УДК 621.372 Ie.V. Duravkn, L.V. Demchenko, S.A. Soboleva Kharkov Natonal Unversty of Radoelectroncs, Kharkov NETWORK MANAGEMENT SYSTEM OF MULTISERVICE NETWORK Sgnfcant ncreasng of number and dversty of provded servces n multservce networks, as well as permanent ncreasng of user requrements for a qualty of servce, leads to the need of developng new management methods of multservce networks. Ths artcle s amed to solve ths problem by mprovng the structure of the network management system and management algorthm of user requests n multservce network. Also to mprove avalablty of servces the dynamc replcaton method, whch has been modfed n accordance wth the characterstcs of the proposed structure of the network management system, has been proposed. Keywords: multservce network, network management system, avalablty, SOA, dynamc replcaton method, ensurng of data consstency. 90 Introducton The opportunty of ntegratng dfferent types of servces wthn a heterogeneous network and necessty for ensurng the requred qualty of servce are the key challenge for buldng of multservce network. Fundamental factor whch wll nfluence on the achevement of ths goal s the qualty of management system of multservce network. For today the exstng management systems n multservce network ncreasngly dffcult to cope wth the ncreasng complexty and heterogenety of servces, especally wth regard to multmeda servces (ITU-T Recommendaton Y.2011, 2004). One of the most perspectve solutons for mprovng effcency of management system n multservce network s a partal transfer of means that ensure the requred qualty of servce, from a transport layer to servce management layer (Open Networkng Foundaton, 2012). In modern multservce networks practcal mplementaton of the servce management layer s performed by usng several technologcal approaches: CORBA (Specfcaton 2008), DCOM (Remote Protocol Specfcaton 2009), SOA (Westerman 2004) and others. And one of the most promsng technologes, that ensure effectve servces management n the network, s SOA. SOA archtecture and features of ts applcaton are dscussed n a large number of artcles such as: Westerman (2004), Channabasavaah et al. (2004), the means that ensure qualty of servce n SOA s represented n Km et al. (2011), Hlar (2009). The man advantage of SOA s the ablty to buld loosely coupled applcatons, focus on open standards, representaton servces n such way that they can be dscovered and accessed by the end user or applcaton. I. Formal descrpton of the nteracton of the management system components n the process of searchng, locatng and provdng servces to the user Desgnng of management system for multservce network wth servce-orented archtecture requres the ntroducton of basc structural elements of SOA (servce provder, servce consumer, servce regstry) (Westerman 2004). To desgn management system of multservce network wth servce-orented archtecture the basc structural SOA elements (servce provder, servce consumer, servce regstry) should be mplemented (Westerman 2004). Ther nteracton s represented by relatvely smple scheme: a user sends a request to the regstry to get the address of the requred servce nstance. If the requested servce nstance s found n the regstry, the response s sent to the user wth nformaton about the locaton of ths servce. Next, the consumer drectly addresses to servce for performng a specfc task. Wthn a geographcally dstrbuted heterogeneous multservce network a set of local servce regstres R v can be arranged. In multservce network the servces communcate va central servce regstry. Central servce regstry s a managed access drectory, whch stores nformaton about the locaton, qualty metrcs, descrpton, etc. of all avalable servces n the network and also greatly facltates the search of requested nformaton. Each regstry has ts own servce area MR defned by a network admnstrator: Net R {CR, R 1, R 2,, R v,, R h }, Net MR {MCR, MR 1, MR 2,, MR,, MR h} 1 1 1 2 Net S {S 1, S 2,...,S, S 1,..., S n }, Ie.V. Duravkn, L.V. Demchenko, S.A. Soboleva
