CN101087238B - Device and method for dynamic bandwidth allocation in passive optical network - Google Patents

Abstract

The invention relates to the field of optical communication, and discloses a dynamic bandwidth allocation device and method for a passive optical network, so that the dynamic bandwidth allocation method realizes business transparency, can adapt to different types of business requirements, improves bandwidth utilization, realizes bandwidth fair allocation, and is robust It has good performance, strong real-time performance, and can allocate bandwidth to different ports, and supports offline bandwidth release of ONU at the same time. This passive optical network dynamic bandwidth allocation method includes that the optical line terminal OLT receives bandwidth assignment requests from multiple services from the optical network unit ONU; according to the reported information carried in the bandwidth assignment request of the optical network unit, performing bandwidth authorization for the services of the optical network unit; according to the bandwidth authorization information, uniformly generating authorization messages for services under the same optical network unit; sending the generated authorization messages to corresponding optical network units.

Description

Device and method for dynamic bandwidth allocation in passive optical network

technical field

The invention relates to the field of optical communication, in particular to a dynamic bandwidth allocation device and method for a passive optical network.

Background technique

Passive Optical Network ("PON" for short) means that the optical distribution network does not contain any electronic devices and electronic power supplies, and is all composed of passive devices such as optical splitters, and does not require expensive active electronic equipment. An optical access network. As an emerging broadband access optical fiber technology covering the last mile, PON does not require node equipment at the optical branch point, and only needs to install a simple optical splitter, so it has the advantages of saving optical cable resources, sharing bandwidth resources, saving It has the advantages of investment in computer room, high equipment security, fast network construction speed, and low comprehensive network construction cost. The low cost of PON has made it a popular choice for Fiber To The Building ("FTTB"), Fiber To The Curb ("FTTC"), Fiber To The Home ("FTTH") ″) is the most ideal broadband access method for FTTx networks.

As the main type of optical access network, PON is mainly divided into ATM Passive Optical Network ("APON" for short) and Ethernet Passive Optical Network ("EPON" for short). , is a point-to-multipoint master-slave control structure, as shown in Figure 1, the optical line terminal (Optical Line Terminal, referred to as "OLT") is the master node device, through the optical splitter and multiple optical network units (Optical Network Unit ("ONU" for short) is connected, and performs ONU registration, data authorization to be sent, media access control sublayer (MediaAccess Control sublayer, "MAC") message interaction, etc.; ONU is a slave node device, responding The OLT discovers the message, reports the length of the data to be sent, sends the data of each port according to the authorization information, and connects multiple user terminals to support multiple services in parallel. Under the frame structure of the optical access network, how to reasonably allocate bandwidth, effectively utilize network resources and meet business needs has become a very important content in the PON MAC solution.

In the optical access network, there are two ways of bandwidth allocation: static bandwidth allocation (Static Bandwidth Allocation, referred to as "SBA") and dynamic bandwidth allocation (Dynamic Bandwidth Allocation, referred to as "DBA"). Static bandwidth allocation fixedly allocates the bandwidth of each ONU or its port, unused time slots cannot be preempted, the bandwidth utilization rate is relatively low, and the adaptability to natural services with high burst rate is not strong. The dynamic bandwidth allocation algorithm is a mechanism or algorithm for fast bandwidth redistribution based on the current user service requirements. It can improve the PON bandwidth utilization by dynamically adjusting the bandwidth between ONUs according to the ONU burst service requirements.

At present, there are many dynamic bandwidth allocation methods, such as the PON dynamic bandwidth called Interleaved Polling with Adaptive Cycle Time ("IPACT") proposed by Glen Kramer, an employee of the University of California at Davis and Alloptic. Allocation method; a DBA protocol especially for APON proposed by the G.983.4 standard of the International Telecommunication Union-Telecommunication Standardization Sector ("ITU-T" for short).

The main idea of the IPACT method described in US Pat. No. 6,546,014 is to round-robin the next ONU before the data sent from the previous ONU reaches the OLT to determine whether to authorize and authorize the amount and other information. Some details of this method are described below with reference to FIG. 2 , in which an OLT communicates with three OUNs as an example to describe the method. Assuming that a certain polling cycle starts at time t0, the OLT has the length of the data to be sent and the round trip time (Round Trip Time, "RTT" for short) information of each ONU, and stores them in the polling table (Polling Table).

