18. VDE/ITG Fachtagung Mobilkommunikation 15. - 16. May 2013 - Osnabrück, Germany
Virtualization of VoIP Application Servers for Implementation of Private Unified Communication Services via LTE Claas Felix Beyersdorf, Diederich Wermser, Daniel Hartmann (Ostfalia University of Applied Sciences, Research Group IP-based Communication Systems, Salzdahlumer Str. 46/48, D-38302 Wolfenbüttel). Xing Cao (IANT Applied NGN Technologies GmbH). Contact:
[email protected]
Abstract Today’s LTE networks with their Evolved Packet Core architecture (EPC) provide an excellent platform for transparent integration of mobile User Agents (UA) into corporate VoIP and Unified Communication (UC) environments. Voice over LTE (VoLTE) can either be controlled by IP-Multimedia Subsystem (IMS) run by mobile network operators or by external Application Servers (AS) run by other parties. This paper introduces first approaches and research goals of an R&D project focussing on solutions for implementation of corporate VoIP and UC services by external Application Servers. Virtualization of Application Servers for real-time communication services is a particular focus of the considerations.
1
Introduction
Large organisations like companies intend to have private communication networks or services, which seamlessly include all employees, wherever they geographically are and whatever communication device they just use. Beyond store-and-forward services like e-mail this is also expected for Real-TimeCommunication (RTC) like voice or video services. As long as only circuit switched mobile networks like GSM could meet the requirements of RTC, Closed User Group services were offered by respective mobile network operators. However, these services only offer a set of standard features limited by supplementary services or IN-features run by the operator. LTE with EPC as core-network for the first time enables RTC over IP in mobile WANs and thus the possibility to have full feature-transparency for corporate UC Services to roaming mobile devices.
2
Seamless Integration of Mobile Users to Company RTC
2.1
Traditional FMC becomes obsolete
The traditional solution to achieve integration of mobile users into company RTC services when using circuit switched mobile networks like GSM are known as Fixed Mobile Convergence (FMC) [2]. For a caller the current whereabouts of an FMC client and its mobile number of the appropriate public mobile network is not visible. Figure 2 illustrates the handling of a mobile originated call (MO) in FMC, when only circuit switched connectivity is provided by the mobile network. Figure 3 shows the handling of an MO call applicable, when the mobile network offers non-RTC capable IPconnectivity like GPRS in parallel to circuit switched RTC. In both scenarios the FMC controller inside the corporate network establishes the required connections.
Figure 11: LTE / EPC C with IMS an nd Private Ap pplication Seerver Controllling QoS Parrameters (Sim mplified) Scenario 1 does not alllow for featuree transparencyy, the FMC useer is limited too the CS featture set offereed by his publicc mobile netw work operator. In contrast inn scenario 2 addvanced preseence services or CTI-integrration with IT-aapplications off the respectiv ve company caan be provided,, as the entiree signalling fo or call control with the comppanies RTC serrver is done over IP.
2.2
RTC seervices baseed on EPC C/LTE
Figu ure 1 gives a simplified vview on LTE//EPC with netw work elementss being particuularly relevantt for RTC. Diffferent from prrevious mobilee network tecchnologies EPC C/LTE works All-IP, i.e. aalso RTC serrvices are baseed on IP. VoIP P in LTE is frrequently called VoLTE [19]. Quaality of Servicee (QoS) param meters as welll as Multileveel Precedence and Pre--emption Meechanisms (eM MLPP) can be controlled thhrough the Policy P and Charging Rules Function F (PCR RF) either by an a IMS of the network n operator or througgh the Rx Intterface using the Diameteer-Protocol byy external Application A Serv vers.
