This work has been performed in the framework of the H2020 project 5GTRANSFORMER
(Grant Agreement no. 761536) and EUB project NECOS (Grant Agreement no. 777067), which are partly funded by the European Commission. This information reflects the consortia views, but neither the consortia nor the European Commission are liable for any use that may be done of the information contained therei

Contreras Murillo, Luis Miguel

López, Diego R.

English

Universidad Carlos III de Madrid e-Archivo

This is a postprint version of the following published document:Contreras, L.M., López, D.R. (2018). A Network Service Provider Perspective on Network Slicing. IEEE  Softwarization:  A  Collection  of  Short  Technical Articles© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Universidad uc3m Carlos Ill de Madrid -1 ·Archivo A Network Service Provider Perspective on Network Slicing Luis M. Contreras, Diego R. López Telefónica Global CTIO Unit Introduction The feasibility of creating logical, full-functional partitions of network infrastructures (either physical, virtual, or a combination of both), known as slices, will permit network service providers to overcome the great challenge of forthcoming 5G services: how to support and operate different kind of services with very distinct needs onto the same infrastructure. Mixing services like enhanced Mobile Broadband (eMBB), massive Machine-Type Communications (mMTC) and ultra-Reliable and Low Latency Communications (uRLLC), altogether on the same network, makes quite difficult to define a common architecture capable of keeping the requirements of each of them in an ordered and structured form. It is much more convenient to think on segregating them on specialized partitions, designed and optimized for the type of service to be provided.  A second level of segregation, directly related to the business models of network service providers, emerges when considering how (and how many of) those slices are to be provided. In this respect, network slicing can be perceived as the next form of providing wholesale services. That is, it is connected to the allocation of specific resources per vertical customer or tenant. Both levels of segregation go in the direction of allocating physical or virtual resources fitted to the kind of service and appearing to be dedicated per tenant, guaranteeing the isolation among the allocated resources. Looking at this from a provider mindset, and taking into account the similarities with wholesale product offerings today, different situations can be considered here, leading to slices with different capabilities, specifically in terms of their management and control capabilities, and how much of them the network service provider hands over to the slice tenant:  • Internal slices, understood as the partitions used for internal services of theprovider, retaining full control and management of them.• External slices, being those partitions hosting customer services, appearing tothe customer as dedicated networks. In this case, a sub-sequent distinctionapplies:o Provider-managed slices, meaning that the provider keeps the full controland management of the slice. In other words, the customer merely canuse the network resources of the provided slice, without any furthercapability of managing or controlling them.o Tenant-managed slices, implying that the customer has full control of theresources and functions allocated. The tenant has access to a (limited) setof operations and/or configuration actions, and the provider justsegregates the infrastructure necessary for that purpose. It is worth notingthat we use here the term “infrastructure” in the broadest sense, that is,1including all network functions that the customer can deploy and use on the slice. It is clear that Tenant-managed Slices have to be allocated one per customer, since the customer directly controls it. On the other hand, for Provider-Managed Slices could accommodate different customers sharing the same kind of service in terms of service requirements (bandwidth, latency, number of handled sessions, etc.). Figure 1 graphically presents these different options, illustrating that while the orchestration capability always resides in the provider, the control of the slice or the service on top of such slice could be in the provider or in the tenant depending on the kind of slice as described above. Figure 1. Types of considered slices and control responsibilities Environments Facilitating Network Slicing Network providers are nowadays deploying cloud-like facilities (termed NFV infrastructures: NFVI) that will serve to host virtualized network functions (VNFs). An NFVI allows for deploying VNFs in a dynamic way that can be adapted to the specific needs of each requested service. In the case of Telefónica, those capabilities are based on UNICA [1], the global NFVI being deployed at all its operations. The overarching architecture of UNICA is based on cloud concepts to allow large-scale deployment across multiple sites, but also covers provider needs such as carrier grade performance, scalability, and operational capabilities.  