JP3686498B2 - Bandwidth allocation circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bandwidth allocation circuit that assigns a transmission band fairly to each information source in a system that shares a transmission band with a plurality of information sources.
As a system sharing a transmission band, for example, a subscriber line terminal station device (hereinafter referred to as “SLT”) in a station and a plurality of network termination devices (hereinafter referred to as “ONU”) on the user side face each other for bidirectional communication. There is a point-multipoint ATM-PDS (Asynchronous Transfer Mode-Passive Double Star) transmission system in which the band allocation circuit provided in the SLT allocates the transmission band of the PDS section to a plurality of ONUs.
[0002]
[Prior art]
In the ATM-PDS transmission system, a plurality of ONUs 53 bundled by a star coupler 52 are connected to an SLT 51 as shown in FIG. Further, a transmission network such as a plurality of terminals 55 and a LAN 56 is connected to each ONU 53 via, for example, a line concentrator (HUB) 54. Here, a portion between the SLT 51 and the ONU 53 is referred to as a PDS section.
[0003]
In such a configuration, the transmission band in the PDS section needs to be shared by the plurality of ONUs 53. For this purpose, there is a method in which the bandwidth allocation circuit 57 of the SLT 51 allocates a bandwidth to each ONU 53. One of them is a method in which the ONU 53 requests a bandwidth from the SLT 51, and the SLT 51 allocates a bandwidth in response to the request. . As the ATM-PDS transmission system including the band allocation circuit 57, Reference 1 “Discussion of Distributed Control ATM Optical Subscriber Transmission System”, IEICE Technical Report CS89-12, and Reference 2 “Distribution Control ATM Optical Subscriber” "Transmission system", IEICE Transactions BI, vol. J73-B-1, No.5, pp.470-478, 1990).
[0004]
FIG. 12 shows the concept of a conventional bandwidth allocation method.
The band allocation circuit 57 of the SLT 51 takes a method of receiving a band request from each ONU 53 and sequentially storing it in the band request storage means 58 and allocating the band in the received order.
[0005]
[Problems to be solved by the invention]
By the way, in the bandwidth allocation method shown in FIG. 12, when a certain ONU requests a large amount of bandwidth all at once, the bandwidth request of another ONU is waited without being processed until the request is processed. When the storage capacity of the request storage unit 58 is exceeded, there is an unfairness that a bandwidth request of another ONU is discarded.
[0006]
In addition, an ONU that does not actually transmit information makes a bandwidth request to occupy the bandwidth, and other ONU bandwidth requests may not be accepted.
As a countermeasure against these situations, a method of providing a bandwidth request receiving unit and setting the upper limit of the request reception amount per fixed time is considered. This measure is effective in a situation where a large number of ONUs requesting bandwidth are connected and each ONU always requests bandwidth. However, if there are a small number of ONUs requesting bandwidth, the bandwidth that cannot be used effectively increases because the amount of requests accepted is set low, and the bandwidth that cannot be used increases even if the bandwidth is free.
[0007]
It is an object of the present invention to provide a bandwidth allocation circuit that allows a SLT to allocate a bandwidth to each ONU fairly and efficiently in response to a bandwidth request from the ONU in an ATM-PDS transmission system sharing the bandwidth of the PDS section. Objective.
[0008]
[Means for Solving the Problems]
The bandwidth allocation circuit of the present invention accumulates each bandwidth request corresponding to the request source, and allocates a certain amount of bandwidth for each request source to the accumulated bandwidth request. Alternatively, a bandwidth request that can be transmitted within a bandwidth allocation time corresponding to a predetermined reception time is stored corresponding to the reception time, and a certain amount of bandwidth is allocated to the stored bandwidth request for each reception time. Or, it has both functions. Thereby, fair bandwidth allocation can be realized for a plurality of information sources.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows a first embodiment of the bandwidth allocation circuit of the present invention.
In the figure, the bandwidth allocation circuit comprises request individual management means 11, bandwidth request storage means 21, and request permission means 31. The bandwidth request sent from each ONU is input to the request individual management unit 11, grasps the requesting ONU, is transferred to the bandwidth request accumulation unit 21, and is accumulated. The request permission means 31 reads the bandwidth requests stored in the bandwidth request storage means 21 in order by a fixed amount for each request source, and assigns the bandwidths in the reading order. Thereby, the waiting time until the request is permitted in the bandwidth request accumulating means 21 can be averaged among all the request sources to be fair. This reading order may be always constant, or the reading order may be changed every time a fixed time elapses.
