Patent Application
20150358431
The present disclosure relates to enabling mapping of virtual lanes for data streams for transmission over an optical transport network.
Higher-speed Ethernet typically has to use existing copper (electrical) and fiber (optical) cables, e.g., in a data center and over the Internet. At this point in time, no technology exists to transport data at rates of 40 or 100 gigabits per second (G) as a single (serial) stream over both copper and fiber media between endpoints, but such transport becomes possible when the traffic is subdivided and transmitted via a plurality of lower data rate channels or virtual lanes. To assist the conversion between optical and electrical transmission, the Institute of Electrical and Electronics Engineers (IEEE) has established the 802.3ba standard for 40 G and 100 G for transmission over networks, e.g., the Internet. The 802.3ba standard implements the use of “virtual lanes” that subdivide the higher data rate optical signals for processing by lower data rate electronics at the physical coding sublayer (PCS). For example, a 40 G optical data rate may be subdivided into 5 G PCS units or lanes for electrical processing. In essence the 40 G data is multiplexed across 5 G lanes, e.g., eight lanes (40 G divided by 5 G).
Techniques are described herein for enabling mapping of virtual lanes for data streams for transmission over an Optical Transport Network (OTN). Line encoded data blocks of a first data stream are distributed at an endpoint device in an OTN. The line encoded data blocks of the first data stream are distributed across a plurality of second data streams such that the second data streams can be processed at a lower data rate than a data rate associated with the first data stream. A transcoding operation is performed on the data packets of each of the second data streams to generate transcoded data packets. The transcoded data packets are processed such that the transcoded data packets of each of the second data streams can be sent over the OTN at the lower data rate.
Optical transport networks (OTN) generally comprise a number of optical fibers that are deployed over large geographical areas. Optical transport, in general, is quickly moving towards implementations for transmission of 100 Gigabit per second (100 G) data that can be widely deployed in the next few years, and solutions for 400 G and 1 Terabits per second (T) transport have been announced. As such, it is expected that further optical network standards will be released that support these and other line rates and signal speeds.
As described above, networks have been developed to employ both optical and electrical media for data transmission, and the optical data rates have evolved to transmit data at higher rates over an optical physical (PHY) link than those economically achieved over an electrical PHY link. In many environments optical signals are converted to electrical signals, and vice versa. For example, certain optical wavelengths (X) may be “dropped” at an optical network node. The data in the dropped wavelength are converted from the optical form and may be retransmitted over an electrically based network. The optical wavelengths may also need to be reconditioned via electrical processing due to optical path signal loss and optical distortions, and thereafter retransmitted over optical media. Due to the cost of the electrical conversion components, lower data rate electronics are preferred in some environments. PCS virtual lanes are employed to allow processing of high bandwidth protocols at lower speed. Virtual lanes enable encoded data blocks of a first data stream to be distributed across a plurality of second data streams such that the second data streams are processed at lower data rates than data rates associated with the first data stream. Virtual lanes may be created by an optical node that is part of an OTN, and data may be distributed across the virtual lanes by the optical node. Thus, the virtual lanes implemented by the optical node enable high data rate optical signals to be divided into streams of lower data rate optical signals across the virtual lanes. For example 40 G data may be subdivided into eight 5 G virtual lanes. Ideally, the data of the virtual lanes would be configured to be mapped in the OTN such that the data from the virtual lanes can traverse the OTN to a destination optical node.
An example optical environment for enabling mapping of virtual lanes in an OTN is shown in
To ensure that data streams of the virtual lanes at each optical node are able to be transmitted in the OTN 130 at lower data rates associated with the virtual lanes, each of the nodes 110 and 120, i.e., endpoint nodes, has virtual lane mapping software 150 and supporting hardware. As described herein, the virtual lane mapping software 150 enables the optical nodes 110 and 120 to perform transcoding operations on data packets of virtual lanes and to process transcoded data packets such that the transcoded data packets can be sent over the OTN 130.
