JP7314728B2 - Communication path switching method, communication path switching method - Google Patents

Description

The present invention relates to a technology for constructing a virtual LAN using switching hubs compatible with PTP (Precision Time Protocol) and switching redundant paths between the switching hubs when executing PTP time synchronization.

(1) PTP described in Non-Patent Document 1 is a relatively new protocol that realizes highly accurate time synchronization by limiting the usage environment to a LAN, and its specification is defined as IEEE1588.

In PTP, a "Grandmaster (hereinafter referred to as GM)" distributes highly accurate time, and slaves receive the time distribution. In addition, high-precision time synchronization (time stamp accuracy of microseconds RMS or less) is realized by using a hardware time stamp function implemented in the network interface MAC (Media Access Control) and PHY (Physical Layer Chip).

Currently, there are two versions of the PTP protocol. Version 1 provides a segmented "Boundary Clock (BC)" for large-scale deployment. On the other hand, in version 2, a switching hub (hereinafter abbreviated as a hub) with a delay management function, ie, "Transparent Clock" is prepared, enabling more flexible and highly accurate expansion.

(2) There is a type of PTP-compatible switching hub (hereafter referred to as a PTP hub) in which a PTP function is incorporated in the L2 hub, enabling time synchronization with a high-precision grandmaster (GM).

In the case of this type, when PTP hubs are connected to each other, a master is automatically selected from the PTP hub group by exchanging PTP packets between the PTP hubs, and other slave PTP hubs can time-synchronize with the time of the selected master PTP hub.

Also, the master PTP hub periodically transmits PTP packets to slave PTP hubs in order to maintain time synchronization. There is also a PTP hub that notifies peripheral devices other than the PTP hub of state information (hereinafter referred to as a PTP information packet) inside the PTP hub at regular intervals.

(3) Virtual LANs (VLANs) are often used in corporate networks (LANs). VLAN establishes a virtual group of terminals separately from the physical connection form, and uses the function of a device called a LAN switch to group the terminals according to the MAC address or IP address of the terminal and the protocol to be used. The network configuration can be changed without worrying about the physical location of the terminal, and there is no need to change the settings even if the terminal is moved.

“Endrum IEEE1588 PTP Grandmaster Clock”, [online], searched on October 15, 2018, Internet <URL: https://www.shoshin.co.jp/c/endrum/1588ptp.html>

Although VLANs are not considered in the PTP function specifications, the PTP hub has a switching function between PTP routes divided by VLANs. However, since the switching function of the PTP hub is a simplified version of VLAN switching for built-in processing, a master-side VLAN route and a slave-side VLAN route are defined, and time synchronization is mainly performed on the master-side VLAN route (main route).

That is, only when an abnormality is detected in the master-side VLAN route, it switches to the slave-side VLAN route (secondary route), and when the abnormality in the master-side VLAN route is resolved, it returns to the master-side VLAN route again. If this method is used in the normal PTP network configuration shown in FIGS. 1(a) and 1(c), it will pass through the same network (in the case of duplexing shown in FIG. 1(c), within a network divided by VLAN), so there is no particular problem.

However, as shown in FIGS. 1(b) and 1(d), when PTP hubs are redundantly connected via normal hubs, a large delay may occur between the route on the main VLAN 10 side (main route) and the route on the sub VLAN 20 side (secondary route).

In this case, it is necessary to use a route with a small delay as the main route (main route) in order to improve the performance of time synchronization. Also, when VLAN 10 with higher priority is restored after changing to the route on the VLAN 20 side, it is not uncommon to not want to easily return to the route with higher priority because VLAN 20 has a smaller delay.

The present invention has been made to solve such conventional problems, and aims to achieve more accurate time synchronization by incorporating a virtual LAN path (route) automatic switching function into the PTP function to select a path that is less affected by delay.

(1) One aspect of the present invention is
A method of constructing a virtual LAN with switching hubs compatible with PTP (Precision Time Protocol) and switching redundant paths between the switching hubs when performing PTP time synchronization,
Collecting route transit time information between the master and slave executing the PTP time synchronization for both the main route and the secondary route between the switching hubs;
The main route and the secondary route are switched based on the collected route transit time information.

