BS: ATestbed for the Evoluton of ntellgent Broadband Networks toward TNA Marc0 Lstant, Unversty of Roma "La Sapenza" Stefan0 Salsano, CoRTeL ABSTRACT Ths artcle analyzes a possble path for the evoluton of telecommuncaton networks toward open dstrbuted archtectures lke the TNA-C archtecture. The results of a research project called BS carred out wthn the CoRTeL laboratory are presented. The BS project starts from the actvtes of the ACTS project NSGNA, whch has proposed and demonstrated an archtecture for the ntegraton of the ntellgent network concept over B-SDN platforms (the so-called ntellgent broadband network). n the BS approach, TNA servce components replace the tradtonal N servce logc, provdng the ntellgence needed to control broadband servces n a very flexble and open envronment. The handlng of the transport connectons s performed n a more tradtonal way, explotng the capablty offered by the BN. Ths artcle focuses on how the TNA and BN paradgms can proftably nteract, provdng the ntellgence to support advanced multmeda servces. he growng demand for broadband multmeda, T multpont, and multparty servces requres ntellgent and flexble servce provsonng approaches n the broadband networks. Unfortunately, the standardzaton process of ATM broadband ntegrated servces dgtal network (B-SDN) s not phased wth these needs; there exsts a gap between servce requrements (e.g., multconnecton, multpont-to-multpont call confguratons) and control capabltes specfed by the nternatonal Telecommuncaton Unon - Telecommuncaton Standardzaton Sector (TU-T) Q- seres Recommendatons. As an example, sgnalng capablty set (SCS) 2.1, under approval n 1997, only supports sngleconnecton bdrectonal pont-to-pont and undrectonal pont-to-multpont call connectons. n order to fll ths gap, the ntegraton of B-SDN wth overlay archtectures lke the ntellgent network (N) and TNA has been consdered. N s ntrnscally a centralzed soluton, based on separaton of swtchng control functons mapped n two functonal enttes, namely servce swtchng functons (SSFs) and call control functon (CCF), and servce control functons, whch are mapped n the SCF functonal entty. The servce control functons are located n a few centralzed nodes that remotely control the swtchng nodes va the NN protocol. N s able to provde a platform to enrch the functonalty furnshed by the B-SDN n order to realze the handlng of several basc bearer connectons n a coordnated manner, accordng to the servce logc requrements. Ths soluton has been studed n depth by the NSGNA (N and B-SDN Sgnalng ntegraton on ATM platforms) project [ 11, carred out n the framework of the European ACTS program. NSGNA focused on the defnton and mplementaton of an ntellgent broadband network (BN) archtecture [2] by applyng the N concepts on top of the transport nfrastructure provded by ATM technology. Greater flexblty n servce creaton and management n a multprovder, multvendor envronment could be acheved by the archtecture developed by the Telecommuncatons nformaton Networkng Archtecture (TNA) Consortum. The TNA archtecture [3] addresses future nformaton and multmeda servces and provdes a means to operate servces over a wde varety of technologes. TNA explots advances n dstrbuted computng and object-orented analyss and desgn to mprove nteroperablty and reuse of software and specfcatons. n TNA, servces are provded by means of the nteracton of computatonal objects (COS) whch contan logc and data and offer specfc operatons. The communcatons between COS s supported by the dstrbuted processng envronment (DPE) whch allows arbtrary dstrbutons of COS. The applcaton of a pure, fully complant TNA approach does not seem realstc, at least n a short-medum-term perspectve. On one hand, t would requre the avalablty of advanced broadband swtchng platforms offerng an open nterface toward elementary swtchng functons. On the other hand, t would mply complete replacement of exstng sgnalng protocols and the avalablty of TNA-complant termnals. An analyss of the mgraton steps of telecommuncaton networks toward TNA can be found n [4], where the advantages of ntegratng N and TNA concepts are also dscussed. These advantages manly relate to: The hgh nteroperablty level between applcatons runnng on DPE The capablty of defnton of multple ponts of control for a servce The possble ntegraton of servce management and servce control Ths artcle s focused on the near-term perspectve for the ntegraton of TNA archtecture n a broadband envronment. Some of the man achevements of the BN archtecture demonstrated by NSGNA can be successfully reused n ths context. Dfferent alternatves can be envsaged, consderng to what extent the features offered by BN can be reused or substtuted by TNA [5]. Fgure 1 shows two alternatve scenaros. n scenaro 1, the BN offers control of sngle B-SDN con- 78 0163-6804/98/$10.00 0 1998 EEE EEE Communcatons Magazne June 1998
