JP3253375B2 - Packet switching equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet switching apparatus, and more particularly, to selecting a data link to be used.

[0002]

2. Description of the Related Art In a conventional packet switching apparatus, a plurality of data links (logical lines set in physical lines) are generally available.
For this reason, the packet switching device must select which of the plurality of data links to use for packet communication. As a method of selecting the data link, a method of selecting a packet having a small number of packets multiplexed in the data link or a method of cyclically selecting the data link has been conventionally used. In packet switching, when a switching device uses a plurality of data links, the service quality of packet communication is affected by the sum of the traffic of packets multiplexed for each data link (the service quality deteriorates as the traffic increases). . However, the service quality described here is a delay time until a packet is transferred.

[0003] Therefore, when the packet switching apparatus performs the data link capture in the same manner as the circuit-switched trunk capture (trapping of the line interface), the number of calls in the data link and the number of cyclic calls are made. Is not uniform, and a certain data link is in a state where packets to be transmitted are crowded.
There is a disadvantage that the data link cannot be operated efficiently. This is because the packet call has the following properties. That is, since the upper limit (such as the X.25 throughput class) of the transmission speed (the number of packet calls issued per unit time) of the packet call is simply determined in advance, the actual traffic (the packet Is changed with time. Also, in packet switching using packet multiplexing, since there are a plurality of upper limit values of transmission speed, it is difficult to determine the communication capacity based on the number of calls, unlike circuit-switched calls.

[0004]

As described above, when a data link for transmitting a packet call is selected by the conventional packet switching device, the data link is selected based on the number of transmission packets in the data link. Alternatively, if a method of cyclically selecting a data link is adopted, the traffic of the data link changes with time, or it is essentially difficult to determine the communication capacity of the data link. There are disadvantages that the quality varies and the data link cannot be operated efficiently.

Accordingly, an object of the present invention is to provide a packet switching apparatus which eliminates the above-mentioned drawbacks and makes it possible to use the data links evenly and to make the service quality uniform for each data link.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a packet switching apparatus which is capable of selecting any one of a plurality of data links for packet communication and transmitting or receiving the data using each data link. Monitoring means for monitoring the usage rate of a buffer in which packets are temporarily stored , and using a buffer corresponding to each data link based on the monitoring result of the monitoring means
Volume and calculate the average
The corresponding load, buffer usage and communication at a given time
Calculating means for calculating an overload corresponding to a difference between the road capacity and a selecting means for selecting a data link having a small load and overload based on the load and the overload calculated by the calculating means; When a received packet call is generated, a packet switching unit for communicating the packet call using the data link selected by the selecting unit is provided.

[0007]

In the packet switching apparatus according to the present invention, the monitoring means monitors the usage rate of the buffer in which the packet transmitted or received using each data link is temporarily stored. The calculating means calculates each data link based on the monitoring result of the monitoring means.
The buffer usage corresponding to the
And the load corresponding to the average
Overload corresponding to the difference between buffer usage and channel capacity
To calculate the door. The selection means selects a data link having a small load and an overload based on the load and the overload calculated by the calculation means. The packet switching means communicates the packet call using the data link selected by the selection means when a transmission or reception packet call occurs. As a result, the data links with smaller loads and overloads are sequentially selected, so that the loads on the respective data links are equalized and the service quality is also equalized.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the packet switching device of the present invention. Reference numeral 1 denotes a packet switching device having a network terminating device 11, a switching unit 12 for exchanging packets, a terminal accommodating device 13, and a central control unit 14. In the central control unit 14, a quality evaluation unit 141 for selecting a data link to be used from the load state of each data link and a call processing unit 142 for controlling the switching unit 12 are constructed by software or the like. The network-side trunk 2 is connected to the network terminating device 11, and the packet terminal 3 is connected to the terminal accommodating device 13.

