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CaON
Converged and Optical Networks Cluster
FP7 Future NetworksWhite paper
Date: 06/05/2023
Chairs:
Prof. Dimitra Simeonidou ([email protected])Sergi Figuerola ([email protected])
Co-chairs:
Juan Fernández Palacios ([email protected]) Andrea Di Giglio ([email protected])
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List of Contributors
Contributors Company/institute e.mail address
Dimitra Simeonidou UEssex [email protected]
Sergi Figuerola I2CAT [email protected]
Juan F. Palacios TID [email protected]
Andrea Di Giglio Telecom Italy [email protected]
Anna Tzanakaki AIT [email protected]
Nicola Ciulli Nextworks [email protected]
Andrea Bianco Polito [email protected]
Reza Nejabati UEssex [email protected]
Georegous Zerva UEssex [email protected]
Mikhail Popov Acreo [email protected]
Josep Prat UPC [email protected]
Xavier Masip UPC [email protected]
Marcelo Yannucci UPC [email protected]
Raul Muñoz CTTC [email protected]
Ramon Caselles CTTC [email protected]
Marcos….. Acreo [email protected]
Joan A. García-Espín I2CAT [email protected]
Tania Vivero Palmer TID
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List of AcronymsAPI Application Programming
Interface
CaON Converged and Optical Networks
CapEx Capital Expenditures
CD Chromatic Dispersion
CDN Content Delivery Network
DC Data Centre
E-NNI External network-to-network Interface
EPON Ethernet Passive Optical Network
FSAN Full Service Access Network
GMPLS Generalized Multi-Protocol Label Switching
GPON Gigabit Passive Optical Network
IaaS Infrastructure as a Service
ICT Information and Communications Technology
IETF Internet Engineering Task Force
IMF Information Modelling Framework
LTE Long Term Evolution
MAN Metropolitan Area Network
MIMO Multiple-Input and Multiple-Output
MTOSI Multi-Technology Operations System Interface
NDL Network Description Language
NIPS UNI
Network + IT Provisioning Service User-to-Network Interface
NMS Network Management System
OAM Operation and Administration and Management
OBS Optical Burst Switching –or– Operational Business Support
OFDMAPON
Orthogonal Frequency Division Multiple Access Passive Optical Network
OLT Optical Line Termination
ONU Optical Network Unit
OOFDM Optical Orthogonal Frequency Division Multiplexing
OpEx Operational Expenditures
OPS Optical Packet Switching
OSS Operation and Support System
PCE Patch Computation Element
PLI Physical Layer Impairment
POF(SI-POF)
(Step-Index) Plastic over Fibre
RACS Resource and Admission Control Sub-System
RDF Resource Description Framework
RN Remote Node
ROADM reconfigurable optical add-drop multiplexer
RWTA Routing Wavelength and Time slot Assignment
SDN Software Defined Networks
SDK Software Development Kit
SLA Service Level Agreement
SOA Service-Oriented Architectures
TSON Time-Shared Optical Network
udWDM Ultra Dense Wavelength Division Multiplexing
UHD Ultra High Definition
UPnP-QoS
Universal Plug and Play Quality of Service
VXDL Virtual eXecution Description Language
WSON Wavelength Switched Optical Network
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Index
1. Introduction..........................................................................................................4
2. Justification/Rationale..........................................................................................4
3. Technologies enabling the CaON reference model..............................................6
3.1. Optical network IT convergence.......................................................................7
3.2. Optical network virtualization..........................................................................8
3.3. Cross-layer considerations..............................................................................11
4. CaON Physical technologies in support of FI services.........................................12
4.1. Core................................................................................................................12
4.2. Metro..............................................................................................................13
4.3. Flexible and Elastic Core/Metro optical Networks..........................................13
4.4. Access.............................................................................................................15
4.5. Access/metro and in-building/home networks..............................................18
5. CaON Control and Management Plane Technologies in Support of Future Internet Services.........................................................................................................19
5.1. Control plane evolution..................................................................................19
5.2. Management plane evolution: From rigidness to programmable management...............................................................................................................22
5.3. Evolution in Optical Networks towards cognitive and self-managed networks and its impact on control and management planes....................................23
6. Energy efficiency and Green networking............................................................24
7. Standardisation...................................................................................................25
7.1. Optical data plane technology........................................................................26
7.2. Optical control plane......................................................................................27
7.3. IT and network integration.............................................................................27
8. References..........................................................................................................28
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Executive Summary
TBD….
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1. Introduction
This white paper exposes the key role that optical networks and its associated infrastructures have towards the success of Future Internet. It takes into consideration technical inputs gathered across different projects composing the FP7 CaON clusteri, and presents the main trends for optical networks research. These research topics are positioned with relevance to the CaON reference model. This is a reference architecture model agreed among the projects belonging to the cluster and reflects the high level architecture that the CaON cluster foresees for the Future Internet. This positioning paper aims at complementing the relevant Photonics 21 and Net!works white papers.
This positioning paper is structured as follows: it presents the rationale and trends of Future Internet with regards to optical networks, followed by an overview of enabling technologies for the CaON reference model. After presenting the reference model, the physical technologies with their control and management planes are presented. Moreover, some standardisation strategies are identified, together with the impact of energy efficiency and green IT.
2. Justification/Rationale
Optical infrastructure is the physical substrate that historically has enabled the wide deployment of the Internet and continues to be critical for Future Internet. Flexibility, transparency, capacity, low cost per bit, isolation capabilities and advanced provisioning services make optical infrastructure a key enabler for the evolution and convergence of Future Networks..
The Internet has become one of the basic infrastructures that support the World economy nowadays. In fact, networked computing devices are proliferating rapidly, supporting new types of services, usages and applications: from wireless sensor networks and new optical network technologies to cloud computing, high-end mobile devices supporting high definition media, high performance computers, peer-to-peer networks and a never ending list of platforms and applications. In the last years there has been a trend (and a requirement) for a convergence of the different networked platforms towards a unifying architecture or reference model for seamless end-to-end communication regardless of the device technology and access/metro/core infrastructure domain segmentation. Particularly, some of these different areas, technologies and innovations at the infrastructure level are going to generate a big impact on the evolution of our society. We can establish an initial differentiation between mid-term and long-term approaches. Being the former the convergence of IT & Telco towards cloud computing, with optimisation of interactions between applications providers, resource, service consumers, network operators and infrastructure providers (with SLA mapping); and the later the definition of new architectures as key area of basic research for the coming years with new technologies at the core, metro and access networks.
Emerging applications are entering the arena of telco services with an unprecedented end-user acceptance. Similarly than the Internet has settled into daily life, Cloud Computing is making its way towards becoming the invisible stratus on which companies base their IT processes and users get their content. From the network perspective, it means understanding
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traffic demands to adopt the technology combination that best fits its support. Video and Cloud Computing demands are stressing the network as never experienced during the past decade, and will be the drivers of the network infrastructure evolution roadmap (fig. 1).
Figure 1: Global consumer Internet traffic Figure 2: VM and physical server shipment evolution
Moreover, proclaims of the advantages of Virtualized resources over Physical ones are well known and can be found wherever in the Internet, e.g. resource usage optimization [1], saves on energy consumption [2]. The introduction of Cloud Services in a massive fashion entails new constraints that may be convergent with the ones that come from the distribution of contents among the network. Here is where the core network will adopt a key role in Cloud service provisioning. It may provide:
Connectivity capabilities for residential and business customers towards the DCs and the external Internet.
Highly reliable, low delay and high bandwidth demanding interconnections between the cloud/CDN DCs themselves.
Due to the wide range of final services and high traffic demand between users and providers Cloud and DCs infrastructures will have to adapt to unprecedented levels of elasticity and contain unpredictability. However, current core and metro networks are not ready for these new traffic demands and behaviour. Core transport is characterized by a variety of networks, technologies and providers. Metro networks, in charge of aggregating traffic from access nodes (e.g. DSLAM, OLTs, Nodes B, corporate, etc), are typically based on Ethernet Metropolitan Area Network solutions from different providers. Within this scenario, core network may make up a bottleneck. Strategically, core, metro and access networks operation and capacity should be adapted to new services demand, in contrast to current core architectures where the adaption to new services is mainly covered by over-dimensioning and over-provisioning (i.e. over-dimensioning in LANs and over-provisioning in WAN). To successfully respond to the traffic demands presented in the previous point, optical networks must support:
An extensive amount of requests from DCs while the rest of traffic remains unaffected. Bandwidth and QoS assurance between end users and DCs (i.e. real time applications). QoS enhancement (via better use of existing network and data center). Flexible networking services enabling on demand fast data transfers. High capacity and scalability Costs optimization (DC and network). Responsiveness to quickly changing demands and infrastructure customisation. Enhanced service resilience (cooperative recovery techniques).
