JP2980172B2 - Connectionless communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connectionless data communication apparatus, and more particularly to an ATM (Ansynchronous Trunk).
ansfer Mode) The present invention relates to a connectionless communication device for transferring data in a connectionless manner in a network.

[0002]

2. Description of the Related Art LANs are connected using an ATM network.
Various systems for performing data transfer without connection have been proposed.

The conventional connectionless data transfer system is realized by a connectionless network 150 shown in FIG. This connectionless network 150 is an ATM
A plurality of user LANs, which are overlaid on the network, are composed of an edge device 151, a connectionless node (communication device) 152, and an address resolution server (ARS) 153.
154 are connected.

A PVC (Permanent virtual connection) is provided between the edge device 151 and the connectionless node 152 and between the connectionless nodes 152, respectively.
Connected by A fixed VPI (Vi) is provided between the edge device 151 and the connectionless node 152.
PVP (Permanentvir) using rtual path Identifier
tual Path). The connection topology between the connectionless nodes 152 does not need to be particularly limited, and is left to the discretion of the network operator. As a typical connection, there is a PVP method.

The edge device 151 is connected to a user LAN 154.
Terminates the user packet generated from the ATM, and transfers the user packet to the ATM in order to transfer the packet on the connectionless network 150.
Convert to cells. Conversely, ATM cells transferred on the connectionless network 150 are assembled into user packets and transferred to the user LAN 154.

[0006] The connectionless node 152 routes the ATM cells generated from the user packets in units of cells, and transfers the ATM cells generated from the user packets via the plurality of connectionless nodes 152 to the edge for terminating the destination user LAN 154. It plays the role of transferring to the device 151.

Next, a data transfer operation by the connectionless network 150 will be described. Here, the IP (Internet Protocol) shown in FIG.
l) Consider a datagram, and as the user LAN 15, a LAN constructed by an Ethernet (ethernet) link medium.

[0008] A user packet generated by a host belonging to a certain user LAN 154 has an IP header. In the IP header, as shown in FIG. 16A, the IP address of the source host of the user packet (host). (SA)
161 and the IP of the destination host of the user packet (host)
Address (DA) 162. This user packet has an Ethernet header and trailer added,
It is converted into an Ethernet frame as shown in FIG. The header for Ethernet includes IWU (InterW
or MAC (Media Access Control) address of the orking unit) and the MAC address of the transmission source. The Ethernet frame transmitted from the host to the user LAN 154 corresponds to the edge device 1 to which the user LAN 154 is connected.
Transferred to 51.

[0009] The edge device 151 is connected to a user LAN 154.
, The data link layer header and trailer added to the user packet are removed, and an IP datagram which is the original user packet shown in FIG. 16C is taken out. Then, the edge device 151 adds an intermediate protocol header and a trailer to the extracted IP datagram, and assembles an intermediate frame as shown in FIG. As a representative of the intermediate protocol, ITUI. 37
CLNIP / CLNAP frame recommended by
IPv6 (Internet Protocol vers) defined by ETF
ion 6) and the like.

As shown in FIG. 1D, the intermediate frame has a destination connectionless address 163 and a source connectionless address 164 defined only in the intermediate protocol in the header. These addresses are
A connectionless network address defined only in the connectionless network 150,
The one assigned to each edge device 151 and each connectionless node 152 that constructs 0 is used. That is, the destination connectionless address 163 is
User LAN where the destination host of the IP datagram exists
154 is a connectionless network address assigned to the edge device 151 connected to 154, and the source connectionless address is the connectionless network address of the edge device 151 connected to the user LAN including the host that generated the IP datagram. It is. In order to increase the size of the connectionless network 150 and reduce the size of the routing table in the connectionless node 152, the connectionless network address adopts a hierarchical address configuration based on geographical division. ing.

When constructing the intermediate frame, the edge device 150 sets the destination connectionless address 1
Address Resolution Server (ARS) 153 to get 63
Send an address resolution request packet to.