As shown in (a) in Figure 2, when the polling period starts, the OLT sends authorization information to ONU1, allowing it to send 6000 bytes. After receiving the authorization information, the ONU sends data until the end of the authorization window. While sending data to the OLT, the ONU has been receiving data from the downstream user terminal and buffering it. At the end of sending data, the ONU generates the next round of data information to be sent and reports it. In the picture it is 550 bytes.

As shown in (b) in Figure 2, before receiving the response from the previous ONU, the OLT calculates the arrival time of the last bit of the previous ONU data: the arrival time of the first bit (the RTT of the ONU) plus the arrival time of the ONU Authorized send data length. Therefore, the OLT can send the authorization information of the next ONU at the exact moment according to the RTT information of the next ONU, so that the data transmission windows of the two ONUs before and after are only separated by a guard band.

As shown in (c) in Figure 2, when all the data of ONU1 is received by the OLT, the OLT updates the information in the polling table according to the attached next round of data information to be sent, as the reference data for the next round of polling cycle. For the update of the RTT information, the OLT obtains it by tracking the authorization information sending and data receiving.

As shown in (d) in Figure 2, the OLT performs the same processing on ONU2 and ONU3.

When the cached data in an ONU is empty, the next round of reported data to be sent is set to zero, so that the authorized window is zero, and the ONU can still apply for an authorization window in the next reported data request to be sent.

If the OLT authorizes each ONU to send all the content in its cache in one sending process, those ONUs with a large amount of data may monopolize the entire bandwidth. To avoid this, the OLT will limit the maximum sending volume. Each ONU will be authorized to send the amount of data requested by it in the previous cycle, but it will not exceed the predetermined maximum limit, that is, the maximum sending window size. Different settings for the maximum limit on the amount of data sent will produce several different solutions. For example, it is fixed, based on the Service Level Agreement (Service Level Agreement, referred to as "SLA"). This scheme ignores the request window size and always grants the maximum sending window; or is limited, which authorizes the number of requested bytes but does not exceed the maximum sending window. window; or a constant credit limit (Constant Credit), which adds a constant credit limit on top of the request window; or a linear credit limit (Linear Credit), which adds a credit limit linearly proportional to the request window on top of the request window ; or elastic, which attempts to remove the constraint of a fixed maximum window, the only limiting factor being the maximum cycle time.

The control message of IPACT is not a standard APON or EPON specified message. It inserts an escape code (Escape, referred to as "ESC") character in the data stream to identify the following control message data, followed by the ONU node identifier (Node Identifier, referred to as "NID") and request authorization window size (Window Size, referred to as "WS").

In addition, in the DBA protocol proposed by the ITU-T G.983.4 standard, the business from the ONU is divided into several types of transmission adaptation containers (Transmission Container, referred to as "T-CONT"), which is essentially carrying the asynchronous transmission mode ( Asynchronous Transfer Mode, referred to as "ATM" virtual path (Virtual Path, referred to as "VP") or virtual channel (Virtual Channel, referred to as "VC") "pipe" has different quality of service (Quality of Service, referred to as "QoS") ″) required multiplexing of VP and VC to T-CONT is programmable. Each T-CONT type has its specific bandwidth allocation requirements. According to the priority of business processing, it is divided into four types of adapters from high to low, namely T-CONT1, T-CONT2, T-CONT3 and T-CONT4. T-CONT5 can adapt to all services, and its purpose is to reduce The number of transport adaptation containers. There are four types of bandwidth allocation requirements: fixed bandwidth, guaranteed bandwidth, non-guaranteed bandwidth, and best-effort bandwidth.

The DBA protocol has three strategies: Non-Status-Reporting ("NSR" for short), Status-Reporting ("SR" for short) and mixed type. For the NSR strategy, the OLT needs to monitor services; for the SR strategy, the ONU and the Optical Network Terminal ("ONT" for short) need to send status reports to the OLT; /ONT status report.

In the SR strategy, the ONU collects the status of the transmission adapters except T-CONT1, and reports to the OLT through the Physical Layer Operation, Administration, Maintenance ("PLOAM") information frame. The OLT obtains the state of each container in the ONU according to the upstream PLOAM information, and allocates guaranteed bandwidth, unguaranteed bandwidth, and best-effort transmission bandwidth to each container according to the algorithm. Various scheduling methods are used for bandwidth allocation to achieve its fairness. For example, there are algorithms such as memory, step by step, step by step increase and decrease.