The inadequacy of the current core architecture to fulfil these requirements (Error: Referencesource not found) evidences the need of the conception of a new architecture capable to enable flexible connectivity services, specially adapted to new requirements with reasonable costs. A
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key challenge for optical networks is the capability to perform automated and flexible connectivity services between end users and DCs. This network model is conceived to:
Accelerate service provisioning and performance monitoring. Enable on demand connectivity configurations (e.g. bandwidth) toend users. Optimize both converged infrastructure costs and energy footprint (e.g. consumption,
carbon footprint) Guarantee the required QoS (e.g delay, jitter…) for real time and video services.
Key requirements for a Cloud enabled networkConnectivity Service
Cost/ bitGuaran-teed BW
Guaran-teed QoS
RangeFlexible
BWAutomated Operation
BW beyond 10Gbps
Current Core Arch.
Internet (L3) LOW NO NO Global YES YES NOStatic IP VPN HIGH YES YES Global NO NO NOStatic L2 VPN MED YES YES MAN NO NO NO
Cloud Enabled Network
Flexible Connec-tivity Services
LOW YES YES Global YES YES YES
Table 1
3. Technologies enabling the CaON reference model
The CaON reference model (figure 3) presents a multi-dimensional, layered architecture for the convergence of optical networks and future technologies and services. The main conclusion from the CaON cluster is that the ICT convergence plays a key role at the infrastructure level. This convergence is the basis to bring innovation at upper layers and enable a real and powerful cloud networked infrastructure deployment where the optical network can dynamically react to different and new applications behaviour.
This is a bottom-up reference model, where the infrastructure and provisioning layers, together with cross-layer SLA and management, are the key focus for future research trends within the CaON cluster community.
The physical infrastructure layer covers from the core to the access optical network. Within the infrastructure layer we can identify the virtualisation capability. It provides a more flexible way to deal with infrastructure resource utilization by overcoming the multilayer and current network segmentation, and a whole new set of functionalities (flexibility and new dynamic provisioning services) that enables the convergence of optical infrastructures to support cloud services delivery. Moreover, it facilitates the emergence of new business models by enabling the entrance of new players. However, with regards to virtualisation there are still many research topics that need to be addressed and further discussed (i.e. how isolation is managed and the impact that non-linear effects have on it).
Man
agem
ent L
ayer
(s)
SLA
Laye
r
Physical Infrastructure(s*)Virtualisation Layer
Network Control Plane Layer(i.e. network provisioning layer)
Cloud/Service Layer(e.g. app middleware layer)
Application Layer(i.e. final consumers)
* = (s) to reflect network & IT and multiplicity of infrastructures
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Figure 3: CaON reference model
More particularly, the provisioning layer is focused on a control plane architecture that may provide a new set of functionalities at the infrastructure level, enabling:
Scalable multi-domain and multi-technology scenarios with open control planes and enhanced UNI’s interfaces.
Automated end-to-end service provisioning and monitoring between different network segments and operators with coordinated management planes.
Network resources optimization by integrated control of different network technologies (e.g. IP and optical).
Network/IT resources optimization by means of cross-stratum interworking mechanisms. Operation over virtual instances of the network infrastructure. Convergence of analogue and digital communications unifying heterogeneous technologies. Unified OAM mechanisms able to operate in a complex behaviour (multi-technology, multi-
domain and multi-carrier).
On top of the provisioning layer there is the service layer. It establishes the link between the network infrastructure and the applications (cloud service requirements). This is the layer where the network exposes its services, resources and capabilities, enabling:
Application to network interface: this interface may enable the request of new and advanced services from the cloud to the network control plane.
On demand services provisioning with advanced re-planning functionalities. Co-advertisement, co-planning, co-composition and co-provisioning of any type of network
resource and IT services (i.e. connectivity + IT resources at the end-points coordinated in a single, optimal procedure)
Enhanced Traffic Engineering framework for resource optimization, advance allocation and energy consumption, in support of energy-efficiency.
Implementation of network prototypes comprising the innovative data and control plane solutions designed along the projects, in particular, pre-commercial software (control plane, network-service interworking…) and hardware prototypes (sub-wavelength switching, multi-granular nodes, etc).
Industrial exploitation: Accelerated uptake of the future networks and service infrastructures enabling increased access capacity and flexibility, as well as cost and power consumption minimization for intensive bandwidth consuming applications and cloud services.
At the cross-layer level, the CaON reference model considers two vertical layers. These are the SLA layer, another interesting topic within the convergence approach, and the Management layer. The former takes into consideration the mapping of the SLA requirements from the application layer down to the infrastructure (virtual) resources. The later is in charge of extending management functions across the different sets of resources, including virtual ones, and layers in coordination with the control plane and the provisioning layer.
3.1. Optical network IT convergence
The IT and Telco convergence mainly deals with dynamic flexible behaviour of network infrastructures and the integration of their operation and management processes with the IT infrastructures systems and services. However, the end challenge is on the capability to provide application-aware infrastructure through a new and well-defined set of Network/Infrastructure Service Interfaces. Actually, the dynamicity of those applications and collaborative group environments require that such infrastructures are provisioned on demand and capable of being dynamically (re-) configured. Dynamicity is also necessary to optimize the resource usage and
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reduce the service provisioning time, which so far is still slow and manual compared to application service needs. In fact, these applications will continue to evolve in features, size and amount of customers, as the associated business requirements change. Thus, the availability, performance, security and cost-effectiveness of application-aware infrastructure remain critical, as they support business decisions and data in a fast-paced, economy-driven environment.
Current provisioning services over hybrid infrastructures (managed networks and IT), composed of both IT resources (i.e. compute and storage) and high capacity optical networks, need unified management and provisioning procedures. This means the usage of cognitive, flexible, elastic and adaptive technologies for core and metro optical networks, with dynamic control plane functionalities and programmability features, as those in Software Defined Networks (SDN) ,for the whole integration with the DC network infrastructures is a must. SDN gives owners and operators of networks better control over their networks, allowing them to optimize network behaviour to best serve their and their users needs. However, current disjoint evolution has ended up with totally decoupled solutions for each type of resource and infrastructure, those under the network operator domain and those under the DC administrator domain. Therefore, there is a key technical challenge towards this ICT convergence and hence, be able to optimize the (i) infrastructure sharing for lowering OpEx/CapEx costs, and (ii) the (dynamic) services and applications deployed on top of these hybrid infrastructures with energy efficiency considerations. In this context, convergence also considers the trend toward infrastructure resource virtualisation and federation, thus providing full flexibility at the infrastructure level.
3.2.1. Management and control planes convergence
Management and control planes convergence is required as a must for future-proof, and Internet-scale enterprise applications. Distributed applications, consuming resources spread all over the world, require DCs and network core/metro convergence in order to optimize the service workflow and overall performance for cloud computing. Dynamic provisioning of one type of infrastructure resources only considers part of the problem, and typically leads to a waste of resources due to over-provisioning, mostly in networks, and sharing limitations in all kinds of resource usage. It must be noted that, as time goes by, hardware is increasing its power (switching, computing, storage, etc.) and embedding degree, which means that a higher control in granularity is needed too, both at the network and IT level. In the end, the challenge is on providing a common and transparent infrastructure able to integrate different technologies and services, where virtualisation is not the end solution but an adequate technique for overcoming many limitations. Some future research considerations are:
Keep IT/Telco converged infrastructure provisioning service (IaaS) time at a minimum. Unified and converged resource description languages and frameworks. Multi-granular, cognitive, elastic, flexible and adaptive optical networks (e.g. hardware
configuration). Isolation and flexibility of circuit-oriented networks (using resource virtualisation). Definition of the impact of these new technologies on legacy business models. Inter-administrative domain issues between networks and DCs. Non-standard service provisioning (alien wavelength services). Carrier grade cloud and DC integrated infrastructure services.