~ _. nectons; the TNA servces have to coordnate a set of sngle pont-to-pont and/or pont-tomultpont B-SDN connectons to buld complex servce confguratons. As n the tradtonal N envronment, the means to control sngle connectons are gven by the basc call state model (BCSM) [6]. The BCSM models the evoluton of a B-SDN call and provdes trggers for nteractons wth TNA connecton management objects through a specalzed adaptaton unt (AU). A hgher-level nterface s foreseen n scenaro 2. Coordnaton of several connectons among a number of partes s performed by the BN tself usng the sesson model [7]. The sesson model allows a pool of B-SDN connectons to be managed by TNA wth a sngle Scenaro 1 pk BN-TNA nterface nteracton. t releases TNA from connecton management aspects by maskng basc connecton operatons and hdng the BCSM level. The second scenaro should lead to a smoother ntroducton of TNA due to the nherent smplfcatons of nteractons and avods the need to support DPE n every swtchng node. Moreover, scenaro 2 could possbly allow smple mgraton from BN archtecture. A detaled archtectural model realzng ths scenaro s dealt wth n ths artcle. Feld experences arsng from the mplementaton of the above-mentoned concepts n a laboratory demonstrator called BS (mplementaton of ntegrated N and B-SDN Sgnalng) are descrbed as well. The man goal of the BS project s to realze a testbed to nvestgate and test advanced control archtectures for broadband multmeda servces and, n partcular, archtectural aspects nvolved n applcaton of TNA concepts on top of B- SDN nfrastructure. n the BS context the BN archtecture (as proposed by the NSGNA project) has been assumed as the startng pont. BN has been enrched manly by ntroducng pont-to-multpont call handlng and the sesson creaton capablty needed to realze multsesson servces. The tradtonal servce logc programs runnng n the N SCF are replaced by TNA-complant COS. n the followng ths replacement s referred to as TNArzaton of the SCF. A specfc AU s defned to allow nterworkng of the TNA world wth the enhanced BN. n partcular, the man achevements reported n ths artcle are: Defnton of BCSM for B-SDN pont-to-multpont calls and enhancement of the model for call unrelated nteractons Enhancement of the concept of sesson control by consderng the ntroducton of multple-sesson concepts, allowng dstrbuton of a sesson over multple BN nodes Specfcaton and mplementaton of an AU, allowng nteracton between TNA COS and BN Partcularzaton of the TNA computatonal model, allowng B-SDN connecton handlng Mappng of the TNA servce sesson graph n the BN sesson model n the followng secton the archtecture for the evoluton of the BN toward B-SDN/TNA as mplemented n the BS testbed s presented. The secton after that s focused on a specfc descrpton of BN functonalty enhancement for nteracton wth the TNA envronment. TNArzaton of SCFs s dealt wth next. Two aspects are manly dscussed: the TNA computatonal model and the nterworkng functonalty for the nteracton wth the BN envronment. Fnally, as a. #? computatonal Scenaro2 node Fgure 1. Dfferent scenaros for ZBNTZNA ntegraton......-.. BN-TNA nterface BN 1 node.._ -_ -. -~ case study, the provson of broadband vdeoconference (B- VC) servce va the mplemented archtecture s dscussed. BS CONTROL ARCHTECTURE The BS control archtecture takes the BN archtecture (as proposed by the NSGNA project [l]) as the startng pont to ntroduce advanced features and explot the mgraton toward TNA. A descrpton of the BN concept and archtectural elements can be found n [8]. n BS, the BN functonal elements n the sesson control doman and B-SDN control doman (e.g., B-SSF, B-CCF) are enrched, manly by ntroducng the capablty to handle pont-to-multpont calls and create sessons n the SCF-SSF drecton, as needed to realze multsesson servces. Wthn the servce control doman, the tradtonal servce logc programs runnng n the B-SCF wll be replaced by TNA-complant COS. The TNA servce archtecture s fully exploted for the realzaton of the servce logc, whle the handlng of connectons s performed by means of the N capabltes of the BN. A specfc AU s defned to allow nterworkng of the TNA world wth BN. Unlke n the tradtonal N, where an nstance of a servce logc program (SLP) s nvoked n the B-SCP to control a specfc servce nstance, n the BS archtecture the B-SCF performs the nterworkng between the BN and TNA archtectures. The servce logc s performed by a set of TNA COS. Nevertheless, n the scenaro shown n Fg. 2 the B-SCF can offer an external behavor whch s fully compatble wth tradtonal N archtecture. Accordng to the BN archtecture, the man task of the B- SSF functon s to manage the sesson model [7]. The B-SSF performs the mappng of sesson-related operatons nto calllevel operaton and vce versa. The B-SSF has been enhanced n the BS archtecture to support pont-to-multpont calls, SCP-ntated setup of a call-unrelated assocaton, and creaton of a sesson ntated by the B-SCF. A sesson wthn the B-SSF can handle an arbtrary combnaton of basc calls, pont-to-multpont calls, and call-unrelated assocatons. The B-CCF and broadband call-unrelated servce functon (B-CUSF) allow nteracton of the N wth the B-SDN control and sgnalng functon. The BCSM and basc call-unrelated state model (BCUSM) allow the servce logc to control the B-SDN calls and call-unrelated assocatons, respectvely. n the context of BS, the call modelng has been enhanced to support pont-to-multpont calls and SCP-ntated callunrelated assocatons. n the BS archtecture, a servce can span multple sessons n dfferent B-SSPs. The servce logc n the B-SCP s able to create a new sesson n a B-SSP whch s not already nvolved n a servce. Therefore, t s a task of the B-SCF to EEE Communcatons Magazne June 1998 79
