JP2011223085A - Mpcp link management circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the number of timers to reduce a circuit scale.SOLUTION: An MPCP link management circuit comprises: a link management unit 21 which determines a status S1 indicating that a Register Request frame of MPCP is received and a process to establish a link with ONU is in progress and a status S2 sending a Gate frame that notifies at regular intervals a transmission timing of an uplink signal of ONU after a Register ACK frame is received and a link is established with ONU; and a shared timer 22 which functions in the status S1 as a Register ACK timer counting a waiting period of the Register ACK frame after sending the Gate frame and notifying a time-out when the Register ACK frame is not received in the waiting period and functions in the status S2 as a Gate periodic timer counting a transmission interval of the Gate frames being transmitted to ONU and notifying a time-out when the transmission interval surpasses a specified value.

Description

  The present invention controls communication between an OLT (Optical Line Terminal: optical subscriber line terminating device) and a plurality of ONUs (Optical Network Unit: optical subscriber line network devices) constituting a PON (Passive Optical Network) system. The present invention relates to an MPCP link management circuit used for MPCP (Multi-point Control Protocol) link management.

FIG. 1 shows a configuration example of a PON system (Non-Patent Documents 1 and 2).
In FIG. 1, a PON system includes an OLT 101 installed in a station, a plurality of m ONUs 102 installed in each user's house, an optical fiber 103 and an optical fiber that connect the OLT 101 and the plurality of m ONUs 102 to 1: m. And a splitter 104. An external network 105 is connected to the OLT 101.

  In the PON system, upstream signals transmitted from a plurality of ONUs 102 are bundled by the optical splitter 104 and reach the OLT 101. Accordingly, IEEE 802.3 and IEEE 802.3av define MPCP for controlling the timing at which each ONU transmits an upstream signal so that the upstream signal does not collide with each other. The OLT periodically performs a discovery process based on MPCP to establish a link with a new ONU.

Here, an overview of the Discovery process will be described with reference to FIGS. The following (1) to (7) correspond to the MPCP frames shown in FIG.
(1) The OLT transmits a Discovery Gate frame to all ONUs. In this Discovery Gate frame, the local time t1 of the OLT is described as a time stamp.
(2) When an ONU that has not established a link with the OLT receives the Discovery Gate frame, the local time of the ONU is set to t1 described in the Discovery Gate frame, and time synchronization with the OLT is performed. Further, the ONU transmits a Register Request frame to the OLT after a random time from the time specified in the Discovery Gate frame, and requests registration.

  In this Register Request frame, time t2 when the ONU transmits the Register Request frame is described as a time stamp. When the OLT receives the Register Request frame, the OLT detects the reception time t3, and calculates the round-trip propagation delay time (RTT: Round Trip Time) between the OLT and the ONU as (t3-t2). The RTT measurement principle is shown in FIG.

(3) The OLT assigns a unique identifier (LLID: Logical Link IDentifier) to the ONU that has transmitted the Register Request frame, and transmits a Register frame in which the LLID is described.

(4) Subsequently, the OLT transmits a Gate frame to the ONU and waits for a Register ACK frame transmitted from the ONU. At this time, the OLT calculates the reception start time T0 and the receivable period L1 (Grant Length) according to a band update algorithm described later so that the Register ACK frame from the ONU does not collide with a transmission frame from another ONU. Then, as shown in FIG. 4, by subtracting RTT from T0, the transmission start time T1 (Grant Start Time) of the Register ACK frame is calculated at the local time of the ONU, and T1 and L1 are described in the Gate frame and transmitted. To do. Here, the end point of the receivable period L1 from the reception start time T0 where the OLT waits for the arrival of the Register ACK frame is referred to as a reception end time (Grant End Time). At this acceptance end time (Grant End Time), R1 and T1 (Grant Length) are added to T1 (Grant Start Time), and the allowable amount (guard Threshold OLT) when the time stamp of the received frame drifts. The added value is set.

(5) When the ONU receives the Register frame and the Gate frame, the ONU transmits a Register ACK frame between the transmission start time T1 designated by the Gate frame and the OLT receivable period L1. At this time, the LLID described in the Register frame is described in the Register ACK frame.