3.2. Optical network virtualization
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As commented, current physical infrastructures are mainly constrained by the amount of resources they can deal with, and this has to be solved. New infrastructures will be composed of heterogeneous resources that allow the delivery of any type of services between different nodes. Resources like network elements, connectivity, storage and computation are those that take part as core elements of the physical substrate and enable the creation of cloud infrastructures. The challenge, however, is on the level of flexibility, optimization and transparency to deliver a service and the need to map the abstraction (virtual representation) of physical resources and network topologies with the applications and service requirements. No matter what the infrastructure is, it would be homogeneously controlled and managed to deliver any requested service. Virtualisation will help on overcoming the multilayer and current network segmentation. Thus, at this point is where network virtualisation will bring the envisaged flexibility for the network infrastructures.
Although many virtualization technologies exist for storage and computational resources, a virtualization framework for the network infrastructure is not yet available. This framework should provide the capability to virtualise the physical network infrastructure, federate administrative resource domains from different providers, and provide the needed open interfaces, APIs and SDKs to allow that control and management planes deliver any type of service; independently of whether the physical substrate is analogue (fix and radio) or digital based. Virtualisation has to provide the full capabilities to partition the physical substrate into virtual resources, or create a virtual resource from the aggregation of physical and virtual resources too.. One of the outstanding features behind virtualisation is isolation. All the virtual resources must be isolated from each other. It is because they will be concurrently managed and operated, and will share the same physical substrate. In that sense, Virtual Infrastructures (VIs) will consist of dynamic composition, interconnection and allocation of these virtual resources. Additionally, these VIs will offer its infrastructure capabilities as a service to third entities or control/management planes.
Actually, virtualisation will have a large impact in networking that is not restricted to the physical substrate. Its flexibility will allow and facilitate the deployment of new services at the control and management plane (higher layers), with new type of open interfaces, business models and relationships between entities. Moreover, the systematic and dynamic deployment of VIs will allow creating customized infrastructures for new cloud applications.
At the analogue domain, optical network virtualization it is expected to be a key technology for addressing future global delivery of high-performance, network-based applications such as Cloud Computing, DCs connectivity and UHD video media services, among others. An optical virtual network infrastructure would be composed of a set of virtual optical nodes and virtual optical links, over a shared physical substrate, interconnected and managed by a single administrative entity. Isolation and coexistence are the two most important characteristics of virtualized optical networks, while the existing layer 2 and layer 3 virtualization solutions, such as VLAN and VPN, respectively, take advantage of the digital nature of network equipments and transport formats. Unlike L2 and L3, optical network resources and transport formats are characterized by their analogue nature. Optical layer constraints, such as wavelength continuity and physical layer impairments (PLIs) differentiate optical and other network resources. Therefore, future research should take into account the physical characteristics of optical networks and its implication on optical network elements and transport technologies, and how coexistence of analogue and digital systems have to be provided.
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3.3.1. Resource description
The term resource should refer to all physical resources (network devices/physical links) used to provide connectivity across different geographical locations and IT equipment providing storage space and/or computational power. Therefore, a pure optical network resource, any other network resource or any IT resource should be considered as resources.. There is the need to have a Virtual Network/Infrastructure Description Language that allows a complete detailed description of virtual resources (Infrastructure/network/IT) as well as integrating the notion of timeline consumption.
Semantic resource description and information modelling framework are needed to define and implement models that can be used for the definition of optical, layer 2 or layer 3 networks and IT resources. GEYSERS, as a first step and in order to work with the resources and compose them, defines abstracted models that represent the corresponding resources as a set of uniform attributes, characteristics and functionalities while hides unnecessary characteristics from the resource itself [ABOSI09], as a continuation of the work done in PHOSPHORUS [WILLNER09]. By means of this abstraction process the resources coming from independent physical domains can then be used by the Network Control Plane and the Service Middleware Layer in order to provision their corresponding services on top of the resources. However, many topics need still to be analysed and covered in resource description, like elasticity aspects of virtual resources, QoS or complete isolation, among others.
3.3.2. Infrastructure description languages
An Information Modelling Framework (IMF) provides common information modelling tools in order to create homogenised resource data models and specify interfaces to seamlessly manage different kinds of resources. Thus, an IMF must cover the type of information that the data model should be able to describe, the relationships between different kinds of resources and the capabilities that can be exposed through interfaces. Some of the aspects that a data model must consider are: resource attributes (IT and network), virtual infrastructure description, energy and consumption, quality of service and security. Moreover, an IMF needs to support and facilitate basic data operations for abstraction, composition and partitioning, that is, all the virtualisation types. The result of the IMF consists then in a model supporting aspects related to physical location, access interfaces, QoS/QoE attributes, multi-layer technology description, time constrains and a description syntax (e.g. RDF/XML).
From the network point of view, most of the IMFs being used nowadays offer support for two existing description languages, the Network Description Language and the Virtual eXecution Description Language. Since an IMF may require flexibility and extendibility, semantic approaches should be adopted in order to describe the resources and facilitate their logical manipulation. The basic hierarchy of an information model should be built using the concept of a Resource as the top element. This concept can be a Device, a DeviceComponent or a NetworkElement. Basically this hierarchy enables to describe devices, their components and the network elements connecting these devices. Different types of device components exist, each one with different properties. Memory, processing and storage components can be used to describe the platform of an IT resource. Switching components can be used to describe switches or routers, while specific types of optical switching components need to be included to describe the specific properties that are required for the virtualization process of these optical components.
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3.3.3. Use case example: Nomadic virtual PC over optical networks
This is a use case that reflects the need of convergence between optical networks and cloud applications. Delivering a Virtual PC service to mobile commercial users is a task which requires having certain network parameters such as minimum latency, jitter or transmission (bandwidth) speeds at certain permissible threshold values. Note that when we refer to mobile Virtual PC service users we mean users who will demand the service from different locations, and not necessarily users who will be consuming the service while on the go (on a roaming basis). A user consuming this virtual PC service will only tolerate certain (low) delay/latency, which implies a need to have the VMs executing on the edge node closest to the user’s physical location for the service to be commercially feasible and acceptable. These conditions impose the need to physically move the VMs as quickly as possible from the previous edge node of execution, to the current one using the optical data plane. The time invested in the transfer will be perceived by the user as part of the “boot-up” time, and it has to be kept at a minimum. In that sense, current research within the optical network metro architecture as described in the MAINS project [add reference] may suit a variety of these novel services.
3.3. Cross-layer considerations
As a new step towards the convergence between cloud environments and optical transport networks, there is the need of an innovative interface between the Service Layer and an enhanced GMPLS-based Network Control Plane [GEYSERS]. This interface, called Network + IT Provisioning Service User-to-Network Interface (NIPS UNI), within the GEYSERS scope, enables active cross-layer cooperation for end-to-end service delivery.
The NIPS UNI aims at being a key enabler for the seamless and on-demand provisioning of the heterogeneous set of networking and IT resources associated to cloud networking services. The mechanisms offered to exchange cross-layer information about capabilities, availabilities, route quotations and QoS requirements will allow more efficient orchestrations of the global set of resources; in fact, network and IT resources can be jointly and automatically selected and optimized, thus better satisfying the requirements of distributed applications for tailored performances and reliability. The work done under the NIPS UNI specification, which defines both the semantics and the procedures for Service Layer and Network Control Plane inter-cooperation along the entire service lifecycle from setup to tear-down, will allow further research of cross-layer integration within the CaON reference model. In fact, it offers services in support of scheduled connections, cooperative or automatic selection of IT end-points, quotations for end-to-end connectivity, dynamic service modification, monitoring functionalities, and cross-layer strategies for coordinated recovery of IT and network services.
Traditional UNIs act as a demarcation point between network service providers and subscribers over which just connectivity services are requested, offered and monitored. On the other hand, the NIPS UNI may evolve towards an interface that widens its services to the aggregate composed of both networking and IT resources. In these terms, it becomes a logical interface that allows network service providers to offer customized transport network services, tailored according to the application requirements, to cloud providers.