[0010]
Here, in order to grasp the request source of the bandwidth request read by the request permission unit 31 from the bandwidth request storage unit 21, a tag that identifies the request source may be attached to the bandwidth request, or the bandwidth request storage unit 21. May be stored separately for each request source.
Further, the storage amount of the bandwidth request storage means 21 may be virtually unlimited or an upper limit may be set. Setting the upper limit of the accumulation amount corresponds to setting the upper limit of the delay time from the request to the allocation. That is, since the bandwidth request exceeding the upper limit cannot be stored and is discarded, the bandwidth allocation notification is not returned within a predetermined time from the viewpoint of the request source. This is suitable for communication such as TCP / IP, which is regarded as a communication failure when a communication completion notification is not returned within a certain time.
[0011]
Further, when the upper limit of the accumulation amount is determined, it may be determined individually for each request source. In this case, an unfairness in which a certain request source requests a large amount of bandwidth and exceeds the capacity of the bandwidth request storage means 21 and a bandwidth request from another request source cannot be accepted can be solved.
When a bandwidth request is transmitted from the ONU to the SLT, the request value is written in a part of the upstream bandwidth. The area to be described may be an unused area of about 30 bytes of the uplink PDS-OAM cell, an unused area of the cell overhead, or a dedicated cell.
[0012]
(Second Embodiment)
FIG. 2 shows a second embodiment of the bandwidth allocation circuit of the present invention.
In the figure, the bandwidth allocation circuit is composed of reception time management means 41, bandwidth request storage means 22, and request permission means 32. The bandwidth request transmitted from each ONU is input to the reception time management means 41, and the bandwidth request that can be transmitted within the bandwidth allocation time corresponding to the reception time divided in fixed time increments is passed to the bandwidth request storage means 22. Accumulated. The request permission unit 32 reads the bandwidth request stored in the bandwidth request storage unit 22 every reception time, and allocates the bandwidths in the order of reading.
[0013]
Here, when receiving the bandwidth request, the reception time management means 41 receives only a bandwidth request that can be transmitted within the allocatable bandwidth corresponding to the reception time, as shown in FIG. A bandwidth request exceeding the allocatable bandwidth is discarded unless there is no bandwidth request at the next reception time. Alternatively, a plurality of reception times may be grouped and a bandwidth request that can be allocated within the group may be received. The upper limit of the time interval or the total reception time of the group as a unit of each reception time may be less than the extent that the time from reception to allocation is determined as a communication failure by a higher-level protocol such as TCP / IP and retransmitted. When this upper limit is applied, information that cannot be transferred within a certain period of time can be applied to a device that conforms to a protocol such as TCP / IP to be retransmitted.
[0014]
The time increment of the reception time is 125 microseconds or an integral multiple thereof considered as a time unit for distributing cells in a frame to each device in the PDS transmission system, or the time required for transmission of 53 cells or an integral multiple thereof, or It may be 1 millisecond, 3 milliseconds, or an integer multiple thereof used in an existing PDS transmission system. When these time units are applied, there is an advantage that management can be performed for each frame.
[0015]
As a method of managing the reception time in the reception time management means 41, a tag that allows the reception time to be known may be attached, or the reception time is divided at regular intervals, and a bandwidth request is assigned to each divided time. It may be stored in the request storage means 22.
Further, the storage amount of the bandwidth request storage means 22 may be virtually unlimited or an upper limit may be set. Furthermore, the upper limit of the accumulation amount may be determined individually for each reception time. Setting the upper limit of the accumulation amount corresponds to setting the upper limit of the delay time from the request to the allocation. This is suitable for communication such as TCP / IP, which is regarded as a communication failure when a communication completion notification is not returned within a certain time. In addition, setting an upper limit for the reception amount per reception time means that a certain request source temporarily requests a large amount of bandwidth and exceeds the capacity of the bandwidth request storage means 22, and a bandwidth request of another request source is accepted. Unfairness that disappears can be resolved.
[0016]
A bandwidth request received within one reception time may be treated as having arrived at the same time. In this case, the bandwidth requests are arranged in an order that is fair for each request source. This treatment can solve the problem that an advantageous request source and an unfavorable request source always occur when a cell transmission timing is determined and the transmission order is fixed as in the PDS transmission system.
[0017]
(Third embodiment)
FIG. 4 shows a third embodiment of the bandwidth allocation circuit of the present invention.
