CN112788442A

CN112788442A - Method and system for bearing low-speed service in OTN (optical transport network)

Info

Publication number: CN112788442A
Application number: CN201911089580.5A
Authority: CN
Inventors: 王浩; 赵梓森
Original assignee: Fiberhome Telecommunication Technologies Co Ltd; Wuhan Fisilink Microelectronics Technology Co Ltd
Current assignee: Fiberhome Telecommunication Technologies Co Ltd; Wuhan Fisilink Microelectronics Technology Co Ltd
Priority date: 2019-11-08
Filing date: 2019-11-08
Publication date: 2021-05-11
Anticipated expiration: 2039-11-08
Also published as: CN112788442B

Abstract

The invention discloses a method and a system for bearing low-speed service in an OTN (optical transport network), relating to the technical field of transmission networks. After the data link layer is simplified, the time delay of the client signal transmitted in the network can be effectively reduced. By adopting a signal mapping mechanism, the complexity of chip design is reduced, the resource consumption of the chip is reduced, the design cost and the time cost of the chip are reduced, and the chip flow success rate is improved. According to the self-defined frame structure of the Tiny _ ODU, the Tiny _ ODU does not need a fixed length according to different low-speed service client signals, so that the frame length of the Tiny _ ODU is more flexible, and the BMP mapping efficiency is improved.

Description

Method and system for bearing low-speed service in OTN (optical transport network)

Technical Field

The invention relates to the technical field of transmission networks, in particular to a method and a system for bearing low-speed services in an OTN (optical transport network).

Background

Currently, SDH (Synchronous Digital Hierarchy) equipment is mature and applied in the field of transmission networks for many years, and the accessed client signals are SUB-1G (SUB 1Gbit/s client, low-speed client below 1G) services such as E1(30Pulse Code Modulation PCM in Europe, european 30-way Pulse Code Modulation). According to the analysis of the market share of the transmission network, the SDH network is in a trend of gradually disappearing in the market of the transmission network.

The access and bearer technology of Sub-1G, as a new technology to replace SDH networks, needs to provide a new mapping, multiplexing implementation scheme for E1 and the like. The method is required to be applied to an edge OTN (Optical transport network) network and needs to have reasonable bandwidth efficiency; the OTN network has the same functions of OAM (operation administration and maintenance) protection and the like as the existing OTN network; the service can be finally converged/fused into the characteristics of a standard OTN network and the like.

In the previous mapping and multiplexing methods, the data interleaving circuit is mostly implemented based on a cross matrix. This method is only suitable for the scenario where the total number of container slot divisions of the ODU0(Optical channel Data UNIT) is small. However, when the number of container timeslots of the ODU0 is large, for example, 80 timeslots, that means that the cross matrix has 80 input ports and 80 output ports, the complexity of the circuit increases exponentially, and at the same time, the consumed circuit resources become very large, and the circuit timing sequence is very poor, which is very unfavorable for the verification of the correctness of the early-stage function of the design, and becomes a technical bottleneck of the whole design scheme.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method and a system for bearing a low-speed service in an OTN (optical transport network), which simplify the mapping path from a client signal to an ODU (optical data Unit) signal in an SDH (synchronous digital hierarchy) network, make the mapping processing more concise and reduce the mapping complexity.

In order to achieve the above purposes, the technical scheme adopted by the invention is as follows: a method for carrying low-speed service in an OTN network comprises the following steps:

mapping a low-speed service client signal to a self-defined optical channel data small unit Tiny _ ODU by adopting a bit synchronization mapping mechanism BMP;

an ODU0 payload area is divided into a plurality of micro-slots, and Tiny _ ODU corresponding to different low-speed service client signals are respectively mapped into the micro-slots of an optical channel data unit ODU0 by adopting a predefined signal mapping mechanism.

On the basis of the above scheme, dividing the payload area of the ODU0 into a plurality of minislots specifically includes the following steps:

the ODU0 payload area is divided into two identical groups, each of which is divided into 476 minislots, each of which occupies 128 bits of data space.

On the basis of the above scheme, a predefined signal mapping mechanism is adopted to map the Tiny _ ODUs corresponding to different low-speed service client signals into the minislots of the ODU0, which specifically includes the following steps:

caching data of various Tiny _ ODUs corresponding to different low-speed service client signals into an FIFO;

configuring a mapping relation between each Tiny _ ODU and each micro time slot;

when data of a certain Tiny _ ODU needs to be transmitted, the data are read from the FIFO of the Tiny _ ODU, and the read data of the Tiny _ ODU are filled into the micro time slot corresponding to the Tiny _ ODU in the ODU0 according to the mapping relation between each Tiny _ ODU and each micro time slot.