This trend is also foreseen in other domains. In the MAINS project, focused on a new multiservice metro network architecture that allows the application/service layer to access sub-wavelength optical layer resources on-demand and at the granularity of optical packets and/or
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optical bursts, the control functionalities of the sub-wavelength data plane are implemented through a supervising sub-wavelength capable GMPLS control plane, which also exposes a unified Network Service Interface (MAINS Network-Service interface, MNSI). Through this interface, aligned with the standard OIF UNI 2.0 network services, the service layer interacts with the network control to reserve/configure connectivity services in the sub-wavelength transport plane.
4. CaON Physical technologies in support of FI services
The key requirements of innovative ultra-high bandwidth networks refer to scalability, flexibility, assurance of end-to-end quality of service and energy efficiency, beside reduction of total cost of ownership. In the data plane, current equipment and network architectures still provide limited scalability, are not cost-effective and do not properly guarantee end-to-end quality of service. Thus, the control plane has to define an end-to-end control structure that allows different technologies and domains to inter-work efficiently, incorporating virtualization of network resources. Based on these rationales the main objective for a future transport network is that it should be/offer:
Compatible with Gbit/s access rates. Equipped with a multi-domain, multi-technology control plane and provide Optimal
integration of Optical and Packet nodes. High scalability, flexibility and guaranteed end-to-end performance and survivability Increased energy efficiency and reduced total cost of ownership
To face the scalability and flexibility problems for future transport network and, in the same way, to guarantee a energy and cost savings, the approach of leveraging on architectures (in parallel to be aware of the technology evolution) seems to have some advantages since it can be shortly applicable and it can be also be compliant with legacy carriers networks.
4.1. Core
Main objectives of the Projects in the cluster dealing with core network evolution is the definition of a transport network architecture, complying with requirements on scalability, flexibility, end-to-end quality of service, energy consumption and cost, for both mid-term (based on: elimination of IP transit routers; use of integrated wavelength switching and packet transport) and long-term scenarios (further based on: multi-granular switching nodes; power efficient ultra high capacity packet processing). In fact, it is demonstrated that an important fractions of functions embedded in large-size routers are not actually used, represent the most important share of energy consumption and it is one of the first item of expenditures. The key areas of research for core network evolution involve the analysis of the feasibility of the different architectures by means of performance and techno-economic impact studies, aiming at network performance and cost. The assessment parameters are considering:
Reduction of energy consumption: Identify the best solutions to reduce the energy consumption of the telco’s networks. Efficient combinations of O/E components needs to be investigated.
Combination of best of transport technologies. Research, develop, analyze and validate optimum combination of L1(Optical) and L2(Packet Transport, OBS,…) transport technologies.
Control Plane for end-to-end service delivery. Pursue e2e services delivery across heterogeneous domains in terms of technologies (circuit transport networks and connection-
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oriented packet transport networks), control plane models (e.g. multi-layer/multi-region), OAM mechanisms, vendors and operators. The identified control-layer and the related control-plane architecture should be compatible with multi-domain and multi-technology scenarios, rely on a hierarchical path computation element (PCE) approach, implemented in a wider resource and admission control (RACS) framework.Enabling the virtualization of resources. Enable the virtualisation of resources, and allowing the cooperation among heterogeneous data-plane technologies to permit quick and low-cost introduction of new services independent of underlying transport platform.
4.2. Metro
A broad range of emerging services and applications (wide-range of multi-media, distributed applications such as Cloud, etc.) are driving the growing trend of network traffic with increasing demand for high bandwidth and flexibility. In addition, such applications require guaranteed multi-granular short-lived services i.e., from seconds to minutes with bandwidths from Mbps to hundreds of Gbps. In order to provide these services, a new subwavelength switching network architecture is required that can deliver dynamic access to transparent multi-granular flows as a guaranteed (no contention) network service.
Optical packet switching (OPS) and optical burst switching (OBS) have been proposed to support subwavelength services [1]. However, these techniques do not provide guaranteed bandwidth services. It is also worth noting that current approaches consider ring solutions [1,5] for metro. In that sense there is clear trend towards novel optical network solution – the Time Shared Optical Network (TSON)[6] – to deliver both highly flexible statistically multiplexed optical network infrastructure and on-demand guaranteed contention-free time-shared multi-granular services. In that sense, TSON supports traffic flows from any source to any destination in transparent optical networks for the metro region supporting the physical interconnection requirements. It is based on user/application-driven bandwidth service requests, centralized RWTA calculation, and one-way tree-based provisioning that allows for flexible symmetric/asymmetric multi-granular bandwidth services with the use of either fixed or tunable transceivers. It delivers contention-free optical switching and transport of contiguous and non-contiguous time-slices across one or multiple wavelengths per service. It also doesn’t require global synchronization, optical buffering and wavelength conversion, thus, reducing implementation complexity.
4.3. Flexible and Elastic Core/Metro optical Networks
Numerous studies have demonstrated and investigated the highly variable and complex nature of internet traffic. Uncertainty in traffic demands, granularity, geographic and temporal distribution may arise from the varied requirements of different applications, changes in customer behaviour, uneven traffic growth or network failures. As such, networks need to be able to cope with some level of uncertainty in order to provide an acceptable quality of service, e.g. low blocking probability. One way to deal with uncertainty is to overprovision network resources. However, this leads to inefficiency and higher costs. Another way is to equip networks with flexibility according to the type of uncertainty that needs to be addressed. For instance, dealing with uncertainty in the geographic distribution of traffic requires networks with the flexibility to route channels to different destinations. Similarly, the requirement for future optical transport and networks able to carry mixed bitrates, e.g. 10 Gb/s, 100 Gb/s, 400 Gb/s, 1 Tb/s and beyond, has triggered a great deal of interest in elastic optical networks. In
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such networks spectrum allocation is performed in a flexible manner, depending on the requirements of individual channels. For instance, it is possible to allocate contiguous 75 GHz of spectrum for 400-Gb/s or 150 GHz for 1Tb/s. Moreover, transport of low traffic with increased spectral efficiency is feasible by reducing channel spacing, e.g. 10 Gb/s with a 25-GHz spacing. In addition, it is possible to support bandwidth variable transmission, whereby the optimum bitrate for the required reach is used, which significantly increases network efficiency. Therefore, this additional flexibility enables matching allocated spectral resources to channel requirements, thereby providing efficient optical transport. However, technology limitations, e.g. 12.5-GHz spectral slot size, restrict the use of elastic spectrum allocation to entire wavelengths, i.e. 10 Gb/s granularity. For finer traffic granularities, several subwavelength multiplexing techniques have been proposed, such as optical packet switching (OPS), optical burst switching (OBS), orthogonal frequency division multiplexing (OFDM) and time-shared optical networks (TSON). It has been recently shown that the combination of elastic spectrum allocation and elastic time multiplexing may be used to provide extensive bandwidth granularities in the optical domain.
Elastic optical networking presents a number of challenges. Most notably, the mix of channels with high and low bandwidth requirements e.g. >1 Tb/s and 10 Gb/s, may give rise to spectrum defragmentation. Spectrum gets fragmented as channels are added and removed leaving behind non-contiguous empty slots. When a high bandwidth request arrives there may not be sufficient contiguous bandwidth to accommodate it, which results in blocking. Techniques for spectrum defragmentation involving relocation of existing wavelengths, e.g. by means of wavelength conversion, have been proposed. However, before a high-bandwidth request arrives it is uncertain which channels would need to be relocated. To support diverse traffic demands and a broad range of granularities, future optical transport networks may need to support a combination of transport functions such as elastic allocation, switching and resource defragmentation in space, time or frequency. Furthermore, the demand for these and other emerging functions operating on multiple dimensions, e.g. time, frequency, space, phase, etc., may be fluctuating or depend on the network region considered, e.g. metro, core.