The difference in the bandwidth update of these algorithms is that when a certain T-CONT is detected to be congested, the memoryless algorithm allocates more resources to the group, and the allocated resources have nothing to do with the previously allocated resources; the incremental algorithm is based on the previously allocated resources , gradually increase the allocation of more resources to this group; the gradual increase and decrease algorithm gradually reduces the resources of other groups on the basis of the previously allocated resources, so as to increase the resources allocated to this group.

In practical application, the above scheme has the following problems: it can only be applied to a system of a single nature, it cannot distinguish and process different types of services according to different policies, it cannot meet the QoS requirements of various types of services, and it cannot allocate bandwidth according to user service ports. It cannot dynamically handle the situation that the ONU is offline.

One of the main reasons for this situation is that there are no different allocation strategies for different services; the polling period in technical solution 1 is adaptively changed with the amount of data, resulting in irregular data transmission for the same service, which cannot meet the time limit. The demand for uniform real-time business; the Round-Robin fixed-sequence round-robin adopted in the second technical scheme is specially aimed at connection-oriented APON applications with fixed length of Protocol Data Unit ("PDU"). The bandwidth update mechanism is aimed at T-CONT, and bandwidth allocation cannot be performed according to different ports.

Contents of the invention

The technical problem to be solved by the present invention is to provide a dynamic bandwidth allocation device and method for a passive optical network, so that the dynamic bandwidth allocation method realizes business transparency, can adapt to different types of business requirements, improves bandwidth utilization, realizes bandwidth fair allocation, and is robust It has good performance, strong real-time performance, and can allocate bandwidth to different ports, and supports offline bandwidth release of ONU at the same time.

In order to solve the above technical problems, an embodiment of the present invention provides a dynamic bandwidth allocation method for a passive optical network, including:

The optical line terminal OLT receives bandwidth assignment requests of multiple services from the optical network unit ONU;

authorize the service of the optical network unit according to the reported information carried in the bandwidth assignment request of the optical network unit;

According to the authorized information, uniformly generate authorization messages for services under the same optical network unit;

Send the generated authorization message to a corresponding optical network unit.

An embodiment of the present invention also provides a dynamic bandwidth allocation device for a passive optical network, including: a bandwidth authorization unit, configured to receive bandwidth assignment requests from multiple services from an optical network unit; The reporting information carried in the bandwidth assignment request authorizes the service of the optical network unit;

An authorization message generation unit, configured to uniformly generate authorization messages for services under the same optical network unit according to the authorized information;

The authorization message sending unit is configured to send the generated authorization message to a corresponding optical network unit.

The embodiment of the present invention also provides a passive optical network system, including an optical line terminal OLT, the OLT communicates with a plurality of optical network units ONU; the OLT is used to receive a plurality of ONUs from the ONU A service bandwidth assignment request; according to the reported information carried in the bandwidth assignment request, authorize the service of the optical network unit; according to the authorized information, uniformly generate services under the same optical network unit An authorization message; sending the generated authorization message to a corresponding optical network unit.

By implementing the embodiments of the present invention, more obvious beneficial effects can be brought, that is, the dynamic bandwidth allocation is transparent to services, and can adapt to the necessary forwarding of TDM/EF, AF, DF and MPCP messages and the guaranteed forwarding of CPU/OAM, etc. Various business needs, improve bandwidth utilization, allocate bandwidth fairly, have good robustness, strong real-time performance, use bandwidth resources more effectively, and avoid waste of resources.

Description of drawings

FIG. 1 is a schematic diagram of a structure of a passive optical network;

Fig. 2 is a schematic diagram of the principle of the periodic self-adaptive cross round robin method;

Fig. 3 is according to an embodiment of the present invention, uplink service activates the structural diagram of ONU Bitmap register and corresponding uplink service activation port Bitmap table;

FIG. 4 is a structural diagram of an uplink vMAC reporting information table according to an embodiment of the present invention;

FIG. 5 is a flowchart of an authorization method for various services according to an embodiment of the present invention;

FIG. 6 is a structural diagram of an uplink vMAC authorization information table according to an embodiment of the present invention;

Fig. 7 is a structural diagram of an ONU state information table according to an embodiment of the present invention;

FIG. 8 is a flowchart of a method for generating an authorization message according to an embodiment of the present invention;

Fig. 9 is a structural diagram of an ONU activation timeout counting table according to an embodiment of the present invention;

Fig. 10 is a flowchart of an ONU information aging method according to an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings.