Reference is now made to
The adjustable rate communications enable the optical nodes 110 and 120 to negotiate from each other the number of virtual lanes (and thus the bandwidth) to be used for data communications across the OTN 130. This negotiation is used to activate (or deactivate) one or more virtual lanes, and optical nodes can negotiate to activate extra virtual lanes to match a maximum bandwidth allowable by physical connections used by the communication interface. For example, if a maximum bandwidth of the physical connections increases, the optical nodes can negotiate to activate additional virtual lanes to fill up the extra available bandwidth in the OTN 130. Similarly, if a maximum bandwidth of the physical connections decreases, the nodes can negotiate to de-activate virtual lanes to match the smaller available bandwidth in the OTN 130.
Each of the MAC modules 204(a)-204(n) generates one or more processed data streams for transmission along one or more virtual lanes.
In current network environments, fixed hierarchical data rates vary significantly, and virtual lanes may be deployed at optical nodes to optimize packet transmission with finer increments allowed by existing fixed rate standards. On the other hand, OTN networks are increasingly becoming widely adopted, and often data from the virtual lanes cannot be mapped over the OTN at the lower data rates. For example, even though the virtual lanes at an optical node may enable 40 G data to be mapped into multiple 5 G virtual lanes, existing OTN technology does not allow the individual 5 G data of the virtual lanes to be sent at the 5 G data rate across the OTN 130. Existing standards have been developed to enable traffic to be mapped over an OTN, but these existing standards lose the data rate granularity provided by virtual lane technology. For example, the International Telecommunication Union (ITU) standard G.709 provides a general framework for mapping data traffic over OTNs, but as currently defined, the G.709 standard does not allow for preservation of the virtual lane-to-MAC module mapping performed by an optical node before data transmission. In other words, the G.709 standard lacks transparency for maintaining the virtual lane-to-MAC module mapping as data packets in specific virtual lanes (corresponding to specific MAC modules) are sent in the OTN 130. Without such transparency, it is difficult, if not impossible, for endpoint optical nodes to reassemble or reorder packet streams in a virtual lane in an appropriate order as they correspond to the specific MAC modules.
The techniques described herein alleviate these drawbacks by transcoding data packets on each of the virtual lanes and processing the transcoded data packets such that the data packets can be sent in the OTN with the virtual lane-to-MAC module assignment preserved. In one example, a procedure, such as the Generic Mapping Procedure (GMP), is applied to the data streams and packets in each of the virtual lanes before they are transmitted in the OTN 130 such that the virtual lane-to-MAC module assignment is maintained and such that the destination optical endpoints can properly reassemble and reorder the packets upon receipt. In other words, the techniques described herein overcome the limitations of current OTN mapping standards (e.g., the ITU G.709 standard) which result in termination of the virtual lane-to-MAC module assignment information. In particular, G.709 contemplates only mapping of packets, therefore additional information such as, e.g., fields added by previous layers, are removed. In the case of a virtual lanes implementation, for instance, markers are added to data packets to allow deskewing and traffic routing and are essential to protocol operation. If such makers were mapped according to the standard G.709 method, those markers would be lost. In any event, virtual lane approaches and other possible variable rate PCS implementations are not contemplated by G.709. The techniques described herein present an alternate method to transcode and send virtual lane data packets oven an OTN.
Reference is now made to
At operation 306, a GMP is applied to the transcoded data packets of each virtual lane. For example, the virtual lanes may each have a constant bit rate (CBR) stream, and GMP mapping of the data in the virtual lanes enables the data of the virtual lanes to be incorporated or placed into an OTN-compatible container. The OTN-compatible container is referred to as a flexible Optical Data Unit (ODUFlex) container for virtual lanes (ODUFlex-VL). It should be appreciated that any OTN container in compliance with the Institute of Electrical and Electronic Engineering (IEEE) 802.3 standard may be used and that ODUFlex-VL is merely an example. At 308, the data in the virtual lanes are placed into the ODUFlex-VL containers. As such, the virtual lane-to-MAC module assignment information is preserved for each data stream as it is transmitted in the OTN 130. Additionally, the transcoded data packets of each virtual lane can be transmitted in the OTN 130 since they are embedded or incorporated into the ODUFlex-VL container, which is a data container capable of being transmitted in the OTN 130.
