JPH10336187A - Band assigning circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize bands between transmission devices and to relieve the load on a cell storing means, which is required for a packet re-configuration in the transmission devices by assigning the bands by means of cell unit to whole information sources, inspecting the kinds of cells which are transmitted from the information sources in accordance with it and assigning the bands by means of cell block unit to the information sources which transmits an information cell. SOLUTION: A cell kind detecting means 11 detects whether the kind of the cells transmitted from the information sources is an information cell, a null cell or a cell for management such as an OAM cell, etc. A cell unit assignment indicating means 12 indicates a band assignment by a cell unit in common with the location of the information sources for holding transmission waiting information and the band assignment for the OAM cell, etc. A cell block unit assignment indicating means 13 indicates the band assignment by a cell block unit. An indicating means selecting means 14 selects one of an assignment indicating means 12 or 13. An assignment indication combining means 15 transmits an assigning indication outputted from the assignment indicating means 12 or 13 to the information sources.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band allocating circuit for allocating a band for effectively using a transmission band in a system in which a plurality of devices (information sources) share a transmission band. As a system sharing a transmission band, for example, a subscriber line terminal unit (hereinafter referred to as "SLT") in a station
-Multipoint type ATM-PDS (Asynchronous Transfer Mode) in which two or more network terminating devices (hereinafter referred to as "ONUs") on the user side face each other and perform bidirectional communication.
-Passive Double Star) There is a transmission system in which a band allocation circuit provided in the SLT allocates a transmission band in a PDS section to a plurality of ONUs.

[0002]

2. Description of the Related Art A transmission apparatus for transmitting information from a plurality of information sources allocates a transmission band to each information source, and transmits short-division information called cells. This cell is a unit of cell unit usually called a packet, and the contents of the transmitted information can be grasped for the first time. Therefore, even if the transmission of information in units of cells is successful, if the transmission in units of packets fails, the transmitted cells are discarded or retransmitted because they have no meaning.

As a method of transmitting information in packet units, there is a CSMA / CD system used in LANs and the like, for example. In this method, it is necessary for each information source to be able to grasp whether or not the transmission band of the transmission device is occupied by another information source. If the information source cannot be grasped, the use efficiency of the transmission band becomes 18% or less, Not a practical method. In a method such as the token ring method in which each information source confirms whether or not each information source has a packet waiting to be transmitted, a transmission cell transmits an interrogation cell to the information source, and a reply cell is returned. Unable to allocate transmission band Therefore, the transmission bandwidth is wasted for the time of waiting for a reply, and when the transmission time between the transmission device and the information source is long, the effect is large. For example, in the case of an ATM-PDS transmission system, a reply waiting time of only one ONU requires 30 cells or more, and when information of 32 ONUs is transmitted, one packet is transmitted. As a result, the waiting time alone wastes more than 900 cells of transmission bandwidth, which is not a practical method.

[0004] Therefore, in an ATM-PDS transmission system or the like, since means similar to the CSMA / CD method or the token ring method cannot be applied, a packet transmission form as shown in FIG. 7 is adopted. In FIG. 7, a transmission device (for example, S
The cell unit band designating means 52 provided in the band allocating circuit 51 of the (LT) 50-1 includes an information source (for example, ONU) 60.
Are allocated in the order of the numbers assigned to the cells in cell units.
The packets held by each information source 60 are transmitted to the transmission device 50-1 in the order of the numbers assigned to the cells in cell units. The cell storage means 53 of the transmission device 50-1 accumulates the cells transmitted from each information source 60, forms them into packets, and transmits the packets to the next transmission device 50-2.

[0005] A method of transmitting the packet as it is without reconstructing it into a packet by the transmission device may be considered, but there is a problem that it is impossible to determine the loss of the cell constituting the packet.
Since the cell loss cannot be determined, the transmission band after the transmission device 50-1 may be wasted. Also, AT
AAL5 (ATM AdaptationLay) standardized by M
In er Type 5), cells of another packet must not be inserted between cells constituting a single packet, and it is difficult to transmit a packet without reconfiguring it.