On the basis of the above scheme, when the mapping relationship between each Tiny _ ODU and each micro-slot is configured, one Tiny _ ODU corresponds to a plurality of random or continuous micro-slots.

On the basis of the above scheme, the Tiny _ ODU includes an overhead region and a payload region, the overhead region is 16 bytes in length, and the payload region is a multiple of 16 bytes in length.

On the basis of the above scheme, the overhead area includes: frame alignment mark, multi-frame alignment mark, path monitoring mark, automatic protection switching mark, regulation control mark and micro time slot mark.

On the basis of the above scheme, the low-speed service client signal includes one or more of an E1 signal, an STM-1 signal, a VC12 signal, a VC3 signal, a VC4 signal, and an FE signal.

The invention also provides a system for bearing the low-speed service in the OTN network, which comprises:

a Tiny _ ODU mapping module to: mapping a low-speed service client signal to a multi-path self-defined optical channel data small unit Tiny _ ODU by adopting bit synchronization mapping BMP;

an ODU0 mapping module to: an ODU0 payload area is divided into a plurality of micro-slots, and Tiny _ ODU corresponding to different low-speed service client signals are respectively mapped into the micro-slots of an optical channel data unit ODU0 by adopting a predefined signal mapping mechanism.

On the basis of the above scheme, the ODU0 mapping module divides an ODU0 payload area into a plurality of micro slots, and specifically includes the following steps:

the payload area of the ODU0 is divided into two identical groups, each group is divided into 476 minislots, and one Tiny _ ODU corresponds to a plurality of random or continuous minislots.

On the basis of the above scheme, the ODU0 mapping module maps Tiny _ ODUs corresponding to different low-speed service client signals into micro-slots of the ODU0 by using a predefined signal mapping mechanism, specifically including the following steps:

On the basis of the above scheme, when the ODU0 mapping module configures a mapping relationship between each Tiny _ ODU and each micro-slot, the number of micro-slots corresponding to the Tiny _ ODU is equal to the length of the Tiny _ ODU/the size of the micro-slot.

Compared with the prior art, the invention has the advantages that:

the technical scheme of the invention simplifies the mapping path from the low-speed service client signal to the ODU0 signal in the SDH network, so that the mapping processing of the signal is simpler and the mapping complexity is reduced. After the data link layer is simplified, the time delay of the client signal transmitted in the network can be effectively reduced. By adopting a self-defined signal mapping mechanism, the complexity of chip design is reduced, the resource consumption of the chip is reduced, the design cost and the time cost of the chip are reduced, and the chip flow success rate is improved.

According to the self-defined frame structure of the Tiny _ ODU, the Tiny _ ODU does not need a fixed length according to different low-speed service client signals, so that the frame length of the Tiny _ ODU is more flexible, and the BMP mapping efficiency is improved.

The containers of the ODU0 may carry a greater number of client signals through the partitioning of micro-slots. The carrying of more e.g. E1 and STM-1 signals at the same bandwidth capacity is greatly improved.

Drawings

Fig. 1 shows a frame structure of a custom Tiny _ ODU according to an embodiment of the present invention;

fig. 2 is a hierarchy of customer signals to ODU0 containers in an embodiment of the invention;

fig. 3 is a schematic diagram of partitioning the Micro _ TS by the ODU0 container in the embodiment of the present invention;

FIG. 4 illustrates a scheduler-based signal mapping mechanism according to an embodiment of the present invention;

fig. 5 is a schematic diagram illustrating an evolution trend of a 5G transmission network according to an embodiment of the present invention;

fig. 6 is a schematic diagram of a specific implementation of a method for mapping a low-speed service to an ODU signal 0 according to an embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

The embodiment of the invention provides a method for bearing a low-speed service in an OTN network, which comprises the following steps:

The mapping path in the prior art adopting the SDH scheme is: client → (LO map) → VC-N → (MUX) → AU4 → STM-N → (BMP) → ODU; the mapping path of the mapping method from the low-speed service to the ODU signal adopted in the embodiment of the present invention is as follows: Sub-1G client → (BMP) → Tiny _ ODU → (signal mapping mechanism) → ODU 0. Therefore, the embodiment of the invention simplifies the mapping path from the low-speed service client signal to the ODU0 signal in the SDH network, so that the mapping processing of the signal is simpler, and the mapping complexity is reduced. After the data link layer is simplified, the time delay of the client signal transmitted in the network can be effectively reduced.