Телекомунікаційні системи where R s a set of local servce regstres that are located n the multservce network Net ; MR s a set of servce areas, from whch multservce network s composed; S s a set of servces that are provded n multservce network; v s a number of servce regstry; s a number of servce area, h s a number of servce regstres and servce areas n the multservce network. The number of servce regstry s the same as the number of the servce area for whch t s responsble: v =. Due to the fact that a multservce network can nclude a set of geographcally dstrbuted subnets wth dfferent szes, the servce area may consst of multple subnets or be a part of one large subnet (Fg. 1): To account the servce s qualty metrcs t s offered to use UDDI regstry (Unversal Descrpton, Dscovery and Integraton). UDDI regstry provdes a standard mechansm for classfyng, catalogng and management of servces that allows fndng and usng them by user (Maumdar et al., 2006). The descrpton of each servce nstance n standard templates s created n the UDDI regstry. Informaton about the servce nstance s stored n the UDDI regstry as an XML-document, whch defnes the metatypes. Meta-types are dsplayng dfferent aspects of the servce functonng (the destnaton area, the owner, terms of use and varous techncal parameters (address, protocols, the values of qualty metrcs)). MR 1 MR 3 Network 4 MR 2 MR 4 Fg. 1. The placement of servce regstry n multservce network If user wants to get access to the specfc servce, then all functonally equvalent servces (FES) that are regstered n the UDDI regstry are scanned to select the nstance that satsfes user requrements. At the mplementaton stage of new servce n multservce network, servce provder publshes nformaton about ths servce (locaton, the values of qualty metrcs, etc.) n a central servce regstry CR: I(S ) {add,c, t, th,a, r,...}, (S : S Net) (add, c, t, th, a, r) I(S ) where Net s a set of elements n multservce network, I(S ) s a set of records n the regstry about servce S, lke (add,c, t, th,a,r,...), where add s servce locaton S, с s a cost of servce, t s response tme, th s servce performance, a s avalablty, r s relablty, etc. Elements (c, t, th,a, r) L, where L s a set of S qualty metrcs, based on whch the search for servce wth the requred QoS parameters s performed, L I(S ). After regstraton new servce s avalable for usng. Durng servce regstraton seral number () and servce area number () s assgned to t. If some servce s removed from the regstry, the seral numbers of other servces may change. However, the servce area number remans the same number throughout ther entre lfe cycle. II. Development of network management structure of user requests Another mportant requrement for the developed management system s the effcency of network management organzaton of user requests (ITU-T Recommendaton Y.2011, 2004). To solve ths problem the management algorthm of user requests n multservce network s proposed. Accordng to the algorthm (Fg. 2) management of user requests wll be carred out as follows: when a user wants to access a partcular servce, t sends a request to the central servce regstry. If the nformaton about the requested servce s not detected n a central servce regstry, the message about absence of servce s sent to the user. In case the requested servce s detected than the central servce regstry forwards the request to locaton server that s stuated closer to the user. After that the user request s processed and the answer s formed. IІІ. Development of functonal network management scheme of user requests In accordance wth the developed algorthm a functonal network management scheme n a multser- 91
vce network, bult on the bass of SOA, s proposed (Fg. 3). The key elements of ths scheme are the central servce regstry, local servce regstres, locaton servers and servce nstances. Fg. 2. Management algorthm of user requests n multservce network Locaton server s responsble for establshng connecton between the user and the requested servce nstance. It montors the status and locaton of servce nstances n ts servce area. When a user sends a request to get access to some servce frst tme hs request s beng processed by central servce regstry accordng to the management algorthm of user requests shown prevously. If the user sends the request agan and a copy of the servce nstance or functonally equvalent servce wthn the user servce area exsts, the request s mmedately sent to the locaton server that s stuated wthn ths servce area. Ths leads to reduce request processng tme and unloadng central servce regstry. The frst advantage of the proposed structure of network management system s the ablty to scale because the mplementaton of new types of servces and ncreasng the number of exstng servces nstances wll not requre changng the structure of the network management system. The second advantage s fault tolerance mprovng (for example n case of DOS-attacks) of the network management system at the expense of dstrbutng query processng and avalablty