WO2007042342A1

WO2007042342A1 - Method for transferring data by means of ethernet frames and network element for processing ethernet frames

Info

Publication number: WO2007042342A1
Application number: PCT/EP2006/065567
Authority: WO
Inventors: Andreas Fricke
Original assignee: Nokia Siemens Networks Gmbh & Co. Kg
Priority date: 2005-10-13
Filing date: 2006-08-22
Publication date: 2007-04-19
Also published as: EP1938516A1; DE102005049104A1

Abstract

The invention relates to a method and to a network element for transferring data by means of ethernet frames, whereby OAM frames are at least partially transferred therebetween, from a first network element to a second network element. At least one first and one second transfer path are provided at least between both network elements. The data is transferred via at least the first transfer path. Alternating data of the KI-byte or the K2-byte of the SDH-Norm ITU-T G.841 is introduced into a byte of the OAM frames. A disturbance of the first transfer path is detected by one of the two network elements and the data is transferred via the second transfer path, which is signalised by means of the data of the KI-and K2-byte of the other network element.

Description

description

Method for transmitting data by means of Ethernet frame and network element for processing Ethernet frames

The invention relates to a method according to the preamble of patent claim 1 and a network element for processing Ethernet frames.

For the transmission of data the so-called Ethernet is often used. Ethernet is a frame-based or frame-based transmission technology for the transmission of data via a (communication) network. Ethernet includes a connectionless protocol for data transmission that is widely used because of its simplicity.

According to IEEE 802.3ah, so-called OAM frames or OAM frames are defined. These serve the so-called operation, administration and maintenance, ie the operation, the control, the administration and the maintenance of a (communication) network. A network consists of several network elements, which are connected to each other by connection paths. The network elements each generate and terminate Ethernet frames with which data is transmitted. OAM frames are each transmitted between different Ethernet frames with user data.

The object of the present invention is to improve the transmission of data by means of Ethernet frames.

This object is achieved by a method having the features of patent claim 1 and a network element having the features of patent claim 10.

According to the invention, it is proposed that data is transmitted via at least one transmission path, and that, in the event of a disturbance of this transmission path, a second undisturbed transmission path is used. The signaling of the fault or the switching is done by data that transmitted via OAM frame. Here, the information is exchanged using the Kl and K2 byte functionality according to the SDH standard ITU-T G.841. For this purpose, the Kl or the K2 byte is alternately transmitted in one byte of the OAM frame. The meaning, coding, functionality and use of these K-bytes in the network elements for the processing of Ethernet frames or Ethernet frames is identical to the SDH standard. Thus, the data transmission is protected by Ethernet frame between two network elements by the use of the Kl- / K2-byte protocol according to if at least two at least partially independent transmission paths are given. This has the advantage that there is a fast equivalent circuit in case of failure or failure of a connection path or E-thernet segment for the data transmission. The switchover takes place very fast SDH-typical and can be in the micro-second range. This leads to an increase in the attractiveness of Ethernet for data transmission.

Advantageous embodiments of the invention are specified in the dependent claims and in the exemplary embodiment.

An embodiment of the invention will be explained in more detail below with reference to the drawing. Showing:

Figure 1 is a circuit diagram for explaining the invention.

Figure 1 shows a section of a circuit diagram for a network element, with a first Ubertragungsweg respectively a working line WLl, which is connected to a first Ethernet Phy component respectively Ethernet physical layer module ETH Phyl. In an analogous manner, further transmission paths / working line WL2,..., WLN are each connected to an Ethernet Phy component ETH Phy2,..., ETH PhyN. Furthermore, a Ersatzubertragungsweg respectively Protection Line WLP is provided, which is connected to an Ethernet Phy module ETH PhyP. The Ethernet Phy modules ETH Phyl, ..., ETH PhyN, ETH PhyP are each connected to a switching device SE. This is on the other hand, each with an Ethernet MAC module or Ethernet media access control module ETH MACl, ..., ETH MACN, ETH MACP connected, wherein in each case an Ethernet Phy device is connected by the switching device SE with an Ethernet MAC module. In the example the first Ethernet Phy module ETH Phyl with the first Ethernet MAC module ETH MACl, ETH Phy2 with ETH MAC2 etc.