(2) Another aspect of the present invention is
A method of constructing a virtual LAN using switching hubs compatible with PTP (Precision Time Protocol) and switching redundant paths between the switching hubs when executing PTP time synchronization,
a step of collecting path transit time information between a master and a slave executing the PTP time synchronization for both the main path and the secondary path between the switching hubs;
switching between the main route and the secondary route based on the collected route transit time information;
characterized by having

According to the present invention, the virtual LAN route automatic switching function incorporated in the PTP function selects a route less affected by delay, so that more accurate time synchronization can be realized.

(a) is an example of VLAN specifications for PTP hubs showing a connection state between single VLANs, (b) is an example of VLAN specifications with redundancy between the same PTP hubs, (c) is an example of VLAN specifications showing a dual connection state of PTP hubs, and (d) is an example of VLAN specifications with redundant VLANs between the same PTP hubs. 4 is a flowchart showing the overall processing of a communication path switching method (switching method) according to the embodiment of the present invention; FIG. 3 is a flowchart showing details of S05 in FIG. 2; FIG. FIG. 4 is a flowchart showing details of S20 and S25 in FIG. 3; FIG. FIG. 4 is a flowchart showing details of S18 in FIG. 3; FIG.

A communication path switching system (switching method) according to the embodiment of the present invention will be described below. Here, at the time of switching between the main path (main master-side VLAN route) and the secondary path (sub-slave-side VLAN route) of the redundant VLAN, the "Meanpath" between the master and slave of the PTP hub and the offset value are greatly suppressed.

(1) As for the PTP hubs, one hub is automatically selected as a master (synchronization source), and the other hubs become slaves (synchronization destinations), and synchronize the time by reciprocating PTP packets between the master and the slaves.

Here, in order to establish a master-slave hierarchy, an "Announce message" is sent from the master to the slaves, and then the time transfer process is executed. Specifically, first, the master transmits a "Sync message" to the slave, and the transmission time is t1.

Next, the slave sets the time at which it received the "Sync message" to be t2, and transmits a "Delay_req message (delay request message)" to the master. Let this transmission time be t3.

When the master receives this "Delay_req message", the reception time is set to t4. The master also sends a "Delay_Resp message (delay response message)" including time t4 to the slave. The process up to this point is one step of the "PTP" packet.

At this time, if the transmission time “T1 (outbound)” and the transmission time “T2 (return)” are the same, the time difference between the slave and the master is calculated as “time difference={(t2−t1)−(t4−t3)}/2”. The calculated time difference is used to correct the time of the slave. As an option, a "Follow_up message" including time t1 may be sent from the master to the slave. In this case the slave can extract the time t1 from the message.

(2) The switching method mainly assumes a VLAN configuration in which PTP hubs are redundantly connected via normal hubs, such as the network configuration shown in FIGS. 1(b) and 1(d).

FIG. 1(b) shows a connection configuration between single VLANs in which hubs 5-8 are provided for redundancy between a master PTP hub 1 and slave PTP hubs 2-4. FIG. 1(d) shows a duplexed VLAN connection configuration in which the connections between the master PTP hub 11 and the slave PTP hubs 12 and 13 are duplexed by VLANs 10 and 20, and the VLANs 10 and 20 are relayed by hubs 14-19.

Here, it is assumed that the PTP hubs 1 to 4 and 11 to 13 employ the switching method described above, and the automatic switching function of duplicated VLAN routes (master-side VLAN route and slave-side VLAN route) is enabled. Specific processing contents will be described below with reference to FIGS. 2 to 5. FIG.

≪Overall processing contents≫
Based on FIG. 2, the overall processing contents of the switching method will be described. Here, it is assumed that the following information is entered in advance using commands before each of the PTP hubs 1 to 4 and 11 to 13 is started, and is written in the initial setting file F1.
・Route evaluation effective threshold D1
・Route evaluation allowance D2
・Switching determination threshold value D3
・Priority change number D4
S01: Processing is started by activation of PTP hubs 1-4 and 11-13. When the process is started, the PTP hubs 1 to 4 and 11 to 13 read the route evaluation effective threshold value D1, the route evaluation allowable value D2, the switching determination threshold value D3, and the priority change number D4 from the initial setting file F1, and set the respective values. After this activation, the PTP hubs 1 to 4 and 11 to 13 transition to either master state or slave state by normal PTP time synchronization processing.