The address resolution server 153 associates the destination host's IP address 162 of the user packet with the destination connectionless address 163 defined in the connectionless network, and the source host's IP address 161 of the user packet. It manages the correspondence with the source connectionless address 164 defined in the connectionless network. Then, the address resolution server 1
In response to the address resolution request from the edge device 151, 53 is the IP address 1 of the requested destination host.
The destination connectionless address 163 corresponding to 62 is retrieved from its own database, and notified to the requesting edge device 151 by an address resolution reply packet. Since the source connectionless address is an address fixedly assigned to the edge device in advance, the individual edge device 151 can know the address without inquiring the ARS 153.

The request source edge device 151 that has received the address resolution reply packet sends the destination connectionless address 16 corresponding to the IP address 162 of the destination host.
3 is obtained and written in the destination connectionless address field of the intermediate frame. In addition, its own connectionless network address is written in the source connectionless address field of the intermediate frame.

The edge device 151 is further provided in FIG.
As shown in (d), a header and a trailer are added to the intermediate frame and the CP of the AAL (ATM Adaptation Layer) 5 is added.
CS-PDU (Common part Convergence Sublayer-P
rotocol data unit) Assemble the frame, and AA
The data is divided into cells in units of 48 bytes by an L SAR (Segmentation reassembly sublayer).

The head cell of a series of ATM cells thus obtained is called BOM (Beginning of Message), and the last cell is called EOM (End of Message). Also, B
The cell located between OM and EOM is COM (Continua
of the Message).

As shown in FIGS. 16E and 17, the edge device 151 stores the same VPI / VCI (Virtual Path) in a series of ATM cells constituting the same AAL frame.
Connection), and transfer to the connectionless network 150 without breaking the order of BOM, COM, and EOM. Here, the VPI is fixedly assigned between the edge device 151 and the connectionless node 152 to be connected. The VCI is given a different value for each packet (for each ATM cell string) on this link.
It is used to identify the packet on the link, not the field corresponding to the connection. That is, the connection between the connectionless nodes 151 is a PVP connection based on a fixed VPI, but on each PVP, a VCI is allocated to each ATM cell row constituting a user packet. That is, the VCI is not an identifier corresponding to a connection as in a normal ATM network, but a field for identifying a user packet on the PVP between the connectionless nodes 151. Thus, each connectionless node 152 can identify individual user packets by referring to the VCI of the ATM header even if a plurality of user packets are mixed at the cell level, and perform different routing for each user packet. Becomes possible.

The connectionless node 152 has a plurality of input interfaces (IFs) and the same number of output interfaces (IFs), and performs packet switching routing by switching between them. That is, the connectionless node 152 transmits the first cell (BO
The routing can be determined with reference to the destination connectionless address and the source connectionless address included in M). This is because the header of the intermediate frame is included in the BOM. Thus, when the connectionless node 152 receives the BOM for each user packet, the connectionless node 152 can determine the routing to transfer the user packet, and the cell-based transfer can be performed without assembling the packet.

In the connectionless network 150,
All transfer functions are realized with reference to the destination connectionless address which is the connectionless network address described in the header of the intermediate frame. Hereinafter, this will be described in detail with reference to FIG.

As shown in FIG. 18, on a link 170 connecting the connectionless nodes 152 in the connectionless network 150, the same VCI is allocated to a series of ATM cells constituting the same packet. This series of ATM cells includes a BOM including the beginning of a packet, an EOM including the end of the packet, and zero or more COMs transferred between the BOM and the EOM. These BOM, CO
The order of M and EOM does not change within the same packet. The VCI assigned on a packet-by-packet basis is defined closed on each link 180, and has the purpose of identifying user packets transferred simultaneously on the same link. Therefore, the connectionless node 152
, When a new link 180 is switched to, a new VCI is allocated again in user packet units (FIG. 1).
8, VCI = α to VCI = β, VCI =
The assignment from γ to VCI = τ is performed).