Apart from the elasticity provided by network function virtualization, flexible steering mechanisms are needed to shepherd the traffic flows according to the expected service behavior. In order to address these requirements, network programmability (enabled by Software Defined Networking, SDN), and its integration with the function virtualization described above, are considered as the baseline pieces to approach network slicing [2,3] playing a central technological role in the control, management and operation of future telecom networks.  !!!"#$%&'" (')*)(+%,-./,01+123.4'5-./,0167680,09.:+123.4'5-./,01676;,<0,09.:+123.4%,=/04-/>3->/.!"# $%&'# (#)*+#","+-*./#*'0"+)0%*01*+/#*$%&'# ,"2*+/#*$#)3&'# &$ 0" +/#*+#","+-*45%+&(%# +#","+$ (#)*$%&'#6,2,(+#2 +0*,*7&"2 01*$#)3&'#8-*./#*()03&2#)'0"+)0%$ +/#*$%&'#9*:/&%# +/#*+#","+ '0"+)0%$ &+$ $#)3&'#-*;%&'#$ 10) &"+#)",% $#)3&'#$-*./#*'0"+)0%*01*+/#*$%&'# ,"2*+/#*&"+#)",% $#)3&'# &$ 0"+/#*()03&2#)-*!)'/#$+),+&0" (#)10)<#2=> +/#*()03&2#)2Challenges Both SDN and NFV are progressively being introduced on existing networks, presenting a number of challenges accompanying this technological transition [4]. Network slicing will add an additional degree of complexity. The fundamental aspect of network slicing is that each slice will behave as it was an actual, independent network. This main requirement of slice isolation constitutes the essential feature any network service provider has to support in order to offer such services to its customers. The degree of isolation achieved will be critical in determining the ability of a certain provider to address the different classes of slices discussed above, and how they can be requested and used by its customers. Taking this into account, from a provider perspective (extending [5]), a preliminary list of challenges are the following (without considering any particular order): • Slice operation: Each slice must behave as a dedicated network while sharingunderlying resources, physical and virtual. Monitoring and maintenancemechanisms have to be defined in order to show and abstract the properinformation for each slice customer. To this respect, external slices have a higherdegree of complexity since the information to be exposed, and the accessconstraints to it, have to be defined or even agreed between the provider and thetenants.• Scalability: In order to partition network resources in a scalable manner, it isrequired to clearly define to what extent slice customers can be served or not bya given slice. The application of different SLAs on the offered capabilities ofmanagement, control and customization of slices will directly impact thescalability issue. Two dimensions of scalability has to be taken into account. Onone hand, there is the dimension related to pure resource allocation andaccounting (including those necessary for satisfying protection and availability),directly related with the kind of service requested and negotiated with thetenants. On the other hand, a too much fine-grained offering of slices canprovoke an unmanageable number of control and management artifacts to beorchestrated by the provider, making it unpractical. Some kind of aggregation orgrouping will be needed for achieving tractability. Scalability can be muchimpacted by the number of external tenant-managed slices offered.• Arbitration: In order to resolve conflicts and to ensure negotiated service levels,some arbitration mechanisms are needed that can allow an efficient usage ofresources, preventing over-dimensioning. These mechanisms have to be in placenot only among the different slices being allocated on the same infrastructure,but within individual slices themselves (like the three main types described inthe categorization above), since the relation between customer and slice is notnecessarily 1:1 (as in the external provider-managed slices case). Arbitrationwill have to be applied not only for slice creation or customer activation, butalso (and more importantly) when scaling and/or failure events happen, soresources are properly (re-)assigned according to the applicable SLAs.• Multi-domain: Vertical customers could require no restriction in terms ofcoverage, service capability, resource constraints, geographical footprint, etc.,avoiding any potential limitation of the network provider with which they3maintain a commercial relationship as primary provider. This drives to the necessity of enabling multi-domain slicing, implying functional and commercial interfaces to be normalized for general adoption. • Slice planning and dimensioning: Over-dimensioning has been the normal wayin the past for avoiding any kind of congestion. With slicing the traffic sourcesand destinations become much less predictable, if at all. This is especiallyrelevant for the case of external tenant-managed slices, where the final decisionof where deploying sources and destinations (as well as some intermediatefunctions that could alter or modify the traffic profile) is on hands of the tenant.Proper planning, dimensioning and enforcement is needed to make sustainablethe transition to this new form of service, starting with an appropriate datacollection on resource usage, including most significantly virtual ones.