KR100454917B1 - Apparatus and method for automatical expiration of virtual channel connection in atm switch - Google Patents

Abstract

An apparatus and method for automatically destroying a virtual channel connection (VCC) in an Asynchronous Transfer Mode (ATM) switch. The apparatus includes a timer memory for storing counter values for each of the plurality of virtual channel connections, a sequential access control unit for generating a sequential access request signal at predetermined times, and a random access request signal when a first or last packet is input. A random access control unit generating a random access control unit; An access mediation unit for accessing a memory to increment or record the counter value, and writing or clearing the data; and a virtual channel in which the counter values stored in the timer memory are read and compared with a predetermined value, and the counter value reaches a predetermined value. Includes an extinction checker that outputs a connection destruction signal for the connections. And it characterized in that.

Description

Apparatus and method for automatically destroying virtual channel connections in asynchronous transfer mode switch {APPARATUS AND METHOD FOR AUTOMATICAL EXPIRATION OF VIRTUAL CHANNEL CONNECTION IN ATM SWITCH}

The present invention relates to an asynchronous transfer mode (ATM) switch, and more particularly, to an apparatus and a method for automatically extinguishing a virtual channel connection (VCC).

In general, in an ATM switch (eg, an AAL2 switch) in which a plurality of packets are input and reassembled into an ATM cell having the same single virtual channel connection (VCC), and output. The timer queue (Timer_cu or combined use timer) refers to a function of outputting the first packet after being mapped to a corresponding ATM cell and irrespective of completion of reassembly of the cell after a predetermined time elapses. In other words, the timer queue is a function that automatically terminates the virtual channel connection after a predetermined time elapses. At this time, it is said that extinguishment of a forced output after a certain time has elapsed before reassembly. The reason for this forcing is to allow ATM cells to be delivered without delay. That is, the ATM switch needs a function for automatically destroying the virtual channel connection when some time has passed since the first packet was input.

1 is a diagram illustrating an example of a configuration for automatically extinguishing a virtual channel connection (VCC) in an ATM switch according to the prior art.

As shown, there are a plurality of timers (Timer # 0 to Timer #N) 120 to 12N corresponding to each of the plurality of VCC connections. First, the VCC check and timer control unit 100 checks the VCC corresponding to the packet when the packet is input and drives a timer corresponding to the VCC. Then, the timer increments the counter every predetermined time. Meanwhile, the timer expiration check block 110 checks counter values of each of the plurality of timers and checks whether a predetermined counter value has been reached. When the timer reaches the predetermined counter value, a signal for extinguishing the VCC corresponding to the timer (a signal for outputting an ATM cell corresponding to the VCC regardless of reassembly completion) is output. . On the other hand, the VCC disappearance signal is provided to the VCC check and timer control unit 100, the timer control unit 100 clears the corresponding timer when the extinction signal is input.

That is, the above structure is a simple structure that implements a block corresponding to a timer using a logic counter. A timer is allocated one-to-one for each virtual channel connection (VCC), and if there is a packet input of the corresponding VCC, the counter performs a counter up every predetermined time. In the meantime, if the same VCC packet is input again, the counter is cleared. In other words, it is possible to know how much time has passed since the first packet was input by referring to the counter value.

2 is a diagram illustrating another example of a configuration for automatically extinguishing a virtual channel connection (VCC) in an ATM switch according to the prior art.

As shown, unlike FIG. 1, only one reference timer 220 exists. The VCC inspection unit 200 sets the first of the incoming packets as a base connection and drives the reference timer 220 in response to the base connection. On the other hand, the time difference calculator 221 calculates the difference between the time input for the next input packet (or connection) and the immediately preceding connection by referring to the time of the reference timer 200 Write to timer table 230. In this case, the time difference calculator 221 records all of the previously input connection, the time difference from the previously input connection, and the next input connection corresponding to any connection. On the other hand, the timer disappearance inspection unit 210 destroys the connection after a predetermined time after the initial connection based on the time of the reference timer 220. Subsequent connections are subsequently destroyed based on the input time difference from the previous connection stored in the timer table.

That is, the structure as shown in FIG. 2 does not calculate the elapsed time for packets having different connections (VCCs) individually, but the elapsed time can be known with the time difference between the packets inputted back and forth. In other words, the first of the incoming packets is the base connection, by which the reference timer is started, and the incoming packets are entered just before the value of the reference timer at the moment of input. The input time difference from the value of the established connection is recorded in a timer table. The connections are subsequently destroyed based on the input time difference.

The problems according to the above-mentioned prior art are summarized as follows.

