distributed mobility management: a standards landscape

IEEE Communications Magazine • March 201380 0163-6804/13/$25.00 © 2013 IEEE

INTRODUCTION

Mobile data traffic has experienced exponentialgrowth over the last few years. We are witness-ing the proliferation of smart phone applica-tions that go beyond traditional web traffic tomore bandwidth-demanding and delay-sensitiveapplications such as video. New technologieslike HTML5, developed to provide a betterexperience to mobile users, are also driving anincrease in the traffic demand as they make iteasier for mobile devices to access content thatwas traditionally only available to desktop com-puters.

This increase in demand is having a seriousimpact on the dimensioning and planning ofmobile networks. Specifically, we note that:• Spectrum is limited and expensive, so avail-

able bandwidth for the access network can-not be easily increased.

• Deployed mobile core networks are highlyhierarchical and centralized, which intro-duces serious scalability and reliabilityissues.

Mobile network operators are addressing thefirst point in several ways:• By deploying more spectrum-efficient tech-

nologies, such as the Third GenerationPartnership Project (3GPP) Long TermEvolution (LTE)

• By using smaller densely deployed cells• By selectively offloading traffic from the cel-

lular access to alternative wireless technolo-gies such as WiFi

In order to address the second point, new net-work architecture approaches that distribute theresponsibility of providing connectivity andmobility are needed. Tackling this second point— that is, alleviating core network scalabilityconcerns in terms of number of users, requiredstate, and traffic load — is the focus of the pre-sent article. On one hand, some short-term solu-tions are being developed as evolution ofcurrently deployed mobile network architecturesto provide relief to current traffic problems. Onthe other hand, long-term alternatives capable ofcoping with the future expected traffic loads,involving a major redesign of the network archi-tecture, are being researched.

This article presents how current mobilitymanagement network architectures are being re-designed towards a more distributed operationthat mitigates the problems noted above. Theseproblems are presented in more detail later. Wepresent an overview of the solutions explored bythe two main standardization bodies in the fieldof mobile communications: the Internet Engi-neering Task Force (IETF)1 and 3GPP.2 Ourview of the potential evolution of these solu-tions is presented, where we discuss the futureevolution of IP mobility management architec-tures. Finally, we make some concludingremarks.

DMM MOTIVATIONCurrent packet-based mobile architectures, such asthe 3GPP evolved packet system (3GPP EPS) andWiMAX, make use of IP as the enabling technolo-gy for both voice and data communications. Thisimplies a key-role for IP mobility management inproviding the ubiquitous always-on network accessservice. Even though several applications do notcurrently require the network to provide IP mobili-ty support (meaning IP address continuity), thereare still many that do require it (e.g., voice or virtu-al private networking, to mention just a couple).Unfortunately, current IP mobility protocols relyon the use of a centralized and hierarchical archi-tecture, which poses several critical issues, asexplained in more detail next.

ABSTRACT

In this article, we introduce distributed mobil-ity management (DMM) — a new architecturalparadigm for evolving mobile IP networks. Wediscuss the technology trends that are driving amove toward DMM and what the relevant stan-dards development organizations (IETF and3GPP) are doing to address these new needs.We conclude with a discussion of how 3GPP’sevolved packet core can evolve toward a DMM-based architecture.

TELECOMMUNICATIONS STANDARDS

Juan Carlos Zún~iga, InterDigital Canada, Ltd.

Carlos J. Bernardos and Antonio de la Oliva, Universidad Carlos III de Madrid

Telemaco Melia and Rui Costa, Alcatel-Lucent Bell Labs

Alex Reznik, InterDigital

Distributed Mobility Management:A Standards Landscape

1 http://www.ietf.org/

2 http://www.3gpp.org/

BERNARDOS LAYOUT_Layout 1 3/1/13 12:41 PM Page 80

IEEE Communications Magazine • March 2013 81

Mobility management schemes standardizedby IETF for IPv6 networks are extensions to ormodifications of the well-known Mobile IPv6(MIPv6) [1], and can be classified into two mainfamilies: client-based mobility protocols and net-work-based mobility protocols.

