Journal of Network and Computer Applications 36 (2013) 1579–1588

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VNET6: IPv6 virtual network for the collaboration betweenapplications and networks

Dujuan Gu a,b,*, Xiaohan Liu a, Gang Qin a, Shuangjian Yan a,b, Ze luo a, Baoping Yan a

a Computer Network Information Center, Chinese Academy of Sciences, Beijing 100190, Chinab University of Chinese Academy of Sciences, Beijing 100190, China

a r t i c l e i n f o

Article history:Received 15 August 2012Received in revised form14 December 2012Accepted 15 February 2013Available online 15 March 2013

Keywords:Network architectureCollaborationIPv6VirtualizationService cloud

45/$ - see front matter & 2013 Elsevier Ltd. Ax.doi.org/10.1016/j.jnca.2013.02.011

esponding author at: Computer Networky of Sciences, Beijing 100190, China. Tel./fax:ail address: gudujuan@cnic.cn (D. Gu).

a b s t r a c t

The scarcity of IPv4 makes IPv6 deployment critical for all network-based applications. However, the bigissue of IPv6 is that we lack real applications that are based on IPv6. The application demands forflexibility, availability and management are hard to be met by the current network. Hence, it has becomeextremely urgent how IPv6 network can be tailored to meet the application specified requirements. Inorder to address the need, we propose IPv6 virtual network architecture (VNET6) to help to accelerate themomentum of IPv6 deployment. VNET6 differs from other proposed architectures. It supports incrementalnetwork evolution with the virtual collaboration environment, which has distinct features includingflexible service provision, reliable service entity, end-to-end flow management and ubiquitous access. Thecollaboration mode provides the bidirectional interaction between applications and networks via intent-based interfaces. IPv6 provides feasibility for the deployment of the virtual environment and the IPv6critical protocols are employed in VNET6. Our initial prototype study and comparative analysisdemonstrate that VNET6 can be adapted to meet the specific application requirements.

& 2013 Elsevier Ltd. All rights reserved.

1. Introduction

The scarcity of IPv4 makes IPv6 deployment critical for allnetwork-based applications. However, the big issue of IPv6 is thatwe lack real applications that are based on IPv6, as IPv6 is anumerical label which cannot provide better services for thenumerous applications than IPv4. Many researchers were on thesearch for the so-called “killer applications” of IPv6 to see thatmore benefits can be delivered than IPv4. Internet AssignedNumbers Authority (IANA) exhausted its IPv4 free pool in February2011, yet IPv6's killer applications have not been found. Hence, ithas become extremely urgent how IPv6 network can be tailored tomeet the specific application requirements.

It is well known that the current architecture is facing unpre-cedented challenges in the services context with the advent ofnumerous applications.

•

Flexibility: The network architecture has ossified. As manyapplications spring up, it is resistant against adding the newapplication-level services. However, the key trend is the profu-sion of services over the Internet (e.g. Google, Facebook,YouTube and similar services form the bulk of Internet traffic).Cloud computing and the proliferation of mobile deviceshave led to further growth in services. Google had to resort

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Information Center, Chineseþ86 10 58812294.

to a self-control network to reduce the “time-to-market” fornew applications. In April 2012, Google has unveiled the G-Scale network, which is the internal backbone and carriestraffic between data centers for Google's applications (Kuzniaret al., 2012).

•

Availability: All kinds of applications demand for communicationguarantee and service availability. It should be noted that theoccurrences of network instability may have primary negativeeffects on applications such as jeopardizing. For example, in arecent incident in China, the online ticketing system “12306.cn”crashed when huge number of customers seeking to purchasetickets in holidays. Moreover, the network is unreliable andarbitrarily delays and drops packets without resource reservefor end-to-end quality.

•

Management: We still do not understand how to set up the“control plane” in such manner that the network can operatereliably, can be easily manageable, and scalable well for variousof applications (Feldmann, 2007). The current network is stillnotoriously hard to manage with more than six thousandRequest For Comments (RFC) protocols and tens of thousandsof manual configuration commands scattered among thou-sands of devices (Hucaby and McQuerry, 2002). Also the net-work utilization of Internet is only 30%, as Internet does notproactively take steps to manage the application traffic.

So the emerging demands for flexibility, availability and man-agement are hard to be met by the current IPv4 network. The mainreason is the isolation between applications and networks. On the

D. Gu et al. / Journal of Network and Computer Applications 36 (2013) 1579–15881580

one hand, there is no efficient way for the applications to visualizethe underlying network topology and to control the paths from theusers to the servicers. In order to capture the information of thenetwork, the applications need to probe the network to under-stand its capabilities and what it can deliver. For example, gamingapplications use the utilities of link ping statistics to constantlymonitor network latency. This leads to low efficiency and highwaste. On the other hand, the network only knows where toforward packets and does not care about what the packets containand what their specific requirements are. The network develop-ment tends to require the network to identify service require-ments to improve network efficiency and value, hence it needs tospy on traffic through deep packet inspection and stateful flowanalysis, etc. But it is immensely difficult to spy on all trafficsabove networks. Trying to understand each other's behavior isinefficient and results in compromised service quality as well asinconsistent experience for the users. There is little bidirectionalinteraction and the feedback loop between applications andnetworks. The network is ill-suited to meet today’s applications’requirements.