  When the OLT receives the Register ACK frame before the acceptance end time (Grant End Time), the link between the OLT and the ONU is established. On the other hand, if the Register ACK frame cannot be received from the ONU by the reception end time (Grant End Time), the OLT ends the ONU registration procedure. This is the Discovery process.

(6) The OLT that has established a link with the ONU transmits a Gate frame describing the ONU upstream signal transmission start time T2 and the receivable period L2.
(7) When the ONU receives the Gate frame, the ONU waits for transmission until the transmission start time T2 specified therein, calculates the amount of frames waiting for transmission during that time, and transmits the transmission frame in the Report frame between T2 and L2. Inform the OLT of the amount.

  The OLT assembles the order of transmission start times for each ONU according to the transmission frame amount and bandwidth allocation algorithm (DBA: Dynamic Bandwidth Allocation) notified in the Report frame from each ONU, and sequentially sends the Gate frame toward the ONU. To do. When the ONU receives the Gate frame, the ONU transmits an uplink frame (MAC frame) during a period specified by the Gate frame, and also transmits a Report frame for receiving the next Gate frame. The OLT and the ONU repeat the communication according to the above procedure. If the OLT does not transmit a bandwidth allocation gate frame to the ONU for 50 msec, the OLT sends a keep alive frame with an allocation bandwidth of zero separately from the DBA algorithm instruction. This is sent to the ONU to notify that the link is maintained.

FIG. 5 shows a configuration example of the OLT.
In FIG. 5, an upstream frame input from the PON side to the OLT is input to the reception processing circuit 52 via the PON side transmission / reception circuit 51, and is separated into an MPCP frame and a user frame other than the MPCP frame. The MPCP frame is input to the MPCP link management circuit 53, and the user frame is transferred to the external network via the bridge circuit 54 and the external network side transmission / reception circuit 55. The user frame input to the OLT from the external network side is input to the transmission processing circuit 56 via the external network side transmission / reception circuit 55 and the bridge circuit 54, multiplexed with the MPCP frame output from the MPCP link management circuit 53, and PON Is transmitted to the PON side via the side transmission / reception circuit 51.

FIG. 6 shows a configuration example of the conventional MPCP link management circuit 53.
In FIG. 6, the MPCP link management circuit 53 includes an MPCP frame transmission / reception unit 10, a link management unit 11, and a number of Register ACK timers 12 and Gate periodic timers 13 equal to the number of connected ONUs. When receiving the MPCP frame from the reception processing circuit 52, the MPCP frame transmission / reception unit 10 notifies the link management unit 11 of a frame reception notification. Also, the MPCP frame transmission / reception unit 10 receives the transmission frame information and the frame transmission instruction output from the link management unit 11, creates various MPCP frames and outputs them to the transmission processing circuit 56, and sends a frame transmission notification when the output is completed. Notify the link manager 11. Note that the transmission frame information output from the link management unit 11 includes the type of frame to be transmitted and the bandwidth allocation amount.

  The link management unit 11 performs time-out determination by the Register ACK timer 12 and the Gate periodic timer 13 of the corresponding ONU in response to the frame reception notification, the frame transmission instruction, and the frame transmission notification. As will be described in detail later, the OLT based on MPCP and the ONU Manage the link status of

  The Register ACK timer 12 is used to determine whether or not the OLT that has transmitted the Register frame and the Gate frame has received the Register ACK frame transmitted from the ONU until the Grand End Time. The register ACK timer 12 is composed of a counter. When the start signal is input when the enable signal is high, the register ACK timer 12 starts counting from 0, and outputs a timeout when the count reaches the measurement time input from the link management unit 11. .

  The Gate periodic timer 13 is used to determine whether or not the OLT has output a band allocation Gate frame to each ONU within 50 msec. The Gate periodic timer 13 is composed of a counter, and starts counting from 0 when a start signal is input when the enable signal is High, and outputs a timeout when the count reaches 50 msec.

  FIG. 7 shows the link state transition between the OLT and the ONU managed by the link management unit 11. S0 represents an initial state in which a link with the ONU has not been established, S1 represents a state in which link establishment processing is being performed, and S2 represents a state in which a link has been established. FIG. 8 shows the measurement time of the Register ACK timer 12. FIG. 9 shows the measurement time of the Gate periodic timer 13.

