CN113922869A - EPON protection switching fast ranging system - Google Patents

EPON protection switching fast ranging system Download PDF

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CN113922869A
CN113922869A CN202111183736.3A CN202111183736A CN113922869A CN 113922869 A CN113922869 A CN 113922869A CN 202111183736 A CN202111183736 A CN 202111183736A CN 113922869 A CN113922869 A CN 113922869A
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pon port
rtt
message
olt pon
onu
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CN113922869B (en
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龙光平
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Xinhe Semiconductor Technology Wuxi Co Ltd
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Xinhe Semiconductor Technology Wuxi Co Ltd
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/03Arrangements for fault recovery
    • H04B10/032Arrangements for fault recovery using working and protection systems
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/03Arrangements for fault recovery
    • H04B10/038Arrangements for fault recovery using bypasses
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062Network aspects
    • H04Q11/0067Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062Network aspects
    • H04Q2011/0079Operation or maintenance aspects
    • H04Q2011/0081Fault tolerance; Redundancy; Recovery; Reconfigurability
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00Reducing energy consumption in communication networks

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)

Abstract

The invention relates to the technical field of EPON (Ethernet passive optical network), in particular to a system for protecting, switching and rapidly ranging an EPON (Ethernet passive optical network), which comprises a main OLT PON port, a standby OLT PON port, an ODN (optical distribution network) and N ONUs (optical network units), wherein the main OLT PON port and the N ONUs complete registration and activation and carry out interaction on network services, the standby OLT PON port synchronizes the service configuration of the main OLT PON port in real time, the standby OLT PON port can rapidly complete ranging calculation of all the ONUs by sending a special Discover message, and then the message of the ONUs can be received according to a specified time slot by using new RTT (round trip time) information. The invention can reduce the service interruption time of switching, improve the user experience and improve the system stability under the condition that the number of the ONUs and the backbone distance dynamically change.

