OTN

With the rapid growth of data traffic in today’s networks, there is a greater need to handle traffic at larger granularities, to pack traffic more efficiently, and to be able to scale to larger signal rates of 100G and beyond that is not possible with legacy SONET/SDH technologies. Also, as the transport networks grow larger, they have to be partitioned into several regions or subnets. Since many operators synergize their networks to provide end-to-end services, an easy management of operator-to-operator handoffs is needed. In order to solve these problems, ITU-T laid down the specifications of the Optical Transport Network (OTN). ITU-T provides the general requirements in the G.872 standard and the interface definitions in the G.709 standard.

 OTN transport has been in use for a decade, beginning with its use in Submarine Line Terminal Equipment (SLTE) applications in the 1990s. G.709 OTN was originally defined as a point-to-point protocol, designed to provide a protocol-independent wrapper of client data to “containerize” and provide fully transparent transport for a variety of Gigabit-speed services such as Ethernet, Fibre Channel, and wavelength services. Today OTN switching is regarded as the most cost-effective layer for point to point traffic between 1Gbs and 10Gbs.  In addition, OTN provides several advantages such as: i) enhanced Forward Error Correct (FEC) based on Reed-Solomon 255/239 code for reduced amplification expenses on longer fiber spans by providing a 6.2dB advantage over SONET/SDH FEC mechanism, ii) six levels of tandem connection monitoring (TCM) for hierarchical management of multi-vendor/multi-operator networks compared to just one in the case of SONET/SDH, iii) efficient sub-lambda grooming of transit traffic on partially filled high-capacity wavelengths at 100G/100G+, and iv) lower build and operational costs by reducing the use of energy-intensive routers through traffic bypass over the OTN layer at express locations. 

Tejas offers the latest generation of converged packet optical (CPO) products that combine Wavelength, SDH, Ethernet and OTN switching in a single network element while delivering services across a common infrastructure.  By combining these diverse capabilities, Tejas CPO can ensure the most cost effective transport of traffic by grooming traffic at the lowest cost layer in the network.  

Tejas implementation of OTN switching on its CPO and PTN products offers several valuable benefits to telecom service providers:

  1. Support for OTN mapping on both access and core network equipment  nodes which is useful for delivering high bandwidth, point-to-point services, typically above 1Gbps speed
  2. Comprehensive OAMP diagnostic messages for loss of signal/frame (LOS/F), alignment errors (TIM), frame errors (BIP-8, BEI), alarm indications (AIS, BDI) along with a range of linear/ring protection and mesh restoration schemes with an automated GMPLS control plane
  3. Low latency and transparent service delivery with asynchronous service mapping which is especially useful for security-sensitive applications (e.g., defence, banking etc) and time-sensitive applications (video streaming, video conferencing etc)
  4. ODUflex feature allows custom bit-rate mapping for signals such as GPON, SDI, CPRI etc thereby reclaiming valuable bandwidth in access networks battling fiber exhaust issues
  5. Bulk encryption can be performed with fixed-size frames and can be uniformly applied to clients of all types without throughput penalty since there is no per-packet overhead. OTN encryption is not susceptible to traffic analysis and the larger size of frames makes cryptanalysis significantly harder.