JP3561163B2 - ATM communication network - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is used for an ATM (Asynchronous Transfer Mode). The present invention provides an AAL2 for ensuring communication quality for traffic in which a plurality of higher-level connections such as AAL2 (ATM Adaptation Layer type 2) such as low-speed voice share a single virtual channel (hereinafter, referred to as VC). Related to bandwidth management technology.
[0002]
[Prior art]
ATM (Asynchronous Transfer Mode) has been developed mainly as a communication system that uniformly carries various traffic at high speed. In recent years, a need has arisen to carry traffic such as low-speed voice using ATM. This is due to an increase in low-speed voice traffic centered on a mobile object, voice compression on a private network accompanying the development of coding technology, and the like.
[0003]
If the low-speed voice is transferred by the ATM using the existing method, the delay of cellization and decellularization becomes too large, which is not practical. Thus, a new ATM adaptation layer called AAL2 has been considered. In AAL2, one VC connection is shared by a plurality of AAL2 connections. One AAL2 connection usually accommodates one audio channel. That is, an appropriate header is added to the audio signal burst of each audio channel, the CPS packet is formed as a variable length information block, and a plurality of CPS packets are accommodated in one cell. For example, cellization is performed at a mobile communication base station (BS). The BS accommodates a plurality of voice channels.
[0004]
The cell is decomposed into CPS packets at the AAL2 switching node in the network as needed, and the combination is changed, and the cell is accommodated again in the cell. At the receiving end, the cells are decomposed into CPS packets and sent to each voice channel as a voice burst. Regarding AAL2, see, for example, literatures, Kazuhiko Nagata, Hiroshi Fujitani, "Low bit rate voice communication technology by AAL2," NTTR & D, 46, 11, pp. 147-64. 1181-1188 (1997).
[0005]
The ATM performs admission control in order to guarantee communication quality. This is intended to prevent excessive traffic (cell flow) from flowing into a limited band. In AAL2, the traffic increases and decreases according to the increase and decrease of AAL2 connections such as low-speed voice. This increases or decreases even if the ATM connection is constant. Therefore, it is considered that AAL2 connection admission control is necessary.
[0006]
The accommodation determination is performed based on the traffic characteristics (peak, average, etc.) of the AAL2 connection. These are considered to be the same as the determination of the acceptance of the ATM connection. Normally, the AAL2 reception control gives a certain band to a VC, and determines whether or not an AAL2 connection accommodated in the VC can be accommodated in the same band. Cells in the accommodated VC are transmitted from the VC endpoint (cell transmitting end) in the above-mentioned fixed band.
[0007]
FIG. 6 shows a conventional AAL2 end system. FIG. 7 shows a network configuration example. In the conventional AAL2 end system, as shown in FIG. 6, CPS packets are generated by encoders 21 to 23 provided for each audio source, and the CPS packets are converted into cells by a cellizer 27. The transmission queue 98 is provided for VC, and the cell transmission scheduler 99 extracts cells from the transmission queue 98 at a speed corresponding to the VC band. As described above, in the conventional AAL2 end system, the transmission queue 98 is provided for each cellifier 27, and cells are transmitted according to the VC band instead of the VP band.
[0008]
As shown in FIG. 7, cells transmitted from the AAL2 end system 35 to the AAL2 end system 37 are VP42, VP handler 41, VC handler 39, VP43, AAL2 switching node 38, VP44, VC handler 40, VP45, AAL2 end system. 37. During this time, cell transfer is performed using a VC to which a certain band is allocated.
[0009]
[Problems to be solved by the invention]
According to the above prior art, cell transfer is performed using a VC to which a certain band is allocated. However, one VC can accommodate only a maximum of 256 AAL2 connections. Therefore, when accommodating 256 or more AAL2 connections, another VC must be prepared. Also, the statistical multiplexing effect is limited within the VC. For this reason, traffic accommodation efficiency does not become very high. The above description can be similarly applied to the case where VP is replaced with a transmission path.
[0010]
The present invention has been made under such a background, and has as its object to provide an ATM communication network capable of increasing the number of cells that can be transferred per predetermined VP band. An object of the present invention is to provide an ATM communication network that can increase the number of cells that can be transferred per predetermined transmission path band.
[0011]
[Means for Solving the Problems]
According to the present invention, a certain band is not provided to a VC, but a certain band is provided to a VP accommodating a VC (or a transmission path; hereinafter, a case of a VP), and an AAL2 connection can be accommodated in the VP. It is determined whether or not. For this purpose, the VC handler has an AAL2 connection admission control function. Further, the VP endpoint (cell transmitting end) transmits cells to the cells belonging to the VP in the fixed band.