S02-S06: Then, it is confirmed whether or not the PTP hubs 1-4 and 11-13 have transitioned to the master state (S02). As a result of the confirmation, if it is in the master state, the process proceeds to S04, and conventional PTP time synchronization processing is executed (S04).

On the other hand, if it is not in the master state, it is checked whether or not it has transitioned to the slave state (S03). As a result of confirmation, if the state has changed to the slave state, master/slave VLAN switching processing is executed (S05).

If it is not in the slave state, the confirmation of S02 and S03 is executed until it transitions to one of the master/slave states (S06) by the PTP time synchronization processing.

<<Details of master/slave VLAN switching process>>
The details of the master/slave VLAN switching process in S05 will be described with reference to FIG. The process of S05 is started when the PTP hubs 1-4, 11-13 receive the packet P, and is executed by the PTP hubs 1-4, 11-13.

S11: Processing is started, and it is confirmed whether or not the received packet P is a PTP packet. As a result of confirmation, if it is a PTP packet, the "VLAN_ID" of the transmission source of the received packet P is acquired. As a result, the VLAN number (VLAN_ID) to which the received packet P belongs is confirmed. It should be noted that if the received packet P is not a PTP packet, the processing ends.

S12: Confirm whether or not the "VLAN_ID" of the received packet P is the slave-side VLAN (secondary path). As a result of confirmation, if it is the slave side VLAN, the process proceeds to S13, while if it is not the slave side VLAN, the process proceeds to S21.

S13, S14: The priority change number (4096) D4 is added to the "VLAN_ID" of the received packet P, and the result is written and saved in the VLAN information D5 (S13). Also, it is checked whether or not the type of the received packet P is "announce message" (S14). As a result of the confirmation, if it is an "Announce message", the process proceeds to S23, and if not, the process proceeds to S15.

S15: Check whether the type of the received packet P is "Delay_Resp message". As a result of the confirmation, if it is "Delay_Resp message", the process proceeds to S16, and if not, the process proceeds to S19.

S16-S18: By referring to the master completion collection flag FL1 and the slave completion collection flag FL2, it is checked whether or not the collection of both the master side information (main path side information) and the slave side information (secondary path side information) has been completed (S16, S17).

Here, if both flags FL1 and FL2 are set, it is assumed that the collection has been completed, and the process proceeds to S26 after execution of the master VLAN switching determination process (S18). On the other hand, if both flags FL1 and FL2 are not set, the process proceeds to S26 without executing the master VLAN switching determination process (S18).

S19, S20: Check whether the type of the received packet P is "Sync message" (S19). As a result of the confirmation, if it is a "Sync message", the master/slave data collection process of S20 is executed to describe it in the slave collected data D6, and then the process proceeds to S26. On the other hand, if not, the process proceeds to S26 without executing the master/slave data information processing of S20.

S21: Confirm whether or not the type of the received packet P is "announce message". As a result of the confirmation, if it is an "Announce message", the process proceeds to S23, and if not, the process proceeds to S22.

S22: Check whether the type of the received packet P is "Delay_Resp message". As a result of the confirmation, if it is a "Delay_Resp message", the process proceeds to S16, and if not, the process proceeds to S24.

S23: Acquisition of master data, that is, acquisition of the master-side VLAN number (master-side VLAN_ID), description and storage in the VLAN information D5, and then proceeding to S18.

S24, S25: Confirm whether or not the type of the received packet P is "Sync message" (S24). As a result of confirmation, if it is a "Sync message", the master/slave data collection process of S25 is executed to describe it in the master collected data D7, and then the process proceeds to S26. On the other hand, if not, the process proceeds to S26 without executing the master/slave data information processing of S25.

S26: After executing conventional PTP time synchronization timer processing, the processing ends.

≪Master/slave data collection processing≫
Details of the master/slave data collection processing (S20, S25) shown in FIG. 4 will be described. Here, a predetermined number of "Meanpaths" for each of the master VLAN route (A route) and the slave VLAN route (B route) are stored.

The minimum value of the stored "Meanpath" group is obtained, and the number of "Meanpates" within the valid threshold from the minimum value is taken as the root evaluation value. Here, the number is set to 100 as an example.