Client-based mobility approaches, such asMIPv6 and Dual Stack MIPv6 (DSMIPv6) [2],enable global reachability and session continuityby introducing the home agent (HA), an entitylocated at the home network of the mobile node(MN) that anchors the permanent IP address usedby the MN, called the home address (HoA). TheHA is in charge of defending the MN’s HoA whenthe MN is not at home, and redirecting receivedtraffic to the MN’s current location. When awayfrom its home network, the MN acquires a tempo-ral IP address from the visited network, called acare-of address (CoA), and informs the HA aboutits current location. An IP bidirectional tunnelbetween the MN and the HA is then used to redi-rect traffic to and from the MN.

With network-based mobility managementprotocols, such as Proxy MIPv6 (PMIPv6) [3],MNs are provided with mobility support with-out their involvement in mobility managementand IP signaling, as the required functionality isrelocated from the MN to the network. In par-ticular, movement detection and signaling oper-ations are performed by a new functional entitycalled the mobile access gateway (MAG), whichusually resides on the access router (AR) forthe MN. In a localized mobility domain (LMD),which is the area where the network providesmobility support, there are multiple MAGs.The MAG learns through standard terminaloperation, such as router and neighbor discov-ery, or by means of link-layer support about anMN’s movement and coordinates routing stateupdates without any mobility-specific supportfrom the terminal. The IP prefixes (home net-work prefixes) used by MNs within an LMD areanchored at an entity called the local mobilityanchor (LMA), which plays the role of localHA of the LMD. Bidirectional tunnels betweenthe LMA and the MAGs are set up, so the MNis enabled to keep the originally assigned IPaddress despite its location changes within theLMD. Through the intervention of the localmobility anchor, packets addressed to the MNare tunneled to the appropriate MAG withinthe LMD, hence making the MN oblivious toits own mobility. The 3GPP also supports avariant of network-based IP mobility that usesthe general packet radio service (GPRS) tun-neling protocol instead of PMIPv6, with thepacket gateway (PGW) playing the role of theLMA in the EPS and the GGSN playing therole of the LMA in the legacy UMTS/GPRSnetwork.

Whatever flavor of IP mobility a modern-daymobile network operator (MNO) chooses todeploy, a constant feature of the operator’s archi-tecture will be the presence of a central entity(HA/LMA/PGW/GGSN) that anchors the IPaddress used by the MN. This centralized func-tion is in charge of coordinating the mobilitymanagement; in the 3GPP this is done in con-junction with a control function called the mobil-ity management entity (MME). As a result, thesecentralized mobility anchors are burdened withdata forwarding and control mechanisms for ahuge number of users. Figure 1 summarizes theoperation of the IETF MIPv6, PMIPv6 protocols,as well as the GPRS Tunneling Protocol (GTP),which is one of the network-based mobility vari-ants adopted by 3GPP. Table 1 shows, for themain mobility protocols and architectures, theequivalence between the principal mobility rolesand the logical entities playing them.

While this centralized way of addressingmobility management has been fully developedby the MIP protocol family and its many exten-sions, it brings several limitations that have beenidentified in [4].

Suboptimal routing: Since the (home)address used by an MN is anchored at the homelink, traffic always traverses the central anchor,leading to paths that are, in general, longer thanthe direct one between the MN and its commu-nication peer. This is exacerbated with the cur-rent trend in which content providers push theirdata to the edge of the network, as close as pos-sible to the users, as for example deploying con-tent delivery networks (CDNs). With centralizedmobility management approaches, user trafficwill always need to go first to the home networkand then to the actual content source, some-times adding unnecessary delay and wastingoperator resources.

Scalability problems: Existing mobile net-works have to be dimensioned to support all thetraffic traversing the central anchors. This posesseveral scalability and network design problems,as central mobility anchors need to have enoughprocessing and routing capabilities to be able todeal with all the users’ traffic simultaneously.Additionally, the entire operator’s networkneeds to be dimensioned to be able to cope withall the users’ traffic.

Reliability: Centralized solutions share theproblem of being more prone to reliability prob-lems, as the central entity is potentially a singlepoint of failure.

In order to address these issues, a new archi-tectural paradigm, called distributed mobilitymanagement (DMM), is being explored by bothresearch and standards communities. DMMintroduces the concept of a flatter system archi-tecture, in which mobility anchors are placed

DMM introduces the

concept of a flatter

system architecture,

in which mobility

anchors are placed

closer to the user,

distributing the

control and data

infrastructures

among the entities

located at the edge

of the access

network.

Table 1. Equivalence between main mobility roles and logical entities.