The current network cannot deal with these challenges in theservices context, because of severely limited IPv4 address space.These challenges require the network architecture to provide abroad range of services. These services go far beyond the simplebest-effort forwarding paradigm of current Internet, so researcheshave been advocated of clean-slate network architectures. FINDprojects (Paul et al., 2011; Roberts, 2009) present completegrounds-up re-designs focusing on defining new service architec-tures. The SILO project of FIND divides into flexible services andmethods across the whole network and supports cross-layer. TheNetServ project of FIND aims to develop efficient and extensibleservice architecture in the core network to overcome the ossifica-tion. In comparison with FIND projects, the EU FP7 (Paul et al.,2011) projects are more concerned about the relationship amongdifferent interested parties and how to setup the service agree-ment and achieve the service integration from business level toinfrastructure level. SDN (McKeown, 2009) is an emerging net-work architecture where network control is decoupled fromforwarding and is directly programmable. Business applicationscan operate on an abstraction of the network with open APIsbetween the SDN controller and applications layers. Openflow(McKeown et al., 2008) is the first standard interface designedspecifically for SDN, providing high-performance, granular trafficcontrol. SDN matters to the cloud computing applications becauseit greatly reduces operational complexity and cost. Yet the archi-tecture was not scale and reliable, because of the centralizedcontroller. OpenFlow required a significant overhaul of somethingthat network operators are not likely to undertake in Internet.Content-Centric Networking (CCN) (Jacobson et al., 2009) treatscontent as a primitive. Accessing content and services requiresmapping from what the users care about to the network's where.However today's network still work in terms of host-to-hostconversations, so CCN could be deployed as an overlay whichmade its functional advantages available to applications withoutuniversal adoption. Moreover, a consumer asks for content bybroadcasting over all available paths, which is a high waste ofnetwork resources and not scalable.

A new network architectures should be designed based oncurrent network, otherwise it is bound to fail. Various versions ofEthernet are good examples of such backward compatibility. Theresearch on incremental architecture can be expected, and some ofthe ideas originally proposed as part of a new architecture can beretrofitted to the current Internet. Furthermore, once a newarchitecture has been identified, it is quite reasonable to identifyintermediate steps so that the current architecture can evolve intothe desired new one. In addition experience and tools developed

may prove to be very valuable for managing current Internet(Feldmann, 2007).

This paper proposes IPv6 Virtual Network Architecture (VNET6)with incremental network evolution. The goal of VNET6 is to adaptto a broad spectrum of application requirements. A key concern inthe design of VNET6 is that it should provide a collaborationbetween applications and networks. The collaboration acceleratesthe momentum of IPv6 deployment, as it can flexibly deal with theabove service challenges. The basic objectives of VNET6 are:

•

Flexibility: VNET6 is able to deal with different application-specific requirements at the same time and reduce the time-to-market for new applications.

•

Availability: VNET6 provides the network reliability for serviceavailability and the service guarantee with end-to-end quality.

•

Management: VNET6 is an easily manageable architecture withreliability and scalability for the networks and applications. Themanagement allows the applications to make efficient use ofresources.

To achieve these objectives, the proposed architecture com-bines and optimizes a set of technologies. Some IPv6 features fulfillreliability and simplify the management. The IPv6 technology isthe core of network layer. Moreover several innovative insights ofthe clean-slate thoughts are taken up and fitted back into VNET6such as the virtualization of network infrastructures (Schaffrathet al., 2009) and content distribution (Leighton, 2009). Further-more, the architecture defines a model to achieve the collabora-tion between networks and applications. This model is then usedto maintain the virtual collaborative environment including virtualconsolidation, virtual partition and virtual service.

VNET6 provides the collaboration between applications andnetworks. The virtual collaborative environment enables the layersto collaborate for the mutual optimization for both applicationsand networks, that is different from other service-oriented net-work architectures. Several proposals for service-oriented archi-tecture (SOA) (Josuttis, 2007; Newcomer and Lomow, 2004)explained how SOA can simplify the creation and maintenanceof large-scale web applications over the network. VNET6 networkarchitecture orients to different services requiring universal adop-tion. For adapting to a broad spectrum of application require-ments, VNET6 should be flexible, manageable and available for abroad range of services. These researches (Dutta et al., 2007;Greenberg et al., 2005; Huang, 2005; Peterson et al., 2005;Schulzrinne et al.; Wolf, 2006) presented the revolution of servicecentric architectures. Differently, VNET6 supports incrementalnetwork evolution with IPv6 and virtualization.

VNET6 provides the separate virtual networks over a commonphysical infrastructure based on IPv6. IPv6 implements some newfeatures such as anycast service (Hinden and Deering, 2006), IPv6Stateless Address Auto configuration (SLAAC) (Narten et al., 2007).Anycast service is a new networking paradigm supporting service-oriented addresses where an identical address can be assigned tomultiple nodes providing a specific service (Ata et al., 2004).SLAAC can configure automatically IPv6 address to support plugand play and it simplifies dynamic access management. These newfeatures fulfill carrier-class level reliability and simplify virtualiza-tion management.

Among current trends of virtualization (Sahoo et al., 2010) atevery aspect of computing (e.g., operating systems, servers anddatacenters), many aspects of network virtualization remain unex-plored Chowdhury NMMK (2009). VNET6 is different from othervirtual networks (Anderson et al., 2005; Chowdhuryand Boutaba, 2010; Carapinha and Jiménez, 2009). These virtualnetworks were no longer be necessarily based on IP and hadmultiplechallenges associated with the deployment of network virtualization

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in physical infrastructures. However virtualization as a mechanism ofthe abstraction of services and the isolation of resources wasimplemented above IPv6 network layer, where IPv6 provided thefeasibility of the deployment of network virtualization.

The virtual environment supports flexible and incrementalscalability and cost effective. VNET6 is a scale-out architectureusing commodity entities to build logical service entities at a low-end price. Currently this “scale-out” architectures can supportflexible, incremental scalability are common for computing andstorage (Vahdat et al., 2010). For example, The Google clusterarchitecture (Barroso et al., 2003) has been a highly successfularchitecture to provide web search service. VNET6 providesseamless integration of numerous network services onto existingindustry computing servers, storage facilities and legacy networkentities. VNET6 also offers different candidate network services toapplications, and adds the applications intelligence into the net-work. Indeed, VNET6 can be regarded as a smart service Cloudnetwork, rather than simple transport pipe.

