JPH05130126A - Atm exchange network - Google Patents

Abstract

PURPOSE:To obtain the ATM exchange network in which communication quality on request is surely warranted without call processing through the use of a virtual path in a virtual path exchange node. CONSTITUTION:The ATM exchange network is provided with a virtual path setting section 4 deciding 1st and 2nd traffic descriptors representing a characteristic of a virtual path to virtual paths 5a-5c and using the 1st traffic descriptor so as to set a virtual path, virtual channel setting sections 6a-6c using the 2nd traffic descriptor so as to set a virtual path.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ATM switching network.

[0002]

2. Description of the Related Art In recent years, research and development of a B-ISDN (Integrated Broadband Service Integrated Digital Network) capable of unifying and handling various kinds of information such as voice, images and data have been advanced. In B-ISDN, ATM (Asynchronous T
ransfer Mode: Asynchronous transfer mode) is used. ATM is a system in which all information is put in a fixed-length packet called a cell and packet transmission is performed by hardware switching, and a switching network using this system is called an ATM switching network.

When communication is performed using such an ATM switching network, generally, a call request is made prior to the communication, a connection called a virtual channel (VC) is set, and user information is sent in the form of cells. And transfer along the VC. In the ATM switching network, a virtual path (V
A connection called P) is also set up. VP is VC
And a VC is set between terminals via one or a plurality of VPs terminated at a VC switching node that performs VC switching. In the VP switching node that relays VPs, cells are switched without being aware of the individual VCs multiplexed in one VP, so call processing at the time of VC setting is unnecessary. This reduces the call processing load of the entire switching network.

At the time of setting the VC, call setting control is performed in order to ensure that the required communication quality is provided. In this call setting control, it is possible to estimate the communication quality when the VC requested to be set is set from the traffic descriptor indicating the traffic characteristics of the VC and the usage status of the communication resources of the switching network, and set this VC. Determine if it is possible.

On the other hand, in the VP exchange node, it is desired not to estimate the communication quality as described above every time the VC is set. For this reason, a traffic descriptor representing the traffic characteristics of the VP is defined, the communication quality such as the cell loss rate in the VP switching node defined using this traffic descriptor, and the V in the VC switching node.
A method of obtaining the communication quality when the VC is set from the communication quality when the C is multiplexed to the VP is used. Note that VC is V
The communication quality when multiplexing to P is obtained from the traffic descriptor used when obtaining the communication quality at the VP switching node and the traffic descriptor defined in the VC that is multiplexed into that VP. The assigned value is used.

This method cannot reliably guarantee the communication quality required of the VC for the following reason. Since the arrival of cells on the VCs multiplexed in one VP is asynchronous, the traffic characteristics of the VP on the actual transmission path are different from the traffic characteristics specified by the traffic descriptor specified for that VP. Not necessarily the same. For this reason,
The actual communication quality at the VP switching node may not satisfy the communication quality obtained by using the traffic descriptor defined in the VP. In this way, when the actual communication quality at the VP switching node does not satisfy the communication quality obtained by using the traffic descriptor defined in the VP, the VC
It may not be possible to provide the communication quality required by the.

This problem can be avoided in the VP switching node by estimating the communication quality at the VC setting from the traffic descriptor of the VC and the usage status of the communication resources, similarly to the call setting control at the VC setting in the VC switching node. However, the call processing load increases because the VP switching node requires call processing for communication quality estimation for each VC setting.

[0008]

SUMMARY OF THE INVENTION As described above, the VP
In the conventional ATM switching network in which a traffic descriptor is defined for the VP, the VP is set using this traffic descriptor, and the VC setting control for the VP is performed, the communication quality at the VP switching node cannot be reliably guaranteed. Therefore, there is a problem that the communication quality required for the VC may not be provided, and a method of estimating the communication quality at the time of setting the VC is adopted from the traffic descriptor of the VC and the usage status of the communication resources in the VP switching node. There is a problem that the call processing load increases because the VP switching node needs call processing for communication quality estimation for each VC setting.

The present invention has been made to solve such a problem, and it is possible to reliably guarantee the required communication quality without performing call processing using a VP in a VP exchange node. The purpose of the present invention is to provide a secure ATM switching network.

[0010]

In order to solve the above-mentioned problems, the ATM switching network of the present invention defines different first and second traffic descriptors representing the traffic characteristics of the virtual path in the virtual path, and It is characterized in that it has a virtual path setting means for setting a virtual path using the first traffic descriptor and a virtual channel setting means for setting a virtual channel using the second traffic descriptor.

