Next Generation Mobile Internet – Network and Service Platform Die Nächste Generation Des Mobilen Internet – Netz- Und Serviceplattform

Schwerpunktthema

it 6/2008

Next Generation Mobile Internet – Network and Service Platform Die nächste Generation des mobilen Internet – Netz- und Serviceplattform

Wolfgang Kellerer, Jörg Widmer, Hendrik Berndt, DOCOMO Communications Laboratories Europe GmbH, München

Summary The Internet has become the main network tech- unserer Gesellschaft und hat sich damit zu der Schlüsseltech- nology supporting communications and Web services in all nologie der vernetzten Welt entwickelt. Damit das Internet areas of our society. In order to perform this role efﬁ- dieser Rolle bei gesteigerten Anforderungen weiterhin gerecht ciently, a fundamental redesign of the Internet architecture werden kann, wird derzeit seine grundlegende Überarbeitung is being discussed. In particular, mobile devices and wire- diskutiert. In Zukunft werden insbesondere mobile Endgeräte less access networks will constitute an important part of the und drahtlose Zugangsnetze einen erheblichen Anteil an der Internet infrastructure. Based on a general discussion of re- Internet Infrastruktur haben. Daher geht dieser Artikel aus- quirements, this article focuses on the challenges of a next gehend von einer generellen Betrachtung der Anforderungen generation mobile Internet and discusses research approaches speziell auf die Herausforderungen eines Next Generation Mo- for mobility, addressing, heterogeneous access, and service bile Internet ein und diskutiert Forschungsansätze für Mobilität, platforms. Zusammenfassung Das Internet un- Adressierung, heterogene Zugangsnetze und Diensteplattfor- terstützt Kommunikation und Web Dienste in allen Bereichen men.

KEYWORDS C.2.1 [Computer Systems Organization: Computer Communication Networks: Network Architecture and Design Future]; future Internet, mobile Internet, virtualization, overlay networks

1 Introduction ation Network (NGN) in fixed in- originating from its basic design The Internet has become the com- frastructures and the All IP Network principles. Targeted as a network for munications backbone of our soci- in mobile systems, the Internet Pro- robust data transport over a fixed ety in all respects. When using the tocol (IP) suite is expected to play infrastructure, its suitability for to- term Internet, we usually do not the dominant role in networking. day’s variety of services including limit ourselves to its core set of pro- With our theme on mobile Internet real-time traffic and mission crit- tocols such as TCP/IP but refer to in this article we cover the aspects of ical applications is limited. To fix itswholeofferofservicesandap- a next generation Internet encom- some of the problems, plenty ad- plications provided by a plethora passing the particular requirements ditional protocols have been pro- of protocols on all protocol layers. of mobile and wireless systems. posed, complementing IP in such Moreover, the Internet has stretched The importance of the Internet areas as security, mobility, and out from the fixed line infrastruc- can also be observed in the area quality of service (QoS). However, ture to cellular networks. There, of service delivery platforms, where none of these proposals have seen access to the Internet was offered the IP Multimedia System (IMS) widespread deployment in the In- as an add-on for second generation becomes more and more import- ternet. For a number of reasons, mobile networks. Today, the Inter- ant as a service platform for packet adding functionality to the current net protocols are an integral part of switched services for fixed and mo- Internet has become almost im- third generation mobile communi- bile networks. possible, leading to an ossification cation systems such as UMTS. With Despite its popularity, the Inter- of the Internet architecture. Thus, the emergence of the Next Gener- net suffers from several deficiencies recently initiatives have started to

it – Information Technology 50 (2008) 6 / DOI 10.1524/itit.2008.0505 © Oldenbourg Wissenschaftsverlag 345 Schwerpunktthema

