JPH06120970A - Multi-point communication system - Google Patents

Abstract

PURPOSE:To assemble a correct data packet using an ATM cell by deciding one of the value of control information inside the ATM cell and a range adoptable by the value between a first terminal and a second terminal. CONSTITUTION:VCI(virtual channel identifier) values sent from respective transmission terminals 3, 4 and 5 are different for VC links 7, 8 and 9 but are all equal for the VC link 6 after being converged at an ATM node 2. However, they are identifiable by using the identifiers of the terminals 3, 4 and 5. But when the terminals 3, 4 and 5 optionally decide the values of the multiplex identifiers of transmission cells, there is a dangerous possibility that the values coincide, by chance. Thus, the values of the multiplex identifiers and the range of the value utilizable by the respective terminals 3, 4 and 5 are negotiated and decided beforehand between the transmission/reception terminals by a signal procedure or an off-line procedure. Thus, the collision of the values of the multiplex identifiers can be prevented beforehand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipoint communication system in ATM communication.

[0002]

2. Description of the Related Art Recently, AT has been used as a network for realizing multimedia communication in which voice, data, images, etc. are integrated.
M (Asynchronous Transfer Mode) communication networks are being put to practical use. In this ATM communication network, information segmented into fixed lengths is put on a packetized cell, and a header, which is control information including routing information indicating the destination and route of this cell, is added to this cell, and the cell unit Is used to transmit and exchange information, which makes it possible to handle various media in a unified manner.

A communication connection between terminals in ATM communication is a virtual channel (VC).
Alternatively, it is called a virtual path (VP), and their identification in an ATM network or a terminal is determined by a VC identifier (VCI: Virtual chan) in an ATM header of a cell.
nel identifier) or VP identifier (VPI: Virtua)
l Path Identifier).

Further, in the future mp communication network, in addition to the conventional one-to-one individual communication as a form of communication, there are many information points such as one-to-many or many-to-many for the purpose of distributing or collecting information or conference communication. It is expected that there will be an increasing number of communication modes in which information is transmitted to multiple locations and information transmitted from multiple locations is transmitted to multiple locations. When providing such a communication service through an ATM communication network, the form of ATM connection in the network is as follows.
A method of simply using a plurality of point-to-point ATM connections and a method of directly using a point-multipoint or multipoint-multipoint ATM connection can be considered. In such a point-multipoint or multipoint-multipoint ATM connection, in the downstream direction (referred to as a direction in which communication information is distributed from one terminal to a plurality of terminals), a node that is a branch point for transmitting to each point is input. Copy the required number of cells and output each one to the appropriate route. At this time, the VPI and VCI values of the input cell are
VPI of copied cell by copying cell
And VCI values are the same, and it is generally necessary to change to a different value depending on the originally output route. On the other hand, considering the upstream direction (referred to as the direction in which information is collected from a plurality of terminals to one terminal), different VPIs and VCIs from different routes at a node serving as a confluence point (generally the same as a node serving as a branch point). The cell entered with the value is
All must be converted to the same VPI or VCI value and output to the same route. Such point-multipoint or multipoint-multipoint ATM
Providing a one-to-many or many-to-many communication service using a connection enables effective use of the VPI and VCI areas.

However, when a normal point-to-point ATM connection is used, the VPI or VCI value of the received cell is equal to that of the cell even if the receiving side terminal is communicating simultaneously with a plurality of terminals. By referring to these values, it depends on the transmission path,
It was possible to uniquely identify from which transmission terminal the cell was sent (which point-to-point ATM connection the cell belongs to). However,
Uplink communication (direction in which information is collected from multiple terminals to one terminal) when simultaneous communication is performed with multiple terminals using the point-multipoint or multipoint-multipoint ATM connection as described above. With regard to (2), the transmitting terminal cannot be identified from the VPI or VCI value of the receiving cell. This is because the VPI and VCI values (generally having different values at the time of transmission) of cells transmitted from different transmission terminals are converted to the same VPI and VCI values for all cells at the confluence node and transmitted on the same route. This is because it is sent and sent to one terminal. For example, in the case of packet data communication, the following problems occur. For example, in connection-type point-to-point data communication, when a transmitting side decomposes a data packet into a plurality of cells for transmission and the receiving side assembles these cells into data packets, the multiplexing in the AAL header is performed. By using the activation identifier (MID), it is possible to prevent cells belonging to different data packets from being mixed and to normally reproduce the data packet. However, the same VPI is transmitted from a plurality of transmitting terminals by using the point-multipoint connection as described above.
When a cell having a VCI value or a VCI value is received, the value of the multiplexing identifier given to a data packet from a different transmission terminal is not necessarily unique to all terminals, and the value may collide. It becomes difficult to specify. In that case, the VPI or VCI value and the MID value of the packets sent from different terminals are the same on the receiving side, so that the packets may not be assembled correctly.