FIG. 2 is a block diagram showing a detailed example of the network termination device 11 shown in FIG. The network terminating device 11 includes a transmitting device 111 for transmitting a packet call to the network, and a transmission buffer 11 for temporarily storing the packet call transmitted from the transmitting device 111.
2, a receiving device 113 for receiving a packet call on the network, a receiving buffer 114 for temporarily storing the packet call received by the receiving device 113, and a network termination device control unit 115 for controlling the operation in the network termination device 11. . Further, the network termination device control unit 115 is provided with a monitoring unit 1151 for monitoring the usage rate of the transmission and reception buffers 112 and 114 (the amount of data accessing the buffers).

Next, the operation of this embodiment will be described. The transmission buffer 112 and the reception buffer 114 in the network termination device 11 for each data link shown in FIGS.
Since a packet is stored for each reception, the present embodiment focuses on the amount of the packet (corresponding to the usage rate of the buffer) to select a data link. Here, in the case of performing packet multiplexing, it is possible that the traffic multiplexing the call exceeds the communication capacity of one data link. This is because the traffic of a packet call differs from the traffic of a circuit-switched call and varies with time. A buffer is used for multiplexing packets, but the packets stored in the buffer 112 are not deleted until it is confirmed that the packets have been transmitted correctly. Therefore, a packet that has not been transmitted remains in the buffer 112. Similarly, a similar problem may occur when arriving packets are demultiplexed. Therefore, packets stored in the buffer 114 are newly generated or arrived from the network and packets remaining in the buffer. The traffic can be defined by the number of packets passing through the data link, but is actually stored in the transmission and reception buffers 112 and 114 at the multiplexing or demultiplexing stage. Can not be evaluated. Therefore, as described above, attention is paid to the amount of packets stored in the buffers 112 and 114.

The network termination unit control unit 115 of the network termination unit 11
The data link monitoring unit 1151 monitors the number of packets (buffer usage rate) stored in the transmission and reception buffers 112 and 114, and compares the monitoring result with the central control unit 14.
To the data link quality evaluation unit 141. The quality evaluation unit 141 calculates the average usage of each buffer based on the usage rate of each buffer sent from the monitoring unit 1151, and sends the calculation result to the call processing control unit 142. The call processing control unit 142 estimates a delay time until a packet transmitted on each data link is transferred from the average buffer usage calculated by the quality evaluation unit 141, and selects a data link with good service quality. In the following, the constant period T
The ratio between the average buffer usage and the communication path capacity for each is referred to as a load, and is used for evaluation by the quality evaluation unit 141. The packet switching device 1 multiplexes the packets received from the packet terminal 3 accommodated via the terminal accommodating device 13 and sends out the multiplexed packets to the data link of the central office interface, or sends the multiplexed packet to the network termination device 11 from the central office interface. Demultiplexing the received packet and transmitting it from the terminal accommodating device 13 to the packet terminal, demultiplexing / multiplexing the packet received from the connected central office interface, and transmitting the packet again to the central office interface. Perform packet switching operation.

As described above, the data link monitoring is performed by the monitoring unit 1151 of the network termination unit 11 checking the transmission buffer 112 and the reception buffer 114 as follows. That is, the monitoring unit 1151 records the accessed buffer size every time the packet data is written to or read from the transmission buffer 112 and the reception buffer 114 for each data link. The accessed buffer size is X. A packet having a packet length in the data, such as 25 packets, may be used, or a header including data such as the packet length may be added to the packet data in advance and used. Further, the monitoring unit 1151 totalizes the buffer sizes accessed within a unit time for each data link, and sends the totaled buffer sizes to the quality evaluation unit 141 of the central control unit 14. These processes are realized as a part of software of the network termination unit control unit 115.

Next, a description will be given of a method in which the above-mentioned quality evaluation section 141 calculates the load of the data link. The total buffer usage Lsi (t) in the unit time on the sending side of the data link i at the time t is represented by the following equation. Here, i is a subscript for the data link. Lsi (t) = {time (t−
The amount of packets remaining in 1) {+ the amount of packets newly generated from time (t-1) to time t} The reception buffer usage Lri (t) at time t on the receiving side is similarly calculated by the following equation. Indicated by Lri (t) = {the amount of packets remaining at time (t-1)} + {the amount of packets newly arriving from time (t-1) to time t} where the load Ai of the data link i is Is defined as Ai = max ｛Σ
Lxi (t)｝ / (n × Ci × T) Ai where x = s, r
Is the condition 1. However, the condition 1 is that a fixed time T = n × (unit time) in one data link.