reconsider the Internet design as ture. Yet, this is not reflected in Among the research undertaken such. the Internet design where both iden- to reconsider the Internet design, The most pressing problems to tity and location are designated by two directions can be observed. The be solved for the future Internet are IP addresses. This creates prob- clean slate approach tries to come summarized in the following para- lems when a host moves between up with a new Internet architecture graphs [1]. They can be grouped networks, is attached to multiple from scratch, whereas the evolu- by short term, mid term and long networks for multi-homing, or in tionary approach builds on step by term problems according to their case it has multiple service-specific step improvements, starting from urgency [2]. addresses. the existing design. Both should not The most obvious annoyance of Another problem of the Inter- be regarded as exclusive but rather the Internet that has to be solved on net to be solved in the medium complement each other. With over- a short term basis is probably Spam, term is the layered protocol refer- lays and virtualization, we describe followed by security as the biggest ence model itself, which is one of the tools for the implementation of so- imminent problem facing the Inter- main reasons why the other prob- lutions for both approaches. net. Today’s security infringements lems remain unsolved. Due to many The remainder of this article such as viruses, phishing, denial-of- short sighted fixes but also due to its is structured as follows. First, we service attacks, etc. largely diminish huge success as the platform for net- highlight selected mobile operator the users’ trust in the network and working, the architecture has ossi- related solution concepts to deal prevent critical applications from fied and lost all necessary flexibility. with the above requirements. In being deployed. A further problem Finally, while the problem of ad- Section 3 and Section 4, we describe is the presence of middleboxes such dress space depletion is addressed by mechanisms such as overlays, virtu- as firewalls or NATs, some of them IPv6, its widespread deployment is alization and cross-layer design as deployed to improve network secu- lagging behind. Enhancing the ad- tools to implement solutions in the rity. They do not fit well with the dress space through IPv6 or any core network and in the wireless original concept of end-to-end con- other suitable solution thus remains access network, respectively. Service nectivity and cause enormous prob- a problem to be solved in the long platform related aspects of a next lems for application developers. term. generation Internet are discussed in Medium term problems relate As a very general tendency, one Section 5. to QoS, management, routing, mo- can observe that the solutions to bility and the overall layered archi- those problems will move some 2 Selected Future Internet tecture itself. Despite many research intelligence back to the network, Concepts and standardization efforts the best- which is in favor of the operators to Of the general architectural prob- effort characteristic of the Internet be able to handle traffic flexibly with lems of the Internet discussed prevails. QoS is addressed by simple respect to the varying application above, some are more relevant to overprovisioning today. However, to requirements. In general, the oper- mobile operators than others. To cope with the rise in traffic volume ator expectations for a future Inter- use IP as a basis for future opera- and the requirements of emerging net target an innovation-friendly In- tor networks, specifically the aspects applications (e. g., real-time, inter- ternet that is service oriented rather of device mobility and multi-hom- active) as well as the use of net- than designed for host-to-host ing (or the use of multiple radio works with different physical layer packet forwarding, to prepare for interfaces for different wireless net- characteristics (e. g., wireless), com- unknown upcoming applications. works on the same device) need to prehensive solutions have to be de- For a mobile operator,thesame be solved. Also, addressing is an im- veloped and deployed in order to problems apply for its IP core net- portant issue, in particular if the transform the Internet from a com- work. In particular, when changing increase in the number of devices modity best-effort network to a com- the viewpoint from mainly fixed connected to an operator network mercialtelco-gradeone.Inthesame hosts to mobile hosts several chal- continues to increase. However, as way, Internet network management lenges have to receive additional long as device mobility or the use is lacking some of the functionality attention: Address management has of multiple radio interfaces are con- known from traditional telecommu- to be able to cope with a rapidly fined to the network(s) of a single nications. Further, the slow conver- increasing number of mobile ter- mobile operator, it is possible to de- gence and other deficiencies of the minals, each possibly equipped with ploy solutions without coordinating BGP protocol limit the scalability of several air interfaces of different with other operators, thus signifi- inter domain routing and thus limit QoS characteristics. Furthermore, cantly simplifying deployment hur- the business relationships between the heterogeneity of device capabil- dles compared to Internet ISPs. Internet service providers (ISPs). ities and wireless access links needs On the other hand, mobile op- Many of the Internet hosts are to be considered in the network erators have to deal with much considered to be mobile in the fu- design. higher degrees of network dynam-

