ODU0 / ODUflex

Overview

When the OTN emerged in the late 1990's as the natural successor to SONET/SDH the smallest container envisaged by the network architects was OTU1 (~2.5G/bps).  At this time the method for mapping 1GbE clients in to this container was GFP*.  While this method is perfectly valid, it has the side affect of wasting 50% of the available bandwidth of the OTU1 payload (when carrying only 1 x 1GbE client) or losing supervision / management control when multiplexing 2 x 1GbE clients in to the OTU1 payload (GFP linear extension).  Using GFP at this level also means that timing is difficult to maintain which is a real problem for packet networks relying on synchronous Ethernet.

These mapping inefficiencies and timing problems combined with the convergence of packet / TDM networks has forced the ITU-T to standardize a new container to efficiently carry 1GbE clients across the OTN.  This container is called ODU0.  ODU0 has been defined with a payload of 1.238G/bps which is perfectly sized to minimize bandwidth wastage when carrying 1 or multiple 1GbE clients across the network.  The introduction of a new sub 2.5Gb ODU container also introduces a much smaller granularity of switching in the OTN than was available before, allowing the Network operators to maximize their revenues.

While ODU0 solves the problem of efficiently carrying 1GbE clients over the OTN, there are a constant stream of packet clients that demand the same attention (FibreChannel, native video etc).  To accommodate all current and future clients the ITU-T defined ODUflex.  Flex differs from the ODU0 mapping shown above in that it allows the client payload size to vary.  This flexibility allows the ODUk/OPUk overhead to wrap tightly around the client, thereby maximizing bandwidth usage.  The use of BMP* and GMP* allows both client & container rates to vary.

See the diagram opposite to understand how these next generation clients are mapped in to the OTUx payload.

GFP* (Generic Framing Procedure).

GMP* (Generic Mapping Procedure).

AMP* (Asynchronous Mapping Procedure).

BMP* (Bit Synchronous Mapping Procedure).

Aliathon Solution

Aliathon OTN products can be tailored to support the latest derivatives of the G.709 standard, including ODU0 & ODUflex.  Applications for this exciting new technology includes but is not limited to the following;

• Native 1GbE support in traditional telco networks (Metro-MSPP etc).
• OTN backhaul.
• CPRI over OTN (Cloud RAN).
• HD video transport over the OTN.
• Fibrechannel (or generic data) storage over the OTN.

We are expert at delivering the perfect mix of features, performance, flexibility, power and cost for your current and future needs.  Click here to contact us and discuss your project requirements...

References

• OTN (Wikipedia)
• ITU-T G.709 Specification