Computer Science and Engineering) K.S.Rangasamy College of Technology, Tiruchengode, TamilNadu Guided By Mrs.R.Renuka M.E. Lecturer, KSRCT, Tiruchengode, TamilNadu

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