2.6 Industry impact on NFV
Interconnection methods of virtualised networks have been continuously studied since the appearance of Software-Defined Data Centres (SDDC). This includes a wide range of research domains including cloud computing, SDN, IoT and NFV.
Among these research domains, the research challenges are similar and overlap-ping, but they focus on different application domains. These research silos are perceived as a challenge for NFV, but also as a potential for having synergy effects across these research domains. An additional factor which brings an additional dimension to these research silos, is that the related work of NFV is not only ori-ginating from the academia but also from private organisations and the industry.
Hence, with respect to the research question (RQ-1) of identifying NFV intercon-nection methods, the related work is not only driven by academic contributions, but it is also driven by trends in the industry. In order to let this academic research have any impact on the society, it should be aligned with these trends.
ETSI aims to lead, consolidate and coordinate the work of NFV standardisation [7]. Different research and technology silos have tended to work independently or in parallel with different focus areas. However, since 2012, ETSI has released over 100 publications (Figure:2.10) aiming to have one common NFV standard. They have published consolidation, capability, requirement, architecture and specifica-tion papers and ETSI is now focusing on consolidaspecifica-tion and optimisaspecifica-tion. However, the publications from ETSI mostly include APIs for the NFV components and not network protocols or virtualisation techniques. This reflects the focus areas of ETSI, which primarily aims to interconnect both components and data centres by APIs and not by distributed network protocols. ETSI aims to describe the network services in an abstract language (i.e. NETCONF/YANG [30], TOSCA [65]) and to distribute this configuration between the NFV components located within or between data centres.
While ETSI focuses on interconnections by APIs, IETF and IRTF have a more network-oriented approach to NFV interconnections by focusing on standardising network protocols on the data plane. Their primary focus in an NFV context has been an SFC architecture with an interface between the network and the virtual-ised services (I2NSF [66]). Similarly to ETSI, standardisation organisation such as MEF [67] has envisioned the service perspective, while ONF similar to IETF focuses on network forwarding and network control. On the other hand, standard-isation organstandard-isations closer to the physical network layer, such as optics [68] or mobile networks [69], have a very specialised focus on how to interconnect the data centres. For example, 5GPP [69] focus on Software-Defined Radio (SDR) access networks and how to interconnect them across multiple service providers.
Figure 2.10:ETSI specifications [6]
They also envision new service concepts, such as network slicing [70], but their architectural concepts of interconnecting different domains have historically not been fully aligned with ETSI. ETSI focus on openness of multiple virtualisation techniques through overlay networks and standardising APIs. The 5G community is focusing on a uniform communication model between the operators.
A simplification of the main difference is that ETSI aims to use overlay networks when interconnecting to other operators, while the 5G community aims to use a common control plane and a common networking standard (MdO). These meth-ods correlate with the SFC interconnection methmeth-ods mentioned in Section 2.2.
These interconnection methods are perceived as two different strategies and can be defined as stratification strategies (Figure:2.11).
With respect to Service Orchestration (SO) and Resource Orchestration (SO), the different responsibilities of these orchestration layers are highly dependent on the top-level stratification strategy. Resource orchestration of a virtual network inside an interconnected single overlay network is naturally easier than adapting and con-verting between different network standards in different domains. However, an ad-ditional network overlay introduces network overhead and operational challenges.
In addition to having different stratification strategies, the different standardisa-tion organisastandardisa-tions also work with different use cases (with different terminologies)
2.6. Industry impact on NFV 37
Figure 2.11:Stratification strategies
which reflects their suggestions of interconnection points and interfaces between the NFV service providers.
As stated previously, ETSI primarily works with federation across NFVOs, while MEF works with orchestrating VNF services [67]. Additionally, the Telecom-munication Management Forum (TMF) [71] work with operational aspects and naming standards (TMF 633, 640, 641, 645, 653, 656, 677) [71], while the Next Generation Mobile Networks (NGMN) [72] and the 5GPPP [73] work with 5G use cases for NFV [74].
However, from June 2019, ETSI and 3GPP SA5 [75] are aiming to collaborate and incorporate the principles from 5G into the NFV standard. This also includes network slicing.
Additionally, the open-source community has been contributing to making NFV standards. Their agile development strategy of "code first", has resulted in a set of successfully NFV applications that uses different API standards.
ETSI aims to consolidate the actors in all these domains, where they aim to collab-orate with both operators, vendors, standardisation organisation, the open-source community and the academia.
When ETSI joined forces with the open-source community, the operators also gained more focus in adopting the ETSI architecture. Hence, the open-source community have been important contributors in connecting the real world and the operators to adopt NFV.
Open Source Management and Orchestration (OSM) [76] is now an ETSI-hosted project set to develop an open-source orchestrator for NFV. The NFV orches-trator ONAP (formerly OPEN-O) [77] is perceived as the competitor to OSM.
The competition and their different standards did split both operators and vendors.
European operators and vendors chose OSM, while Asian and North American vendors chose ONAP. In April 2019, the organisations join forces and are now working together towards a common NFV orchestration model. During the past years, there have been many similar consolidations of standardisation organisa-tions and the open-source community. MEF is collaborating with Opendaylight [78], while Opendaylight is chosen as the main SDN controller in Openstack [79].
Openstack has for many years been the leading open-source framework for cloud computing and they were also the origin to the leading open-source platform for NFV (OPNFV) [55]. Similarly, the NFVO system CORD [80] grew out of the SDN controller ONOS [81].
This stream of collaborations reflects how the different NFV research domains are merging. However, even if OSM and ONAP are now collaborating in the NFVO domain, the NFVI domain is more diverse. Historically, vendors had different in-terpretations of how to implement the ETSI specifications. ETSI, which aligned with OPNFV, defined the OPNFV platform as the NFVI standard for interoperab-ility tests. According to the interoperabinteroperab-ility tests from ETSI, most vendors are now compatible [82]. However, research challenges still remain related to the intercon-nections of NFVI infrastructures, such as isolating virtual services [83], which is also the research objective in this thesis.
In summary, ETSI tends to lead the work of interconnecting NFVI domains, and their work on standardising the APIs between different operators seems success-ful. However, their work on interconnected network domains is open for multiple models. The platform which tends to be most successful and also most used for interconnection test is the OPNNFV platforms. For interconnecting these different NFVIs, the flexibility and openness in the platform is acknowledged. Hence, this research aims to be aligned with both ETSI and the OPNFV platform.