• Orchestration: Slice-based services will not only require the communicationbetween different administrative domains but, what is more challenging, theintegration of different technology domains. The complete end-to-end nature ofslices involves distinct computing environments and transport technologies, andlinking them require from an open and consistent orchestration approach.Furthermore, the scenarios related to external slices will require mediationmechanisms to coordinate requests for the management platforms of thedifferent customers (in the case of tenant-managed slices) or the providerbusiness units (in the case of the provider-managed ones).• Business layer: The interaction with the vertical customers is key forunderstanding the needs of the service to be provided. Proper abstractions andtemplates have to be defined for ensuring the provision of a consistent serviceportfolio and their integration with the internal network management andorchestration. The support of the different slice classes described above require aconsistent set of abstractions at all planes.• Security: In any shared infrastructure, security is a key element to guaranteeproper operation, and especially a fair share of resources to each user. Slicecustomers must be appropriately authenticated, their rights enforced byauthorization mechanisms, and the operations they performed accounted for, sofurther auditing can be applied in case of any problem is detected. Beyond this,measures have to be in place to proactively detect and address active securityattacks, avoiding a security breach in one slice propagates into the infrastructureand/or other slices.• Slice aging: the same dynamicity and flexibility for the allocation of slices totenants applies as well to the time-scale on which those slices will beoperational. We can expect to have a mix of long- and short-lived slices co-existing on top of the same infrastructure. This fact will impact providers inseveral ways, from resource planning (slice demand forecast including trafficand resources to be consumed) to security (data preservation per tenant).These challenges are still a relevant area for research, as explored in projects like 5G-TRANSFORMER [6] and NECOS [7], and additional ones will likely be identified and described in the coming future. 4Conclusions Network slicing constitutes an extremely promising approach for the provision of network services, able to deal with the demanding 5G requirements, and to support new wholesale offerings. While leveraging recent but well-established technology substrates, such as NFV and SDN, seems a straightforward path to achieve network slicing, there are several important challenges that have to be addressed to make it operationally feasible for network service providers. While a complete list of the open issues related to operational network slicing is still subject for research, the most salient of these challenges have been introduced here, relating them to the fundamental isolation property. Acknowledgements This work has been performed in the framework of the H2020 project 5G-TRANSFORMER (Grant Agreement no. 761536) and EUB project NECOS (Grant Agreement no. 777067), which are partly funded by the European Commission. This information reflects the consortia views, but neither the consortia nor the European Commission are liable for any use that may be done of the information contained therein. References [1] Analysys Manson, “Telefónica’s UNICA architecture strategy for networkvirtualization”, white paper, July 2017, available at:http://www.analysysmason.com/telefonica-UNICA-architecture-strategy-for-network-virtualisation-report[2] J. Ordonez-Lucena, P. Ameigeiras, D. Lopez, J.J. Ramos-Munoz, J. Lorca, J.Folgueira, “Network Slicing for 5G with SDN/NFV: Concepts, Architectures andChallenges”, IEEE Communications Magazine, Vol. 55, Issue 5, pp. 80-87, 2017.[3] M.-P. Odini, “SDN and NFV Evolution Towards 5G”, IEEE Softwarization,September 2017, available at: https://sdn.ieee.org/newsletter/september-2017/sdn-and-nfv-evolution-towards-5g[4] L.M. Contreras, P. Doolan, H. Lønsethagen, D.R.López, “Operation, organizationand business challenges for network providers in the context of SDN and NFV”,Elsevier Computer Networks, Vol. 92, pp. 211-217, 2015.[5] N. Davies, P. Thompson, “Challenges of Network Slicing”, IEEE Softwarization,January 2017, available at: https://sdn.ieee.org/newsletter/january-2017/challenges-of-network-slicing[6] 5G-TRANSFORMER Project. http://5g-transformer.eu/[7] NECOS Project: https://intrig.dca.fee.unicamp.br/2017/09/05/necos-2-year-eu-brazil-collaborative-project-starting-in-nov2017/5

A Network Service Provider Perspective on Network Slicing

Abstract

Similar works

Full text

Available Versions

Universidad Carlos III de Madrid e-Archivo

Name not available