S31: When the process is started, it is confirmed whether or not the VLAN information D5 of the received packet P is the master side VLAN. As a result of confirmation, if it is the master side VLAN, the process proceeds to S32, and if not, the process proceeds to S36.

S32: Referring to the master collection data D7, confirm whether or not 100 "Meanpaths" of the master-side VLAN are stored. As a result of confirmation, if 100 items are stored, the process proceeds to S33, otherwise, the process ends.

"Meanpath (passage time between PTP hubs)" is calculated as follows. That is, the elapsed time from the transmission port of the master PTP hub to the reception port of the slave PTP hub is obtained. The time obtained by subtracting the elapsed time in all the PTP hubs passed through from the elapsed time obtained here, that is, the transmission time _T1 between the master and the slave (outbound route) is calculated. Similarly, the transmission time T ₂ between the slave and the master (return path) is calculated, and the average value of the calculated transmission times T ₁ and T ₂ is defined as "Meanpath".

S33-S35: Find the minimum value in the group of 100 "Meanpaths", that is, the minimum "Meanpath" D8 (S33).

Also, among the 100 "Meanpath" groups, the number belonging to the root evaluation effective threshold D1 from the minimum "Meanpath" D8 is obtained as the A root evaluation value, and the A root evaluation value is described and stored in the master collection data D7 (S34). The A route evaluation value saved here is shown as D10 (see FIG. 5). After this storage, the master collection completion flag FL1 is set (S35), and the process ends.

S36: Referring to the slave collected data D6, it is confirmed whether or not 100 "Meanpaths" of the slave-side VLAN are stored. As a result of the confirmation, if 100 items are stored, the process proceeds to S37, and if not, the process ends.

S37-S39: Find the minimum value in the group of 100 "Meanpaths", that is, the minimum "Meanpath" D9 (S37).

In addition, the B root evaluation value is obtained from the minimum "Meanpath" D9 in the group of 100 "Meanpaths" and the number belonging to the root evaluation effective threshold value D1, and the B root evaluation value is described and saved in the slave collection data D6 (S38). The B route evaluation value saved here is shown as D11 (see FIG. 5). After this storage, the slave collection completion flag FL2 is set (S39), and the process ends.

<<Details of master/slave VLAN switching determination process>>
Details of the master/slave VLAN switching determination process (S18) will be described with reference to FIG. Here, when the A route evaluation value is smaller than the route evaluation allowable value D2, the difference between the A route and the B route is calculated. If the calculated route evaluation difference value (D12) is greater than the switching determination threshold value D3, routes A and B are switched.

S41: When the process starts, the A route evaluation value D10 and the B route evaluation value D11 are acquired from the master collected data D7 and the slave collected data D6 (S41).

S42: The A route evaluation value obtained in S41 is compared with the allowable route evaluation value D2 to confirm whether or not the A route evaluation value is small. As a result of the confirmation, if the A route evaluation value is smaller than the route evaluation allowable value D2, there is a possibility that a large delay has occurred on the A route, and the process proceeds to S43 to continue processing. On the other hand, if not, the delay of the A route is small, and there is no need to switch to the B route, so the processing ends.

S43, S44: Calculate the difference between the A route evaluation value and the B route evaluation value (S43). The route evaluation difference value D12 calculated here is compared with the switching determination threshold value D3 to confirm whether or not the route evaluation difference value D12 is greater than the switching determination threshold value (S44).

As a result of the confirmation, if the route evaluation difference value D12 is large, a clear delay improvement can be expected by switching to the B route, so the process advances to S45 to continue processing. On the other hand, if this is not the case, a clear delay improvement cannot be expected by switching to the B route, so the process is terminated.

S45: After switching between the master VLAN route (route A) and the slave VLAN route (route B), the master-side VLAN-related information (for example, VLAN information D5, master-collected data D7, master-collection completion flag FL1, etc.) and the slave-side VLAN-related information (for example, slave-collected data D6, slave-collection completion flag FL2, etc.) are exchanged, and the processing ends.

As described above, according to the communication path switching method (switching method) according to the present embodiment, since automatic switching between the master-side VLAN route and the slave-side VLAN route is incorporated into the PTP function, a VLAN route that is less affected by delay is always selected, and more accurate time synchronization can be realized. In particular, an automatic VLAN switching function is added to the PTP hub, and the following effects are obtained.