First of all, it needs to be pointed out that the dynamic bandwidth allocation method for passive optical network proposed by the present invention includes service registration, bandwidth allocation, authorization message, and ONU information aging. The invention classifies various services, and arranges different data structures for different types of services to implement different allocation strategies. The present invention also handles different ports under the same ONU separately. In addition, the present invention also monitors the state of the ONU, and dynamically releases the resource of the offline ONU. An embodiment of the present invention is described in detail below.

In order to classify services and process different ports separately, it is necessary to set the data structures of various types of services and ports so that the system can perform classification processing. In one embodiment of the present invention, business is divided into the following categories according to priority:

Fast forwarding services, such as time division multiplexing (Time Division Multiplex, referred to as "TDM"), accelerated forwarding (Expedited Forwarding, referred to as "EF"), etc., here collectively referred to as EF services, such services require real-time forwarding with uniform delay, and The bandwidth is basically unlimited, so the priority is the highest;

Multi-Point Control Protocol (Multi-Point Control Protocol, referred to as "MPCP") message service, MPCP message is used for normal MPCP communication of the system, divided into automatic discovery MPCP message and non-automatic discovery MPCP message, the relevant parameters of MPCP message are Fixed, the present invention will also judge whether it is online according to the timely MPCP message of the ONU;

Ensure forwarding (Must Forwarding, "MF" for short) services, such as Central Process Unit (Central Process Unit, "CPU" for short) messages, OAM messages, such services need to ensure the correct transmission of messages for operation, management, maintenance and Preset module (Operation Administration, Maintenance and Provisioning, referred to as "OAM&P") and communication between OLT and ONU, so the priority is also higher;

Reliable forwarding service, that is, Assured Forwarding ("AF" for short), this type of service needs to guarantee the specified minimum bandwidth, but does not have high requirements for real-time performance;

Best-effort forwarding services, such as Default Forwarding ("DF" for short), have no minimum bandwidth requirements, so they have the lowest priority.

The present invention adopts the mode of centralized control and reporting information, and the OLT manages the state of each ONU. In a preferred embodiment of the present invention, the ONU auto-discovery and message exchange of the registration process adopts the message exchange process of the IEEE802.3ah standard of the International Institute of Electrical and Electronics Engineers.

In order to facilitate round robin by business and priority when carrying out data transmission authorization, in a preferred embodiment of the present invention, the upstream business of various services is set to activate the ONU bitmap (Bitmap) register to save the information of various services. ONU activation information, such as upstream MPCP activation ONU Bitmap register (Ingress MPCP Active Bitmap, referred to as "IMAB"), upstream MF service activation ONU Bitmap register (Ingress Must Forwarding Active Bitmap, referred to as "IMFAB"), upstream EF service activation ONU Bitmap register (Ingress Expedited Forwarding ActiveBitmap, "IEFAB" for short), upstream AF service activation ONU Bitmap register (Ingress Assured Forwarding Active Bitmap, short for "IAFAB"), upstream DF service activation ONUBitmap register (Ingress Default Forwarding Active Bitmap, short for "IDFAB"); At the same time, services in units of ports include EF, AF, DF, etc. These services also need to set up the upstream service activation port bitmap (Bitmap) table to save the activation information of these services on the port, such as the upstream EF service activation Bitmap table (Ingress Expedited Forwarding Active Bitmap Table, referred to as "IEFABT"), uplink DF service activation Bitmap table (Ingress Assured Forwarding Active Bitmap Table, referred to as "IAFABT"), uplink AF service activation Bitmap table (IngressDefault Forwarding Active Bitmap Table, referred to as "IDFABT").

As shown in Figure 3, the upstream service activation ONU Bitmap register contains the corresponding bits (bits) of N ONUs, which are used to indicate whether this type of service of the ONU is activated, such as 1 indicates activation, 0 indicates inactivation; The upstream service activation port Bitmap table on the side contains the corresponding entries of N ONUs, and the content of each entry stores the information of whether such services of each port connected to the corresponding ONU are activated, such as Each port corresponds to a bit, 1 means active, 0 means inactive, and the system stores these tables in memory, and can be indexed according to the corresponding Optical Network Unit Identifier ("ONUID") (index) table entry of the corresponding ONU, so as to facilitate reading and writing of port service activation information.

It should be noted that during the service registration process, the Logical Link Identifier ("LLID") assigned to the ONU is in the form of {ONUID, port activation Bitmap}, which is convenient for using ONUID and each port Offset searches various service activation information and bandwidth allocation information tables, and facilitates the development of multicast services.

The MPCP port of the ONU is activated during the registration process, and the activation information is added to the IMAB; after the ONU is registered, the MF port is activated, and the activation information is added to the IMFAB. Here, each ONU has CPU and OAM services by default.