Fgure 2. The BS archtectural model, B-N (0 TNA Servce archtecture computatonal objects SCF/TlNA adadtatron unt / \\ png between the B-NN nformaton flows and the methods defned n the TNA COS nterfaces. For example, when a user requests a servce, the B-SSF sends a B-NN operaton to the B-SCF. Wthn the TNA servce logc as a consequence of ths message, the set of COS needed to provde the requred servce wll be nstantated and confgured. On the other hand, when TNA servce logc needs to set up a connecton, the AU wll translate ths request nto one or more B-NAP operatons. Snce a sngle servce nstance can span several B-SSPs, coordnaton of the dfferent sessons s performed by the TNA servce logc. The TNA servce sesson graph (SSG) s used to keep the overall nformaton about the state of a servce: the nvolved users, the network resources, and thek relatonshps. - -..._ Fgure 3. BNTNA nterworkng. correlate the dfferent sessons and mantan the overall vew of the servce. The TNA part of the archtecture wll accomplsh ths task. n order to TNArze the B-SCF, a set of TNA COS and ther nteracton to provde the dfferent multmeda servces must be defned. nterworkng of TNA servce archtecture wth BN functonal enttes s realzed by means of an nterworkng object (wo) n the SCFTNA AU. Fgure 3 hghlghts the proposed BN/TNA nterworkng. The B-NAP protocol defned for the BN archtecture can be used on the B-SSFB-SCF nterface. B-NAP provdes the means to set up and release connectons between end users and to establsh communcaton between the user and the servce logc. The user termnals and swtchng ATM platforms wll not change the way they nteract wth the servce logc wth respect to the BN. As a matter of fact, n the proposed scenaro there are no TNA-complant end users and no TNA applcatons runnng on user termnals. The user equpment s the same as that used n the BN [9]. The role of the wo wthn the AU s to realze the map- BROADBAND CALL CONTROL FUNCTON AND SERVCE SWTCHNG FUNCTON EVOLUTON n ths secton an evoluton of the BN wth respect to the outcome of the NSGNA project s proposed. The enhancements concern the B-SSF, B-CCF, and B-CUSF functonal enttes, whch belong to the sesson control doman and the B- SDN control doman. n the context of the BS archtecture, the TNA-based servce logc complements ths evoluton n the servce control doman. t s worth notng that the enhancements proposed n ths secton could also be appled to a classcal BN wthout any TNA nvolvement. PO NT-TO-M U LT PONT CALL MODELNG A pont-to-multpont calllconnecton allows dstrbuton of a undrectonal flow of data from one source, the root party, to a set of snks, the leaf partes. The basc pont-to-multpont call s specfed by TU-T Recommendaton Q.2971 [lo] at the user-network nterface (UN) and Q.2722.1 [ll] at the network-node nterface ( 1). A pont-to-multpont call s ntated by the root by sendng a SETUP message whch explctly requests the pont-to-multpont confguraton. The root party can send ADD PARTY messages to add further leaves and DROP PARTY messages to remove partes from the call. A 80 EEE Communcatons Magazne June 1998
leaf party can drop tself from a call, but cannot jon tself to a pont-tomultpont call. The call can be explctly torn down by the root by sendng a RELEASE message, whch releases all the leaves. The frst requrement for an N call model for a pont-to-multpont call s to allow montorng and control of the events n a basc pont-to-multpont call (.e., ntated by the root usng UN1 sgnalng), such as call setup, party addton, party answer, call release, and party release. Followng the BN approach for SCP-ntated operaton, the addtonal requrements for call modelng are to support SCP-ntated party addton (addton of partes to an already establshed pontto-multpont call on behalf of the servce logc) and SCP-ntated ZNpont-to-multpont call setup (establshment of a pont-to-multpont confguraton on behalf of the servce logc). Moreover, t must be consdered that n a pont-to-multpont call there s a set of partes whch can evolve ndependently, makng t nfeasble to control them wthn a sngle state machne. The avalable N standards descrbe the call model for a pont-to-pont call wth a sngle connecton, as sutable for plan old telephone servce (POTS) and narrowband SDN (N-SDN). The NSGNA project has defned a BCSM sutable for BN based on ths classcal BCSM. The proposed soluton foresees reusng the BCSM defned n the BN archtecture, whch wll be called the call control manager (CCM) hereafter, and addng a state machne representng each leaf party, called the party control manager (PCM). Consderng the setup of a tradtonal pont-to-multpont call (.e., set up by the root), when the setup ndcaton s receved by the B- CCF, a PCM s nstantated and wll evolve n parallel wth the CCM, whch s nstantated as n the pont-to-pont case. The CCM represents the call state, whle the PCM represents the state of the frst leaf party. The leaf partes that wll be successvely connected are montored by new nstances of the PCM, as shown n Fg. 4. A complete descrpton of the ponts n call (PCs) and detecton ponts (DPs) defned n the CCM and PCM s beyond the scope of ths fgure [12]. The DP n the PCM can be armed accordng to the servce logc requrements. As an example, the Add Party Attempt DP s encountered when the root sends an ADD PARTY message. f t s necessary to montor each addton of a new party to allow an N-based access control servce or accountng servce, ths DP wll be ],, (, Pont-to-pont setup Root U BCSM modelng Frst leaf CCM: Call control manager PCM: Party control manager.-.-.