JP2003143174A - Star network connection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a star network connection system capable of efficiently using bands of an ATM (asynchronous transfer mode) network when a MAC (media access control) frame to be transmitted is a broadcasting frame or when the MAC address of a transmission destination is unlearned as a star network connection system for connecting a head office (HO) to a plurality of branch offices (BO) stored in the HO like stars through ATM network. SOLUTION: In the star network connection system for connecting the HO to a plurality of BOs stored in the HO like stars, each terminal of the HO are stored in an HO subscriber's line terminal equipment (NT), the HO-NT is stored in the ATM network, the terminal of each BO is stored in a BO-NT, the BO-NT is stored in line terminal equipment (LT) through a PON, and the LT is stored in the ATM network.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ATM (Asynchronous).
nous Transfer Mode) A head office and a plurality of branch offices accommodated in a star shape are connected to the head office via a network, and between the head office or terminal devices arranged in the branch office. MAC
(Media Access Control) The present invention relates to a star network connection system for temporarily converting an ATM cell into an ATM cell and transmitting the ATM cell, particularly when a transmitted MAC frame is a broadcast frame or when a destination MAC address is unlearned. The present invention relates to a star network connection system capable of efficiently using a band on an ATM network.

In recent years, transmission between computers, such as transmission between personal computers installed in offices and homes, transmission between database servers and clients, has become popular. In particular, a single office is the head office and the rest are branch offices.
An increasing number of offices have star network connection systems that connect multiple offices in a star pattern.

The plurality of offices forming the star network connection system are not necessarily geographically close to each other, and in the most typical example, they may be located in a plurality of countries. In order to configure a star network connection system between such remote offices, it is necessary to accommodate each office in the public network. The ATM method has been put into practical use as a transmission method suitable for transmitting multimedia such as voice, data, and images. Since the transmission between the computers is often multimedia transmission including voice, data, and images, a star network connection system between remote offices is often constructed via an ATM network.

In the above system, when transmitting information from the head office to a plurality of branch offices,
In the case of broadcasting purpose or in the case where the head office has not learned the MAC address of the terminal on the branch office side even in the single cast mode, it is installed in the branch office in the broadcast mode or the multicast mode. The same information is transmitted to a plurality of terminals. At this time, it is important that the band on the ATM network can be used efficiently.

[0005]

2. Description of the Related Art FIG. 14 shows a conventional remote LAN (Local Ar).
FIG. 2 shows a case of connecting a head office and a plurality of branch offices point-to-point in a connection form (part 1) between ea networks). In FIG. 14, 1, 1a and 1b are terminal devices installed in the head office, and 2 is a head office subscriber line terminating device installed in the head office.

Reference numeral 3 is an ATM switching network, which is an ATM switching system 3-
1, 3-2, 3-3, 3-4, 3-5, and FIG.
3 shows an example of configuring a physical network indicated by a thin solid line. Reference numeral 8 is a branch office subscriber line terminating device installed in the branch office, and 9 is a terminal device installed in the branch office. Similarly, 8a is a branch office subscriber line terminating device installed in another branch office, and 9a is a branch office subscriber line terminating device.
A terminal device installed in the same branch office as the office subscriber line terminating device 8a, 8b a branch office subscriber line terminating device installed in another branch office, and 9b a branch office subscriber line terminating device. Device 8
It is a terminal device installed in the same branch office as b. In FIG. 14, only one terminal device installed in each branch office is shown in each branch office, but this is only for the purpose of simplifying the drawing. Multiple terminal devices are installed in the office.

A LAN is constructed in the head office and in each branch office. It should be noted that the LAN may have any form such as a star, a bus, or a ring. In FIG. 14, a head office subscriber line terminating device 2 and a branch office subscriber line terminating device 8,
Each of 8a and 8b has a LAN interface such as Ethernet (registered trademark) inside the office and an ATM interface outside the office. Then, the head office subscriber line terminating device 2 transmits the MA transmitted by the terminal devices 1, 1a and 1b.
It has a function of reconstructing a C frame into an ATM cell having a fixed length of 53 bytes and transmitting it to the ATM switching network 3, and reconstructing an ATM cell received from the ATM switching network 3 into a MAC frame and transmitting it to a destination terminal device. . That is, the head office subscriber line terminating device 2 and the branch office subscriber line terminating devices 8, 8a and 8b have a bridge function.

The relationship between the MAC frame and ATM cell will be described later. Now, in the configuration of FIG.
The office subscriber line terminator 2 and the branch office subscriber line terminators 8, 8a and 8b are connected by ATM point-to-point connections C ₁ , C ₂ and C ₃ as shown by the thick broken lines in FIG. Are connected, and each subscriber line terminator connects each connection to a bridge
Treated as a port, IEEE (Institute of Electrica
l and Electronic Engineering) Learning by MAC address, forwarding and filtering are performed according to the specification of 802.1D.

Here, the learning means the source address of the MAC frame received from a certain port and the identification information of the port that has received the MAC frame (in this case, LAN).
Interface number. ) Is stored in the memory of the subscriber line termination device each time a MAC frame is received. That is, the memory indicates to which port of the subscriber line termination device the terminal device having the MAC address is connected, and is called a learning table.

For example, the terminal device 1 on the head office side in FIG. 14 is the MA of the terminal device 9 on the branch office side.
When the MAC frame is transmitted to the head office subscriber line terminating device 2 with the C address as the destination, the head office subscriber line terminating device 2 receives the MA in the MAC frame.
When the C address is compared with the learning table in the head office subscriber line terminating device 2 and it is determined that the terminal device 9 is connected to the end of the port corresponding to the connection C ₁ , The MAC frame is edited into an ATM cell and transmitted only to the connection C ₁ . This is forwarding.

On the other hand, when the port corresponding to the MAC address is the port received by the head office subscriber line terminating device 2, the MAC frame need not be transferred and is discarded. This is filtering.
When the branch office subscriber line terminating device 8 receives the MAC frame converted into ATM cells by the head office subscriber line terminating device 2, the learning table in the branch office subscriber line terminating device 8 is referred to. If the destination MAC address is the MAC address of the terminal device connected to the LAN side interface, the ATM
The cell is reassembled into a MAC frame and transmitted to the terminal device 9 through the LAN.

