KR100221330B1 - Method of Efficient Use of Residual Bandwidth by Partitioning and Recombining the ALA Layer - Google Patents

Abstract

According to the present invention, in order to select a cell to be serviced in a scheduling table of a partitioning and reassembly (SAR) sublayer, the cell is circulated through the scheduling table of a partitioning and reassembly (SAR) sublayer instead of manually searching for a connection having cell data to be sent. When data or idle cells are sent down, the AAL layer removes idle cells by reading the headers of the cells at the interface between the split and recombination (SAR) sublayer and the physical layer to remove idle cells from the sub-layer of the AAL layer. A method for efficiently using the remaining bandwidth, the method comprising: a first step (S1) of reading a cell header from the division and recombination (SAR) sublayer; A second step (S2) of checking the cell header read in the first step (S1) by the idle cell removing means (2) to determine whether it is an idle cell; A third step S3 of determining whether it is an idle cell as a result of the determination in the second step S2; A fourth step S4 of discarding the current cell when the determination result in the third step S3 is an idle cell; When the determination result in the third step (S3) is not an idle cell, it is characterized in that the fifth step (S5) for transmitting the current cell to the physical layer.

Description

Efficient Use of Residual Bandwidth by Idle Cell Removal in AAL Segmentation and Recombination (SAR) Sublayer

The present invention relates to a method of efficiently using the remaining bandwidth by removing idle cells in the split and recombine (SAR) sublayer of the AAL layer, and in particular, to select a cell to be serviced in the scheduling table of the split and recombine (SAR) sublayer. Instead of looking for connections that currently have cell data to send, you can cycle through the scheduling table of the split and recombination (SAR) sublayers and send down cell data or idle cells to interface between the split and recombination (SAR) sublayers and the physical layer. The present invention relates to a method of efficiently using the residual bandwidth by removing an idle cell in a sub-layer of the AAL layer whereby the residual bandwidth is efficiently used by reading the header of the cell and removing the idle cell.

In general, the ATM Adaptation Layer (ATM) adapts the service provided by the ATM layer to the requirements of the upper layer user. Therefore, the ATM adaptation layer must provide support for the asynchronous transmission mode communication environment and the asynchronous transmission mode communication environment in addition to performing support of the user plane, the higher level control plane and the management plane.

In addition, the ATM adaptation layer maps the protocol data unit (PDU) of the upper layer to the payload section of the ATM cell, handles transmission errors, processes and flows control of lost and inserted cells. It provides timing control. The ATM adaptation layer is divided into two sublayers: a segmentation and reassembly (SAR) sublayer and a convergence sublayer (CS).

The convergence sublayer (CS) performs a function related to a specific service, and the partitioning and recombination (SAR) processes a function related to service segmentation and recombination by processing a function that is not related to service termination. Therefore, at the transmitting side, the convergent sublayer (CS) is applied as user information from an upper layer, attaches a header and a trailer, forms a convergent sublayer protocol data unit (CS-PDU), and sends it to a split and recombination (SAR) sublayer. This split and recombine (SAR) sublayer cuts it into the size of an ATM cell, attaches a header and a trailer to form a split and recombine protocol data unit (SAR-PDU) and transmits it through the ATM layer.

On the receiving side, the segmentation and recombination (SAR) sublayer extracts only the payload interval among the segmentation and recombination protocol data units (SAR-PDU) received through the ATM layer to form a convergence sublayer protocol data unit (CS-PDU). After that, the information is transferred to the convergence sublayer CS, and the convergence sublayer CS extracts only upper layer user information among the received convergence sublayer protocol data units CS-PDUs and delivers the information to the upper layer.

At this time, the header and the trailer attached to each sub-layer in the transmission process are related to error processing, buffer management, and sequence preservation. Will be passed to the layer.

On the other hand, ITU-T classifies user services into four types of A, B, C, and D according to constant bit rate (CBR), real time, and connectivity, and AAL type to correspond to these various services. It is defined by dividing into 1 to 4. In addition, the June 1992 ITU-T Conference newly discussed AAL Type 5 to support high-speed data communications.

In the AAL type 1, a real-time equal bit rate service is provided in a connected manner, and a service provided to a user is largely equal bit rate (CBR) data transfer, timing information transfer, user data structure information transfer, error recovery capability, and cannot be recovered. Display of information about errors and losses.

