KR950015084B1 - Control unit and method of fast access to mechi using ring - Google Patents

Abstract

The apparatus for providing equitable opportunity of access to a number of nodes connected to ring of LAN or MAN, includes: a cell receiver(23) connected to single ring of which slot with continuous linked length is rotated or double ring of which slots are rotated in reverse direction each other; a cell transmitter(24) transmitting a number of priority cells; and a token processor(25) controlling flow of window token.

Description

High speed media access control device and method using ring

1 is a double ring configuration to which the present invention is applied

Fig. 2A is a block diagram of an access unit in the double ring configuration.

Fig. 2B is a block diagram showing the configuration of the access unit in the single ring configuration.

3 is a block diagram of a cell transmitter and a token processor having three levels of priority.

4 is a structural block diagram of a cell rotating a ring.

5 is a flowchart of a cell transmission method for each priority in the case of having three levels of priority.

6 is a flowchart showing an operation when a window token arrives.

Local Area Networks (LAN) or Metropolitan Area Networks (MAN) using shared transmission media in a ring form provide fair access opportunities to multiple nodes connected to the ring, and at the same time A high speed medium access control apparatus and method for providing a plurality of priority access control functions to satisfy a quality of service.

Conventional protocols having a double ring type include Asynchronous Transfer Mode Ring (ATMR) and Metaring. In order to realize fairness and priority control, ATMR uses periodic reset and Metaring uses SAT (SATisfy) control signal. In case of using periodic reset, fairness is maintained between nodes by assigning a quota indicating the number of cells that can be transmitted to the nodes whenever a reset occurs. This method must check whether all nodes have used all their quotas and generate a new reset, so the idle time between the two successive reset cycles does not use the bandwidth of the ring during the determination of the end of the cycle. This will occur. This idle time is increased in proportion to the delay of the ring, so that the throughput of the network becomes sensitive to the delay of the ring. Even in priority control, if a high priority cell is not transmitted within a specified time to limit the maximum transfer delay of high priority information within a certain time, an interrupt relet is generated to prohibit the transmission of a low priority cell. When all of these have been sent, a normal reset will occur again, allowing all priority cells to be sent. The priority control scheme of ATMR applies a short reset period to a high priority cell to limit the maximum propagation delay to within a predetermined value. As a result, the frequency of reset is increased to decrease the utilization rate of a transmission medium.

In metaring, the SAT control signal is rotated in the opposite direction to the slot transfer direction. When the SAT passes through a node, it assigns a maximum and minimum quota to it. A node with a cell to transmit may transmit up to Qu-quota cells, and when the SAT returns by rotating the ring, the remaining cell to send remains and if the Min-quota value is greater than zero, then the minimum The pass of the SAT is suspended until the quota value becomes zero or there are no cells left to transmit. If there is no cell to send or if the quota is used up, it passes the SAT and is assigned a new quota (Min-quota, Max-quota), and if both the cell and the quota (Min-quota) remain, Suspend the passing of the SAT until all quotas are used up. In this method, since the SAT continuously rotates the ring and allocates new quotas to the nodes, the use of the transmission medium is high because there is less wasted bandwidth than the reset method. Priority control is given to the SAT, and each node has higher priority data than the SAT at the moment the SAT passes, transmits the SAT with higher priority, and the node receiving the SAT is lower than the SAT. Priority data cannot be transmitted. This way, the higher priority SAT can be changed back to its original priority by at least one rotation of the ring.

In order to reduce the priority of the SAT to its original priority, the priority control method based on the intermittent priority change of the SAT is proportional to the delay of the ring since the data of the same or higher priority of the SAT must not remain. There is a disadvantage in that the overhead is generated and the utilization rate of the medium is lowered.

The present invention provides a fair access opportunity according to priorities to nodes while minimizing bandwidth loss of a transmission medium even in a ring type network in which data is divided into cells having a predetermined length and transmitted at a speed of 1 gigabit per second or more. It is an object of the present invention to provide a priority control method capable of preferentially transmitting high priority data to limit the maximum access delay of a high priority within a predetermined value.

The present invention relates to a medium control protocol applied to a single ring in which a continuous slot of a certain length rotates in opposite directions as shown in FIG. 1 or a single ring in which a continuous slot rotates. ) Provides a fair access opportunity, and when the data to be delivered is divided into several priorities, the utilization rate of the transmission medium is significantly increased compared to the conventional method in the method of preferentially delivering high priority data. .