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ics at the edges of the networks. Proposals for a separate flat lack any management function to Mobility solutions in the Internet, identifier space are often combined monitor or control their operation such as Mobile IP, have never been with a public/private key infrastruc- to achieve certain requirements such widely adopted, mainly because the ture to enable the authentication as cost optimality, quality of service, most widely used applications like of the sender of a packet. For ex- etc. Further, heterogeneity as a re- web browsing and e-mail do not ample, HIP [8] allows a receiver quirement of a mobile Internet is not require a static address. Better mo- to start an authenticated Diffie- supported sufficiently in current ap- bility support is a central element of Hellman exchange before accept- proaches. We briefly look into these future Internet research, but its real- ing a connection and establishing requirements in more detail. ization in production networks will state information. With this, initi- As an illustration, [3] describes depend on the emergence of appli- ating distributed denial of service an analytical framework for dis- cations that require it, such as VoIP. attacks becomes more difficult. tributed management of P2P over- A major criticism of the current lays with respect to cost optimal- Internet architecture is the overload- 3 Core Network: Overlays ity according to the total number ing of IP addresses to serve the and Virtualization of messages exchanged as a meas- function of node locator and iden- As pointed out in the introduction, ure of traffic load. It is based on tifier. The hierarchical address space a general objective of the future the concept of a hierarchical dis- of IP is instrumental for the scala- Internet is its flexibility to adapt tributed hash table (DHT), consist- bility of the Internet since it allows to changing requirements. This is ing of high capability superpeers aggregationofroutingtableinforma- in particular true for the IP core forming a DHT structure and leaf tion.However,italsoidentifiesnodes network, which suffers most from nodes (e. g., mobile phones) (Fig. 1). as being part of a specific network, the strict Internet design that pre- Such an architecture is well suited which hinders node mobility be- vents solutions to the above prob- to support mobile communication tween networks and multi-homing. lems. Therefore, overlay networks systems. Cost optimality can be Proposals such as [8; 9] break up have been applied successfully to achieved by tuning the number of this double role and use IP addresses overcome some deficiencies on the superpeers in the overlay network. only for routing purposes (if at application layer. Most prominent As illustrated in Fig. 2, the total net- all). Mapping between locator and are overlays for multicast applica- work traffic increases monotonously identifier space requires a lookup tions such as the mbone, content with the ratio of superpeers due service similar to DNS. The prob- distribution networks such as Aka- to higher maintenance traffic. At lems of multi-homing and mobility mai, application layer virtual private thesametimewehavetoprevent are thus relegated to the lookup ser- networks, and Peer-to-Peer (P2P) overloaded superpeers from causing vice which has to be performant overlay networks. system failures. Dynamically adjust- enough to support frequent changes Distributed overlay networks ing the superpeer ratio relying only of the identifier to address reso- such as P2P-based information on the partial view of the network lution entries. Some recent work lookup and delivery networks are at a single peer allows managing the takes the concept of a flat identifier very attractive as they can be de- overlay in a distributed way. space one step further by propos- ployed easily, without requiring Overlay networking concepts ing a routing protocol that does not any change of the underlying in- provide a simple and efficient way require any location information frastructure. Moreover, they are to enhance the functionality of the embedded in addresses, but is based very flexible in terms of supported underlying network, but they can- only on identifiers [6]. The routing applications, including diverse ap- not be used to address all of the mechanism is based on ideas bor- plications such as content sharing, rowed from structured Peer-to-Peer streaming, and voice over IP. It architectures (Section 3). This obvi- should be noted that overlay con- ates the need for a separate lookup cepts and in particular P2P overlay service which increases the overall concepts are originally only end sys- robustness of the network. How- tem based and not core network ever, as the authors themselves state, concepts. However, these concepts their work can only be seen as a very have an impact on the design of fu- first step to expand the design space ture core networks with respect to for future routing protocols. The their advantages regarding ease of performance and scalability com- deployment, distribution, self orga- pared to traditional Internet routing nization, and thus cost efficiency. protocols make the proposed ini- For practical operations, how- tial approach unsuitable for deploy- ever, it is a huge disadvantage of Figure 1 Hierarchical P2P overlay network ment in large scale inter-networks. overlay networks, that they usually Chordella [3].

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required physical resources, e. g., by powering off equipment when it is not needed [15]. Network virtualization may be combined with virtualization of storage and processing resources which is very appealing, for example, for the design of efﬁcient content distribution networks.