The ODUFlex-VL containers that pertain to the same MAC module (e.g., if there is more than one virtual lane that is mapped to a MAC module) can be aggregated using an enhanced scheme wherein some bytes of a data stream (e.g., bytes JC1/JC2/JC3, etc.) are used for GMP mapping and other bytes of the data stream (e.g., bytes JC4/JC5/JC6) are used to manage the concatenation of different virtual lanes. JC1-JC3 provide information to the receiver to identify the location of the stuffing bytes and correctly demap payload data, while JC4-JC6 are filled with a concatenation pointer described in G.709 chapter 18.1.2.2.2.
Additionally, this scheme may be used to aggregate data streams originating from different MAC modules that are assigned different virtual lanes. The scheme can also be used to add or drop a virtual lane from a single data flow.
In any case, after data is embedded or incorporated into the ODUFlex-VL container, the data for each virtual lane is sent in the OTN, as shown at 310 in
It should be appreciated that the OTN mapping operations may be separated between processing elements, and thus, the process described in
Reference is now made to
Reference is now made to
The network interface unit 502 is an interface that is configured to send and receive network traffic that is at a higher data rate that is subdivided into lower data rate traffic for PCS lane processing. The network interface unit 502 is coupled to the processor 504. The processor 504 may be a programmable processor, e.g., microprocessor, digital signal processor (DSP), or microcontroller or a fixed-logic processor such as an application specific integrated circuit (ASIC) or Field Programmable Gate Array (FPGA). As such, the processor 504 may represent plural processors within the optical node that perform general, programmable, and specific fixed logic operations, e.g., to perform PCS encoding and encryption. The processor 504 may comprise a processor with a combination of fixed logic and programmable logic, e.g., a System on a Chip (SoC), ASIC or FPGA with fixed logic, and a microprocessor and memory section.
The memory 506 may be of any type of tangible processor readable memory (e.g., random access, read-only, etc.) that is encoded with or stores instructions, such as virtual lane mapping software 150, e.g., for execution by processor 504. Thus, software or process 150 may be executed by software, firmware, fixed logic, or any combination thereof that cause the processor 504 to perform the functions described herein. Briefly, software 150 provides enables mapping of virtual lanes for data streams for transmission over an OTN. In general, software may be embodied in a processor readable medium that is encoded with instructions for execution by a processor that, when executed by the processor, are operable to cause the processor to perform the functions described herein.
It should be appreciated that the techniques described above in connection with all embodiments may be performed by one or more computer readable storage media that is encoded with software comprising computer executable instructions to perform the methods and steps described herein. For example, the operations performed by the nodes 110 and 120 may be performed by one or more computer or machine readable storage media (non-transitory) or device executed by a processor and comprising software, hardware or a combination of software and hardware to perform the techniques described herein.
In summary, a method is provided comprising: at an endpoint device in an optical transport network, distributing line encoded data blocks of a first data stream across a plurality of second data streams such that the second data streams can be processed at a lower data rate than a data rate associated with the first data stream; performing a transcoding operation on data packets of each of the second data streams to generate transcoded data packets; and processing the transcoded data packets such that the transcoded data packets of each of the second data streams can be sent over the optical transport network at the lower data rate.
In addition, a computer readable storage media is provided that is encoded with software comprising computer executable instructions and when the software is executed operable to: distribute at an endpoint device in an optical transport network line encoded data blocks of a first data stream across a plurality of second data streams such that the second data streams can be processed at a lower data rate than a data rate associated with the first data stream; perform a transcoding operation on data packets of each of the second data streams to generate transcoded data packets; and process the transcoded data packets such that the transcoded data packets of each of the second data streams can be sent over the optical transport network at the lower data rate.
Furthermore, an apparatus is provided comprising: a network interface unit; and a processor coupled to the network interface unit, and configured to: distribute at an endpoint device in an optical transport network line encoded data blocks of a first data stream across a plurality of second data streams such that the second data streams can be processed at a lower data rate than a data rate associated with the first data stream; perform a transcoding operation on data packets of each of the second data streams to generate transcoded data packets; and process the transcoded data packets such that the transcoded data packets of each of the second data streams can be sent over the optical transport network at the lower data rate.
The above description is intended by way of example only. Various modifications and structural changes may be made therein without departing from the scope of the concepts described herein and within the scope and range of equivalents of the claims.