The feature of this embodiment is that it includes a request individual / acceptance time management means 51 that combines the function of the request individual management means 11 in the first embodiment and the function of the reception time management means 41 in the second embodiment. By the way. Further, the band request accumulation unit 23 and the request permission unit 33 have a configuration corresponding to the request individual / acceptance time management unit 51 of the present embodiment.
[0018]
(Fourth embodiment)
FIG. 5 shows a fourth embodiment of the bandwidth allocation circuit of the present invention.
The feature of this embodiment is that, in addition to the configuration of the first embodiment, a use band notification unit 61 and a request discard unit 71 are provided, and the band request stored by the band request storage unit 24 is appropriately controlled by the control of the request discard unit 71. It is about to be discarded. The used bandwidth notification means 61 detects a request source having a transmission amount that differs from the transmission amount requested in the past and the actual transmission amount. The request discarding unit 71 controls the bandwidth request accumulating unit 24 so as to discard the bandwidth request corresponding to the difference from the actual transmission amount for the request source detected by the used bandwidth notification unit 61.
[0019]
(Fifth embodiment)
FIG. 6 shows a fifth embodiment of the bandwidth allocation circuit of the present invention.
A feature of the present embodiment is that, in addition to the configuration of the first embodiment, a use band notification unit 61 and a request discard unit 71 are provided, and the request permission unit 34 reads out from the band request accumulation unit 21 under the control of the request discard unit 71. The bandwidth request is appropriately discarded. The functions of the used band notification unit 61 and the request discard unit 71 are the same as those in the fourth embodiment.
[0020]
(Sixth embodiment)
FIG. 7 shows a sixth embodiment of the bandwidth allocation circuit of the present invention.
A feature of the present embodiment is that, in addition to the configuration of the first embodiment, a use band notification unit 61 and a request discard unit 71 are provided, and the request individual management unit 12 is added to the band request accumulation unit 21 by the control of the request discard unit 71. The bandwidth request to be transferred is to be discarded appropriately. The functions of the used band notification unit 61 and the request discard unit 71 are the same as those in the fourth embodiment. In the present embodiment, since a useless bandwidth request is discarded before storage, the capacity of the bandwidth request storage means 21 can be used effectively.
[0021]
(Seventh Embodiment, Eighth Embodiment, Ninth Embodiment)
In the fourth to sixth embodiments described above, the use band notification means 61 and the request discarding means 71 are added to the first embodiment while changing their connection positions. As shown in FIG. 10, it can be similarly applied to the third embodiment.
[0022]
The bandwidth request accumulation means 25 of the seventh embodiment shown in FIG. 8 appropriately discards the bandwidth requests accumulated under the control of the request discarding means 71. The request permission means 35 of the eighth embodiment shown in FIG. 9 appropriately discards the bandwidth request read from the bandwidth request accumulation means 21 under the control of the request discarding means 71. The request individual / acceptance time management means 52 of the ninth embodiment shown in FIG. 10 appropriately discards the bandwidth request delivered to the bandwidth request storage means 21 under the control of the request discarding means 71.
[0023]
【The invention's effect】
As described above, the bandwidth allocation circuit of the present invention can realize fair bandwidth allocation for a plurality of information sources. In particular, in the configuration in which the bandwidth request is processed by separating the reception time, it is possible to avoid a situation in which a large amount of bandwidth requests are received and a long time bandwidth cannot be allocated to the information source that subsequently made the bandwidth request. it can.
[0024]
Further, by discarding the bandwidth request according to the difference from the actual transmission amount for each information source (request source), other information sources cannot receive bandwidth allocation due to information sources that occupy the transmission bandwidth unnecessarily. The disadvantage can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a bandwidth allocation circuit of the present invention.
FIG. 2 is a block diagram showing a second embodiment of the bandwidth allocation circuit of the present invention.
FIG. 3 is a diagram for explaining the operation of reception time management means 41;
FIG. 4 is a block diagram showing a third embodiment of the bandwidth allocation circuit of the present invention.
FIG. 5 is a block diagram showing a fourth embodiment of the bandwidth allocation circuit of the present invention.
FIG. 6 is a block diagram showing a fifth embodiment of the bandwidth allocation circuit of the present invention.
FIG. 7 is a block diagram showing a sixth embodiment of the bandwidth allocation circuit of the present invention.
FIG. 8 is a block diagram showing a seventh embodiment of the bandwidth allocation circuit of the present invention.