As described above, the destination connectionless address 163 required for routing each user packet
Are included in the header of the intermediate frame and are located in the BOM, which is the head of the packet. Therefore, each connectionless node 152 can determine the routing of the user packet when receiving the BOM, and
The correspondence between I / VCI and routing is held in a cache. Thereafter, cells having the same VPI / VCI received on the same link 180 as the BOM reception follow the routing information held until the EOM reception. When an EOM having the same VCI is received, the correspondence between the VPI / VCI and the routing information is removed from the cache.

In the transfer from each connectionless node 152 to the edge device 150, the routing is performed in the same manner as described above, and the destination connectionless address 1
The transfer of the packet to the edge device 151 corresponding to 63 is performed.

The edge device 151, which has received a series of ATM cells constituting the user packet, collects a sequence of cells having the same VCI in order from BOM to EOM, assembles them into an AAL5 CSCP-PDU frame, and removes the header and trailer. Take out the intermediate frame. Further, the edge device 151 obtains the original user packet (IP datagram) by removing the header and the trailer from the intermediate frame.

The edge device 151 is connected to the user LAN 154
The side interface has a data link processing function of the user LAN interface. After assembling the user packet into an Ethernet frame, the user packet is transferred to the host specified by the IP address 162 of the destination host.

As described above, data transfer between user LANs is performed via the connectionless network.

[0025]

A first problem is that a conventional connectionless node relates to the transfer of ATM cells.
Since switching within the device is performed based on the input VPI / VCI, the input IF number, and the destination connectionless address in the BOM, the size of the routing table becomes the number of registrations of “the number of VPIs × the number of input IFs × the number of destination IWU addresses”. That is, the amount of information and the scale of processing of the switch unit become very large.

The second problem is that existing ATM cross-connects and ATM switches are VP switches and VC switches, respectively, and input IF numbers and input VPIs (input VCIs).
Since the connectionless device needs to further refer to the parameter specified by the destination connectionless address as compared with performing the switching process with reference to the above, the switch section of the ATM cross-connect or the ATM switch cannot be used as it is, The cost is high because special switches are required.

The present invention relates to an ATM cross connect and an ATM.
An object of the present invention is to provide an inexpensive connectionless communication device that can use a switch as it is and does not require a large routing table.

It should be noted that JP-A-8-46625, JP-A-6-85830, and JP-A-6-62038.
In various publications, various proposals regarding connectionless communication using ATM are made, but nothing is described about solving the above problem.

[0029]

According to the present invention, there is provided a connectionless communication apparatus used in a connectionless network, comprising a plurality of input IF sections, a plurality of output IF sections, a plurality of input IF sections, and a plurality of output IF sections. And a VP cross-connect section connected between the plurality of input IF sections.
Each of the units detects a destination connection address included in an input ATM cell, and outputs a first in-device VPI including information indicating an output IF unit and an output VPI corresponding to the destination connection address. The VCI area is defined, and the in-device VCI is defined in the VCI area of the ATM cell, the ATM cell is output to the VP cross-connect section, and the VP cross-connect section is connected to the VPI area of the input ATM cell. The VPI in the second device including the information indicating the input IF unit that has output the ATM cell and the information indicating the output VPI is converted into the VPI in the first device.
In addition to defining the PI, the first device VP
I, and outputs the ATM cell to an output IF unit designated by I. The plurality of output IF units
An output VPI is defined in the VPI area of the cell based on the information indicating the output VPI included in the second in-device VPI, and the output VPI is replaced in the VCI area in place of the in-device VCI.
It is characterized in that CI is defined and output to the outside.