4 Access Networks In contrast to the urgent requirements for new architectures for the future Internet, wireless access net- Figure 2 Overlay network cost optimization: determining the optimum superpeer ratio as a function of the trade-off between minimizing total network traffic and individual superpeer load (highest works have seen a steady evolution observable load factor). of existing technologies and emergence of new wireless standards, aforementioned problems. For ex- architectures are permanently run mainly to support higher data rates. ample, an overlay can attempt to side-by-side (along with the current In addition to well established wire- work around parts of the Internet Internet architecture). less access technologies, WiMAX suffering from a denial of service Network infrastructure pro- may play a significant role to fill attack, but it cannot prevent or viders may thus give much greater the gap between cellular networks mitigate such attacks on the un- flexibility to service providers for and Wireless LAN in terms of cov- derlay. At the same time, proposals the creation of services that are erage and supported data rates. An to solve such problems directly by not possible with today’s Internet important trend is the integration changing the network architecture architecture [12]. For this vision of many of these wireless tech- were not deployed by operators in to become true, it is necessary to nologies in a single mobile device. production networks, often due to develop tools and business models This has implications on future In- the lack of a financial incentive to for the interconnection of slices of ternet architectures to support the do so or the requirement for co- different operators to provide end- multitude of heterogeneous wire- ordinated simultaneous deployment to-end connectivity with specific less technologies that are emerging. everywhere in the Internet. Network resource guarantees and network It also requires decision mechan- virtualization may provide a path characteristics. isms which of these technologies to out of this stalemate [10]. Virtu- As an example, virtualization use alternately or concurrently, de- alization of processing and storage canbeusedforamoreradicalim- pending on the current situation. resources is already widely used, and plementation of overlay networks. For example, to conserve cellular re- the flexibility it provides is highly The latter constitute their own part sources, parts of the content may be useful, e. g., for the operation of of the solution space for a fu- streamed to some device of a cluster, data centers and server farms. It has ture Internet design, but they can and devices use local communica- also been applied to networking in also be considered as a seed for tion inside the cluster to exchange the form of virtual private networks new, more radical designs. Here information until all users have (VPNs), but these are usually con- virtualization would be the mech- all the content they are interested fined to a single ISP and do not offer anism to allow overlay network in [16]. resource guarantees. techniques to be implemented in In addition to technologies for Network virtualization brings lower layer protocols for higher effi- global connectivity, local commu- this concept one step further by ciency. Similar considerations hold nication standards and systems de- allowing for isolation of network for other technologies such as net- mand their integration to the mo- resources on all layers of the pro- work coding [13] or content based bile Internet: Bluetooth, UWB, Near tocol stack. The virtual network routing [14]. Field Communication, ad hoc net- created by the interconnection of The flexibility offered by networking, sensor networks, femto virtual routers through virtual links work virtualization is also of par- cells, as well as special purpose net- is called a slice. Slices can be used ticular interest to a mobile operator, works such as DVB, MediaFlow, etc. to facilitate experimentation with where the mobility of terminals cre- Here, the use of software defined different future Internet architec- ates high (but partially predictable) radios is a promising technology to tures [11], but it may even be that fluctuations in traffic demand over avoid the problem of integration of no single future Internet architec- time and space. Relocation of virtual many different radio transceivers on ture will emerge, and different new resources can be used to reduce the a device [17]. With the integration

