JPH0528542B2 - - Google Patents

Description

[Detailed Description of the Invention] [1] Technical Field The present invention is directed to determining how to grant transmission rights to nodes in an information network that connects a plurality of computers, terminal devices, etc. and communicates with each other. This paper relates to a network priority determination method.

[2] Prior Art In network equipment that connects various computers, terminal devices, etc. and transmits information between each other, and uses one or more lines in common, it is difficult to determine how to assign transmission rights to each node. There is a need for a method to decide whether to sequentially allocate them.

(called an access method) A frame determined by one of these access methods (called a free token) is circulated to each node in turn, and the node with a transmission request captures the token, changes it to a busy token, and then sends data There is a method of sending with a basket attached. (Token method) In the token method, various methods have been considered to prioritize transmission packets and give the opportunity to transmit high-priority packets as quickly as possible.
A typical example is the IEEE802.5 method. The outline is as follows.

(1) The token has a priority field (P) and a reservation field (B), and each node writes the values to Pr and Rr each time it receives a token.

(2) If the priority of the free token is P and the priority (Pm) of the node's transmission request packet is greater than or equal to Pm, change the free token to a busy token and transmit the data.

(3) After finishing sending the packet, this node outputs a free token, but at this time P and R
The value of is based on the following criteria.

(i) For (Pr)max((Rr)Pm) (P)=Pr(B)=max((Rr)Pm) (ii) (Pr)>max((Rr), Pm) (P)= max((Rr)Pm)(B)=0 Where, (Pr): Value of priority field register (indicates current priority) (Rr): Value of reserved field register Pm: Priority of transmission request packet P: Setting value of the priority field of the token to be transmitted R: Setting value of the reserved field of the token to be transmitted Here, 0 indicates the lowest priority.

(4) A node that changes the value of the priority field in the token from a small value to a large value stores the original value in stack Sr and the changed value in stack Sx. Each stack is prepared as many times as there are priority levels. This node is called a stacking station.

(5) When a node that becomes a stacking station confirms that no node has a packet with a priority higher than that of the network it outputs, it lowers the priority.The method for doing this is as follows.

When a free token with priority equal to Sx is received, (i) (Sr) (Rr), pops Sx, sends a token with P=(Sr)R=(Rr), and pops Sr. Once the contents of Sr are gone, the statking station will be released.

(ii) When Rr>Sr Pops Sx, sends a free token with P=(Rr)R=0, and stacks the value of (P) on Sx. (The stacking station will continue) (6) The reserved field will be updated under the following conditions.

(i) When the priority of the transmission request packet is lower than the priority of the network.

(ii) When the reserved field value (Rr) is lower than the priority value of the transmission request packet.

When transmitting a free token after transmitting a data packet, perform the following operations.

(i) When (Rr)≧(Rr) and (Rr)≧Pm, a comparator is used to output a free token of P=(Pr)R=max((Rr)Rm),
, to determine the values of P and R.

(ii) When (Pr)<max((Rr)Pm), a comparator for outputting free tokens with P=max((Rr)Pm) and R=0;
, and make a judgment to determine the values of P and R. At this time, the value (Pr) is stacked in Sr, and the value P is stacked in Sx.

[3] Problems with conventional technology The method described above has the following problems.

(i) Free token priority When a node outputs a free token with increased priority, the current network priority (Pr) is greater than the value of Rr, and if the value of Pm is greater than the free token with priority Pr. is output. Since (Rr) is lower than the value of (Pr) at this time, it is unlikely that there is a data packet with (Rr) greater than or equal to Pr at another node. Therefore, there is a high probability that this token will be returned to the node that output it and the operation will be performed to lower the priority.

When outputting free tokens (P) = max ((Rr),
Pm) priority reduces the amount of time that tokens are captured and traverses, increasing the efficiency of the entire network.

(ii) Change of priority For example, if the priority is changed in the order of 1 → 2 → 3 → 5, it is always necessary to lower it in steps of 5 → 3 → 2 → 1. This is because each stacking station lowers the priority by the amount it is responsible for raising. In this way, since the priority does not decrease from 5 to 1, if only a packet with a priority of 0 exists in the network, the time it takes for this packet to capture a free token that can be sent is approximately 3 times longer than when decreasing from 5 to 1. There will be a time difference of twice as much.