  First, the case where the Register ACK frame does not arrive from the ONU after the OLT transmits the Register frame and the Gate frame and the Register ACK timer 12 times out will be described with reference to FIGS.

  When the link management unit 11 of the MPCP link management circuit of the OLT detects reception of the Register Request frame (FIG. 2, 8: (2)) from the ONU by the frame reception notification of the MPCP frame transmission / reception unit 10, the link with the ONU The state transition number indicating the state is changed from S0 to S1. At the same time, the register ACK timer 12 is started by setting the enable signal for the Register ACK timer 12 to High.

  Next, the OLT transmits a Register frame (FIG. 2, 8: (3)) describing the LLID to the ONU. Subsequently, the OLT transmits a Gate frame (FIG. 2, 8: (4)) describing the Grant Start Time (T1) and Grant Length (L1) of the Register ACK frame. The link management unit 11 calculates the Grant END time of the Register ACK frame when this Gate frame is output, and sets the measurement time obtained by subtracting the local time of the OLT from the Register ACK timer 12. Then, the start signal is set to High to instruct the count start of the Register ACK timer 12.

  The Register ACK timer 12 counts up to Grant End Time. If the Register ACK timer 12 has not received a Register ACK frame before that time, the timeout is determined and notified to the link management unit 11. The link management unit 11 changes the state transition number from S1 to S0 based on the timeout determination, sets the enable signal for the Register ACK timer 12 to Low, and stops the Register ACK timer 12.

  Note that the measurement time of the Register ACK timer 12 in the above operation example is from the output of the Gate frame to the Grant End Time, but the Register ACK timer 12 has a period of Grant Length (L1) from the reception start time (T1 + RTT). May be configured to count.

  Next, referring to FIG. 2, FIG. 6, FIG. 7, and FIG. 9, the OLT receives a Register ACK frame from the ONU after transmitting the Register frame and the Gate frame, and after establishing the link between the OLT and the ONU, Will be described when the Gate periodic timer 13 times out.

  When the link management unit 11 of the MPCP link management circuit of the OLT receives the Register ACK frame (FIG. 2, 9: (5)) from the ONU by the frame reception notification of the MPCP frame transmission / reception unit 10, the link with the ONU is established. The state transition number is changed from S1 to S2, the enable signal for the Register ACK timer 12 is set to Low, and the Register ACK timer 12 is stopped. At the same time, the gate periodic timer 13 is started by setting the enable signal for the Gate periodic timer 13 to High.

  Next, the OLT periodically transmits a Gate frame (FIG. 2, 9: (6)) describing Grant Start Time and Grant Length, and the ONU transmits a Report frame (FIG. 2, 9: (7)) according to the instruction of the OLT. ). Further, when outputting the Gate frame after the link is established, the OLT sets the start signal for the Gate periodic timer 13 to High and instructs the gate periodic timer 13 to start counting. When the Gate periodic timer 13 receives a start signal, it starts counting 50 msec each time.

  Here, when the Gate periodic timer 13 times out, the Gate periodic timer 13 determines the timeout and notifies the link management unit 11 of it. The link management unit 11 controls to output a keep alive frame instead of the gate frame, and the OLT transmits a keep alive frame (FIG. 9: (8)) to the ONU. At this time, the link management unit 11 outputs a start signal to the Gate periodic timer 13 and starts counting again. As a result, the OLT can notify the ONU that does not allocate the band that the link is connected.

  As described above, the measurement time of the Gate periodic timer 13 is 50 msec after the Gate frame is output.

  If the ONU does not transmit the MPCP frame to the OLT for a certain period, the link management unit 11 determines that the link with the ONU has been disconnected, changes the state transition number from S2 to S0, and sets the Gate periodic timer. The gate periodic timer 13 is stopped by setting the enable signal for 13 to Low. The same applies when the OLT autonomously disconnects the link with the ONU.