First, referring to the structure of FIG. 1, a logical counter must be allocated to each virtual channel connection (VCC). Therefore, when the connection (VCC) increases, the corresponding logic counter must also increase accordingly, thereby increasing the volume of the system. And there is a problem that can not be practically implemented in terms of load.

Referring to the structure of FIG. 2, compared to the structure of FIG. 1, since there is only one counter, the number of connections is not limited. However, there is a burden of calculating the time link relationship and the input time difference with the VCC connection before and after corresponding to each packet, and always recording them in the timer table. If the logic for calculating the link relationship and time difference is implemented in hardware (H / W), there is a problem that is too complicated. In addition, there is a problem in that a chain error may occur if one link relationship is misaligned due to its structure.

Accordingly, an object of the present invention is to provide an apparatus and method for automatically destroying a virtual channel connection after a predetermined time has elapsed after the first input packet is mapped to an ATM cell in an ATM switch. .

According to an embodiment of the present invention, an apparatus for automatically destroying a virtual channel connection in an ATM switch includes: a timer memory storing a counter value for each of a plurality of virtual channel connections, and a predetermined time; A sequential access control unit for generating a sequential access request signal each time, a random access control unit for generating a random access request signal when the first or last packet is input, and storing information indicating whether the virtual channel connections are valid or invalid; A connection status register having areas, an access arbitration unit for accessing the timer memory each time the sequential access request signal or the random access request signal is generated, incrementing the counter value, and writing or clearing the counter, and stored in the timer memory. Read counter values and compare them with a predetermined value, Characterized in that it comprises a checking unit for outputting the extinction connection extinction signal for the group of the virtual channel connected to the counter value reached a predetermined value.

According to an embodiment of the present invention for achieving the above object, a timer memory for storing a counter value indicating the elapsed time after the first packet input for a plurality of virtual channel connections, and, for each of the virtual channel connections, A method for forcibly destroying a virtual channel connection in an ATM switch having a connection status register having areas indicating information indicating invalidity, the method comprising: checking whether an access request is generated for the virtual channel connection; And a second process of clearing a corresponding counter value of the timer memory and validly writing to a corresponding area of the connection status register if the access request detected in the first process is a random access request according to a first packet input. If the access request detected in step 1 is a random access request according to the last packet input, A third process of generating a connection destruction signal for destroying the virtual channel connection and invalidating it in a corresponding region of the connection status register; and accessing the timer memory if the access request detected in the first process is a sequential access request. The counter value is read and the read counter value is compared with a predetermined value. If the two values are the same, a connection destruction signal for destroying the virtual channel connection is generated. Otherwise, the timer memory is accessed to access the count value. After the fourth process of increasing and recording, and after performing the fourth process, it is checked whether or not the access to the entire virtual channel connection is terminated, and returns to the first process if it is terminated, and if not, access to the next virtual channel connection is finished. And a fifth process of returning to the fourth process.

1 is a diagram illustrating an example of a configuration for automatically extinguishing a virtual channel connection (VCC) in an ATM switch according to the prior art.

2 illustrates another example of a configuration for automatically extinguishing a virtual channel connection (VCC) in an ATM switch according to the prior art.

3 is a diagram illustrating a configuration for automatically extinguishing a virtual channel connection (VCC) in an ATM switch according to an embodiment of the present invention.

4 is a diagram illustrating a configuration of the timer memory of FIG. 3.

5 is a diagram illustrating a configuration of a connection state register of FIG. 3.

FIG. 6 is a diagram showing a correspondence relationship between ATM cells destined for an Nth VCC and incoming packets; FIG.

7 is a diagram illustrating access state transition of a timer memory according to an exemplary embodiment of the present invention.

8 is a diagram illustrating a control procedure for automatically destroying a virtual channel connection in an ATM switch according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, the present invention will be described for implementing the portion corresponding to the timer described in the prior art by using a memory rather than a logic counter. When implemented using the memory, it is possible to remove the limitation on the logic size mentioned in the prior art, and to establish a very large number of connections.

3 is a diagram illustrating a configuration for automatically extinguishing a virtual channel connection (VCC) in an ATM switch according to an embodiment of the present invention. That is, FIG. 3 shows an example of the implementation of a timer queue (timer_cu) in an ATM switch. The ATM switch may be an ATM allocation layer 2 (ALL2) switch.

