JPH03280644A - Dynamic slot assignment multiplex system - Google Patents

Abstract

PURPOSE:To realize a cross connector with less buffer quantity by providing a variable delay means which calculates a required delay time according to the statistical distribution while availing the arrival of a detected packet itself of an opportunity and produces the calculated delay time to the system. CONSTITUTION:In the case of multiplexing a packet 400 sent from plural user equipments, the position to be multiplexed is allocated to each packet dynamically, that is, at a random delay according to a statistic rule. In order to provide a dynamic delay to the multiplexer, the system is provided with a selector 401 of, e.g. 1:N, a delay circuit 402 for one packet and a control section 403 allocating a slot dynamically to the input packet 400. Moreover, the control section 403 generates a control data as to how much delay is to be provided according to the statistic distribution to each input packet based on a slot allocated to a just preceding packet. Thus, the periodicity in terms of the packet multiplex level is relieved and the cross connector is realized with less buffer quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field to which the invention pertains The present invention relates to broadband ISDN (Integrated
Asynchronous transfer mode (hereinafter referred to as ATM) in
The present invention relates to a multiplexing method using chronous transfers (transfer made), and particularly relates to a multiplexing method at the output section of a cross-connect switch.

(2) Conventional technology Currently, AT is the multiplexing method used in broadband 15DN.
The M method is attracting attention. The ATM system is fundamentally different from the conventional packet system in that the format of information is in a packet format or in the multiplexing method. That is, in the ATM system, the capacity is specified for each line, and it is possible to provide high throughput and transparent characteristics similar to line multiplexing.

(Reference 1; Fukinuki, Itamoto, Komiya, Inoue (Digital line configuration using burst multiplexing technology J IEICE Technical Report C379-83
, PP55-60.1979) (Reference 2: Sahara.

Sahara, [Cell transmission monitoring and regulation method in high-speed burst multiplex transmission system] 1898 Autumn National Conference of the Institute of IEICE,
N (LB -262) As described above, since the capacity is specified for each line, the transfer process within the network can be simplified compared to the conventional packet method.

For example, consider the multiplex transmission system shown in FIG.

In FIG. 1, 100 is a packet signal, 101 is a line capacity monitoring circuit, 102 is a multiplexer, 103 is a multiplex transmission line, 104 is a cross-connect device, 105 is a demultiplexer, 106 is 1.2.3.4. 5.6 User equipment (transmission side), 107 are a, b, c, d,
The user equipment (receiving side) is indicated by e and f.

In the multiplexing device 102, the line capacity monitoring circuit 101 determines that the flow is less than the specified capacity. Packets output from the line capacity monitoring circuit 101 are multiplexed by the multiplexing device 102 on a first-come, first-served basis. Cross-connect device 104 is multiplex transmission line 1
The packet is routed between 03 and 03 according to its destination.

That is, it is distributed to the output multiplex transmission path. For example, a packet going from transmitting device 1 to receiving device a takes route 108 within cross-connect device 104. Similarly, a packet going from transmitting device 1 to receiving device d takes route 109. The cross-connect device 104 checks the destination information included in the header of the input packet and performs the above-mentioned routing. Each line (between 106 and 101) routed by the cross-connect device 104 has a predetermined capacity, and is designed to accommodate so as not to exceed the capacity of the multiplex transmission line 103. Even if it is simply routed according to its destination, the multiplex transmission path 103
No overflow will occur regarding the transmission line capacity.

However, the method shown in FIG. 1 described above has the problem that the packet transmission mode of the transmitting user equipment 106 affects the number of lines that can be accommodated in the cross-connect device 104, complicating the line accommodation design. For example, consider the line accommodation situation of the loss connect device 203 as shown in FIG. Here, 200 is the input side multiplex transmission path, 201 is the packet, and 202 is the cycle (multiplicity) of the multiplexed packet.
, 203 is a cross-connect device, 204 is a buffer (F
IFO), 205 is an output multiplex transmission line. The cross-connect device 203 in FIG. 2 corresponds to 104 in FIG.

In FIG. 2, hatched packets of the same type have different input multiplex transmission paths 200, but the same output multiplex transmission path 205.
Indicates that the route will be routed to In FIG. 2, the capacity of one multiplex transmission path is V, and N lines with a capacity of V/H are multiplexed, and the cross-connect device 203 has a Buffer of finite size y204 (FIFO, First In First
0ut). Assuming the line capacity situation as shown in FIG. 2, if all packets arriving at a certain time are output to the same multiplex transmission path, that is, in FIG.
When the data is output to 1, the output buffer capacity is required for a maximum of N packets, and with a high-speed transmission line where the number of N packets is several hundred to several thousand, the required buffer size increases and the equipment cost increases. .

A conventional solution to this problem is to set the buffer amount to a value smaller than N, add a circuit that constantly monitors the usage status of the output buffer 204 in FIG. proposed a method in which a restriction signal is sent back to the transmitting side for all lines accommodated in the relevant multiplex transmission path.

(Reference 3; J, D.

Atkins, “Path Control;
Transport Network of SNA”,
IEEE Trans, C0M-28,4, April
il 1980) If this conventional method is applied, the transmitting end is notified of the circuit capacity limit due to the reduction in buffer capacity, which has the advantage that regulation by distributed control can be easily realized. However, in this conventional system, monitoring was the main focus, and there was no improvement in accommodation efficiency.