IEEE Std 802.3-2005: Part 3: Carrier sense multiple access with collision detection (CSMA / CD) access method and physical layer specifications IEEE Std 802.3avTM-2009: Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA / CD) Access Method and Physical Layer Specifications

  The conventional MPCP link management circuit uses the Register ACK timer 12 and the Gate periodic timer 13 to determine timeouts. That is, the Register ACK timer 12 is activated when the OLT enters the link establishment processing state S1, and is used for control to determine a timeout when the Register ACK frame cannot be received within a specified waiting time and to switch to the initial state S0. On the other hand, if a Register ACK frame is received within the specified standby time, the link establishment state S2 is entered, and the Gate periodic timer 13 is started. In the link establishment state S2, the OLT periodically outputs a Gate frame, but the Gate periodic timer 13 determines a timeout when the Gate frame is not output within the specified time, and outputs a Keep alive frame to change the link establishment state S2. Used for continued control.

  As described above, in the conventional MPCP link management circuit, the two timers are individually operated according to the link state between the OLT and the ONU, and only the number of ONUs connected to the OLT is necessary. The circuit configuration was large.

  The present invention provides an MPCP link management circuit capable of reducing the number of timers and reducing the circuit scale by making it possible to determine two types of timeout with one type of timer in accordance with the state transition of the OLT. With the goal.

  The present invention relates to a discovery process of an MPCP discovery process in an MPT link management circuit of an OLT that performs link management in accordance with a specification of MPCP that controls the timing at which a plurality of ONUs connected via an optical fiber and an optical splitter transmit uplink signals. Send a Gate frame to the ONU, receive a Register Request frame sent by the ONU, send a Discovery process Register frame and a Gate frame to the ONU, and receive a Register ACK frame sent by the ONU to the ONU, An MPCP frame transmission / reception unit that outputs a transmission notification and a reception notification of each frame, and a state S1 indicating that a link establishment process with the ONU is being performed is determined based on the transmission notification of the Discovery Gate frame and the reception notification of the Register Request frame. Frame transmission notification and Register ACK frame A link management unit for determining a state S2 for transmitting a Gate frame for notifying a transmission timing of an upstream signal of the ONU at regular intervals by establishing a link with the ONU by the reception notification of the network, and in the state S1, A Gate ACK timer that functions as a Register ACK timer that counts the waiting period of a Register ACK frame after transmitting a frame, and notifies a timeout when no Register ACK frame is received during the waiting period. It has a shared timer that functions as a Gate periodic timer that counts the frame transmission interval and notifies that a timeout occurs when the transmission interval exceeds a specified value, and the link management unit is shared according to state S1 or state S2. The timer is controlled to function as a Register ACK timer or Gate periodic timer, and the Register ACK timer In this configuration, the state S1 is switched to the initial state S0 when a notification is sent, and when the Gate periodic timer notifies the timeout, the MPCP frame transmitting / receiving unit is controlled to transmit the keep alive frame to the timed ONU. .

  In the MPCP link management circuit of the present invention, the link management unit is configured to restart counting using the shared timer as a Gate periodic timer when receiving a keep alive frame transmission notification from the MPCP frame transmission / reception unit.

  In the MPCP link management circuit of the present invention, the shared timer is configured to notify the MPCP frame transmission / reception unit of the Gate periodic timer timeout, and the MPCP frame transmission / reception unit receives a keep-alive notification when the Gate periodic timer timeout is received. A configuration may be adopted in which control is performed to transmit a frame, and the count is restarted after the transmission by using a shared timer as a Gate periodic timer.

  The MPCP link management circuit of the present invention operates the shared timer as a Register ACK timer in the state S1 or a Gate periodic timer in the state S2 according to the link state between the OLT and the ONU, and determines the corresponding timeout respectively. The circuit scale can be reduced by reducing the number.

It is a figure which shows the structural example of a PON system. It is a figure explaining the outline | summary of a Discovery process. It is a figure explaining the measurement principle of RTT. It is a figure explaining the waiting period of the Register ACK frame in OLT. It is a figure which shows the structural example of OLT. It is a figure which shows the structural example of the conventional MPCP link management circuit. It is a figure which shows the link state transition of OLT and ONU which the link management part 11 manages. 6 is a time chart showing the measurement time of the Register ACK timer 12. 5 is a time chart showing the measurement time of the Gate periodic timer 13. It is a figure which shows the structural example of Example 1 of the MPCP link management circuit of this invention. It is a time chart which shows the operation example of the MPCP link management circuit of this invention. It is a figure which shows the structural example of Example 2 of the MPCP link management circuit of this invention.