In the present invention, a plurality of window tokens, one assigned to each priority, rotate the ring at the same time, each time the window token passes through the node, a quota is assigned to the priority, and the node is assigned while the window token rotates the ring. The nodes are provided with fair access opportunities by transmitting the number of quota cells. Quota refers to the number of cells that Windows Token can transmit while rotating the ring, and the size of the quota depends on the size of the data to be transmitted. In order for a cell in the transmission queue of priority k to be transmitted, all priorities higher than k cannot transmit the cell, and the ring rotation time of all priority window tokens higher than k must be within the specified value. Quota of rank k must remain. In addition, in order to pass the node of the window token of priority k, no quota remains for each priority higher than k, or there are no cells to transmit in the transmission queue of priority, and windows of all priority higher than k. Token rotation time must be within the specified value. Therefore, in the present invention, the ring rotation time of each priority window token is proportional to the magnitude of the load equal to or higher than the corresponding priority applied to the network.

In this multi-token priority control method, the transmission of priority media lower than k is stopped only in nodes where priority k window tokens do not arrive within a specified time, that is, in the network, so that the utilization rate of transmission medium is significantly lower than that of ATMR or metraring. Is reduced. In addition, since the number of quotas of cells allocated when the window token of priority k passes through the node is guaranteed to be transmitted while the window token of priority k is rotated one time, the window token's rotation time is limited to a certain value. The maximum transmission delay of the cell can be limited within a certain time.

As an embodiment of the present invention, a media access control method having three levels of priority will be described.

1 shows a configuration of a network to which the present invention is applied. That is, the present invention is applied in principle to an enemy applied to a network in which a plurality of nodes are connected to a double ring in which slots of a predetermined length rotate in opposite directions, and can also be applied to a single ring.

2 shows the configuration of a node. The node connected to the double ring has two access units 21 and 22 transmitting and receiving to and from a cell in each of the two rings as shown in FIG. 2A, and the two access units operate independently. When the present invention is applied to a single ring, the node is composed of one access unit 26 as shown in FIG. 2B. When the access unit arrives at the slot in which the cell is loaded, the node looks at the header area of the cell and the destination of the cell is its own. When the cell transmitter 24 transmits a cell in the transmission queue of the highest priority having a window counter value greater than 0 and decreases the window counter of the priority by one, the window token of priority k arrives. If there is a cell in the transmission queue for all priorities equal to or higher than k and there is at least one priority with a window counter value greater than zero, the window token is suspended. If the pass condition of the window token is satisfied, the window token is opened. Pass through and the token processing unit 25 for allocating quotas to the window counter.

3 shows the configuration of a slot for rotating the ring. The slot includes an access control area 31 including a bit for transmitting a window token for allocating a quota to an access unit and a monitor bit for detecting a cell that rotates the ring indefinitely, and data and data for exchanging data in a cell transmitter. It consists of an information area 32 containing an address representing the destination of.

4 is a block diagram showing the structure of a cell transmitter and a token processor. The cell transmitting unit transmits a transmission queue 42 for storing cells to be transmitted by priority, a cell transmitter 41 for loading cells stored in the transmission queue into empty slots, whether cells are to be transmitted, and cells of any priority. It consists of the transmission controller 43 which determines whether it is. The token processing unit divides the window token received from the ring B by priority and stores it in the token buffer, and the token buffer 40 temporarily stores the window token until the pass condition of the window token for each priority is satisfied. If the window token of the corresponding priority passes, the quota value is assigned and the window counter 48 decrements each time the cell of the priority is transmitted.The value is initialized to 0 each time the window token passes. Token timer 47 that increases in value as the elapsed time, token rotation time buffer 46 for storing the token timer value immediately before it is initialized to 0 when the window token is passed, determination of the pass condition of the window token and token buffer Token controller 44, which controls the window counter, and two types of variables, Cycle_MIN and Cycle_MAX, used as a criterion value of the pass condition of the window token in the token controller. It is composed of a variable buffer 45 for storing. Token buffer and window counter are assigned one for each priority, and token timer, token rotation time buffer, Cycle_MIN and Cycle_MAX are assigned one for each priority except the lowest priority. In the names of the parts of FIG. 4, the subscript indicates the priority, and the smaller the subscript value, the higher the priority.

The operation of the cell transmitter and the token processor having the above configuration will be described in detail using a flowchart.