[0006]

As described above, in the point-to-point connection, when assembling a plurality of cells as a data packet, a multiplexing identifier is used to prevent mixing of cells belonging to different data packets. It becomes possible to reproduce a normal data packet. However, like the point-multipoint connection, since the multiplexing identifier of each cell belonging to each data packet received from a plurality of transmission terminals is not necessarily unique to each data packet, a normal data packet can be obtained. It had the drawback that it could not be assembled.

The present invention has been made in view of the above circumstances, and control information such as a multiplexing identifier is used not only for identifying a plurality of packets belonging to a point-point connection but also for a multipoint connection. It is also intended to enable the receiving terminal to correctly reproduce the packets received from a plurality of transmitting terminals by also utilizing the identification of the transmitting terminal.

[0008]

In order to achieve the above object, the present invention provides an ATM communication system for transmitting ATM cells from a plurality of first terminals to a second terminal via a multipoint connection. Control information is provided in the cell, and means for determining between the value of this control information and at least one of the possible range of this value between each first terminal and second terminal is provided. It is characterized by.

[0009]

The ATM cell is transmitted from each first terminal to the second terminal. In particular, in order to make it easy to identify from which first terminal the ATM cell to be transmitted is transmitted, Between the first terminal and the second terminal, the value of the control information in the ATM cell or the means for determining the range of the value is assigned to each first terminal, or an agreement is made based on the designation with both terminals. . As a result, the second terminal side can easily assemble the ATM cells transmitted for each first terminal into an information packet based on the control information uniquely provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a multipoint communication system which is an embodiment of the present invention. In particular, this figure shows an example of communication between a large number of terminals and one terminal using a multipoint connection, that is, many-to-one communication. ATM nodes 2 from transmitting terminals 3, 4 and 5 to one receiving terminal 1
The cellized information is transmitted using a multipoint-point connection (one in which a large number of transmission lines are connected to the same transmission line) passing through. The VCI value of the cell transmitted from each transmitting terminal 3, 4, 5 generally takes different values (X, Y, Z) in the VC links 7, 8, 9 to which each transmitting terminal is connected. The VC links 6 after being converged by the ATM node 2 all have the same value U.
Therefore, the receiving terminal 1 cannot identify at all whether the transmitting terminal is 3, 4, or 5 only by the VCI value added to the transmitted cell, but the value of the multiplexing identifier can generally have different values. Therefore, it is possible to use this for identification of the transmitting terminals 3, 4, and 5. However,
If each transmitting terminal 3, 4, 5 arbitrarily determines the value of the multiplexing identifier of the transmitting cell, there is a risk that the values coincide with each other. Therefore, each transmitting terminal 3, 4 may be previously set by a signaling procedure or an offline procedure. The value of the multiplexing identifier that can be used by 4 and 5 and the range of the value are negotiated and determined between the transmitting and receiving terminals. Thereby, it is possible to prevent the collision of the values of the multiplexing identifiers.

FIG. 2 shows a form of information from the AAL-SDU layer to the ATM layer when the connection type packet communication by the ATM is realized.
The transmitting terminals 3, 4, and 5 shown in FIG. 1 create ATM cells by the method described below. AAL shown at the top of the figure
-SDU (ATM Adaptation Layer-Service DataUni
The t) section has a layer for processing with information data called service data. Upper sublayer C of AAL below
In the S (conversion subLayer) layer, AAL-SD
A CS layer header and trailer are added to the CS payload, which is the service data of the U part.