After the ONU successfully registers, it requests bandwidth allocation from the CPU of the OLT, and the network management communicates with the CPU of the OLT to transmit the bandwidth information. The bandwidth information includes the activation of the EF service port, the activation of the AF and DF service ports and the bandwidth of the port. The activation information of EF, AF and DF service ports are respectively added to IEFAB, IAFAB and IDFAB and corresponding entries of IEFAB, IAFAB and IDFABT, and the corresponding bits of IEFAB, IAFAB and IDFAB respectively reflect whether the ONU has EF, DF and AF services For the activation information, the corresponding entries of IEFABT, IAFABT, and IDFABT indicate that the EF, DF, and AF services of those ports of the ONU are activated.

For service ports that require bandwidth control, set up a corresponding bandwidth information table (BandwidthInformation Table, referred to as "BIT"), which is used to store the amount of data sent in each fixed polling cycle (that is, the virtual frame cycle), called the sending quantum (Transmit Quantum), its unit can be byte (Byte), word (Word), etc. The same system performs table item retrieval according to ONUID and each port offset (Offset).

Through the interaction with the network management, the OLT can dynamically operate and modify the relevant bits of the upstream service activation ONU Bitmap register, the relevant entries of the activated port Bitmap table and the relevant entries of the bandwidth information table, thereby realizing the dynamic insertion and deletion of ONU service ports and bandwidth information. reconfiguration.

In each polling cycle, the ONU reports the data length to be sent to the OLT through the REPORT message of the IEEE802.3ah standard. Each message contains 8 queue data length reporting items, and the corresponding relationship between each queue and the ONU port is predetermined, so that the OLT Ability to distinguish which port the reported length comes from. At the same time, the valid flags of each queue are set, such as dividing 8 bits corresponding to whether the 8 queues are valid items, or setting the length of the invalid queue to zero to mark the item as invalid. When the ONU has more than 8 connected ports, multiple REPORT messages are used to represent the message, and the sequence number is attached to the message to identify the continuity of multiple REPORTs in one cycle, so that the OLT can determine which report item comes from according to the received multiple messages port.

In order to process the reported information of each port separately, the OLT stores the length information of the reported data to be sent in the uplink vMAC Report Information Table (Report Information Table, referred to as "RIT") classified by Virtual MAC (Virtual MAC, referred to as "vMAC") 4 shows the structure of the table: each entry corresponds to the reporting information of each ONU port, and the system is indexed by the ONUID; for common services, such as OAM, CPU and common forwarding services, etc., the entry includes reporting information Flag (Reported Flag), reported data length to be sent (Report), where "report flag" indicates whether the vMAC reports data to be sent within the current virtual frame period, and the numerical unit of "reported data length to be sent" is sent in the bandwidth information table The unit of quantum is consistent; for MPCP message service, the table item includes reporting flag (Reported Flag), uplink MPCP message type field (Type), reserved field (Reserved), wherein the uplink MPCP message type field indicates the type of the uplink MPCP message, Such as "REGISTER REQ", "REGISTER ACK" and "Normal REPORT", etc., enable the OLT to distinguish the registration stage of the ONU so as to clarify the type of downlink MPCP message that should be generated. After the virtual frame period is determined for the EF service, the data length that the port can send within a virtual frame period is fixed, so there is no need to report the length of the data to be sent.

Bandwidth allocation, that is, service data transmission authorization, is a process in which the OLT polls the authorization according to the service priority according to the service ONU port activation information, bandwidth allocation information, and reported information. In order to meet the QoS guarantee of the EF service, the authorized period is the virtual frame period, and other bandwidth allocation operations are performed according to the virtual frame period. A method for authorizing uplink service data transmission according to an embodiment of the present invention will be described in detail below with reference to FIG. 5 .

In the present invention, according to the service priority from high to low, the order polling authorization is respectively EF service, automatic discovery of MPCP, non-automatic discovery of MPCP, MF service, AF service and DF service.

In order to facilitate the OLT to send authorization messages to various uplink services, the present invention sets up an uplink vMAC authorization information table (Grant Information Table, GIT for short), which is used to store the authorization information generated by the authorization of service transmission. When in the uplink receiving process, the OLT reads The data in the authorization information table is generated, and the authorization message is sent to the corresponding ONU to complete the bandwidth dynamic allocation process.

Fig. 5 shows the authorization method flow of various services.

