Green Video-Dominated P-OTNs


Motivation

           In their migration toward Next Generation Networks (NGNs), today’s carriers desire to integrate the latest packet networking technologies such as connection-oriented Ethernet and MPLS with installed optical network technologies such as WDM, ROADM, and OXC, giving rise to converged Packet Optical Transport Networks (P-OTNs). P-OTNs aim at providing a smooth migration platform toward an all-packet infrastructure and addressing carriers’ drive to investment protection and lower CAPEX/OPEX by capitalizing on low-cost layer-2 switching functionalities. This research tackles open issues of emerging PBB-TE networks and explores next-generation carrier Ethernet switch architectures with advanced packet switching capabilities and new forwarding models, paying particular attention to their control, evolutionary migration not only from legacy SONET/SDH TDM but also widely deployed WDM circuit-switched network infrastructures, as well as their coexistence with IP/MPLS routers, backward compatibility with existent Ethernet switches, and further integration of new and emerging standards.

Research Direction

           Though IP/MPLS routers lead new installations, there exists a huge base of legacy SONET/SDH circuit switched time division multiplexing (TDM) equipment dominating the installed infrastructure of today’s backbone networks. As a result of ITU-T’s Global Standards Initiative (GSI), current widely deployed circuit switching SONET/SDH networks will evolve into NGNs whose transfer is based on packets instead of circuits in order to converge and optimize their operation and meet the increasing demand for new multimedia services and mobility.

Toward the realization of carrier Ethernet networks, traditional Ethernet bridges/switches must be gradually enhanced with advanced capabilities and forwarding models, while at the same time operating at ever increasing line rates. In our research, we focus on the latest carrier Ethernet technology called Provider Backbone Bridge-Traffic Engineering (PBB-TE), which was recently ratified in IEEE standard 802.1Qay in June 2009.

In order to provide transport features such as wide-area scalability, fast recovery from network failures, advanced traffic engineering and end-to-end QoS, as well as operation, administration, and maintenance (OAM) capabilities, traditional Ethernet switches have evolved into carrier Ethernet switches in several steps. The step-by-step migration toward carrier Ethernet implied a number of evolutionary modifications of the original IEEE 802.1 Ethernet frame format, depicted in Fig. 1.

Ethernet frame evolution
Fig. 1. Ethernet frame evolution (D. Allen et al.,2006).


Another interesting issue that motivates us for a more scalable architecture is the latest Internet Forcast of Cisco Visual Networking Index. This forcast shows the huge growth in Internet data traffic. As Fig. 2 shows, overall IP traffic is expected to grow to 56 exabytes per month by 2013, whereby 40 exabytes are due to consumer Internet traffic.

Fig. 2. Cisco Forecasts 56 Exabytes per Month of IP Traffic in 2013
Fig. 2. Cisco Forecasts 56 Exabytes per Month of IP Traffic in 2013.


Video will be responsible for the majority of the traffic growth between 2008 and 2013. As indicated in the Executive Summary of Cisco Visual Networking Index June 9, 2009, The sum of all forms of video (TV, video on demand, Internet, and P2P) will account for over 91 percent of global consumer traffic by 2013. Internet video alone will account for over 60 percent of all consumer Internet traffic in 2013. In 2013, Internet video will be nearly 700 times the U.S. Internet backbone in 2000. It would take well over half a million years to watch all the online video that will cross the network each month in 2013. Internet video will generate over 18 exabytes per month in 2013. Video communications traffic growth is accelerating. Though still a small fraction of overall Internet traffic, video over instant messaging and video calling are experiencing high growth. Video communications traffic will increase tenfold from 2008 to 2013. Real-time video is growing in importance. By 2013, Internet TV will be over 4 percent of consumer Internet traffic, and ambient video will be 8 percent of consumer Internet traffic. Live TV has gained substantial ground in the past few years: globally, P2P TV is now slightly over 7 percent of overall P2P traffic at over 200 petabytes per month. Video-on-demand (VoD) traffic will double every two years through 2013. Consumer IPTV and CATV traffic will grow at a 53 percent CAGR between 2008 and 2013, compared to a CAGR of 40 percent for consumer Internet traffic.