[0012] The CS-PDU (conversi
on sublayer-protcol Data Unit) is decomposed into units of 44 bytes, and SAR (segume) which is a lower sublayer of AAL
ntation and reassembly) layer to add header and trailer. Further, the SAR-PDU (segu obtained in this way
mentation and reassenbly) 48 bytes AT
A header of 5 bytes is added to the M layer, and the ATM cell is transmitted to the transmission line payload. That is, the ATM cells are finally created while adding specific information as the entire information data is finely divided into detailed parts. The receiving terminal 1 shown in FIG. 1 assembles a packet from an ATM cell by the reverse operation.

Next, each part will be briefly described with reference to the detailed configuration diagram of the ATM cell shown in FIG. At the beginning of the ATM cell, called an ATM header, contains 5-byte destination information and the like. The next SAR header is ST (Segmen
t Type) section, SN (serial number) section, and MID (Mess
age ID) department. The ST portion contains 2-byte information indicating whether the divided information data is the first one, the middle one, the last one, or the information completed in one cell. The SN portion contains, for example, information indicating the sequence number of the divided information data. The MID portion contains 10-byte information indicating which information data belongs to, for example, when a plurality of information data are transmitted. This MID part is called a multiplexing identifier.

In the SAR payload part, the divided 44
Contains byte information data. The last part is called the SAR trailer part and consists of the LI part and the CRC part. L
The I (Length Identifier) part is contained in the SAR payload. Contains 6 bytes of information indicating the length of the returned data. Finally, the CRC section contains an error correction code.

An ATM cell is composed of the above-mentioned parts. The transmitting terminals 3, 4, and 5 assign the same MID to the SAR-PDUs belonging to the same packet, and the receiving terminal 1 refers to the MID and SN of the cell to assemble each cell and correct. Packets can be reassembled.

FIG. 4 shows an example in which the receiving terminal 1 shown in FIG. 1 assigns MID values to 3, 4, and 5 to each transmitting terminal. The upper bits of the 10-bit MID value are used for identifying the transmitting terminal, and the lower bits are used for the multiplexing identifier in the transmitting terminal. The boundary between the upper and lower bits may be determined by the number of transmitting terminals or the number of multiplexing desired to be identified in the terminal. Alternatively, as another embodiment, the MI can be directly transmitted to each transmitting terminal.
The range of D value is from 000000000000 to 00000011
A method of designating as 10000001000 to 000001111, ... Is also conceivable. By allocating in this way, it becomes possible to easily discriminate which ATM packet belongs to which information packet of which transmitting terminal.

Next, V for realizing such a many-to-one communication
The C or VP connection setting and bandwidth management method will be described below. FIG. 5 is a diagram showing the configuration of a VC or VP connection when realizing many-to-one communication. Each transmitting terminal 10-14 sends out a cell stream to the VC (or VP) linked transmission lines 15-18 and 21 directly connected to them. The cell flows via the VC (or VP) linked transmission lines 15 to 18 are merged at the relay nodes 23 and 24, and VC (or V) respectively.
P) Transferred to the linked transmission lines 19 and 20.
Finally, a VC (or VP) linked transmission path 19-
The cell flow passing through 21 is merged into one at the relay node 25, sent out to the VC (or VP) linked transmission path 22, and finally transferred to the receiving terminal 26.

In this embodiment, each transmitting terminal 10
It is assumed that 14 traffic descriptors are now peak rates (expressed by the number of cells / unit time) P1 to P5. In this case, as a parameter expressing the traffic characteristics of the ATM cell flow guaranteed by each VC (or VP) link, the peak rate of the traffic descriptor of the transmitting node transmitting the ATM cell flow transferred on it is used. It is assumed to be Japanese. That is, the VC (or VP) linked transmission line 15
~ 18 and 21, peak rates P1 to P4 and P5 are respectively set to VC (or VP) linked transmission lines 15 to 18, and peak rates P1 + P2 and P3 + P4 are set to VC, respectively. For the transmission line 22 (or VP) linked, the peak rate P1 +
P2 + P3 + P4 + P5 are assigned.

Since the cell flow actually flowing into the network is monitored and controlled (policing control) at the entrance of the network so as to protect the traffic descriptor of the transmitting node which is transmitting it, the above bandwidth allocation is performed. By performing the above, the communication quality can be guaranteed.

