JPH0528541B2 - - Google Patents

Description

[Detailed Description of the Invention] [1] Technical Field The present invention connects various computers, terminal devices, etc., and determines the priority of terminals for transmitting information in a network that mutually transmits information, thereby achieving the shortest waiting time. This paper relates to a network priority determination method for time-efficient network operation.

[2] Background technology 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 (called an access method) to decide whether to sequentially grant the access information to the access points. One of these access methods is a method in which a predetermined frame (called a free token) is circulated to each node in turn, and the node requesting transmission captures the token, changes it to a busy token, and then sends it with a data packet attached. There is (token method). For example, the IEEE Committee No. 802 draft dated September 23, 1983, “Draft IEEE Standard 802, 5.
Token Ring Access Method and Physical
As seen in ``Layer Specifications,'' the token method prioritizes transmitted packets,
A method has been devised to provide an opportunity to transmit high-priority packets as quickly as possible, and an outline of this method will be explained below.

(1) The token has a priority field (P) and a reservation field (R), 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 P, 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) When (Pr)≧max((Rr)pm) (P)=Pr (R)=max((Rr)Pm) (ii) (Pr)<max((Rr), Pm) (P) = max ((Rr), Pm), (R) = O where (Pr): Value of the priority field register (indicates the current priority) (Rr): Value of the reserved field register Pm: Value of the transmission request packet Priority 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 "O" 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 the node that becomes the 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 is as follows.

When receiving a free token with priority equal to Sx, (i) If (Sr) ≧ (Rr), pop Sx, send tokens with P = (Sr), (R) = (Rr), and pop Sr. . Once the contents of Sr are gone, the statking station will be released.

(ii) When Rr>Sr, pop Sx and send a free token with P=(Rr) and R=O, and the value of (P) is stacked 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.

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

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

(i) If (Pr)≧(Rr) and (Pr)≧Pm, then P=
In order to output a free token of (Pr)R=max((Rr)Pm), a comparator is used to make a judgment and determine the values of P and R.

(ii) When (Pr)<max((Rr)Pm), a comparator is used to output a free token with P=max((Rr), Pm) and R=O.
is used to make a judgment and 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 above-mentioned conventional technology has the following problems.

(i) Free token priority When a node outputs a free token with increased priority, if the current network priority (Pr) is greater than the value of Rr or Rm, the free token with priority Pr is output.

If (Rr) is lower than the value of (Pr), it is unlikely that other nodes have data packets with a priority higher than Pr. 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 spend circulating without being captured, increasing the efficiency of the entire network.

(ii) Waiting time when the priority is changed For example, if the priority is changed in the order of 1 → 2 → 3 → 5, these changes will result in each stacking station raising the priority by one step. Therefore, if you try to lower the token whose priority is currently 5 to 1, the priority will be 5 →
It will not go down to 1 unless you go through steps 3 → 2. Therefore, it is not possible to change the priority from 5 to 1, so if only a packet with a priority of 1 currently exists in the network, the waiting time until this packet acquires a free token that can be sent is the same as changing the priority from 5 to 1. This means that it will take about three times as much time as it would take if the changes could be made all at once.

[4] Purpose of the invention The present invention is intended to solve the problems of the conventional method described above. When a node outputs a free token, its priority is determined from the values of Rr and Pm. The priority can be changed immediately, thus eliminating the need for the stacking station to maintain its functionality and significantly reducing the time for priority changes and waiting for free token output.

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

(1) The token has a priority field (P) and a reservation field (R), 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 higher than that, the data is transmitted using the free token as a busy token.

(3) After completing the packet transmission, this node outputs a free token, at which time the values of P and R are based on the following criteria.

(i) When the transmit data packet remains in the queue (P)=max((Rr), Pm) (R)=O (ii) When the transmit data packet does not exist in the queue (P)=Rr (R)=O ( (Each symbol has the same meaning as above) (4) No stack is provided (changes in priority are not remembered) (5) Reserved fields are 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 of the transmission request packet.

In (i) of Section 3 above, if a transmission data packet remains in the queue, it is also possible to set the criteria for P and R as follows.

(P) = max ((Rr), Pm) (R) = min ((Rr), Pm) If the values of P and R are set according to this criterion, information from past token cycles will remain in the reserved bits. This has the advantage of reducing the number of times the reserved field is written.

Furthermore, in the network priority determination method of the present invention as described above, if a node leaves the queue of transmission request packets after writing the priority in the reservation field, the priority of the reservation field is set as the priority. When a free token transferred to the field circulates, if any node has only low-priority transmission request packets, it will not be able to capture the free token, which makes it unreasonable for the free token to circulate. In order to solve such problems, the following two methods can be considered.

(1) Method under the control of the node that sent the free token When a node outputs a free token, it stores its value in a register, and the contents of that register are changed when it receives a busy token or a free token with a different priority. Reset. If a free token with the same priority other than the lowest priority is received before the register is reset, and the value of the priority (Pm) of the transmission request packet is smaller than the priority of the free token, A new free token is transmitted with the priority field value set to the higher value of the value of the reserved field of this free token and the priority value of the transmission request packet, and the value of the reserved field set to the lowest value. In this way, it is possible to prevent free tokens other than the lowest priority from continuing to circulate and packets from other nodes having lower priority to be placed on the waiting list for transmission.

