JP7172721B2 - Frame transfer control method - Google Patents

Description

The present invention relates to techniques for controlling frame transfer delays.

A best-effort architecture such as Ethernet (registered trademark) has a low bandwidth cost, but has a weak mechanism for guaranteeing arrival reliability and transfer time characteristics (delay size and variation).

Reachability reliability has been a traditional issue for a long time. In recent years, time synchronization via Ethernet has been attempted, and improvement of transfer time characteristics has become important. Existing techniques for improving transfer time characteristics in Ethernet and the like include (1) flow control and (2) priority attachment "IEEE P802.1p".

However, while flow control can improve arrival reliability, it has a large negative effect on transfer time characteristics due to waiting for frame transfer, and cannot be a solution.

In addition, according to the method of adding priority, a high priority is added to frames that are strongly affected by arrival time characteristics (hereinafter referred to as time-sensitive frames), and preferential transfer is performed over other general traffic. , reduction in waiting time and suppression of fluctuations can be expected to some extent.

However, in Ethernet, as shown in FIG. 1, it is not possible to overtake the frame being output. That is, if another general frame is being output when the time-sensitive frame arrives, the time-sensitive frame cannot overtake the general frame being output and is forced to wait until the output is completed.

Especially in Ethernet, since the frame length is indefinite between 64 and 1518 octets, the output latency also fluctuates, which may adversely affect time synchronization. In order to solve such a problem, an interrupt control method and the like described in Patent Document 1 have been proposed.

JP 2017-169148

The interrupt control method of Patent Document 1 interrupts the current frame transmission by issuing an escape signal when a frame is being transmitted, and interrupts the transmission of a high-priority frame such as a time-sensitive frame.

According to this control method, although transfer time characteristics are greatly improved, compatibility with the existing Ethernet is lost. Also, since dedicated hardware is required, there is a risk of high costs.

SUMMARY OF THE INVENTION The present invention has been made to solve such conventional problems, and aims to enable preferential transfer of time-sensitive frames using existing equipment and suppress variations in transfer delay at low cost.

(1) One aspect of the present invention is a frame transfer control method when frame transmission/reception between terminals is relayed by a relay device,
When the source terminal transmits a time-sensitive frame that is strongly affected by arrival time characteristics to the destination terminal,
Transmitting a BPDU (Bridge Protocol Data Unit) frame as a BPDU signal via the relay device in advance,
After receiving the BPDU signal, the relay device puts the transfer port of the time-sensitive frame into a blocking state other than the BPDU;
A BPDU-encapsulated frame obtained by adding BPDU information to the time-sensitive frame is passed through the transfer port.

(2) Another aspect of the present invention is a frame transfer control method when frame transmission/reception between terminals is relayed by a relay device, comprising:
When the transmission source terminal transmits a time-sensitive frame that is strongly affected by the arrival time characteristics to the transmission destination terminal, the terminal transmits a BPDU (Bridge Protocol Data Unit) frame via the relay device in advance as a BPDU signal. sending as
a step of, after receiving the BPDU signal, placing the transfer port of the time-sensitive frame in a blocking state other than the BPDU;
and passing a BPDU-encapsulated frame obtained by adding BPDU information to the time-sensitive frame through the transfer port.

(3) Still another aspect of the present invention is a device for relaying time-sensitive frames strongly affected by arrival time characteristics between terminals,
If a BPDU signal composed of a frame of a BPDU (Bridge Protocol Data Unit) is received prior to the time-sensitive frame, setting a transfer port of the time-sensitive frame to a blocking state other than the BPDU;
A BPDU-encapsulated frame obtained by adding the BPDU information to the time-sensitive frame is passed through the transfer port.

According to the present invention, it is possible to preferentially transfer time-sensitive frames, and suppress variations in transfer delay at low cost.