[0006]

In the configuration shown in FIG.
The transmission device requires cell storage means having a storage amount capable of reconfiguring packets from all information sources. Further, the transmission device allows the transmission band to the next transmission device to be idle until the last cell of the packet arrives from each information source, and simultaneously transmits each packet after the last cell of the packet arrives from each information source. Form. This is a factor that hinders effective use of the bandwidth between the transmission devices. Further, when the output of the packet is delayed, the new storage capacity of the cell storage means decreases, and when the cell of the newly input packet cannot be accepted to the end, the already transmitted cell of the packet is discarded.

SUMMARY OF THE INVENTION The present invention provides a band allocation which can effectively use a band between transmission apparatuses and reduce a load on a cell storage unit required for packet reconfiguration in the transmission apparatus and can prevent transmitted cells from being wasted. It is intended to provide a circuit.

[0008]

SUMMARY OF THE INVENTION A band allocating circuit according to the present invention allocates a band on a cell basis to all information sources, checks the type of a cell transmitted from the information source accordingly, and transmits an information cell. A bandwidth in cell block units is allocated to the information source. That is, the information source that has transmitted the information cell is assumed to hold the information waiting for transmission.

The size of a cell block is determined by using the longest packet length transmitted by the information source, or an integer multiple of the longest packet length, or the window size that is the maximum length of a cell transmitted once by the information source. In addition, it is possible to easily reconfigure packets in the transmission device while effectively using the bandwidth between the transmission devices. Note that the information source may be configured to transmit a packet or a packet group that fits in the allocated band when the band is allocated in units of cell blocks.

[0010]

FIG. 1 shows an embodiment of a band allocation circuit according to the present invention. In the figure, cell type detecting means 11
Indicates whether the type of cell transmitted from the information source is an information cell,
It detects whether it is an empty cell without information or a cell for management of an OAM cell or the like.

The cell unit allocation instructing means 12 issues a band allocation instruction on a cell basis, which also serves as a search for an information source holding information waiting for transmission, and a band allocation instruction for an OAM cell or the like.
Here, the total bandwidth of the number of allocated cells according to the cell-based bandwidth allocation instruction that also serves as the search may be the minimum guaranteed bandwidth that is guaranteed to the information source at least. OAM
An ONU that does not send an OAM cell in response to a cell request may be regarded as dormant and may be excluded from searching for an information source that holds information waiting for transmission.

The cell block unit assignment instructing means 13 instructs, in accordance with the detection result of the cell type detecting means 11, a band assignment in cell block units to cause an information source holding information waiting for transmission to be transmitted in packet units. . The instructing means selecting means 14 selects either the cell unit assignment instructing means 12 or the cell block unit assignment instructing means 13 according to the detection result of the cell type detecting means 11. The allocation instruction merging unit 15 sends the allocation instruction output from the cell unit allocation instruction unit 12 or the cell block unit allocation instruction unit 13 to the information source.

(First Control Example of Bandwidth Assignment Circuit of the Present Invention)
FIG. 2 shows a first control example of the band allocation circuit of the present invention.
The instructing means selecting means 14 selects the cell unit assignment instructing means 12 since it does not recognize the information source holding the information waiting for transmission at the start of communication, and allocates the bandwidth of one cell to all information sources (S1). ). When a cell transmitted from each information source arrives due to this band allocation (S2), the cell type detection means 11 detects the information type of the cell, and the information source which has transmitted the information cell and the information source which has transmitted other cells (S3). Here, the information source that has transmitted the information cell is regarded as having a packet to be transmitted, and if there are a plurality of such information sources, they are held.

If there is an information source which has transmitted the information cell, the instruction means selecting means 14 designates the cell block unit allocation instructing means 13
Is selected, and a band in a cell block unit is allocated to the information source (S4). If there are a plurality of information sources that have transmitted the information cells, the bandwidth in cell block units is sequentially allocated to those information sources (S5, S4). When there is no information source to which a band in cell block units is allocated, the band is again allocated to all information sources in cell units (S1).

[0015] When there are a plurality of information sources that have transmitted information cells, in order to fairly allocate the bandwidth to each information source, for example, bandwidth allocation is performed from an information source with a small number of allocations within a certain period of time. Alternatively, bandwidth allocation may be performed preferentially from an information source that has allocated only a bandwidth equal to or less than the minimum guaranteed bandwidth within a certain period of time.
If there is an information source having the same number of times of assignment, the priority may be determined according to a predetermined priority or may be changed according to the priority which is changed each time. Also, an upper limit may be set for the product of the number of times of allocation and the allocated bandwidth.