MIPv6 Proxy MIPv6 GPRS and UMTS EPS

Mobility anchor HA LMA GGSN PGW

Signaling agent MN MAG SGSN SGW/ePDG/eNB


IEEE Communications Magazine • March 201382

closer to the user, distributing the control anddata infrastructures among the entities locatedat the edge of the access network. Critically,DMM introduces the ability of an MN to movebetween mobility anchors, something that is notpossible with any of the present centralizedapproaches. Additionally, it is worth noting thatby removing all the difficulties posed by thedeployment of a centralized anchoring andmobility approach, adoption of DMM approach-es is expected to be easier.

DMM IN STANDARDSIn this section we provide an overview of currentDMM or DMM-like initiatives in the IETF and3GPP standards organizations.

DMM IN THEINTERNET ENGINEERING TASK FORCE

The IETF is at the moment the main driverstandardizing solutions for distributed mobilitymanagement. The DMM Working Group3 waschartered in March 2012 to address the emerg-ing need for mobile operators to evolve existingIP mobility solutions toward supporting a dis-tributed anchoring model. The IETF first iden-tied the requirements that an IP distrubutedmobility management solution should meet [4],and it is currently analyzing existing practices forthe deployment of IP mobility solutions in aDMM environment [5]. The goal of this analysisis to identify what can be achieved with existingmobility solutions and which functions are miss-ing in order to meet the identified DMMrequirements.

In terms of solution space, three main classesof solutions can be identified (Figure 2 showsoperational examples of each of them):• Client-based• Network-based• Routing-basedIn the case of client-based mobility, existingproposals aim at deploying multiple HAs at theedge of the access network, thus distributing theanchoring. The basic concept is that an MN nolonger uses a single IP address anchored at acentral HA, but configures and uses an addi-tional IP address at each visited access network.The MN uses the locally anchored address tostart new communications, while maintainingreachability for those IP addresses that are stillin use by active communications. This requiresthe MN to bind each of the active (home)addresses with the locally anchored address cur-rently in use, which is actually playing the roleof CoA in these bindings. Session continuity isguaranteed by the use of bidirectional tunnelsbetween the MN and each one of the HAsanchoring in-use addresses, as shown in Fig. 2a.This deployment model, proposed, for example,in [6, 7], does not require changes in the proto-col behavior of the network entities. However, itrequires extensions and additional intelligenceon the MN side, as it has to manage multipleaddresses simultaneously, select the right one to

3 http://datatracker.ietf.org/wg/dmm/Figure 1. Overview of the a) MIPv6, b) PMIPv6, and c) GTP protocols.

AR5

a)MN1

@HoA1,@CoA1

MN1@HoA1,@CoA2

AR1

IPv6-in-IPv6tunnel

HA1

AR4AR3AR2

Operator’snetwork

@HoA1 → @CoA1

@HoA1 → @CoA2

HA1’s binding cache

Internet

CN1

MAG5

b)MN1

@HoA1MN1

@HoA1

MAG1

IPv6-in-IPv6tunnel

LMA1

MAG2 MAG3 MAG4

Operator’snetwork

@HoA1 → MAG1

@HoA1 → MAG5

LMA1’s binding cache

Internet

CN1

c)MN1@IP1

MN1@IP1

SGW1LTe

3GPP access Trusted non-3GPPIP access

IPsec tunnel

HSSAAAePDG

GTP tunnel

PGW

MME Operator’snetwork

@IP1 → SGW1

@IP1 → ePDG

PGW table

Internet

CN1

LTe LTe

Untrusted non-3GPPIP access



use for each communication, keep track of thoseaddresses that need mobility support, and per-form the required maintenance operations (i.e.,binding, signaling, and tunneling). Additionally,non-locally-anchored traffic experiences subop-timal routing. Consider the example in Fig. 2a;here MN1 initially attaches to the distributedanchor HA/AR1 and configures the IPv6address HoA1 to communicate with a corre-spondent node CN1. If MN1 moves to HA/AR5,a new locally anchored IPv6 address is config-ured (HoA2) and used for new communications(e.g., with CN2). The continuity of the sessionwith CN1 is provided by a tunnel set up betweenthe MN and HA/AR1.