5 is a flowchart illustrating a cell transmission method when an empty slot arrives in the cell transmission unit. When the node encounters an empty slot, the highest priority window counter (Window counter 1: 1 indicates the window counter priority) is greater than 0 and cells remain in transmission queue 1. Send one cell in queue 1 and decrement window counter 1 (56). If the above conditions are not met, check whether the window token rotation time of priority 1 exceeds the value of the defined variable to determine whether to pass the empty slot as it is or to pass the license of the empty slot to priority 2. 51). In other words, if the value of 1 in the token timer is less than Cycle_MIN1 and the value stored in the token rotation time buffer is less than Cycle_MAX1, the right of the empty slot is transferred to priority 2, and the value of token timer 1 is greater than Cycle_MIN1 or the token rotation time buffer If is greater than Cycle_MAX1, pass the empty slot (55). If the right of use of the empty slot is transferred to priority 2, the window counter and the transmission queue of priority 2 are checked (52). At this time, if the value of the window counter 2 is greater than 0 and there are remaining cells to be transmitted in the transmission queue 2, one cell in the transmission queue 2 is transmitted and the window counter 2 is decreased (57). If the above condition is not satisfied, the window token rotation time of priority 2 exceeds the value of the defined variable to determine whether to pass the empty slot as it is or to pass the license of the empty slot to priority 3 (53). ). In other words, if the value of Token Timer 2 is less than Cycle_MIN2 and the value stored in Token Rotation Time Buffer 2 is less than Cycle_MAX2, the license of the empty slot is transferred to Priority 3, and the value of Token Timer 2 is greater than Cycle_MIN2 or the Token Rotation Time buffer If the value of 2 is greater than Cycle_MAX2, an empty slot is passed (55). If the right of use of the empty slot is transferred to priority 3, the window counter and the transmission queue of priority 3 are checked (54). If the value of the window counter 3 is greater than 0 and there are remaining cells to be transmitted to the transmission queue 3, one cell in the transmission queue 3 is transmitted and the window counter 3 is decreased (58). If the condition 54 is not satisfied, Pass through without using an empty slot.

6 is a flowchart showing the operation when the window token of priority i (token i) arrives at the token processing unit. That is, when the window token i arrives at the token processing unit, the token stays in the token buffer i until the pass condition of the window token i is satisfied (66). The passing conditions of these window tokens are described below. When the pass condition of the window token is satisfied, the window token i is passed (62), the token timer i value is stored in the token rotation time buffer i (63), and the token timer i is initialized to 0 (64). Quota i is assigned to counter i (65).

When the window token of priority i (token i) arrives at the token processing unit, it can be passed only if the following four conditions are met simultaneously. In the notation, i, k, and j represent the priority and the value of 1 means the highest priority. 'j = 1, i' indicates that j represents a priority of any one of priority 1 to i. First, the window counter k = 0 or the send queue k = 0 for all k k satisfying k = 1, i, i.e. the window counter for each of all priorities from highest priority to priority i The value must be 0 or no cells remain in the transmission queue. Second, the token timer j <Cycle MINj must be present for all j that satisfies j = 1, i-1, i.e., higher than the priority of the window token. The token timer value of all priorities must be smaller than the Cycle_MIN value of the same priority. Third, the token rotation time buffer j <Cycle MAXj for all js satisfying j = 1, i-1. The value of the token rotation time buffer of all priorities higher than the rank must be smaller than Cycle_MAX of the same priority. Fourth, the window token j must not be present for all j satisfying j = 1, i-1. That is, window tokens with higher priority than window tokens should not remain in the node. If the priority of the window token is the highest priority (i = 1), the second, third and fourth conditions are not applicable.

Cycle_MINi and Cycle_MAXi variables used in the present invention should use the same value at all nodes, and the values of these variables are determined by priority, maximum propagation delay required by each priority, and ring delay. However, if the Cycle_MINi value is smaller than the ring delay, the ring rotation time of the window token of priority i is always greater than Cycle_MINi so that the priority is lower than i even when no load of the same or higher priority is applied. The load will not be able to use the band of the ring efficiently. Therefore, under normal conditions, the value of Cycle_MINi should be equal to or larger than the ring delay. If the value of Cycle_MAXi is set smaller than the ring delay, the ring rotation time of the priority i window token is always larger than Cycle_MAXi, and the priority lower than i cannot transmit the cell. Therefore, the Cycle_MAX value should always be set higher than the ring delay. .

The present invention assigns one window token to each priority to give a fair cell transmitter time between nodes according to the priorities, and each window token rotation time indicates the priority and the magnitude of the load having a priority higher than the priority. If the window token rotation time exceeds the specified value, it stops the low priority cell transmission of some nodes according to the excess level, which is why the delay of transmission media is lower than that of ATMR or Metaring, which changes the priority of the entire network intermittently. The decrease in utilization efficiency is significantly reduced. Thus, it can be applied to speeds of 1 gigabit per second or more and 100 kilometers or more. In addition, since the maximum access delay of the cell is determined by the rotation time of the window token of each priority, it is possible to predict the maximum access delay and limit the transmission of low priority cells when the rotation time of the window token exceeds the specified value. This has the effect of limiting the high priority maximum access delay to within the prescribed value.