-.a Fgure 4. BCSMnstances for the control of. a pont-to-multpont - call. armed to report each attempt. The DPs n the PCM can be armed ndependently for each leaf accordng to servce requrements. The DPs n the CCM allow montorng of the state of the whole call: for example, the Call Released DP, f armed, can detect the release of the whole call requested by the root Dartv. The hrdducton of SCP-ntated party addng and pont-to-multpont call setup s realzed by means of extenson to the CCF nsde the nodes, wth no mpact on sgnalng. For the SCP-ntated addng of partes, the CCF has to be modfed to receve a request from the B-SSF to add a new party and to control the sgnalng toward the leaf party on the outgong UN1 or NN lnk. The addng of these partes wll not be communcated to the root at the sgnalng level because the Q.2971 procedures do not allow t. The same approach s appled for SCP-ntated pont-to-multpont call setup. Snce a node cannot set up a pont-to-multpont call toward a root party, a pont-to-pont call s establshed to support a undrectonal connecton from the root to the node; then an ndependent (wth respect to B- SDN sgnalng) pont-to-multpont call toward the leaf partes s set up. The two phases for the setup of an N-ntated pont-to-multpont call are depcted n Fg. 5. The setup of an addtonal leaf party s also shown. The dotted arrows show the control plane relatonshps (the drecton represents the party who receves the setup), whle the thck arrows show the user plane lnks (the drecton represents the flow of data). The modfed CCF wll correlate the sgnalng messages, dalog wth servce logc, and control the through-connecton of the user plane lnks. As far as the BCSM modelng s concerned, the partes that are added on behalf of the servce logc wll be modeled by nstances of the PCM: the servce logc can control the result of the party setup, montor the release of the partes, and so on. The CCM represents only the status of the root party (e.g., notfyng a release comng from the root). As far as the sesson model enhancements are concerned, the bearer connecton object wll be extended to support a set of more than two legs. A new attrbute, confguraton, s added to the bearer connecton object wth possble values pont-to-pont and pont-to-multpont. The leg objects wll represent the root and set of leaves that compose a pont-tomultpont call. The new flows that must be added to the set of B-SSF/B- SCF nformaton flows are reported n the frst two rows of [y&-q Pont-to- 0 Root Pont-to-mult Dont Frst phase: setup of the lnk Second phase: setu of the lnk Setup of the lnk toward toward the root party toward a eapparty an addtonal leaf party.- -_ - -. - ---- - -- - Fgure 5. Setup of a SCP ntatedpont-to-multpont call. 0, Leaf 2 ' EEE Communcatons Magazne June 1998 81
_- ~ ~ usage of net\\ 01 k csourccs. 111 ths soluton the sessons n each B-SSP - represent only a partal vew of the Gcnerc Functonal Protocol - - Add party and servcc confguraton hltrgng of Multple sesson 1 Create sesson Table 1. Newly defned B-SSFB-SCF nformaton flows. Table 1. The Add pont-to-multpont bearer nfo flow allows the servce logc to establsh a SCP-ntated pont-to-multpont call provded the root party and the lst of leaf partes are connected. A bearer connecton object wll be created wth the confguraton attrbute set to pont-to-multpont, a party object wll be created for each party that does not stll exst n the sesson, and one leg object for each party wll be created to represent the lnk wth the bearer connecton. The Jon partes to pont-to-multpont bearer nfo flow allows the servce logc to add a set of new leaf partes to a pont-to-multpont (ether root-ntated or SCP-ntated) call. An exstng bearer connecton object s provded n the message, whle the same rules for creatng party and leg objects apply as for the Add pont-to-multpont bearer nfo flow. GENERC FUNCTONAL PROTOCOL MODELNG The out-channel call-unrelated nteracton allows drect exchange of servce nformaton between the user termnal and servce logc. At the UN1 of the B-SDN the nformaton s exchanged va a connecton-orented bearer-ndependent (COB) sgnalng assocaton, as defned n the Generc Functonal Protocol [13]. A smlar feature s already ncluded n the N Capablty Set 2 Recommendatons [6], where t s called user servce nteracton (US). The US1 can complement the tradtonal n-band user nteracton va the B-P, whch n the narrowband N allows the servce logc to send voce messages and collect DTMF tones. The US1 mechansm s more effcent than tradtonal n-band nteracton and s especally sutable f the termnal equpment s "smart" as n a broadband context. n the BN archtecture, smple support s provded for ths mechansm. Only the user can ntate a COB assocaton to send some servce nformaton, as used for regstraton procedures n a vrtual prvate network. n the BS context, the SCP can ntate a COB assocaton toward any user and can use ths assocaton to convey any nformaton (e.g., an nvtaton to take part n a servce). The COB assocaton wll last as long as the user servce communcaton s needed. No specfc enhancements to the statc sesson model are needed to support the SCP-ntated call-unrelated assocaton, whle the dynamc behavor s extended and the Jon party and bearer unrelated connecton has been added (Table 1). Ths nfo flow allows the servce logc to establsh a COB assocaton toward a gven end user. SUPPORT OF MULTPLE SESSONS n the BN archtecture, for a sngle servce nstance a sngle sesson comprses all the B-SDN connectons nvolved n the servce. Ths means that a sngle B-SSP node controls the whole set of B-SDN connectons. Ths soluton gves rse to neffcent resource utlzaton, especally n multparty servces. The problem s that a connecton between two remote users must