Core and Metro Networks
April 2010, ©2009
In this book, the authors provide an overview of the status, challenges, architectures, and technological solutions for core and metropolitan networks. Furthermore, the book describes the current state of core and metropolitan telecommunication networks, as well as the drivers and motives behind the current paradigm shift in the telecommunications industry. Moreover, the authors elaborate system design guidelines for both point-to-point and multi-hop optical networks taking into consideration the analogue nature of the transmission channel.
- Provides coverage of all aspects of core and metro networks supporting future broadband services, and a detailed description of the state-of-the-art
- Presents a clear path for migrating from point-to-point to data-centric, dynamic, multi-hop optical networks
- Shows how current systems will need to evolve over the coming years, summarizing challenges and issues to be investigated in future research
- Covers a wide range of topics from network architectures, to control plane, to key optical and optoelectronic devices, and best practice in transmission and system design
- Provides results, best practices and guidelines for various technical problems, including numerous hands-on examples
- Written by authors from cutting-edge companies such as Alcatel-Lucent, Siemens, Lucent, France Telecom, BT, and Telefonica
Optical Core and Metro Networks will be of interest to researchers in industry and academia, and advanced (final year undergraduate) and postgraduate students undertaking communications, networking and optics courses.
1 The Emerging Core and Metropolitan Networks
Andrea Di Giglio, Angel Ferreiro and Marco Schiano
1.2 General Characteristics of Transport Network
1.3 Future Networks Challenges
1.4 New Transport Networks Architectures
1.5 Transport Networks Economics
2 The Advances in Control and Management for Transport Networks
Dominique Verchere and Bela Berde
2.1 Drivers Towards More Uniform Management and Control Networks
2.2 Control Plane as Main Enabler to Autonomic Network Integration
2.3 Multilayer Interactions and Network Models
2.4 Evolution of Connection Services and Special Cases of Optical Networks
3 Elements from Telecommunications Engineering
Chris Matrakidis, John Mitchell and Benn Thomsen
3.1 Digital Optical Communication Systems
3.2 Performance Estimation
4 Enabling Technologies
Stefano Santoni, Roberto Cigliutti, Massimo Giltrelli, Pasquale Donadio,
Chris Matrakidis, Andrea Paparella, Tanya Politi, Marcello Potenza,
Erwan Pincemin and Alexandros Stavdas
4.4 The Optical Fiber
4.5 Optical Amplifiers
4.6 Optical Filters and Multiplexers
5 Assessing Physical Layer Degradations
Andrew Lord, Marcello Potenza, Marco Forzati and Erwan Pincemin
5.1 Introduction and Scope
5.2 Optical Power Budgets, Part I
5.3 System Bandwidth
5.4 Comments on Budgets for Nonlinear Effects and Optical Transients
5.5 Semianalytical Models for Penalties
5.6 Translucent or Hybrid Networks
6 Combating Physical Layer Degradations
Herbert Haunstein, Harald Rohde, Marco Forzati, Erwan Pincemin,
Jonas Martensson, Anders Djupsj€obacka and Tanya Politi
6.2 Dispersion-Compensating Components and Methods for CD and PMD
6.3 Modulation Formats
6.4 Electronic Equalization of Optical Transmission Impairments
6.5 FEC in Lightwave Systems
6.6 Appendix: Experimental Configuration and Measurement Procedure for Evaluation and Comparison for Different Modulation Formats for 40 Gbit/s Transmission
Dictionary of Optical Networking
Didier Colle, Chris Matrakidis and Josep Sol_e-Pareta
Broadband is becoming the dominant access mode to the Internet. High capacity broadband connections enhance the users' experience, freeing them from the inconvenient dial-up service. With user data rates of typically between 1-20 MBit/s downstream, broadband access enables the user to get more out of existing services and, more importantly, opens up opportunities for new services. Already the expansion of broadband networks has brought with it a host of new services, such as voice over IP and video streaming. By 2010-2012 it is expected that advanced countries will reach an 80-90% household penetration. This market success in broadband access has been made possible by cost-efficient technologies and by the adoption of flat-rate tariffs.
Multimedia convergence encompasses convergence of products and solutions in telecom, broadcasting, digital media and consumer electronics. It is a profound revolution in the ICT sector that has started several years ago and finds its origins in technological evolutions allowing for the ability of different network platforms to carry essentially similar kinds of digital services, including the integration of consumer devices such as telephony, television and personal computing.
Rapidly convergence has affected businesses by changing the business roles and the competitive environments of the sector actors. Convergence is at the source of major reshaping of the telecom, broadcasting and digital media worlds. Multimedia convergence has further triggered radical changes in the ways digital multimedia services are consumed by the end-user, who evolved from a passive multimedia services consumer towards a major player controlling and creating his own communications and media. In turn these changes in consumer's behaviour have opened a series of new technological and scientific fields in the areas of multimedia networking, services, applications and devices.
A first step of convergence has already been implemented and offered in so-called triple-play packages, where broadband Internet access is complemented by a number of applications, such as television and VoIP. A triple-play access supporting mobility in addition is also called quadruple-play access. Whereas the term Fixed-Mobile Convergence (FMC) has originated with the aim of fixed-mobile telephony convergence, the vision today is larger aiming at making accessible any service seamlessly fixed or mobile.
From a network point of view, convergence is realised by the evolution of networks that support all kinds of different services or even "converged services", which are no longer designed to be deployed or delivered over a specific network. The basis for the future of a plethora of converged services is the emerging Next Generation Network (NGN). This will consist of
- Various next generation access networks, reducing any bandwidth bottlenecks that may exist today at the access level. This evolution is not related to any single access technology but to characteristics of an access infrastructure capable in providing higher and scalable bandwidth, better symmetry and lower contention
- Global next generation core networks with nearly unlimited bandwidth in the backbone
- Next generation service control, which will provide the framework for intelligent and convergent service creation
Broadband for All
In recent years, research activities in broadband communications have achieved progress towards network technologies and architectures allowing a generalised and affordable availability of broadband access, fixed and wireless, to all users, including those in less developed regions, peripheral and rural areas.