That An Ethernet frame that comes from a working line is forwarded to the Ethernet MAC block via the Ethernet Phy block and the switching device SE. This applies analogously to the Ethernet frame of the Protection Line. In the same way, OAM frames are transmitted to the Ethernet MAC module.

The OAM frames are generated, inserted, processed and terminated by the Ethernet MAC module.

Such a first network element is connected to at least two connection paths with a second such network element.

According to the invention, a protocol analogous to the protocol of the K and K2 bytes of the SDH standard ITU-T G.841 is used in one byte of the OAM frame. For example, the previously unused bits 8 to 15 of the OAM frame are used for this purpose. Since these bits are only one byte, but two bytes - Kl and K2 - are needed, the Kl byte and then the K2 byte are transmitted first in two consecutive OAM frames or vice versa. In addition, in the previously unused bit 7 of the OAM frame, an identifier can be transmitted which identifies the type of the K byte. For example, "0" for the Kl byte and "1" for the K2 byte or vice versa.

The insertion and termination as well as the processing of the K1 and K2 bytes can be carried out by means of the Ethernet MAC module. This can have a K-byte processing and transfer function, which can also be implemented as a separate component. In Figure 1, this is as K-

Byte processing device KV, which controls the switching device SE.

Alternatively, the OAM frames may be processed by the Ethernet Phy device such that the K and K2 bytes By means of this module are used and filtered out, the Kl and K2 bytes are passed to a K-byte processing and transfer function, which can be at least partially part of the Ethernet Phy block, so that the Ethernet Phy block by default, ie the Kl and K2 Bytes not included OAM frames are passed to the Ethernet MAC block, so that the Ethernet MAC blocks need no adaptation.

If a transmission path / a working line has a fault, this is detected by a network element. Corresponding information K1 / K2 encoded by the Ethernet Phy block or the Ethernet MAC block is inserted in the OAM frame. This OAM frame is transmitted to the adjacent (destination) network element. There, the K1 / K2 byte from the OAM frame is terminated and evaluated. Subsequently, a switchover from the faulty working line to the protection line in both network elements takes place in accordance with the Kl / K2-byte protocol of the SDH standard. In the respective network element, a switching command is sent to the switching device SE by the K-byte processing and transfer function, so that it switches from the faulty or failed working line to the protection line / spare transmission path. Any data traffic of the Protection-Line is rejected.

In FIG. 1, the K bytes are inserted in the Ethernet MAC modules. A K-byte processing and transfer function KV is designed as an independent module which is connected to the respective Ethernet MAC modules ETH MAC1, ETH MAC2,..., ETH MACN, ETH MACP and the switching device SE.

According to the invention, the information of the Kl and K2 bytes are transmitted in an OAM frame whose meaning, coding, functionality and use is identical to the SDH standard, as described in ITU-T G.841. Thus, for example, unidirectional protection, bidirectional protection, 1: N protection or ring protection can be switched. These modified OAM frames are used in the Ethernet Phy Viewpoint in the Ethernet physical layer interface or in the Ethernet MAC block is generated or terminated and, if necessary, processed.

A case of failure can be detected or triggered by

- Forced switching to the protection path

Signaling from the far side by the K byte

Protocol (Kl, K2)

a loss-of-bit synchronization of the physical layer interfaces z. Eg no signal

a loss-of-byte synchronization of the physical layer

interfaces

- a link-down message

a rate of erroneous OAM (Operation Administration Maintenance Praamble) detected by checking the OAM CRC, that is the check sum of the OAM frames through the physical layer interface function

by physical layer link quality supervision, i. H. if the signal quality is not sufficient, is reduced to a lower link speed z. From 1 Gbit per

Second switched to 100 MBit per second, but a spare link used

- if an autonegotiation went wrong

if the rate of faulty Ethernet frames exceeds a threshold, by checking the MAC check sum

CRC, which can be realized in the MAC function.

In the event of an error, the network element recognizing the error signals with the aid of the K-byte information transmitted in the OAM frame to the opposite network element which is switched to the protection link / spare transmission path or a second / further transmission path. As a result, both devices switch over to the replacement transmission path / the protection line at the end of the faulty connection or the defective link. This is shown in dashed lines in FIG

Switch shown, wherein the switch of the Protection Line occupies the dashed line position and the switch of the disturbed working line / the first transmission path also the dashed line marked position occupies. This means that all traffic is transmitted bidirectionally via the Protection Line. Since the changeover takes place before the MAC block, all Ethernet frames or Ethernet frames destroyed by the switching process are filtered out and paid. The actual performance including all switching operations can be monitored.