The present invention also provides an ATM network with an overlay
Connected to each other to form a connectionless network
Used with connection edge device and address resolution server
In connectionless communications device is, N input IF section, and N output IF unit, connected between them
The ATM cells input to the N input IF units are
VP cross-connect output to any of the output IF sections
And a isolation portion, the input IF section, respectively, the AT
It is determined whether or not the M cell is a BOM.
A BOM detector that generates a reception notification , wherein the ATM cell is E
Determine whether it is OM, and if it is EOM, receive EOM
An EOM detector that generates a notification, which is included in the ATM cell
Output IF number corresponding to the destination connectionless address
Routing table for outputting a signal and an output VPI regression code, an in-device VCI pool for managing an in-device VCI ,
VPI and VCI included in the ATM cell, BO
M reception notification, the EOM reception notification, the output IF number,
Receiving the output VPI retraction code and the in-device VCI
The device VCI, the output IF number and the output
Cache table that outputs VPI regression code , before
The VPI included in the ATM cell is defined by the output IF number and
VPI in the input side device based on the output VPI retraction code
To the VPI selector and the ATM cell
VCI for replacing the included VCI with the in-apparatus VCI
Is composed of the selector unit, the VP cross-connect unit is filled prior to inclusion in the ATM cells from the input IF unit
When converting the VPI in the input device to the VPI in the output device
Output IF number corresponding to the VPI in the input side device
A cross-connect control unit for outputting the output IF number
The ATM cell to the corresponding output IF section based on the
An N × N cross-connect section for outputting, and the output IF sections are respectively provided from the VP cross-connect section.
If the ATM cell is determined to be a BOM or not,
BOM detecting unit for outputting a BOM receiving notification, the ATM cell
File is EOM, and if it is EOM, EOM
EOM detection unit for outputting reception notification, managing output VCI
Output VCI pool , V in the output side device of the ATM cell
PI and VCI in the device, the BOM reception notification, and the
A cache table that receives an EOM reception notification and outputs an output VCI, and stores an in-device VCI included in the ATM cell.
A VCI selector unit for replacing the output VCI,
Output VPI from output side device VPI included in TM cell
Decoding unit for decoding the data, an output device of the ATM cell
Selector for replacing the internal VPI with the output VPI
Is composed of parts, inside the connectionless communication device, the apparatus to the VPI area of the ATM cells input VPI
Defines, with using a VP switch for switching by referring to only the input IF number and VPI of the ATM cell in the N × N cross-connect unit, to define a device VCI to VCI area of said ATM cell, The output IF unit is characterized in that user packet unit identification is enabled by cell-based processing.

More specifically, the connectionless communication apparatus according to the present invention comprises an input IF unit, a VP cross-connect unit, and an output IF unit, and the input IF unit includes an EOM detection unit, a BOM detection unit, a routing table , A cache table, an in-apparatus VCI pool, a VCI selector, and a VPI selector. The BOM detector has a management table. The VP cross-connect unit includes a cross-connect control unit and an N × N cross-connect unit,
The cross-connect control unit includes a permanent VP switching table unit and a VPI conversion unit. The output IF unit includes an EOM detection unit, a BOM detection unit, a cache table, an output VCI pool, a VPI decoding unit, a VCI selector unit, and a VPI selector unit. The BOM detection unit has a management table. In addition, in order to transfer user packets using the VP cross-connect unit, an in-device VPI is defined in the connectionless communication device. This device VPI is classified into two types: a device VPI (input side) and a device VPI (output side). Also,
In order to identify a user packet when transferring a user packet in a connectionless communication device, an in-device VCI is defined in the connectionless node.

[0032]

The BOM detection unit 112 of the input IF unit 101 refers to the VPI / VCI of the received cell to manage whether or not a user packet is being received in the management table 501.
Even when using AAL5 in which a cell type other than M is not specified, BOM / COM of a user packet can be identified.

[0033] The EOM detector 111 detects the P of the ATM header.
The EOM is identified by monitoring the TI field. Upon receiving the BOM, the destination connectionless address is extracted from the header of the intermediate frame included in the BOM payload, and the routing table 113 is referred to based on the destination connectionless address described on the left. The routing table 113 includes a device address (output IF number) indicating the output IF unit 103 to which the cell is to be transferred in the connectionless node 152, and the transferred output I
A code (output VPI degeneration code) indicating the VPI assigned in the F unit 103 is output. By temporarily holding the output IF number and the output VPI degeneration code described in the left in the cache table 114, the same user packet (the same VPI / V
BO for COM and EOM that have CI)
The same transfer as performed in M can be performed.

