Key architectural features of P-OTS elements are:

  • Universal switching architecture/fabric for switching traffic at different layers (OTN, TDM and packet)
  • Ability to switch, groom, and manage traffic in its native format (i.e. SONET/SDH traffic as TDM traffic, and IP or Ethernet traffic as packet traffic), thus, allowing for the percentage of each traffic type to vary dynamically (all Ethernet to all SONET/SDH and anything in between, for instance)
  • Software-selectable ports that can switch between switching SONET/ SDH to switching Ethernet, depending on the traffic

Even as this definition is gaining industry consensus, according to research firm Heavy Reading, there are three architectures that are currently deemed to fall under the packet optical transport umbrella, shown in Figure 4.

Thus, P-OTS platforms provide the transport and PHY components of optical Ethernet networks (Figure 5).

Optical Ethernet Applications

So which applications/services are optical Ethernet being used for (or envisaged for) today?

Figure 4. Packet-Optical Transport Systems (P-OTS): Architectures in use today.
As expected, it is the business or residential services with triple-play applications (voice, video, and data to the desktop), mobile backhaul applications (where the Ethernet PHY is used between the base-station and the first switching node, and regular optical Ethernet networks are used in the backhaul and backbone networks), and utility infrastructure networks (where oil, gas, water, and electric utilities are transforming their aged communication systems into “data-aware” systems that allow for automation of functions such as billing, monitoring, meter reading).

Applications such as software-as-a-service, VoIP, VoD, and hosted unified communications are driving demand, as are ICT trends such as virtualization, data center outsourcing, data replication, disaster recovery, remote backup, and IT outsourcing.

How It All Fits Together

Figure 5. Optical Ethernet: How it all fits.
Thus, we see that in the trio that are the components of optical Ethernet — service, transport and PHY — Carrier Ethernet provides the service component, packet-optical transport gear provides the transport and PHY component, and the various IETF, IEEE, and ITU-T standards provide the specifications for the PHY layers, as well as connection-oriented Ethernet (Figure 5).

As optical Ethernet evolves over the next few years, there will be further reduction in the layers leading to a fused Ethernet-WDM packet transport layer with circuit-like capabilities, and to packet- optical systems optimized for it. This allows the providers to handle increasing volume of data traffic, while reducing the number of network elements by using Ethernet as the common packet technology in access, aggregation, and core networks.

This article was written by Vishal Sharma, Ph.D., Principal Consultant & Technologist, Metanoia, Inc. (Mountain View, CA) and Shahram Davari, MASc, Associate Technical Director, Network Switching, Broadcom Corporation (San Jose, CA). For more information, contact Dr. Sharma at This email address is being protected from spambots. You need JavaScript enabled to view it., Mr. Davari at This email address is being protected from spambots. You need JavaScript enabled to view it., or visit http://info.hotims.com/28050-201.

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