always be routed through the controllng B-SSP node. A more effcent soluton allows more than one sesson to be nvolved n a servce nstance. Ths means that the connectons composng the servce confguraton are controlled by dfferent B-SSPs. The B-SSPs can be selected to mnmze these patnl w" s peforned by the TNA servce logc, as wll bk descrbed later. At the B-SSF level a new capablty needs to be ntroduced to let the servce logc actvate a sesson n the B-SCF+B-SSF drecton. The Create Sesson nfo flow allows the servce logc to start a new N sesson n a B-SSP that s not already nvolved n the servce nstance (Table 1). TNA SERVCE LOGC FUNCTONALTY The scope of ths secton s the descrpton of the TNA servce archtecture for BS and ts nteracton wth the BN. A TNA-based computatonal model s proposed; then attenton s focused on the ntenvorkng object (wo), whch s the core of the BN/TNA nteracton. THE TNA-BASED COMPUTATONAL MODEL The TNA-based computatonal model of the BN-TNA archtecture s reported n Fg. 6, whch shows the servce components and ther nterfaces and relatonshps. A practcal example wll be shown later n Fg. 10. The TNA COS replace the tradtonal N servce logc. A basc assumpton s that each end user s represented n the SCFAU wth ts own "consumer doman" objects. On the N sde the consumer doman objects nteracts wth an TWO, whch s the core of the AU, whereas on the TNA sde they nteract wth the "retaler doman" objects. Specfcaton of the wo s one of the results of the BS project. On the TNA sde, the specfcatons of the nterface between consumer and provder, called Ret Reference Pont [14], have been followed and only slghtly enhanced when needed. n a fully TNA-complant archtecture, the user-plane connectons are provded by the TNA communcaton management archtecture (CMA), whch s a part of the network resource archtecture (NRA) [15]. n the BN/TNA archtecture the servce archtecture objects wll nteract wth the wo wthn the B-SCF to request setup of the user plane connectons to the BN enttes. n the classcal TNA servce archtecture [16] the user applcaton (UAP) objects model the dfferent applcatons n the consumer doman. The user agent (UA) objects represent the end user n the retaler doman. The provder agent (PA) represents the provder n the consumer doman and nteracts wth the UAs to allow the user to take part n servce sessons. n the retaler doman the servce sesson manager (SSM) s responsble for control of the servce sesson. The SSM logcally manages the resources needed to provde the servce, stores the overall state, and requests actual resources of the communcaton sesson objects. The servce factory (SF) creates the servce sesson components for a servce type. n the proposed BNTNA archtecture the man features of the TNA objects have been mplemented. The logc to mplement a gven servce can be splt among the UAP and the SSM. The UAP plays a key role because t can store the user-specfc nformaton wth respect to a gven servce. For example, n the vdeoconference servce that wll be descrbed later, the UAP of the user requestng the servce stores the set of conferees to nvte, the characterstcs of the connectons, and so on, and makes the cor g requests of the SSM. A new functonalty has been to the UAP: the UAP wll support connecton man handlng the requests comng from the SSM and nteractng wth the BN world 82 EEE Communcatons Magazne June 1998
! 1 BN - -- -_ 6-SCF ) --_. -* TNA Consumer doman ' Retaler doman Ret reference pont wlms: lnterworkng DS mappng servce; wo: lnterworkng object; UAP: User applcaton; SSM: Servce sesson manager; CSM: Communcaton sesson manager ~. -- - W Fgure 6. BNTNA archtecture: servce component model. - Servce sesson!! Communcaton, sesson related : through the wo. To represent ths new functonalty, n Fg. 6 the UAPCSM extends the UAP. For the sake of smplcty, the BN/TNA model does not consder ntal agent objects (always assumng an exstng access sesson) or user servce manager objects (the servce s entrely handled by the SSM). Most of the nterfaces offered by the servce components n Fg. 6 are complant subsets of the correspondng nterfaces defned n the TNA archtecture. Later we wll focus on what has been added or enhanced n the BNENA context. TNA SERVCE SESSON GRAPH AND MAPPNG ONTO BN SESSONS The servce sesson graph (SSG) s the TNA object model that can be used to store the overall state of a servce nstance. t records the partes nvolved, the network resources used, and ther relatonshps. The objects of the SSG can be used as parameters of the methods defned for the Ret Reference Pont. The TNA COS request the addcton and removal of partes and connectons n terms of SSG objects. The SSG s composed of two abstract classes, the sesson member class and the sesson relatonshp class. The party class s a subclass of the sesson member class; aparty object nstance represents an end user nvolved n a servce. The resource class models a source of support for the executon of a servce, such as a servce subscrpton fle, conference brdge, or vdeo server. The stream bndng class s a subclass of the sesson relatonshp class; a stream bndng object nstance represents a logcal relatonshp between sesson member objects and can be composed of one or more stream flow connectons, whch represent the data flows (e.g., audo and vdeo). The control SR allows enhanced control to be per- formed on the servce sesson object, supportng mechansms for negotaton and votng. Usng the multple-sesson feature, a servce nstance can be