With respect to the network-based solutions,two sub-families can be identified:• Solutions with a fully distributed model• Solutions with a partially distributed modelThe distinction between fully and partially dis-tributed approaches has to do with whether ornot the control plane and data plane are tightlycoupled. In the fully distributed model, mobili-ty anchors are moved to the edge of the accessnetwork, and they manage both control anddata planes. For instance, in a fully distributedmodel and using PMIPv6 terminology, eachaccess router implements both LMA and MAGfunctions, and for each user the access routercould behave as an LMA (thus anchoring androuting the local traffic for a given user) or asan MAG (thus receiving the tunneled trafficfrom the virtual home link of the given user).If we consider a partially distributed model,the data and control planes are separated, andonly the data plane is distributed. In this sense,the operations are similar to 3GPP networkswhere the control plane is managed by theMME, and the data plane by the SGW andPGW. An example of the operation of a gener-ic network-based DMM solution is shown inFig. 2b.

The split of the control plane and data planeallows the mobility anchors to optimally routethe data traffic while relying on a single centralentity to retrieve the localization of the con-nected mobile devices, that is, the tuple {cur-rent mobility anchor router, mobile nodeidentifier}. There are proposals to extend thePMIPv6 protocol to achieve this by either main-taining legacy with current PMIPv6 deploy-ments or proposing new extensions andchanging the way PMIPv6 functions are imple-mented. Among the ones of the first category,[8] proposes implementing local routing at theMAG. In fact, the PMIPv6 binding signalingexchange is extended to allow the MAG todefend a pool of IP addresses, thus routingtraffic directly through the Internet. To accessthe operator services, the MN can still use theIP address anchored at the LMA. This, howev-er, requires the management of several IPaddresses at the MN and the selection of a spe-cific IP address for a specific service. Alterna-tively, [9] introduces the logical entity of acentral mobility database to maintain users’localization information and allow the setup ofon-demand tunneling when a specific servicerequires seamless mobility support.

It is worth highlighting that network-based Figure 2. a) Client-, b) network-, and c) routing-based DMM approaches.

IPv6-in-IPv6tunnel

HA/AR5HA/AR1

@HoA1 → @HoA2

a)MN1

@HoA1MN1

@HoA1,@HoA2

Operator’snetwork

Internet

CN1CN2

IPv6-in-IPv6tunnel

LMA/MAG5LMA/MAG1

@HoA1 → LMA/MAG5

b)MN1

@HoA1MN1

@HoA1,@HoA2

Operator’snetwork

Internet

CN1CN2

AR5AR1

c)MN1

@HoA1MN1

@HoA1

Operator’snetwork

Internet

CN1CN2



approaches pose more challenges than host-based ones, as the mobile terminal needs toappropriately handle different IP addresses inboth cases, but this is harder to achieve withoutsome support from the host.

Last, routing-based proposals (e.g., [10]) fol-low a completely different approach. In thiscase, when the MN attaches to an accessrouter, it obtains an IP address that is theninternally advertised within the domain usingan intra-domain protocol (e.g., IBGP). Whenthe node moves and attaches to a differentaccess router, the access router finds out theaddress assigned to the MN during the authen-tication phase, and then proceeds to update itsroutability via routing updates. In this way, thereachability of the node is ensured while mov-ing within the domain. This approach, howev-er, has some limitations in terms of handoverlatency (limited by the intra-domain routingconvergence) and scalability (i.e., storms ofrouting updates). An example of this type ofsolution is shown in Fig. 2c.

In addition to these three main DMM solu-tion classes, the IETF is also looking at how todistribute the anchoring and mobility supportwith other approaches, such as MobileLocator/Identifier Separation Protocol (LISP)and Identifier-Locator Network Protocol(ILNP). However, in this article we limit thescope of our analysis to DMM evolutionaryextensions of approaches exhibiting a provenrecord in industry and some deployment experi-ence, and thus not covering more disruptiveand/or clean slate architectures.

Overall, the IETF DMM group is still in theearly stages of standardization, and it is difficultto draw a full picture of what eventually willbecome the proposed solution. It is, however,clear that there is strong interest in addressingthe current issues, especially when new services(e.g., distributed caching for multimedia contentor CDN) representing renewed business rev-enues for MNOs require a paradigm shift in theway mobility support is provided today.