The objective of the FP6 Strategic Objective "Broadband for All", which has been funded by the EU with approximately 159M€ in 38 FP6 projects, has been to develop the network technologies and architectures allowing a generalised and affordable availability of broadband access to European users, including those in less developed regions, peripheral and rural areas.
One of the key areas in the programme "Broadband for All" was optical network technologies. The main objective was increased bandwidth capacity, in the access network as well as in the underlying optical core/metro network, including in particular optical burst and packet switching, commensurate with the expected evolution in user requirements and Internet-related services.
The NOBEL project
NOBEL has been the flagship project of this area. The overall goal of NOBEL phase 1 was to develop innovative network solutions and technologies for intelligent and flexible metro and core optical networks, and to validate these technologies to ensure their suitability for broad implementation across the EU. Providing input to the standardisation bodies (ITU, OIF and IETF) was also central to the project’s aims.
The rationale was that by working together to develop the most suitable technologies for mass-market adoption of broadband capabilities, the partners would be able to develop critical mass in markets more quickly. It is only when markets reach critical mass that businesses can offer broadband services to customers at a realistic cost, while customer demand reaches levels that make such services economic to provide.
The NOBEL project partners consist of telecom network operators, equipment manufacturers and research centres across Europe, in fact just about every major name in the telecom field. In addition to Telecom Italia, they include Alcatel, British Telecom, Deutsche Telecom, Ericsson, Lucent Technologies, Siemens, Telefonica, CISCO, France Telecom and many more.
In their research the partners studied technology developments over three distinct periods; progress in the next few years, developments in the medium term, and the longer-term future. For each of these periods they examined network technologies, network services, and the ‘control plane’, i.e. the network technologies, algorithms and protocols that enable automatic network configuration, either to meet customer demand or to compensate for faults.
In the immediate future for example, the partners looked at Internet Protocol (IP) and Multiprotocol Label Switching (MPLS) technologies, Ethernet, next-generation Synchronous Digital Hierarchy (SDH), including GFP, LCAS and VCAT technologies and Optical Transport Hierarchy (OTH). They also foresaw the likely take-up of level 3 VPN (Virtual Private Networks), or virtual network services responding in a similar way to IP. In the control plane, features such as basic Automatically Switched Optical Network (ASON) and Generalised Multiprotocol Label Switching (GMPLS) would allow fast automatic reconfiguration of networks to meet varying traffic needs.
Over the medium term, transport technologies would stay the same except that OTH would give way to OTN, providing more advanced network traffic management. Network services would see the introduction of level 2 VPNs, and technologies in the control plane would develop greater power, more flexibility and more features, such as the possibility to offer the Bandwidth on Demand, thanks to the introduction of ASON.
For the extended-term scenarios, transport technologies would see the introduction of facilities such as burst-switched networks using Optical Burst Switching. In network services, level 1 VPNs would underpin key optical circuits for network operators and major business customers, with significant new features such as bandwidth-on-demand. While in the control plane, GMPLS would be based on a peer-to-peer model.
NOBEL phase 2
Building on research in its predecessor, the NOBEL phase 2 consortium’s ambitious goal was to provide this next-generation optical broadband network. It is the enabler for this by reducing the upfront costs and simplifying network architecture and management to cut operational costs as well.
The idea is to give every European household fast access to all that the Internet has to offer, including browsing, e-commerce and e-government, services for health, and developing services such as IPTV.
NOBEL2 has identified three basic innovations as the key to the development of new- generation optical networks.
First up is transparency. A transparent optical network transmits and switches signals as light rather than electricity. The signals can be between any pair of nodes on the network with no speed or distance restrictions. What this means, in practical terms, is that there is no longer any need for expensive equipment at intermediate network nodes – the network is easier to manage as a result, and extra traffic can easily be accommodated.
So, thanks to this technological breakthrough, not only are transparent optical networks cheaper to build and maintain than conventional legacy telephony networks, they are also far more efficient and flexible with much greater capacity.
NOBEL2 has also made major progress in the field of automated intelligent networks, thanks to its work with the network control plane (CP). CPs are computation and communications systems that automatically control a network’s lower-level functions which are too complex to be controlled by human operators. As well as simplifying the management of complex networks, CPs mean new connections can be made on demand, and this means new opportunities in on-demand services.
Third, the project has been researching the use of packet transport technologies, which send separate ‘packages’ of data rather than a continuous bit-stream, as a more efficient use of network resources. It also provides a unified networking concept for all data, voice and video operations.
What comes next?
What comes next, after NOBEL? In Framework Programme 7, Future Internet has become the federating theme for European research on communication networks and services. In the core lies research on communication networks towards an efficient, scalable and reliable Future Internet coupled with research on the underlying technologies, in particular mobile and wireless access and optical networks.
One of the important infrastructure foundations of the Future
Internet are ultra-high-capacity optical transport and access
networks. They are expected to be based on state-of-the-art
photonics with transparent core-access integration, optical flow
and packet transport, dynamic wavelength allocation and end-to-end
service delivery capability. They should overcome the limitations
of segmentation between access, metro and core networks and
domains, enable lower cost optical access and address the need for
energy efficiency. Integrated projects are expected to address also
a network control plane supporting flexible management capability
of multi-domain and multi-operator contexts with end-to-end carrier
—Dr. Peter Stuckmann
DG Information Society and Media
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