of copes or functonally equvalent servce nstances. Fg. 3. Block dagram of the network management system of user requests ІV. Development of the method of ncreasng the servce s avalablty n multservce network wth SOA archtecture Increasng of ntensty of requests to servce may lead to server overload and the denal of servce, n other words, to a deteroraton of servce avalablty. Ths also leads to lower value of qualty metrcs of network s servces and reducng network compettveness. Nowadays, specal methods to ensure avalablty of servces are not used for SOA, therefore the system uses only exstng advantages of archtecture to mprove servce avalable (Hlar 2009). To solve ths problem the exstng methods for ncreasng the qualty of servce should be mproved or new ones developed. One of the most effectve methods of ensurng avalablty of servces s replcaton. Possblty of usng ths technology and the effectveness of ts mplementaton s presented n Stantchev V. (2008), Yousef et al. (2011). To ncrease the servces avalablty for the proposed structure of the network management system, the dynamc replcaton method, dscussed n Demchenko et al (2013), s proposed to use. The bass of the replcaton method s performng replcaton of servce nstance n case t s necessary. Therefore, the load of users requests on the current nstance (server) s reduced and ths leads to reducton of quantty of servce denals (avalablty ncrease). It s necessary to solve three man tasks to organze replcaton of servces (Fg. 4): 92
Телекомунікаційні системи 1. Moment of decson-makng about replcaton; 2. Choose the locaton for replca; 3. Ensurng of data consstency. Decson about servce nstance copyng s made based on the analyss of the ntensty of user requests to the servce. The key parameters of the method are the replcaton threshold rep(s ) and deleton threshold del(s ). The values of these parameters affect on the ntensty of replcaton and the server overload of unclamed replcas. Fg. 4. Complex algorthm of servce replcaton The central regstry servce montors the number of requests for each servce. If the requests count to any of the partcular servce n some servce areas (ncludng servce areas CR) exceeds the threshold then a decson about replcaton s made. To accomplsh ths, future replca locaton must be determned. For ths purpose, n the specfed servce area, the server that has the necessary resources to accommodate the replca must be defned. If the requred server s found then the regstry sends a request to the servce S to create a copy. In the request t specfes the locaton for future copes. After replcaton the answer wth the results of operaton s sent to the locaton server of CR servce area. In case the replcaton was successful n the descrpton of the prmary servce nstance s specfed copy mark 1 and replca s address add(s k ). In case the server s located n the R v servce area, ths nformaton s also sent to the locaton server to regster the replca. If the avalable server s not found n the regstry database, the replcaton s canceled and the regstry starts checkng next servce counter. The locaton server of R v also montors the ntensty of user requests to servces. If the rate of requests to the servce nstance exceeds the replcaton threshold, the locaton server decdes to create an addtonal copy of the resource n accordance wth the algorthm prev- 93
ously submtted. If the rate of requests to the replca falls below the deleton threshold the locaton server decdes to remove the replca for free up space on the server. After removal operaton, the nformaton about replca S k s deleted from the local servce regstry R v. Also, ths nformaton s sent to a central servce regstry. After the message about removal of replca s receved, CR deletes nformaton about copy mark and replca s address from the descrpton of the prmary servce nstance. The effectveness of the method of dynamc replcaton s largely dependent on the choce of methods that ensure data consstency. Often the transacton s used to synchronze the replcas (Tanenbaum et al., 2006, Tansch 2000). Accordng to the type of trans- acton a synchronous or asynchronous replcaton wll be used to synchronze the servce replcas. Today, many methods that ensure data consstency have been developed (Tanenbaum et al., 2006). The usage of these methods depends on the replcaton strategy, whch s used n the network, the type of provded servces and the requrement of strct consstency. Accordng to the fact that SOA always has a prmary copy of servces, whch may change only a provder, t s