FIG. 4 is an explanatory diagram showing the occurrence of transfer delay fluctuations in Ethernet; FIG. 4 is a conceptual diagram of a model case to which the frame transfer control method according to the embodiment of the present invention is applied; The schematic diagram which shows the time of transmission of the same BPDU signal. The schematic diagram which shows the state which relayed the same BPDU signal by the 1st BD switch. The schematic diagram which shows the state which relayed the same BPDU signal by the 2nd BD switch. FIG. 11 is a schematic diagram showing a state in which a third BD switch relays a reply of the BPDU signal; FIG. 4 is a schematic diagram showing transmission of the same BPDU-encapsulated frame; FIG. 4 is a schematic diagram showing a state in which the same BPDU-encapsulated frame is relayed by the second BD switch; FIG. 4 is a schematic diagram showing a state in which the same BPDU-encapsulated frame is relayed by a third BD switch; 4 is a schematic diagram showing a state after transmission of the same BPDU-encapsulated frame is completed; FIG. The block diagram of the same BD switch. Data configuration diagram of the same BPDU signal. FIG. 4 is a data configuration diagram of the same BPDU-encapsulated frame;

A frame transfer control system (method) according to an embodiment of the present invention will be described below. This control method mainly applies the infrastructure of the spanning tree protocol (STP).

This STP is defined in IEEE 802.1D as a route control protocol for preventing infinite circulation of frames on a loop by automatically detecting a loop and blocking one point on the loop on a layer 2 network.

Specifically, one bridge on the network is selected as the root, the shortest route from a node other than the root to the root is calculated, and paths not included in the shortest route are regarded as redundant routes and cut off.

At that time, a dedicated Ethernet frame called "BPDU (Bridge Protocol Data Unit)" is used to exchange route information between bridges. This "BPDU" can pass through blocked paths as well.

In the control method, a switching hub (hereinafter referred to as a switch) is applied to a dedicated Internet frame of 'BPDU' to temporarily occupy a transfer path, that is, a transfer port when a time-sensitive frame passes through. As a result, time-sensitive frames can be preferentially transferred, and it is possible to suppress the occurrence of transfer delay fluctuations and at the same time ensure arrival reliability.

In addition, the control method can also be called "BPDU signaling" in that signaling is performed using a dedicated Ethernet frame of "BPDU", and a switch that executes this is called a "BS switch". do.

≪Network configuration≫
A model case of the control method will be described with reference to FIG. Although FIG. 2 exemplifies a relatively simple network configuration, any network configuration in which frame transmission/reception between terminals is relayed by a relay device such as a switch is similarly applied.

An application using the time-sensitive frame F1 is executed between the terminals 11 and 12 in FIG. 2, and the time-sensitive frame F1 is transmitted/received via (relayed) the BS switches 1a to 1c.

For example, PTP (Precision Time Protocol) time synchronization is performed between terminals 11 and 12, and messages for time synchronization (synchronization message, delay request message, delay response message, etc.) are exchanged between terminals 11 and 12. be done.

Terminals 13-15, on the other hand, are running general applications that are not time sensitive. Here, the general frame F2 is transmitted and received instead of the time-sensitive frame F1, thereby consuming a large amount of bandwidth.

In particular, since the sizes of general frames are not uniform, the transfer delay of the time-sensitive frame F1 fluctuates as described above, which may adversely affect time-sensitive applications (such as PTP time synchronization).

Arrows R1 to R4 in FIG. 2 indicate routes for transmitting the general frame F2 from the terminal 13 to the terminal 15 via the BS switches 1a to 1c. The arrows r1 to r3 indicate routes for transmitting the general frame F2 from the terminal 14 to the terminal 15 via the BS switches b1 and 1c.

<Transition of Signaling>
The transition of the signaling of the control method will be explained with reference to FIGS. 3 to 6. FIG. Here, P1 to P5 in each figure indicate the ports of the BS switches 1a to 1c, "FWD" indicated on the ports P1 to P5 indicates the forwarding state, and "BLK" indicates the blocking state.