DMM IN THE THIRD GENERATIONPARTNERSHIP PROJECT

Although no DMM-specific efforts are ongoingin 3GPP, several developments indicate a trendtoward more flexible and dynamic mobility man-agement. In this section, we summarize thesedevelopments. Later, we show how these solu-tions can be built on to introduce full-blownDMM concepts into 3GPP.

Our discussion focuses on the evolved packetcore (EPC) [11], and we begin by discussing thetwo architectural entities that are key to IP traf-fic management: the serving gateway (SGW) andthe packet data network gateway (PGW). TheSGW is the gateway function in the 3GPP thatterminates the interface toward the radio accessnetwork (E-UTRAN in 3GPP lingo), whichmeans the SGW is the point in the networkbeyond which the MN4 can maintain connectiononly at IP layer or above. The SGW is also incharge of below-IP mobility between base sta-tions in a single E-UTRAN. However, the SGWdoes not provide IP mobility anchoring capabili-

ties; hence, while the SGW is often located atthe edge of the core network, it cannot supportDMM-like functionality.

The PGW is the anchor node for IP ser-vices, including IP-based mobility, IP addressmanagement, and other operator services suchas data traffic monitoring for the purposes ofQoS control, charging, and so on. While anoperator may maintain multiple PGWs, thesegateway functions are used to provide a partic-ular service to the whole operator network, orat least a significant portion of it. For example,a U.S.-based operator may maintain separatePGWs for its New England operations and itsCalifornia operations, but it would not do sofor each neighborhood in the city of Boston.As such, IP mobility between PGWs is not sup-ported. In fact, the UE cannot even keep thesame IP address if it changes PGWs. In theevent that the UE does move from one PGWto another, it will experience an interruption ofdata services. Of course, given the large-scalecoverage of PGWs, this is unlikely and thuslack of mobility support across PGWs is not amajor concern for operators.

However, the fact that a central gateway nodeanchors a significant amount of traffic for a net-work’s users in a very large geographical areadoes raise other serious issues, as introducedearlier. Two issues are particularly acute:• The sheer amount of traffic “hitting” the

PGW• The often highly suboptimal routes that the

need to anchor traffic at the PGW forcesIt would appear that one way to address thisproblem would simply be to allow PGWs tocover much smaller areas and/or become muchmore service-specific. However, this wouldnecessitate support of one key feature currentlynot supported by the PGW: inter-PGW mobility.In fact, as we shall describe in detail shortly, thisis precisely what DMM provides, and thus webelieve that DMM offers the right long-termparadigm for the EPC evolution.

Nevertheless, a full DMM approach is stillsomewhat far away in time. In the near term,though, 3GPP does provide two approachesdesigned to relieve the loading introduced by IPtraffic into the 3GPP core: selected IP trafficoffload (SIPTO) and local IP access (LIPA)[11]. SIPTO enables an operator to offload cer-tain types of traffic at a network node close tothe UE’s point of attachment to the access net-work, by selecting a set of gateways (SGW andPGW) that are geographically or topologicallyclose to the UE’s point of attachment. Theupside to the operator is lower load on its net-work. However, mobility support for SIPTO traf-fic can be rather limited, and offloaded trafficcannot access operator services (as they are onlyavailable in the private operator’s network).Thus, the operator must be very careful in select-ing which traffic to offload.

LIPA, on the other hand, enables an IP-capable UE connected via a home eNode B(HeNB) to access other IP-capable entities inthe same residential/enterprise IP networkwithout the user plane traversing the mobileoperator’s network core. In order to achievethis, a local gateway (L-GW) is used, which

4 In 3GPP, the mobilenode is called user equip-ment (UE). In this articlewe use both terms, UEand MN, to refer to amobile node.

A full DMM

approach is still

somewhat far away

in time. In the near

term, though, 3GPP

does provide two

approaches designed

to relieve the loading

introduced by IP

traffic into the 3GPP

core: selected IP

traffic offload (SIPTO)

and local IP access

(LIPA).



implements a subset of the PGW functionality.LIPA is established by the UE requesting a newpacket data network (PDN) connection to anaccess point name (APN) for which LIPA ispermitted, and the network selecting the localGW associated with the HeNB and enabling adirect user plane path between the local GWand the HeNB.