Description

EPON protection switching fast ranging system
Technical Field
The invention relates to the technical field of EPON networks, in particular to a system for protecting, switching and rapidly ranging an EPON network.
Background
With the development of Network technology, the demand of users for transmitting a large amount of services such as voice, data and video by using a Network is continuously increased, and Passive Optical Networks (PONs) are produced accordingly;
the topology structure of the PON system is shown in fig. 2, and the PON system generally comprises an OLT (Optical Line Terminal), an ODN (Optical Distribution Network), and an ONU (Optical Network Unit), and adopts a P2MP (Point to More Point, Point to multipoint) Network structure; in the TDM PON system, the data transmission of an EPON (Ethernet Passive Optical Network) system in the downlink direction (from an OLT to ONUs) adopts a broadcasting mode, each ONU receives all data frames and then acquires the data frame according to the Logical Link Identification (LLID) information of the ONU per se;
the PON technology can be subdivided into multiple types, and mainly the differences between the data link layer and the physical layer are distinguished, and APON, EPON, GPON, and the like are commonly used.
The whole registration activation process of EPON is shown in fig. 3:
1. the OLT broadcasts and issues a Discovery message with the structure shown in FIG. 4, and a local Timestamp T is marked in a Timestamp field of the message0
2. After receiving Discovery message, ONU updates timestamp T in message0To the local; after a certain random time delay TrandomThen, a Register _ req message with the structure shown in fig. 6 is fed back, and the Timestamp field in the message is filled with the Timestamp T of the ONU local1
3. OLT is in local T2Constantly receiving Register _ req message of ONU and extracting timestamp T in message1The loop delay rtt (roundtrip time) is calculated according to the method shown in fig. 72-T1Thus, the loop time of the ONU is obtained;
4. the OLT issues a Register message and follows a Gate2 bandwidth to the ONU; at this time, the Gate2 bandwidth is to allocate an uplink sending time slot according to the obtained RTT information, so that the ONU message can reach the OLT without being affected by other ONU data;
5. the ONU feeds back a Register _ ack message after receiving the Register and Gate2 messages;
6. after receiving the Register _ ack message fed back by the ONU, the OLT completes registration and activation;
7. the OLT intermittently transmits a Normal _ gate message to the ONU;
8. the ONU receives the Normal _ gate message, transmits a service data message according to the bandwidth of the message and feeds back a Report message;
9. the OLT receives the Report message of the ONU, extracts a timestamp in the message to calculate new RTT information, compares the new RTT information with the previous RTT information, and updates the RTT information if the difference value is within a reasonable range required by a standard; the RTT information is the ranging information, and the service interaction process is completed at the moment;
in the deployment application of the passive optical network, some users need higher security, and it is hoped that an operator can provide a guarantee mechanism to ensure that the service path is not interrupted, or the next level of requirement is that the operator can recover quickly after the service path is interrupted. The requirements of a protection path and a fast switching path are provided for the passive optical network carrying the operation of the user service;
fig. 5 illustrates a typical network architecture diagram in an EPON network protection mode;
when the OLT has a Network failure and is abnormal, the service needs to be quickly switched from a main working PON (Passive Optical Network ) port to a backup PON port, in the process, the EPON service will undergo a process from interruption to restoration, and the time consumed by the process is called protection switching time; the protection switching of the OLT needs to re-measure the distance of the ONU under the EPON port, so that the time slot conflict can not exist when the service of each ONU reaches the OLT, and the time for re-measuring the distance also determines the time for protection switching;
there are two common techniques available:
firstly, after a network fault occurs at a main PON port, switching to a standby PON port, then ranging all ONU again, and then recovering the service;
secondly, generally, before ONU layout, a main PON port and a standby PON port both perform ranging on the ONUs under the PON in advance and store ranging values in the local, and when a network fault occurs at the main PON port, the main PON port is directly switched to the standby PON port without performing ranging again;
the technical method of the first method is limited in that: the distance measurement needs to be carried out again, the consumed time is at least more than 100 milliseconds, the service interruption time is too long, and the user experience is influenced;
the technical limitation of the second method is that: the whole main and standby PON port network can not change in the using process, if a newly-added ONU user event occurs or the trunk optical fiber distance of the standby PON port changes, the standby OLT PON port needs to update RTT information of all ONUs under the ODN in time, the current main PON port network service needs to be stopped, the standby PON port is switched to carry out ranging again, ranging information is recorded, and then the main PON port network is switched back; if the replacement is not updated in time and once the switching is started, if the main and standby optical fibers have a distance difference or an ONU is newly added, the ONU data under the PON port of the standby OLT misses a sending time slot allocated to the ONU by the OLT, so that the uplink service of the whole system is seriously lost; the protection switching can be two different OLT PON ports on the same OLT line card, or two different OLT PON ports on different line cards, so the uncertainty of the system environment is very common, and once such a situation occurs, the hidden trouble of service interruption is easily caused, and the maintenance is very inconvenient.
Disclosure of Invention
The invention provides a system for protecting, switching and rapidly ranging an EPON (Ethernet passive optical network), which can reduce the service interruption time of switching, improve the user experience and improve the system stability under the condition that the number of ONUs and the backbone distance are dynamically changed.