The size of the cell block is defined as the longest packet length transmitted by the information source, or an integer multiple of the longest packet length, or the window size which is the maximum length of a cell transmitted each time by the information source such as a computer. Is also good.
For example, the longest packet length of a general LAN is 1500 bytes or 9180 bytes, and the window size for file transfer with a general personal computer or workstation is 8 kbytes, 12 kbytes or 64 kbytes.

The size of the cell block is not fixed, but is set to a value obtained by subtracting the cell (one cell in the above example) which has already been allocated by the cell unit allocation instructing means 12 for searching or the like. Good. Conversely, the size may be added to the information source to which the transmission band is assigned by adding one cell in order to confirm the presence or absence of the remaining transmission information. In addition, the information source memorizes the band that was actually transmitted together in the past,
The size of the cell block may be dynamically changed by recognizing the window size of the information source or the amount of information for the allocated band. On the other hand, when the bandwidth is allocated in units of cell blocks, the information source may transmit a packet or a packet group that fits in the allocated bandwidth.

Further, in the control example of FIG. 2, after the bandwidth allocation to the information sources to which the bandwidth is allocated in units of cell blocks is completed (S4, S5), the search for the bandwidth allocation to all the information sources (S1). However, for information sources that may hold information, it is regularly investigated whether or not information that is waiting to be transmitted is held. Band allocation may be performed.
This is effective when the size of the cell block is large.

Further, since it takes time from the start of the search until the search result is known, the search for the band allocation is performed during the time when the bandwidth is allocated to a plurality of information sources in units of cell blocks or at a predetermined timing. May be started. Thereby, for example, in the case of the ATM-PDS transmission system, if the search for the allocation after 32 cells is performed, the waiting time for 32 cells is effectively used.
It is possible to effectively use a band of up to 32 cells from the band allocation to the arrival of the cell. For this search or when it is necessary to interrupt the band allocation due to a fixed cell position such as an OAM cell used in a certain type of PDS transmission system, the cell block unit allocation instructing means 13 is used. Suspends only the necessary bandwidth allocation by
Bandwidth allocation may be resumed after the cause of the interruption is resolved.

Here, an operation example when the band allocation circuit according to the control example of FIG. 2 is used for the SLT of the ATM-PDS transmission system will be described. The number of ONUs is 32 and the transmission speed is 150Mb
It / s. At the start of communication, a band is allocated to each ONU one cell at a time. If no information cell is returned from any ONU, the bandwidth is again allocated to each ONU one cell at a time. When information cells are returned from all ONUs, a bandwidth in cell block units is sequentially allocated to each ONU. When information cells are returned from some of the ONUs, the ONUs that have returned the information cells are sequentially allocated a bandwidth in cell block units. Here, assuming that the cell block size is 33 cells, the band allocation to all ONUs ends.
After 1056 cells (approximately 3 milliseconds), band allocation to 16 ONUs ends after 528 cells (approximately 1.5 milliseconds). In an ATM-PDS transmission system that is not variable in bandwidth,
The frame, which is the cycle of cell allocation, is fixed at 3 ms or the like, but when the band allocation circuit of the present invention is used, the length becomes variable, such as 0.1 to 3 milliseconds, when the concept of frame length is applied.

When the present invention is applied to the concept of a fixed frame, the cell block unit used by the cell block unit assignment instructing means 13 may be assigned a band from a band in the frame to an essential band such as an OAM cell. With the exception of the bandwidth required for the allocation of the minimum unit to the information source, the bandwidth is allocated to the information source that holds the information waiting to be transmitted in packet units or is equally divided.

(Second Control Example of Bandwidth Assignment Circuit of the Present Invention)
FIG. 3 shows a second control example of the band allocation circuit of the present invention.
The feature of this control example is that the instruction unit selecting unit 14 selects the cell block unit allocation instruction unit 13 and performs band allocation in cell block units for one information source that has transmitted information cells (S4). The search is to be performed by allocating the bandwidth in units of cells to all information sources (S1). Thus, even when there are a plurality of information sources that hold information waiting to be transmitted, it is not necessary to hold the information sources, and the search cycle can be shortened.