(1) First, as shown in FIG. 3, when transmitting the time-sensitive frame F1 from the terminal 11 to the terminal 12, a BPDU signal S is transmitted in advance. That is, the BPDU signal S is transmitted prior to the time-sensitive frame F1, and the time-sensitive frame F1 is not transmitted during the transmission of the BPDU signal S.

The transmission of this BPDU signal S is performed for each entry of each time-sensitive frame F1 (for each BPDU signaling entry). 2 to 10 show only the transmission from the terminal 11, the same applies to the transmission from the terminal 12. FIG.

Specifically, the BPDU signal S is configured based on an Ethernet frame, and as shown in FIG.
(A) Protocol ID
(B) Protocol version ID
(C) BPDU type (D) Flag (E) Session ID
(F) source MAC address (G) destination MAC address (H) pass count (I) timer fields are added.

Table 1 shows the details of each field (A)-(I). Here, it is assumed that the terminal 11 sets the "calling bit" in the flag field and transmits. A unique identification number is assigned to the session ID within the terminal 11, and is used to identify multiple entries of BPDU signaling.

The transmission of the BPDU signal S from the terminal 11 is transferred to the terminal 12 in the order of "BS switch 1a→1b→1c".

(2) Next, when the BS switch 1a receives the BPDU signal S from the terminal 11, as shown in FIG. state.

Therefore, as indicated by arrow R1, when general frame F2 is received from terminal 13, it cannot be transferred from transfer port P1 to BS switch 1b. On the other hand, the BS switch 1a transfers the BPDU signal S from the transfer port P1 to the BS switch 1b in the STP blocking state.

(3) Also, as shown in FIG. 5, when the BS switch 1b receives the BPDU signal S at the port P2, it sets the transfer port P3 of the time-sensitive frame F1 to the STP blocking state.

Therefore, as indicated by arrow r1, when general frame F2 is received from terminal 14, it cannot be transferred from transfer port P3 to BS switch 1c. On the other hand, the BS switch 1b transfers the BPDU signal S from the transfer port P3 to the BS switch 1c in the STP blocking state.

(4) Further, the BS switch 1c sets the forwarding port P5 of the time-sensitive frame F1 to the STP blocking state after receiving the BPDU signal S at the port P4, as shown in FIG.

As a result, all of the transfer ports P1, P3, and P5 from the terminal 11 to the terminal 12 are set to the STP blocking state, and frames other than BPDU cannot pass through. In this sense, the state in which there is no frame being output to the transfer ports P1, P3, and P5 is completed.

After that, the BS switch 1c transmits a BPDU signal S to the terminal 12. FIG. Upon receiving this BPDU signal S, the terminal 12 returns the BPDU signal S as indicated by an arrow L when answering the call from the terminal 11 .

At this time, the ACK bit is set in the flag field of the BPDU signal S to indicate that it is a reply, thereby preventing the BPDU signal from playing catch. The reply of the BPDU signal S from the terminal 12 is transferred to the terminal 11 in the order of BS switch 1c→1b→1a.

≪Transfer of time-sensitive frames≫
(1) Transfer of the time-sensitive frame F1 will be explained with reference to FIGS. 7 to 10. FIG. Here, as shown in FIG. 7, the terminal 11 BPDU-encapsulates the time-sensitive frame F1 and transmits it to the BS bridge 1a.

It is preferable that this transmission be performed after receiving the reply indicated by the arrow L and confirming the STP blocking status of the transfer ports P1, P3, and P5. The encapsulated time-sensitive frame F1 is called BPDU-encapsulated frame C herein. This frame C, as shown in FIG. 13, includes (A) protocol ID in the time-sensitive frame F1.
(B) Protocol version ID
(C) BPDU type (D) Flag (E) Session ID
field has been added. As a result, BPDU information and the like are added to the BPDU-encapsulated frame C, and the BPDU-encapsulated frame looks like a BPDU. The above fields are synonymous with those in Table 1.

(2) The BPDU-encapsulated frame C is apparently a BPDU, passes through the blocking forwarding port P1 of the BS switch 1a, and is received at the port P2 of the BS switch 1b, as indicated by the arrow X1 in FIG. be.