Figure 2:: Pure CS based FMC Sollution
Tablle 1 lists the QoS classes aas defined in 3GPP TS 23.2 203 [7], the eMLPP e mechhanisms are defined d in 3GP PP TS 22.067 [10].
ass Identifierss [7] Table 1: QoS Cla
Figure 33: FMC Solu ution with CS C RTC and non RTC-cap pable IP Conn nectivity in Mobile M Netwoork
Figure 4: SiipXecs [3]as aan SSOA Exa ample, modiffied from [1]
A compaany aiming at seamless inteegration of m mobile users intoo its internal RTC services can either iinterconnect tthese servicess with the on nes offered byy the LTE operrator based onn his IMS usiing an approppriate Session B Boarder Controller (SBC)) or use the LTE /EPC as transparent mobile m IP-Netw work throughh SGi Interface with the opttion to contro ol QoS param meters using the Rx reference point. Seen from m the viewpooint of featuree transparencyy for the internnal RTC servvices, the lattter alternativee has obvious aadvantages. On O the other hand h requirem ments for high aavailability off mobile RTC C services now w are to be fulffilled by the coompany’s RTC C servers.
2.3
P Private AS for RTC Services S
Internal R RTC Services, replacing traditional onn-site PBX sysstems, are moore and moree offered as ccloud services bby specializedd providers. These prooviders have to run RTC services for m many customerrs on their serrver infrastruccture and are ffaced to high requirementss with respecct to availabbility. There aree two basic architecture a alternatives a too implement ssuch a scenariio:
I a multiOne Mullti-tenant impllementation. In tenancy environmentt, multiple customers share thee same applicaation softwaree. Virtualizzation with (opptionally) an individual application software fo for each custom mer.
As far as known n by the auth thors, IMS im mplements closed user group ps for corporaate customers by multitenaancy. wever, for priv vate AS to proovide RTC Serrvices virHow tualiisation has a number of aadvantages. Application A softw ware not deveeloped for muulti-tenancy can c be utilized d and moreov ver additionall software co omponents for customer c individual servicee features can n easily be integ grated. Major requiremen nts for RTC sserver solutio ons in this conttext are scalab bility as well as redundanccy of main com mponents in orrder to achievve high availaability and load d balancing. Moreover M oppen standard interfaces like SIP, XMPP an nd REST to al allow functional integration with commo on enterprise applications like l CRM or ERP E are needed d.
3
A Aspects of o Virtualiized RTC C S Servers
Running services like web w or e-maill in virtualizedd environmennts is nothing special nowaadays. But exppanding the sspectrum of virtualized v serrvices to real--time applicatioons like VoIIP or unified d communicaations (UC) in general reqquires a careeful investigaation, which wiill be discussed in this chaptter. When it ccomes to virtuualizing of Vo oIP systems, a particular nootice has to be b taken of media-related m processes. T The signalling on the other hand is relattively uncriticall, since SIP has h its own timingt and eerrorhandling [13].
Assumingg that CPU annd RAM resou urces of a phyysical server arre properly diimensioned, the t hypervisoor for the virtuaal machines (V VM) can be eaasily configurred to provide tthe appropriatte CPU and RAM R resourcees for high priorrity VMs at anny time.
I/O activities are more problem matic (Figure 5). A media related r VoIP process p of an SSOA normaally has to transsfer 50 packeets per secondd of RTP dataa for each direcction. At bestt, those packeets should be sent in an isochronous interval; the netwo work interface controller (NIC C) has to be exactly e triggerred at each 20ms without any a jitter. Sincce the NIC actts as a virtual switch on a viirtualized macchine, an outg tgoing RTP sttream can suffe fer from high jitter, if other V VMs heavily access the same NIC simultaneously. Usiing several NICs N along with h pass-through h mechanismss can ease this problem by allowing a a hig gh priority VM M to access on ne specific NIC C exclusively. Asid de the presencce informationn, the call-stattes and the audiio data for In nteractive Voiice Response (IVR) or Mussic on Hold (MoH), ( the aactual registraations and call detail recordss (CDR) get sstored on the hard disc drives (HDD) off the physicall server, as well. w With Ds having the slowest accesss times in a whole w sysHDD tem,, it has to bee examined, iif UC servicees like the Pressence Service, IVR or MoH H get affected in i a heavy load d scenario caussed by lots off VMs with dissc access. With h further noticce on high avaailability, the HA of the publlic operator’s architecture now has to be implemen nted by the private SSOA’ss operator. The modular struccture of an SSOA allows eeasy distribution of the resp pective and op ptionally reduundant processes across the physical hard dware of a viirtualized env vironment. To meet m the demaanded HA, noo redundant UC U componentts (i.e. databasses) must be ddistributed ontto the very same physical harrdware. Furthhermore, it hass to be investigated, if the potentially hiigher granularrity serves or liimits the inteended scalabillity and overaall performan nce, in particu ular the syncchronization processes, whicch cause addittional networkk traffic.
