Infonetics Research says optical network providers are making a major push to the Optical Transport Network (OTN) for metro, long haul and ultra long haul transmision. Until now, carriers have mostly used SONET/SDH for optical transport but that seems about to change in a big way.
Infonetics interviewed telcos in North America, Asia Pacific, EMEA, and CALA were interviewed about their plans for optical transport networks for their new report titled, OTN Deployment Strategies: Global Service Provider Survey. The service providers interviewed represent a significant 23% of worldwide 2010 telecom capex and are a mix of incumbents (52%), competitive operators (32%), and mobile operators (16%) from North America, EMEA, Asia Pacific, and Central and Latin America.
Infonetics Optical Analyst Andrew Schmitt (and author of the aforementioned report) stated,
“All of the carriers we interviewed for our OTN survey have deployed OTN interfaces in transport applications, and based on conversations aside from this survey, we know very few major carriers in general will ‘skip’ OTN. There is a huge shift between now and 2014 in the area of optical switching, with the number of carriers with plans to deploy OTN interfaces on electrical switching equipment rising from 37% to 84%.”
The Optical Transport Network (OTN) was defined over 11 years ago by ITU-T SG 15. It is a set of Optical Network Elements (e.g. DWDM), connected by optical fiber links, which provides functions such as transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals. Optical network providers worldwide are steadily evolving from a pure SONET/SDH infrastructure to the OTN, because it better supports packet traffic and can operate at higher speeds.
There were several key advantages envisioned for the OTN (when compared to SONET/SDH):
- It is based on DWDM being used to partition an optical fiber into multiple wavelengths/channels
- It can encapsulate both SONET/SDH as well as pure packet (e.g. Ethernet) payloads
- It can be used for comprehensive end to end fault isolation through stack-like operation (in SONET/SDH, the Section overhead gets changed after transiting each optical network element/regenerative repeater)
- It would evolve to support higher speeds than SONET/SDH, which was scheduled to top out at 40G (OC-192)
- Fast optical path provisioning and rapid restoration (from failures) would be faciliatated by an optical control plane (AKA G.ASON or G-MPLS)
ITU-T Recommendation G.709 is the foundation standard for Optical Transport Network (OTN) (also called “digital wrapper” or “optical channel wrapper”). OTN is currently offered in the following line rates.
- OTU1 has a line rate of approximately 2.66 Gbit/s and was designed to transport a SONET OC-48 or synchronous digital hierarchy (SDH) STM-16 signal.
- OTU2 has a line rate of approximately 10.70 Gbit/s and was designed to transport an OC-192, STM-64 or WAN PHY (10GBASE-W).
- OTU2e has a line rate of approximately 11.09 Gbit/s and was designed to transport an 10 gigabit Ethernet LAN PHY coming from IP/Ethernet switches and routers at full line rate (10.3 Gbit/s). This is specified in G.Sup43.
- OTU3 has a line rate of approximately 43.01 Gbit/s and was designed to transport an OC-768 or STM-256 signal or a 40 Gigabit Ethernet signal.
- OTU3e2 has a line rate of approximately 44.58 Gbit/s and was designed to transport up to four OTU2e signals.
- OTU4 has a line rate of approximately 112 Gbit/s and was designed to transport a 100 Gigabit Ethernet signal.
Note: A full OTN Tutorial is available from the ITU’s web site at: www.itu.int/ITU-T/studygroups/com15/otn/OTNtutorial.pdf
Infonetics OTN Survey Highlights:
- 74% of respondent service providers plan to eventually deploy electrical ODU (optical data unit) switching
- 71% of the carriers interviewed have deployed or will deploy ODU-2/1/0 switching in the core and the metro by the end of 2011
By 2014, 40G and 100G ODU switching will each be prevalent in over half of all metro networks
- The traditional service multiplexing features of OTN are by far the most important in the eyes of carriers
- 52% of metro optical ports support OTN, but only a fraction are enabled and transmitting using this Physical layer frame format.