(Third Control Example of Bandwidth Assignment Circuit of the Present Invention)
FIG. 4 shows a third control example of the band allocation circuit of the present invention.
In the second control example, the cell unit allocation instructing means 12 performs the band allocation for one cell. However, the present control example is characterized in that the band allocation for three cells is performed (S11). In this case, the information source determines whether or not there is a packet to be transmitted based on the cell type of the third cell (S13). Thereby, W
It is possible to avoid a situation in which more transmission bandwidth is allocated to information of 64 bytes corresponding to the transmission amount of frequently transmitted commands such as pressing down a button of WW access, that is, an information source holding only two cells. . Another corresponding control example is shown in FIG. 6 as a fifth control example.

(Fourth Control Example of Bandwidth Assignment Circuit of the Present Invention)
FIG. 5 shows a fourth control example of the band allocation circuit of the present invention.
This control example is characterized in that the instruction unit selecting unit 14 selects the cell block unit allocation instructing unit 13 and performs band allocation in cell block units for one information source that has transmitted an information cell to the third cell. (S13, S4), a search is performed by allocating a bandwidth of three cells to all information sources (S11). Thus, even when there are a plurality of information sources that hold information waiting to be transmitted, it is not necessary to hold the information sources, and the search cycle can be shortened.

(Fifth Control Example of Bandwidth Assignment Circuit of the Present Invention)
FIG. 6 shows a fifth control example of the band allocation circuit of the present invention.
The instructing means selecting means 14 selects the cell-based allocation instructing means 12 at the start of communication, allocates a band for one cell to all information sources (S1), and the cell type detecting means 11 returns information cells. An information source is detected (S2, S3). Up to this point, the control is the same as in the first control example.

Next, the cell unit allocation instructing means 12 allocates the bandwidth of two cells to the information source which has returned the information cell (S21). At this time, if the number of information sources that have returned information cells is small, band allocation for one cell may be performed again for information sources that have not returned information cells. The cell type detecting means 11 detects whether or not both cells are information cells for the information type of the cell returned from the information source to which the band for two cells is allocated (S22). If both cells are not information cells, it is considered that only 64-byte information (for two cells) is held as described above. If both cells are information cells, it is regarded as a packet exceeding the information of 64 bytes, and the instruction means selecting means 14 selects the cell block unit assignment instructing means 13 and sends the cell block to the information source. Band allocation is performed in units (S23). When there are a plurality of information sources to which the bandwidths of two cells are allocated, the bandwidth allocation is similarly performed in cell blocks for the information sources that have returned the information cells in both cells (S24, S22, S2).
3). When there is no information source for which band allocation is performed in cell block units, band allocation for one cell is performed again for all information sources (S1).

In the case of the present control example, a 64-byte packet is allocated in the same manner as the method of allocating the band of three cells first and detecting the cell type of the third cell as shown in the third and fourth control examples. Can be avoided.
As a countermeasure similar to this, in band allocation in cell block units, only 1500 bytes or 1500 bytes + 1 cell is first allocated, and only 8 k
A window size of any of bytes, 9180 bytes, 12 kbytes, and 64 kbytes may be allocated.

[0028]

As described above, the band allocating circuit according to the present invention makes it possible to allocate a band in units of cell blocks by identifying the cell type of the cell transmitted from the information source. As a result, it is possible to effectively use the band between the transmission devices, reduce the load on the cell storage means required for packet reconfiguration in the transmission device, and avoid transmission of useless cells.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a band allocation circuit of the present invention.

FIG. 2 is a flowchart showing a first control example of the band allocation circuit of the present invention.

FIG. 3 is a flowchart showing a second control example of the band allocation circuit of the present invention.

FIG. 4 is a flowchart showing a third control example of the band allocation circuit of the present invention.

FIG. 5 is a flowchart showing a fourth control example of the band allocation circuit of the present invention.

FIG. 6 is a flowchart showing a fifth control example of the band allocation circuit of the present invention.

FIG. 7 is a diagram showing a conventional packet transmission form in an ATM-PDS transmission system or the like.