In step 501, the current authorized port is determined according to the activation information of the uplink service, or the automatic discovery of MPCP messages is started according to the startup counter. For services such as EF, MF, AF, DF, and non-automatic discovery of MPCP, the uplink service activation information includes the uplink service activation ONUBitmap register and the uplink service activation port Bitmap table of various services, and polls these information to obtain the currently required operation. Class service port. For automatic discovery of MPCP, in order to dynamically register new online ONUs, a startup counter for automatic discovery of MPCP is set, and it is started every time it is full, so that the process of automatic discovery of MPCP for periodic startup does not occupy too much bandwidth.

Then enter step 502, perform authorization if the bandwidth resource permits, and record authorization window information or downlink MPCP type. The judgment of whether the bandwidth resource is allowed is based on the assigned bandwidth of the port, that is, the amount of data allowed to be sent in a virtual frame period, or the fixed data amount of MPCP, and the remaining bandwidth in the current virtual frame period. When the former is greater than the latter, the bandwidth If resources permit, authorization can be performed; or for AF services, only when the port has data to be sent to report, and the amount of reported data to be sent is not greater than the remaining amount of data that can be sent, nor greater than the sum of the amount of sent data and the amount owed by the bandwidth assigned by the port , it is determined that the bandwidth resources are allowed; or for DF services, only when the port has pending data to report and the remaining amount of data that can be sent is not less than the largest of the reported data amount and the maximum amount of bandwidth that can be sent by the bandwidth assignment, it is judged as the bandwidth resources permitting.

Among them, for the EF service, according to the scheduled data arrival time stamp and the protection band that needs to be added when the previous port in this virtual frame period belongs to a different ONU, determine its data transmission start time (Start Time) and data transmission length (Length ), and record it into the corresponding entry of the port of the GIT of this type of business. The predetermined data arrival time stamp refers to a predetermined data arrival time stamp in the next uplink virtual frame period, and the reference standard of the time stamp is a free-running clock at the OLT.

For the MPCP message service, determine the downlink MPCP message type according to the RIT uplink message type of the current MPCP port, automatically find that the MPCP is a fixed type, and write the MPCP type and authorization flag into the corresponding GIT entry of the MPCP port.

For MF and DF services, according to the data length information reported in the port RIT and the existing authorization deficit, it authorizes the corresponding length window, and writes it into the corresponding GIT entry.

For the AF service, according to the data length information reported in the port RIT and the existing authorization owed amount, it authorizes the corresponding length window, and calculates the new authorized owed amount at the same time, and writes it into the corresponding GIT entry.

Then enter step 503, update related information. The operation of updating relevant information includes updating the remaining bandwidth in the current virtual frame period, updating the current scheduled data arrival time stamp in the EF service and the remaining bandwidth in the virtual frame period, clearing the start counter of automatic discovery of MPCP, and clearing the MF, AF, and DF Corresponding to the reporting flags in the RIT table, etc., the purpose of clearing the reporting flags in the RIT table is to prevent repeated authorization from occurring in the next virtual frame period.

In a preferred embodiment of the present invention, the authorization scheduling method of the AF service adopts a leaky bucket algorithm. Those skilled in the art can understand that the authorization scheduling of the AF service can also adopt the weighted round-robin algorithm, without affecting the essence and scope of the present invention.

Then enter step 504 to judge whether any port is not authorized, if so, enter step 501, otherwise end the authorization of the original service port, and enter the authorization of the next priority service port. Among them, the auto-discovery MPCP has at most one authorization per cycle, so it directly enters the authorization of the service port of the next priority.

Fig. 6 shows the data structure of uplink vMAC authorization information table, and each entry corresponds to the authorization information of each ONU port, and the system is indexed by ONUID; Start time (StartTime), data sending length (Length), where the authorization flag indicates whether the service port is authorized, the data sending start time is the time when the port is authorized to start sending, and the data sending length is the port is authorized to send The length of the data; for the uplink MF service, the entry includes the Granted Flag, the reserved field (Reserved), and the data transmission length (Length), and the reserved field is the part that has not yet been defined; for the MPCP port, the entry contains the authorized Flag (Granted Flag), downlink MPCP message type (Type), reserved field (Reserved), wherein the downlink MPCP message type includes "DiscoveryGATE", "Normal GATE", "REGISTER&GATE", where the downlink MPCP of the "GATE" type is specially used For other services, the entry includes Granted Flag (GrantedFlag), Deficit Cnt, and Data Sending Length (Length). The accumulated authorized bandwidth of the service port in the previous uplink service cycle is more than the reported bandwidth, and the system balances the QoS guarantee of AF and DF services through the authorized deficit. In the service data sending authorization phase, only the start time of data sending is authorized for EF services, and the registration window for automatic discovery of MPCP in other services is also determined for PON systems with a certain number of ONUs and the longest extension distance. Non-automatic discovery of MPCP is due to MPCP message length is fixed, so its authorized length is also fixed, and their authorized lengths are no longer written into the authorized information table, and the authorized lengths of AF and DF service ports are not fixed to be written into the authorized information table.