The VP cross-connect unit 102 performs switching of user packets in the connectionless node 152 on a cell basis. VP cross connect part 1
A function 02 is a cross-connect function for a permanent VP of an ATM cross-connect device or an ATM switch.
2 is fixedly switched by the VPI. The ATM cell has its VPI rewritten in the VP cross-connect unit 102 and the output IF unit 1
03.

Here, in order to realize the processing of the user packet transfer using the fixed cross-connect function for the permanent VP based only on the information of the routing table 114 of the input IF unit 101, the definition of the in-device VPI is introduced. . The in-apparatus VPIs are classified into an in-apparatus VPI (input side) and an in-apparatus VPI (output side) with the VP cross-connect unit 102 in between. VPI (IN side) in device is input IF
It is provided by the unit 101 and is used for the following two purposes. One is to output the ATM cell as indicated by the routing table 113 of the input IF unit 101 to the output IF unit 1.
03. Second, the input IF unit notifies the output IF unit of the output VPI that is replaced by the output IF unit. The notification of the output VPI is not the VPI itself to be replaced but the output VPI which is degenerated information.
This is done through degenerate code.

On the other hand, the in-apparatus VPI (output side) is used for the following two purposes. One is to notify the output IF unit 103 of the device address (input IF number) of the input IF unit 101 of the transmission source. The second is that the output VPI degeneration code specified on the in-apparatus VPI (input side) is incorporated into the in-apparatus VPI (output side) to output IF
This is to notify the unit 103. The cross-connect control unit 130 of the VP cross-connect unit 102
The ATM cell is switched to the output IF unit 103 with reference to the (input side). At the same time, the VPI conversion unit 124 rewrites the in-apparatus VPI (input side) to the in-apparatus VPI (output side).

User packets arrive at the output IF unit 103 from a plurality of VP links of the plurality of input IF units 101 at the same time. The user packet of such simultaneous arrival is called AT
In order to correctly identify at the M cell level without any restrictions, a new intra-device VCI is defined together with the above-described intra-device VPI. The device VCI is the device V of the input IF unit 101.
The in-device VCI managed by the CI pool 115 and usable at the time of BOM reception is written to the cache table 114. The ATM cells of COM and EOM that constitute the BOM and the user packet including the BOM are rewritten to the corresponding in-device VCI held in the cache table 114 and transferred to the VP cross-connect unit 102.

BOM detection section 132 of output IF section 103
Are the ATM cell VCI and the device VPI (OUT
By managing the input IF numbers indicated in the side, the packet can be uniquely identified at the ATM cell level even when the maximum possible number of user packets arrives at the same time. The output IF unit 103 identifies a user packet from the input IF unit 101 that differs depending on the input IF number of the VPI (OUT side) in the device of the receiving cell, and identifies the user packet from the same input IF unit 101 by the VCI in the device. Do. BO performed by output IF section 103
The identification of the cell type of M, COM, EOM is performed by the input IF unit 1
01 is the same as the processing performed by the BOM detection unit 112 and the EOM detection unit 111. The output VCI pool 134 manages VCIs to be given to user packets to be output, and outputs VCIs corresponding to in-device VCIs during BOM transfer.
And the output VCI is transferred to the output pool 134 during the EOM transfer.
Return to The VPI decoding unit 135 outputs the VP in the ATM cell device.
The output VPI degeneration code of I (OUT side) is decoded into a 12-bit VPI,
Perform I conversion.

As described above, by using the VP cross-connect unit 102 having the cross-connect function of the permanent VP,
It is possible to transfer user packets on an ATM network in cell units, and even when the maximum number of user packets are simultaneously relayed in the connectionless node 152, it can be realized without any restrictions.