(2) Method using a monitor node 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. For example, if a free token other than the lowest priority passes through the monitor node, the counter is incremented by one, and if a busy token passes or a free token other than the lowest priority passes, the counter is incremented by one. The counter shall be reset, and the counter shall be reset a preset number of times (two or more times).
There is a method that detects the condition even when the condition has changed.

When it is detected that a free token other than the one with the lowest priority is circulating, it immediately changes the priority field of the free token to the value of the reserved field and the priority value of the monitor node's transmission request packet, as in (i). Compare and set the higher value as the priority field value, and send a new free token with the reserved field value as the lowest value.

[6] Embodiment FIG. 2 is a block diagram showing the configuration of the priority determination method described in IEEE802.5, which is an example of the prior art.

In FIG. 2, three registers 1 hold the latest token priority, reserved field value, and transmission request packet priority.
The six comparators 5 compare the mutual sizes of the three registers 1 and Starks 3 and 4, and the priority control circuit 6 uses the output of the comparators 5 and the token output timing signal to (i) (ii) outputting 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 2 selects the values of P and R based on the selection signal from the priority control circuit 6. Sr and Sx have a stack structure, the depth of which matches the number of priority levels.

Next, the operation when the stacking station lowers the priority of the network will be explained.

Are there no data packets being sent at the stacking station? Also, with a comparator, 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), pops Sx, sends free tokens of P = (Sr), R = (Rr), and pops Sr. do.

(ii) If (Sr)<(Rr), transmit a free token with P=(Rr) and R=O, and stack the value of P on Sx.

The value of the reserved field is Rr in the comparator
<Determine Pm and use the comparator to determine Pm
When Rr is determined, it is updated by setting R=Pm.

In the above, the values of P and R are selected by the data selector 2 as appropriate based on the output of the priority control circuit.

FIG. 1 shows a specific example of the configuration of the system of the present invention. The registers 11 each hold the latest token priority, reserved field value, and transmission request packet priority.

The comparators 15 compare the values of Pm with the values of Pr and Rr, and the priority control circuit 16 determines the priority (P) of the token to be transmitted and the reservation based on the output of the comparator 15 and the token output timing control signal. Outputs a selection signal for determining the value of field (R). The data selector 12 selects the values of P and R based on the selection signal from the priority control circuit 16.

When outputting a free token, check the output of the second comparator and if it is PmRr, Pm
If Rr<Pm, the first data selector is controlled to output the value of Rr to P.

At the same time, the second data selector is controlled,
Determine the value of R.

And: When Rm≧Rr, output Rr, and when Pm<Rr, output the value of Rm to R. (The algorithm that sets the value of R to the lowest value outputs R=O.) In the case of a busy token, the value of Pr is output as is to P, and if Pm>Rr, Pm,
If PmRr, output Rr.

Comparing the method of the present invention with the conventional method, it was found that the number of comparators is small, the priority control circuit can be simplified, and no stack is required.The present invention greatly simplifies the circuit configuration. You can see that

[7] Effects According to the method of the present invention detailed above, when a node outputs a free token, the priority is immediately raised or lowered based on the values of Rr and Pm. Compared to a stacking station with this function, the time required to change priorities is shortened, and at the same time, the hardware is simplified by eliminating the need for stacking.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the configuration of the system of the present invention. FIG. 2 is a diagram showing the configuration of a conventional system. 1, 11... Register, 2, 12... Data selector, 3, 4... Stark, 5, 15... Comparator, 6, 16... Priority control circuit.

Claims (1)

[Claims] 1. A priority field for controlling priority and a reservation field for reserving transmission are provided in a token consisting of a specific bit string, and a token consisting of a specific bit string is provided with By circulating a string of data packets with a token indicating possible transmission (free token) or a token indicating transmission in progress (busy token), each node rewrites the priority stored in the priority field and reservation field in the token. In a token ring network that gives each node the right to transmit according to its priority, when the node that captured the free token and sent the busy token and packet next outputs the free token, Compare the value written in the reserved field of the circulating busy token with the priority of the next packet requested to be transmitted at the node, write whichever is higher in the priority field of the free token, and A network priority determination method characterized by writing the lowest priority in the free token reservation field. 2. When a node outputs a free token after completing a packet transmission, it uses the value written in the reserved field of the busy token that circulated during the packet transmission and the priority of the next packet that the node is requesting to transmit. 2. The network priority determination method according to claim 1, wherein the lower one of the two is written in a reserved field of a free token. 3 When it is confirmed that the free token output by the node has circulated around the network and returned to its own node, it sets the value of the reservation field of this free token and the priority value of the transmission request packet of its own node. Network priority according to claims 1 and 2, characterized in that a new free token is transmitted with the higher value compared as the priority and the lower value as the reserved field value. degree determination method. 4 One monitor node is determined in the network, and when this monitor node detects that a free token other than the lowest priority has circulated once or more, it sends the value of the reserved field and the monitor node's transmission request packet. The network according to Claims 1 and 2, characterized in that the priority field is compared with the priority value of , the higher value is set as the value of the priority field, and the reserved field is set as the lowest priority value. Work priority determination method.