In order to facilitate the management of the ONU, the present invention also sets an ONU status information table (StatusInformation Table, referred to as "SIT"), which is used to characterize the status information of the ONU. The ONU state information table is generated during the MPCP message exchange process, and the state of the ONU is determined according to the type of message exchanged between the current OLT and the ONU. Figure 7 shows the data structure of the status information table, each ONU corresponds to a table item, the system is indexed by ONUID, and the table item contains ONU status information (ONUStatus). In a preferred embodiment of the present invention, 2 bits are used to represent the ONU state information, which are respectively invalid (Invalid Entry), registered (Registered ONU), and registration (RegisteringONU), wherein invalid means that the ONUID is not assigned to any ONU, registered means that the ONU has completed the registration process and can forward business data normally, and registered means that the ONU is in the process of registration, and the specific current interaction information of the ONU in registration can be reported to the information table through the MPCP port of the ONU ( RIT) entry and authorization information table (GIT) entry.

After completing the service sending authorization operation, the OLT will generate an authorization message in the virtual frame period and send the authorization message to the corresponding ONU at a certain time. The principle of authorization message generation is: in order to generate as few authorization messages as possible for the port services of each ONU, and also to insert less guard bands and synchronization time periods between ONUs in the upstream data stream, the authorization transmission of other port services except EF The windows are adjacent to each other, so the start time of sending authorization data on ports other than EF is determined in the authorization message generation stage and written into the authorization message.

Fig. 8 shows the flow of a method for generating an authorization message according to an embodiment of the present invention.

As shown in the figure, in step 801, the ONU state information table entries are read one by one. The system generates authorization messages in units of ONUs, so that the authorization messages are carried in the downlink MPCP message of type "GATE", and can handle the unified authorization of the service ports of the same ONU.

Then enter step 802, judge whether the current ONU is invalid, if yes, enter step 801, otherwise enter step 803. If the ONU state information corresponding to the current ONUID is invalid, no authorization is performed, and the state information table is read continuously.

In step 803, GIT entries corresponding to each port of the ONU are read. The authorization information is stored in the authorization information table during the authorization process, and the authorization information of the port can be obtained by reading the entry corresponding to each port. Then go to step 804 .

In step 804, a downlink MPCP message is generated according to the authorization information. The system carries the authorization message through the downlink MPCP message, first determines the downlink MPCP message type according to the state of the ONU and the authorized MPCP message type, and then according to the authorization status of each vMAC port and the authorized scheduled data transmission inherited from the service data transmission authorization stage Timestamp, to determine the start time of sending the authorization data of each vMAC port, and write the authorization related information into the generated downlink MPCP message.

Then enter step 805, clear the authorization flag of the GIT entry, so as to avoid repeated generation of authorization information.

Then enter step 806, judge whether to have read all state information table entries, if so, then show that the generation of all ONU authorization messages has been completed, end the authorization message generation process of this virtual frame cycle, otherwise return to step 81 and continue to read the state Information Sheet.

Finally, the present invention provides a method for dealing with offline ONUs or faulty ONUs, that is, the ONU information aging process. The system sets the ONU activation timeout count table to count the non-response time of each ONU. If the count value exceeds the specified offline threshold, it will determine that the ONU is invalid and release the resources of the invalid ONU.

Figure 9 shows the data structure of the ONU activation timeout count table, each ONU corresponds to an entry, the system is indexed by the ONUID, and the entry includes a report flag (Reported), an activation timeout counter (Active Timeout Count, referred to as "ATC").

Fig. 10 shows the flow of the OUN information aging method according to one embodiment of the present invention,

As shown in the figure, in step 101, the ONU state information table entries are read one by one. The system is indexed according to the ONUID.

Then enter step 102, judge whether current ONU is valid, if yes, then enter step 103, otherwise, return to step 101, do not grant processing to invalid ONU, continue to read down.