For the OTN Deployment Strategies: Global Service Provider Survey, Infonetics interviewed purchase decision-makers with detailed knowledge of their company’s OTN transmission and switching equipment about their use and plans for OTN transport. Respondent carriers were asked about preferred equipment used with OTN interfaces; plans for electrical OTN switching in core and metro networks (what level and when); their ratings of various OTN applications (such as service multiplexing onto a single wavelength, ASON/G-MPLS optical control plane automation, optical private line service delivery, etc.); whether to combine DWDM, OTN switching, and Ethernet/MPLS switching; and more.
In a separate report, Infonetics Research forecasts the10G, 40G, and 100G transceiver and transponder market to grow to $2.8 billion worldwide by 2015. The firm reports that 10G optical transceiver/transponder revenue jumped 160% in 2010, but 10G growth will slow as the market shifts to more compact form factors with less electronics and lower ASPs. Infonetics 10G/40G/100G Optical Transceivers Market Size and Forecast report highlights did not break out its forecast by optical technology type, e.g. Fiber Channel, 10G/40G/100G Ethernet, SONET/SDH, OTN, etc. However, the market research firm states that network equipment manufacturers are supplying an increasing share of high speed optical ports.
PMC-Sierra’s CEO expects a huge ramp up in OTN deployment in the next five years. During their earnings call a few weeks ago, PMC’s CEO Gregory Lang stated:
“For the full year, we’re estimating about $10 million in OTN revenue, subject to the Verizon deployment schedule in the U.S. and when AT&T starts its OTN deployments. And based on external third-party data, the adressable market for OTN semiconductors is expected to grow at a CAGR of about 30% over the next five years from $140 million to about $550 million in 2015. Now this may be a bit aggressive, but the deployment of OTN equipment will happen as carriers worldwide transition to packet-based network equipment.”
Steve Gorsche, PMC’s ITU-T delegate,adds, “The OTN standards have made major evolutionary steps in the past three years. Support was added for efficient transport of 1, 40 and 100 Gbit/s Ethernet, as well as a flexible method for carrying a variety of new constant bit rate and packet client signals. These new capabilities have greatly increased the value of OTN for the carriers.”
A Tutorial on ITU-T G.709 Optical Transport Networks (OTN), written by Steve Gorsche is available at:
Steve is a multi-decade colleague of this author and he is highly respected for his professional accomplishments.
It appears the main incentive for carriers to now move from SONET/SDH to the OTN is encapsulation of aggregated IP and Ethernet traffic. We see this starting with 10G Ethernet and then evolving to 40G and !100G Ethernet in data centers, Internet exchanges, and for other aggregated long haul packet traffic. Yet the TDM traffic in SONET payloads can also be ampped to ODUs and combined with packet based ODUs in a single OTUi frame.
Why hasn’t the OTN been deployed sooner (since it was standardized by ITU over 11 years ago)? The reason is that it’s an entirely new network infrastructure! Not only does the OTN require all new optical network elements (DWDM transponders, optical switches, routers, etc), but an entirely new network management and provisioning system. But now, with the explosion in high bandwidth traffic (mostly video), the operators have little choice but to move rather quickly to deploy OTN equipment and related management and operations support systems.
With OTN deployment forecast to accelerate, there are several critical questions for the carriers deploying it:
- Is carrier aggregation of packet traffic really the biggest driver of the OTN? If so, what traffic types predominate?
- With little use of GMPLS/G.ASON for optical control plane, what else will be used for fast (circuit path) provisioning/re-provisioning, rapid restoration (on failure), and adjacent (optical network element) discovery?
- Considering that most high speed routers have either 10GE or SONET/SDH uplinks, will OTN switches also support those (with internal PHY framing/ protocol conversion) in addition to native OTN ports?
- As the OTN network management (EMS, NMS, OSS) is completely new, how will it co-operate with SONET/SDH network management in the carrier’s total network? There will be only a few greenfield carriers that go directly to OTN without also having an embedded base of SONET/SDH optical network elements and management systems.
- Will Internet Exchanges deploy 40GE/100GE directly over DWDM (as per the standard) or map those to the OTN for optical network transport?