FIG. 15 shows a case of connecting a head office and a plurality of branch offices point-to-multipoint in a conventional LAN-to-LAN connection mode (No. 2). The hardware configuration of the network in FIG. 14 and the hardware configuration of the network in FIG. 15 are exactly the same, so description of the configuration will be omitted.

In FIG. 15, the head office and a plurality of branch offices are not connected by a fixed connection,
Each time communication is performed by the ATM exchanges 3-1 to 3-5
The form which connects the head office and the branch office by selecting the outgoing line of the M switchboard is shown. For example, the head office subscriber line terminating device 2 is an ATM switch 3-
1 and the branch office subscriber line termination device 8 is accommodated in the ATM exchange 3-3, and the branch office subscriber line termination device 8a is accommodated in the ATM exchange 3-.
4 and the branch office subscriber line terminating equipment 8b is accommodated in the ATM switch 3-5. Now, the head office subscriber line terminating equipment 2 and the branch office subscriber line terminating equipment 8b are accommodated.
The office subscriber line terminating device 8 is an ATM exchange 3-1 or A.
The head office subscriber line terminating device 2 and the branch office subscriber line terminating device 8a are connected via the ATM exchange 3-2 and the ATM exchange 3-3, and the ATM exchange 3-
1, the ATM switch 3-2 and the ATM switch 3-4 are connected, and the head office subscriber line terminating device 2 and the branch office subscriber line terminating device 8b are connected to the ATM switch 3-1 and the ATM switch 3-. 5 is assumed to be connected.

Also in this case, if the head office subscriber line terminating device 2 has learned the MAC address of the terminal device 9 in the single cast mode, the head office subscriber line terminal 2 is in the same manner as described with reference to FIG. Transmission takes place between the subscriber line terminator 2 and the branch office subscriber line terminator 8.

[0015]

When the MAC address of the terminal device 9 is not learned in the learning table of the head office subscriber line terminating device 2 in the transmission process of the embodiment shown in FIG. The office subscriber line terminating device 2 transmits the MAC frame to all ports other than the LAN side port that has received the MAC frame. In this case, the connection C _{1 of} FIG.
ATM by copying the same MAC frame to C ₂ and C ₃
Send to the net.

Further, for example, the terminal device 1 on the head office side is in the broadcast mode or the multicast mode.
A MAC frame whose destination is a MAC address indicating a mode (hereinafter, the broadcast mode and the multicast mode will be referred to as a broadcast mode).
When transmitted to the office subscriber line terminating device 2, the head office subscriber line terminating device 2 sends the MA to all ports other than the LAN side port that received the MAC frame.
Send C frame. In other words, even in this case,
The same MAC frame is copied to the four connections C ₁ , C ₂ and C ₃ and transmitted to the ATM network.

Further, in the transmission processing in the form of FIG. 15, in the case of the broadcast mode or when the learning of the MAC address of the destination terminal device has not been completed in the single cast mode, all except the port which received the MAC frame. In order to transfer the MAC frame to the port of the above, the head office subscriber line terminating device 2 transmits the MAC frame to the ATM switch 3-1 and the ATM switch 3-
In order to output the same MAC frame to the ATM exchange 3-2 side and the ATM exchange 3-3 side, 1 transmits the same MAC frame by copying it. The ATM exchange 3-2 has the same M on the ATM exchange 3-3 side and the ATM exchange 3-4 side.
The MAC frame is copied and transmitted to output the AC frame, and the ATM exchange 3-5 receives the received MAC.
Send the frame as is.

Therefore, only one MAC frame needs to be transmitted between the head office subscriber line terminating device 2 and the ATM switching network 3, but each time the connection is branched in the ATM switching network 3, the MAC frame is transmitted. Must be copied and sent. Therefore, in the configurations of FIGS. 14 and 15, in the broadcast mode or when the learning of the destination MAC address has not been completed, there arises a problem that the band in the ATM switching network is wasted.

In view of such a problem, the present invention connects a head office and a plurality of branch offices accommodated in a star shape in the head office via an ATM network,
Regarding a star network connection system in which a MAC frame is temporarily converted into an ATM cell and transmitted between terminal devices arranged in the head office or the branch office, when the transmitted MAC frame is a broadcast frame, An object of the present invention is to provide a star network connection system capable of efficiently using the band on the ATM network even when the MAC address of the destination terminal device is unlearned.

[0020]

The first invention is a star network connection system for connecting a head office and a plurality of branch offices housed in a star shape in the head office via an ATM network. Head
Each terminal of the office is accommodated in the head office subscriber line termination device, the head office subscriber line termination device is accommodated in the ATM network, and each terminal of the plurality of branch offices is accommodated in the branch office subscriber. It is accommodated in the line terminating equipment, and the branch office subscriber line terminating equipment is PON
It is a star network connection system characterized in that it is accommodated in a line terminating device via a (Passive Optical Network), and the line terminating device is accommodated in the ATM network.

According to the first aspect of the invention, each terminal of the head office is accommodated in the head office subscriber line terminating device, the head office subscriber line terminating device is accommodated in the ATM network, and a plurality of branches are provided. Each of the office terminals is accommodated in a subscriber line terminating device, the subscriber line terminating device is accommodated in a line terminating device via a PON, and the line terminating device is accommodated in the AT.
Since it is accommodated in the M network, when a branch office subscriber line terminator on the side of a plurality of branch offices is seen from the head office subscriber line terminator, a single line terminator can be seen from the head office side. Therefore, even when transmitting in the broadcast mode to the terminal devices installed in multiple branch offices, the head office subscriber line terminating device uses the MAC address of the specific terminal device of the specific branch office. Even when learning is not performed, the MAC frame to be transferred only needs to be transferred to a single line termination device, and the band on the ATM switching network can be used efficiently.

A second invention is the star network connection system of the first invention, wherein the line terminating device comprises:
The VPI / VCI in the ATM cell received from the branch office subscriber line terminating device is the terminal side VPI / VCI.
The ATM cell is stored in the storage unit, the storage position in the VPI / VCI storage unit on the terminal side is calculated, padded as a PON downlink destination identifier, and the received ATM cell is transmitted to the ATM switching network. AT received
A star network connection characterized by extracting a PON downlink destination identifier padded in an M cell and extracting a VPI / VCI of a branch office subscriber line terminating device as a destination by using the PON downlink destination identifier as a key System.