The embodiment of the invention firstly defines a brand-new Tiny _ ODU (Tiny optical channel Data UNIT).

The Tiny _ ODU is a container for carrying low-speed services, and can carry low-speed services such as E1 and STM-1(Synchronous Transport Module level-1). The low-speed service client signal of the embodiment of the invention also comprises the following components besides the E1 signal and the STM-1 signal: VC12(Virtual Container12 ) signal, VC3(Virtual Container3, Virtual Container 3) signal, VC4(Virtual Container 4) signal, FE (Fast Ethernet) signal. It is constructed based on a 16-byte cell length, which is an OH (overhead) field and a PL (Pay Load) field, respectively, where the OH field length is 16 bytes and the PL field length is a multiple of 16 bytes, as shown in fig. 1. According to different low-speed service client signals, the length of the Tiny _ ODU does not need to be fixed, so that the frame length of the Tiny _ ODU is more flexible, and the BMP mapping efficiency is improved. The client signal is normally transmitted continuously, so the PL area of the Tiny _ ODU is always a multiple of 16 bytes. Only in the case of a sudden interruption of the client signal, the PL area of the Tiny _ ODU has a phenomenon that the last byte is less than 16 bytes, and at this time, the client signal is regarded as an abnormal signal and no further conversion processing is performed.

The overhead part mainly comprises: FAS (Frame Alignment Signal), MFAS (multi Frame Alignment Signal), PM (Path Monitoring), APS (Automatic Protection Switching), JC (notification Control), Micro _ TS ID (Micro Time Slot Indication), and reserved bytes.

The specific mapping process of the client signal to the ODU0 container is as follows:

the hierarchy of the customer signal with the Tiny _ ODU hierarchy and the OPU0(Optical Channel Payload Unit) and ODU0 is shown in fig. 2.

The embodiment of the invention defines a brand-new time slot division mechanism and scheme of the ODU0 container. The payload area of ODU0 is divided into 2 groups, each Group being divided into 476 minislots (Micro _ TS) based on about 2.5M, with minislot interleaving being performed at 128 bits, as shown in fig. 3.

The reason for this is that the rate of the E1 signal is 2.048Mbit/s, which corresponds to a Tiny _ ODU rate of about 2.4 Mbit/s. And the minimum effective bandwidth of Micro _ TS requires E1 capable of carrying 1 hard channel.

The embodiment of the invention defines a brand-new mapping device and method of a signal mapping mechanism based on a scheduling mechanism. The structure mode of the data interleaving scheme of the signal mapping mechanism defined in the embodiment of the present invention is shown in fig. 4, wherein a Scheduler (Scheduler) is a structure mode based on a linked list (Calendar), and each configuration Entry (Entry) and the sequence of Micro _ TS are in a one-to-one correspondence relationship. The content of each entry is the channel number of the Tiny _ ODU to be transmitted by the corresponding Micro _ TS. And sequentially mapping the multiple paths of Tiny _ ODUs into different Micro _ TSs of the ODU0 by adopting a signal mapping mechanism according to a Calendar scheduling sequence configured in advance by a Scheduler.

Furthermore, the embodiment of the invention can enable the low-speed services such as E1 and the like which can only be accessed in the SDH network before to be quickly merged into the standard OTN network, and the simplified and optimized network structure is as shown in figure 5. Wherein, a and b in fig. 5 illustrate the structure of the prior art network, and c in fig. 5 illustrates that the network of a and b can be fully merged and replaced after the embodiment of the present invention is applied.

In order to make the technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention are described in detail below with reference to fig. 6 and the embodiments. The embodiment of the present invention is described by taking VC12(Virtual Container12 ) signal as an example of the client signal. The embodiment of the invention is simultaneously suitable for various low-speed service client signals such as E1, STM-1 and the like.

After completing Tiny _ ODU mapping and encapsulation by means of BMP, VC12 client signals of 476 channels need to be mapped into a payload area of ODU0 according to a signal mapping mechanism.

S1: the rate of the client signal VC12 is 2.24Mbit/s, and the byte amount of continuous 10 frames is 1400 bits. An 8-bit idle signal of 0 is added at the end of the consecutive 10 frames and the data reconstruction amounts to 1408 bits in length. The rate is adjusted as follows: 2.24Mbit/s (1408/1400) ═ 2.253 Mbit/s. The idle signal 0 is added by adding 0 after the low bit of the data and pulling up the data valid indication signal aiming at the 8bit, thereby completing the data addition.

