Question 12/15 – Transport network architectures
(Update of Question 12/15 to include some of the work of Q9/15)
Transport network architecture Recommendations (G.800, G.805 and G.809) and technology specific network architecture Recommendations (G.803, G.872, G.8010, G.8110, G.8110.1 and I.326) have been established and are widely used. As operating experience is gained with employing current transport network technologies and new technologies evolve (e.g., variable size packets, high-speed transport networks), new Recommendations, or enhancements to existing Recommendations need to be developed, in close cooperation with the standardization activities on transport network systems and equipment. The operational aspects of networks, including the use of ASON or SDN for restoration, are becoming more important. The operational aspects of combined packet and circuit switched optical networks should be considered to ensure that they are addressed in a way that is architecturally sound and minimizes divergent approaches.
Software Defined Networking (SDN) is an architectural approach to managing transport network resources. Its architecture needs to be understood in the context of the management control continuum that includes the Architecture of the Automatically Switched Optical Network (G.8080). Commonality and differences with existing architectures requires study as it is applied to various transport layers. Requirements for enhanced control interfaces to and within the transport network, for example to support network slicing, need to be studied. Interfaces to configure and control programmable hardware are needed. Interfaces that enable clients to request network services beyond basic connectivity are needed.
Network Functions Virtualisation (NFV) is an architectural approach in which some network functions are implemented as a programme on a generic compute platform. There are strong synergies between SDN and NFV especially in the goal of providing automated control. This drives the need for compatible enhanced control interfaces. This suggests the need for strong compatibility between the functional modelling currently used for the transport network and the functional model for NFV.
The continued evolution of transport networks and the services they support such as, the Internet, IMT-2020/5G, datacentre-based services, and higher definition video, have resulted in drastic changes in the demands placed on transport networks. Transport networks need to continuously evolve to meet these changing demands and provide a converged transport network. This rapidly evolving situation led us to recognise the need for a coordination and communication activity among the involved Questions (primarily Questions 2, 6, 7, 9, 10, 11, 12, 13, and 14/15) in order to avoid duplication of work and facilitate the most efficient completion of the work. Also, a standardization work plan for new optical transport network activities (the Optical Transport Networks and Technology Standardization Work Plan (OTNT SWP)) needs to be maintained. In addition, some general aspects such as terminology, need to be captured.
The following major Recommendations, in force at the time of approval of his Question, fall under its responsibility: G.800, G.803, G.805, G.809, G.872, G.7701, G.7702, G.8010/Y.1306, G.8080/Y.1304, G.8081/Y.1353, G.8110/Y.1370, G.8110.1/Y.1370.1 and I.326.
What new or modifications to existing Recommendations are required to:
- refine and enhance the specification of Transport Network Architecture, including enhancements to G.800, G.872, G.7701, G.7702, G.8010, G.8080, G.8110 and G.8110.1, including use of ASON or SDN for network restoration, operational aspects and implications of the evolution of photonic technologies to support additional flexibility within the transport network?
- define the architecture for SDN control of transport networks?
- understand the commonality and differences between SDN and Automatically Switched Optical Network (ASON) architectures?
- explore the relationship between the Transport Network Architecture and applications such as computing and storage, including NFV?
- explore the implications of multi-technology and multi-layer integration, the potential for network simplification and the consequent impact on the network architecture and existing standards?
- develop the architecture of media networks as the manner in which information layers use them is evolving?
- explore the relationship between SDN and ASON functions, and how control functions are related to the information models developed in Q14/15?
- explore enhancements to the architecture of transport networks to address emerging requirements of IMT-2020?
- Specify requirements for enhanced control interfaces to and within the transport network? Interfaces to configure and control programmable hardware are needed.
- Define interfaces that enable clients to request network services beyond basic connectivity?
- Explore for SDN control of transport networks, the implications of the centralized vs distributed control architectures (the management/control continuum)?
- reflect synchronization (as studied in Q13/15) in architecture Recommendations?
Study items to be considered include, but are not limited to:
- Transport networks that offer circuit switching capability including photonic switching technology.
- Transport networks that offer packet switching capability, including packet switching in the photonic layer.
- Converged multi-technology and multi-layer transport networks.
- The architecture of the media layer and new ways that information layers can be supported over media.
- Support of point-to-multipoint and multipoint-to-multipoint transport services.
- The dynamic behaviour of resources in the network (e.g. link speed change).
- The relationship with functional modelling required for NFV.
- The Software Defined Networking (SDN) architectural approach and its role in providing more flexible control.
- Use of ASON or SDN for network restoration
- What enhancements to OTNT SWP or what new Recommendation(s) or mechanisms are necessary to capture, within this framework, new or evolving aspects of optical transport networks, their general terminology, and reliability/availability characteristics?
Tasks include, but are not limited to:
- Maintenance of Recommendations I.326, G.803, and G.805.
- Refinement and enhancement of Recommendations G.800, G.872, G.8010, G.8080, G.8110 and G.8110.1.
- Investigate the use of ASON or SDN for network restoration and clarify the relationship between protection switching and restoration techniques.
- Facilitate discussion among questions during SG15 meetings to coordinate work on Optical Transport, including the harmonization of terminology.
- Develop, maintain, and regularly distribute a work plan that documents the work and time schedules of all major new optical transport network activities (OTNT SWP).
NOTE − An up-to-date status of work under this Question is contained in the SG15 Work Programme at:
- Q2/15, Q6/15, Q7/15, Q10/15, Q11/15, Q13/15 and Q14/15
- ITU-T SG2 on telecommunication management
- ITU-T SG13 working on SDN and IMT-2020/5G
- JCA-IMT-2020 on 5G
- ITU-T SG20 requirements from IoT
Standardization bodies, forums and consortia:
- IETF on Control Plane Issues
- IEEE 802 on Ethernet Issues
- OIF on Optical Control Plane and FlexEthernet
- ONF on SDN
- ETSI ISG NFV
- 3GPP on IMT-2020/5G
- BBF on IMT-2020/5G