According to the second invention, the line terminating device receives the ATM from the branch office subscriber line terminating device.
The VPI / VCI in the cell is stored in the VPI / VCI storage unit on the terminal side, the storage position in the VPI / VCI storage unit on the terminal side is calculated, padded as the PON downlink destination identifier, and the received ATM cell is exchanged with the ATM. Since it is transmitted to the network, a learning table can be created by the PON downlink destination identifier, the source MAC address, and the receiving port in the head office subscriber line terminating device, and the ATM cell is received from the ATM switching network. Sometimes the PO padded in the received ATM cell
The VPI / VCI of the destination can be obtained using the N downlink destination identifier as a key.

A third invention is the star network connection system of the first invention, wherein when the head office subscriber line terminating device receives an ATM cell from the ATM switching network, the line is transmitted from the ATM cell. A PON downlink destination identifier padded by the terminating device, a source MAC address, and a receiving port create a learning table, and when a MAC frame is received from the terminal device, the MAC address in the MAC frame is used as a key in the learning table. The stored PON downlink destination identifier is extracted and the PON is extracted.
A star network connection system characterized by padding a downlink destination identifier and transmitting an ATM cell to an ATM switching network.

According to the third invention, the head office subscriber line terminating device has a PON downlink destination identifier padded by the line terminating device from an ATM cell received from the ATM switching network, a source MAC address, and a receiving port. Since the learning table is created by using the MAC address in the MAC frame received from the terminal device in the head office as a key, the PON downlink destination identifier stored in the learning table is extracted, and the PON downlink destination identifier is extracted. Can be padded to send ATM cells to the ATM switching network.

A fourth invention is the star network connection system of the third invention, wherein the head office subscriber line terminating device has a PON downlink destination when the broadcast mode or the destination MAC address is not learned. Identifier and VPI
/ VCI is a star network connection system characterized by setting a specific value and transmitting downlink ATM cells.

According to the fourth aspect of the invention, when the head office subscriber line terminating device has not learned the broadcast mode or the destination MAC address, the PON downlink destination identifier and VPI /
Since a specific value is set as the VCI and the downlink ATM cell is transmitted to the line termination device, the broadcast mode or the destination MAC is set.
Even when the address is not learned, the band on the ATM switching network is not wastefully used.

A fifth invention is the star network connection system of the second invention, wherein the line terminating device is
When the PON downlink destination identifier has a specific value, a VPI / VCI corresponding to the specific PON downlink destination identifier is set and an ATM cell is transmitted to the PON. According to the fifth aspect, when the PON downlink destination identifier has a specific value, the line terminating device has a VP corresponding to the specific PON downlink destination identifier.
Since the I / VCI is set and the ATM cell is transmitted to the PON, the ATM cell can be transmitted to all the branch office subscriber line terminators under the control.

[0029]

DETAILED DESCRIPTION OF THE INVENTION The technique of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration of a star network connection system of the present invention. In FIG. 1, 1, 1
Reference numerals a and 1b are terminal devices installed in the head office, and 2 is a head office subscriber line terminating device installed in the head office.

Reference numeral 3 is an ATM switching network. Since the specific configuration of the ATM switching network 3 is not essential to the present invention, the specific configuration of the ATM switching network 3 is omitted in FIG. 1, and the ATM switching network 3 is a single ATM switch. It is shown as it is. Reference numeral 4 is a line terminating device. Reference numeral 8 is a branch office subscriber line terminating device installed in the branch office, and 9 is a terminal device installed in the branch office. Similarly, 8a is another branch
A branch office subscriber line terminating device installed in an office, 9a is a terminal device installed in the same branch office as the branch office subscriber line terminating device 8a, and 8b is installed in another branch office. Branch office subscriber line terminating equipment, 9b
It is a terminal device installed in the same branch office as the office subscriber line terminating device 8b. In FIG. 14, only one terminal device installed in each branch office is shown in each branch office, but this is only for the purpose of simplifying the drawing.
Multiple terminal devices are installed in the office.

A LAN is constructed in the head office and in each branch office. Where LA
The shape of N may be any of a star shape, a bus shape, a ring shape, and the like. In addition, in order to show the simplest configuration, an example is shown in which the terminal device is accommodated in each branch office in the branch office subscriber line terminating device, but the branch office subscriber line terminating device includes a plurality of branch offices. -It can also accommodate terminal equipment in the office.

Reference numerals 7, 7a and 7b denote branch office side PON interfaces connected to the branch office subscriber line terminators 8, 8a and 8b, respectively.
6a and 6b are passive branching devices, 5, 5a and 5b
Is a PON interface connected to the line terminating device 4. And the PON interfaces 7, 7a and 7b
And the passive branching device 6 are connected by a transmission line made of an optical fiber, and the passive branching device 6 and the PON interface 5 are also connected by a transmission line made of an optical fiber. That is, the PON is the PON interface 5, the passive branching device 6, the PON interfaces 7, 7a and 7b.
And an optical fiber transmission line. In addition, PON
Is a transparent transmission system,
Since the specific configurations of the interface 5, the passive branching device 6 and the PON interface 7 are irrelevant to the essence of the present invention, the PON interface 5, the passive branching device 6
The description of the specific configuration of the PON interface 7 will be omitted.

FIG. 2 shows the configuration of the branch office subscriber line terminating device. In FIG. 2, 8-1 is a MAC frame receiving unit that receives a MAC frame sent from the terminal device side, and 8-2 is a MAC frame that is correctly received by the MAC frame receiving unit 8-1 and is encapsulated according to RFC2684 specifications. , An AAL5 frame creation unit for constructing an RFC2684 encapsulated frame into an AAL (ATM Adaptation Layer) 5 frame, 8-3 is a PO
PON-side VPI / V that stores in advance VPI / VCI indicating N-side virtual path and virtual channel
CI storage unit (abbreviated as "PON side VPI storage unit" in the figure. Hereinafter, "VPI / VCI" is simply referred to as "V" in the figure.
PI ”. ), 8-4 is VPI / VC on the PON side
The VPI / VCI read from the I storage unit 8-3 is transferred to the ATM.
An ATM cell editing unit for setting the AAL5 frame into an ATM cell by setting it in the cell header, and 8-5 is an ATM cell for transmitting the ATM cell edited by the ATM cell editing unit 8-4 to the line terminating device via the PON. It is a transmitter.

