Patent Application
20130107897
The present invention pertains to the domain of communication networks, and more particularly the transmission of information carried by Ethernet Synchronization Messaging Channel (ESMC) messages through Synchronous Optical Networking/Synchronous Digital Hierarchy (SONET/SDH) domains.
This is because the SDH/SONET and Synchronous Ethernet (SyncE) domains are compatible from the standpoint of physically distributing a Synchronization frequency as depicted in
In SONET/SDH domains, the synchronization signal's quality level (or QL) is carried within the physical layer, in the header of SONET/SDH frames.
In SyncE domains, meanwhile, the synchronization status is carried by ESMC messages (or packets) that contain Type Length Value (TLV) structures as specified in the 802.3 protocol by the Institute of Electrical and Electronic Engineers (IEEE 802.3)). At present, only one of these TLV structures is standardised by the International Telecommunications Union (ITU-T). This is the TLV field indicating the synchronization signal's quality level (ordinarily designated by QL-TLV) in order to maintain compatibility with SONET/SDH.
Proposals to add TLV structures have, however, been made within UIT-T in order to optimise the use of those ESMC messages. These additional TLVs make it possible to carry other information that is helpful for managing synchronization.
In the configuration described in
The need is therefore to propose a method that would make it possible to transmit data related to additional TLV structures with respect to QL-TLV 9 through SDH/SONET domains 3.
Thus, the present invention pertains to a method for transmitting an Ethernet Synchronization Messaging Channel “ESMC” message between a first and a second Synchronous Ethernet “SyncE” domain, said first and second domains being interconnected by a third, Synchronous Optical Networking or Synchronous Digital Hierarchy “SONET/SDH” domain, in which at least one part of said Ethernet Synchronization Messaging Channel “ESMC” message is encapsulated when entering said third domain and unencapsulated when exiting said third domain, so as to create a network tunnel through that third Synchronous Optical Networking/Synchronous Digital Hierarchy “SONET/SDH” domain.
According to another aspect of the present invention, said method comprises at least one Type Length Value “TLV” field different from the Quality Level “QL-TLV” field.
According to an additional aspect of the present invention, the encapsulation and unencapsulation of the messages is done in the Synchronous Ethernet-Synchronous Optical Networking/Synchronous Digital Hierarchy “SyncE-SDH/SONET” hybrid nodes located at the interface of the various domains.
According to an additional aspect of the present invention, a Synchronous Ethernet-Synchronous Optical Networking/Synchronous Digital Hierarchy “SyncE-SDH/SONET” hybrid node receives
firstly, at least two distinct synchronization signals that have taken different routes and that come from different source border hybrid nodes, and,
secondly, at least two different Ethernet Synchronization Messaging Channel “ESMC” messages corresponding to said at least two synchronization signals, and coming from different tunnels,
wherein said at least two messages comprising an additional Type Length Value “TLV” field that makes it possible to tell different Ethernet Synchronization Messaging Channel “ESMC” messages apart.
According to another aspect of the present invention, a Synchronous Optical Networking/Synchronous Digital Hierarchy “SONET/SDH” node receives at least two different synchronization signals that have taken different routes and that come from different source border hybrid nodes,
selects the primary synchronization signal to distribute, based on a list of priorities provided by a synchronization management system.
and wherein, in the event that the primary synchronization signal degrades and the primary synchronization signal is reselected, a message, comprising an identification of the new selected primary synchronization signal, is transmitted to the synchronization management system. Said synchronization management system then transmitting, to the destination Synchronous Ethernet-Synchronous Optical Networking/Synchronous Digital Hierarchy “SyncE-SONET/SDH” hybrid node, an identification of the synchronization source corresponding to the selected synchronization signal in order to allow the destination border hybrid node to consider the tunnel encapsulating the Ethernet Synchronization Messaging Channel “ESMC” message associated with the selected primary synchronization signal.
According to an additional aspect of the present invention, the additional, at least one, Type Length Value “TLV” field indicates the stability level of the frequency provided by the frequency source.
According to an additional aspect of the present invention, at least one additional Type Length Value “TLV” field indicates the number of nodes traversed by said message since its source node.
According to an additional aspect of the present invention, the additional, at least one, Type Length Value “TLV” field comprises an identification of the nodes traversed by said message.
According to an additional aspect of the present invention, the tunnel associated with the Ethernet Synchronization Messaging Channel “ESMC” message of the Synchronous Optical Networking/Synchronous Digital Hierarchy “SONET/SDH” domain follows the same route as the synchronization signal.
According to an additional aspect of the present invention, the tunnel associated with the Ethernet Synchronization Messaging Channel “ESMC” message of the Synchronous Optical Networking/Synchronous Digital Hierarchy “SONET/SDH” domain follows a different route from the synchronization signal.
The present invention also pertains to a Synchronous Ethernet-Synchronous Optical Networking/Synchronous Digital Hierarchy “SyncE-SDH/SONET” hybrid node comprising means for encapsulating an Ethernet Synchronization Messaging Channel “ESMC” message that comprises at least one Type Length Value “TLV” field different from the Quality Level field, known as “QL-TLV”.