The first demonstration of an elastic optical network based on OFDM transmission. Since then, a number of studies have investigated elastic networking showing significant gains in network mean traffic, required spectral resources , capacit], cost, etc. Other work has focused on the development of bitrate-variable transceivers and spectrum defragmentation. Recently, there have been important demonstrations on automated adaptive transmission and networking. In spite of the increasing popularity of elastic optical networks, there has been very little work focusing on elastic node and network architectures
In this context the concept of elastic optical transport is based on the ability to dynamically partition the fibre bandwidth into variable-size spectrum slots. The size and shape of each slot are usually tailored to the requirements of a specific channel or group of channels so that efficient transport across the network is achieved. This fine slicing and shaping of passbands is not accomplished by passive components, e.g. arrayed waveband grating (AWG). Instead, active components typically based on liquid crystal on silicon (LCoS) or micro-electromechanical systems (MEMS) are used. Elastic time multiplexing requires fast switching devices, e.g. ns switching time, in order to achieve fine switching granularity and high efficiency. Fast time switches are usually implemented with semiconductor optical amplifiers (SOA) or electro-optic materials such as LiNbO3 or PLZT. The combination of flexible spectrum switching and fast time switching technologies enables elastic time and frequency allocation.
The main objectives of future research in this topic should focus on:
Scalable and flexible data plane technologies
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Innovative transmission, switching and grooming technologies enabling transport beyond 1Tbps.
Control Plane for elastic optical networks
To design of new control plane solutions for scalable and adaptive flexible and elastic optical networks in order to support end-to-end connection provisioning and recovery services delivery crossing domains that are heterogeneous in terms of technologies and control plane interworking models
Node and network architecture for elastic optical networks
Design elastic optical nodes and networks based on the relevant advanced data and control plane technologies
4.4. Access
Next-generation of optical access networks are foreseen to provide multiple services simultaneously over common network architectures for different types of customers. In recent years, most studies are being focused on time division multiplexing passive optical network (TDM-PON) and wavelength division multiplexing passive optical network (WDM-PON). The TDM technology based on GPON and EPON and its future developments allow dynamic bandwidth allocation but complex scheduling algorithms between several ONUs are needed, therefore, through each time slot only one ONU can transmit or receive simultaneously information. Consequently, the performance of this technology is highly sensitive to packet latency and not transparent to other kind of traffic that shares the same link.
In the other hand, WDM-PON is able to deliver multiple services transparently to each ONU, due to each ONU can use a dedicated wavelength. However, WDM-PON isn’t enough flexible to dynamically allocate the bandwidth for several ONUs and transceivers, optical filters and other devices are needed for this type of network, increasing the cost of the solution and making it unfeasible for all type of customers. In contrast to previous technologies, the orthogonal frequency division multiple access passive optical network (OFDMA-PON) can transparently support various services, allows dynamic bandwidth allocation among services, in addition it has resistance to some dispersions effects like chromatic dispersion (CD), consequently the complete bandwidth can be divided into both orthogonal frequency-domain subcarriers and time-domain slots, in this way each ONU can be assigned one or more subcarriers in a given time slot. Mainly, the OLT in an OFDMA-PON system is able to support heterogeneous ONUs using a single receiver per PON port. In that sense, the ACCORDANCE projects enables a seamless OFDMA-based access network where all different Telco services are consolidated, allowing a full coexistence of fixed and wireless applications.
The benefit of this technology is based on the OFDM modulation format that also offers additional advantages, such as:
Allows using the spectrum with more efficiency due to the use of multilevel modulation formats like QPSK or M-QAM.
Simple to scale to higher constellations sizes and higher bitrates.
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Better chromatic dispersion tolerance: in OFDM, the speed at which each sub-carrier is modulated is less than the aggregate rate and with the use of a cyclic prefix can mitigate the effects of chromatic dispersion and achieve a greater reach.
High spectral efficiency, orthogonal sub-carriers without guard bands can be overlapped making it more efficient than FDM schemes.
OFDM is currently used in access networks over copper pair as xDSL and wireless (WiFi, WiMAX or LTE), so using OFDM in the optical network will simplify convergence between different technologies in the access network and could facilitate more efficient traffic management.
Thus, from telco point of view, although not yet mature, this technology is attractive compared with other fixed access technologies. Mainly due to its flexible architecture, its cost access system for the delivery of heterogeneous services, the high-speed that can be achieved, its high spectral efficiency and its powerful bandwidth granularity. Although several technologies for access networks are introduced below, the experience gained along the CaON projects brings some key topics to be addressed for next generation of access networks:
End-to-end low round-trip delay for multimedia communications. Access network scalability, in terms of connected users, BW and distances, sharing a limited
infrastructure, integrating radio-PON and providing an effective resiliency, as the network extends to a higher dimension.
Next Generation Access models: Open neutral network versus operator vertical model
4.3.1. Optical Orthogonal Frequency Division Multiplexing - OOFDM
The OOFDM technology roadmap can be divided into three major phases (fig 4).
Fig.4. Roadmap for OOFDM technologies (from ALPHA project, D4.5p).
4.3.2. Radio-over-fibre technology
Radio over fibre may be deployed in two application domains: Access networks for mobile telephony networks (GSM, GPRS, UMTS, LTE), and In-building and home networks for wireless broadband (WLAN, 60GHz, UWB, …) where steadily growing capacity demands are put on the wireless connectivity for communication terminals. These growing capacity needs per user can be solved in several ways: by decreasing the radio cell size, by increasing the transmission capacity per radio frequency channel, and by multiple antenna techniques (MIMO). Fig 5 presents an indicative timeline of RoF technologies networks.
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Fig.5. Roadmap for Radio-over-Fibre technologies (from ALPHA project, D4.5p).
4.3.3. Large-core Plastic Optical Fibres for in-building and home networks
The current conventional step-index POF (SI-POF) offers a solution for home networking that can be immediately used due to the existing commercial products (mostly for Fast Ethernet). POF is seen as a valid alternative to the electrical solutions, like Cat-5e/6a or coaxial cables. To the best of our knowledge, ALPHA [ref] has been the first project where a Gigabit POF transceiver prototype has been developed. For future developments, the power budget of the system could be increased in order to make the solution more robust, in particular working on the coupling condition between fibre and photodiode. Another area to investigate is the use of blue or green laser diode.
Fig.6. Roadmap for POF technologies (from ALPHA project, D4.5p).
The future roadmap expected for POF technologies is illustrated in Fig. 6, and is conditioned by the home networking market evolution. The success of POF technology in the in-building network segment will also depend on some factors that are outside an EU research project.
4.3.4. Resilient hybrid WDM/WDM-PON
This first network solution, developed in the FP7 SARDANA [ref] project, gracefully integrates the GPON optical TDM multiplexing, at a higher rate, with the optical WDM
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multiplexing in hybrid architecture. With this integration, the fine granularity and scalability of TDM combines with the huge bandwidth capacity and power efficiency of WDM. This technology is implemented over an alternative architecture with respect to the conventional tree WDM/TDM-PON, consisting on the organization of the optical distribution network as a WDM bidirectional ring and TDM access trees, interconnected by means of cascadeable optical passive Add&Drop remote nodes (RN). This type of technology aims at serving more than 1000 users spread along distances up to 100 km, at 10 Gbit/s, with 100 Mb/s to 1 Gb/s per user in a flexible scalable way. The ring+tree topology can be considered as a natural evolution, from the conventional situation where Metro and Access networks are connected by heterogeneous O/E/O equipment at the interfaces between the FTTH OLTs and the Metro network nodes, towards an optically integrated Metro-Access network.
4.3.5. OFDMA-PON
Another investigated promising PON technical solution is based on OFDMA (Orthogonal Frequency Division Multiple Access); this technology/protocols can introduce ultra high capacity, even reaching the 100Gbps regime, in extended reach optical access network architecture, as proposed in the European ACCORDANCE project [2]. OFDM is implemented through the proper mix of state-of-the-art photonics and electronics. Such architecture is not only intended to offer improved performance compared to evolving TDMA-PON solutions but also inherently provide the opportunity for convergence between optical, radio and copper-based access. Although OFDM has been used in radio and copper-based communications, it is only recently that is making its way into optics and is expected to increase the system reach and transmission rates without increasing the required cost/complexity of optoelectronic components. In that sense, ACCORDANCE hence aims to realize the concept of introducing OFDMA-based technology and protocols (Physical and Medium Access Control layer) to provide a variety of desirable characteristics, such as increased aggregate bandwidth and scalability, enhanced resource allocation flexibility, longer reach, lower equipment cost & complexity and lower power consumption, while also supporting multi-wavelength operation.