Like SIPTO, mobility support for trafficoffloaded using LIPA is very limited. However, a3GPP work item on LIPA mobility and SIPTOat the local network (LIMONET) [12] is cur-rently studying how to provide SIPTO and LIPAmechanisms with some additional, but still limit-ed, mobility support. In general and withoutgoing into fine details, LIPA mobility support islimited to handovers between HeNBs that aremanaged by the same L-GW (i.e., mobility with-in the local domain), while seamless SIPTOmobility is still limited to the case where theSGW/PGW is at or above the radio access net-work (RAN) level. Seamless mobility at the localnetwork is still not considered in SIPTO. There-fore, although SIPTO and LIPA allow offloadingtraffic from the network core in ways that appearsimilar to the DMM approaches, even withLIMONET these provide only localized mobilitysupport; and when the UE moves outside itslocal area, packet data connections have to bedeactivated and reactivated.

Another important aspect of the present3GPP approach to mobility management is therole of the mobility management entity (MME).While we do not provide a full overview of thiscritical architectural function in 3GPP, it isworth noting some of the key functions that theMME supports [11]:• UE reachability, including maintaining

information about the UE state and loca-tion of connection to the network as well asidle mode procedures such as paging

• Selection of the gateway (PGW and SGW)the UE should be using

• Management of bearers associated with theUEHow the MME evolves and changes with the

introduction of DMM concepts into the 3GPPnetwork is a subject worthy of a separate paper.However, it should be clear that the role ofMME in such evolved networks is an importantconsideration. For instance, the MME may playa role in the selection of the “distributed”anchor.

POSSIBLE EVOLUTIONAs stated earlier, 3GPP is currently standard-

izing methods to deploy local GWs addressingenterprise scenarios (e.g., LIPA) and more tradi-tional cellular deployments (e.g., SIPTO abovethe RAN). Considering that LIPA is a fourthgeneration (4G)-only solution, and SIPTORelease 10 has been specified for both 3G and4G networks, we focus on the 4G network(EPC), deliberately leaving aside considerationson the integration of legacy networks.

There are two main drivers of distributedanchoring GWs for cellular networks. The firstis geographical. In some countries MNOs areexpected to cover a geographically large terri-

tory, hence requiring deployment of a largenumber of PGWs with a certain degree oflocality. The second driver is the need to sup-port a new set of services that require a net-work of service-anchoring gateways. Amongthese, multimedia content distribution is per-ceived as a particularly acute problem facingMNOs. A promising approach to address thisissue is via distribution of caching systems asoverlay networks (e.g., CDNs); however, suchdistributed caching requires a distributedanchoring solution to go along with it. As thesenew services emerge as important new sourcesof revenue for the mobile operators, the opera-tors are ever more likely to invest in upgradesof their network infrastructure that supportthese new revenue sources.

A distributed mobility management approachis widely believed to be the likely upgrade path.As we shall see, it provides a means to distributea network gradually and partially, giving theoperator the ability to easily evolve from a cen-tralized architecture to a distributed one, anddistributing mobility anchoring only to the extentit needs to do so.

SIPTO above the RAN can be consideredthe first step. As depicted in Fig. 3, the distri-bution of the L-GW on top of the SGW assignsusers to a closer gateway, enabling a betterresponse in terms of round-trip delays andlocalization of services. The main drawback ofcurrent solutions is that when the UE movesfrom one region to another, the local GW maychange, and there is no support of seamlessmobility between local GWs. This may not bean issue for applications that can survive an IPaddress change (e.g., for a given access pointname the UE has to re-establish the PDN con-nection to the new GW and therefore changeits IP address), but it could impact ongoing ses-sions such as a voice over IP (VoIP) call. One

Figure 3. Network evolution.

SWm

’(d

iam

eter

)

S2a

S5

S11

S1u

S1u

S1u

S1u

TWAGHotspot

Macrocells

Macrocells

L-GW

PGWPacket core

Internet

HSS/HLRAAA

SGW

MME

SGW

L-GW

L-GW



strategy to solve this issue could be to enabledata forwarding between the old GW and thenew GW, but in terms of 3GPP semantics thisis not possible since the UE would need to con-figure two IP addresses for the same accesspoint name on two different PGWs (e.g., anAPN implies one PDN connection and henceone IP address). There are solutions that per-mit the use of an APN simultaneously on bothcellular and WiFi, like the seamless network-based IP flow mobility (NB-IFOM), althoughthey have not yet been fully described in thespecifications. Also, since Release 9, it is possi-ble to enable multiple PDN connections to thesame APN for PMIPv6-based interfaces (MUP-SAP). This, however, is limited to PMIPv6-based interfaces. Moreover, as of today only afew operators are deploying the S5 interface(i.e., the one providing user plane tunnelingbetween the SGW and the PGW) based onPMIPv6. GTP, on the other hand, inherentlysupports this functionality.