In general, in the partitioning and recombination (SAR) sublayer of the AAL layer, scheduling is performed by using a scheduling table. When an empty entry is reached while circulating the scheduling table, an empty cell is received. Will be sent down to the physical layer. In this case, the empty cell is a cell that does not contain any information, and when the empty cell is received in the partitioning and recombination (SAR) sublayer of the receiving AAL layer, the empty cell is discarded.

However, in the physical layer, all cells coming down from the split and recombination (SAR) sublayer are regarded as valid cells and transmitted over a physical link, thereby causing a problem of wasting bandwidth in transmitting empty cells having no information.

Accordingly, the present invention is to solve the above problems, in the scheduling table of the partitioning and reassembly (SAR) sub-layer, instead of looking for a connection that has the cell data to be sent currently to select a cell to be serviced, the partitioning and recombination (SAR) When the cell data or idle cells are rotated while rotating the scheduling table of the sub-layer, the remaining bandwidth can be effectively used by removing the idle cells by reading the headers of the cells at the interface between the sub-layer and the physical layer. An object of the present invention is to provide an efficient method of using the remaining bandwidth by eliminating idle cells in the split and recombination (SAR) sublayer of the AAL layer.

In order to achieve the above object, the present invention provides a scheduling table of a partitioning and reassembly sublayer instead of manually searching for a connection having cell data to be sent in order to select a cell to be serviced. Residual bandwidth due to idle cell removal in the split and recombination sublayer of the AAL layer that removes idle cells by reading the cell headers at the interface between the split and recombination sublayer and the physical layer when cycling down cell data or idle cells A method for efficiently using the method, comprising: a first step of reading a cell header from the division and recombination sublayer; A second step of judging whether the cell header read in the first step is by an idle cell removing means to determine whether it is an idle cell; A third step of determining whether it is an idle cell as a result of the determination in this second step; A fourth step of discarding the current cell when the determination result in the third step is an idle cell; When the determination result in the third step is not the idle cell, it is characterized in that the fifth step of transmitting the current cell to the physical layer.

The present invention configured as described above, in the scheduling table of the partition and reassembly (SAR) sublayer, instead of manually searching for a connection having cell data to be sent to select a cell to be serviced, the partition and reassembly (SAR) sublayer Sending down cell data or idle cells while rotating the scheduling table allows the remaining bandwidth to be effectively used by removing the idle cells by reading the headers of the cells at the interface between the partition and recombination (SAR) sublayers and the physical layer.

1 is a conceptual diagram illustrating a general ATM protocol reference model;

2A is a diagram showing a data format of an ATM cell;

2b is a diagram illustrating a header structure in a user network interface (UNI);

FIG. 2C shows the header structure at the network node interface (NNI); FIG.

3 is a diagram illustrating a data format for each layer in an asynchronous transmission mode communication method;

FIG. 4 is a block diagram showing an embodiment of an apparatus for efficiently utilizing residual bandwidth by removing idle cells in a split and recombination (SAR) sublayer of an AAL layer according to the present invention; FIG.

FIG. 5 illustrates an embodiment of a method for efficiently using residual bandwidth by removing idle cells in a split and recombination (SAR) sublayer of an AAL layer according to the present invention.

* Explanation of symbols for the main parts of the drawings

1: SAR layer, 2: idle cell removal unit,

3: physical layer transmitter, 4: physical layer receiver,

5: physical layer.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail

First, to simplify the understanding of the present invention briefly described asynchronous transmission mode communication method to which the present invention is applied

1 is a conceptual diagram illustrating an ATM protocol reference model, wherein the openness is composed of a management plane, a control plane, and a user plane, and the management plane is again hierarchical. It will consist of management and flat management. In addition, the plane management means the overall management of the system, and the hierarchical management manages resource and usage variables and OAM information management.

In addition, the control plane manages call control and connection control information, and the user plane transmits user information. The protocol of the control plane and the user plane is composed of a higher layer, an ATM adaptation layer, an ATM layer, and a physical layer.

As shown in FIGS. 2A to 2C, the user's long message is divided into ATM cells and transmitted, and the received ATM cell is reassembled into one message and transmitted to the upper user. .