4.3.6. Ultra-Dense-WDM-PON
For longer term development, an alternative to the exploitation of the electrical-over-optical domains could consist of the direct intensive use of the optical spectrum, while minimizing the electronics requirements in terms of bandwidth and power consumption. This can be achieved by ultra-dense WDM multiplexing (udWDM-PON), with very narrow filtering techniques or by coherent homodyne detection. New developments in photonics and signal processing can enable this next-generation large-scale access networks based on ultra-dense wavelength division multiplexing (U-DWDM) targeting more than 1000 users on a single architectural platform with low-cost deployment. Pure optical OFDM is a step further in this direction.
4.5. Access/metro and in-building/home networks
The ALPHA project has developed solutions and respective roadmaps (fig. 10) for the cross domain control and management of access/metro and in-building home networks. The solutions and roadmaps have been based on the existing technologies with extensions and provide an evolutionary path for the development of integrated control and management in the domains of metro, access and home networks. These solutions address the formulated requirements for:
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Unified network management of heterogeneous networks (networks of networks) Context-aware networking Flexibility, scalability, efficiency and robustness (Intelligent and Controllable) Green networking
now mediumterm
longterm
+1 year +5 +100
Best effort, separate or no control planeAccess: f ixed access bandwidth, IP connectivity to accessHome: no central QoS controller in home
Prioritising flowsAccess: Reconf igurable management plane based on e.g. AON/Carrier EthernetHome: Prioritised access for in-home f lows through the gateway
Cross domain end-to-end provisioningGMPLS controlled NG AON accessIntegration of NG-PON with wireless AP (WiMAX/LTE)
Integrated controlUnif ied control plane for home and access, Full f ixed/mobile convergence
shortterm
very longterm
Integrated UPnP-QoS (or similar) and GMPLS
Per domain QoSAccess: Management based Std. Ethernet, XG-PON/10G-EPON, MPLS, and IP QoSHome: UPnP-QoS (or other CP), parameterised f low management
Figure 10 High-level roadmap for cross domain issues and end-to-end QoS provisioningin access and home networks’
In the access, the GMPLS control plane will be more advanced and the users can request for a specified bandwidth. UPnP-QoS or a similar control plane in the home will automatically request the necessary resources in the access network through the gateway. In the very long term, a unified and common control plane like GMPLS will act as glue and mediator between the user and the access network, and full fixed/mobile convergence will be supported.
5. CaON Control and Management Plane Technologies in Support of Future Internet Services
5.1. Control plane evolution
The Future Internet grow is enabled not only by the bare optical transport technologies with enhanced capabilities, but also by the control plane tools and procedures that can guarantee the related provisioning, monitoring and survivability of the involved resources and services.
The research in network control planes is currently focused on consolidating the control procedures adopted for the underlying optical infrastructure, and on extending a generalized (single-instance) control approach to include more and more technologies. Both objectives involve different architecture aspects with different degrees of maturity: they can range from more evolutive extensions to the control plane protocols when there is the need to incorporate new advances in optical data plane technologies (such as new Optical Transport Network multiplexes or grid-less networking), and can scale up to more extreme and demanding interactions between the control plane and the network service layer (e.g. the cloud) for controlling new types of enhanced connectivity services (i.e. beyond the point-to-point). Additionally, since optical networks represent the core substrate responsible for inter-carrier data transport, other key research topics addressed in this area include possibly standardized multicarrier and multivendor control solutions to make more effective and open (i.e. vendor-
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independent) the current implementations. Some of the mainstreams in the current control plane evolution, in decreasing order of importance and compelling requirements, are:
Opening the control plane domains towards true multi-vendor and multi-carrier scenarios Decoupling of the optical transport from the control plane(s) More flexible and powerful User to Network Interfaces (UNI); i.e. equipping the control
plane with more advanced interfaces to external end-user “systems” (e.g. clouds) for any type of bandwidth-on-demand provisioning service, and above all seamlessly integrated with the service layer workflows
5.1.1. “Opening the CP domains/systems” for true multi-vendor and multi-carrier interactions
After many attempts for inter-vendor interoperability through standardized protocol extensions (IETF), also supported by industry-driven Implementation Agreements (OIF E-NNIs and UNIs), the issue of multi-vendor equipments within one operator’s network is still unresolved, above all in case of multiple switching technologies. Several reasons contributed to this limitation: primarily the possibility offered by the current standards for different interpretations of complex procedures, which led to a diversity of deployment options by vendors and different degrees of compliance for implemented features; then, the different pace of market availability of specific technological solutions by a single vendor (e.g. ROADMs and WSON equipments under GMPLS control) with respect to the slower consolidation of the related reference standard modelling and control procedures. Both these causes led to the proliferation of many proprietary (vendor-specific) extensions and different equipment behaviours, above all in the optical domain; subsequently, a sort of “protected market-niches” for vendors has been created, as they can deliver their systems as highly integrated “all-in-one black boxes” (i.e. bundles of control and transport plane components, possibly extended to the management plane). The limitation on control plane openness is further complicated at the inter-carrier interfaces, where many other issues needs still to be solved; for example, the definition of reference mechanisms to dynamically establish trust relationships among carriers is still undefined, as well as technology-agnostic signalling procedures and service semantics (e.g. for QoS) that can ease the cooperation among carriers. Similarly, there is no agreement on possible reference model(s) for sharing more detailed Traffic Engineering topology information, that can provide data beyond the rough endpoint reachability but still preserving the confidentiality of the carrier’s internal infrastructure.
A sibling challenge in this context is the increasing interest by carriers to operate multi-region/multi-layer equipments (i.e. supporting different switching technologies), either by one single vendor or by multiple ones, under a single control plane instance. This challenge is relevant for both homogeneous technology networks applying proprietary control plane extensions (e.g. for WSON GMPLS), and for heterogeneous technology networks (e.g. MPLS and GMPLS). Nowadays, network operators are often forced to design their control domains that directly map one specific vendor technology, thus interfacing to “black-box” GMPLS systems at the management plane and with limited functionalities. The evolution of the control plane architecture should allow a more in-depth control of the control plane processes, in particular for what concerns the route computation and the resource allocation policies.
A potential approach to this problem area is in researching modes for an effective “splitting of the control plane architecture”, i.e. moving some of the intelligence out of the GMPLS systems towards the Operation and Support System (OSS). Key rationale for the split approach
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is the possibility to more strictly correlate the routing decisions taken by the control plane with the systems where the operators set and manage their Traffic Engineering policies (e.g. for provisioning and planning). The bridge between the enlarged OSS “brain” and the GMPLS “arm” is provided by the Path Computation Element (PCE) architecture, both in terms of established and developing standards (e.g. hierarchical PCE).
The GMPLS and PCE architectures are powerful and flexible enough to allow throttling the boundary between the “arm” and the “brain” according to a variety of splitting points. For example, an interesting solution for network operators who need self-defined procedures to route circuits across their network is to maintain a centralized paradigm for the actual service provisioning, by means of a Network Management System augmented via a stateful PCE (usually referred to as the “nominal wavelength service provisioning”), while using the distributed GMPLS signalling and routing for any subsequent fast recovery mechanisms.
5.1.2. Decoupling of the optical transport from the control plane(s)
Another possible application of the “split architecture” concept can be the integration of devices by different vendors in a single control framework. In this case, the splitting point can be much lower in the architecture, i.e. right above the node hardware and the related node agent. The key goal is to decouple the control plane implementation and procedures from equipments, with the main rationale of “moving intelligence out of the box”, and making it vendor-independent. In this perspective, this “external” control plane is the unifying glue for provisioning, recovery and traffic engineering procedures across different vendors within the same operated network. This approach relies on the assumption that vertical interoperability between the vendor-independent intelligent entity and the node devices is more streamlined with simpler interfaces (low level operations and application programming interfaces) and based on having, for example, unique or centralized points of deployment. One of the potential enablers in this research area is the popular OpenFlow protocol and its Software Defined Networking (SDN) framework. The major applicability areas for OpenFlow are currently the connectionless IP or MPLS-controlled networks, i.e. it is confined at the edge/aggregation (from campus up to metropolitan networks); however, there is an emerging interest towards developing its adaptation for circuit switched networks, and in particular for wavelength switched optical networks.