[0012]
That is, the present invention relates to an ATM communication network, which includes a VP between a transmitting end and a receiving end of a cell, and between the transmitting end and the receiving end via a VC set on the VP. This is an ATM communication network that includes means for transferring cells and whose VC is set to be sharable by a plurality of higher-level connections.
[0013]
Here, the feature of the present invention resides in that the means for performing the transfer includes means for variably allocating a part of the band of the VP to the upper connection in accordance with the number of upper connections set in the VP. is there.
[0014]
As described above, by variably allocating a part of the VP band to the upper connection within the range of the VP band, cells can be transferred using the minimum necessary VP band. Therefore, more cells can be efficiently transferred to a smaller VP band as compared with the conventional example.
[0015]
It is preferable to include means for estimating the bandwidth allocated by the allocating means in accordance with the number of higher-level connections set in the VP, and means for determining whether or not to accept cell transfer according to the estimation result of the estimating means.
[0016]
In this way, by estimating the capacity of the VP, it is possible to determine whether or not the cell transfer can be accepted, and to eliminate cell discard during the transfer.
[0017]
In order to realize the present invention, it is desirable to provide a transmission waiting queue corresponding to the VP. Further, the upper connection may be an AAL2 connection.
[0018]
An upper limit value can be set for the VP band. Alternatively, an upper limit may not be set for the band of the VP, and an upper limit may be set for the band of the transmission path including the VP. As a result, the bandwidth of the transmission path can be provided for other uses, and the bandwidth can be effectively used.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a main part of an AAL2 end system according to an embodiment of the present invention. FIG. 2 is a block diagram of a main part of the AAL2 switching node according to the embodiment of the present invention. FIG. 3 is a block diagram of a main part of the VC handler according to the embodiment of the present invention.
[0020]
The present invention is an ATM communication network, as shown in FIG. 7, including VPs 42, 43, 44, 45 between an AAL2 end system 35 which is a transmitting end of a cell and an AAL2 end system 37 which is a receiving end, A VP handler 41, a VC handler 39, 40, and an AAL2 exchange, which are means for transferring cells between the AAL2 end system 35 and the AAL2 end system 37 via the VCs set on the VPs 42, 43, 44, and 45. The ATM communication network includes a node 38 and its VC is set to be sharable by a plurality of AAL2 connections, which are upper-level connections.
[0021]
Here, the feature of the present invention is that the AAL2 end systems 35 and 37 shown in FIG. 1, the VC handlers 39 and 40 shown in FIG. 3, and the AAL2 switching node 38 shown in FIG. And a cell transmission scheduler 30, 73, 74, 88, 89, which is a means for variably assigning a part of the bandwidth of the VPs 42, 43, 44, 45 to the AAL2 connections according to the number of AAL2 connections set in the It is in.
[0022]
The AAL2 switching node 38 shown in FIG. 2 and the VC handlers 39, 40, 47 shown in FIG. 3 are adapted to transmit the cell transmission schedulers 30, 73, 74, 88, 89 according to the number of AAL2 connections set in the VPs 42, 43, 44, 45. , And acceptance determination devices 75, 76, 84, and 85, each of which is a means for estimating the acceptability of cell transfer according to the estimation result.
[0023]
The AAL2 end systems 35 and 37 shown in FIG. 1, the AAL2 switching node 38 shown in FIG. 2, and the VC handlers 39, 40 and 47 shown in FIG. Is provided.
[0024]
In the embodiment of the present invention, upper limits are set for the bands of the VPs 42, 43, 44, and 45. As another example, an upper limit value may be set for the band of the transmission path including the VP. In this case, the VP handler requires the same device as the VC handler. Since this can be easily inferred, the description is omitted.
[0025]
【Example】
An embodiment of the present invention will be described with reference to a network configuration example of FIG. The network typically has an AAL2 end system that accommodates multiple audio sources. If there is no AAL2 switching node between AAL2 end systems, they are directly connected by a VC connection. If there is an AAL2 switching node 38 in the middle as in the network of FIG. 7, a VC is established between the AAL2 end systems 35, 36, 37, 48 or the AAL2 switching node 38. In the AAL2 switching node 38, each cell is once decomposed into CPS packets, and a cell is constituted by CPS packets having the same AAL2 system (AAL2 end system 35, 36, 37, 48 or AAL2 switching node 38) as an end point, and The cell flows over it. The VP handler 41 is an exchange that exchanges cells at the VP level, and the VC handlers 39, 40, and 47 are exchanges that exchange cells at the VC level. A VP connection is set between the AAL2 connection and the VC handlers 39, 40, and 47, and between the VC handlers 39, 40, and 47, and a VC connection passes inside. The VP connection is given a band in advance.