Further, Ci is the communication channel capacity of the data link i per unit time, and Δf (x) Condition C means the sum of f (x) satisfying Condition C. Also, max
g (z) z = a, b is the equation g (x), z = a,
It means the maximum value of g (a) and g (b) when z = b.
The overload Bi of the data link i is defined as follows. Bi = max {F (Lxi (t) -Ci)}
/ (N * Ci * T) x = s, r is the condition 2. However,
F (x) is a function satisfying the following equation. F (x) = x (x
> 0) F (x) = 0 (x ≦ 0) These statistical processes are performed by software executed by the processor of the central control unit 14.

The selection of a data link is performed for all the data links i using the load Ai and the overload Bi as follows (1) to (3). (1) The data link quality evaluation unit 141 creates a group of data links having a small load Ai among all the data links, and sets this group as a selection candidate 1. (2) If there are a large number of selection candidates 1 obtained in (1), the data link quality evaluation unit 141 creates a group of data links having a small overload Bi from the selection candidates 1 and selects this group as a selection candidate 2 And The quality evaluation unit 141 sends the selection candidates 1 and 2 to the call processing control unit 142. (3), call processing control unit 14
2 cyclically selects data links one by one from the selection candidates 2. However, when another selection condition exists, a data link satisfying the condition is cyclically selected from the selection candidates 2. Here, when there is no data link that satisfies the condition, candidates 1 and 2 are repeatedly obtained from data links other than the data link that does not satisfy the condition. If there is no data link satisfying the condition, the call processing control unit 1
Reference numeral 42 indicates that the selection has failed, and performs disconnection processing of the packet call. The call processing control unit 142 uses the well-known switching system call processing method when not performing the above-described dynamic data link capture, and switches the switch or the like when performing the dynamic data link capture to perform the well-known switch processing. The data link capturing function of the control unit is changed to the method adopted in this embodiment.

According to the present embodiment, the monitoring unit 1151 of the network terminating device 11 for each data link
2 and 114, the quality evaluation unit 141 calculates the average buffer usage based on the monitoring result, and further calculates the load Ai of each data link from the average buffer usage.
And overload Bi, and a data link selection method is determined from these loads Ai and overload Bi.
The call processing control unit 142 selects the data link that has a small number of packets and is not temporarily overloaded Bi as the data link to be used, and selects the data link selected in this manner. , It is possible to select a data link with a small substantial traffic at any time. Therefore, the traffic of packets transmitted through each data link is equalized, so that the service quality of each data link can be equalized and each data link can be operated efficiently. Also, equalization of service quality for each data link means that
Since there are many cases where there is no extremely crowded data link, a communication path with good service quality is secured as a whole.

[0017]

As described above, according to the packet switching apparatus of the present invention, the service quality of each data link can be made uniform by using the data links evenly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a packet switching device of the present invention.

FIG. 2 is a block diagram showing a detailed example of the network termination device shown in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Packet switching device 2 ... Network side trunk 3 ... Packet terminal 11 ... Network terminating device 12 ... Switching unit 13 ... Terminal accommodating device 14 ... Central control unit 111 ... Transmitting device 112 ... Transmission buffer 113 ... Receiving device 114 ... Receiving buffer 115 ··· Network termination device control unit 141 ··· Quality evaluation unit 142 ··· Call processing control unit 1151 ··· Monitoring unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/56

Claims (1)

(57) [Claims] 1. A packet switching device which can select an arbitrary one of a plurality of data links and use it for packet communication. A buffer in which a packet transmitted or received using each data link is temporarily stored. Monitoring means for monitoring the usage rate of each data link and corresponding to each data link based on the monitoring result
Buffer usage at a given time
The load corresponding to the average usage and the
Calculating means for calculating an overload corresponding to a difference between the usage amount of the network and the communication path capacity; and selecting a data link having a small load and an overload based on the load and the overload calculated by the calculating means. And a packet switching unit for communicating the packet call using the data link selected by the selection unit when a transmission or reception packet call occurs.