Referring to FIG. 3, a timer memory 360 stores counter values indicating elapsed time after the first packet input for each of the plurality of connections VCC. The counter values are countered up by the periodic access of the access arbitration unit 320. The timer memory 360 allocates 8 bits as a time counter for one connection. Each region (8 bits) of the timer memory 360 replaces the existing logic counter one-to-one. An example of the timer memory 360 is illustrated in FIG. 4. As shown, the timer memory 360 has N entries, each entry storing counter values for four connections. Meanwhile, an 8-bit data area is allocated for one counter value.

The connection valid register 350 is a register in logic. The basic configuration is the same as that of the timer memory 360, and the data area is 1 bit, and the connection is valid for each of the plurality of connections. Stores information indicating whether a connection is valid or invalid. Here, the meaning of the connection is valid indicates a state after the packet having the connection is input, and the time point when the connection is valid is a time point when the packet of the connection is input. On the other hand, the point of invalidity is the time when the reassembly of the ATM cell for the connection is completed or when the connection is destroyed. An example of the connection state register 350 is shown in FIG. 5. As shown, the connection state register 350 has N entries, each entry storing state values for four connections. Meanwhile, one bit data area is allocated for one state value.

The input buffer 300 stores and outputs an input packet in a first input first output (FIFO) manner. The random access controller 310 generates a random access request (RA Request) signal to the access arbitration unit 320 when a packet input is detected through the input buffer 300. The sequential access control unit 330 generates a sequential access request signal to the access arbitration unit 320 at a predetermined time resolution. The predetermined time resolution means the minimum time required to access the timer memory 360 and increment the counter values of the entire connection by one.

The access arbitration unit (SA / RA Arbitration) 320 adjusts the access (read / write) authority of the timer memory 360 between the random access control unit 310 and the sequential access control unit 330. That is, the access arbitration unit 320 receives the random access request and sequential access request signals to access the timer memory 360 and the connection state register 350. Here, the series of access operations generated in the random access request signal is called "random access", and the series of access operations generated in the sequential access request signal is called "sequential access". Here, in the case of the sequential access, the entire area of the timer memory 360 is read and written within the predetermined time resolution, and in the case of random access, the sequential access is prioritized in almost real time with the packet input. Do it.

An expiration check unit 340 checks whether counter values output by the access of the timer memory 360 have reached a predetermined value (connection extinction value), and extinguish signal ( expired VCC).

An operation based on the configuration of FIG. 3 is as follows.

Referring to the sequential access, when the sequential access request is generated from the sequential access control unit 330, the access arbitration unit 320 regularly performs the timer memory 360 and the connection state register 350 twice at a time. Read and write). First, the connection status register 350 is read to check whether the connection is valid. If it is not valid, the counter value (corresponding data in timer memory) of the connection is cleared. If the connection is valid, the extinction checker 340 checks whether the counter value of the connection reaches a predetermined extinction value. When the predetermined extinction value is reached, the extinction test unit 340 outputs an extinction signal for the corresponding connection, clears an area corresponding to the connection of the timer memory 360, and checks the connection state register 350. Record the invalid status in the area corresponding to the connection. When the predetermined extinction value is not reached, the counter value of the corresponding connection is increased by "1" to overwrite the corresponding area. As an example, the time resolution is set at 125 ms and completes access for all connections for 125 ms. That is, the counter value for each connection increments by 1 every 125 ms.

Next, referring to random access, when packets of a reassembled ATM cell are input, the random access controller 310 determines that a packet of the inputted reassembled ATM cell is a first packet or a last packet. Determine if When the packet of the reassembled ATM cell is the first packet or the last packet, the random access controller 310 outputs a random access request signal to the access arbitration unit 320. Here, the meanings of the first packet and the last packet are as shown in FIG. 6. As shown, the first packet refers to the first input packet among the packets reassembled into the ATM cell, and the last packet refers to the last input packet. Then, the access arbitration unit 320 receiving the random access request signal according to the first packet input clears the counter value of the connection of the timer memory 360 and clears the corresponding area of the connection state register 350. Record valid. Until the random access request signal according to the last packet input is input to the access arbitration unit 320, the corresponding area of the connection state register 350 continues to be valid. Meanwhile, the access arbitration unit 320 receiving the random access request signal according to the last packet input clears the counter value of the connection of the timer memory 360 and invalidates the corresponding area of the connection state register 350. Record as (invalid).

7 is a diagram illustrating an access state transition of the timer memory 360 according to an exemplary embodiment of the present invention.

As shown, reference numerals 711 to 729 represent various states that may occur in accordance with an embodiment of the present invention. If the random access RA does not occur in the standby states RDY and 711, and only the sequential access SA occurs, the process transitions to the sequential access 0 states SR0 and 713. Thereafter, the Nth address and the N + 1th address of the timer memory 340 are read in the sequential access 0 state 713 and the sequential access 1 state 715, respectively. At this time, the connection status register 350 of the same address is read to check whether the connection is valid. Then, the state transitions to SX state 717. Here, the SX state 717 is a state defined to provide a spare time for determining data to latch and update again the value of the read timer memory.