[0026]
Figure 7 AAL2 end systems 35 and VC handler 39, VC handler 39 and AAL2 switching node 38, AAL2 switching node 38 and the VC handler 40, 47, VC handler 47 and AAL2 end systems 48, VC handler 40 and AAL2 end systems 36 , 37, VP connections (hereinafter referred to as VP for simplicity) 42 to 46, 50, and 51 are provided, respectively.
[0027]
FIG. 1 shows the configuration of the AAL2 end system 35 (the same applies to other AAL2 end systems). The encoders 21 to 26 sample and encode audio information by a predetermined method. Alternatively, codes are exchanged. In addition, additional information such as an encoding method is added as necessary to create a variable-length information block called a CPS packet. When a certain amount of CPS packets are accumulated in the cellizers 27 and 28 or a timeout occurs, cells of a predetermined VC are generated. The cell is transmitted to the cell transmission waiting queue 29, and is transmitted according to the VP band of the VP.
[0028]
FIG. 2 is a configuration diagram of the AAL2 switching node 38. Cells arriving from the input link including the VP 43 are once decomposed into CPS packets by the decelerators 61 to 64. The CPS packet is exchanged by the CPS packet switch 65 according to the output destination and reaches the cell units 67 to 70.
[0029]
In the cellizers 67 to 70, cells are assembled again from the CPS packets. Since cellization is performed in units of VCs, there is basically a cellizer for each of VCs 67 to 70. The cells of the VC accommodated in the same VP are sent from the cellifiers 67 to 70 to transmission queues 71 and 72 corresponding to the VP. Cells are transmitted from the transmission waiting queues 71 and 72 according to the VP speed.
[0030]
The VP handler 41 and the VC handlers 39, 40 and 47 exchange cells in VP and VC units, respectively. This is the same as the prior art. However, the VC handlers 39, 40, and 47 require different features in the AAL2 connection setting phase from those according to the related art.
[0031]
FIG. 3 shows a configuration diagram of the VC handler 39. The VC handlers 40 and 47 have the same configuration. The output destination of the cell input from the input link including the VP 42 is specified by the routing tables 81 and 82, and the cell header is rewritten. Thereafter, the cells are exchanged for each output destination by the switch 83, and the cells are transmitted through the cell transmission wait queues 86 and 87 according to the cell transmission schedulers 88 and 89. In the present invention, the cell transmission schedulers 88 and 89 take out cells at a speed corresponding to the VP band of the output link. The transmission waiting queues 86 and 87 are configured in VP units. The reception determination of the ATM or AAL2 connection is performed by the reception determination devices 84 and 85.
[0032]
In the configuration diagram, the reception determination devices 84 and 85 are provided for each output (VP), but may be provided in one place in the VC handler 39 intensively. The processor 90 processes each signal (connection setting request, call, end-of-call, etc.), sets up an ATM connection, changes the routing table at the time of release, instructs the reception determination devices 84 and 85 to perform reception determination, and receives the determination result. Do.
[0033]
In addition, the reception determination devices 75 and 76 in the AAL2 switching node 38 and the processor 66 perform the same operation as the reception determination operation in the VC handler 39.
[0034]
Referring to FIG. 4, a case is considered where the voice sources 31 and 34 talk. FIG. 4 is a sequence diagram showing the operation of the embodiment of the present invention. For a call 500 from the voice source 31, the AAL2 end system 35 first has room to accept a new AAL2 connection from the AAL2 end system 35 to the VP 42 in the direction of the destination 34 (or 37). It is determined based on the bandwidth of this VP, the setting (ATM or) AAL2 connection, and the setting request AAL2 connection traffic characteristics (501). If the reception is determined to be accepted, a setting request 502 for setting an AAL2 connection is issued to a portion corresponding to the AAL2 portion between the audio sources 31 to 34 (between the AAL2 end systems 35 and 37). This is a preset having an originating endpoint in the AAL2 end system 35 and a destination endpoint in the VC handler 39 via the VP 42 (or, if necessary, set by an ATM signaling procedure). Performed by VC.