To summarize the above problems, if all packets arriving at a certain time are output to the same multiplex transmission path, the output buffer capacity becomes large, which increases costs.

(3) Purpose of the Invention The purpose of the present invention is to provide dynamic slot allocation multiplexing which solves the problem that the number of lines accommodated in an ATM network is affected by the number of packets input from each side being multiplexed. The goal is to provide a method.

(4) Structure of the invention (4-1) Features of the invention and differences from the conventional technology When the present invention multiplexes packets sent from a plurality of user devices, the multiplexing position is dynamically set for each packet. That is, the most important feature is that the delay amount is allocated randomly according to a certain statistical law.

Conventionally, packet multiplexing in an ATM network has been performed regularly on a first-come, first-served basis, and the arrangement of packets after multiplexing is completely different from the method of the present invention.

That is, the conventional F CF S (First Come
In the multiplexing system based on the First 5evice), when multiplexing packets from the multiplex transmission line in the same output direction coming from the multiplex transmission line on the long side, the multiplexing is performed on a first-come, first-served basis. Also, when those packets arrived at the same time, the output packets were concentrated. However, in the present invention, concentration of output packets can be avoided by adding a dynamic delay to input packets.

(4-2) Embodiment FIG. 3 compares the conventional first-come, first-served packet multiplexing format (a) with the packet multiplexing format (b) of the present invention.

Here, 300 and 304 indicate lines corresponding to users, and as shown in the figure, the case where packets arrive periodically with the same phase is shown. 302 is a conventional multiplexing device, 306 is a multiplexing device of the present invention, 303 is a conventional multiplexing format, and 307 is a multiplexing format according to the present invention.

301 and 305 are user-compatible packets. (a)
is a method in which multiplexing is performed on a first-come, first-served basis, and packets that arrive at the same time are multiplexed in random order. Basically, when the output has a periodic structure in which every N packets are input to the same output transmission line as shown in Figure 2, the output also has a periodic structure, and as mentioned above, the capacity efficiency of the line decreases. may decrease.

On the other hand, in the multiplexing system of the present invention, input packets are dynamically assigned to slots on multiplexed links with a random delay amount according to a certain statistical law, as shown in the multiplex transmission line 307, so No structure remains. Therefore, the unfavorable packet arrival pattern in which packets on the same side are periodically concentrated as shown in FIG. 2 does not continue for a long time on the output multiplex transmission path, that is, on the next cross-connect input. Therefore, when the system of the present invention is applied to a network including the cross-connect device shown in FIG. 1, line accommodation efficiency can be improved with a small amount of buffer. However, due to the statistical nature of slot allocation, there is a possibility that packets will be discarded due to buffer overflow, but the discard rate can be made to a level that does not pose a practical problem by optimally designing the buffer amount.

FIG. 4 shows an example of a circuit implementing the present invention. This is shown in Figure 3 (b
) is an example of dynamic delay provision in the multiplexing device 306. 400 is an input packet, 401 is a 1:N selector, 402 is a delay circuit for one packet, 403 is a control unit that dynamically allocates a slot to an input packet, and 404 is an output packet. Then, the control unit 403 generates control data for determining how much delay is to be given to each input packet from the slot assigned to the immediately preceding packet according to statistical distribution.

By using this method, periodicity at the packet multiplexing level is reduced, and a cross-connect device can be realized with a small amount of buffer. Further, since the arrival phase of packets to the cross-connect device does not affect line accommodation efficiency, line accommodation design is easy.

(5) As described in detail of the invention, by applying the multiplexing method of the present invention to an ATM communication network including a cross-connect device, packets from the same output direction that appear on the input multiplex transmission path input to the cross-connect device The number of buffers required does not affect the line capacity, and the packets are dynamically distributed on the output multiplex transmission path, which is the input to the next-stage cross-connect switch. Since it does not affect the amount of communication required or the line accommodation efficiency, it has the advantage of making equipment economical and making network operation easier.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional multiplex transmission system, FIG. 2 is a block diagram showing the line accommodation status of a conventional cross-connect device, and FIGS. 3 (a) and (b) are packet multiplexing formats in the conventional example and the present invention. FIG. 4 is a block diagram showing an embodiment of the present invention. 100... Packet signal, 101... Line capacity monitoring circuit, 102... Multiplexing device, 103... Multiplex transmission line, 104... Cross-connect device, 105...
Demultiplexer, 106...user equipment (transmission side),
107...User device (receiving side), 108, 10
9...Packet route within the cross-connect device, 200
...Multiple transmission path (input side), 201...Packet,
202... Period of multiplexed packets (multiplicity),
203... Cross-connect device, 204... Buffer (FIFO), 205... Multiplex transmission path (output side), 300, 304... User support circuit, 301
, 305... User-compatible packet, 302... Conventional multiplexing device, 306... Multiplexing device of the present invention, 3
03, 307...Multiple transmission line, 400...Input packet, 401...1:N selector, 402...1
Packet delay circuit, 403... dynamic multiplexing and drawing unit, 4
04...Output packet.

Claims (1)

[Scope of Claims] A first means for detecting the arrival of a packet; a second means for calculating the required delay time according to a statistical distribution using the arrival of the packet detected by the first means as a trigger; and arrival. a variable delay means for giving a delay time calculated by the second means to a packet.