Further, 8-6 is an ATM cell receiving section for receiving an ATM cell from the line terminating device via the PON, 8-7.
Is a receivable VPI / that stores its own VPI / VCI
VCI storage unit, 8-8 can receive VPI / VCI set in the header of the received ATM cell VPI / VCI
A filtering processing unit that compares the VPI / VCI read from the storage unit 8-7 and discards the received ATM cell if the two do not match (abbreviated as "filter processing unit" in the figure. , And 8-9 are extracted in the MAC frame from the ATM cells that have not been discarded by the filtering processing unit 8-8.
The AC frame extraction unit 8-10 is a MAC frame transmission unit that transmits the MAC frame extracted by the MAC frame extraction unit 8-9 to the terminal device side.

The configuration and function of the branch office subscriber line terminating device shown in FIG. 2 are the same as those of the conventional branch office subscriber line terminating device. Figure 3
Is a configuration of the line terminal device of the present invention. In FIG. 3, 4-1 is an AT that receives an ATM cell transmitted by the branch office subscriber line terminating device via the PON.
The M cell receiving unit 4-2 extracts and stores the VPI / VCI of the branch office subscriber line terminating device from the ATM cells received by the ATM cell receiving unit 4-1 and stores the PON.
A terminal-side VPI / VCI extraction unit that determines the storage location of the VPI / VCI stored as the downlink destination identifier, and 4-3 is a VPI / V extracted by the terminal-side VPI / VCI extraction unit 4-2.
Terminal side VPI / VCI storage unit for storing CI, 4-4 is ATM side VPI / VCI storage unit for storing VPI / VCI indicating the virtual path and virtual channel on the ATM switching network side in advance, 4-5 Is an ATM cell receiving unit 4-
The PON downlink destination identifier extracted by the terminal-side VPI / VCI extraction unit 4-2 is padded in the ATM cell received by the terminal 1 and the VPI / VCI read from the ATM-side VPI / VCI storage unit 4-4 is stored in the ATM cell. An ATM cell editing unit set in the header, and an ATM cell transmitting unit 4-6 for transmitting the ATM cells output by the ATM cell editing unit to the head office subscriber line terminating device via the ATM switching network.

Further, 4-7 is an ATM cell receiving unit for receiving an ATM cell from the head office subscriber line terminating device via the ATM switching network, and 4-8 is a PON downlink destination padded in the received ATM cell. Terminal-side VPI that reads the VPI / VCI of the branch office subscriber line terminator from the terminal-side VPI / VCI storage using the identifier as a key
/ VCI determination unit, 4-9 indicates the VPI / VCI of the branch office subscriber line termination device determined by the terminal side VPI / VCI determination unit 4-8 in the header of the ATM cell received by the ATM cell reception unit 4-7. Cell header setting part to set, 4
Reference numeral -10 is an ATM cell transmission unit for transmitting the ATM cell output by the cell header setting unit 4-9 to the branch office subscriber line terminating device via the PON.

The feature of the configuration of FIG. 3 is that the VPI / VC on the terminal side is
The I extraction unit 4-2 not only extracts the VPI / VCI of the branch office subscriber line terminating device and stores it in the terminal side VPI / VCI storage unit 4-3, but also of the branch office subscriber line terminating device. The VPI / VCI storing position is determined, padded as a PON downlink destination identifier, and the ATM cell is transmitted to the head office subscriber line terminating device via the ATM switching network.
The terminal-side VP using the PON downlink destination identifier padded in the ATM cell received by the CI determination unit 4-8 as a key
The VPI / VCI of the branch office subscriber line terminator is read from the I / VCI storage unit 4-3 and set in the header of the ATM cell in the cell header setting unit 4-9 to set the branch office subscriber line terminator. To send to.

The contents stored in the VPI / VCI storage unit on the terminal side are illustrated in FIG. FIG. 4 shows the configuration of the head office subscriber line terminating device of the present invention. In FIG.
2-1 is an AT from the line terminating device via the ATM switching network.
ATM cell receiving unit for receiving M cells, 2-2 is its own V
Receivable VPI / VCI storage unit storing PI / VCI, 2-3 are VPI / VCI set in the header of the received ATM cell, and VPI / VCI read from the receivable VPI storage unit 2-2. And a filtering processing unit that discards the received ATM cell if the two do not match, a MAC frame is extracted from the ATM cell that is not discarded by the filtering processing unit 2-3, and a transmission source A MAC frame extraction unit that stores the MAC address, the reception port, and the PON downlink destination identifier of the terminal device in the learning table, and 2-5 is the M of the source terminal device.
A learning table that stores an AC address, a reception port, and a PON downlink destination identifier, and 2-6 is a MAC frame transmission unit that transmits the MAC frame extracted by the MAC frame extraction unit 2-4 to the terminal device side.

Further, 2-7 is a MAC frame receiving section for receiving a MAC frame from the terminal side, and 2-8 is a MAC frame.
The PON downlink destination identifier is extracted from the learning table 2-5 using the destination MAC address set in the MAC frame output by the frame receiving unit 2-7 as a key, and AAL5
An AAL5 frame creation unit for constructing a frame, 2-9 is an ATM cell editing unit for editing the AAL5 frame output from the AAL5 frame creation unit 2-8 into an ATM cell, 2-1
0 indicates the ATM cell output by the ATM cell editing unit 2-9.
It is an ATM cell transmitting unit for transmitting to the line terminating device via the TM switching network.

The feature of the configuration of FIG. 4 is that the MAC frame extraction unit 2-4 not only extracts the MAC frame from the ATM cells not discarded by the filtering processing unit 2-3, but also the MAC address of the source terminal device. The receiving port and the PON downlink destination identifier are stored in the learning table 2-5, and the AAL5 frame creation unit finds the PON downlink destination identifier from the learning table 2-5 using the destination MAC address as a key and pads the AAL5 frame. It is in.

An example of the learning table is shown in FIG. The configuration of the branch office subscriber line termination device, the configuration and characteristics of the line termination device, and the configuration and features of the head office subscriber line termination device have been described above. The process of the line terminating device and the process of the head office subscriber line terminating device will be described in detail with reference to the flowcharts.

FIG. 7 is a flowchart showing the processing of the upstream MAC frame of the branch office subscriber line terminating device. Hereinafter, the processing of the upstream ATM cell of the branch office subscriber line terminating device will be described with reference to the reference numerals of FIG. S1. The MAC frame receiving unit monitors whether a MAC frame is received from the terminal device.