In order to realize the aim of the invention, the EPON network protection switching rapid ranging system comprises a main OLT PON port, a standby OLT PON port, an ODN and N ONUs, wherein the main OLT PON port and the N ONUs complete registration activation and perform interaction of network services, the standby OLT PON port synchronizes service configuration of the main OLT PON port in real time, and a sending end of the standby OLT PON port is closed; when the protection switching is started, a sending end of a standby OLT PON port is opened, a Discovery2 message is sent to the ONU of the corresponding LLID, and the ONU of the corresponding LLID feeds back a Report message; the standby OLT PON port receives the Report message, extracts the timestamp information in the Report message and calculates the new loop delay time RTTnewAccording to the new loop delay time RTTnewWith old loop delay time RTToldDetermines the final RTT information.
As an optimization scheme of the invention, the ODN is a 2: N optical splitter, wherein N is the number of the ONU.
As an optimization scheme of the invention, a force _ report is set to 1 and a Discovery flag is set to 0 in a flag field of a Discovery2 message; and the ONU with the corresponding LLID receives the Discovery2 message, analyzes the message and sends a Report message.
As an optimization of the invention, a new loop delay time RTTnewWith old loop delay time RTToldComparing and calculating a difference RTTdelta
1) If RTT is presentnew≥RTToldIt is noted that the trunk optical fiber distance of the standby OLT PON port is greater than or equal to the trunk optical fiber distance of the main OLT PON port, and at this time, RTT information of all ONUs stored in the standby OLT PON port needs to be read out one by one, and this difference RTT is addeddeltaAs final RTT information;
2) if RTT is presentnew<RTToldWhen the trunk optical fiber distance of the standby OLT PON port is less than the trunk optical fiber distance of the main OLT PON port, RTT information of all ONUs stored in the standby OLT PON port needs to be read out one by one, and the difference RTT is subtracteddeltaAs final RTT information.
The invention has the positive effects that: the invention can complete the switching from the main OLT PON port to the standby OLT PON port within 5 milliseconds, and can accept the dynamic change of the ONU number and the inconsistent distance between the main optical fiber and the standby optical fiber before the switching; compared with the two existing implementation modes, the method saves the time of protection switching, improves the stability of the system, is convenient to maintain, can be quickly recovered after the service access is interrupted, and improves the network experience of users.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a data structure of Discovery2 message according to the present invention;
FIG. 2 is a schematic of a topology of a PON system;
fig. 3 is a schematic diagram of an ONU registration activation flow for an EPON;
FIG. 4 is a diagram of a standard Discovery message data structure;
fig. 5 is a schematic diagram of a typical network architecture in the PON network protection mode;
FIG. 6 is a diagram of a Register _ req message data structure;
fig. 7 is a schematic diagram of RTT calculation.
Detailed Description
The implementation of the invention is described in further detail below with reference to the attached drawing figures:
the invention discloses a system for protecting, switching and rapidly ranging an EPON (Ethernet passive optical network), which comprises a main OLT (optical line terminal) PON port, a standby OLT PON port, an ODN (optical distribution network) and N ONUs (optical network units), wherein the main OLT PON port and the N ONUs finish registration activation and carry out interaction of network services, the standby OLT PON port synchronizes the service configuration of the main OLT PON port in real time, and a sending end of the standby OLT PON port is closed; when the protection switching is started, a sending end of a standby OLT PON port is opened, a Discovery2 message is sent to the ONU of the corresponding LLID, and the ONU of the corresponding LLID feeds back a Report message; the standby OLT PON port receives the Report message, extracts the timestamp information in the Report message and calculates the new loop delay time RTTnewAccording to the new loop delay time RTTnewWith old loop delay time RTToldDetermines the final RTT information.
Discovery2 is a special message, is a modification of the standard Discovery message structure, is not in the standard specification, but the ONU on the market can identify:
for an initiator (a standby OLT PON port), an OLT designer makes a receiving side of an OLT think that it is a normal Discovery message; therefore, the OLT may open a Discovery window enough to cover the farthest logical distance that the PON can support at the receiving side according to the processing flow of Discovery messages; therefore, no matter how much the optical fiber distance of the ONU is changed after the main/standby switching, the OLT can receive an effective message fed back by the ONU in a discovery window time slot;
for the ONU under the OLT PON port, the Discovery flag of the special message is set to be 0, the Force _ Report flag is set to be 1, the ONU can be identified to be a normalGate message according to the standard rule, and the ONU must feed back a Report message carrying timestamp information to the OLT according to the standard rule.
Wherein: the main OLT PON port and the standby OLT PON port are connected with the ONUs through a 2: N optical splitter, and N is the maximum number of the ONUs.
The main OLT PON port completes registration and activation of the ONU and performs interaction of network services through the flow shown in fig. 3; the process is specifically implemented as follows:
1) the OLT issues the Discovery message with the structure shown in fig. 4 in a broadcast manner, and a local Timestamp T is marked in the Timestamp field of the message0And filling the upper limit value T of random time delay in the Grant field of the messagemax_random(i.e., ONU generated random time delay T)randomThe value cannot be exceeded), the purpose of the random time delay is to prevent the data sent by the ONU at the OLT PON port for the first time from time slot collision as far as possible; meanwhile, the OLT may open a discovery window as shown in the right side of fig. 3 on the receiving side, where the window length is Tmax_random+Tlogic_distance,Tlogic_distanceA common default value is 20KM, which is converted into a time unit of about 200 us; therefore, data sent by ONUs within an optical fiber distance of 20KM below the PON port all reach the OLT within the range of the discovery window, and then the data can be analyzed;