The present invention also pertains to a Synchronous Ethernet-Synchronous Optical Networking/Synchronous Digital Hierarchy “SyncE-SONET/SDH” hybrid node comprising
The present invention also pertains to a Synchronous Optical Networking/Synchronous Digital Hierarchy “SONET/SDH” node comprising
The present invention also pertains to a synchronization management system comprising
Other characteristics and benefits of the invention will become apparent from the following description, given with reference to the attached drawings, which by way of a non-limiting example depict one possible embodiment.
In these drawings:
In the following description, generally:
The term “ESMC” stands for Ethernet Synchronization Messaging Channel; The term “SONET” stands for Synchronous Optical Networking;
The term “SDH” stands for Synchronous Digital Hierarchy;
The term “TLV” stands for Type Length Value;
The term “QL” Quality Level;
The term “SyncE” stands for Synchronous Ethernet;
The term “encapsulation” refers to encapsulation with respect to packets, in which the packet is enclosed within a protocol structure (comprising a header, checksum, etc.) so as to allow it to be transmitted into another domain managed by a different protocol; the term “unencapsulation” refers to the reverse operation, the outcome of which is the initial packet.
The embodiments of the present invention refer to the transmission of ESMC messages within a tunnel connecting two SyncE domains through a SDH/SONET domain. As depicted in
Furthermore, it should be noted that because the network tunnel 19 associated with the ESMC messages transparently traverses the SDH/SONET nodes S, the path taken by that tunnel is not connected to the path taken by the synchronization signals 11. Nonetheless, it is recommended that the paths taken be the same, whenever possible, in order to allow more effective protection in the event that the synchronization path is reconfigured owing, for example, to a degradation in the primary signal.
The information on the quality level (QL) is normally transmitted via the SONET/SDH header, but it may additionally be encapsulated with the other TLV structures and transmitted on the packet level through the tunnel associated with the previously described ESMC message. If that happens, the QL value extracted from the physical level of the SDH/SONET domain may be compared to the encapsulated QL value, and if there is any inconsistency between the two QL values, the encapsulated value is then ignored by the destination border hybrid node 15 and an alarm is sent to the synchronization management system, in order to report such an inconsistency.
The setting up of tunnels 19 as described by
This way, according to one embodiment of the present invention, one of the additional TLV fields 9 is a field that makes it possible to tell apart two ESMC tunnels 19. This field may, for example, be a “source ID TLV” TLV field comprising an identification of the source border hybrid node of the ESMC tunnel 13 or a “tunnel ID TLV” field comprising an identification of the tunnel 19 or a “trace route” field comprising an identification of all of the nodes crossed by the ESMC message 17, or a combination of those three fields. For the “source ID TLV” and “tunnel ID TLV” fields, said fields are deleted from the destination border hybrid node 15.
Another configuration presented in
However, in the event of degradation (of the QL level) or if the primary synchronization signal fails, the re-selection of a new synchronization source is carried out locally within the node S1: by comparing the “QL-TLV” quality level values contained within the SONET/SDH frame, for example. But in such a case, the destination border hybrid node 15 cannot know the onset or result of that selection, which would allow it to associate the physical synchronization path with the relative ESMC information transported on the packet level, through a network tunnel
In order to announce to the destination border hybrid node 15, the identity of the primary synchronization signal's source that is transmitted to it in the event of a re-selection, according to one embodiment of the present invention, a re-selection message (e.g. an alarm) is sent by the node S1 to the synchronization management system in order to inform that system of the physical port connected to the new primary synchronization signal 11, which will be transmitted to the destination border hybrid node 15. The synchronization management system is thereafter responsible for making the connection between the information on the port of the new primary signal thereby selected within the node S1 and the identity of the source border hybrid node associated with the new synchronization signal thereby selected by S1; this can be done, for example, by cooperating with the SONET/SDH network management system.
In general, the selection of synchronization sources within the node S1 is carried out automatically, within the software and not within the hardware. Consequently, it is fairly easy to update the software in order to add instructions such as sending an alarm to the synchronization management system.
When it starts up, the synchronization management system 21 sends the node S1 a configuration message 26 comprising, for example, a priority list in order to locally control the synchronization signal selection process from among the synchronization signals received at the physical ports 22 and 23. The primary synchronization signal serves to lock the local clock of the equipment S1. The present scenario assumes that the primary synchronization signal initially selected by the node S1 is provided by the port 22.
If there is degradation in the quality level or that primary signal fails, the node S1 re-selects the primary signal based on the quality level of the received signals and on the priority list. In
This method therefore enables the destination border hybrid node to associate the associated tunnel with the ESMC message to the source of the selected primary signal.
It should also be noted that the embodiments presented above for two physical synchronization distribution paths may be extended to more than two distribution paths from different (synchronization) sources, and the presented selection modes may be applied to any number of synchronization frequency distribution paths.
Thus, the embodiments of the present invention make it possible to transmit ESMC messages 17 comprising additional TLV fields 7 between two SyncE domains 1 interconnected by a SDH/SONET domain 3 while avoiding the filtering of the information carried by those additional fields 7 at the interface between the domains and allowing the destination border hybrid node 15 to associate the ESMC messages 17 received with the received primary synchronization signal 11 and therefore to use those messages consistently with the primary synchronization physical signal.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1002753 | Jun 2010 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/061025 | 6/30/2011 | WO | 00 | 1/17/2013 |