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and the desire for information sharing will become a strong promoter of this new trend. Moreover, services that have a large impact on the society as a whole, for example, in electronic health care, force us to rethink traditional Internet service provisioning, adding specific requirements regarding privacy, security, and re- liability – requirements which the Internet of the past, as it has been pointed out, fell short to provide. Figure 3 Typical simulation result for a cross-layer optimized transmission system (MOS) compared with a conventional throughput optimized system (Throughput) with three application classes (voice, The future mobile Internet will video, ftp) for different symbol rates. have to support new methodologies for discovering services and infor- of local or personal area networks, plication model, and signaled to the mation, in particular when the new mobile phones are no longer con- respective layers. service world allows for a unifica- strained to serve only for personal It has to be carefully considered tion of information services with communications, but are used as to what extent the existing layering real world objects through the “In- a hub for information gathering should be broken up or if cross- ternet of Things”. and dissemination. As such, mobile layer information exchange as in the The Next Generation Network phones can play the role of gate- above example is enough to realize concept and in particular the IP ways between local networks and full application awareness in a fu- Multimedia System are possible en- the global network. ture Internet design. ablers for such an open service Access networks are usually platform. From an operator’s point under the control of one opera- 5 Service Platforms of view, they bring more intelligence tor who can implement proprietary Traditional telecommunication sys- to the Internet-based network, to al- solutions to overcome Internet de- tems have focused on rather closed, low for an easy service deployment ficiencies. One example is Wire- service specific networks in order by the operators. These platforms less TCP employing a dedicated to ensure the right service perform- are expected to be integrated into proxy where TCP is split running ance. One of the main advantages of a wider range of service platforms a modified protocol over the wire- the Internet from a service perspec- in the Internet, bringing the oper- less link [7]. tive is that it constitutes an open ser- ator into the position of a service Further future Internet require- vice platform where everybody can orchestrator rather than providing ments for access networks include contribute service offers. A future all services by itself. support for user perceived qual- Internet is expected to foster this With the emergence of all- ity of service, which demands for evolution of service provisioning by IP packet-based networks and ser- a better awareness of the diverse ap- shaping itself as a service integrating vice platforms such as IMS, the plication characteristics by the wire- network, intelligently orchestrating telecommunications world has fi- less resource management. Cross- service offers from a multitude of nally turned away from service spe- Layer Optimization [4] is one ap- providers on an open platform. cific networks to an integrated ser- proach to jointly optimize upper Currently we are experiencing vices network. However, this comes and lower network layers. Fig- a migration from traditional client at the cost of less tight integra- ure 3 illustrates that gains of up server service provisioning towards tion of services and higher overhead to1onthescaleofthesub- interactive web services that allow of managing services and ensuring jective measure of Mean Opinion for community building and for sat- their performance. It is the strong Score (1 = dissatisfied; 4.5 = excel- isfying societal needs. A central role belief of the authors that a cleverly lent) can be achieved for a joint in this fast changing environment is managed Future Mobile Internet, optimization of voice, video, and ftp played by a new user behavior. The where different service specific pro- users in one cell. As the user per- uptake of community based service tocol stacks may run in parallel in ceived quality (expressed in MOS) scenarios and information sharing different slices of a virtualized net- of each transmitted application has in, for example, a P2P environment work,willbeabletocombinethe a different sensitivity to changes of shows that the user is changing from advantages of service specific and parameters, a resource or quality a service consumer to an active ser- integrated services networks and optimized parameter setting can be vice and content provider. User’s thus prevail over the shortcomings determined when knowing the ap- self advertising such as life logging of today’s Internet design.