2) after receiving Discovery message, ONU updates timestamp T in message0To the local; after a certain random time delay TrandomThen, a Register _ req message with the structure shown in fig. 6 is fed back, and the Timestamp field in the message is filled with the Timestamp T of the ONU local1
3) OLT is in local T2Constantly receiving Register _ req message of ONU and extracting timestamp T in message1Calculating the delay RTT (RoundTrip time) of the loop as T2-T1Thus, the loop time of the ONU is obtained, and fig. 7 is a schematic diagram of RTT calculation;
4) the OLT issues a Register message and generates a Gate2 bandwidth to the ONU according to the RTT information;
5) after receiving the Register and Gate2 messages, the ONU sends a Register _ ack message to the OLT according to the specified uplink sending time slot in the Gate 2;
6) after receiving the Register _ ack message fed back by the ONU, the OLT completes registration and activation;
7) the OLT intermittently transmits a Normal _ gate message to the ONU;
8) the ONU receives the Normal _ gate message, transmits a service data message according to the bandwidth of the message and feeds back a Report message;
9) the OLT receives the Report message of the ONU, extracts a timestamp in the message to calculate new RTT information, compares the new RTT information with the previous RTT information, and updates the RTT information if the difference value is within a reasonable range required by a standard; RTT is the information of the distance measurement, and the service interaction process is finished at the moment;
after the registration and activation of all ONUs are completed, the standby OLT PON port synchronizes the service configuration of the main OLT PON port in real time, including RTT information values of all ONUs below the main OLT PON port, but the transmitting end is closed.
When a main OLT PON port fails (usually, a receiving side of the main OLT PON port cannot receive an optical signal sent by an upstream ONU within a certain time), a transmitting end of the main OLT PON port needs to be immediately closed, and a transmitting end of a standby OLT PON port needs to be opened; because the PON port of the main OLT is closed in a downstream mode, the ONU of the EPON system enters a Hold _ Over state at the moment, and the time T staying in the Hold _ Over stateholdThe main OLT PON port sends the information to the ONU when registering and activating; the OLT needs to complete the switching process from the main OLT PON port to the standby OLT PON port within the time; if the distances between the main optical fiber of the main OLT PON port and the main optical fiber of the standby OLT PON port are inconsistent, the OLT needs to finish an important thing in the process of re-ranging all the ONUs connected with the ODN, and the time consumed by the ranging is TholdThe minimum time of (c).
In order to prevent events such as an excessive change of a trunk fiber distance of a standby OLT PON port or an addition of a new ONU under ODN connection from occurring before starting protection switching, the technical solution provided by the present invention issues a special Discovery message as shown in fig. 1, that is, a Discovery2 message, when the standby OLT PON port is opened. Discovery2 message flag field for force _ report 1, Discovery flagSetting a mark 0; the message is issued to the ONU through the unicast LLID, and only the ONU with the corresponding LLID can analyze and respond, so that a certain ONU in the Hold _ Over state can respond and feed back a Report message. For the standby OLT PON port, the message is a Discovery message, so a Discovery window that can cover the farthest logical distance is opened to receive the message, so that even if the distance of the trunk fiber of the standby OLT PON port is greatly different from that of the main OLT PON port, the standby OLT PON port can receive the message; after receiving the Report message sent by a specific ONU, the standby OLT PON port can extract the timestamp information in the message and calculate a new RTTnewThen the time difference is related to the old loop delay time RTT of the ONU under the main OLT PON portoldComparing and calculating a difference RTTdelta
1) If RTT is presentnew≥RTToldIt is noted that the trunk optical fiber distance of the standby OLT PON port is greater than or equal to the trunk optical fiber distance of the main OLT PON port, and at this time, RTT information of all ONUs stored in the standby OLT PON port needs to be read out one by one, and this difference RTT is addeddeltaAs final RTT information;
2) if RTT is presentnew<RTToldWhen the trunk optical fiber distance of the standby OLT PON port is less than the trunk optical fiber distance of the main OLT PON port, RTT information of all ONUs stored in the standby OLT PON port needs to be read out one by one, and the difference RTT is subtracteddeltaAs final RTT information.
The purpose of design is to let the OLT consider the message as a Discovery message; but let the ONU consider that this is not a Discovery message, but a NormalGate message; the NormalGate message is of unicast attribute and only belongs to an individual ONU; the Discovery message is broadcast, and the ONU in the Hold _ Over state does not respond to the Discovery broadcast message;
because the distance between the ONUs after the main/standby switching is greatly changed, the transmission delay of the message is also changed; the OLT further uses a normal normalGate message to communicate with the ONU, and the OLT cannot receive a message fed back by the ONU in a specified allocated time slot; if the OLT side processes according to the Discovery message, a large time slot Discovery window is opened, and the OLT can receive the Discovery message no matter how much the ONU distance changes.
In order to accurately calculate RTTdeltaSeveral measurements may be made to average. Therefore, the standby OLT PON port can quickly finish the ranging calculation of all the ONUs, and then the message of the ONU can be received according to the specified time slot by using the new RTT information, the part of functions is finished by chip logic, the consumed time is in microsecond level, and compared with the time consumed by other technical implementation modes which is in millisecond level, the time required by switching is greatly shortened.
The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, and therefore, the present invention should not be construed as limiting the scope of the present invention. It should be noted that several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims (4)