To sum up, the above-mentioned challenges in the servicescontext would be turned into opportunities for IPv6 deploymentthrough the virtual collaborative environment. This paper exploitsvirtualization to enhance collaboration of applications and net-works, improve network efficiency and value through the extract-ing simplicity, flexible resource scheduling and application trafficmanagement. Furthermore, VNET6 can stimulate the developmentof applications.

The rest of the paper is organized as follows. In Section 2 wedescribe the basic definitions, sketch VNET6 architecture and thecollaboration model. The main topic of Section 3 is the virtualcollaborative environment analysis including virtual consolidation,virtual partition and virtual service. Section 4 discusses researchrelated to an example for the video service of VNET6. In Section 5,the conclusions and future work are presented.

2. VNET6 overview

2.1. VNET6 definition

Here we formally define the common terminologies and nota-tions that frequently appear in VNET6.

Services: A set S¼ fsig, where si is a service which is a well-defined and self-contained function performed on applicationpackets. A service is relevant to the application-specific require-ment, such as multi-path transport, bandwidth reserve, cachingservice, video compression and end-to-end flow control.

Each service addresses a separate atomic function based onservice level abstraction, so the service is more flexible and finer-granularity than current protocols which typically embed complexfunctions. Each service takes into account the application specificrequirements, network resource availability and other conditions.

Fig. 1. VNET6 a

We divided the services into two types based on the physicalresources dependence. si-Vp, where si relies on the resources ofphysical entities Vp. si becomes an available service unless theresources of Vp are available, then si-Vp is created. If a servicedoes not depend on the physical resources, it can become anavailable service after the software service function finishesregistration. Numerous candidate network services could beoffered to the applications after they become available services.

Different services can share the resources of physical entitiesfor an effective re-use of hardware as the demand for suchcapabilities evolves. Some services are the software service func-tions which reduce hardware complexity at the remote server. Theservices provide an enhanced degree of future proofing as servicesevolve. So the services can be rapidly scaled up and scaled down asrequired.

S-Profile: A set ScDS, it performs a set of transformations fromthe application to the network or vice versa.

S-Profile provides a way to group numerous applications theymeet to the same combination of services. The atomic services canbe selected to construct a particular S-Profile. Different S-Profilesneed to partition networks into multiple logical networks toisolate the traffic and allow traffic optimization within eachpartition. Therefore, S-Profile is the services integration for theapplications with the same requirements. Network is divided intoapplication views.

NIB: A weighted indirection graph Gp ¼ ðVp,EpÞ, where eachphysical entity in the physical infrastructure is a vertex vpi∈Vp,with s set of attributes Avp. Each physical link between two entitiesis represented as epi∈Ep, with s set of attributes Aep.

2.2. VNET6 architecture

VNET6 provides the network level abstraction according to theservice requirements of applications. This network architecturecomprises not only network resources, but storage and computingresources as well. Packaging network/storage/computingresources, each logical service entity carries out application-specific processing of services. Each end-to-end path carries outthe end-to-end flow services. Through separating the access fromtransport network, VNET6 allows ubiquitous access and flexibleservice level adjustment. A service cloud comprises reliable serviceentity, end-to-end service path and ubiquitous access over net-work infrastructure. Figure 1 shows formal definition of theterminologies and notations which are involved in VNET6architecture.

VNET6-C: A weighted undirected graph Gc ¼ ðVc,EcÞ, where Vc isthe set of virtual nodes vci and Ec is the set of virtual links eci. It isalso known as logical topology. VNET6-C is dedicated virtualnetwork to establish a service cloud for S-Profile over physicalinfrastructure. vci and eci also have their corresponding set of

rchitecture.

Fig. 2. VNET6 collaboration model.

D. Gu et al. / Journal of Network and Computer Applications 36 (2013) 1579–15881582

attributes Avc and Aec , respectively, that are provided when placinga service request for a VNET6-C.

VNET6 should provide flexible services for a wide variety ofapplications. It enables multiple heterogeneous VNET6-Cs tocoexist together on a single physical infrastructure. On the basisof the application level S-Profile, each VNET6-C can use arbitrarynetwork topology, resource reserve, routing and forwarding func-tions, etc. rather than best-effort forwarding. For example, Cloudapplications would benefit from the VNET6-C that can provideflexible on-demand provision of network and cloud capacity tocustomers.

VNET6-E: VNET6-E is a virtual node vci in VNET6-C. It is a logicalservice entity of VNET6-C. It contains more than one physicalentity. As mentioned above, vci has a set of attributes Avc . Avc isdefined as network attributes including port information, queue,computing resources and storage resources.

VNET6-E adds the applications intelligence into network ratherthan on two ends. VNET6-E is a service processing entity whichcontains flexible computing and virtual storage capabilities. More-over, VNET6-E provides reliability and scalability.

VNET6-P: A simple path Γ from vc1 to vcn, Γ ¼ vc1ec1vc2ec2…ecnvcn where vc1 is the start node of Γ and vcn is the endnode of Γ, vc1≠vcn. VNET6-P is an end-to-end service path inVNET6-C which is composed of ðec1eecnÞDEc . As mentioned ear-lier, eci has a set of attributes Aec that characterize it. Bandwidth,delay, loss, etc., are the example of attributes of a VNET6-P.

VNET6-P represents an association between S-Profile of flowand Aec . A VNET6-P adapts to a S-Profile e.g. end-to-end flowcontrol. A VNET6-P provides data flow delivery and controlcombined with the type of terminal, access type and transmissioncapacity.