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6 Summary Magazine, Special Issue on Cross- in Wireless Neworks: an Agent-based In order to overcome deficiencies Layer Protocol Engineering, vol. 44, model. In: IEEE Int’l Symp. on Wire- of the current Internet architecture no. 1, Jan. 2006. less Communication Systems, 2007. a fundamental reconsideration of its [5] S. Buchegger and A. Feldmann. [17] U. Ramache. Software-Defined Radio design is discussed in academia and ARCADIA/NeXtworking’07 Workshop Prospects for Multistandard Mobile industry. Based on a general sum- Report on NeXtworking, the Second Phones. In: Computer, vol. 40, no. 10, mary of the requirements of a fu- COST-NSF Workshop on Future pp. 62–69, Oct. 2007. ture Internet design, this article high- Internet, Berlin, Germany, Apr. 2007. lights solutions and mechanisms for [6] M. Caesar, T. Condie, J. Kanna, their implementation from a mo- K. Lakshminarayanan, I. Stoica, and bile operator point of view. In par- S. Shenker. ROFL: Routing on Flat ticular, we have discussed address Labels. In: ACM SIGCOMM’06, Pisa, and mobility management concepts. Italy, Sep. 2006. For the implementation of such con- [7] H. Balakrishnan, V. N. Padmanabhan, cepts, overlay networks as well as S. Seshan, and R. H. Katz. A compar- 1 2 network virtualization are consid- ison of mechanisms for improving ered as viable tools. Their application TCP performance over wireless links. is discussed along examples such as In: IEEE/ACM Trans. on Networking, a managed hierarchical overlay net- vol. 5, no. 6, pp. 756–769, 1997. work. Whereas wireless access net- [8] R. Moskowitz, P. Nikander, P. Jokela, works themselves are rather closed and T. Henderson. Host Identity 3 systems where changes could be ap- Protocol, IETF Request for Comments plied independently, the integration 5201, Apr. 2008. 1 Dr. Wolfgang Kellerer is Senior Man- of multiple emerging wireless ac- [9]B.Ahlgren,J.Arkko,L.Eggert, ager of the Ubiquitous Networking Research cess standards such as WiMAX and and J. Rajahalme. A Node Identity Group at NTT DOCOMO’s European Re- WLAN with the cellular dominated Internetworking Architecture. In: IEEE search Laboratories in Munich, Germany. He mobile communication systems is Infocom, Apr. 2006. holds a MS degree and PhD from Technische a major challenge for the future In- [10] T. Anderson, L. Peterson, S. Shenker, Universität München. His research interests ternet. With the dominance of Inter- and J. Turner. Overcoming the Inter- include service platforms, P2P overlay net- net technologies in communication net Impasse through Virtualization. works, multimedia networking, and cross- networks, packet-based service plat- In: Computer, vol. 38, no. 4, pp. 34– layer design. forms have emerged. A major chal- 41, Apr. 2005. Address: see below, E-Mail: [email protected] lenge for the future is to open these [11] A. Bavier, N. Feamster, M. Huang, 2 Dr. Jörg Widmer is Project Manager of platforms to integrate services from Peterson, and J. Rexford. In vini the Ubiquitous Networking Research Group a multitude of providers. veritas: Realistic and controlled at NTT DOCOMO’s European Research network experimentation. In: ACM Laboratories in Munich, Germany. He holds References Sigcomm, 2006. a MS degree and PhD from Universität [1] F. Guillemin (ed.). The future Inter- [12] N. Feamster, L. Gao, and J. Rexford. Mannheim. His research is concerned with net: the operators’ vision. Project How to lease the internet in your MAC layer design, network coding, and report, EURESCOM project P1657, spare time. In: ACM Sigcomm algorithms for wireless multi-hop networks. Nov. 2007. Computer Communication Review, Address: see below, [2] M. Handley. Why The Internet Only vol. 37, no. 1, 2007. E-Mail: [email protected] Just Works. In: BT Technology [13] R. Ahlswede, N. Cai, S. Y. R. Li, and Journal, vol. 24, no. 3, July 2006. R. W. Yeung. Network information 3 Dr. Hendrik Berndt is Chief Technology [3] S. Zoels, Z. Despotovic, and flow. In: IEEE Trans. on Information Officer and Senior Vice President at W. Kellerer. On Hierarchical DHT Theory, 2000. NTT DOCOMO’s European Research Systems – An Analytical Approach [14] A. Carzaniga, M. J. Rutherford, and Laboratories in Munich, Germany. He also for Optimal Designs. In: Computer A. L. Wolf. A routing scheme for serves as Visiting Professor at the GITI of Communications (COMCOM), content-based networking. In: IEEE the Waseda University, Tokyo. His research Elsevier, vol. 31, issue 3, pp. 576–590, Infocom, Mar. 2004. interests include next generation mobile Feb. 2008. [15] Y. Wang, J. van der Merwe, and systems, service provisioning, and Future [4] S. Khan, M. Sgroi, Y. Peng, E. Stein- J. Rexford, Vroom: Virtual routers Internet design. bach, and W. Kellerer. Application- on the move. In: ACM SIGCOMM Address: DOCOMO Communications driven Cross Layer Optimization HotNets Workshop, 2007. Laboratories Europe GmbH, Landsberger for Video Streaming over Wireless [16] F. Albiero, F. H. P. Fitzek, and M. Katz. Str. 312, 80687 München, Germany, Networks. In: IEEE Communications Cooperative Power Saving Strategies E-Mail: [email protected]

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