1. A system for protecting, switching and rapidly ranging an EPON network is characterized in that: the system comprises a main OLT PON port, a standby OLT PON port, an ODN and N ONUs, wherein the main OLT PON port and the N ONUs complete registration and activation and perform interaction of network services, the standby OLT PON port synchronizes service configuration of the main OLT PON port in real time, and a sending end of the standby OLT PON port is closed; when the protection switching is started, a sending end of a standby OLT PON port is opened, a Discovery2 message is sent to the ONU of the corresponding LLID, and the ONU of the corresponding LLID feeds back a Report message; the standby OLT PON port receives the Report message, extracts the timestamp information in the Report message and calculates the new loop delay time RTTnewAccording to the new loop delay time RTTnewWith old loop delay time RTToldDetermines the final RTT information.
2. The system of claim 1 for fast ranging for protection switching of an EPON network, wherein: the ODN is a 2: N optical splitter, wherein N is the number of the ONU.
3. The system of claim 2 for protection switching fast ranging of an EPON network, wherein: a force _ report setting 1 and a Discovery flag setting 0 are arranged in a flag field of a Discovery2 message; and the ONU with the corresponding LLID receives the Discovery2 message, analyzes the message and sends a Report message.
4. The system of claim 3 for protection switching fast ranging of an EPON network, wherein: new loop delay time RTTnewWith old loop delay time RTToldComparing and calculating a difference RTTdelta
1) If RTT is presentnew≥RTToldIt is noted that the trunk optical fiber distance of the standby OLT PON port is greater than or equal to the trunk optical fiber distance of the main OLT PON port, and at this time, RTT information of all ONUs stored in the standby OLT PON port needs to be read out one by one, and this difference RTT is addeddeltaAs final RTT information;
2) if RTT is presentnew<RTToldWhen the trunk optical fiber distance of the standby OLT PON port is less than the trunk optical fiber distance of the main OLT PON port, RTT information of all ONUs stored in the standby OLT PON port needs to be read out one by one, and the difference RTT is subtracteddeltaAs final RTT information.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101378311A (en) * 2007-08-27 2009-03-04 华为技术有限公司 Method, system and equipment for protecting rearrange
CN101867392A (en) * 2009-04-15 2010-10-20 中兴通讯股份有限公司 Method, equipment and system for improving type B protection switching performance
CN102368691A (en) * 2011-09-23 2012-03-07 烽火通信科技股份有限公司 Optical link protection switching realizing method in Ethernet passive optical network system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101378311A (en) * 2007-08-27 2009-03-04 华为技术有限公司 Method, system and equipment for protecting rearrange
CN101867392A (en) * 2009-04-15 2010-10-20 中兴通讯股份有限公司 Method, equipment and system for improving type B protection switching performance
CN102368691A (en) * 2011-09-23 2012-03-07 烽火通信科技股份有限公司 Optical link protection switching realizing method in Ethernet passive optical network system

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