FIG. 2A is a diagram illustrating a data format of an ATM cell, FIG. 2B is a diagram illustrating a header structure at a user network interface (UNI), and FIG. 2C is a diagram illustrating a header structure at a network node interface (NNI).

Here, the ATM cell is divided into a header section of 5 bytes (or octets) and a user information section of 48 bytes, and the header of 5 bytes is a user network interface (UNI) as shown in FIGS. 2B and 2C. Header structure in user network interface (UNI), where the first byte is a 4-bit generic flow control (GFC) and a 4-bit virtual path identification number (VPI) identifier).

The second byte is composed of a 4-bit virtual path identification number (VPI) and a 4-bit virtual channel identifier (VCI), and the third byte is an 8-bit virtual channel identification number (VCI). The fourth byte consists of a 4-bit virtual channel identification number (VCI), a 3-bit payload type (PT), and a 1-bit cell loss priority (CLP). The byte consists of 8 bits of header error control (HEC).

Also, in the header structure of the network node interface (NNI) as shown in FIG. 2C, the general flow control (GFC) in the first byte of the user network interface (NNI) is converted into a virtual path identification number (VPI). Except for being used, it can be seen that it is identical to the header structure of NNI. This asynchronous transmission mode communication method has a hierarchical structure as shown in Table 1 below and has standardized standards for each layer.

Hierarchy Tier function Upper hierarchy Higher layer function ATM Adaptation Layer Convergence (CS) sublayer Convergence function Cutting and Recombination (SAR) Cutting function and recombination function ATM layer General flow control and cell header processing Physical layer Transmission Convergence (TC) HEC signal generation and extraction function Physical medium Bit time information function

As shown in Table 1, the asynchronous transmission mode communication method is divided into vertical structures such as a physical layer, an ATM layer, an ATM adaptation layer (AAL), and a higher protocol layer. It is divided into segmentation and reassembly sublayer (SAR) and convergence sublayer (CS) sublayer, and the physical layer is divided into physical medium (PM) and transmission convergence (TC) sublayer.

In addition, a service required by a user in an asynchronous transmission mode communication method may be classified as shown in Table 2 below according to its characteristics.

Type of service End-to-end time relationship Bit rate Connection mode Example of service Class A Real time Identity Connectivity Video signal Class B Real time variable Connectivity Variable Rate Video Signal Class C Non-real-time variable Connectivity Connectivity data Class D Non-real-time variable Connectionless Connectionless data

The AAL protocol corresponding to the service is divided into AAL 1 to AAL 5 as shown in Table 3 below.

AAL form Typical feature AAL 1 Support class A service of equal bit rate AAL 2 Support real-time, variable bit rate Class B service AAL 3/4 Support class C and D services with variable bit rate AAL 5 High speed service by simplifying AAL 3/4 function

In Table 3, the AAL layer is divided horizontally as AAL 1, AAL 2, AAL 3/4, and AAL 5 to efficiently process the corresponding service according to the type of service.

Here, the AAL layer 1 is a convergent sub-layer (CS) that transparently transmits a Class A service data unit (U-SDU) having a constant bit rate, detects transmission errors, and performs information identification and clock synchronization functions. A split and recombination sublayer (SAR) that divides variable-length data received from the convergence sublayer (CS), creates an ATM cell, transfers it to the ATM layer, and receives and reassembles the ATM cell from the ATM layer to recover the CS-PDU. Will be divided into

In addition, the convergence (CS) sublayer is a common part convergence sublayer (CPCS) in charge of functions common to connectivity and connectionless services, and a service specific convergence sublayer for providing a specific AAL user service. (SSCS: service specific convergence layer).

FIG. 3 is a diagram illustrating a data format for each layer in the asynchronous transmission mode communication method, in which a user service data unit (U-SDU) of a higher layer passes through an AAL service access point (AAL-SAP). After that, it is formed as AAL service data unit (AAL-SDU) and stored in AAL FIFO.In the AAL1 SAR layer, the CS-PDU is divided by 47 bytes according to the message to be transmitted by the user, and then added by adding 1 byte of SAR header. And a recombination protocol unit (SAR-PDU) is formed and sent down to the ATM layer via the ATM service access point (ATM-SAP). In the ATM layer, a 5-byte ATM header is attached to form a 53-byte ATM cell, and then transmitted to another terminal or ATM switch through an optical transmission path of the physical layer.