FIG. 9 is a block diagram showing an eighth embodiment of the bandwidth allocation circuit of the present invention.
FIG. 10 is a block diagram showing a ninth embodiment of the bandwidth allocation circuit of the present invention.
FIG. 11 is a diagram showing a configuration example of an ATM-PDS transmission system.
FIG. 12 is a diagram for explaining the concept of a conventional bandwidth allocation method.
[Explanation of symbols]
11, 12 Request individual management means 21, 22, 23, 24, 25 Bandwidth request accumulation means 31, 32, 33, 34, 35 Request permission means 41 Reception time management means 51, 52 Request individual / acceptance time management means 61 Bandwidth used Notification means 71 Request discarding means

Claims (10)

In a bandwidth allocation circuit that allocates a transmission band shared by a plurality of information sources according to a bandwidth request from each information source,
Request individual management means for receiving the bandwidth request by grasping the request source; and
Bandwidth request accumulation means for accumulating the bandwidth request received by the request individual management means in response to the request source;
The accumulated bandwidth request in the bandwidth request storage means, read by a constant amount for each request source, bandwidth allocation circuit which is characterized in that a request permitting means for allocating a bandwidth to the read order. In a bandwidth allocation circuit that allocates a transmission band shared by a plurality of information sources according to a bandwidth request from each information source,
Reception time management means for receiving a bandwidth request that can be transmitted within a bandwidth allocation time corresponding to a predetermined reception time;
Bandwidth request storage means for storing the bandwidth request received by the reception time management means in correspondence with the reception time;
Wherein the accumulated bandwidth request in the bandwidth request storage means, reading every reception time, bandwidth allocation circuit which is characterized in that a request permitting means for allocating a bandwidth to the read order. In a bandwidth allocation circuit that allocates a transmission band shared by a plurality of information sources according to a bandwidth request from each information source,
Request individual / acceptance time management means for accepting a bandwidth request that can be transmitted within a bandwidth allocation time corresponding to a predetermined acceptance time by grasping the request source;
Bandwidth request accumulation means for accumulating the bandwidth request received by the request individual / acceptance time management means in correspondence with the request source and the reception time;
The accumulated bandwidth request in the bandwidth request storage means, read by a constant amount for each request source and reception time, bandwidth allocation circuit which is characterized in that a request permitting means for allocating a bandwidth to the read order. In the band allocation circuit according to claim 1 or 3,
A bandwidth allocation circuit characterized in that an upper limit is set for the amount of bandwidth request accumulation means as a whole or for each request source. In the band allocation circuit according to claim 2 or claim 3,
A bandwidth allocation circuit characterized in that an upper limit is set for the amount of bandwidth request accumulation means as a whole or for each reception time. In the band allocation circuit according to claim 2 or claim 3,
Time step that defines reception time is 125 microseconds, integer multiple of 125 microseconds, 1 millisecond, 3 millisecond, integer multiple of 1 millisecond or 3 milliseconds, 53 cell transmission time, 53 cell transmission A bandwidth allocation circuit characterized by being an integral multiple of the time required for. In the band allocation circuit according to claim 1 or 3,
Used bandwidth notification means for detecting a request source whose actual transmission amount differs from the transmission amount requested in the past;
A request discarding means for controlling the bandwidth request storage means so as to discard the bandwidth request according to the difference from the actual transmission amount for the request source detected by the used bandwidth notification means. Allocation circuit. In the band allocation circuit according to claim 1 or 3,
Used bandwidth notification means for detecting a request source whose actual transmission amount differs from the transmission amount requested in the past;
Bandwidth allocation comprising: a request discarding unit that controls a request permitting unit to discard a bandwidth request corresponding to a difference from an actual transmission amount with respect to a request source detected by the used band notification unit circuit. The bandwidth allocation circuit according to claim 1, wherein
Used bandwidth notification means for detecting a request source whose actual transmission amount differs from the transmission amount requested in the past;
A request discarding means for controlling the request individual management means so as to discard the bandwidth request according to the difference from the actual transmission amount for the request source detected by the used bandwidth notification means. Allocation circuit. The bandwidth allocation circuit according to claim 3 ,
Used bandwidth notification means for detecting a request source whose actual transmission amount differs from the transmission amount requested in the past;
Request discarding means for controlling the request individual / acceptance time management means so as to discard the bandwidth request according to the difference from the actual transmission amount for the request source detected by the used bandwidth notification means. A bandwidth allocation circuit.

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