(1) In the case of the VLAN configuration of FIG. 1(b), that is, in the case of connection between single VLANs in which the PTP hubs 1 to 4 are made redundant, it can be used with the same setting as VLAN duplication. Further, if a VLAN 20 is added to each PTP hub and transmission/reception is performed between the PTP hubs using a tagged VLAN, a route with less delay is automatically selected, and high-precision time synchronization can be performed between the PTP hubs 1 to 4 while maintaining the redundancy function.

(2) Even in the case of the VLAN configuration of FIG. 1(d), that is, the PTP time synchronization VLAN duplex connection in which the PTP hubs 11 to 13 are made redundant for each VLAN, it can be used in the same manner as the case of FIG. 1(b).

For example, when VLAN10 is the master side route and VLAN20 is the slave side route, if the delay of VLAN10 becomes large, the route can be switched to VLAN20 through the processing of S41 to S45. This enables stable and highly accurate time synchronization among the PTP hubs 11-13.

(3) In the VLAN configurations shown in FIGS. 1(b) and 1(d), assume that the master-side VLAN route is disconnected and switching to the slave-side VLAN route occurs (in the case of FIG. 1(b), the use of VLAN 20 and tag VLAN is added). At this time, even if the previous master-side VLAN route recovers communication, there is no risk of switching back to the previous master-side VLAN unless the switching conditions of S41 to S45 are satisfied.

(4) After the route switching, as shown in S45, the VLAN-related information on the master side and the VLAN-related information on the slave side are exchanged. Therefore, the VLAN-related information can be used as before, so that S32 to S34 and S41 to S45 can be performed as before, which stabilizes the switching determination (S18).

(5) By rewriting the route evaluation effective threshold value D1, the route evaluation allowable value D2, and the switching determination threshold value D3, the conditions for route switching can be adjusted to be slow or slow, and flexible route switching according to the network configuration can be realized.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified and implemented within the scope described in each claim. For example, as for VLAN, not only port LAN but also tag LAN can perform the operations shown in FIGS. 2 to 5 without any problem.

1 to 4, 11 to 13...PTP hub 5 to 8, 16 to 19...hub

Claims (4)

A method of constructing a virtual LAN with switching hubs compatible with PTP (Precision Time Protocol) and switching redundant paths between the switching hubs when performing PTP time synchronization,
Collecting route transit time information between the master and slave executing the PTP time synchronization for both the main route and the secondary route between the switching hubs;
if the switching hub is in the slave state, switching between the main route and the secondary route based on the collected route transit time information;
storing a predetermined number of pieces of information on the route transit time for each of the routes;
obtaining the minimum value of the stored information group of each route transit time, and calculating the number of pieces within the effective threshold from the minimum value as the evaluation value of each route;
A communication route switching method, wherein the main route and the secondary route are switched based on the evaluation value. if the evaluation value of the main route is less than a predetermined evaluation tolerance, calculating the difference between the evaluation values of both routes;
2. The communication path switching system according to claim 1, wherein said main path and said secondary path are switched if said calculated difference value is greater than a predetermined threshold value. at the time of switching, all virtual LAN-related information including the evaluation value is exchanged between the two routes;
The VLAN-related information of the secondary path before switching is used as the VLAN-related information of the main path,
3. A communication path switching system according to claim 2 , wherein the VLAN-related information of the main path before switching is used as the VLAN-related information of the secondary path . A method of constructing a virtual LAN using switching hubs compatible with PTP (Precision Time Protocol) and switching redundant paths between the switching hubs when executing PTP time synchronization,
a step of collecting path transit time information between a master and a slave executing the PTP time synchronization for both the main path and the secondary path between the switching hubs;
if the switching hub is in the slave state, switching between the main route and the secondary route based on the collected route transit time information;
has
The switching step includes storing a predetermined number of pieces of information on the route transit time for each of the routes,
obtaining the minimum value of the stored information group of each route transit time, and calculating the number of pieces within the effective threshold from the minimum value as the evaluation value of each route;
A communication path switching method, comprising switching between the main path and the secondary path based on the evaluation value.

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