Despite of the technical impacts of the aforementioned “opening” and “splitting” trends, the separation of intelligence layers (“brain”) and convenience layers (“arm”) can also generate a business impact. In fact, they allow traditional third party players (e.g. software houses, stack vendors) and network customers (network administrators, but also Over-The-Top with large DCs and network operators) to participate actively in network operations and control, with the possibility to introduce new business actors and market dynamics.
5.1.3. Enhanced User to Network Interfaces (UNI)
Network operators have often been traditionally “hostile” towards dynamic UNIs, motivating this approach with the increased management complexity that results from the injection of customer-driven states (i.e. circuits) within their network and not under their direct control. Nevertheless, many emerging end-user systems require a better integration with the network provisioning procedures for on-demand and tailored connection services. Examples of these
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systems are cloud computing and Service Oriented Architectures (SOA) at large, which all rely on the network as a vital commodity and could highly benefit in treating it as an integrated resource within their orchestration processes. An ever-increasing number of distributed (super-) computing applications have highly-demanding requirements for dynamicity and flexibility in network and Information Technology (IT) resource control (e.g. automated scaling up/down), but their network service(s) is still treated as “always-on” and much more static in nature. Their application layer is unable to exploit the automatic control potentialities of the current optical (and not-optical) network technologies, thus resulting in inefficient resource utilization in the network, above all in case of fault recovery. This all points towards a network interface beyond the traditional UNI, and specifically towards Cloud/Service-to-Network interfaces with generalized semantics to integrate the characteristics of both IT sites/resources and network nodes (i.e. resource types, capabilities and availabilities, sites, attached services, capabilities and capacities of network, computing and storage elements, etc.). These more powerful interfaces should go closer to the cloud “way of thinking” about the network resources (of which the circuit is just the ultimate service instantiation), and support a number of advanced components, such as workflow descriptions, interaction properties, Service Level Agreements / Specifications (SLAs/SLSes), AA credentials, security contexts and accounting models.
5.2. Management plane evolution: From rigidness to programmable management
One of the main roles of Network Management is to ensure that the services provided by the network are offered to the clients with the desired level of performance, quality, and availability, usually based on a Service Level Agreement (SLA). Typical functions of network management are network provisioning, fault management, and performance monitoring, which are handled by Network Management Systems (NMS’s) that embed the capability to be customized to the different network equipment. Unfortunately, the overall set of management functions have been developed mainly on a per layer (network technology) basis. Thus, IP networks are typically managed through customized systems and individual tools, such as HP OpenView, IBM Tivoli, OpenNMS or Nagios. However none of these tools provides support for all potential providers’ needs and requirements, mainly because of the lack of programmable features, the lack of well set standard protocols for network device configuration, the lack of consensus around the preferred protocols and especially in terms of defining uniform data models, the high cost of commercial tools and the limited capabilities of the open source tools, what all in one also conducts to multiple interoperability issues between the IP network management systems with other management systems. On the other hand, the transport network is dominated by NMS’s particular to each vendor, where MTOSI appears as the interface to communicate in a standard way to different NMS’s. The main limitation on a Transport Network Management System is certainly the level of integration of management capabilities for devices that operate at different layers than the Transport System. Thus, the management of a typical operator’s network with many layers is based on separate ecosystems composed of different NMS’s and isolated tools, without easy interaction between them. In fact, the inter-relation between different layers is kept by in-house systems and databases that are hard to develop and maintain. Moreover, operations involving several layers are full of manual steps and end up in long and costly processes. This isolation leads to high operational costs, lack of interoperability and a continued need of upgrades in different systems, what definitely drives to a non-desired management scenario, hence requiring innovative solutions to optimize the overall network management process.
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In order to reduce the complexity of managing a network with multiple layers, two basic directions can be followed, namely simplification and/or coordination. The former aims at reducing as much as possible the complexity of the network by a flattering of the layers, while the latter refers to the development of tools that can interact with the existing network management systems at the different layers so as to make them work in concert. Any of these approaches requires extensive research to face the following challenges:
Interoperability between different NMS’s. Lack of coordination between layers (L1, L2, L3). Lack of standards and lack of consensus on interfaces and protocols, especially in terms of
defining uniform data models (for NETCONF, MTOSI, etc). The need to reduce the complexity and duplication of network devices and roles. The need to reduce manual and error prone intervention as much as possible. Lack of programmable features allowing providers to compose and orchestrate a set of
operations as a result of an event or a pre-defined policy in the network.
5.3. Evolution in Optical Networks towards cognitive and self-managed networks and its impact on control and management planes
Next generation optical networks will progressively deploy cognitive technologies, becoming cognitive optical networks. In short this term refers to networks that are able to learn, optimize and adapt themselves in reaction to state changes with little to no (operator) intervention. Clearly, the adoption of such technologies will have strong implications and impact on the data, control and management planes. It is noteworthy that Cognitive Optical Networks are becoming feasible thanks to the adaptive capabilities of both hardware and software components. Specific examples of dynamic adaptation involve optical transmission (with software-defined /cognitive transceivers with learning-capabilities) as well as optical transport (with cognitive framing and encapsulation) and optical switching (with self-flexible and adaptive on demand switching, leveraging the new grid-less spectrum management paradigms and approaches). Current and in development technology capabilities, such as format transparent wavelength or signal format conversion, regeneration or network-wide optical frequency/time/phase determination, will support the realisation of such cognitive functions. Moreover, hardware programmable elements could be also deployed to turn state-of-the art optical modules into cognitive-enabled optical system.
Further research and development should be focused on developing an open platform to dynamically re-purpose, evolve, self-adapt and self-optimize functions/devices/systems of the optical network infrastructure. An open platform for these optical/opto-electronic technologies would allow for environment-aware, self-x systems that can change any parameter based on interaction with the environment with or without user assistance. This platform would need to interact with both the control and management planes, potentially requiring either adaptations/extensions of the current framework or even radically different new approaches. New control and management plane architectures, protocols and algorithms should support highly flexible cognitive future optical infrastructure in a heterogeneous optical environment (i.e., an environment where the cognitive capabilities of its components is heterogeneous). In particular, research on cognitive control and management plane should be carried out to enable
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network-wide infrastructure dynamic self-adaptation, self-handling across heterogeneous systems, and should target both a) a framework that considers optimized multi-dimension (frequency, time, space) resource allocation, control and provisioning with self-healing and evolvable operations; and b) evolvable and open control plane platforms based on modular structures with environmental-awareness utilizing a mix of self-x or user-x controls (i.e. driven by the user or driven by the network in the normal course of its own cognitive capabilities). This research should provide a balance between minimal control and management overheads and yet deliver a trustworthy environment of multi-operator, multi-domain contexts is of critical importance.
6. Energy efficiency and Green networking
The steadily rising energy cost and the need to reduce the global greenhouse gas emissions have turned energy into one of the primary technological challenges. Information and Communications Technology (ICT) in general and optical technologies in particular, are expected to play a major active role in the reduction of the world-wide energy requirements. Indeed, recent studies show that ICT is today responsible for a fraction of the world energy consumption of about 4%, a percentage expected to double in the next decade. This evolution is illustrated in Error: Reference source not found [1], [2], where the reported data are based on a ‘business-as-today’ scenario, i.e. assuming that energy-efficiency efforts from industry, regulation and consumers will remain similar to these of the past years. Error: Reference sourcenot found also shows that there is no specific sector dominating the ICT power consumption, indicating that the need for energy-efficient solutions is relevant to all ICT sectors, spanning from DCs to network devices and to users appliances.