VNET6-A: VNET6-A is the first virtual link ec1 in VNET6-P.VNET6-A has a set of attributes Aec. Furthermore, VNET6-A has aunique set of access attributes Aac including access type (e.g. cable,3G RAN or ADSL) and the terminal parameters (e.g. screen size,operating system or terminal cache).

VNET6-A can provide ubiquitous access services. It providesdata flow delivery and control according to the access attributes.

In summary, VNET6-C traverses the entire network and con-sists of VNET6-Es and VNET6-Ps. VNET6-P consists of VNET6-As.VNET6-A traverses the access network. So VNET6 has the fourbasic virtual components above the underlying network infra-structure. The network infrastructure consists of numerous com-modity physical entities which are maintained in NIB. Four basiccomponents have a unified control and management which isdesigned in VNET6 collaboration model.

2.3. VNET6 collaboration model

Nowadays services and applications are composed of a largenumber of functions combined together, that involve differentresources of the underlying network (Branca and Atzori). VNET6 isdifferent from current network model. The unified control andmanagement (UCM) publishes common atomic features as servicefunctions si and reusing these services in building and managingapplications as Choi and Kim (2008). The applications are providedthe network services after registration. So UCM provides thecollaboration between applications and networks. VNET6 stimu-lates the development of the applications over the network andincreases the network resource utilization.

VNET6 decomposes the collaboration model into three layers:applications layer, UCM layer and underlying network infrastruc-ture. These conceptual layers are illustrated in Fig. 2. They areexplained as follows.

Applications layer: Applications layer is the service consumer.This layer wishes to use the services after registering S-Profile. This

S-Profile is assigned to VNET6-Cs for specific applications. Appli-cations are easy to be built, maintained and scaled on VNET6-Cs.On the one hand, the applications register S-Profile with UCM,then require network infrastructure to perform services. On theother hand, the applications can easily collect information ofnetwork topology, manage traffic and optimize routing accordingto the services. For example, applications can dynamically requestnetwork bandwidth to adapt application traffic change. Thereforeapplications can manage the traffic on network since applicationsknow the best.

UCM layer: This layer is the service orchestrator to provide anemerging key feature of the collaboration between applicationsand networks. It unifies the control and management of applica-tions and networks.

First, UCM maintains all information including S-Profile, ser-vices and NIB. S-Profile can keep UCM apprised of the applicationsrunning within their networks and optimize the network services;Services provide current network services status; NIB also pro-vides the information about the access network, beyond providingapplications with network topology information. Through UCM,the network investments can be shared among numerous applica-tions. An application, in turn, will be able to offer improved qualityof services to its users. The information exchange as well as theinvocation of network services leads to cost reductions for thenetwork.

Second, UCM provides two-way information exchange. On theupward side, this layer provides open interface of XML schema(Biron and Malhotra, 2001; Fallside and Walmsley, 2004;Thompson, 2004) which describers the feedback of services. Onthe downward side, this layer provides NETCONF (Enns, 2006) tomake the communication with the network infrastructure andhandle the individual physical entity. So UCM provides thebidirectional interaction and the feedback loop between applica-tions and networks.

Third, the open interfaces of XML schema and NETCONF areintent-based interfaces (Rolland et al., 2007) for highlighting thegoal that a service is able to achieve. The intent-based interfacesavoid the mismatch of languages between the high-level applica-tions and low-level networks. For example, the applications requestthe service (si, multi-path transport, 2), where “si” is the service

D. Gu et al. / Journal of Network and Computer Applications 36 (2013) 1579–1588 1583

identity, “Multi-path transport” is the service intent expression, “2”is the service capability description. UCM do the matching andcomposition of load balance with two redundant links on theselected physical entities. So the intent-based interface is easieraccess to services by applications, and it provides the ability todynamically combine the implements of physical entities.

Last, UCM is responsible for virtualization in VNET6 and itcreates and manages virtual elements of VNET6-C, VNET6-P,VNET6-E and VNET6-A according to NIB and S-Profile. Moreovervirtualization provides the services abstractions to hide imple-mentation details and reduce complexity for the service consumer.

Underlying network infrastructure: This layer is the serviceprovider which provides services and resources to the serviceconsumer. It is composed of existing industry computing servers,storage facilities and legacy network entities.

After the physical entities of underlying network infrastructureregister physical resources with UCM, UCM compiles all these indivi-dual control requests into a single physical configuration. Then thislayer needs timely responses to the dynamic application-specificrequirements such as on-demand computing and storage facilitiesfor cloud computing applications, dynamic traffic management androuting optimization for the service consumer. So the underlyingnetwork infrastructure takes proactive steps to do service require-ments management and control in the collaborative environment.

Taken together, VNET6 provides the virtual environment ofextracting simplicity to enhance collaboration between applica-tions and networks. The networks can be adaptive to the applica-tion specified requirements, while the applications can utilize thenetwork infrastructure limited resources effectively.

3. The virtual collaborative environment

3.1. The collaboration processing overview in VNET6

In this section we describe the key issues to be resolved for thecollaborative virtual environment, which is implemented as thefollowing steps:

1.

After the physical entities register its resources in NIB, UCMprocesses the virtualized resource consolidation for the ser-vices in S. The resource virtualized consolidation can unifyservice scheduling for the flexible and scalable multiple serviceintegration.

2.

When the applications register S-Profile with UCM, UCMschedules multiple available service integration in S according

Fig. 3. (a) Virtual VNET6-E; (b) virtu

to S-Profile. The applications are aware of the actual capabilitiesof underlying network infrastructure, since UCM can provideapplications with the network topology information and net-work services status from NIB and services via XML schemainterface.