Otheer planned exaaminations:
S Figure 5:: I/O is Criticcal for RTC Services
OA in paralleel to other non-critical An SSO services like CRM or web on the saame physical host.
A “competing g” on the More than one SSOA same phy ysical host.
Distributtion of seveeral virtualizeed SSOA across a wide range off physical hosts.
4
C Clients foor Privatee Mobile R RTC Servvices
Many coompanies aim m for deskttop virtualizaation, which is one way too cope with the challengees of BYOD (B Bring Your Ow wn Device), as a asked for bby today’s em mployees. Usabbility of softp phones in the context of deesktop-virtualiization needs additional coonsideration. F For smart phoones as domin nant client devvices for mobille RTC services, desktop viirtualization s eems not to maake sense. Howeverr, WebRTC [12] as extensio on for HTML L5 offers an exxcellent portabble thin clientt solution for RTC services oon smart phonnes to interactt with private RTC Applicatiion Servers based b on QoS S-controlled ttransparent IP-transport in LTE/EPC L mob bile networks.. IMS venddors like Ericssson have alreeady announcced to support W WebRTC cliennts for IMS-baased real-timee services [20]. Figure 6 and Figure 7 illustrate ro outes of signaalling and mediia for a simpple two-party call, when uusing SSOA (F Figure 6) resppectively a Back-to-Back-U UserAgent arcchitecture for the RTC AS (Figure ( 7).
Figure 6:: WebRTC prrotocol stack with SSOA
Figure 7:: WebRTC prrotocol stack with B2BUA A
5
Outlook
Thiss paper consid ders a varietyy of aspects relevant r to enab ble seamless access a to corpporate RTC seervices for mob bile users, baseed on LTE/EPPC mobile netw works. Furtther research activities a willl focus on virttualization of RTC R Applicatiion Servers an and in particu ular implemen ntation of testss, that proof kkeeping of QoS parameters for media serrvices under eextreme load situations in th he virtualizatio on environmennt. As long l as LTE radio networkss have insuffiicient coverag ge, Voice Call Continuity (V VCC) has to be b applied. It en nables seamleess handoverss between VoL LTE (controllled by an IMS) and GSM--based circuitt switched voicce transmission n outside the L LTE coveragee [11]. Potentiial solutions offering o an eqquivalent exteension beyond d the LTE co overage need to be addresssed when exteernal corporatte RTC appliication serverrs will be used d. Traditional FMC solutionns as described in chapter 2.1 2 could perhaps contributee to this aspecct. Also o, usability of WebRTC for mobile RTC Clients on smarrt phones in interaction i wiith external RTC R applicatio on servers neeeds more thoroough considerration.