FIG. 10 shows a configuration example of Embodiment 1 of the MPCP link management circuit of the present invention.
10, the MPCP link management circuit according to the first embodiment includes an MPCP frame transmission / reception unit 20, a link management unit 21, and a number of shared timers 22 equal to the number of connected ONUs. When receiving the MPCP frame from the reception processing circuit 52 shown in FIG. 5, the MPCP frame transmission / reception unit 20 notifies the link management unit 21 of a frame reception notification. Further, when receiving the transmission frame information and the frame transmission instruction output from the link management unit 21, the MPCP frame transmission / reception unit 20 creates various MPCP frames and outputs them to the transmission processing circuit 56 shown in FIG. The link management unit 21 is notified of the frame transmission notification. Note that the transmission frame information output from the link management unit 11 includes the type of frame to be transmitted and the bandwidth allocation amount.

  The link management unit 21 manages the link state of the OLT and the ONU, causes the shared timer 22 to function as a Register ACK timer or a Gate periodic timer according to the link state, and instructs the start of each timeout determination.

Hereinafter, an operation example of the MPCP link management circuit according to the first embodiment will be described with reference to FIGS. 10 and 11.
When the link management unit 21 of the MPCP link management circuit of the OLT detects a Register Request frame (FIG. 2, 11: (2)) from the ONU based on the frame reception notification of the MPCP frame transmission / reception unit 20, the link status with the ONU is displayed. The indicated state transition number is changed from S0 to S1. At the same time, the enable signal for the shared timer 22 is set to High to start the shared timer 22 and notify the shared timer 22 of the state transition number S1. The shared timer 22 operates as a Register ACK timer according to the state transition number S1.

  Next, the OLT transmits a Register frame (FIG. 2, 11: (3)) describing the LLID to the ONU. Subsequently, the OLT transmits a Gate frame (FIG. 2, 11: (4)) in which the Grant Start Time (T1) and Grant Length (L1) of the Register ACK frame are described. The link management unit 21 calculates the measurement time for waiting for the Register ACK frame after outputting this Gate frame, sets it in the shared timer 22, sets the start signal to High, and instructs the shared timer 22 to start counting.

  The shared timer 22 counts the measurement time, and if a register ACK frame cannot be received by that time, it determines a timeout and notifies the link management unit 21 of the timeout. The link management unit 21 changes the state transition number from S1 to S0, sets the enable signal for the shared timer 22 to Low, and stops the shared timer 22.

  On the other hand, if the link management unit 21 receives a Register ACK frame (FIG. 2, 11: (5)) from the ONU before the shared timer 22 times out, it determines that the link with the ONU has been established, and the state transition The number is changed from S1 to S2. At the same time, the enable signal for the shared timer 22 is maintained at High, and the shared timer 22 is notified of the state transition number S2. The shared timer 22 operates as a Gate periodic timer according to the state transition number S2.

  Next, the OLT periodically transmits a Gate frame (FIG. 2, 11: (6)) in which Grant Start Time and Grant Length are described, and the ONU transmits a Report frame (FIG. 2, 11: (7)) according to the instruction of the OLT. ). Further, when outputting the Gate frame after the link is established, the OLT sets the start signal for the shared timer 22 to High and instructs the shared timer 22 to start counting. The shared timer 22 starts counting 50 msec each time it receives a start signal.

  Here, when the shared timer 22 operating as the Gate periodic timer times out, the shared timer 22 notifies the link management unit 21 of the timeout. The link management unit 21 controls the MPCP frame transmission / reception unit 20 to output a keep alive frame instead of the gate frame, and the MPCP frame transmission / reception unit 20 sends a keep alive frame (FIG. 11: (8)) to the ONU that has timed out. ) And a frame transmission notification to the link management unit 21. When the link management unit 21 receives a frame transmission notification from the MPCP frame transmission / reception unit 20, the link management unit 21 outputs a start signal to the shared timer 22 and starts counting again as a Gate periodic timer. As a result, the OLT can notify the ONU that does not allocate the band that the link is connected.