Further, in consideration of the traffic fluctuation caused by the fluctuation of the arrival phase at the time of cell merging at the relay nodes 23 to 25, the above-mentioned peak rate is set as a parameter to be assigned to each VC (or VP) link. A margin may be added to the simple sum, and the margin may be allocated to the safe side.

In the next embodiment, the transmitting terminals 10-1
4 traffic descriptors are set (P1, A1) to (P5, A) of a peak rate (represented by the number of cells / unit time) and an average rate (represented by the number of cells / unit time).
5). In this case, ATMs guaranteed by VC (or VP) linked transmission lines 15 to 18 and 21
As the parameter expressing the traffic characteristics of the cell flow, the average rate of the transmission node is not taken into consideration, and the same peak rate as in the above-mentioned embodiment is used, but VC at which the cell flows merge
(Or VP) linked transmission lines 19, 20 and 2
A value smaller than the simple sum of peak rates is assigned to 2 in consideration of the statistical multiplexing effect. For example, V
For the transmission path 22 that is C (or VP) linked, P ′ = (P1 + P2 + P3 + P4 + P5) * X X = f (P1 to P5, A1 to A5), 0 <X <1 is assigned as the peak rate. Here, the function f is, for example, a conventionally known method (cited document: H. Esaki,
Others: "Simple and Efficient Admission Control inan A
TM Network ". GLOBECOM90,300.5, DEC., 1989. And H.Esa
ki: "Call Admission Control in ATM Networks", ICC92,
354.4, June, 1992.), a band is provided such that the peak of each transmitting terminal and the cell loss rate obtained on the safe side from the average rate and the multiplicity satisfy a predetermined communication quality.

Further, in consideration of the case where the peak rate of the merged cell streams exceeds P ', such as the case where all the transmitting terminals transmit the cell streams at the peak rate, it is shown in FIG. As described above, a device (shaping device) 28 that suppresses the peak rate of the ATM cell flow sent to the VC (or VP) linked transmission path 22 to P ′ or less may be installed in the relay node 27.

As for the VC (or VP) linked transmission lines 19 and 20, a simple sum of peak rates is assigned as in the first embodiment without expecting a statistical multiplexing effect. Is also good.

As described above, by performing the above-mentioned band allocation, the efficiency of band use is improved in consideration of the statistical multiplexing effect, and a predetermined communication quality is satisfied, which is a many-to-one ratio.
Communication becomes feasible.

Further, it is possible to determine the parameter to be assigned to each VC (or VP) link after taking into account all the traffic fluctuations at the time of cell merging and merging in the above-mentioned embodiment, statistical multiple effects, etc. The present invention can be variously modified within the scope of the gist thereof and is not limited by the above-described embodiments.

[0026]

As described above in detail, in the present invention, in the multipoint communication system, the value of the control information in the ATM cell or the possible range of the value is assigned to each first terminal. The second terminal can identify from which first terminal the transmitted ATM cell is transmitted, so that the ATM cell can be used to correctly assemble a data packet.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a multipoint communication system of the present invention.

FIG. 2 is a diagram showing an information form in ATM packet communication of the present invention.

FIG. 3 is a diagram showing an internal structure of an ATM cell of the present invention.

FIG. 4 is a diagram showing an example of MID value allocation to each transmission terminal of the present invention.

FIG. 5 is a diagram showing a configuration of a VC connection that realizes many-to-one communication of the present invention.

FIG. 6 is a diagram showing a configuration of a VC connection and a position of a shaping device for realizing the many-to-one communication of the present invention.

[Explanation of symbols]

 1, 26 ... Receiving terminal 2 ... ATM node 3, 4, 5, 10, 11, 12, 13, 14, ... Sending terminal

Claims (2)

[Claims] 1. ATM from a plurality of first terminals to a second terminal
A transmitting cells via a multipoint connection
In the TM communication system, control information is provided in the ATM cell, and at least one of a value of the control information and a range of the value is set between the first terminal and the second terminal. A multipoint communication system comprising means for determining between. 2. The second terminal is provided with means for identifying which first terminal the ATM cell was transmitted by referring to the control information in the ATM cell. The multipoint communication system according to claim 1.