realzed by means of several sessons n dfferent B-SSPs. n the BN/TNA archtecture the SSG represents a centralzed vew whch allows the BN sesson vews to be coordnated. The man elements of the TNA SSG are represented n Fg. 7, whch also reports the BN sesson model to allow a comparson. An example of the mappng of a TNA SSG nto BN sessons s shown n Fg. 8. n ths very smple servce scenaro user A s connected wth audo and vdeo connectons wth users B and C. Users A and B are connected to SSPl and user C to SSP2. n the TNA SSG the three partes and two stream bndng objects are clearly shown. TNA party B s mapped n the two BN sessons, whle each TNA stream bndng s mapped n two BN bearer connectons (one for audo, one for vdeo). n the BN sesson the bearer-unrelated connectons can be notced, whch have no correspondence n the TNA SSG. n fact, the bearer-unrelated connectons allow the TNA servce logc to nteract wth the end user by means of the BN-based US. THE NTERWORKNG OBJECT The wo represents the core of the AdU, performng the nterworkng between the BN functonal enttes and the TNA COS. On the TNA sde, the wo nteracts wth the TNA UAP objects. As shown n Fg. 6, nterfaces -wo-uap-ssm and -wo-uap-csm are supported by the wo, and nterfaces -uap-ssm-wo and -uap-csm-wo are supported by the UAPs. These nterfaces have been defned usng the TNA Object Defnton Language (ODL) [17]. The methods on ths EEE Communcatons Magazne June 1998 83
Fgure 7. Nsesson and TNA SSG models.. nterface allows the wo to request actons of the TNA objects on behalf of the real users (e.g., to start a servce nstance or modfy the servce confguraton) and to report the results of actons performed n the BN doman. The UAP s able to request the wo to nteract wth the real users (usng the facltes provded by the BN) and to set up the requred transport connectons. On the BN sde, the wo wll nteract wth a smplfed B- SCF that wll handle the dalogue wth the B-SSFs, termnatng the B-NAP protocol. For the servces handled by the TNA servce logc, the B-SCF wll not make autonomous decsons, relayng all B-NAP messages to the wo. n order to perform the mappng between the BN and TNA paradgms, the wo must access and/or store some nformaton related to the mappng between elements n the two dfferent domans. For example, the wo must be able to assocate a TNA user D wth an BN callng party number provded n the B-NAP Servce Request message. A specfc CO has been defned, called the nterworkng DS Mappng Servce (wms), whch has been located n the AU (consumer doman). n a real-world mplementaton, ths CO should belong to the retaler doman. As another example, the wo has the task of correctly dstrbutng the B-NAP messages to the dfferent sessons n the TNA + BN drecton and to nvoke the dfferent TNA UAP objects n the opposte drecton. Therefore, for each servce nstance the wo wll keep track of the composton of the BN sessons TNASSG and wll store the mappng between TNA users and BN party objects, as @Stream well as the mappng between the TNA stream bndng and BN bearer connectons. whch n the pure TNA archtecture s supported by the communcaton sesson manager object (CSM) n the network resource archtecture, s now supported by the extended UAPs. Ths nterface provdes operatons to establsh flow connectons. These operatons are mapped by the UAP objects nto nvocatons of sutable methods on the wo object. The UAPs are able to nteract wth the SSM objects to notfy them of the state of the connectons when alerted by the wo. The UAF emulates the CSM behavor n the nteracton wth the SSM, nvokng a method supported by the -Notfy nterface. THE BROADBAND VDEOCONFERENCE SERVCE N THE BS TESTBED The BS project has realzed the proposed archtecture n a testbed runnng on a LAN. Ths secton gves an overvew of the archtecture of the testbed, descrbng the equpment and A \- SUPPORT OF CONNECTON ANAGEMENT BY THE USER APPLCATON OBJECTS As n the classcal TNA archtecture, the nterface -sessonnotfy (Fg. 6) allows the SSM to notfy a requester or partcpant n a stream bndng of the state of stream bndng operatons. The UAP objects are extended to support requests to set up the connectons comng from the TNA SSM objects. The nterface -ComSctrl, H Fgure 8. Mappng between TNA SSG and Nsessons. 84 EEE Communcatons Magazne * June 1998
TNA retaler doman COS DPE (CORBA) based TNA Ret Ref pont -: DPE (CORBA) based j SSF-SCF nterface hternal (SDT-based) gf-ssf nterface NN nterface \ Not mplemented wthn BS....-..- -..~. Fgure 9. Archtecture of the testbed mplementaton. software tools used. Only the control aspects have been consdered n the BS testbed. Fgure 9 shows the archtecture of the testbed mplementaton. A broadband vdeoconference (B-VC) servce logc has been defned, usng as a gudelne the methods and event traces contaned n the draft TNA specfcatons for the TNA Ret Reference Pont [14]. On the TNA sde, the ONA Technologes OrbxWeb tool whch mplements the Common Object Request Broker Archtecture (CORBA) 2.0 specfcatons has been used. The OrbxWeb allows Java code to be wrtten to mplement the methods defned n a CORBA nterface Defnton Language (DL) nterface. n order to mplement the TNA servce archtecture, the object nterfaces have been defned usng CORBA DL translatng the TNA specfcatons wrtten n ODL. On the BN sde, the B-NAP has been mplemented accordng to the NSGNA project specfcatons addng the enhancements descrbed n the prevous secton. t s worth notng that the B-SSF/B-SCF nterface has been realzed on a CORBA