After the predetermined time elapses by the SX state 717, the state transitions to the sequential write 0 states (SW0 and 719) and the sequential write 1 states (SW1 and 721). In the sequential write 0 and sequential write 1 states, an update value determined based on the read timer memory and connection state register values, respectively, is overwritten to the timer memory and the connection state register. In addition, the sequential write 1 state determines whether or not the four connections included in the Nth address and the connections included in the N + 1th address are destroyed and outputs the result. Here, in outputting the disappearance signal, a sequential access end signal (SAEND) is generated so as not to overlap with the extinction signal to be output in the next cycle. On the other hand, if no request signal is generated in the sequential access 1 state 721, the state transitions to the standby state 711, and if a random access request occurs, the state transitions to the random access state 723. As described above, the sequential access SA is performed over five clocks.

Random access (RA) is performed by four clocks. When a packet input is detected in the standby state 711 and a random access request (RA Req) occurs, a transition to the random access state (RR, 723) occurs. The random access state reads the address of the timer memory and the connection state register with the vcc of the input packet. In the RX state 725 and the RXX state 727, the read data is latched in consideration of the delay, and the data to be updated is determined. Thereafter, in the random write state (RW) 729, the determined update data is written to the timer memory and the connection state register.

8 is a diagram illustrating a control procedure for automatically destroying a virtual channel connection in an ATM switch according to an embodiment of the present invention.

Referring to FIG. 8, the access mediation unit 320 checks whether the random access request signal is received in step 811. Here, the random access request signal is generated when the first packet or the last packet of the reassembled ATM cell is received. If the random access request signal is received, the process proceeds to step 831. Otherwise, the process proceeds to step 813 to determine whether a sequential access request signal is received. In this case, when the sequential access request signal is received, the process proceeds to step 815, and if not, the process returns to step 811 to check whether the random access request signal is received.

Upon receiving the sequential access request signal, the access mediation unit 320 initializes an entry value N for accessing the timer memory 360 and the connection state register 350 in step 815. In operation 817, the access mediation unit 320 reads data of the Nth and N + 1th regions of the timer memory 360 and the connection state register 350 shown in FIGS. 4 and 5. That is, it reads counter values and connection validity for all eight connections. On the other hand, the extinction test unit 340 analyzes the read data in step 819 and checks whether the connection connection condition is satisfied. That is, each of the read counter values is compared with a predetermined extinction value to check whether there is a counter value that has reached the extinction value.

If there is data that satisfies the connection extinction condition, the extinction test unit 340 proceeds to step 821 and outputs a sequential access termination signal (SAEND) to the access arbitration unit 320, and simultaneously corresponds to the connection in step 823. The connection destruction signal is output to the cell reassembly unit (not shown) and the access arbitration unit 320. Then, the cell assembly unit immediately outputs the ATM cell of the connection regardless of completion of reassembly. The access mediation unit 320 clears the region of the memory corresponding to the connection, records the region of the connection state register corresponding to the connection in an invalid state, and proceeds to step 825.

On the other hand, for connections where the connection destruction signal is not enabled, the access arbitration unit 320 proceeds to step 829 and increments and updates the counter values of the timer memory 360 corresponding to the corresponding connection by one. The flow proceeds to step 825. In step 825, the access arbitration unit 320 checks whether access to all entries is completed. That is, since the entry has a predetermined number, it is checked whether the variable N value has reached the predetermined number. If the access to the entire entry is completed, the process returns to step 811 again to perform the following steps, otherwise proceeds to step 827. In step 827, the access arbitration unit 320 increases the entry value N by 2 and returns to step 817 to continue the sequential access, and then performs the following steps again.

On the other hand, when a random access request is received, the access arbitration unit 320 reads the corresponding regions of the timer memory 360 and the connection state register 350 with the corresponding VCC in step 831, and in step 833. Determine update information. In operation 835, the access arbitration unit 320 overwrites the update information to the corresponding regions of the timer memory 360 and the connection state register 350. If the random access request is generated by the first packet input, the access arbitration unit 320 clears the counter value of the timer memory 360, and activates the corresponding area of the connection state register 350 in a valid state. Record as. Until the random access request is generated by the last packet input, the corresponding region of the connection state register 350 remains valid. On the other hand, if the random access request is generated by the last packet input, the counter value of the timer memory 360 is cleared, and the corresponding area of the connection state register 350 is recorded as an invalid state.