3.

If the scheduling fails, UCM notifies the applications of thereasons of the failure.

4.

If the scheduling succeeds, UCM processes the virtualizedpartition based on the resource requirements of the S-Profile,then UCM adds the annotation of “used” and configuresphysical entities for these services via NETCONF interface.Especially in the access network, the virtualized partition isimplemented based on both the S-Profile and the accessattributes of users. The applications are adapted to the cap-abilities of networks and terminals.

5.

UCM provides the flexible services and end-to-end flow manage-ment through the processing of physical entities associated withVNET6-Cs. At the same time, UCM can create multiple hetero-geneous VNET6-Cs with different S-Profiles to coexist on a singlephysical infrastructure. The applications are specialized differentservices for end-to-end performance, being aware of the actualcapabilities of the underlying networks and the actual trafficrequirements.

6.

When the applications unregister the S-Profile, UCM erases theannotation of “used” of the services for other applications’reuse.

7.

When the new physical entities register their resources in NIB,UCM provides dynamic resource consolidation and exchangeadditional information to invoke services. Meanwhile, UCMsupports on-demand provisioning if there are availableservices.

8.

UCM monitors the service state. If the service is unavailable,UCM deletes the unavailable service from NIB.

Next we would present the details of virtual consolidation (step 1),virtual partition (step 4) and virtual service (step 5) which are differentfrom other researches.

3.2. Virtual consolidation

Multiple physical entities could be virtually consolidated into avirtual entity by UCM. This virtual entity vci is called VNET6-Ewhich is the combination of services. The connection between twoVNET6-Es is a virtual link eci. Two ends of eci are two virtualinterfaces.

al consolidation.

D. Gu et al. / Journal of Network and Computer Applications 36 (2013) 1579–15881584

VNET6-E aims to allow isolated physical entities to become afully functional entity which consolidates multiple physical enti-ties’ resources. Figure 3 shows the architecture of virtual VNET6-Eand the collaborative procedure of virtual consolidation.

1.

Register: After the physical entities register their resources withUCM, UCM processes the virtualized resource consolidation forthe available services si in S, then records the resourcedependence si-Vp, where si relies on the resources of physicalentities Vp.

2.

Integrate resource: UCM records Vc-VP which is the relationbetween a logical entity vci and multiple physical entities vpi.Meanwhile, si-Vc is recorded, for the applications can easilyfind the logical entity to implement service si. UCM can easilyfind the underlying physical entities VP according to Vc and si.Multiple services are the combination of application servicerequirements.

3.

Create connection: Then these multiple physical entities arelinked logically. The connection of two physical entities islogical interface (e.g. tunnel, trunk) which is binding one ormore physical interfaces. Using this method, VNET6-E gainsconsiderable independence of the underlying links and canstep over many hops of physical entities.

4.

Configure: UCM assigns the basic attributes Avc of vci such asanycast address. Anycast address is sent to these associatedphysical entities vpi via NETCONF interface. Then these physicalentities configure anycast address.

5.

Monitoring and updating: UCM provides the monitoring andupdating of the VNET6-E state and the services state. Accordingto the service type, UCM manages these physical entities asseveral virtual boards intra the same VNET6-E. In Fig. 3, arouter, a server and a storage facility were virtualized VB1, VB2and VB3, respectively. These three physical entities were threevirtual boards within a single logical chassis. So VNET6-Esimplifies network topology and reduces management points.

VNET6 creates and manages the VNET6-Es which unify aresource pool with physical entities. VNET6-E can times thecapacity of single physical entity by multiple. It provides a fullydistributed and resilient data forwarding plane with more entitiesand bandwidth.

VNET6-E builds a cost-effective virtual entity from prevailingcommodity physical entities. The price per entity is effective interms of capital expenditure. More important, VNET6-E can reduceoperational expenditure of the human configuration and manage-ment burden. Adding current commodity entity into VNET6-E,VNET6-E can reduce overload, and deliver more bandwidth andresources.

Furthermore, the network, computing and storage resourcescan be integrated into a VNET6-E to satisfy flexible and complexservice requirements. Indeed, VNET6-E not only forwards servicepackets, but also contains flexible computing and virtual storagecapabilities, VNET6-E can aggregate, consolidate and transform

Fig. 4. (a) Virtual VNET6-A

data after receiving application dynamic requests. For example,VNET6-E can summarize data for the sensor network service,compress video stream for video service and on-demand comput-ing and storage facilities for cloud computing applications. SoVNET6-E puts applications intelligence into network.

VNET6-E which is a virtual entity of multiple physical entities isidentified with a same anycast address which is defined in IPv6addressing architecture. Anycast address is an attributes in Avc ofvci. Since IPv6 anycast aids in routing a user's service request to thenearest physical entity in VNET6-E, VNET6-E can improve networkefficiency. Ideally, the packet is sent to an optimal one in thegroup, where “optimal” can be defined minimum delay or largestthroughput according to the routing metric used by the unicastrouting protocol. In Fig. 3, UMC configures an identical anycastaddress to physical entity 1, physical entity 2 and physical entity3 to providing a same specific service.

Of course, VNET6-E would improve robustness of communica-tions. Anycast allows a sender to access at least one in a groupwhich shares the same anycast address. The anycast service is toseparate the logical service identifier from the physical entity. Theapplication can receive a specific service without knowledge oncurrent conditions in the physical entities of the same VNET6-E.When a physical entity goes down, the service packets can be sentto another physical entity.

UMC monitors and updates the service state in a virtual entity,rather than replicates and backups across different physicalentities. IPv6 anycast can simplify node-level complex protocoland need no longer worry about synchronizing service statesbetween active and backup nodes. Since all service states aremonitored and synchronized naturally in a virtual entity. Improv-ing its scalability and perhaps more importantly, IPv6 anycasthardens VNET6-E against denial-of-service attacks.

