Ad hoc Service Grid A Self-Organizing Infrastructure for Mobile Commerce

Transcription

1 Ad hoc Servce Grd A Self-Organzng Infrastructure for Moble Commerce Klaus Herrmann Berln Unversty of Technology Emal: klaus.herrmann@acm.org Web: PTB-Semnar, 3./4. November 2004 PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 1

2 Outlne > Ad hoc Servce Grd > General vson, advantages, and challenges > Research Focus > Self-organzng Servce Dstrbuton > Complementng Concepts > Summary and Conclusons PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 2

3 Wreless Servces at medum-szed Locatons > Locatons: > Constructon stes, hosptals, shoppng malls etc. > Servces (e.g. at a shoppng mall) > Local, faclty-specfc servces for local users > Examples: navgaton, product fnder, reservaton (e.g. restaurant) > Usng cellular phone networks > Non-local communcaton, expensve, low-bandwdth > Usng WLAN access pont technology > Wrng s extremely expensve(!), nflexble, centralzed server PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 3

4 Ad hoc Servce Grd > Basc dea: Use an ad hoc network > Dstrbuton of PC-lke computers (Servce Cubes) at the locaton > Wreless network nterface, power connector, no perpherals > Drect communcaton between neghborng Servce Cubes > Mult-hop communcaton between Cubes that are further apart > Users access servces va nearest Servce Cube > Advantages > Communcaton s free of charge, modest expenses for setup > No hgh ntal expenses for monolthc central server > Flexbly scalable: addng or removng Cubes durng runtme s easy PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 4

5 Example Setup: Shoppng Mall 90 m 180 m PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 5

6 General Challenges > Decentralzaton and Self-Organzaton > Dstrbuted resources Control and organzaton s dffcult > Servce nfrastructure should be nvsble > Mnmal manual nterventons > Self-organze and adapt to changng condtons > Personalzaton vs. prvacy and securty > Offer personalzed servces whle provdng prvacy > Interactons must be secure > Busness Models > Indrect revenue PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 6

7 Current Research Focus > Self-organzng dynamc servce dstrbuton > Dynamc replcaton and node selecton to meet current demand > Maxmze QoS: response tmes perceved by users > Mnmze network load, balance processng load > Servce lookup and dscovery > Enable users to dscover servces and fnd best servce replca > Data consstency > Acheve data consstency among replcated stateful servces > What does an overall ASG Mddleware/Servceware look lke? PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 7

8 Self-organzng Servce Dstrbuton > Installaton: one servce replca postoned arbtrarly > Clents start accessng the servce > Assumpton: Spatal dstrbuton of requests s non-unform > General Approach: Use request patterns to gude dstrbuton > Clents always choose closest servce > Request tree T s recorded at each servce replca s Cube > Servce s replcated or mgrated to request hot spots PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 8

9 Dstrbuton algorthm > Runs perodcally at the replca s Cube > Compute weghtng functon M n for each node n n the tree > Fnd nodes and j n request tree T such that > and j are not n the same subtree > M > M j > M k for all k wth k j > Mgrate servce to node f t s domnatng (M >> M k for k) > Replcate servce to and j f both are domnatng and the servcespecfc replca lmt has not been reached > Dssolve replca f dle for too long PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 9

10 Weghtnng Functon M n M n = ( D + ) ( ) n 1 Rn t = t k > Informally: Number of transmssons caused by n > Inputs > D n : Hop Dstance of node n from servce s node > R n (): Number of requests transmtted by node n at tme ndex > t: the current tme ndex > k: length of relevant request hstory tme wndow PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 10

11 Smple Example Requests produced: R n (): D n +1: =100 (transmtted) M n : Requests produced: R n (): D n +1: =60 (transmtted) M n : PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 11

12 PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 12 Oscllaton Avodance > Mantan a hstory of adaptatons performed locally at each node > Adaptaton = (Destnaton, Request Tree) > Check for past adaptatons wth smlar Request Trees before performng an adaptaton > Smlarty of two trees T 1 and T 2 s gven by ( ) { } { } wth = r N r N N N M M M M T T s \ \, = k k k k k j T r T N N M root node from ID of node IDs from Set of ff 0 : :

13 Emergent Effects > Replcas fnd postons where traffc s balanced > None of the nodes nvolved n the request flow stands out n terms of network load produced (no domnatng nodes) > Tunable parameter: Domnaton Factor > Preset lmt on per-servce number of replca controls the average dstance between servce and clents > Tunable Parameter: Replca Lmt > Oscllaton avodance reduces unnecessary adaptatons whle stll keepng the system reactve > Tunable Parameter: Smlarty Threshold > Processng load s balanced > Replcaton and choce of nearest servce by clents PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 13

14 Result Adaptve Reducton n overall Traffc Overall Transmssons #Transmssons Tme [smulaton steps] PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 14

15 Work not Covered n the Talk > Dstrbuted lookup servce for moble servces > Forwardng of clent requests to current servce locaton > Lazy propagaton of locaton changes by snoopng meta nformaton pggybacked n servce reples Self-reparng > Data consstency n stateful servces > Weak, optmstc consstency model (nspred by Bayou) > Current work! > Archtectural mplcatons on overall mddleware > Puttng t all together > Past, current, and future work! PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 15

16 Summary and Conclusons > Ad hoc Servce Grd: Basc vson for a servce provsonng platform for medum-szed locatons > Conceptual groundwork (algorthms and protocols) > Self-organzng servce dstrbuton > Smple, usage-drven algorthm > Transmsson hot spots attract servces untl network load s balanced > Oscllaton s damped whle the system remans reactve to changes > Processng load s balanced PTB-Semnar 04. Nov. 04 Herrmann - Ad hoc Servce Grd 16

17 Thank you. Queston and comments are welcome. Klaus Herrmann Intellgent Networks and Management of Dstrbuted Systems Berln Unversty of Technology

18 Telecommuncatons Insttute Faculty IV Electrcal Engneerng & Computer Scence TU Berln phone: fax: Secretary EN 6 Enstenufer 17 EN-Gebäude D Berln Germany Intellgent Networks and Management of Dstrbuted Systems

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