Similarly, BPDU-encapsulated frame C passes through blocking transfer port P3 of BS switch 1b and is received at port P4 of BS switch 1c, as indicated by arrow X2 in FIG. The BPDU-encapsulated frame C received here passes through the blocking transfer port P5 of the BS switch 1c and reaches the terminal 12, as indicated by the arrow X3 in FIG.

As described above, according to the control method, the BPDU-encapsulated frame C can be transferred from the terminal 11 to the terminal 12 while the transfer ports P1, P3, and P5 are blocked. As a result, the time-sensitive frame F1 is not kept waiting until the output of the general frame F2 is completed, and preferential transfer of the time-sensitive frame F1 is realized.

At this time, as shown in FIGS. 8 to 10, after the BPDU-encapsulated frame C has passed through each of the ports P1, P3, and P5, the respective blocking states are canceled and the passage of the general frame F2 is permitted.

Therefore, after releasing the blocking state, it becomes possible to send the general frame F2 from the terminal 13 to the terminal 15 as indicated by the arrows R1 to R4. It is also possible to send the general frame F2 from the terminal 14 to the terminal 15 as indicated by arrows r1 to r3.

≪Structure of BS switch≫
A configuration example of the BS switches 1a to 1c will be described with reference to FIG. Each of the BS switches 1a-1c has a switch engine 2, ports 3 (corresponding to ports P1-P5 in FIGS. 2-10), and an FDB table (MAC address table) 4, like a general switch. there is

This port 3 has a state called port state, as indicated by an arrow Q. FIG. If this port state is forwarding, all frames can pass. On the other hand, if the port state is blocking, only BPDUs can pass.

Furthermore, the BS switches 1a to 1c include a BPDU signaling processing unit 6 that monitors the BPDU signal S, an SIB (signal information base) 7 that records information on the BPDU signal monitored by the signaling processing unit, and a destination MAC address of the entry. and a set value DB 5 for storing user allocation in the case of multicast.

<<Example of operation of BS switches 1a to 1c>>
Main operations of the BS switches 1a to 1c will be described below based on the network configurations shown in FIGS. 2 to 10. FIG.

(1) Signal processing The BS switches 1a to 1c that have received the call origination of the BPDU signal S process the "session ID", "source MAC address", "destination MAC address", "pass count", and "session ID" of the BPDU signal S. Reads the "timer" information. The read information is recorded in the SIB 7 for each BPDU signal S and registered as an entry.

(2) Port Blocking The BS switches 1a-1c perform the following operations for each entry registered in the SIB7. Here, the operation of the BS switch 1a will be described as an example.

First, if the transmission destination MAC address of the entry is a unicast address, the BS switch 1a refers to the FDB 4 to determine the transfer port P1 of the corresponding address, and puts the determined transfer port P1 in the blocking state.

On the other hand, if the transmission destination MAC address of the entry is multicast, the target transfer port P1 is determined according to the setting value 5, and the determined transfer port P1 is placed in the blocking state. However, since port blocking is performed for each entry, the blocking state in the BS switch 1a is not limited to the forwarding port P1.

After that, the BS switch 1a transfers the call of the BPDU signal S from the identified transfer port P1. The BS switch 1b that has received this transfer also performs the above-described signal processing and port blocking operations. This chain of operations blocks all of the transfer ports P1, P3 and P5 on the transfer path and eliminates the frame being output.

As a result, priority transfer of the time-sensitive frame F1 and fluctuations in transfer delay can be suppressed using only the STP port state for the widely used spanning tree without requiring special hardware. Contribute to cost reduction.

(3) Signal Reply The BS switches 1a to 1c that have received the BPDU signal S reply from the terminal 12 forward the signal reply to the terminal 11 in order. At this time, since the MAC address of the terminal 11 is described in the BPDU signal S, the transfer port (ports P4 and P2 in FIGS. 2 to 10) can be determined by referring to the FDB4.