advsable to use the protocols based on the prmary copy to ensure data consstency. To perform synchronous replcaton as a protocol that ensures data consstency t s proposed to modfy the prmary backup protocol (Fg. 5). Fg. 5 The prmary backup protocol If a provder wants to change any data t sends a request to the prmary servce nstance S wth servce updates. Servce S sends the request to the central servce regstry to check for a presence of copes marks and ther addresses. If the copes marks do not exst 0, the update process s beng completed, and the servce becomes avalable agan. If the regstry s answer wll contan nformaton about copes and ther addresses, the servce wll send the updated data to all ts replcas. When all update acknowledgments have been receved from all replcas, the servce sends to provder a confrmaton of acceptng these changes and the update process s beng completed. Update process s performed as a sngle atomc operaton or transacton that ensures servce copes consstency. To perform asynchronous replcaton as a protocol that ensures data consstency t s proposed to use a nonblockng protocol. The dfference between a nonblockng protocol and a prmary backup protocol s that the update of the prmary servce nstance and replcas are made usng ndvdual transactons, after whch servces are avalable for user. Thus developed complex method of servces replcaton allows solvng a set of tasks whch s needed to perform replcaton and ensure data consstency. V. Estmaton of the network management system effcency To analyze the effcency of the developed network management system the smulaton model of a multservce network was developed. The developed system can operate n two modes - wth replcaton and wthout replcaton. Graphcal representaton of the model s shown n Fg. 6. In mode wthout replcaton, all user requests are sent to the central servce regstry, whch stores nformaton about the locaton of the requested servce. Locaton server of CR defnes the placement of server 94
Телекомунікаційні системи MR MR 1 MR 2 Fg. 6. The smulaton model of the multservce network whch ncludes the requested servce and establshes a connecton between the user and the server. At the same tme the server that stores the requested servce may be n a remote part of the network that brngs an addtonal delay to the delvery of servces. In the case of the growng servce nstance popularty, the level of ts avalablty wll be sgnfcantly reduced, that negatvely affects on the values of qualty metrcs. In the second mode, as shown n Fg.6, the load on the some servces s dstrbuted over the network by applyng of mode wth replcaton. In case the number of requests from a partcular part of the network to a remote servce nstance exceeds the replcaton threshold, then the decson to create a replca of the requested servce near servce users wll be taken. Thus, n accordance wth management algorthm of user requests (Fg. 2), a user requests that was receved by the central servce regstry s redrected to the locaton server of R v regstry, where a replca of the servce s regstered. Analyss of smulaton results has shown that applyng of the developed network management system can ncrease servce s avalablty on 15% durng congeston. Moreover, n case the rate of requests s ncreased the dfference between the level of avalablty n replcaton and wthout replcaton mode can also be ncreased and can reach a values close to 30% (Fg. 7). Fg. 7. Level of avalablty In case the number of requests from some part of the network to the servce nstance ncreases then the applyng of replcaton mode reduces the workload of backbone lnk (Fg. 8). Resdual traffc s formed due to updates that are beng sent between replcas. Fg. 8. Level of traffc of backbone lnk 95
Conclusons In ths paper the structure of management system of multservce network wth servce-orented archtecture s presented. As the key elements of the structure the central servce regstry, local servce regstres, locaton servers and servce nstances are proposed to use. Processng of user requests wthn the proposed structure s performed n accordance wth management algorthm of user requests, whch s presented n the artcle. The man advantages of the developed network management system are the scalablty and fault tolerance. To ncrease the avalablty of servces n multservce network wth SOA archtecture the dynamc replcaton method was developed. Ths method allows creatng, f necessary, addtonal copes of the requested servces near servce users. To ensure data consstency the prmary backup protocol