[Explanation of symbols]

 Reference Signs List 11 Cell type detecting means 12 Cell unit allocation instructing means 13 Cell block unit allocation instructing means 14 Instruction means selecting means 15 Allocation instruction merging means

Claims (13)

[Claims] 1. A band allocating circuit for allocating a transmission band shared by a plurality of information sources to each information source, wherein a cell unit allocating a cell unit band allocation instruction to search for an information source holding information waiting for transmission. Instructing means, a cell type detecting means for detecting whether or not the cell type transmitted from the information source according to the cell-based band allocation is an information cell, and an information cell according to the cell-based band allocation Cell block unit allocation instructing means for instructing the transmitted information source to perform band allocation in cell blocks for transmission in packet units, and information for holding information awaiting transmission according to a detection result of the cell type detecting means A cell block unit assignment instructing unit or a finger for selecting the cell unit assignment instructing unit for each information source. Bandwidth allocation circuit characterized by comprising: means selecting means, and assignment instructions merging means for sending allocation indication to the source that is output from the cell unit assignment instruction means or the cell block assignment instruction means. 2. The bandwidth allocating circuit according to claim 1, wherein the instruction means selecting means and the cell block unit allocation instructing means, when there are a plurality of information sources holding information waiting to be transmitted, transmit all the information sources. A band allocation circuit for performing band allocation on a cell block basis in a predetermined order. 3. The bandwidth allocating circuit according to claim 1, wherein the instruction unit selecting unit, the cell unit allocation instruction unit, and the cell block unit allocation instruction unit include: It is characterized in that band allocation is performed on a cell block basis for all of the information sources, and band allocation is performed on a cell basis for an information source which may hold information waiting for transmission at a predetermined timing. Band allocation circuit. 4. The band allocation circuit according to claim 2, wherein the order of information sources for performing band allocation in units of cell blocks is the order of the number of allocations within a predetermined time, or the allocation within a predetermined time. A band allocating circuit, wherein the band allocating circuit is determined in accordance with the order of the product of the number of times and the allocated bandwidth, or the priority, or a combination of at least two of the above. 5. The band assignment circuit according to claim 1, wherein the cell block unit assignment instructing means assigns a cell having a fixed cell position to a cell block while band assignment is being performed on a cell block basis. A band allocating circuit having a function of interrupting band allocation for each cell block for transmission. 6. The band allocation circuit according to claim 1, wherein the size of the cell block allocated by the cell block unit allocation instruction means is the longest packet length transmitted by the information source or the longest packet length. A bandwidth allocating circuit having a window size that is an integral multiple of a packet length or a maximum length of a cell transmitted each time by an information source. 7. The bandwidth allocation circuit according to claim 1, wherein the size of the cell block allocated by the cell block unit allocation instructing means is the longest packet length or the longest packet length transmitted by the information source. A bandwidth allocating circuit having a size obtained by subtracting, from an integer multiple of the packet length or a window size, cells already allocated by the cell unit allocation instructing means for a search or the like. 8. The band allocation circuit according to claim 1, wherein the size of the cell block allocated by the cell block unit allocation instruction means is the longest packet length transmitted by the information source or the longest packet length. Bandwidth allocation characterized by adding an integer multiple of the packet length or a window size to a cell to be newly searched by subtracting cells already allocated by search or the like by cell unit allocation instructing means to a cell size. circuit. 9. The band allocation circuit according to claim 6, wherein the size of the cell block allocated by the cell block unit allocation instructing means is determined by a band which the information source actually transmitted in the past in a collective manner. A bandwidth allocating circuit, which is determined according to the condition. 10. The band allocation circuit according to claim 6, wherein the longest packet length is 1500 bytes or 9180 bytes. 11. The bandwidth allocation circuit according to claim 6, wherein the window size is 8 kbytes or 12 kbytes,
Or a bandwidth allocating circuit having a capacity of 64 kbytes. 12. The band allocating circuit according to claim 1, wherein the band allocated by the cell unit allocation instruction means is one cell, two cells, or three cells. 13. The band allocation circuit according to claim 12, wherein when the band allocated by the cell unit allocation instructing unit is three cells, the instruction unit selecting unit and the cell block unit allocation instructing unit are all three cells, or A band allocation circuit for performing band allocation in cell block units for an information source in which a third cell is detected as an information cell.