[0035]
Upon receiving the setting request, the VC handler 39 determines whether there is room in the internal processor for accepting a new AAL2 connection for the VP 43 in the direction of the destination 34 (or 37), Or) the AAL2 connection and the setting request are determined based on the traffic characteristics of the AAL2 connection (503). If it is determined that the VC handler 39 is accepted, the VC handler 39 has a calling end point, and has a destination end point in the AAL2 switching node 38 via the VP 43. An AAL2 connection setting request 504 is issued by the VC (which is set by an ATM signaling procedure in response). The AAL2 switching node 38 that has received the setting request makes an acceptance determination 505. Whether there is room to accept a new AAL2 connection from the AAL2 switching node 38 to the VP 44 in the direction of the destination voice source 34 (or 37), or the band of this VP and the setting (ATM or) AAL2 connection and setting request The determination is made based on the traffic characteristics of the AAL2 connection. If the AAL2 switching node 38 is determined to be accepted in the acceptance determination, the AAL2 switching node 38 has a calling end point in the AAL2 switching node 38 and a preset end point having an incoming end point in the VC handler 40 via the VP 44 (or AAL2 connection setting request 506 is issued by VC (set by an ATM signal procedure as needed). The VC handler 40 that has received the setting request makes an acceptance determination 507. Whether there is room to accept a new AAL2 connection from the VC handler to the VP 45 in the direction of the destination voice source 34 (or 37), or the band of this VP, the setting (ATM or) AAL2 connection, and the setting request AAL2 connection Is determined based on the traffic characteristics. If it is determined in the acceptance determination that the VC handler 40 is accepted, the VC handler 40 has a calling end point, and has a destination end point in the AAL2 end system 37 via the VP 45 (or a preset (or otherwise)). AAL2 connection setting request 508 is issued by the VC (which is set by an ATM signal procedure as needed). When it is determined that the reception is not possible in each of the reception determinations, a call loss or a detour to another route is performed. When another route is detoured, the same procedure as above is performed again.
[0036]
The AAL2 end system 37 that has received the setting request calls the audio source 34 (509). In addition, the VC handler 40 is notified of the call in progress using the VC in the opposite direction to the VC for which the setting request was made (510). The VC handler 40 notifies the AAL2 switching node 38 that the call is being made, using a pair of VCs in the opposite direction to the VC for which the setting request was made (511). The AAL2 switching node 38 notifies the VC handler 39 that the call is being made, using a pair of VCs in the opposite direction to the VC for which the setting request was made (512). The VC handler 39 notifies the AAL2 end system 35 that the call is being made, using a pair of VCs in the opposite direction to the VC for which the setting request was made (513). The AAL2 end system 35 notifies the voice source 31 that the call is being made by using a pair of VCs in the opposite direction to the VC for which the setting request was made (514). When the voice source 34 goes off-hook (515), response signals 516 to 521 are issued as in the case of the notification during calling, and the telephone enters a call state.
[0037]
When the call ends, the audio source 31 notifies the AAL2 end system 35 of the end of the call by on-hook or the like (522). The AAL2 end system 35 releases the band on the VP 42 for the AAL2 connection to end the call (523). Further, an AAL2 connection between the AAL2 end systems 35 and 37 is released, and an end signal 522 is transmitted on the same route as the AAL2 connection setting request to notify the audio source 34 of the end of the AAL2 connection. The VC handler 39 receiving the signal releases the band for the AAL2 connection on the VP 43 (525). Next, the end signal 526 is transmitted on the same route as the AAL2 setting request. Similarly, the AAL2 switching node 38 and the VC handler 40 also release the bandwidths 527 and 529, and transmit the end signals 528 and 530 on the same route as the AAL2 setting request. The AAL2 end system 37 that has received the end signal 530 notifies the audio source 34 of the end signal 531.
[0038]
The following judgment method is used.
[0039]
(1) When the traffic characteristics of AAL2 are expressed by the same traffic descriptor as ATM, AAL2 traffic is regarded as ATM traffic, and ATM traffic is regarded as ATM traffic within the VP band using the conventional ATM reception determination method. It is determined whether AAL2 traffic can be accepted.
[0040]
(2) When only AAL2 traffic of the same bit rate is multiplexed in a VP, how many AAL2 traffics can be multiplexed for each VP band is evaluated in advance by computer simulation or a mathematical expression, and each reception judgment is made. In this case, if the number of connected AAL2 connections in each VP is less than the evaluation value, it is accepted, otherwise, it is not accepted.