When no MAC frame is received (N
In o), the above monitoring is continued. S2. When the MAC frame is received from the terminal device in step S1 (Yes), the MAC frame receiving unit determines whether or not the received MAC frame has been correctly received. In the above determination, a CRC operation is performed on bits other than CRC (Cyclic Redundancy Check) bits inserted at the end of the MAC frame, and comparison with the CRC bit inserted at the end of the MAC frame is performed.
If they match, it may be determined that they have been normally received, and if they do not match, it may be determined that they could not be normally received.

S3. If the received MAC frame cannot be correctly received in step S2 (No), the received MAC frame is discarded and the process jumps to step S1. Now, in step S2, when the received MAC frame is correctly received (Yes), the received M frame is received.
The AC frame is finally edited into an ATM cell and transmitted. Here, the relationship between the MAC frame and the ATM cell will be briefly described.

FIG. 13 is a diagram showing the relationship between MAC frames and ATM cells. In FIG. 13, (1) indicates MA
It is a C frame. Although details of the MAC frame are not shown, as described above, the CRC bit is inserted at the end of the MAC frame, and the MAC address of the transmission source and the destination MAC address are set in the header portion of the MAC frame.

(2) is a MAC frame encapsulated by RFC2684. For the original MAC frame, a 3-byte LLC (Logical Link Control) header and a 3-byte OUI (Organization Unique Identi
fier) and 2-byte PID (Protocol Identifier)
And 2-byte PAD (Padding) is added. (3)
Is an AAL5 frame. The MAC frame that has undergone the RFC2684 encapsulation becomes the AAL5 payload, and the PAD and CPCS-PDU of 0 to 47 bytes are used.
(Common Part Convergence Sublayer-Protocol Data U
nit) Trailer is added. A CRC bit is inserted in the CPCS-PDU trailer.

(4) is an ATM cell. To edit an ATM cell, an AAL5 frame is sequentially divided into 48 bytes, and a 5-byte header is added to each 48-byte unit to sequentially construct an ATM cell having a fixed length of 53 bytes. Subsequently, the flowchart of FIG. 7 will be described. S4. If the received MAC frame can be correctly received in step S2 (Yes), the AAL5 frame creation unit performs RFC2684 capsulation on the received MAC frame, and S5. Further, PAD and CPCS-PDU trailer are added to create an AAL5 frame.

S6. The ATM cell editing section decomposes the AAL5 frame into 48 bytes to create a payload section of the ATM cell, and S7. A PON that is a VPI / VCI indicating a line terminating device, which is preset in the VPI / VCI storage unit on the PON side
The side VPI / VCI is read out, and S8. Create the header part of the ATM cell.

S9. The ATM cell transmission unit is step S8.
The ATM cell created in step 1 is transmitted to the PON addressed to the line terminating device, and a series of processing ends. Actually, when the process of step S9 is completed, the process jumps to step S1 to continue the process of the upstream ATM cell, but here, when the normally received MAC frame is edited into the ATM cell and transmitted, It has been described that the processing ends. This expression is the same in the following flowcharts.

FIG. 8 is a flowchart showing the processing of the upstream ATM cell of the line terminating device. Hereinafter, processing of the upstream ATM cell of the line terminating device will be described with reference to the reference numerals of FIG. S11. The ATM cell receiving unit monitors whether or not an ATM cell is received from the branch office subscriber line terminating device. Branch office subscriber line terminal to ATM
If the cell is not received (No), the above monitoring is continued.

S12. The ATM cell receiving unit receives the received A
It is determined whether the TM cell has been successfully received. The above determination is performed on the header of the ATM cell by HEC (Hedder).
Error Control) operation and CPCS of AAL5 frame
It can be done by doing a CRC check using the CRC bits inserted in the PDU trailer.

S13. AT received in step S12
When the M cell cannot be normally received (No), the received ATM cell is discarded and the process jumps to step S11. S14. In step S12, when the received ATM cell can be normally received (Yes), the ATM cell receiving unit temporarily stores the received ATM cell to wait for the subsequent processing time and sequentially reads it.

S15. The terminal side VPI / VCI extraction unit
It is determined whether the read ATM cell is the first ATM cell. The above determination is made by using the P in the header of the ATM cell.
It is possible by looking at the value of T (Payload Type). That is, the first received ATM cell with PT 0 is the first ATM cell, the other ATM cells with PT 0 are the subsequent ATM cells, and the ATM cell with PT 1 is the final AT cell.
It is an M cell.

S16. A read in step S15
If the TM cell is at the beginning (Yes), the terminal side V
The PI / VCI extraction unit stores the VPI / VCI set in the header of the ATM cell in the terminal side VPI / VCI storage unit, and S17. The position where the VPI / VCI is stored in the terminal-side VPI / VCI storage unit is determined as the PON downlink destination identifier.

S18. The ATM cell editing unit is step S
The PON downlink destination identifier determined in 17 is used as the first AT
RF in AAL5 frame of payload of M cell
Pad at a position corresponding to PAD in the C2684 header. S19. After the processing of step S18 is completed, or when it is determined in step S15 that the ATM cell is not the head ATM cell (No), the ATM cell editing unit determines that the ATM VPI
AT to VPI / VCI stored in / VCI storage
Overwrite the header of M cell.

S20. The ATM cell transmission unit performs step S
The ATM cell edited in 19 is transmitted to the ATM switching network. S21. The ATM cell editing unit determines whether all ATM cells have been edited and transmitted. The above determination can be made by determining whether or not the ATM cell with the PT of 1 is edited and transmitted.

If all the ATM cells have not been transmitted (No), the process jumps to step S14 to read the stored ATM cells and perform the subsequent processing.
On the other hand, when all the ATM cells have been transmitted (Yes), the series of processing is ended. FIG. 9 is a flowchart showing the processing of the upstream ATM cell of the head office subscriber line terminating device. Hereinafter, the processing of the upstream MAC frame of the head office subscriber line terminating device will be described with reference to the reference numerals of FIG.

S31. The ATM cell receiving unit monitors whether or not an ATM cell is received from the line terminating device via the ATM switching network. When no ATM cell is received from the line terminating device (No), the above monitoring is continued. S32. In step S31, when the ATM cell is received (Yes), the ATM cell receiving unit receives the received ATM cell.
The cell determines whether it has been successfully received.