In summary, VNET6-E can provide flexible services, lower cost,simple management, nonstop resiliency and high availability.

3.3. Virtual partition

UCM processes the virtualized resource partition in VNET6-Eand VNET6-A. For each service si which processes in VNET6-E,UCM can efficiently implement resource partition according to theresource requirement of si. The resource partition procedure inVNET6-E is simple and successful, for the resources have beenreserved to si. Furthermore, for each service si which processes inVNET6-A, UCM can efficiently implement resource partitionaccording to not only the resource requirement of si, but also theaccess attributes Aec of users. To provide flexible access service,this section presents the details of the collaborative procedure ofvirtual partition in VNET6-A. Figure 4 shows the architecture ofvirtual VNET6-A and the collaborative procedure of virtualpartition.

UCM implements VNET6-A partition for different access usersand services.

; (b) virtual partition.

D. Gu et al. / Journal of Network and Computer Applications 36 (2013) 1579–1588 1585

1.

Plug-and-play access: To accelerate service deployment timesand time, plug-and-play access is provided in VNET6-A. WhenUCM discovers a user accessing to physical interface, then auto-configures network parameters including IPv6 address to theuser access device. Plug-and-play access is achieved throughSLAAC. The plug-and-play access is the first step when a uservisits applications.

2.

Create connection: After Plug-and-play access is achieved, UCMcreates a virtual link ec1 and record the access attributes aac.One user can dynamically creates multiple virtual links forflexible access services. VNET6-A extends the physical entity'shardware capabilities beyond the physical interfaces.

3.

Resource partition: A virtual link provides flexible resourceallocation according to aec and aac of ec1. The attributes aecare bound with S-Profile, and the attributes aac are bound withthe access type and access device. UCM negotiates and vali-dates the resources to make logical separation regardless of thegeographical and physical topology. VNET6-A provides flexibleuser-level services.

4.

Monitoring and updating: UCM monitors the access requeststates from a user, and dynamically updates the virtual links ofVNET6-A. A virtual link is created at the beginning of servicerequesting and is removed at the end of service.

VNET6-A provides ubiquitous access with adaptive service quali-ties from various devices and access networks. VNET6-A obtainsinformation about the access capability aac, such as access type,access link capabilities and the access terminal parameters. ThenVNET6-A dynamically creates different virtual links over the physicalnetwork for the user-level service requirement. Moreover, a user mayhave multiple different virtual links in series or in parallel to gainhigh quality of experiences. As shown in Fig. 4, User 1 has two virtuallinks with different access devices. Two virtual links of user 1 and avirtual link of user 2 belong to a same physical link.

Ubiquitous access is getting much prevalent. Some bottlenecksarise from access security. The identification of user is one of thesharpest issues. VLAN TAG which is bound with the account forauthentication in current access network is still an issue becauseof the limited bit width of VLAN TAG. To prevent the abuse of thesubscriber's account, VNET6-A binds the access virtual link ec1 andacquires sufficient information for authentication. The accessvirtual links which identify the access of user are not limited tobit width, so VNET6-A provides the secure ubiquitous access.

VNET6-A is simpler to operate than those that exit today. On oneside, numerous distributed physical access entities are represented asvirtual interfaces of VNET6-E, A virtual interface can be virtuallymanaged as part of VNET6-E. UCM simply manages a single virtualinterface, rather than a large of physical entities in traditional accessmanagement. On the other hand, SLAAC simplifies the aspects ofaddress assignment including generating IPv6 address via statelessaddress auto configuration, and the duplicate address detectionprocedure to verify the uniqueness of the addresses.

In summary, VNET6-A can provide the simple secure ubiqui-tous access service.

3.4. Virtual service

VNET6-C is a virtual service cloud which provides flexibleservices and end-to-end flow management based on the colla-boration between applications and networks. UCM providesintent-based interfaces for the collaboration as above.

1.

Negotiate services: The applications request services after theregister of S-Profile. The S-Profile is bound with the combinationof service requirements. The services have the intent expressionand the service capability description. UCM can do the matching

and composition of the implements of physical entities for theseservices of S-Profile.

2.

Create VNET6-C: UCM simply dedicated virtual network Gc toVNET6-C with the VNET6-Es. For each service si of oneS-Profile, UCM finds the VNET6-Es according to si-Vc whichhave recorded through virtual consolidation. These VNET6-Esare linked by virtual links Ec . So VNET6-C can use arbitrarynetwork topology Gc on the basis of the applications level S-Profile. Moreover, UCM can create multiple virtualized logicaltopologies VNET6-Cs over the unique physical one.

3.

Create VNET6-P: UCM dynamically creates VNET6-P to transportservice flows from the sender to the receiver. A simplededicated VNET6-P to guarantee service flows for end-to-endquality of service. VNET6-P is Γ ¼ vc1ec1vc2ec2…ecnvcn, where:• For each service si of one S-Profile, UCM creates Eci, whereEciDEc . si-Eci is recorded, the applications can easily findthe virtual links to implement service si. UCM recordsEc-EP which is the relation between a virtual link eci andmultiple physical links epi.

• ec1 has been created when a user visits applications. Theattributes aec were bound with S-Profile, and the attributesaac were bound with the access type and the access device.

4.

On-demand provision: UCM can provide on-demand provisionof the dynamic service requests for the applications, since theservices can be rapidly scaled up and scaled down as required.UCM can dynamically combine the resources for the on-demand services via the intent-based interface.

6.

Monitoring and updating: UCM provides the monitoring of theservice flow state to ensure flexible service-level requirementand enforces service policies. UCM dynamically updates theresource state with variable services. VNET6-P dynamicallyoptimizes the paths for the variable applications’ traffic.