(4) Transfer of BPDU-encapsulated frame Since the BPDU-encapsulated frame C is apparently BPDU, each of the BS switches 1a to 1c passes through the blocking ports P1, P3, and P5 and transfers it to the destination terminal 12 (switch engine 2). is also enabled for hardware forwarding instead of BPDU trapping).

(5) Monitoring of BPDU-encapsulated frame The BPDU-encapsulated frame C is transferred by the CPUs in the BS switches 1a to 1c, and subjected to the following monitoring processing by the signaling processing unit 6. FIG.

First, the SIB 7 is searched using the source MAC address, the destination MAC address, and the session ID of the BPDU-encapsulated frame C as keys, and an entry of the BPDU signal S having the same information is obtained from the SIB 7 .

Next, the BS switches 1a to 1c subtract "1" from the pass count value of the entry. As a result of the subtraction, when the pass count value becomes "0", the blocking state of the transfer ports P1, P3, P5 corresponding to the entry is canceled and the entry is deleted. If not, keep the blocking state.

Therefore, for the same entry, it is possible to preferentially transmit the number of BPDU-encapsulated frames C described in the path count. In particular, there is no need to repeatedly maintain and release blocking for each individual BPDU, thus improving efficiency.

(6) Entry aging The BS switches 1a to 1c periodically scan their own SIB 7, and set the timer of each entry (effective time of BPDU signal S/effective time of blocking state) from the time when the BPDU signal S is received. Subtract according to elapsed time.

At this time, the transfer ports P1, P3, and P5 corresponding to the entry are maintained in the blocking state until the timer times out. Therefore, for the same entry, multiple BPDU-encapsulated frames C can be preferentially transmitted until the time expires. On the other hand, when the timer times out, the blocking state of the transfer ports P1, P3, P5 is released and the entry is deleted from the SIB7.

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, the pass count and timer fields of the BPDU signal S are not essential and need not be described.

In this case, although the aforementioned effects of monitoring and entry aging cannot be obtained, it is possible to obtain the effects of preferential transfer of the time-sensitive frame F1 and suppression of fluctuations in transfer delay.

1a to 1c ... BS switch (relay device)
2 Switch engine 3 (P1, P2, P3) Port 4 FDB
5... Setting value 6... BPDU signaling processing unit 7... SIB
11 to 15... terminal

Claims (5)

A frame transfer control method when frame transmission/reception between terminals is relayed by a relay device,
When the source terminal transmits a time-sensitive frame that is strongly affected by arrival time characteristics to the destination terminal,
Transmitting a BPDU (Bridge Protocol Data Unit) frame as a BPDU signal via the relay device in advance,
After receiving the BPDU signal, the relay device puts the transfer port of the time -sensitive frame into a blocking state other than the BPDU;
passing a BPDU-encapsulated frame obtained by adding BPDU information to the time-sensitive frame through the transfer port;
A control method for frame transfer, wherein the destination terminal sends a reply to the source terminal after receiving the BPDU signal. 2. The frame forwarding control system according to claim 1, wherein said blocking state is released when said BPDU-encapsulated frame passes through said forwarding port. The terminal of the transmission source sets a calling bit and a unique identification number within the terminal in the BPDU signal and transmits the signal,
2. The frame transfer control system according to claim 1, wherein said destination terminal sets an incoming call bit in said BPDU signal and returns it. The BPDU signal includes the number of BPDU-encapsulated frames passed through the transfer port as a pass count,
each of the relay devices includes a signal information storage unit that stores the path count information after receiving the BPDU signal;
subtracting "1" from the value of the pass count each time the BPDU-encapsulated frame passes;
3. The frame transfer control system according to claim 2, wherein said blocking state is released when said pass count value becomes "0". While the BPDU signal includes the valid time of the blocking state,
The relay device includes a signal information storage unit that stores the valid time after receiving the BPDU signal,
4. The frame transfer control system according to claim 1, wherein the blocking state of the transfer port is released after the valid time has elapsed.

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