The above determination can be performed in the same manner as described in step S12 of FIG. S33. When the ATM cell is not normally received in step S32 (No), the ATM cell is discarded and the process jumps to step S31. S34. In step S32, when the ATM cell is normally received, the filtering processing unit receives VPI
It is determined whether or not the ATM cell may be received by referring to the / VCI storage unit.

If the ATM cell should not be received (No), the process jumps to step S31. S35. In step S34, if the ATM cell may be received (Yes), the AAL5 frame creation unit
Assembling the AAL5 frame by removing the header part of the ATM cell, S36. A MAC frame is extracted from the AAL5 frame assembled in step S35, and S37. The source MAC address, the receiving port, and the PON downlink destination identifier are stored in the learning table.

S38. The MAC frame transmission unit transmits the MAC frame extracted in step S36 to the destination terminal device and ends the series of processes. FIG. 10 is a flowchart showing the processing of the downlink MAC frame of the head office subscriber line terminating device. Hereinafter, processing of the downlink MAC frame of the head office subscriber line terminating device will be described with reference to the reference numerals of FIG.

S41. The MAC frame receiving unit monitors whether a MAC frame is received from the terminal device.
When no MAC frame is received from the terminal device (No)
To continue the above monitoring. S42. When the MAC frame is received from the terminal device (Yes), it is determined whether the received MAC frame is normal.

The above determination may be performed as described above. S43. When it is determined in step S42 that the received MAC frame is not normal (No), the MAC frame receiving unit discards the received MAC frame and jumps to step S41. S44. If it is determined in step S42 that the received MAC frame is normal (Yes), the AAL5 frame creation unit determines whether the received MAC frame is a broadcast frame.

The above determination can be made based on whether or not a specific address indicating the broadcast is set in the destination MAC address. S45. If it is determined in step S4 that the received MAC frame is not a broadcast frame (No), A
The AL5 frame creation unit determines whether the destination MAC address is a learned MAC address.

The above determination is made by the destination MAC in the learning table.
It can be performed by searching the address and whether or not the destination MAC address is written. S46. If it is determined in step S45 that the destination MAC address is a learned MAC address (Yes), the learning table is searched using the destination MAC address as a key, and S47. The receiving port number and the PON downlink destination identifier are extracted.

S48. The AAL5 frame creation unit uses the PON downlink destination identifier extracted in step S46 as an RFC.
Pad the PAD of the 2684 header and set the receiving port number to assemble the AAL5 frame. S49. On the other hand, if it is determined in step S44 that the frame is a broadcast frame (Yes), and if it is determined in step S45 that the destination MAC address has not been learned (N).
The specific PON downlink destination identifier is RFC268.
The padding is done in the PAD of the 4th header and the receiving port number is set to assemble the AAL5 frame.

S50. When the process of step S48 or the process of step S49 is completed, the ATM cell editing unit sets the VPI / VCI corresponding to the receiving port to edit the ATM cell, and the ATM cell transmitting unit transmits the edited ATM cell. . S51. The ATM cell editing unit determines whether all AAL5 frames have been edited into ATM cells.

The above determination can be carried out depending on whether or not an unedited frame remains in the AAL5 storage section, which is attached to the ATM cell editing section and temporarily stores the AAL5 frame. When all the AAL5 frames have not been edited into ATM cells (No), the process jumps to step S50 and the processes of steps S50 and S51 are continued until all the AAL5 frames are edited into ATM cells.

Finally, when all the AAL5 frames are edited into ATM cells (Yes), the series of processing is terminated. FIG. 11 is a flowchart showing the processing of the downlink ATM cell of the line terminating device. Hereinafter, the processing of the downlink ATM cell of the line terminating device will be described with reference to the reference numerals of FIG.

S61. The ATM cell receiving section monitors whether or not an ATM cell is received from the head office subscriber line terminating device. When no ATM cell is received (N
In o), the above monitoring is continued. S62. When the ATM cell is received in step S61 (Yes), it is determined whether or not the received ATM cell is normal.

The above determination may be performed as described above. S63. When it is determined in step S62 that the received ATM cell is not normal (No), the received ATM cell is discarded and the process jumps to step S61. S64. When it is determined in step S2 that the received ATM cell is normal (Yes), the received ATM cell is temporarily stored, and the terminal-side VPI / VCI determination unit sequentially reads the temporarily stored ATM cell.

S65. The terminal side VPI / VCI determination unit
It is determined whether the read ATM cell is the first ATM cell. The above determination may be performed as described above. S66. When it is determined in step S65 that the read ATM cell is the first ATM cell (Yes),
The terminal side VPI / VCI determination unit extracts the PON downlink destination identifier from the position corresponding to the PAD of the RFC2684 header of the payload of the ATM cell.

S67. The terminal side VPI / VCI determination unit
PON downlink destination identifier is broadcast or destination MAC
It is determined whether or not the address has a specific value indicating that it has not been learned. S68. If it is determined in step S67 that the PON downlink destination identifier is not a specific value (No), the terminal-side VP
The I / VCI determination unit extracts the VPI / VCI of the virtual path and the virtual channel to the branch office subscriber line terminating device using the PON downlink destination identifier as a key, and sets the cell header together with the PON downlink destination identifier. Hand over to the department.

S69. On the other hand, in step S67, PON
When it is determined that the downlink destination identifier has a specific value (Yes
s), the terminal-side VPI / VCI determination unit is
The VPI / VCI corresponding to the N downlink destination identifier is extracted and passed to the cell header setting unit together with the specific PON downlink destination identifier. S70. The cell header setting unit sets (overwrites) the VPI / VCI extracted in step S68 or step S69 in the cell header of the ATM cell and passes it to the ATM cell transmission unit.

S71. The ATM cell transmission unit performs step S
The ATM cell received at 70 is transmitted to the PON. S72. The cell header setting unit determines whether all ATM cells have been processed. If all the ATM cells have not been processed (No), the process jumps to step S64 and each unit continues the subsequent processes.

On the other hand, when all the ATM cells have been processed (Yes), the series of processing is terminated. In the flowchart shown in FIG. 11, P in step S67
By determining whether the ON downlink destination identifier has a specific value,
Although the processing is branched to step S68 and step S69, the terminal side V including the PON tube destination identifier with a specific value is also included.
If the PI / VCI storage is created, step S67
Then step S69 becomes unnecessary.