S2: through BMP mode, map into Tiny _ ODU (VC12) signal, its frame length is 12 128 bits, the 1 st 128bit is overhead, the latter 11 128 bits are payload. The speed of the Tiny _ ODU (VC12) is 2.2528Mbit/s (12/11) ═ 2.458 Mbit/s.

The implementation process of BMP, that is, the implementation process of Tiny _ ODU framing, is as follows:

firstly, the data envelope of the Tiny _ ODU corresponding to the client signal needs to be carved out under a local clock according to the rate of the client signal.

Secondly, in order to ensure uninterrupted transmission of data stream, a FIFO (First Input First Output) device is required to buffer the client signal data. The valid indication of the client signal is write enable of the FIFO, and the client signal data is write data of the FIFO, and the FIFO write operation is performed. And the payload area envelope of the data envelope of the Tiny _ ODU is used as a read enable signal of the FIFO, and the data buffered in the FIFO is read out to be used as the payload of the Tiny _ ODU, so that the FIFO read operation is completed.

Thirdly, the corresponding overhead indication needs to be filled in the overhead area of the data envelope of the Tiny _ ODU. The whole framing operation from the client signal to the Tiny ODU is thus finished.

S3: the payload area of ODU0 is divided into exactly the same 2 groups, each consisting of 476 slots. The bandwidth of each Micro _ TS is 2.603 Mbit/s. The division strength is 128 bits, that is to say, each Micro _ TS occupies 128 bits of data space.

S4: according to the channel number of the Tiny _ ODU (VC12) required to be transmitted, the calendar information of a scheduler, the depth of which is fixed to 476, is configured. Each entry of the calendar of the scheduler corresponds to a Micro time slot of the ODU0 one by one, and the content of each entry is a channel number of a Tiny _ ODU to be transmitted by a corresponding Micro _ TS; if a Tiny _ ODU (VC4) needs to occupy multiple Micro _ TS scenarios, for example, a VC4 service with a number of 0 occupies 8 entries, then all of entries 0 to 7 of the scheduler belong to the VC4 service with a number of 0.

S5: OMFI (OPU Multi-Frame Indication, OPU multiframe Indication signal) is set to 80, the multiframe period is about 8ms, and there are 2 × 80 to 160 Micro _ TS groups in the multiframe. The 8ms multiframe design enables the service to have sufficient time margin to perform relevant operations when performing protection switching.

S6: the CM (number of M-bit Client data entries, number of M-bit Client data) value of each Tiny _ ODU is subjected to padding operation by using C128, and the padding algorithm is a delta-sigma algorithm, wherein the delta-sigma algorithm is a general algorithm in an OTN system, and the embodiment of the present invention is not described in detail.

S7: as shown in fig. 6, according to the calculated CM value, that is, according to the delta-sigma algorithm, the read enable signal of each data buffer is controlled at the same time, so that the depth of each buffer is minimized, the time delay of the whole service path is minimized, and the implementation of the whole signal mapping mechanism is completed.

The signal mapping mechanism is realized by the following steps:

first, a Scheduler, i.e., Scheduler, is required to perform scheduling management on the Tiny _ ODU of multiple channels. The caller is realized based on a linked list, namely, a CALENDAR mode, and configuration entries of the CALENDAR, namely, each Entry corresponds to 1 Micro _ TS. And flexibly configuring the content application software of each Entry, wherein the configuration information is the channel number of the Tiny _ ODU, and the Tiny _ TS represents that the Tiny _ TS is occupied by the Tiny _ ODU of the corresponding channel.

Next, the calendar reads the configuration information of Entry 0-Entry 475 cyclically when the circuit starts to operate. When the Entry information output by the scheduler indicates that a channel of the Tiny _ ODU needs to be transmitted, the 128-bit data of the FIFO of the Tiny _ ODU that buffers the channel is read, that is, the data of 1 address in the buffer is read. And then selecting a 1 circuit through 476, filling the read data of the Tiny _ ODU as the payload content of the ODU0 container into a micro-slot corresponding to the configuration entry of the payload area of the ODU0 container, and pulling up the data valid indication signal of the ODU 0.

Again, the overhead area of the data envelope of the ODU0 container needs to be filled with the corresponding overhead indication. Thus, the implementation of the whole signal mapping mechanism from the Tiny _ ODU to the ODU0 is completed.