platform mappng the Abstract Syntax Notaton v. 1 (ASN.l) specfcaton nto DL. n partcular, each B-NAP message on the B-SSF/B-SCF has been mapped nto a specfc method n the correspondng CORBA-based nterface. The CORBA protocols replace the full SS7 protocol stack that would be used to transport the B-NAP. Ths soluton, whch has been adopted manly for ease of mplementaton, s nterestng n a more general context, snce the ntroducton of the dstrbuted platform envronment nto the exstng telecommuncaton network s under consderaton by network operators. The functonalty of the B-SSF, B-CCF, and B-CUSF have been descrbed wth the Specfcaton and Descrpton Language (SDL) [18] and mplemented usng the Telelogc SDT tool. At the UN1 a sutable subset of the Recommendatons for pont-to-pont (Q.2931), pont-to-multpont (Q.2971), and Generc Functonal Protocol (Q.2932) has been mplemented, also usng the SDT tool. The protocol state machnes for the user and network sdes of UN1 have been realzed. These machnes send and process the sgnalng messages on the UN1 and offer a prmtve-based nterface toward the swtch call handlng processes (l, Fg. 9). A call handler has been developed wthn the B-SSP to control a set of UNs. Ths call handler controls the pont-to-pont calls, pont-to-multpont calls, and call-unrelated assocaton, and ntegrates the BCSM and BCUSM functonalty to allow the nteracton wth BN, actng as the B-CCF. An nternal nterface toward the SSF has been defned (2). The B-SSF realzes the sesson model and dalogues wth the B-SCF (3). The physcal groupng of enttes s shown by the dashed lne n Fg. 9. The B-SSP enttes (B-SSF, B-CCF, B-CUSF, and UN1 protocol machne - network sde) are grouped n a sngle applcaton runnng on a Sparcstaton 20. The mplementaton of the CORBA-based B-SSF nterface runs on the same workstaton. The TNA COS run on another workstaton. A set of standalone applcatons mplement the user termnals. These applcatons run on dfferent workstatons; more than one termnal can be mapped n a sngle workstaton. The UN1 messages among these applcatons and the B- SSP workstaton are formatted accordng to the TU-T Recommendatons and are exchanged usng socket nterfaces EEE Communcatons Magazne June 1998 85
TNA the UNs and on the nternal nterfaces wthn the B-SSP applcaton. These Java applcatons can run on external workstatons or PCs. Fgure O. BNTNA computatonal model. an example of the archtecture. provded by the UNX operatng system. The nternal nterfaces l and 2 wthn the B-SSP applcaton are based on the exchange of SDL sgnals. The 3 and 4 nterfaces are CORBA-based. A set of GU applcatons has been developed n Java to allow basc management operatons (.e., setup of the testbed envronment), emulaton of termnal operatons (servce request, call setup), and real-tme vsualzaton of messages on A B-VC SERVCE EXAMPLE The computatonal model used to manage a B- VC servce nstance nvolvng three users s shown n Fg. 10. Users A and B are connected to the same B-SSP, user C to a dfferent B-SSP. n the TNA servce logc, a UA, a provder agent (PA), and a UAP object are nstantated for each user. Each user s represented by a correspondng UAP n the consumer doman and by a UA that stores the user profle n the retaler doman. n the user profle there s also nformaton related to the BN context such as the dentfer of the B-SSF to whch the user s connected and the BN number of the termnal at whch the user wants to be called. When a user requests a servce n the BN, the B-NAP Servce Request operaton s ssued from the B-SSF to the B-SCF. The wo provdes for the creaton of the correspondng UAP object, and sends t the start-servce method. The nstantated UAP stores the nformaton about the vdeoconference confguraton to be realzed and nvokes the methods n the SSM as needed to establsh and confgure the servce. The SSM nteracts wth the UAPPJM to request the connectons that physcally realze a stream bndng, by means of setup-lflowconnecton method. The UAP~~M nvokes the add-bearer method n the wo, whch n turn translates t nto B-NAP operatons (e.g., Add Bearer to Sesson, Request Report SSM Change). \.--! UAP: Uter applcaton, PA Provder agrnt; 5SM Servce wwon managcr, UTS Usrt-o-servce nfot maton, ST gure 1 1. UserA (nvter) nvtes user C (nvtee) to jon a servce sesson. 86 EEE Communcatons Magazne 0 June 1998
Durng the actve phase of the servce, a user s able to nvte another user to jon n a servce sesson. Ths scenaro s shown n Fg. 11 by means of an event trace. The nvted user can accept the nvtaton and mmedately jon the servce sesson. The precondtons for ths procedure are: The nvtee user C and nvter user A are connected to dfferent SSPs. An BN sesson related to the specfc servce nstance s not already nstantated n the B-SSP at whch the nvtee user s connected. Users A and B are already actve n the servce. The man steps to nvte a user are: User A sends a message to the TNA servce logc by means of the User Servce nteracton to nvte user C. The wo nvokes the method nvte-user n the nvter's UAP. The UAP requests the add party operaton of the SSM, usng SSG objects as parameters. The TNA servce logc contacts the nvtee's UA and sends an nvtaton usng the -nameduahvte nterface. The UA forwards the nvtaton usng the qanvte nterface of the PA, addng to the parameters the SSF dentfer and BN party number to be called. The PA sends the nvtaton to the nvtee's UAP. The UAP sends a method to the wo to alert the user by means of the BN capabltes. The wo controls the state