VNET6-C is dedicated to virtual network Gc which is adapt tospecific service profile. The set of attributes Avc , Aec and Aac arebound with service profile to guarantee service availability. EachVNET6-C can use arbitrary network topology, resource reserve,routing and forwarding functions, etc. VNET6-C keeps the applica-tions running within their networks. Moreover, the applicationsare provided end-to-end connectivity according to the servicesrequirements, terminal and resource capacity by IPv6 forwardingand flow-scheduling. So VNET6-C provides services with highquality of experiences to users.

IPv6 is main protocol at the network layer while creating andconfiguring of VNET6-Cs. for example, VNET6-E is created by IPv6anycast service. VNET6-A is provided the configuration parametersby SLAAC. The forwarding plane of VNET6-C is based on the stateof IPv6 forwarding table. IPv6 implements some new features tofulfill carrier-class level reliability and simplify virtualizationmanagement.

VNET6-P provides multi-path service as an innovative way toprovide end-to-end service differentiation on IPv6 forwardingplane. VNET6-P allows the transport of multiple separate physicallinks at the same time. Moreover, VNET6-P provides resilience andavailability with multiple separate physical links. A virtual linkprovides multiple times the capacity of the physical link.

In summary, VNET6 can flexibly adapt to a broad range of theapplication’ service requirements. It can improve the quality ofexperiences to users, supporting available resource reserve,dynamic traffic optimization, end-to-end flow management, etc.

4. Example considerations for video service in VNET6

Given a significant amount of streaming bandwidth consump-tion over the Internet backbone (Liu et al., 2008; Singh et al.,

Fig. 5. Video service in VNET6.

D. Gu et al. / Journal of Network and Computer Applications 36 (2013) 1579–15881586

2012), this section describes and evaluates the video service of ourVNET6 prototype implements in order to assess the feasibility ofVNET6 architecture.

4.1. Simulation model under study

For the real-time video surveillance application of 720p HD video,the video's frame inter-arrival time was 25 frames/s and the fixedframe size of is 1280� 720� 24 pixels. This indicates the networkbandwidth w, where w≥528M≈ð1280� 720� 24� 25=1024�1024ÞM.

The video network model of VNET6 under study is shown inFig. 5. The underlying network infrastructure consisted of sixrouters, one server, one real-time video surveillance cameras andfour access users. The server was installed with the software ofUCM, the cache for video data and three software service functionsof s1 (bandwidth reserve), s2 (caching service bounded with thestorage resource of vp7), s3 (multi-path transport). The study wasperformed as follows:

UCM saved Gp in NIB after all physical entities registered.The S-Profile of the video service was registered, where

S−Profile1 ¼ fs1,s2,s3g. Then UCM created the graph Gc ¼ ðVc,EcÞwith Vc ¼ fvc1,vc2,vc3,vc4,vc5,vc6,vc7g and Ec ¼ fec1,ec2,ec3,ec4,ec5,ec6,ec7g for S−Profile1, where

•

vc5-fvp1,vp2,vp7g • v6-fvp5,vp7g • vc7-fvp4,vp6,vp8g

S-Profile1 was bound with the implement entities:

•

s1-fec1,ec2,ec3,ec4,ec5,ec6,ec7g • s2-fvp7g • s3-fec7g

Fig. 6. Video service in current architecture.

When user 1 requested video stream from real-time video server,VNET6 provided the services S¼ fs1,s2,s3g on the source pathΓc1 ¼ vc1ec2vc5ec7vc7. ec2 had the access attributes fFTTB,desktopg- (1280�720 pixels, 24 frames/s). ec2,ec7 reserved thebandwidth of 528M by dynamically binding with physical links.ec7 selected two available physical paths (Γp1 ¼ vp8vp6vp1and Γp2 ¼ vp8vp4vp3vp1) for multi-path transport.

Then the video data was sent back through the reverse path ofΓc1, vc7 sent two copies of packets to both available physical pathsof ec7. ec2,ec7 guaranteed video service with reserved bandwidth.Upon detection of user request, VNET-E directed this video streamto the local cache. vp7 processed the caching service for vc5, sincevc5 has integrated vc5-fvp1,vp2,vp7g. After vc5 sent the video

through ec2 which had the reserved bandwidth and the accessservices, the user 1 got available 720p HD video.

VNET6 provided intelligent connections between users andvideo contents, and VNET6 pushed the video stream to the net-work edge. User 3 and user 4 provided video with caching service.vc6 and vc7 sent back video data from local cache for these twousers. ec3 of user 3 had the access attributes fWIFI,smartphoneg-(128�120 pixels, 10 frames/s); ec4 of user 4 had the accessattributes fADSL,laptopg- (640�480 pixels, 24 frames/s). Forvirtual links which were bound with the user-level video transportrate requirements, VNET6 provided dynamic adaptive streamingover virtual link.

When a user requests video, anycast service can select theoptimal physical entity according to network conditions andlocation awareness. For example, user 2 requested video stream,vc5 found the video data from the cache of vp7, then selected thenearest available physical entity vp2 in fvp1,vp2,vp7g to send backthe video data. IPv6 anycast aided in routing a user's servicerequest to the nearest video server.

4.2. Results discussions

We provided the qualitative analysis by comparing with cur-rent Internet architecture and CCN, because there is no quantita-tive estimation method for network architecture. Despite manystudies have been made about large-scale network traffic (Jianget al., 2011), it is still a significant challenge to obtain accurateestimation of the network architecture. In order to compare andevaluate three network architectures, we identified six evaluationmetrics including flexibility, availability, management, security,increment and scalability. These six metrics covered the applica-tion requirements of networks and the essential aspects of net-work architecture.