[0041]
The embodiment of the present invention has been described on the assumption that the upper level is AAL2. However, the present invention can be applied to a case where a single VC is shared by a plurality of upper level connections.
[0042]
(Example summary)
The same traffic is used between the method using VC (Constant Bit Rate VC) in which a fixed band is provided in a VP and the method using VC (Unspecified Bit Rate VC) in which a band is not provided according to the present invention (UBR: Unspecified Bit Rate VC). FIG. 5 shows how much the VP band to carry. FIG. 5 is a diagram showing the relationship between the number of VCs and the VP band, with the horizontal axis representing the VC number and the vertical axis representing the VP band. The celling timeout is 4 ms, the cell loss rate specified value is 10 ⁻⁴ , and the buffer is the result when the staying time of the cell is 5 ms at the maximum. When the number of VCs in the VP is "1", the amount of traffic that can be carried at 768 kbps or 1.5 Mbps is added to the traffic. As can be seen in FIG. 5, the required bandwidth is significantly reduced by the present invention.
[0043]
【The invention's effect】
As described above, according to the present invention, the number of cells that can be transferred per predetermined VP band can be increased. Further, the number of cells that can be transferred per predetermined transmission path band can be increased.
[Brief description of the drawings]
FIG. 1 is a block diagram of a main part of an AAL2 end system according to an embodiment of the present invention.
FIG. 2 is a block diagram of a main part of an AAL2 switching node according to an embodiment of the present invention.
FIG. 3 is a block diagram of a main part of the VC handler according to the embodiment of the present invention.
FIG. 4 is a sequence diagram showing the operation of the embodiment of the present invention.
FIG. 5 is a diagram showing a relationship between the number of VCs and a VP band.
FIG. 6 is a block diagram of a main part of a conventional AAL2 end system.
FIG. 7 is a diagram showing an example of a network configuration.
[Explanation of symbols]
21-26 Encoders 27, 28, 67-70 Cellizers 29, 98, 71, 72, 86, 87 Transmission queue 30, 73, 74, 88, 89, 99 Cell transmission schedulers 31, 32, 33, 34, 49 Audio source 35, 36, 37, 48 AAL2 end system 38 AAL2 switching node 39, 40, 44, 47 VC handler 41 VP handler 61-64 Decellularizer 65 CPS packet switch 66, 90 Processor 81, 82 Routing table 83 Switch 75, 76, 84, 85 Reception determination device 501, 503, 505, 507 Reception determination 502, 504, 506 AAL2 connection setting request 508 AAL2 connection reception request 509 Calling 510-513 Calling 514 Calling notification 515 Off-hook 516- 521 response 22,524,526,528,530,531 final story 523,525,527,529 band released

Claims (10)

Including a virtual path between the transmitting end and the receiving end of the cell, comprising means for performing cell transfer between the transmitting end and the receiving end via a virtual channel set on the virtual path, In an ATM communication network in which a virtual channel is set to be shared by a plurality of higher-level connections,
The means for performing the transfer determines whether or not the virtual path can accommodate a higher-level connection, and if the virtual path can accommodate the higher-level connection, is given to the virtual path according to the number of higher-level connections set in the virtual path . An ATM communication network including means for variably allocating a part of a band to the upper connection. 2. The system according to claim 1, further comprising: means for estimating a bandwidth allocated by said allocating means in accordance with the number of higher-level connections set in said virtual path; ATM communication network. 2. The ATM communication network according to claim 1, further comprising means for preliminarily holding an upper limit value of the number of higher-level connections set in the virtual path and determining whether or not to accept cell transfer in accordance with the upper limit value. 4. The ATM communication network according to claim 1 , further comprising a transmission queue corresponding to the virtual path . 4. The ATM communication network according to claim 1 , wherein said upper connection is an AAL2 connection . The virtual path in the zone of the scan, ATM network according any one of the upper limit value claims 1 set 3. 4. The ATM communication network according to claim 1, wherein an upper limit is set for a band of the transmission path including the virtual path. The ATM communication network according to any one of claims 1 to 3, wherein the virtual channel is a UBR virtual channel. 4. The ATM communication network according to claim 2, wherein the acceptability determination unit performs the acceptability determination for each virtual path in which the higher-order connection request is accommodated. 5. The acceptability determination means is a virtual channel handler 4. The ATM communication network according to claim 2, wherein the ATM communication network is provided in a switching node of an upper connection.

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