of the B-SSP at whch the nvtee s connected. f no sesson related to the servce nstance s nstantated, the wo creates and ntalzes t, sendng the needed B-NAP messages. A COB1 assocaton toward the nvtee s establshed and allows the nvtaton to be relayed to the user termnal. CONCLUSONS Ths artcle proposes an approach for the provson of ntellgence n broadband networks, as needed to support multmeda servce. The approach s based on the evoluton of the ntellgent broadband network toward an open dstrbuted processng archtecture such as TNA. The proposed archtecture has been mplemented n a testbed envronment n the framework of the BS project. As a frst concluson the BN, as proposed by the NSGNA ACTS project, appears even more nterestng because t has been proven to be futureproof. n fact, the largest part of the nvestment n the deployment of an BN s probably represented by the B-SSP nodes, whch have been successfully reused n a more advanced context. The second concluson concerns the evoluton toward TNA. A vable soluton such as that proposed here must be found to allow step-by-step ntroducton of TNA n the telecommuncaton network startng n the near future. Further work s requred to evaluate the performance of BNRNA archtecture; n fact, the response tmes for servce provsonng could be nfluenced by the overhead of the dstrbuted orocessng envronment supportng TNA. However, the applcaton of the TNA concept s lmted to handlng the logc of complex servces (e.g., vdeoconference) that could admt a setup tme on the order of few seconds. Therefore, t ' s reasonable that the DPE does not consttute a bottleneck to meet these tme requrements. ACKNOWLEDGMENTS The authors would lke to thank all the people who worked n the NSGNA project (n partcular Mchael Gepl, Deutsche Telekom, for hs contrbutons on the TNNNSGNA nterworkng ssues), as well as all the people at CoRTeL who partcpated n the BS project (especally Rossella Mossotto for her work on the TNA servce logc). REFERENCES [] A publcly avalable descrpton of the NSGNA project can be found at http://www.fokus.gmd.de/nthp/nsgna/entry.html [21 H. Hussmann and. Veners, Eds., ntellgent Broadband Networks, Wley, to be publshed June 1998. [31 Publcly avalable descrpton of the TNA-C actvtes and results avalable at http://www.tnac.com. [4] U. Herzog and T. Magendaz "ntellgent Networks and TNA - Mgraton and nterworkng ssues," /nt% Swtchng Symp., Toronto, Canada, 1997. 151 ACTS NSGNA Project delverable report on topcs requred from the 1997 Techncal Audt, Ch. 2, "lnteroperablty between NSGNA and TNA." 161 TU-T Rec. 4.1 224, "Dstrbuted Functonal Plane for ntellgent Networks CS-2." [7] G. DeZen et al., "Proposal for an n Swtchng State Model n an ntegrated N/B-SDN Scenaro," Proc. /S&N '97, May 27-29, 1997, Cernobbo (Como), taly. 181 G. Prezerakos et al., "NSGNA: A Pan-European tral for the ntellgent Broadband Network Archtecture," / E Commun. Mag., ths ssue. [91 H. Hussmann et al., "A Transnatonal N/B-SDN ntegrated Network for the Provsonng of Multmeda Servces," Proc. ECMAST '97, Mlan, taly, May 21-23, 1997. [lo] TU-T Rec. 4.2971. "B-SDN DSSZ - User-Network nterface Layer 3 Specfcaton for Pont-to-Multpont Call/Connecton Control." [ 11 TU-T Rec. 4.2722.1: "B-SDN User Part - Network Node nterface Specfcaton for Pont-to-Multpont Call/Connecton Control." [21 M. Lstant and S. Salsano, "Pont-to-Multpont Call Modellng for the ntegraton of N and B-SDN," Proc. N '97, Pars, France, Sept. 1997. [31 TU-T Rec. 4.2932.1, "B-SDN DSSZ Generc Functonal Protocol: Core Functons," 1996. [41 "Ttk Ret Reference Pont (v. 1.1) - Response to a Request for Refnements and Solutons," draft. [15] "TNA Network Resource Archtecture Verson 3.0," Feb. 1997 [ 61 "Servce Archtecture Verson 5.0," TNA-C, June 1997. [17] T/NA Object Defnton Language Manual Verson 2.3, July 1996 [81 TU-T Rec. 2.100. "SDL Methodology Gudelnes," Appendces and 11. BOGRAPHES MARCO LSTANT [M (marco@nfocom.ng.unromal.t) receved hs Dr. Eng. degree n electroncs engneerng from the Unversta d Roma "La Sapenza" n 1980. He joned the Fondazone Ugo Bordon n 1981, where he was leader of the TLC network archtecture group untl 1991. n November 1991 joned the NFOCOM Dept. of La Sapenza, where he s assocate professor n swtchng systems. Snce 1994, he also collaborates wth the Electronc Department of the Unversty of Rome "Tor Vergata" where he holds courses n telecommuncaton networks. He has partcpated n several nternatonal research projects sponsorzed by EEC and ESA and s the author of papers publshed n the most mportant techncal journals and conferences n the area of telecommuncaton networks. Hs current research nterests focus on ATM networks wth partcular regard to traffc control and sgnalng aspects. He has represented the talan PTT admnstraton n nternatonal standardzaton organzatons (TU, ETS). STEFAN0 SALSANO (salsano@cortel.t) receved hs Dr. ng. degree n electronc engneerng from the Unversty of Rome "Tor Vergata" n 1994. Snce then he has been wth CoRTeL, a research nsttute n telecommuncatons, as a scholarshp holder. He has now completed hs Ph.D. course at the NFOCOM Department, Unversty of Rome "La Sapenza," and s watng for the fnal examnaton. n 1997 he was employed by CoRTeL. Hs research nterests nclude archtectures and sgnalng protocols for broadband networks, focusng on the ntegraton of B-SDN wth N, and ntegraton of P and ATM. He has partcpated n the EC ACTS projects NSGNA and ELSA. EEE Communcatons Magazne June 1998 91