Content Content Synchronization Synchronization T- - 110.5120 - - PowerPoint PPT Presentation
Content Content Synchronization Synchronization T- - 110.5120 Next generation wireless networks 110.5120 Next generation wireless networks T Helsinki University of Technology Helsinki University of Technology Jin ZhiHua ZhiHua (77168L)
T T-
110.5120 Next generation wireless networks
Helsinki University of Technology Helsinki University of Technology
Jin Jin ZhiHua ZhiHua (77168L) (77168L) Chia Chia PernHui PernHui (771 (77146H 46H) )
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– Why do we need sync ? – What Sync is about ? – Current Sync Solutions
– SyncML – OMA Data Sync Working Group – OMA SyncML Common Spec – OMA Data Sync Protocol
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– Data is modified independently – Mobile device is not always connected
Personal Information Management (PIM) e.g. calendar, task, contact, etc
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One Way File or web content replication from central server to other servers e.g. web cache proxy Two Way Data being updated at both central server and local storage e.g. email Slow Sync All data is compared and synchronized, usually performed during 1st sync or when change detection is not feasible Fast Sync Delta synchronization: Only changes since last synchronization are exchanged
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– Resource constraints on mobile device: memory, processing speed, power, bandwidth – Computation, change detection, conflict resolution at Server – Increased Manageability
Change Detection
Status flag / change log Timestamp Algebraic Set Reconciliation
Conflict resolution
Client always wins Server always wins Latest change wins Merging conflict Data duplication
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– Defines the sync communication process
– Defines the data format used during the sync process
– Serial cable, infrared, Bluetooth – Sync with desktop or other mobile device
– Cellular network, WLAN – Sync with web based (centralized) server
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– Different proprietary protocols each functioning only on a very limited number of devices, systems and data types
– Complicated task for users, manufacturers, service providers and developers – Restricted data access and delivery – Limited user mobility
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SyncML
– FusionOne – FUNAMBOL – Voxmobili – SYNTHESIS AG – Synchronica plc
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– Representation Protocol – Synchronization Protocol – First release in 2000
OBEX, etc)
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From Ref[3] Figure 2 SyncML Framework
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– Mobile service specification work – Stimulating and contributing to the creation of interoperable services
– Between any DEVICE – On any PLATFORM – In any SERVICE – Over any NETWORK
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From Ref[3] Figure 1 OMA SyncML Specification Structure and Relationships
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– Data, metadata, commands – Binary coding based on WBXML to reduce data size
– OMA Data Sync Specs
– OMA Device Management Specs
information management department, etc.) to carry out the difficult procedures of configuring mobile devices on behalf of the end users
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– To sync networked data with any mobile device
– To sync a mobile device with any networked data
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– A set of messages for certain operation (client modifications, initialization, etc) form a conceptual SyncML Package – Each message is a complete XML document
– Message size could be limited (E.g., by bearer)
and server (such as device capabilities, command, status info, data object, etc.)
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process
– Initialization
capabilities between client and server
(two-way sync required by default)
– Exchange modified data – Update ID mapping
From Ref[3] Figure 8 MSC of Two-Way Sync
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– Long in server but short in client – GUID for server, LUID for client – Server maintains the mapping between GUIDs and LUIDs
From Ref[3] Figure 5 Example: ID Mapping of Data Items
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– Status code for conflict types (delete, update, etc.) – Status code for conflict resolving result (server/ client win, merge, copy, etc.)
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information, Office documents, pictures, music, video, etc
Email and PIM data
in Windows Vista
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preferences & settings, application installation
– Status flags to keep track of changes
– All data records are sent to desktop – Performed if device is not last sync with this desktop; inevitable when sync with multiple device – Communication bandwidth and computation time increase linearly with no. of records on the device
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– Email, PIM data – Role based file or web content distribution within company – Application installation or update
Domino, Palm PDA, PocketPC, Symbian handheld, etc
centralized server
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device through peer-to-peer connections
– Each device maintains status flags for each record against every other device on the sync network – Massive memory requirement
If A record is represented by 8 bytes metadata, memory required per device would exceed 1 MB
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synchronization settings
– No maintenance of status flags – Low bandwidth requirement
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– Records could be identified by a set of integer { i1,i2,…,in} – A characteristic polynomial f(z) to describe all records,
f(z)= (z-i1).(z-i2)…(z-in)
– Consider 2 hosts A and B, we have
fA(z)= (z-iA1).(z-iA2)…(z-iAn) fB(z)= (z-iB1).(z-iB2)…(z-iBn)
– We could solve for f∆A/ f∆B using a generalized Vandermonde system of equations
fA(z) f∆A(z) fB(z) f∆B(z)
– The numerator and denominator of f∆A/ f∆B determine the differences between A and B =
subset of {i} not in B subset of {i} not in A
5.
CPISync (2) (2)
2006-11-21 28 Records, iA= { 1,2,4,16,21} Characteristic Polynomial, fA(z) = (z-1).(z-2).(z-4).(z-16).(z-21) Evaluation of fA(z) at { -1,-2,-3,-4} = { 69,12,60,61}
z
fA(z) 69 12 60 61 45 55 fB(z) 1 7 60 fA/ fB 69 22 1
Records, iB= { 1,2,6,21} Characteristic Polynomial, fB(z) = (z-1).(z-2).(z-6).(z-21) Evaluation of fB(z) at { -1,-2,-3,-4} = { 1,7,60,45} Send values { 1,7,60,45} to A The zeros of numerator and denominator are { 4,16} and { 6} respectively. Hence { 4,16} is not in B and { 6} is not in A. Use the generalized Vandermonde system to derive f∆A/ f∆B f∆A/ f∆B= z2+ 51z+ 64 z+ 65
A B
Send record { 6} to A Send records { 4,16} to B
5.
CPISync (3) (3)
in finite field F71
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Time against difference size (fixed total size = 10, 000 records)
From Ref[4] Figure 6 From Ref[4] Figure 5
Time against database size (fixed difference size)
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From Ref[5] Figure 7
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– End users: We love it! – Wireless operators: Great! But … – Device manufacturers: Why not mine?
such as algebraic set reconciliation (e.g., CPISync)
produce practical results
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[ 1] Sudhir Dixit and Tao Wu, “Content Networking in the Mobile Internet”, Hoboken, N.J Wiley cop. 2004 [ 2] OMA SyncML Representation Protocol (Candidate Version 1.2 – 09 May 2005), OMA-SyncML-RepPro-V1_2-20050509-C [ 3] OMA DS Protocol (Approved Version 1.2 – 10 Jul 2006), OMA- TS-DS_Protocol–V1_2-20060710-A [ 4] David Starobinski, Ari Trachtenberg, and Sachin Agarwal, “Efficient PDA Syncronization”, IEEE Transactions on Mobile Computing, Vol. 2, No. 1, Jan-Mar 2003 [ 5] David Starobinski, Ari Trachtenberg, and Sachin Agarwal, “On the scalability of Data Synchronization Protocols for PDAs and Mobile Devices”, IEEE Network, Jul/ Aug 2002 [ 6] Matthew Denny and Michael J. Franklin, “Edison: Database- Supported Synchronization for PDAs”, Distributed and Parallel Databases, Kluwer Academic Publishers, Netherlands, 2004.
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