The next step would be to also enable theselection of L-GW for WiFi networks, assumingthe MNO is deploying the so-called trusted WiFiaccess (i.e., S2a-based mobility over GTP —SaMOG). Some past proposals do developSIPTO for WiFi, but they are primarily targetingtraffic offload, and do not have enough supportfrom manufacturers and service providers. Theuse of distributed caching at anchors closer tothe UE could renew the need for standardizingsuch functionality.

Now that we have introduced multiple localPGWs in the cellular network and converged theLIPA and SIPTO functions under the sameframework, these L-GWs can be used to supporta full-fledged DMM framework. Full inter-GWmobility is enabled using techniques such asthose presently under consideration by IETF,while LIPA and SIPTO become features that areenabled by the overall framework. One exampleof how this is done can be found in [13].

CONCLUSIONThe challenges facing mobile network architec-tures in the application- and service-centeredfuture are indeed tremendous, as data demandsof mobile users are already stressing the existingnetwork. However, we believe that a flexibleapproach to network architectures, combinedwith an equally flexible spectrum and coveragestrategy, can go a long way toward addressingthese challenges. Indeed, architectural flexibilitywill allow network operators to offer the “rightnetwork” to the “right services.” However, to besuccessful, a “flexible network” technology mustbe an evolution of existing networks. The alter-native would require operators to abandon bil-lions of dollars of existing investment for what islikely to be billions of dollars to deploy a brandnew network — a proposition that is not palat-able in practical terms.

We believe DMM offers the right solution.As an architectural paradigm, it is designed tobe flexible and distributed “from the core,” andit builds and evolves from existing IETF and3GPP mobility protocols. Additionally, it can beintroduced into 3GPP in a gradual and additive

fashion, either complementing or replacing exist-ing functions, depending on the operator’s needs.Moreover, it evolves those features of the 3GPPsystems that are already being deployed as spotsolutions to the bandwidth crunch. Accordingly,we encourage the community at large to followthe development of this technology closely.

ACKNOWLEDGMENTSThe research of Carlos J. Bernardos, TelemacoMelia, and Antonio de la Oliva has been partial-ly funded by the European Community’s Sev-enth Framework Programme (FP7-ICT-2009-5)under grant agreement no. 258053 (MEDIEVALproject). Carlos J. Bernardos has also been par-tially funded by the Ministry of Science andInnovation of Spain under the QUARTET pro-ject (TIN2009-13992-C02-02).

REFERENCES[1] C. Perkins, D. Johnson, and J. Arkko, “Mobility Support

in IPv6,” IETF RFC 6275, July 2011.[2] H. Soliman, “Mobile IPv6 Support for Dual Stack Hosts

and Routers,” IETF RFC 5555, June 2009.[3] S. Gundavelli et al., “Proxy Mobile IPv6,” IETF RFC 5213,

Aug. 2008.[4] H. Chan, “Requirements of Distributed Mobility Man-

agement,” Internet draft, Dec.. 2012.[5] D. Liu et al., “Distributed Mobility Management: Cur-

rent Practices and Gap Analysis,” Internet draft, Feb.2013.

[6] B. Sarikaya, “Distributed Mobile IPv6,” Internet draft,Feb. 2013.

[7] F. Giust, A. de la Oliva, and C. J. Bernardos, “Flat Accessand Mobility Architecture: An IPv6 Distributed ClientMobility Management Solution,” IEEE Mobiworld 2011,in conjunction with IEEE INFOCOM 2011, Apr. 2011.

[8] J. Korhonen and T. Savolainen, “Local Prefix LifetimeManagement for Proxy Mobile IPv6,” Internet draft,Mar. 2012.

[9] C. J. Bernardos et al., “A PMIPv6-Based Solution for Dis-tributed Mobility Management,” Internet draft, Mar.2012.

[10] P. McCann, “Authentication and Mobility Managementin A Flat Architecture,” Internet draft, Mar. 2012.

[11] 3GPP, “General Packet Radio Service (GPRS) Enhance-ments for Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN) Access,” TS 23.401, Sept. 2011.