FIG. 12 is a flowchart showing the processing of the downlink ATM cell of the branch office subscriber line terminating device. Hereinafter, processing of the downlink ATM cell of the branch office subscriber line terminating device will be described with reference to the reference numerals of FIG. S81. The ATM cell receiving unit 8-6 in FIG. 2 monitors whether or not an ATM cell is received from the line terminating device via the PON.

When no ATM cell is received (No)
To continue the above monitoring. S82. When the ATM cell is received in step S81 (Yes), the ATM cell receiving unit 8-6 determines whether or not the received ATM cell is normal. The above determination may be performed as described above. S83. If the received ATM cell is not normal in step S82 (No), the process jumps to step S81.

S84. AT received in step S82
If the M cell is normal (Yes), the filtering processing unit 8-8 extracts the VPI / VCI from the header of the received ATM cell, and S85. It is determined whether or not it is a specific VPI / VCI indicating that it is a broadcast or has not been learned.

S86. In step S85, the specific VPI
When it is determined that it is not / VCI (No), the filtering processing unit 8-8 determines whether or not it is VPI / VCI addressed to itself. If it is determined that the VPI / VCI is not addressed to itself (No), the process jumps to step S83.

S87. In step S86, the VP addressed to self
When the I / VCI is determined (Yes), the filtering processing unit 8-8 MACs the received ATM cell.
It is passed to the frame extraction unit 8-9, and the MAC frame extraction unit 8
-9 assembles an AAL5 frame from the received ATM cell, and S88. The RFC2684 header is removed from the AAL5 frame to extract the MAC frame, and the MAC frame is sent to the MAC frame transmission unit 8-10.

S89. MAC frame transmitter 8-10
Transmits the MAC frame received from the MAC frame extraction unit to the terminal device with reference to the destination MAC address.
In FIG. 12, the VP received in step S85 is received.
The process branches depending on whether or not the I / VCI is a specific VPI / VCI, but the specific VPI / VCI is also stored in the receivable VPI / VCI storage section in the same manner as the VPI / VCI addressed to itself. If so, step S85 becomes unnecessary.

As described above, the line terminating device of the present invention receives the ATM from the branch office subscriber line terminating device.
VPI from cell to branch office subscriber line terminator
/ VCI is extracted and stored in the VPI / VCI storage unit on the terminal side, the storage location of the VPI / VCI of the branch office subscriber line terminator is determined as the PON downlink destination identifier, and the PON downlink destination identifier is set to the upstream ATM. The cell is set in the cell and transmitted, and the head office subscriber line terminating device stores the received PON downlink destination identifier, the MAC address of the transmission source, and the reception port number in the learning table.

Therefore, when the head office subscriber line terminating device transmits to the terminal device on the branch office side, when the destination MAC address has been learned, the destination MAC address is transmitted.
The PON downlink destination identifier and the port number of the destination can be extracted by the address, and the PON downlink destination identifier is A
It is possible to set an ATM cell and transmit the ATM cell to the line terminating device.

On the other hand, when the head office subscriber line terminating device has not learned the destination MAC address and is in the broadcast mode, a specific PON downlink destination identifier is set and an ATM cell is transmitted to the line terminating device. You can On this occasion,
Since it is only necessary to send ATM cells to the line termination device,
There is no waste of bandwidth on the ATM switching network. The line terminating device receiving the ATM cell from the head office subscriber line terminating device, when the PON downlink destination identifier is not a specific value, should be transmitted from the terminal side VPI / VCI storage unit using the PON downlink destination identifier as a key. The VPI / VCI of the office subscriber line terminator can be extracted and sent to the branch office subscriber line terminator to which the received ATM cell should be sent.

On the other hand, when the PON downlink destination identifier has a specific value, the VPI corresponding to the specific PON downlink destination identifier
/ VCI can be set to send ATM cells to the branch office subscriber line terminator under it. Therefore, in both the single cast mode and the broadcast mode, the head office and the branch office can communicate with each other without wasting the bandwidth on the ATM switching network.

Finally, FIG. 1 shows the case where all branch offices accommodated in one head office can be accommodated in one line termination device, but all branch offices accommodated in one head office are shown. 1 branch office
It may not fit in one line termination device. This is the case where the number of branch offices is large and the PON specifications cannot be met.

In this case, in the broadcast mode or in the unlearned state, the head office subscriber line terminating device must specify a plurality of paths of the ATM switching network and transmit ATM cells to a plurality of line terminating devices. However, the bandwidth on the ATM switching network can still be used efficiently.

[0089]

As described above in detail, according to the present invention, the AT
A head office and a plurality of branch offices accommodated in a star shape are connected to the head office via an M network, and a MAC frame is transmitted between the head office or terminal devices arranged in the branch office. ATM once
Regarding a star network connection system for converting to a cell and transmitting, when a transmitted MAC frame is a broadcast frame or when a destination MAC address is unlearned, the band on the ATM network is efficiently used. It is possible to realize a star network connection system.

That is, according to the first invention, each terminal of the head office is accommodated in the head office subscriber line terminating device, and the head office subscriber line terminating device ATM is installed.
In the network, the terminals of each of the plurality of branch offices are accommodated in the subscriber line terminating equipment for each branch office, and the subscriber line terminating equipment is accommodated in the line terminating equipment via the PON. Since the equipment is accommodated in the ATM network, when the subscriber line terminating equipment on the branch office side is seen from the subscriber line terminating equipment on the head office side, the head
Since only a single line terminating device can be seen from the office side, even when transmitting in a broadcast mode to terminal devices installed in multiple branch offices, the head office side can select a specific branch office device. Even if the MAC address of the specific terminal device of No. 1 is not learned, it is only necessary to transfer the MAC frame to be transferred to a single line termination device, and the band on the ATM switching network can be used efficiently. .

According to the second aspect of the invention, the line terminating device transmits the VPI / VCI in the ATM cell received from the branch office subscriber line terminating device to the terminal side VPI / VCI.
The ATM cell is stored in the storage unit, the storage position in the VPI / VCI storage unit on the terminal side is determined, and the received ATM cell is padded as the PON downlink destination identifier and then received.
Since it is transmitted to the switching network, in the head office subscriber line termination device, the PON downlink destination identifier and the transmission source M
A learning table can be created by the AC address and the receiving port, and when the ATM cell is received from the ATM switching network, the VPI / VCI of the destination can be obtained using the received PON downlink destination identifier as a key.