(iii) Each node requires a stack of (priority level) x 2, which complicates the hardware. In addition, the number of stacks that are constantly in operation is at most (priority level) x 2 in all networks, resulting in the provision of hardware that is hardly used.

[4] The purpose of the present invention is to solve the conventional problems, and to provide a priority control field (Pc) in the token and use it for both free tokens and busy tokens in the network. It is an object of the present invention to provide a priority determination method that reduces the number of priority bits in a frame by half and allows the priority to be changed in an extremely short time.

[5] Structure of the invention The configuration of the present invention will be explained below.

(1) Priority control field (Pc) during token
It is used to indicate network priority in the case of free tokens, and used to make reservations in the case of busy tokens.

(2) If the priority P of the free token is greater than the priority (Pm) of the node's transmission request packet, the data is transmitted using the free token as a busy token.

(3) After the packet transmission is completed, this node outputs a free token, and the value of (Pc) at this time is based on the following criteria.

However, Rr is the reserved value obtained by circulating the busy token, and the symbols have the same meanings as above.

(i) If the transmitted data packet exists in the node (Pc) = max (Pr, Pm) (ii) If the transmitted data packet does not exist in the node (Pc) = Pr (4) It is not remembered that the priority is not changed. Therefore, no stack is provided.

(5) The priority control field is updated with the busy token only when the priority of the transmission request packet is higher than the priority of the priority control field.

By adopting the above configuration, when a node outputs a free token, it is determined by the values of Pr and Pm, so it is more efficient than the conventional technology in which the stacking station has this function. Also, the time required to change the priority level is shortened, and a stack is not required, which simplifies the hardware. Also, since the priority control field can be used to indicate network priority and also be used for reservations, only half the number of bits in the frame are used than if each bit were occupied.

As is clear from the above explanation, in the present invention, a free token is created by a node leaving the queue of transmission request packets after writing the priority in the reservation field and transferring the priority value of the reservation field to the priority field. When a free token circulates around the network, if the priority of the transmission request packets of all nodes is lower than the priority of the token being circulated, a free token will continue to circulate without being captured, resulting in an unreasonable situation.

In such a case, the problem can be solved as follows.

(i) When a node outputs a free token, its value is stored in a register, and the contents of the register are reset when a busy token or a free token with a different priority is received. In order to prevent the register from being reset, if a free token with the same priority other than the lowest priority is received (Pm), if the node has a transmission request packet, the priority will be changed, and if there is no transmission request packet, the priority will be changed. is sent a new free token with the lowest priority.

(ii) One monitor node is provided in the network. (The method of determining the monitor is arbitrary.) The monitor node detects that a free token other than the one with the lowest priority has passed twice or more. The detection method includes, for example, incrementing the counter by 1 when a free token other than the lowest priority passes through the monitor node, and increasing the counter when a busy token passes or a free token other than the lowest priority passes. There is a method in which the counter is reset and the detection is made when the counter reaches a preset number of times (two or more times).

As soon as it is detected that a free token other than the lowest priority is around, the value of the priority control field of the free token is set to the priority if there is a transmission request packet in the monitor node as in (i), If there is no transmission request packet, a new free token with the lowest rank is transmitted.

[6] Example Figure 2 shows one of the typical conventional methods.
This is a block diagram showing the configuration method of the IEEE80.25 priority determination method.

In FIG. 2, three registers hold the latest token priority, reserved field value, and transmission request packet priority.

The comparator ~ compares the mutual sizes of the three registers and Stark Sr and Sx, and the priority control circuit determines (i) the values of Sr and Sx based on the output of the comparator and the token output timing signal (ii) Outputs a selection signal for determining the priority (P) of the token to be transmitted and the value of the reserved field (R).

The data selector selects the value of PR based on the selection signal of the priority control circuit. Sr and Sx have a stack structure, the depth of which matches the number of priority levels.

The operation when the stacking station lowers the priority of the network is as follows.

There is no data packet to be sent at the stacking station, or the comparator indicates that Pm<(Sx)
The priority (Pr) of the received free token is equal to (Sx) ((Pr) =
(Sx)) is determined by the comparator. When the comparator determines (i) (Sr) (Rr), it pops Sx, sends free tokens of R=(Sr), R=(Rr), and sends Sr. Pop.