This section describes the comparative analysis among Inter-net, CCN and VNET6 from the six metrics. Video service in Internetarchitecture is shows in Fig. 6. A major strength of CCN is that itprovided content distribution high efficiency in latest research(Jacobson et al., 2012).

•

Flexibility:Internet provides packets forwarding among nodes and pro-cesses the video packets at no higher layer than thenetwork layer.CCN provides caching service, multiple simultaneous connec-tivity, content-based security, etc.VNET6 provided bandwidth reserve, caching service, multi-path transport and ubiquitous access service, etc.To sum up, CCN and VNET6 provided more flexible servicesthan Internet.

•

Availability:In the current Internet, the real-time video server replicatedvideo stream by the number of requests. For example 10,000users have 10,000 video stream replications. 10,000 video

Fig. 7. Comparative analysis.

D. Gu et al. / Journal of Network and Computer Applications 36 (2013) 1579–1588 1587

streams �5M/stream¼50,000M traffic traversed the network.By comparison with Internet, we found that CCN and VNET6reduced video traffic across network even as user scale. CCNand VNET6 efficiently used physical bandwidth resources. Theyhad independent scalability of video content delivery functionswith in-network caching for video content. Video is cachedlocally and contents are streamed locally for new requests. So10,000 users can share the same video stream, one videostream �5M/stream¼5M traffic traversing the network. CCNand VNET6 reduced content replication to one stream acrossthe network for 10,000 users. Video was delivered from thelocal cache with much low latency providing. So CCN andVNET6 enhanced users’ experience. Moreover the video dis-tribution efficiency of VNET6 was as high as the efficiencyof CCN.In addition, VNET6 guaranteed non-stop video service availabilitythrough virtualization and anycast service. VNET6 provided end-to-end video bandwidth reservation, and dynamic adaptivestreaming over the virtual links which was bound with user-level requirements. However Internet forwards packets withoutcommunication guarantee. Backpressure between adjacent nodesin CCN is used to adjust resources sharing among continuous flow(Jacobson et al., 2009).

•

Management:In VNET6, managing the entire complex network and numer-ous services is an easy job due to extracting simplicity. Theabstraction of complicated services and numerous physicalentities hide implementation details to reduce complexity. Soit simply manages a few virtual elements, rather than tradi-tional management of a large of physical entities.VNET6 provided plug-and-play auto-management that is anintrinsic part of the network itself by IPv6 protocols, and thatsimplifies ubiquitous access services with high quality videoacross laptop, desktop and smart phone. So the management ofVNET6 was simpler than Internet.CCN maintains content store, pending interest table andforwarding information base (FIB) (Jacobson et al., 2009), whileInternet only maintains FIB. So the management of CCN is morecomplex than Internet.Taken together, the management of VNET6 was simplerthan CCN.

•

Security, increment and scalabilityAbout security, CCN provides content-based security manage-ment with content validation, managing trust, content protec-tion and access control, while VNET6 took little care aboutsecurity and only provided security access.VNET6 supported incremental network evolution with thevirtual environment and IPv6 some new features. It co-existsand is compatible with the existing physical network. To theopposite, CCN was a clean-slate network architecture.In terms of scalability, VNET6 provided flexible, incrementalscalability with multiple services integration and the resourceconsolidation of commodity network physical entities. The

number of VNET6-E of a specific VNET6-C could grow dynami-cally. The services could be rapidly scaled up and scaled downas required. But CCN was not scalable for a consumer asked forcontent by broadcasting its interest over all availableconnectivity.

•

Comparative analysisFigure 7 summarizes comparisons among VNET6, Internet andCCN against our six evaluation metrics. Each metric wasdivided into three levels: the superior, the middle and theinferior which is labeled with 1, 0 and −1, respectively.Comparative analysis confirmed that:• VNET6 was better than Internet architecture about flexibil-ity, availability, management and scalability. VNET6 couldovercome the challenges in the services context.

• VNET6 was better than CCN about management, incrementand scalability, and it was as good as CCN about flexibility,availability.

The video service prototype study illustrates its feasibility.However VNET6 has only limited visibility and control networkresources in VNET6-C for variable video service. The servicefunctions should be enhanced for more applications. The fine-grained collaborative services should be investigated. More-over, VNET6 should provide security management, especiallycontent-based security.

5. Conclusion and future work

The above prototype study illustrated its feasibility throughassessing the procedures correctness and the quality of experiencefor users. The VNET6 has achieved the basic objectives in Section 1.

Especially VNET6 can satisfy the service expectations of wideflexibility, simple manageability and high availability when theadvent of numerous applications. Because VNET6 can mitigatemany physical restrictions to provide separated virtual network forvariable services. These differentiated services meet the applica-tion specified requirements such as end-to-end connections guar-antees and service level resource management and control.

The above-mentioned challenges in the services context can beturned into opportunities for IPv6 deployment through the virtualcollaborative environment which provides bidirectional interac-tion and the feedback loop between applications and IPv6 net-works. The IPv6 networks overcome the challenges in the servicescontext, and the service applications help accelerate the momen-tum of IPv6 deployment.

This paper only proposed the conceptual network architecture.In future research, we will focus on the improvement of VNET6,especially how to provide fine-grained collaborative services, howto re-optimize IPv6 protocols for better services, and how toallocate crucial resources to the coexisted different VNET6-Cs.The further investigation of network virtualization, future networkand other collaboration technologies is also our concern.

Acknowledgments

Many thanks go to Dr. Xiaoyu Yang for his helpful discussionsand feedbacks. This work is supported in part by the DevelopmentProgram of China Next Generation Internet (CNGI). Thank ourcolleagues who contributed towards CNGI project for theircollaboration.

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