According to the third aspect of the invention, the head office subscriber line terminating device receives the AT received from the ATM switching network.
Since the learning table is created by the PON downlink destination identifier padded by the line terminating device from the M cell, the source MAC address, and the receiving port, the MAC in the MAC frame received from the terminal device in the head office
The PO stored in the learning table using the address as a key
It is possible to extract the N downlink destination identifier, pad the PON downlink destination identifier, and transmit the ATM cell to the ATM switching network.

According to the fourth invention, when the head office subscriber line terminating device has not learned the broadcast mode or the destination MAC address, the PON downlink destination identifier and the VP
Since a specific value is set as the I / VCI and the downlink ATM cell is transmitted to the line terminating device, the broadcast mode or the destination M is transmitted.
Even if the AC address is not learned, the band on the ATM switching network is not wastefully used.

Further, according to the fifth invention, when the PON downlink destination identifier has a specific value, the line terminating device sets the VPI / VCI corresponding to the specific PON downlink destination identifier and sets the ATM cell to the PON. Since it is transmitted, ATM cells can be transmitted to all the branch office subscriber line terminators under the control.

[Brief description of drawings]

FIG. 1 is a configuration of a star network connection system of the present invention.

FIG. 2 is a configuration of a branch office subscriber line terminating device.

FIG. 3 is a configuration of a line terminal device of the present invention.

FIG. 4 is a configuration of a head office subscriber line terminating device of the present invention.

FIG. 5 shows contents stored in a VPI / VCI storage unit on the terminal side.

FIG. 6 shows an example of a learning table.

FIG. 7: Processing of an upstream MAC frame of a branch office subscriber line terminating device.

FIG. 8: Processing of an upstream ATM cell of a line terminating device.

FIG. 9 Upstream A of head office subscriber line terminator
Processing of TM cells.

FIG. 10: Processing of downlink MAC frame of head office subscriber line terminating device.

FIG. 11: Processing of a downlink ATM cell of a line terminating device.

FIG. 12: Processing of downlink ATM cells in a branch office subscriber line terminator.

FIG. 13 is a diagram showing a relationship between a MAC frame and ATM cells.

FIG. 14 shows a configuration of a conventional star network connection system (No. 1).

FIG. 15 shows a configuration of a conventional star network connection system (No. 2).

[Explanation of symbols]

1, 1a, 1b Terminal device 2 Head office subscriber line termination device 2-1 ATM cell receiving unit 2-2 Receivable VPI / VCI storage unit 2-3 Filtering processing unit 2-4 MAC frame extracting unit 2-5 Learning Table 2-6 MAC frame transmitting unit 2-7 MAC frame receiving unit 2-8 AAL5 frame creating unit 2-9 ATM cell editing unit 2-10 ATM cell transmitting unit 3 ATM switching network 3-1, 3-2, 3- 3, 3-4, 3-5 ATM switch 4 Line terminating device 4-1 ATM cell receiver 4-2 Terminal side VPI / VCI extractor 4-3 Terminal side VPI / VCI storage 4-4 ATM side VPI / VCI Storage section 4-5 ATM cell editing section 4-6 ATM cell transmitting section 4-7 ATM cell receiving section 4-8 Terminal side VPI / VCI determining section 4-9 Cell header setting section 4-10 ATM cell transmitting section 5 PON interface 6, 6a, 6b Branching device 7, 7a, 7b PON interface 8, 8a, 8b Branch office subscriber line terminating device 8-1 MAC frame receiving unit 8-2 AAL5 frame creating unit 8-3 PON side VPI / VCI storage section 8-4 ATM cell editing section 8-5 ATM cell transmission section 8-6 ATM cell reception section 8-7 Receivable VPI / VCI storage section 8-8 Filtering processing section 8-9 MAC frame extraction section 8- 10 MAC frame transmitter 9, 9a, 9b Terminal device

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5K030 GA19 HA10 HB14 HB29 HC14                       HD01 HD07 JA08 JL03 LB05                       LB19                 5K033 AA01 AA04 AA09 CB08 DB02                       DB19

Claims (5)

[Claims] 1. ATM (Asynchronous Transfer Mode)
What is claimed is: 1. A star network connection system for connecting a head office and a plurality of branch offices housed in the head office via a network, wherein each terminal of the head office is a head office subscriber. A line terminating device is accommodated, the head office subscriber line terminating device is accommodated in an ATM network, and each terminal of the plurality of branch offices is connected to a branch terminal.
It is accommodated in the office subscriber line terminator, and the branch office subscriber line terminator is PON
A star network connection system, which is accommodated in a line terminating device via an ive optical network and accommodates the line terminating device in the ATM network. 2. The star network connection system according to claim 1, wherein the line terminating device has a VPI (Vertual Path Identifier) / V in an ATM cell received from the branch office subscriber line terminating device.
CI (Vertual Channel Identifier) on the terminal side VPI / V
The VPI / VCI is stored in the CI storage unit and
The storage position in the storage unit is calculated, padded as the PON downlink destination identifier, and then the received ATM cell is
Branch office subscriber line terminating device which is transmitted to the TM switching network, extracts the PON downlink destination identifier padded in the ATM cell received from the ATM switching network, and uses the PON downlink destination identifier as a key A star network connection system characterized by extracting VPI / VCI of. 3. The star network connection system according to claim 1, wherein when the head office subscriber line terminating device receives an ATM cell from an ATM switching network, the AT
A learning table is created by the PON downlink destination identifier padded by the line terminating device from the M cell, the source MAC address, and the receiving port, and when the MAC frame is received from the terminal device, the MA
The PON downlink destination identifier stored in the learning table is extracted using the MAC address in the C frame as a key, and the P
ON Downlink destination identifier is padded and ATM cell is AT
A star network connection system characterized by transmitting to an M switching network. 4. The star network connection system according to claim 3, wherein the head office subscriber line terminating device has not learned the broadcast mode or the destination MAC address,
A star network connection system characterized in that a specific value is set as a PON downlink destination identifier and VPI / VCI to transmit a downlink ATM cell. 5. The star network connection system according to claim 2, wherein when the PON downlink destination identifier has a specific value, the line terminating device transmits a VPI / VCI corresponding to the specific PON downlink destination identifier. A star network connection system characterized by setting and transmitting an ATM cell to a PON.