(ii) If (Sr)<(Rr), transmit a free token with P=(Rr) and R=0, and stack the value of P on Sx. The value of the reserved field is updated by setting R=Pm when the comparator determines Rr<Rm and the comparator determines PmRr.

In the above, the PR and value are selected by the data selector as appropriate based on the output of the priority control circuit.

FIG. 1 shows an embodiment showing a specific configuration of the system of the present invention.

The registers ~ are comparators that hold the latest free token priority, busy token reserved field value, and send request packet priority, respectively, and the comparators compare the Pm value with the Pr and Rr values, respectively. The priority control circuit determines the priority of the token to be transmitted using the output of the comparator and the token output timing control signal.
The data selector outputting a selection signal for determining the values of the priority control field (P) and the reserved field (R) selects the priority control field (Pc) value in accordance with the selection signal of the priority control circuit.

When outputting a free token, check the output of the comparator, and if PmRr, set the value of Pm to Pm<
If it is Rr, control the data selector to output Rr and the value to Pc.

When a busy token is output, the priority control field (Pc) has two values: (i) the lowest priority is output (P ₀ ), and (ii) if the local node has a transmission request packet, its priority (Pm) is output. You can make a choice.

FIG. 3 shows an example of a conventional token frame, and FIG. 4 shows an example of a token frame of the present invention. As can be seen from both, in the case of the present invention, the capacity of the field for priority control is clearly half that of the conventional system.

[7] Effects Compared to the conventional method, the priority determination method of the present invention has a smaller number of comparators, the priority control circuit can be simplified, and the circuit configuration is significantly reduced considering that no stack is required. It can be seen that it can be reduced to Also, the number of bits used for priority control can be halved.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the method of the present invention. FIG. 2 is an example of a typical conventional method. FIG. 3 is a diagram illustrating a conventional token frame. FIG. 4 is an example of a token frame according to the present invention. 1, 11...Register, 2,12...Data selector, 3...Stack, 4...Stack, 5,
15... Comparator, 6, 16... Priority control circuit, Pc ₀ , Pc ₁ , Pc ₂ ... Priority control bit (3 bits), T... "1" in case of free token,
T...“0” for busy token, R ₀ , R ₁ , R ₂
... Reserved bits (3 bits), P ₀ , P ₁ , P ₂ ... Priority display bits (3 bits).

Claims (1)

[Claims] 1. Either a token indicating that transmission is possible (free token) or a token indicating that transmission is in progress (busy token) consisting of a specific bit string is circulated in a network consisting of a plurality of nodes, and each node In a token-ring network that grants transmission rights according to priority, a priority control field is provided in which a single priority can be written in the token, and a node that has a transmission request packet determines whether the priority of the transmission request packet is If the priority is higher than the priority written in the priority control field of the free token, the free token is captured, the lowest priority is written in the priority control field of the busy token, and it is sent to the network along with the transmission request packet. However, if the priority of the transmission request packet it owns is higher than the priority written in the priority control field of the circulating busy token, a node that has another transmission request packet changes the priority of the transmission request packet to that of the busy token. write to the priority control field,
When a node that has completed transmitting a packet first outputs a free token, it uses the reservation priority written in the priority control field of the busy token that circulated during packet transmission and the next request for transmission at that node. A network priority determination method that compares the priorities of existing packets and writes the higher one into the priority control field of a free token and sends it. 2. Network priority according to claim 1, characterized in that in a node having a transmission request packet, the priority of the packet is written in a priority control field of a busy token and sent to the network together with the packet. Decision method. 3 When it is confirmed that the free token output by a node has circulated around the network and returned to its own node, if there is a transmission request data packet in that node, the value of the priority control field in the token is changed to Claims 1 and 2 are characterized in that a free token is newly transmitted with the priority value of the transmission request data packet and, if there is no transmission request data packet, with the lowest priority. network prioritization method. 4. If a monitor node is set in the network and the monitor node detects that a free token other than the one with the lowest priority has circulated once or more,
If there is a transmission request packet from the own node, a free token with the priority of that packet, or
3. The network priority determination method according to claim 1, wherein if there is no transmission request packet from the own node, a free token with the lowest freshness level is newly transmitted.