Further, according to the present invention, the communication quality realized by the virtual channel set by the virtual channel setting means by using the second traffic descriptor is the virtual quality by the virtual path setting means by using the first traffic descriptor. It is characterized in that the first and second traffic descriptors are set so as to be higher than the communication quality estimated when the path is set.

[0012]

As described above, in the present invention, the first and the first different paths are set when the virtual path is set and when the virtual channel is set (that is, when it is determined whether or not the virtual channel is multiplexed into the virtual path). Two traffic descriptors are used respectively.

Therefore, when the virtual channel setting means sets the virtual path using the first traffic descriptor, the communication quality of the virtual channel set by the second traffic descriptor is set by the virtual path setting means. The first traffic descriptor is higher than the estimated communication quality, that is, the traffic characteristic of the actual virtual path caused by the virtual channel set up using the second traffic descriptor satisfies the first traffic descriptor. When the first and second traffic descriptors are defined, the VC is set so that the communication quality actually obtained at the VP switching node and the communication quality of the VC are guaranteed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration of an ATM switching network according to an embodiment of the present invention. As shown in the figure, VC (virtual channel) switching nodes 1a to 1c are connected to transmission lines 2a to 1c.
It is connected to the VP (virtual path) switching node 3 by 2c. Further, VP5a is located between the VC switching nodes 1a and 1c, and VP5b is located between the VC switching nodes 1a and 1b.
However, the VP 5c is set between the VC exchange nodes 1b and 1c, respectively.

The VPs 5a to 5c include the VPs 5a to 5c.
First and second different traffic descriptors are defined as the traffic descriptors for expressing the traffic characteristics of c.

The VP setting unit 4 sets a VP between the VC exchange nodes 1a to 1c via the VP exchange node 3.
The VP setting unit 4 determines the first VP set in each of the transmission lines 2a to 2c when a new VP needs to be set or when the band of the VP needs to be changed. Using the traffic descriptor, each of the transmission lines 2a-2
c communication quality, for example, VP5a-5c transmission line 2
Estimate the communication quality when multiplexed in a. VP5a
5c defines the communication quality that must be satisfied when multiplexing on the transmission path, and the communication quality obtained using the first traffic descriptor satisfies this defined communication quality. Set VP only for

Further, the VP setting unit 4 has a function of converting the first and second traffic descriptors defined in the VP in addition to the above-mentioned functions, and the first traffic description used when setting the VPs 5a to 5c. The child and the second traffic descriptor used when obtaining the communication quality when the VPs 5a to 5c are multiplexed on the transmission path are converted. The conversion of the traffic descriptor will be described later.

The VC switching nodes 1a to 1c are provided with VC setting units 6a to 6c, respectively. These VCs
The setting units 6a to 6c set the VC for the communication request. When setting a VC, first, the VC switching node accommodating the partner terminal is obtained from the destination address, and the VP set between the VC switching node and that VC switching node is selected.
When the VC requested by P is set, it is determined whether the requested communication quality can be provided, and if it can be provided, the VC is set.

In this case, the VC setting units 6a to 6c need to estimate the communication quality when the VC for which communication is requested is set to the selected VP. This communication quality is
This is a value when the cell is output when the second traffic descriptor defined in the VP is satisfied, and is converted from the first traffic descriptor used when the VP is set by the VP setting unit 4. The second traffic descriptor and the traffic descriptor (third traffic descriptor) representing the traffic characteristics of the VC defined in the VC are obtained.

The communication quality provided to the VC is the same as the VC to the VC.
Can be obtained from the communication quality when multiplexing the VP and the communication quality when multiplexing the VP on the transmission path. The latter VP
The upper limit of the communication quality when multiplexing is performed on the transmission path is guaranteed in advance by the VP setting unit 4. Therefore, when the first and second traffic descriptors are converted in the VP setting unit 4, by satisfying the characteristics of the actual cell flow, the communication quality is surely guaranteed even when there is a VP. The VC can be set. Next, the above-mentioned VP and VC setting procedure will be described in more detail with reference to the flowchart shown in FIG.

When a new VP setting request is made in step S1, the VP setting section 4 first uses the transmission line capacity and the first traffic descriptor defined in the VP to set the VP.
The communication quality at the time of being multiplexed on the transmission path is estimated (step S2), and this is compared with the required communication quality (step S3). Here, when the communication quality estimated in step S2 satisfies the required quality, the VP setting unit 4 sets the VP capacity (step S4).

When the VP setting unit 4 sets the VP in this way, at the same time, the VP setting unit 4 notifies the VC setting unit 6 of the second traffic descriptor defined in the set VP. The VC setting unit 6 sets the VC using the notified second traffic descriptor. That is, when the VC setting request is made in step S5, the VC setting unit 6 outputs V
The communication quality of the VC is estimated by using the second traffic descriptor defined in P and the third traffic descriptor defined in the VC requiring the setting (step S
6). Next, the estimated communication quality is compared with the required communication quality (step S7). Here, when the estimated communication quality satisfies the required quality, the VC is set (step S8).