was modfed. The analyss of the proposed structure of management system of multservce network was performed usng smulaton models. The results of research showed that applyng of the developed system allows ncreasng the avalablty of network servces, reducng the access tme to the network resources, and reducng the workload of the backbone lnk and the central servce regstry. Thus, usng of replcaton allows performng traffc balancng n the network, and also mprovng the qualty of servce n multservce networks n general. References 1. ITU-T Recommendaton Y.2011 (2004). Seres Y: Global nformaton nfrastructure, nternet protocol aspects and next-generaton networks - General prncples and general reference model for Next Generaton Networks. Geneva: Internatonal Telecommuncatons Unon. 2. Open Networkng Foundaton (2012), "Software- Defned Networkng: The New Norm for Networks," ONF Whte Paper, Aprl 13. 3. Specfcaton (2008) Common Obect Request Broker Archtecture (CORBA) Verson 3.1.1. Obect Management Group, Inc., 2008. 250 р. 4. Remote Protocol Specfcaton (2009) Dstrbuted Component Obect Model (DCOM). Copyrght. Mcrosoft Corporaton. USA, 124 p. 5. Westerman J. (2004) SOA Today: Introducton to Servce-Orented Archtecture : http://www.nformatonmanagement.com/news/7992-1.html. 6. Channabasavaah K., Holley K., Tuggle E.M. (2004) Mgratng to a servce-orented archtecture. IBM. 7. E. Km et al., (2011) Web Servces Qualty Factors Verson 1.0. Commttee Draft 02, OASIS, July 2010. http://docs.oass-open.org/wsqm/wsqf/v1.0/ws-qualty- Factors-v1.0-cd02.html (last accessed: July 23, 2011). 8. Hlar M.O. (2009) Qualty of Servce (QoS) n SOA Systems A Systematc Revew, Master thess, Unverstat Poltecnca de Catalunya. 9. Maumdar B., Verma A., Mysore U. (2006) Enhance UDDI to manage Web servces IBM developerworks. 10. Stantchev V. (2008) Effects of Replcaton on Web Servce Performance n WebSphere ICSI Techncal Report TR-08-003. 11. Ans Yousef, Douglas G. Down (2011) Request Replcaton: An Alternatve to QoS Aware Servce Selecton Proceedngs of the 2011 IEEE Internatonal Conference on Servce-Orented Computng and Applcatons, SOCA '11, Р. 1-14 12. Demchenko L., Sad Halava Fauaz. (2013) Increasng the Avalablty of Servce n Multservce Networks Constructed on the Bass of SOA, Proceedngs of the 12th Internatonal Conference "CADSM" - Lvv-Polyana, Ukrane. Р. 69-71 13. Andrew S. Tanenbaum, Maarten Van Steen (2006) Dstrbuted systems: prncples and paradgms, 2th edton, publshed: oct 2, by Prentce Hall, pages 704. 14. Tansch P. (2000) Atomc Commt n Concurrent Computng IEEE Concurrency. vol. 8, no. 4. Р. 34-41. Надійшла до редколегії 11.08.2015 Рецензент: д-р техн. наук, проф. Д.О. Агєєв, Харківський національний університет радіоелектроніки, Харків. 96 СИСТЕМА УПРАВЛЕНИЯ ДОСТУПНОСТЬЮ В МУЛЬТИСЕРВИСНЫХ СЕТЯХ Е.В. Дуравкин, Л.В.Демченко, С.А. Соболева Значительное увеличение числа и разнообразия предоставляемых услуг в мультисервисных сетях, а также постоянное повышение требований пользователей к качеству обслуживания, приводит к необходимости разработки новых методов управления мультисервисными сетями. Эта статья направлена на решение этой задачи, путем совершенствования структуры системы управления сетью и алгоритма управления пользовательскими запросами в мультисервисных сетях. Кроме того, для повышения уровня доступности услуг, был предложен метод динамической репликации, который был модифицирован в соответствии с характеристиками предлагаемой структуры системы управления сетью. Ключевые слова: мультисервисная сеть, система управления сетью, наличие, SOA, метод динамической репликации, обеспечение согласованности данных. СИСТЕМА УПРАВЛІННЯ ДОСТУПНІСТЮ В МУЛЬТИСЕРВІСНИХ МЕРЕЖАХ Є.В. Дуравкін, Л.В.Демченко, С.А. Соболева Значне збільшення числа і різноманітності послуг, що надаються в мультисервісних мережах, а також постійне підвищення вимог користувачів до якості обслуговування, призводить до необхідності розробки нових методів управління мультисервісними мережами. Ця стаття спрямована на вирішення цієї проблеми, шляхом вдосконалення структури системи управління мережею і алгоритму управління користувацькими запитами в мультисервісних мережах. Крім того, для підвищення рівня доступності послуг, був запропонований метод динамічної реплікації, який був модифікований відповідно до характеристик запропонованої структури системи управління мережею. Ключові слова: мультисервісна мережа, система управління мережею, наявність, SOA, метод динамічної реплікації, забезпечення узгодженості даних.