Figure 3 – Estimation of ICT energy consumption evolution
Currently, access networks are responsible for a major part of the network power consumption, as access related devices, although consume less power than those in the core network, are deployed in much higher quantities. To date, fixed access networks are mainly implemented, by copper-based technologies such as ADSL and VDSL. However, to address the rapidly increasing broadband access penetration and the new and emerging services, access technologies such as fibre to the X (FTTX) or even fibre to the home (FTTH) are becoming available to the end users. This adoption of energy efficient fibre based technologies is expected to limit the energy consumption in the access network segment despite the heavily increased capacity. Recent studies (e.g. [3]) also predict that the power share of the metro and core network segments will grow rapidly. This is due to the dramatic increase in the traffic expected to be supported by these network segments and to the fact that although they deploy energy
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efficient optical transmission technologies, they rely heavily on traditional electronic devices for switching and routing functions. Electronic devices consume high power and their consumption increases in a nonlinear fashion with the bit rate [4]. It is therefore critical that energy efficiency considerations are applied in the design, implementation and operation of these networks.
Optical networking can play a key role towards the support of energy efficient and hence sustainable future ICT solutions. The level of energy efficiency that can be achieved is very much dependent on the specific architectural approaches that will be followed, the technology choices that will be made, as well as the use of suitable planning/routing algorithms and service provisioning schemes. In this context, it is also important to design and operate optical networks taking into consideration the details of the services and applications that they support as well as the end devices they interconnect, as considering the relevant specificities and constraints can have a direct impact on the overall energy efficiency of the infrastructure.
More precisely, at the equipment level it is important to assess if, when and where optical technologies can be more energy-friendly than electronics, not only considering new or enhanced low-power devices but also fully re-designing network node architectures to exploit at best optical component features. Hybrid opto-electronic design can be an important asset especially in the medium term to also ensure graceful upgradeability. In terms of network architectures two strategies should be considered: to gracefully upgrade current infrastructures on one hand and to design new clean slate network paradigms on the other hand. This includes re-discussing the bandwidth efficient but energy hungry packet switching paradigm vs the circuit or burst switching techniques, which seem better suited for optical technologies, and understanding the trade-off between lightpath provisioning compared to hop-by-hop electronic switching. Improving the engineering practice at the design, planning and operational level includes redefinition of energy aware management paradigms, introduction of new simpler protocols, definition of energy friendly resilience schemes including the possibility of quickly switching on and off devices upon failures, as well as support of planning and routing algorithms which reduce the network overprovisioning to enhance energy features. Finally, attempts to match the characteristics of currently popular applications such as P2P, grid or cloud services to the underlying optical-based network infrastructure can further enhance energy savings in future network infrastructures, for operators, service providers and users.
7. Standardisation
Research projects bring relevant solutions to its application fields. However, translation from research to industry is a slow and difficult path that unfortunately remains uncompleted most of the times. Standardization is however key for the industrialization of research solutions. It takes time and money for particular solutions to reach a global market that increasingly tends to replace silos by open solutions. Standardization carries this demanded openness by interoperability among the different vendors/providers solution with the cost reduction of mass production (operators can purchase equipments from any vendors/providers; vendors/providers can sell equipments to any operators).
Nevertheless, in the current model of standardization followed by EC Research Projects it is hardly manageable to standardize results within the meantime of the project. The limited timeframe of a project related to the timeframe of a standardization process, tied to the fact that standardization efforts are commonly launched at advanced laps of the project, makes difficult
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the success of the standardization of a particular solution. An inter-project common standardization strategy will pave the way to overcome these difficulties by increasing the influence of European projects and consortiums on standardization bodies while providing a long term presence during the whole standardization process. The current standardization strategy covers three fronts, which from now and on will be coordinated by the CaON cluster.
7.1. Optical data plane technology
The driving standardization body in this case is the ITU-T. There are several EC Research Projects dedicating efforts to standardization addressing the encompassed technologies.
Photonic Access: The FSAN standardization ITU-T Task Force is focused in the standardization of NG-PON2 technologies (as a "Disruptive" NG–PON technology with no strict requirement in terms of coexistence with GPON on the same ODN), where the SARDANA, ACCORDANCE and FIVER European projects are participating. The ALPHA European project is working on the standardization of WDM-10G TDM PON.
Metro and Core: The efforts are centered High Speed Transmission (100G+), Flexi-grid technologies and MPLS/photonic integration. The STRONGEST European project has presence in these standardization works.
Power efficiency: The STRONGEST European project is working on it for Metro and Core networks while the TREND European project is active on Access networks.
With regards to the access, the standardization process is an ongoing work, the groups are entitled to consolidate their efforts and remain very active in proposing their solution and specifications to the standardization bodies (especially for NG-PON2). The time frame of NG-PON2 in standardization is shown in Fig. 11
Fig. 11
7.2. Optical control plane
The driving standardization body in this case is the IETF, with two major initiatives to provide vendor/provider interoperability and automatic end to end connectivity:
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GMPLS: The practical totality of the projects concerning Metro and Core Networks adopt GMPLS as the preferred control plane platform due to its wide technology umbrella it permits: the STRONGEST and GEYSERS projects for wavelength switching technologies, the MAIN project for sub-wavelength technologies, the ETICS project for both (covering inter-carrier issues).
PCE: As a key element (enabler of inter-operability) of MPLS and GMPLS networks, it is also subject to standardization efforts of STRONGEST, MAINS, GEYSERS, ETICS.
7.3. IT and network integration
It is an incipient field with standardization efforts open by different bodies towards the convergence of the two words.
The OGF is the driving standardization body in this case, organized in several working and research groups: the MAINS project has precense in the OGF-NSI WG (Network Service Interface Working Group) and the GEYSERS project in the ISOD-RG (Infrastructure Services On-Demand Provisioning Research Group).
Meanwhile there is an intend to create a IETF working group on Cross-Stratum Optimization, where the GEYSERS project may have an important presence.
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8. References
Energy efficiency
[1] M. Pickavet, W. Vereecken, S. Demeyer, P. Audenaert, B. Vermeulen, C. Develder, D. Colle, B. Dhoedt, and P. Demeester, “Worldwide Energy Needs for ICT: the Rise of Power-Aware Networking,” in IEEE ANTS Conference, Bombay, India, Dec. 2008.
[2] M. Pickavet, R. Van Caenegem, S. Demeyer, P. Audenaert, D. Colle, P. Demeester, R. Leppla, M. Jaeger, A. Gladisch, H.-M. Foisel, “Energy footprint of ICT,” in Broadband Europe 2007, Dec. 2007
[3] J. Baliga, K. Hinton, R. S. Tucker, “Energy consumption of the Internet”, proceedings COIN-ACOFT 2007, Melbourne (Australia), pp 1-3, June 2007
[4] R. Tucker et al., “Energy consumption in IP networks”, in European Conference on Optical Communication ECOC’2008, Brussels, Sept. 2008.
Section 4
[5] [1] D. Chiaroni, et.al., “Demonstration of the Interconnection of Two Optical Packet Rings with a Hybrid …“, PD3.5, ECOC 2010
[6] [2] F. Vismara, et.al. , “A Comparative Blocking Analysis for Time-Driven-Switched Optical Networks”, ONDM 2011
[7] [3] M. A. Gonzalez-Ortega, et.al, “LOBS-H: An Enhanced OBS with Wavelength Sharable Home Circuits”, ICC 2010
[8] [4] B. Wen, et.al, “Routing, wavelength and time-slot-assignment algorithms for wavelength-routed optical WDM/TDM networks”, ICTON 2010
[9] [5] Dunne, J., "Optical Packet Switch and Transport: A New Metro Platform to Reduce Costs and Power by 50% to 75% …”, WOBS 2009
[10] [6] G.Zervas et al “Time Shared Optical Network (TSON): A Novel Metro Architecture for Flexible Multi-Granular Services”. ECOC 2011 Geneve.
[11] [ABOSI09] C.E. Abosi, R. Nejabati, and D. Simeonidou: Design and Development of a semantic information modelling framework for a service oriented optical Internet. International Conference on Transparent Optical Networks, 2009. ICTON 09. Azores. Portugal.
[12] [WILLNER09] A. Willner, C. Barz, J.A. García Espín, J. Ferrer Riera, S. Figuerola and P. Martini: “Harmony - Advance Reservations in Heterogeneous Multi-domain Environments”. IFIP TC-6, Networking 2009, Lecture Notes in Computer Science, 2009, Volume 5550/2009, 871-882, DOI: 10.1007/978-3-642-01399-7_68
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i The porjects involved on the CaON cluster are : GEYSERS, ONE,......