As described above, the ATM switch according to the present invention, when one packet is input, generates a random access request signal from the random access control unit 310, accordingly, the access arbitration unit 340 is the timer corresponding to the connection; Only the regions of the memory 360 and the connection state register 350 are read, corrected, and overwritten again. If the random access request does not occur again after completing the random access operation, the access arbitration unit 340 performs the sequential access operation. The sequential access control unit 330 generates a sequential access request signal at a time interval of 125 ms. The time resolution value may be defined as the sum of the maximum possible number of random accesses and the completion time of sequential access processing. In other words, sequential access to all areas of the timer memory must be completed within the period, and should be possible with random access processing for the largest packet inputs. In an embodiment of the present invention, two address areas are updated at a time for more efficient memory access in the sequential access process. However, depending on the structure, it can be configured to access N at a time. The access mediation unit 320 reads the entire area of the timer memory in response to the sequential access request signal, and the extinction test unit 340 analyzes the read counter values to disconnect connections for connections that satisfy the extinction condition. Generates an (expire connection) signal.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, according to the present invention, by configuring a timer using a memory in the ATM cell assembling apparatus, the present invention can have the same effect as driving the timer individually for a plurality of connections without being limited in logic size. In addition, by efficiently adjusting the memory access method to match system performance, the accuracy is similar to using a logic counter. The implementation of such a timer can be applied as a timer queue (timer_cu) in an AAL2 switch that performs ATM cell disassembly and assembly, and can be applied to a timer queue of other similar systems.

Claims (7)

An apparatus for automatically destroying a virtual channel connection in an asynchronous transfer mode switch, A timer memory for storing counter values for each of the plurality of virtual channel connections; A sequential access control unit for generating a sequential access request signal every predetermined time; A random access controller which generates a random access request signal when a first or last packet is input; A connection status register having areas for storing information indicating presence or absence of the virtual channel connections; An access arbitration unit that accesses the timer memory each time the sequential access request signal or the random access request signal is generated, increments the counter value, and writes or clears it; And an extinction checker configured to read counter values stored in the timer memory, compare the counter values with a predetermined value, and output a connection destruction signal for virtual channel connections in which the counter value reaches a predetermined value. Device. The method of claim 1, And wherein said asynchronous transfer mode switch is an ATM Adaption Layer 2 (AAL2) switch. The method of claim 1, When the sequential access request signal is generated, the connection status register is read to clear the counter value of the timer memory if the virtual channel connection is in an invalid state, and if the counter value is valid, the counter value of the timer memory is predetermined. If larger, the counter value is cleared and invalidated in the corresponding area of the connection status register. If smaller, the counter value is incremented and overwritten. When the start packet is input and the random access request signal is generated, the corresponding counter value of the timer memory is cleared and validly written in the corresponding area of the connection status register. When the last packet is input and the random access request signal is generated, And clearing the corresponding counter value in the timer memory and invalidating the corresponding counter value in the connection status register. The method of claim 1, And the access arbitration unit clears a counter value of a corresponding virtual channel connection when the connection destruction signal is generated. A connection memory register having a timer memory for storing counter values indicating an elapsed time after the first packet input for a plurality of virtual channel connections, and areas for storing information indicating whether the virtual channel connections are valid or invalid; In the asynchronous transfer mode switch comprising: a method for forcibly destroying the virtual channel connection, A first step of checking whether an access request is generated for the virtual channel connection; A second step of clearing a corresponding counter value of the timer memory and validly writing to a corresponding area of the connection status register if the access request detected in the first step is a random access request according to a first packet input; A third step of generating a connection destruction signal for erasing the virtual channel connection if the access request detected in the first step is a random access request according to a last packet input, and writing the signal to the corresponding area of the connection status register invalidly; If the access request detected in the first process is a sequential access request, the timer memory is accessed to read a corresponding counter value, and if the two counter values are equal to each other, the corresponding counter value is read. A fourth process of generating a connection destruction signal for the second memory device, and if not equal, accessing the timer memory to increase the corresponding count value and to record the count value; After performing the fourth process, checking whether access to all virtual channel connections is terminated returns to the first process, and if not, returning to the fourth process for access to the next virtual channel connection. Method comprising five processes. The method of claim 5, And wherein the asynchronous transfer mode switch is an ATM Adaption Layer 2 (AAL2) switch. The method of claim 6, And clearing a counter value of a corresponding virtual channel connection of the timer memory when the connection destruction signal is generated.