News
New Optical Strategy Takes Shape
21 MAY 2010: Following a recent review, the JANET Optical Networking Strategy is being updated to reflect current market and technology positions and JANET(UK)'s development plans, and an overview of some of the main themes follows below.
The original strategy was developed based on experience gained in service provision using dedicated circuits during the UKLight project, combined with the step-change in approach to JANET network engineering which was achieved with the procurement of the SuperJANET5 backbone. This move to direct use of dedicated optical fibres and associated transmission systems as foundations for JANET services made it important to track commercial optical networking technologies and assess their relevance for JANET infrastructures, both current and future.
The TDM (SDH) technology which was appropriate for the UKLight project and its origins within SuperJANET4 was implemented with equipment which was becoming increasingly expensive to operate and maintain, and after considering alternatives, this part of the JANET Lightpath Service was re-engineered using an MPLS switched network to carry the layer 2 project traffic.
This area has been dropped from the new strategy which reflects the shift away from classic TDM. However, during the intervening period, the standards associated with Optical Transport Networks (OTNs) have matured significantly and now address circuits with capacities between 1Gbit/s to 100Gbit/s and a granularity of 1Gbit/s. This retains the TDM structuring concept, but extends beyond the 40Gbit/s (STM256) level where development of the older SDH standards has now been frozen. In future, it is expected that the majority of high capacity circuits will either be framed for OTN use, or be one of the Ethernet options at 10, 40 (not yet fully standardised) or 100Gbit/s.
At the true optical level, developments in modulation techniques have enabled a shift from 10Gbit/s to 40 and 100Gbit/s capacities per wavelength in the optical transmission systems, and JANET now uses 40Gbit/s circuits in the core network. JANET(UK) has also undertaken successful trials at 100Gbit/s with our service partners as previously reported. The strategy will incorporate these changes to higher capacities per wavelength, and focus on equipment capabilities which enable flexible and cost-effective management of the bulk network capacity provided by the optical transmission systems. Devices such as Reconfigurable Optical Add-Drop Multiplexers (ROADMs) offer the prospect of achieving this flexibility of management of the wavelengths carried on the optical fibres, making it easier to add extra wavelengths (i.e network capacity) and control how these are routed within the network and how the optical power is managed to ensure signal and communications integrity. The strategic element here is to understand how these developments feed into approaches to network architectures, and to assess these for relevance to JANET. Other NRENs have similar interests and another important source of information is through the international fora where insight into the approaches our peers are taking can be obtained.
There is continuing interest in layer 2 transmission technologies incorporating traffic-engineering capabilities which enable traffic to be sent along pre-determined routes through networks. These are seen as cost-effective and fine-grained delivery mechanisms for layer 2 lightpath services, and may also be important in future networks as providers of structuring capabilities to enable different traffic classes or different customer groups to receive appropriate engineering solutions.
Such capabilities will become more important as network trunk capacities move to 40 and 100Gbit/s per wavelength and the ability to control network traffic in this way will be important to manage broad service mixes which include an increasing proportion of applications sensitive to real-time constraints such as collaborative use of voice and video.
The two major technology candidates are MPLS (or the emerging carrier variant MPLS-TP) and carrier Ethernet in its IEEE standardised form PBB-TE (Provider Backbone Bridging–Traffic Engineering IEEE 802.1Qay). The strategy includes development work in both areas in the form of lab based and wide-area trials with partners in the JANET community.
A long-standing aim has been to make the Lightpath service easier to manage and to speed-up circuit provision. This remains in the strategy as a theme of dynamic provisioning, and feeds into the layer 2 development work noted above in the form of requirements on management and provisioning systems which would control the equipment to deliver services.
Commercial systems providing these functions are evolving, but are still largely proprietary, so the strategy also contains development work associated with provisioning and control systems which have emerged from the NREN communities in Europe and the United States. In Europe, development of the AutoBAHN system[1] continues within the current GEANT programme GN3, and in the US, networks such as Internet2 and ESnet have deployed systems to enable dynamic provisioning over their infrastructures. JANET(UK) has begun lab-based work to evaluate these systems, and this is likely to lead to small-scale wide-area trials, probably involving an international element with partners from either or both of the initiatives mentioned above.