Next, the probability that the required VC cannot be set (blocking rate) is calculated (step S
9) Then, it is judged whether or not the VP capacity needs to be changed (step 10). If it is determined that the VP capacity needs to be changed, the step S is performed again.
Return to 2 and change the VP setting. On the other hand, when it is determined that it is not necessary to change the VP capacity, step S5
Return to and set the VC.

The determination of the VP capacity change in step S10 is made by, for example, increasing the VP capacity when the blocking rate exceeds a certain fixed value, and conversely, when the blocking rate is smaller than another fixed value, as compared with the communication request. Since the VP capacity is excessive, the VP capacity is reduced.

In FIG. 2, the blocking rate is always obtained so that the VP capacity can be changed. However, it is naturally possible to change the VP capacity normally or to change the VP capacity only at a predetermined time. Is.

Next, conversion of the first and second traffic descriptors will be described with reference to FIG. For simplicity, consider a case where only the peak rate is defined as the third traffic descriptor in the VC. The peak rate is the reciprocal of the minimum interval between cells in the cell flow shown in FIG. Further, it is assumed that the peak rates of all VCs are equal, and this is _VVC . It is assumed that the traffic descriptor (second traffic descriptor) of the VP used in the VC setting units 6a to 6c is also defined only for the peak rate, and this is referred to as V _VP (VC). VC setting units 6a to 6
In c, when setting VC to VP, if the number of VC set to the VP is n = V _VP (VC) / V _VC or less, V
It is determined that C can be set.

On the other hand, the characteristics of the cell flow of the VP on the actual transmission line are as shown in FIG. 3 (b) when cells from each VC are simultaneously input as shown in FIG. 3 (a). Becomes
Most bursty. First in the VP setting section 4
When setting a VP using the traffic descriptor of the above, it is necessary to guarantee the communication quality even in such a case. Therefore, the traffic descriptor (first traffic descriptor) of the VP used in the VP setting unit 4 is, for example, the peak rate V _VP (VP) = 1 and the maximum burst length N = n. By doing this, the actual traffic is always V _VP (V
Since P) and N are satisfied, the communication quality estimated by the VP setting unit 4 using the first traffic descriptor is guaranteed. As a traffic descriptor of VP,
Besides this, it is also possible to use an average rate, an average burst length, or the like.

As another example of conversion of the first and second traffic descriptors, a certain constant α less than 1 is defined,
The α times the first traffic descriptor used in the VP setting unit 4 may be used as the second traffic descriptor used in the VC setting units 6a to 6c. Also in this case, the actual VP may be more bursty, but the load factor becomes smaller by making α smaller by that amount, so that the communication quality can be guaranteed.

Further, since the use efficiency of the switching network is reduced when α is reduced, the value of α is set to 1 in order to improve the use efficiency.
The communication quality can be assured by adding a regulating device for regulating the cell output to the VC switching node only when the actual cell flow cannot satisfy the communication quality as a result. ..

[0030]

As described above, according to the present invention, the first and second traffic descriptors are set in the virtual path, and the virtual path is set by using the first traffic descriptor. By configuring the virtual channel using the traffic descriptor, the VC
It is possible to guarantee the defined communication quality without requiring call processing in the VP switching node when setting is performed.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an ATM switching network according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining a processing procedure of the embodiment.

FIG. 3 is a diagram for explaining a traffic descriptor conversion example in the embodiment.

[Explanation of symbols]

 1a to 1c ... Virtual channel switching nodes 2a to 2c ... Transmission path 3 ... Virtual path switching node 4 ... Virtual path setting unit 5a-5c ... Virtual path 6a-6c ... Virtual channel setting unit

Claims (2)

[Claims] 1. An ATM switching network in which a virtual channel and a virtual path accommodating a plurality of virtual channels are set in each cell transmitted on a transmission path, wherein different first and A virtual path setting unit that sets a second traffic descriptor and sets a virtual path using the first traffic descriptor, and a virtual channel setting unit that sets a virtual channel using the second traffic descriptor An ATM switching network characterized by having: 2. The first and second traffic descriptors are such that the communication quality realized in the virtual channel set by the virtual channel setting means using the second traffic descriptor is the virtual path setting means. 2. The A according to claim 1, wherein the communication quality is set to be higher than the communication quality estimated when the virtual path is set by using the first traffic descriptor.
TM switching network.