Claims (8)

A cell receiver 23 for receiving a cell and a cell transmitter for transmitting a plurality of priority cells, connected to a single ring in which a plurality of continuous slots are rotated or a double ring in which slots of a predetermined length are rotated in opposite directions. (24), the access unit comprising a token processing unit 25 for controlling the flow of the window token; The cell transmitter unit transmits a transmission queue 42 for storing a cell to be transmitted, a cell transmitter 41 for transmitting a cell in the transmission queue to an empty slot when an empty slot arrives, and whether or not to transmit a cell when the empty slot arrives. It consists of a transmission controller 43 for determining the priority of the cell to be performed, the token processing unit token distributor 40 for distributing the received window token by priority, the token temporarily storing the window token until the pass condition is satisfied. The buffer 49 is decremented every time a cell is transmitted from the transmission controller, and is initialized to a quota value every time the window token is passed, and is initialized to zero each time the window token is passed, and as time passes. Increased token timer 47, token rotation time buffer 46 for storing the token timer value at the moment when the window token passes, variable buffer 45 for storing Cycle_MIN and Cycle_MAX variable values, pass condition of the window token High speed medium access control device judges whether or not the group, characterized by consisting of a token controller 44, which determines the passage of the token window. The apparatus of claim 1, wherein the transmission queue, the token buffer, and the window counter have one priority for each priority, and the token timer and token rotation time buffer are allocated one by one for each priority except the lowest priority. 2. The apparatus of claim 1, wherein the transmission direction of the cell and the rotational direction of the window token are the same in the case of a single ring, and the rotational direction of the cell transmission direction and the window token is in the case of the double ring. 2. The apparatus of claim 1, wherein one window token is assigned to each priority and several window tokens rotate the ring at the same time. 2. The apparatus of claim 1, wherein the variable values of Cycle_MIN and Cycle_MAX should be set to a value larger than the delay value of the ring, and all access units should use the same value. A transmission queue 42 for storing the cell to be transmitted, a cell transmitter 41 for placing a cell in the transmission queue into an empty slot when an empty slot arrives, and whether the cell is to be transmitted or not when the empty slot arrives. A cell transmitter 24 having a transmission controller 43 for determining the priority, a token distributor 40 for distributing received window tokens by priority, and temporarily storing the window tokens until the window token pass condition is satisfied Token buffer 49, which is decremented every time a cell is transmitted from the transmission controller, window counter 48 that is initialized to a quota value every time the window token passes, and initializes to 0 each time the window token passes, and time elapses. Token timer 47, which is increased according to the change, the token rotation time buffer 46 storing the token timer value at the time of passing the window token, the variable buffer storing the Cycle_MIN and Cycle_MAX variable values, and satisfying the pass condition of the window token Parts determined by according to the high-speed medium access control device consisting of a token processor (25) having a token controller 44, which determines the passage of the window token; When the empty slot arrives at the cell transmitter, a first step of determining whether or not to transmit the cell and the priority of the transmitting cell; a second step of transmitting the cell and reducing the window counter when the cell is determined; In the third step of determining whether the pass condition of the window token is satisfied, the third step is to hold the pass of the window token until the pass condition of the window token is satisfied.If the pass condition of the window token is satisfied, the pass window token is passed and the token timer is set. Storing the token in the token rotation time buffer, and performing a fifth step of allocating a quota to the window counter and initializing the token timer to zero when the window token passes. In the second step of claim 6, if the cell in the transmission queue of priority i is transmitted, the window counter value of priority i is greater than 0 and the value of the token rotation time buffer of all priorities higher than 1 is the priority. A high speed medium access control method characterized by having a value less than Cycle_MAX value of a rank and a token timer value of all priorities higher than i being smaller than a Cycle_MIN value of a corresponding priority. In order to pass the window token of priority i in the fourth step of Claim 6, first, the window counter value is 0 or is transmitted to the transmission queue for each priority from the highest priority to the priority i. There should be no cells left, second, the token timer value of all priorities higher than the priority of window token must be smaller than Cycle_MIN value of the corresponding priority, and third, the token rotation time higher than the priority of window token. 4. The method of claim 1, wherein the buffer value must be smaller than Cycle_MAX of the corresponding priority, and fourth, the window token having a priority higher than that of the window token must not remain in the node.