That is, AAL type 1 protocol transmits U-SDU of equal bit rate at the same bit rate along with related time information, so that clock information of information source can be extracted at the receiving side, and at the convergence part layer, the bit for high quality video or audio signal Error correction function is provided, and the division and reassembly sublayer divides the CS-PDU and adds a 1-byte header to send it to the ATM layer.

Meanwhile, Table 4 below is a scheduling table of a partition and recombination (SAR) sublayer of an AAL layer according to the present invention.

One 2 3 One One 2 One 2 3 One One 2 One 3 One One 3 One 2 One 3 One One 2 One 3 One One One One 2 One 3 One 2 One 3 2 2 One 2 One One 2

Here, the scheduling table of Table 4 shows a case where the size is 100 as an example. The entry containing the number in Table 4 above is a valid entry (non-empty), and the entry with an empty number is an invalid entry. In addition, the entry of "1" shown in Table 4 is an entry assigned to the first connection, the entry of "2" is an entry assigned to the second connection, and the entry of "3" is an entry assigned to the third connection to be.

On the other hand, if the cell transmission rate of the link in the physical layer is ℓ, the bandwidth allocated to the first connection is And the bandwidth allocated to the second connection is And the bandwidth allocated to the third connection is to be. Therefore, the remaining bandwidth excluding the bandwidths of the first, second and third connections is to be.

Subsequently, when scheduling is performed according to the scheduling method of the present embodiment, the remaining bandwidth is equally divided to the first, second, and third connections in a ratio of 24: 12: 8 in proportion to the used bandwidth, thereby more efficiently without wasting bandwidth. It can be used as.

When the third connection is made inactive, the bandwidth allocated to the third connection and the remaining bandwidth are divided by a ratio of 12: 6 in proportion to the first and second connections.

Meanwhile, in the present embodiment, the remaining bandwidth which is not currently used is not used to transmit empty cells, but is used to transmit data of a currently active connection. Therefore, it is possible to reduce the waste of bandwidth by having the entry pointer indicate the next entry that has data to send on the scheduling table.

As such, there is an effect of equally dividing the remaining bandwidth that is not being used to transmit valid cells between active connections.

However, the process of finding the next entry with the data to send becomes quite complicated. That is, each time a cell to be serviced is selected, it is determined whether there is data to be sent by the connection corresponding to the next entry, and when there is no data to be sent, it is checked whether there is data to be sent by the connection corresponding to the next entry.

Using this approach, in the worst case, the hassle of checking every entry, and implementation makes it difficult to run the partitioning and recombination (SAR) sublayer at high speed. Therefore, in this embodiment, an idle cell removal block is installed between the split and recombination (SAR) sublayer and the physical layer, and operated at a high speed so that the idle cell is not sent down from the split and recombination (SAR) sublayer. To pay. This makes it easy to eliminate the hassle of checking whether there is data to send each time.

FIG. 4 is a block diagram illustrating an embodiment of an apparatus for efficiently utilizing residual bandwidth by removing idle cells in an AAL layer division and recombination (SAR) sublayer according to the present invention.

Here, the Utopia connection method is a standard connection method between the physical layer and the SAR layer proposed by the ATM forum. When transmitting from the SAR layer to the physical layer, the connection signal is "TxData [7: 0], TxSOC, / TxEnb, / TxFull, and TxClk". The connection signal upon reception from the physical layer to the SAR layer includes "RxData [7: 0], RxSOC, / RxEnb, / RxEmpty, and RxClk".

TxData [7: 0] is ATM cell data (hereinafter referred to as ATM cell transmission data or transmission data) in bytes transmitted from the SAR layer to the physical layer, and TxSOC is the start of the ATM cell from the SAR layer to the physical layer. (SOC: start of call) signal (hereinafter referred to as "transmission cell start signal"). If this signal is "high", the data input as transmission data (TxData [7: 0]) is ATM cell. This is the first byte of.

In addition, / TxEnb is to inform that the transmission data (TxData [7: 0]) transmitted from the SAR layer to the physical layer is valid cell data, and is valid for the transmission data (TxData [7: 0]). ) Stays "low" while data is present, and / TxFull is a signal to indicate that transmitted data in the physical layer is no longer full (referred to below as a transmission full signal). It will be activated when "low".