In order to achieve switching times that are comparable to the SDH standard or SONET standard, which is usually less than 50 ms, it must be ensured that at least one K / K2 byte combination, ie two OAM frames, are transmitted per unit of time. Since OAM frames are transmitted between two "normal" Ethernet frames, no K-byte protocol can be transmitted during the transmission of the "normal" Ethernet frames. With Ethernet at 10 MB / s, this can result in interruptions of 1 ms. Therefore, the method is preferably suitable for Ethernet at 100 MB / s or faster, at least when switching times according to the SDH standard are to be achieved.

The following table shows the duration of an Ethernet frame for Ethernet data rates from 10 Mb / s to 10 Gb / s and frame lengths of 1600 bytes and 9600 bytes (jumbo frame).

By comparison, SDH frames have a duration of 125 μs. A 10 Mb / s Ethernet transmission could thus not achieve the switching times according to the SDH standard.

A persistence check should only pass K byte changes after three consecutively changed K bytes. For this, 6 OAM frames are needed. A defect that is signaled via a K-byte protocol can therefore be at 100 Mb / s or higher transmission rate can be detected after 600 μs. This detection time is comparable to the SDH method. If no OAM frame has been transmitted for 100 μs, an OAM frame must be used and transmitted. If the OAM frame rate is lowered, the response time of the protocol becomes longer. Switching a spare connection within 50 ms, however, seems realistic even at a much smaller OAM frame rate. The IEEE 802.3ah standard proposes an OAM frame rate of 10 OAM frames per second. The detection of an error using the K-byte protocol would take 200 ms. In order to achieve switching times in the area of the SDH protection methods, the OAM frame rate must be significantly increased in accordance with the IEEE 802.3ah standard.

In summary, a method for protecting Ethernet transmission paths using protection circuit functions in accordance with the SDH standard results. It provides higher security of Ethernet connections. This makes it possible to achieve a higher acceptance and attractiveness of Ethernet.

Claims

claims

1. A method for transmitting data by means of Ethernet frames, wherein at least partially OAM frames are transmitted between them, from a first network element to a second network element, at least partially providing at least a first and a second transmission path between the two network elements, characterized in that the data are transmitted via at least the first transmission path, that in one byte of the OAM frame alternately data of the K byte or of the K2 byte of the SDH standard ITU-T G.841 be inserted, that a fault of the first transmission path is detected by one of the two network elements and the data is transmitted via the second Ubertragungsweg, wherein this is signaled to the other network element by means of the data of the Kl and K2 bytes.

2. The method according to claim 1, characterized in that OAM frames are transmitted in accordance with the IEEE 802.3ah standard.

3. The method of claim 1 or 2, characterized in that the data of the Kl and K2 bytes are inserted in an Ethernet MAC module or in an Ethernet Phy module in the OAM frame.

4. The method according to any one of the preceding claims, characterized in that the data of the Kl and K2 bytes are evaluated or terminated in an Ethernet MAC module or in an Ethernet Phy block.

5. The method according to any one of the preceding claims, characterized in that a changeover from the first to the second transmission path by means of a switching device is performed, which is arranged between an Ethernet Phy and an Ethernet MAC module.

6. The method according to any one of the preceding claims, characterized in that the OAM frames are cyclically generated and transmitted.

7. The method according to any one of the preceding claims, characterized in that a changed K-byte is passed or evaluated only after receiving three times this changed K-byte.

8. The method according to any one of the preceding claims, characterized in that in the flag field of the OAM frame in the bits 8 to 15, the data of the Kl or K2 bytes are transmitted.

9. The method according to claim 8, characterized in that in the bit 7, a logical zero a Kl byte and a logical one see a K2 byte or vice versa.

10. Network element for transmitting data by means of Ethernet frames, comprising means for carrying out the method according to one of the preceding claims.

11. Network element according to claim 10, characterized in that in each case one connection path is connected to an Ethernet module which has at least one Ethernet Phy and one Ethernet MAC module, a switching device being arranged between them which is controllable in such a way is switched to at least one remaining connection path in case of failure of a connection path, and the that it can use a protocol according to the Kl and K2 bytes of the SDH standard ITU-T G.841.