  As described above, the shared timer 22 stops operating at the state transition number S0, operates as a Register ACK timer at the state transition number S1, and the measurement time is set to the standby time of the Register ACK frame, and the state transition number S2 It operates as a Gate periodic timer and the measurement time is 50 msec after the Gate frame is output.

FIG. 12 shows a configuration example of the second embodiment of the MPCP link management circuit of the present invention.
The feature of the present embodiment is that, in the configuration of the first embodiment, when the shared timer 22 detects the timeout of the Gate periodic timer, the MPCP frame transmitting / receiving unit 20 is notified of the timeout. When the MPCP frame transmission / reception unit 20 receives the timeout of the Gate periodic timer from the shared timer 22, the MPCP frame transmission / reception unit 20 creates and transmits a keep alive frame for the timed-out ONU, and directly outputs a start signal instead of the frame transmission notification to the shared timer 22. Start counting again as Gate periodic timer.

  The common timer 22 in each embodiment described above is configured to count with the enable signal and the start signal and notify the timeout when the measurement time is reached, but the common timer has reached the set time. However, the present invention is not limited to the above configuration. For example, the timer may be configured by a counter that counts up with a start signal and resets the count to 0 with a reset signal. Or it is good also as a structure which implement | achieves by the combinational circuit whether the local time of OLT became equal to the set time.

  The MPCP link management circuit of the present invention can be applied to the case where the frame transmission rate of the ONU connected to the OLT is only 1 Gbps, only 10 Gbps, or a mixture of 1 Gbps and 10 Gbps.

11, 21 Link management unit 12 Register ACK timer 13 Gate periodic timer 22 Shared timer 101 OLT
102 ONU
103 optical fiber 104 optical splitter 105 external network

Claims (3)

OLT (Optical Line Terminal) that performs link management in accordance with MPCP (Multi-point Control Protocol) regulations that control the timing at which multiple ONUs (Optical Network Units) connected via optical fibers and optical splitters transmit upstream signals In the MPCP link management circuit of
A Discovery Gate frame of the MPCP Discovery process is transmitted to the ONU, and a Register Request frame transmitted by the ONU is received, and a Register frame and a Gate frame of the Discovery process are transmitted to the ONU. An MPCP frame transmission / reception unit that receives a Register ACK frame transmitted by the ONU and outputs a transmission notification and a reception notification of each frame;
The state S1 indicating that the link establishment process with the ONU is being performed is determined based on the discovery gate frame transmission notification and the register request frame reception notification, and the register frame and gate frame transmission notification and the register ACK frame reception notification are determined. A link management unit for determining a state S2 for transmitting a Gate frame that notifies the transmission timing of the upstream signal of the ONU at regular intervals after a link with the ONU is established;
In the state S1, it functions as a Register ACK timer that counts the waiting period of the Register ACK frame after transmitting the Gate frame, and notifies a timeout when the Register ACK frame is not received during the waiting period; A shared timer that functions as a Gate periodic timer that counts the transmission interval of the Gate frame to be transmitted to the ONU when the state S2, and notifies a timeout when the transmission interval exceeds a specified value;
The link management unit performs control to cause the shared timer to function as the Register ACK timer or the Gate periodic timer according to the state S1 or the state S2, and the state when the Register ACK timer reports a timeout. When S1 is switched to the initial state S0 and the Gate periodic timer notifies the timeout, the MPCP frame transmitting / receiving unit is controlled to transmit a keep alive frame to the timed ONU. MPCP link management circuit. The MPCP link management circuit according to claim 1,
The link management unit is configured to restart counting using the shared timer as the Gate periodic timer when receiving a transmission notification of the Keep alive frame from the MPCP frame transmission / reception unit. . The MPCP link management circuit according to claim 1,
The shared timer is configured to notify the MPCP frame transmission / reception unit of a timeout of the Gate periodic timer,
The MPCP frame transmission / reception unit is configured to perform control to transmit the Keep alive frame when receiving a notification of timeout of the Gate periodic timer, and to restart counting using the shared timer as the Gate periodic timer after the transmission. An MPCP link management circuit.

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