The embodiment of the present invention further provides a system for loading a low-speed service in an OTN network, including:

As a preferred embodiment, the ODU0 mapping module divides an ODU0 payload area into a plurality of minislots, and specifically includes the following steps:

As a preferred embodiment, the ODU0 mapping module maps the Tiny _ ODUs corresponding to different low-speed service client signals into micro-slots of the ODU0 by using a predefined signal mapping mechanism, specifically including the following steps:

As a preferred embodiment, when the ODU0 mapping module configures a mapping relationship between each Tiny _ ODU and each micro slot, one Tiny _ ODU corresponds to multiple random or continuous micro slots.

As a preferred embodiment, the Tiny _ ODU includes an overhead region and a payload region, the overhead region has a length of 16 bytes, and the payload region has a length that is a multiple of 16 bytes.

As a preferred embodiment, the overhead area includes: frame alignment mark, multi-frame alignment mark, path monitoring mark, automatic protection switching mark, regulation control mark and micro time slot mark.

As a preferred embodiment, the low-speed service client signals include one or more of E1 signals, STM-1 signals, VC12 signals, VC3 signals, VC4 signals, and FE signals.

Based on the same inventive concept, embodiments of the present application provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements all or part of method steps of a method for carrying low-speed traffic in an OTN network.

The present invention realizes all or part of the flow of the method for carrying the low-speed service in the OTN network, and may also be completed by instructing the related hardware through a computer program, where the computer program may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the above-mentioned method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying computer program code, recording medium, U.S. disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution media, and the like. It should be noted that the computer readable medium may contain other components which may be suitably increased or decreased as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, in accordance with legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunications signals.

Based on the same inventive concept, an embodiment of the present application further provides an electronic device, which includes a memory and a processor, where the memory stores a computer program running on the processor, and the processor executes the computer program to implement all or part of method steps in a method for loading a low-speed service in an OTN network.

The Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. The general purpose processor may be a microprocessor or the processor may be any conventional processor or the like, the processor being the control center of the computer device and the various interfaces and lines connecting the various parts of the overall computer device.

The memory may be used to store computer programs and/or modules, and the processor may implement various functions of the computer device by executing or executing the computer programs and/or modules stored in the memory, as well as by invoking data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required by at least one function (such as a sound playing function, an image playing function, etc.), and the like; the storage data area may store data (such as audio data, video data, etc.) created according to the use of the cellular phone, etc. In addition, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other volatile solid state storage device.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, server, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.

The present invention has been described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), servers and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A method for carrying low-speed service in an OTN network is characterized by comprising the following steps:

2. The method of claim 1, wherein dividing the ODU0 payload area into a plurality of minislots, specifically comprises the steps of:

3. The method according to claim 2, wherein a predefined signal mapping mechanism is adopted to map a Tiny _ ODU corresponding to different low-speed service client signals into minislots of an ODU0, and the method specifically includes the following steps:

4. The method of claim 3, wherein when the mapping relationship between each Tiny _ ODU and each micro-slot is configured, one Tiny _ ODU corresponds to a plurality of random or continuous micro-slots.

5. The method of claim 1, wherein the Tiny _ ODU comprises an overhead region and a payload region, wherein the overhead region is 16 bytes in length, and wherein the payload region is a multiple of 16 bytes in length.

6. The method of claim 5, wherein the overhead region comprises: frame alignment mark, multi-frame alignment mark, path monitoring mark, automatic protection switching mark, regulation control mark and micro time slot mark.

7. The method of claim 1, wherein the low-speed service client signals include one or more of E1 signals, STM-1 signals, VC12 signals, VC3 signals, VC4 signals, and FE signals.

8. A bearer system for low-speed traffic in an OTN network, comprising:

9. The system of claim 8, wherein the ODU0 mapping module divides an ODU0 payload area into a plurality of minislots, specifically comprising the steps of:

10. The system of claim 9, wherein the ODU0 mapping module is configured to map, to micro timeslots of the ODU0, Tiny _ ODUs corresponding to different low-speed service client signals by using a predefined signal mapping mechanism, and specifically includes the following steps:

11. The system of claim 10, wherein when the ODU0 mapping module configures a mapping relationship between each Tiny _ ODU and each micro slot, one Tiny _ ODU corresponds to multiple random or consecutive micro slots.

12. The system of claim 8, wherein the Tiny ODU comprises an overhead region and a payload region, wherein the overhead region is 16 bytes in length, and wherein the payload region is a multiple of 16 bytes in length.

13. The system of claim 12, wherein the overhead area comprises: frame alignment mark, multi-frame alignment mark, path monitoring mark, automatic protection switching mark, regulation control mark and micro time slot mark.

14. The system of claim 8 wherein the low speed service client signals include one or more of E1 signals, STM-1 signals, VC12 signals, VC3 signals, VC4 signals, and FE signals.