In step 103, read the activation timeout count table entry corresponding to the ONU to determine whether the ONU is offline, and then enter step 104.

In step 104, according to whether the MPCP message is reported, the activation timeout counter is cleared or counted, and the reporting flag is cleared. The system operates on the activation timeout counter according to whether the ONU reports an MPCP message within the current virtual frame period. If so, it is cleared, otherwise it is counted.

Then enter step 105, judge whether the activation timeout counter exceeds the offline threshold, if yes, show that this ONU is offline, enter step 106; Otherwise, indicate that this ONU is online, enter step 107.

In step 106, set the ONU state information table entry corresponding to the ONU to an invalid state, and release the relevant resources of the ONU, and then enter step 107. For an offline ONU, the system sets invalid in the status information table, indicating that the ONU does not exist. The relevant resources of the ONU include: the corresponding bits of the uplink service activation Bitmap registers IMPAB, IMFAB, IEFAB, IAFAB, and IDFAB, the corresponding entries of the uplink service activation Bitmap tables IEFAT, IAFAT, and IDFAT, the corresponding entries of the bandwidth information table, and the original ONUID assigned to this ONU.

In step 107, it is judged whether all state information table entries have been read, and if so, the ONU information aging process of this virtual frame cycle is ended, otherwise step 101 is returned to continue reading the state information table.

The present invention is applicable to a master-slave system in which the OLT controls ONU access. The OLT controls the forwarding and access of all upstream business data of the ONU, including MPCP or other MAC messages, and the downstream is broadcast mode. The data is filtered and received at the ONU, and the downstream The transmission scheduling is also based on priority, and the downlink scheduling and forwarding is performed in the priority order of EF, MPCP, CPU/OAM, AF, and DF.

Although the present invention has been illustrated and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein, and without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (13)

1. A dynamic bandwidth allocation method for a passive optical network, characterized in that, comprising: The optical line terminal OLT receives bandwidth assignment requests of multiple services from the optical network unit ONU; authorize the service of the optical network unit according to the reported information carried in the bandwidth assignment request of the optical network unit; According to the authorized information, uniformly generate authorization messages for services under the same optical network unit; Send the generated authorization message to a corresponding optical network unit. 2. The method according to claim 1, wherein said generating an authorization message comprises: Generate authorization messages in units of ONUs. 3. The method according to claim 1, wherein when sending the authorization message to the ONU, the authorization sending windows of at least two services of the same ONU are adjacent to each other. 4. The method according to claim 1, wherein when authorizing the service of the optical network unit, Authorization is performed in units of service ports. 5. The method according to claim 1 or 4, wherein when authorizing the service of the optical network unit, Authorize according to predetermined priority. 6. The method according to claim 1, further comprising: The non-response time of each ONU is recorded, and when the non-response time reaches a preset threshold, the resources of the ONU are released. 7. The method according to claim 6, further comprising: Establish an ONU activation timeout counter table to record the non-response time of each ONU. 8. A dynamic bandwidth allocation device for a passive optical network, characterized in that it comprises: The bandwidth authorization unit is configured to receive bandwidth assignment requests from multiple services of the optical network unit; perform the service for the optical network unit according to the reported information carried in the bandwidth assignment request of the optical network unit authorization; An authorization message generation unit, configured to uniformly generate authorization messages for services under the same optical network unit according to the authorized information; The authorization message sending unit is configured to send the generated authorization message to a corresponding optical network unit. 9. The dynamic bandwidth allocation device according to claim 8, further comprising: Aging processing unit: used to record the non-response time of each ONU, and release the resources of the ONU when the non-response time reaches a preset threshold. 10. A passive optical network system, comprising an optical line terminal OLT, said OLT communicates with a plurality of optical network units ONU, characterized in that: The OLT is configured to receive bandwidth assignment requests of multiple services from the ONU; authorize the services of the optical network unit according to the reported information carried in the bandwidth assignment request; For the authorization information, an authorization message is uniformly generated for services under the same optical network unit; and the generated authorization message is sent to a corresponding optical network unit. 11. The passive optical network system according to claim 10, characterized in that: When the OLT generates the authorization message, it generates the authorization message in units of ONUs. 12. The passive optical network system according to claim 10, characterized in that: When the OLT sends the authorization message to the corresponding optical network unit, the authorization sending windows of at least two services of the same optical network unit are adjacent to each other. 13. The passive optical network system according to claim 10, characterized in that: When the OLT authorizes the service of the optical network unit, the authorization is performed in units of service ports.

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