This research addresses open issues of emerging PBB-TE networks and explores next-generation P-OTN switch architectures with advanced packet switching capabilities and new forwarding models, paying particular attention to their control, evolutionary migration not only from legacy SONET/SDH TDM but also widely deployed wavelength division multiplexing (WDM) circuit-switched network infrastructures, as well as their coexistence with IP/MPLS routers and backward compatibility with existent Ethernet switches. The following open issues will be tackled in our research activities:

Convergence with IP/MPLS
PBB-TE introduces a connection-oriented forwarding mode to the data plane of traditional connection-less Ethernet networks assuming that the forwarding tables of PBB-TE switches are populated with ESP related table entries through an external control (or management) plane. The development of a control plane to set up, modify, and tear down ESPs is currently one of the key open issues in PBB-TE. There is a risk to be tempted to add too many replicated networking functions to Ethernet and thus lose its trademarks of low cost and simplicity. Instead, Ethernet should be viewed as a highly effective complement to IP/MPLS and should not attempt to replace it. Recently, Ethernet over MPLS (EoMPLS) transport services over a Generalized MPLS (GMPLS) controlled optical circuit-switched network was successfully demonstrated. However, this approach involves an additional set of encapsulation standards (so-called pseudo-wires) which allow IP/MPLS routers to carry non-IP traffic, e.g., Ethernet. As a result, the complexity of the protocol stack is increased significantly. In fact, many carriers find that while IP/MPLS offers many features, enabling them introduces a whole new set of complex challenges, e.g., troubleshooting. There is a need for a different approach to converge IP/MPLS and PBB-TE in order to carry Ethernet frames natively. Given that GMPLS supports a wide range of interface switching capabilities and allows for explicit constraint-based routing, and the administrative benefits of using a single control plane are enormous, the GMPLS control plane is extended for PBB-TE networks at present. This work in progress is known as GELS.

Energy Consumption
An important feature of future network equipment is energy consumption in relation to network operation as well as heat dissipation. Lowering energy consumption results in significant cost savings and gives service providers a competitive edge. Power consumption represents one of the most serious obstacles of expanding the capacity of today’s routers and switches due to their underlying optical-to-electrical-to-optical (OEO) conversion, which is a highly power-consuming process. In fact, almost 50% of power is consumed by OEO conversion and chip-to-chip communication. forwarding mode to the data plane of traditional connection-less Ethernet networks assuming that the forwarding tables of PBB-TE switches are populated with ESP related table entries.

Flow Management
In today’s Internet, voice and video applications are exploding with an ever increasing number of users streaming multimedia content to their PCs and wireless handhelds, e.g., iPhones and BlackBerrys, and peer-to-peer (P2P) services consuming more and more bandwidth. Current routers and switches, including PBB-TE switches, handle streaming media on a per-packet basis where each packet is processed and forwarded independently from each other. As a result, each individual packet’s destination address must be looked up in the forwarding table, switched, and stored in an output queue instead of treating all packets that are part of the same stream as a flow. With flow management, a switch is able to identify the first packet in a flow and let the remaining packets of the flow bypass the switching and queuing stages, giving rise to new forwarding models and resulting in significant performance gains and savings in terms of power, size, complexity, and cost.

Extended Frame Sizes
For backward compatibility, PBB-TE still uses the original MTU of 1500 bytes. The current maximum Ethernet frame size not only poorly matches the much larger MTU of 65536 bytes of IP/MPLS routers, but more importantly degrades the performance of many of today’s attached servers dramatically, thus negating many of the initial benefits of high-speed Ethernet networks. Extending frame sizes is crucial to increase the throughput of next-generation Ethernet networks and decrease the CPU utilization of attached servers. Extended frame sizes yield significant benefits especially for large data transactions, e.g., storage and file backup, and HDTV video, which has an average video frame size of 83300 bytes and is expected to dominate future Internet traffic. Given the current Ethernet 32-bit frame check sequence, however, extended frame sizes must not exceed 11455 bytes to maintain the same bit error rate accuracy.

Researchers

Advisors
  •    Prof. Chadi M. Assi
  •    Prof. Martin Maier
Graduate Students
  •    Mohammad Nurujjaman Beajon

Publications

  •     M. Nurujjaman, S. Sebbah, C. Assi, and M. Maier, “Optimal Capacity Planning and RPL Placement in Carrier Ethernet Mesh Network Design,” Proc., IEEE International Conference on Communications (ICC), Ottawa, ON, Canada, June 2012.
  •     M. Nurujjaman, M. Sharifi-Rayeni, C. Assi, and M. Maier, “Green Packet Optical Transport Networks (P-OTNs) Based on Photonic PBB-TE Switches and Minimized EEE Overhead,” IEEE/OSA Journal of Lightwave Technology, vol. 30, no. 6, pp. 893-905, March 2012.
  •     M. Nurujjaman, M. Sharifi-Rayeni, C. Assi, and M. Maier, “Minimizing EEE overhead in Green Packet Optical Transport Networks (P-OTNs),” Proc., IEEE GLOBECOM, Houston, TX, USA, Dec. 2011.