The choice of where to place flexibility in a network has many dimensions. Physically - should it be distributed or centralised? Logically - which layer or combination of layers to use? Since the consensus for 5G seems to be placing the intelligence at the access edge and in the core with dynamic, resilient packet connectivity between the two, I will not consider in detail where flexibility should be placed. That said, I will discuss the options we have to start deploying now to support future 5G networks as they roll over the horizon.
I would not be remiss to say that today we are spoilt for choice:
Curiously the first telecoms regulation in the UK was driven by environmental considerations rather than competition, as now. The proliferation of overhead copper wires deployed by large numbers of small telephone operators became a major safety hazard. The government consolidated all the telephone networks at the start of the 20th century apart from Hull and Guernsey.
Physically cross-connecting services is low on CapEx but can be high on OpEx if the network needs to be regularly reconfigured. In addition manual reconfiguration is a difficult task prone to mistakes.
ROADMs and their associated optical amplifiers continue to fall in price and improve in performance to the point where now, with Flexgrid capability and coherent transmission, they offer a very attractive future proof flexible wavelength layer. I tend to recommend the use of ROADMs over fixed cross-connects for most new core network deployments because it leaves options for expansion and use open.
An OTN layer for sub 100G aggregation and resilience is useful if the services are dedicated point-to-point or hard guarantees of performance are wanted. However a WDM layer can have some wavelengths dedicated to OTN connectivity and others for packet connectivity.
A L2 /L2.5 packet layer facilitates packet aggregation, L2 VPNs and shared bandwidth. This is especially efficient where bursty traffic such as internet access is being supported, or customers wish to build extended LANs
If you are building a new core network it generally makes sense now to design for wavelengths carrying 100G and above, unless the bandwidth requirement is guaranteed to always be low. Building a WDM layer with manual wavelength patching will be very difficult to upgrade to ROADM based cross-connects - so if possible build a ROADM layer. Adding OTN and or packet cross-connects can be decided on the basis of the type of services being carried. These can also be mixed on the same WDM layer. Additional wavelengths can be utilised as capacity requirements grow. An important criteria is management of the network. Traditional element and network managers are fine now as long as they offer a route to SDN control.
For all of the above options ECI has a comprehensive set of market leading solutions. Compact, low power consumption and almost endlessly flexible. A key advantage we have is a single in-house developed management platform for WDM, OTN, SDH, Ethernet, MPLS-TP, IP/MPLS and Segment Routing. The look and feel of each layer is consistent saving training time and enhancing usability.
Dr. Antony Thorley C.Eng., FIET has over 35 years of telecommunications experience with vendors, operators and regulators, working on reviews of the business connectivity market. Currently Tony supports pre-sales technical work supporting the UK sales team and the UK market for ECI on DWDM, OTN, packet and network management for customers in the service provider, utility and data centre markets. He started his career with optical component specification and evaluation including early work on coherent transmission and optical amplifiers. Then moved to circuit design, sub-system design, system design and analogue ASIC development. His career has included over time: marketing, customer engineering, network strategy and regulation.