Optical IP Network Architectures

The Optical IP Network Architectures group is currently is currently proposing a number of novel research projects. The research activity is focused on transparent network architectures with distributed provisioning mechanisms, drawing on the work we have carried on "Optical IP Switching". A list of the past and current projects is given here.

Current projects

1. Long-Reach Pasive Optical Networks (LR-PON)

Passive Optical Networks (PONs) are widely recognized as a cost-effective fiber-to-the-home (FTTH) solution because of their ability to share network costs among a number of customers. However the large increase in bandwidth enabled by fiber access network means that metro and core networks will also need upgrading, producing a surge in the overall network cost. Next generation PONs address this issue and in particular the Long-Reach PON (LR-PON) has recently gained increasing interest as an economic and potentially profitable solution. By extending the optical reach to about 100 km the number of network nodes can be reduced by as much as two orders of magnitude, eliminating most of the local exchanges and thereby reducing both cost and energy consumption. Increasing the number of customers per PON from 32 to over 500 or even 1000 increases equipment and fibre sharing, further reducing cost, and making LR-PON an economically viable solution with low Capital Expenditures (CapEx) and short time to positive cash flow.
We are currently working on many asects of LR-PON networks, including optimal node positioning, advanced protection strategies and network cost modeling.

2. Intelligent, self-aware, cross-layer optical networks
Although Internet traffic growth has sensibly decreased over the past few years, traffic forecast show that annual growth of about 40% remains a plausible scenario over the next five years. Especially if we consider that service providers are now deploying FTTx solutions (many of which are FTTH), which have the potential to increase customer peak bandwidth by well over two order of magnitude compared to current offers on copper access, such traffic forecast seem to represent a lower bound. Traffic growth has put the core network under pressure to provide more and more bandwidth at lower and lower cost. Traffic forecast show that this trend will continue in the foreseeable future. Over the past decade growth on Internet related technologies and services leveraged on the exponential growth of available bandwidth, mainly supported by EDFA and WDM technologies at the optical layer and by extensive silicon chip integration in the electronics. Such technologies seem however to have reached saturation. We do not currently have competitive technologies able to exploit the additional bandwidth in the fiber. Similarly, scalability issues in dynamic heat dissipation in silicon technology have sensibly slowed down the capacity growth of network electronic equipment, such as IP routers. Power consumption has also become a major concern in networking and more in general for the IT sector. Although IT related power consumption is currently between 1 and 2 % of the total, it is growing three times faster than the rest. The concern generated by such growth has pushed much of current research on networks towards reduction of power consumption. Probably the most relevant example is the Greentouch consortium, which includes among the top vendors, operators and universities in the world, and aims at reducing power consumption in networks by 1000 times within the next 5 years. In addition, networking technology could help further reduce global power consumption in other areas such as transport, by making ideas (i.e., bits) travel instead of people. Although new techniques are being developed such as multi-level modulations, OFDM, coherent transmission, that aim at increasing the data rate that can be carried over a single fiber, it is believed that their ability in reducing the cost-per-bandwidth ratio will not be comparable to that allowed by EDFA and WDM technologies over the past decade. Although network capacity will keep growing over the foreseeable future, its growth will not benefit from the same economies of scale we have seen in the past, and bandwidth will be increasingly perceived as a scarce resource. Such trend will continue unless significant innovation will emerge in the optical transmission (e.g., with new transmission media) and in the electronic processing domain (e.g., for switching and routing functions). The quest for reduction in bandwidth cost will thus need to be tackled at multiple levels. Besides looking for technological advances at the physical layer, means for a more efficient use of the scarce bandwidth resources are also required. For example achieving quality of service through massive static over-provisioning of network resources is not sustainable. Similarly, current use of routing traffic almost exclusively through IP routers is not sustainable. These technologies do not seem scalable to support the Internet evolution in the foreseeable future, where high peak rates will be required to offer quality of experience to a multitude of to bandwidth-hungry applications, such as HD video on demand and thin client computing. We believe that dynamic and intelligent bandwidth allocation will be a key feature to enable efficient bandwidth usage and reduce the pressure on the network core. Such efficiency will be also reflected in reduced power consumption. Both access and core architectures will need to be redesigned to be more flexible, self-aware and self-managing, bandwidth and power efficient.

3. FPGA-hardware accelerated architectures
...coming soon...

Past projects

4. Optical IP Switching (OIS)
Optical IP Switching is a technique we have developed that creates and deletes optical cut-through paths in response to locala analysis of IP traffic. Switching data directly in the optical domain has important consequences. On one hand it can allow cost saving, as optical switch ports are data rate independent, and cost tens of times less than IP ports. On the other hand however, optical switching is operated at the wavelength granularity, which can become quite inefficient compared to the packet granularity offered by electronic routers and switches. This inefficiencies originate from the difference in granularity between electronic routing, where data is switched packet-by-packet (each in the order of the Kbyte in size), and wavelength switching, where data is switched at the channel rate (of the order of a few Gbps). We challenge this large gap (about six orders of magnitude) by first reorganizing the packets in IP flows, decreasing the granularity to values between hundreds of Kbps and few Mbps. We then aggregate the flows sharing a common route into the same dedicated optical cut-through paths, using a method we have developed, that groups flows depending on their destination network. The path creation algorithm finally selects the flow aggregates eligible for dedicated cut-through paths, taking into consideration the aggregate data rate, the resources available, the network policies of its own domain and, in the case of interdomain operations, the network policies of its neighboring domains.
The distinguishing features of our approach is that the optical paths provisioning mechanism is completely distributed and based only on local decisions. We believe that this approach better satisfies the requirements of Internet network architectures (especially in the inter-domain), where existing distributed routing protocols have proved to be very effective to cope with large-scale deployment, high heterogeneity (both of network technologies and user applications) and high traffic variability. For example, by adopting the OIS architecture different nodes can implement their own policies to decide if an incoming signal should be transparently switched or locally terminated. More details can be found here.

5. OIS interface to UCLP (User Controlled Light Path)
This project was developed in collaboration with i2cat, HEAnet and Glimmerglass, and involved the integration of UCLP and OIS, so that bandwidth on demand (BoD) services could be requested automatically by the OIS nodes, following traffic flow analysis. In this model OIS acts as a client of the external UCLP networks.
When an OIS node detects traffic destined for a specific external domain, it can automatically request the bandwidth needed to reach the desired destination. The UCLP server is the central unit in charge of signaling and scheduling operations, receiving the bandwidth requests, calculating the best routes and signaling the network elements to provision the optical paths. The interface we have developed for this experiment allows the OIS node to log into the UCLP server, download the network topology and request/release dedicated end-to-end paths. The novelty of our implementation is that we have provided the UCLP server with a mechanism that stores an updated list of network prefixes reachable through each node.