[12] 3GPP, “LIPA Mobility and SIPTO at the Local Network,”TR 23.859, July 2011.

[13] C. J. Bernardos, J. C. Zuniga, and A. Reznik, “TowardsFlat and Distributed Mobility Management: A 3GPPEvolved Network Design,” 1st ICC Wksp. Telecommun.Standards, 2012.

BIOGRAPHIESJUAN CARLOS ZÚN

~IGA ([email protected]) is

a principal engineer at InterDigital, currently leading stan-dardization activities in the area of IP mobility, heteroge-neous networks, and distributed content management. Hehas actively contributed and held leadership roles in differ-ent standards fora, such as IEEE 802, IETF, and 3GPP. Hehas been with InterDigital since 2001. Previously heworked with Harris Communications in Canada, Nortel Net-works in the United Kingdom, and Kb/Tel in Mexico. Hereceived his engineering degree from UNAM, Mexico, andhis M.Sc. and DIC from Imperial College, London. He is aninventor of more than 25 granted U.S. patents and 70published applications. He has been granted several recog-nitions like the BoD Chairman’s Award to the most out-standing patent application and the British CouncilFellowship.

CARLOS J. BERNARDOS ([email protected]) received a telecom-munication engineering degree in 2003 and a Ph.D. intelematics in 2006, both from the University of Carlos III ofMadrid (UC3M), where currently he works as an associateprofessor. From 2003 to 2008 he worked at UC3M as aresearch and teaching assistant. His current work focuseson IP-based mobile communication protocols and vehicular

We believe DMM

offers the right solu-

tion. As an architec-

tural paradigm, it is

designed to be flexi-

ble and distributed

“from the core,” and

it builds and evolves

from existing IETF

and 3GPP mobility

protocols. Additional-

ly, it can be intro-

duced into 3GPP

in a gradual and

additive fashion.



networks. His Ph.D. thesis focused on route optimizationfor mobile networks in IPv6 heterogeneous environments.He has actively contributed and held leadership roles in theIETF. He has published over 50 scientific papers in presti-gious international journals and conferences, and hasserved as a Guest Editor of IEEE Network.

TELEMACO MELIA ([email protected])received his informatics engineering degree in 2002from the Polytechnic of Turin, Italy, and his Ph.D. inmobile communications from the University of Göttin-gen in April 2007. Until December 2007 he worked atNEC Europe Ltd. in the Mobile Internet Group focusingon IP mobility support across heterogeneous networks.In September 2008 he joined Alcatel-Lucent Bell Labsworking on the 3GPP evolved packet core and IETF stan-dardization bodies. His main research interests includewireless networking, next generation networks, andmultimedia platforms.

ANTONIO DE LA OLIVA ([email protected]) received a telecom-munication engineering degree in 2004, and a Ph.D. intelematics in 2008, both from UC3M, where he worked asa lecturer and researcher since 2005. His research isfocused on mobility in heterogeneous networks and wire-less systems. He has published over 20 scientific papers inprestigious international journals and conferences, and he

is also an active contributor to the IEEE 802.21 where hehas served as Vice-Chair of IEEE 802.21b.

RUI COSTA (rui [email protected])received his Ms.C. in computers and telematics in 2008from the University of Aveiro, Portugal. During the spring-summer semester of 2007 he was an intern for the IVCgroup of NEC Deutschland in Heidelberg, Germany. He iscurrently a Ph.D. student with Alcatel-Lucent Bell LabsFrance. His interests are focused on DMM, PMIP, andmobile, vehicular, and heterogeneous networks.

ALEX REZNIK ([email protected]) is a senior prin-cipal engineer at InterDigital, currently leading the compa-ny’s research and system design activities in the area of IPmobility and heterogeneous networks. Since joining Inter-Digital in 1999, he has been involved in a wide range ofprojects, including leadership of 3G modem ASIC architec-ture, design of advanced wireless security systems, andcoordination of standards strategy in the cognitive net-works space. He earned his Ph.D. in electrical engineeringfrom Princeton University and holds a visiting facultyappointment at WINLAB, Rutgers University, where he col-laborates on research in cognitive radio, wireless security,and future mobile Internet. He is an inventor of 70 grantedU.S. patents, and has been awarded numerous awards forinnovation at InterDigital.

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distributed mobility management: a standards landscape

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