TxClk represents a transmission clock, and RxData [7: 0] is ATM cell data (hereinafter referred to as ATM cell received data or received data) transmitted in bytes from the physical layer to the SAR layer, and RxSOC is derived from the physical layer. It is a signal for notifying that the start of the ATM cell to the SAR layer (hereinafter referred to as a reception cell start signal). If this signal is "high", the byte data output as received data (RxData [7: 0]) is ATM. The first byte of the cell is indicated.

In addition, / RxEnb is to inform that the received data (RxData [7: 0]) transmitted from the physical layer to the SAR layer is valid cell data, while there is valid cell data in the received data (RxData [7: 0]). Remains "low" and / RxEmpty is a signal to indicate that the received data of the physical layer is empty and there is no more data to transmit (hereinafter referred to as a receive buffer beam signal). do.

In this case, the rate at which the cell data is sent down from the split and recombination (SAR) sublayer becomes larger than the actual physical layer data transmission rate, so that the remaining bandwidth can be more effectively used. As such, the remaining bandwidth can be utilized quite simply.

In addition, the operating speed of the idle cell removing unit 2 should be larger than the operating speed of the physical layer, and the larger the operating speed of the idle cell removing unit 2 can further utilize the remaining bandwidth.

FIG. 5 illustrates an embodiment of a method of efficiently using residual bandwidth by removing idle cells in a division and recombination (SAR) sublayer of an AAL layer according to the present invention.

On the other hand, instead of manually searching for a connection having cell data to be sent to select a cell to be serviced in the scheduling table of the partitioning and reassembly (SAR) sublayer, the cell data or When the idle cell is sent down, the residuals from the idle cell removal at the split and recombination (SAR) sublayer of the AAL layer, which reads the cell header at the interface between the split and recombination (SAR) sublayer and the physical layer, removes the idle cell. The efficient use of bandwidth is as follows.

First, in a first step S1, a cell header is read from the split and recombination (SAR) sublayer, and in a second step (S2), the cell header read in the first step (S1) is idle cell removing means ( 2), it is determined whether it is an idle cell, and in a third step S3, it is determined whether it is an idle cell in the second step S2.

In the fourth step S4, when the determination result in the third step S3 is an idle cell, the current cell is discarded. In the fifth step S5, the determination result idle cell is determined in the third step S3. If not, the current cell is transmitted to the physical layer. The operating speed of the idle cell removing means 2 should be larger than the operating speed of the physical layer, and the larger the speed, the more effectively the remaining bandwidth is used.

On the other hand, the reference numerals written in the components of the claims of the present application to facilitate the understanding of the present invention, and are not written in the intention to limit the technical scope of the present invention to the embodiments shown in the drawings. Further, various modifications can be made without departing from the scope of the invention.

Explained above

Claims (2)

Instead of looking for a connection that currently has cell data to be sent to select a cell to serve in the scheduling table of the partitioning and reassembly (SAR) sublayer, the cell data or idle cell is cycled through the scheduling table of the partitioning and reassembly (SAR) If you look down, the remaining bandwidth of the AAL layer that removes idle cells by reading the header of the cell at the interface between the split and recombination (SAR) sublayer and the physical layer In the efficient use method, A first step (S1) of reading a cell header from the division and recombination (SAR) sublayer; A second step (S2) of checking the cell header read in the first step (S1) by the idle cell removing means (2) to determine whether it is an idle cell; A third step S3 of determining whether it is an idle cell as a result of the determination in the second step S2; A fourth step S4 of discarding the current cell when the determination result in the third step S3 is an idle cell; In the sub-layer of the AAL layer, the fifth step (S5) of transmitting the current cell to the physical layer when the determination result in the third step (S3) is not an idle cell. Efficient Use of Residual Bandwidth by Idle Cell Removal. 2. The splitting and recombination of the AAL layer according to claim 1, wherein the operating speed of the idle cell removing means 2 must be larger than the operating speed of the physical layer, and the larger the speed, the more effective the use of the remaining bandwidth. Efficient Use of Residual Bandwidth by Idle Cell Removal at Sublayer.