6
References
[1] Schumacher, Jan; Wermser, Diederich: VoIPTK-Anlagen auf Basis von Open Source. BerlinOffenbach: VDE-Verlag, ntz 7-8, Nov. 2009. [2] Shneyderman, Alex; Casati, Alessio: Fixed Mobile Convergence. McGraw-Hill, 2008. [3] Picher, Michael W.: Building Enterprise Ready Telephony Systems with sipXecs 4.0. Packt Publishing, 2009. [4] SIPfoundry open source community. http://www.sipfoundry.org, April 2013. [5] Hartmann, Daniel; Stephan, Mark; Cao, Xing et al.: Initial Development of a SIP-/RTP-based Core Network for the TETRA Mobile Radio System aiming at Transparent Availability of its Features in LTE. Osnabrück: 16. ITGFachtagung Mobilkommunikation, 2011. [6] Pankratz, René; Hartmann, Daniel; Wermser, Diederich: Spezielle Anforderungen an Virtualisierungslösungen für Software-basierte VoIPPBX. Leipzip, HfTL Science Days, 2010. [7] 3GPP TS 23.203: Policy and charging control architecture. Release V12.0.0, 2013-03. [8] 3GPP TS 29.213: Policy and charging control signalling flows and Quality of Service (QoS) parameter mapping. Release V11.6.0, 2013-03. [9] 3GPP TS 22.011: Service accessibility. Release V12.0.0, 2013-03. [10] 3GPP TS 22.067: enhanced Multi Level Precedence and Pre-emption service (eMLPP). Release V11.0.0, 2011-09. [11] 3GPP TS 23.206: Voice Call Continuity (VCC) between Circuit Switched (CS) and IP Multimedia Subsystem (IMS). Release V7.5.0, 2007-12. [12] Web Real-Time Communication. http://www.webrtc.org/, April 2013. [13] Trick, Ulrich; Weber, Frank: SIP, TCP/IP und Telekommunikationsnetze. 4. Auflage, München: Oldenbourg Verlag, 2009. [14] Poikselkä, Mikka et al.: The IMS. West Sussex: John Wiley & Sons Ltd, Reprint of 2004. [15] Dahlman, Erik et al.: 3G Evolution. 2nd Edition, Burlington: Academic Press, 2008. [16] Lescuyer, Pierre; Lucidarme, Thierry: Evolved packet Systems (EPS). West Sussex: John Wiley & Sons Ltd, 2008. [17] Agbinya, Johnson: IP Communications and Services for NGN. Boca Raton: CRC Press, 2010. [18] Olsson, Magnus et al.: SAE and the Evolved Packet Core. Burlington: Academic Press, 2009. [19] Ericsson White Paper: Voice over LTE. http://www.ericsson.com/res/docs/whitepapers/v oice-over-lte.pdf, December 2010.
[20] Gabriel, Caroline: Ericsson pushes WebRTC beyond the phone. http://www.rethinkwireless.com/2013/01/10/ericsson-pusheswebrtc-beyond-phone.htm , 2013.
7 AS B2BUA BYOD CRM CSCF eMLPP EPC ERP FMC GPRS GSM HA HSS IMS IN IP IVR LTE MO MoH NGN NIC PBX PCRF PDN PSTN QoS RAN REST RTC RTCP RTP SAE SBC SIP SPR SRVCC SSOA UA UE UC VM VPN VoIP VoLTE WAN XMPP
Abbreviations Application Server Back-to-Back User Agent Bring Your Own Device Customer-RelationshipManagement Call Session Control Function enhanced Multi-Level Precedence and Pre-emption Evolved Packet Core Enterprise-Resource-Planning Fixed Mobile Convergence General Packet Radio Service Global System for Mobile Communications High Availability Home Subscriber Server IP Multimedia Subsystem Intelligent Network Internet Protocol Interactive Voice Response Long Term Evolution Mobile Originated Music on Hold Next Generation Network Network Interface Controller Private Branch Exchange Policy and Charging Rules Function Public Data Network Public Switched Telephone Network Quality of Service Radio Access Network Representational State Transfer Realtime Communication Realtime Transport Control Protocol Realtime Transport Protocol System Architecture Evolution Session Border Controller Session Initiation Protocol Subscriber Profile Repository Single Radio Voice Call Continuity SIP Service Orientated Architecture User Agent User Equipment Unified Communication Virtual Machine Virtual Private Network Voice over IP Voice over LTE Wide Area Network Extensible Messaging and Presence Protocol