[0040]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the connectionless communication device (node) of the present invention. 1 is applied to the conventional connectionless network 150 shown in FIG. This connectionless node has N (# 1 to #N) input IFs (interfaces).
Unit 101 and the VPs connected to these input IF units 101
Cross-connect unit 102 and VP cross-connect unit 10
N (# 1 to #N) output IF units 103 connected to
And Input IF unit 101 and output IF unit 10
In each of 3, a unique device address (input IF number, output IF number) used in the connectionless node is set in advance.

The input IF unit 101 corresponds to an input physical link, and includes an EOM detection unit 111 and a BOM detection unit 11.
2, routing table 113, cache (chach
e) Table 114, in-device VCI pool 115, VC
An I selector unit (SEL) 116 and a VPI selector unit (SEL) 117 are provided. Further, the BOM detection unit 112 has a management table described later.

The VP cross connect section 102 includes N cross connect control sections 121 and N × N cross connect sections 122 respectively corresponding to the N input IF sections. The cross-connect control unit 121 includes a PVP switching table 123 and a VPI conversion unit 124.

The output IF unit 103 corresponds to an output physical link, and includes an EOM detection unit 131, a BOM detection unit 132, a cache table 133, an output VCI pool 134,
PI decoding unit 135, VCI selector unit 136, and VP
An I selector 137 is provided. In addition, the BOM detection unit 132 has a management table described later.

In the connectionless node of this embodiment, as shown in the upper part of FIG. 1, VPI and VCI are replaced. That is, each input IF unit 101 converts the input VPI and VCI of the cell into an in-device VPI (input side).
And VCI in the device. Further, the VP cross-connect unit 102 converts the in-device VPI (input side) into the
Replace with I (output side). Further, the output IF unit 103
Replaces the in-apparatus VPI (output side) and the in-apparatus VCI with the output VPI and output VCI, respectively. By performing such replacement of the VPI and the VCI, a general-purpose ATM cross-connect or ATM switch can be used, and the load on the cross-connect unit can be reduced.

The replacement of the VPI of the ATM cell in the connectionless node will be described below.

The VPI (input VPI) of the ATM cell input to the connectionless node 152 is
01 is rewritten to the in-device VPI (input side) by the VPI selector unit 117. Thereafter, the in-device VPI (input side) is converted by the VPI conversion unit 124 of the cross-connect control unit 121 of the VP cross-connect unit 102 into the in-device VPI.
(Output side). Furthermore, VPI in the device
(Output side) is the VPI selector unit 1 of the output IF unit 103.
At 37, it is rewritten to the output VPI.

The reason for introducing the in-device VPI (input side / output side) is that the VPI having a fixed cross-connect function by VP is used.
Using the P cross connect unit 102, the input IF unit 10
The packet is routed based on the routing information determined in step S1.
This is because the replacement with the PI is performed.

The in-device VPI (input side) is used for the following two purposes.

One is that the ATM is sent to the output IF unit 103 specified by the routing table 113 of the input IF unit 101.
This is for transferring the cell, that is, notifying the VP cross-connect control section 121 to which output IF section 103 the cell should be transferred. For this reason, the VPI (input side) in the apparatus is connected to the target output IF unit 1 as shown in FIG.
It has an in-apparatus address (output IF number) field of 03.

The other is that the VPI to be replaced when transferred from the output IF unit 103 to the physical link is
This is to notify the output IF unit 103 via the cross connect unit 102. This notification will be sent to the VP
This is performed using an output VPI degeneration code which is degenerated information instead of I itself. The output VPI degeneration code is
As shown in FIG. 2, it is defined by an in-device VPI (input side).

Here, the reason for using the degenerate code will be described. In this type of connectionless network (see FIG. 15), the VPI is used to identify the connection between the connectionless nodes 152, and only a few VPIs are defined per physical link. Therefore, VPI is set to 1
There is no problem even if it is reduced to information of several bits instead of having it as 2 bits of information, and the amount of transfer information can be reduced, which is efficient. For example, three Vs per physical link
If PI (= XXX, YYY, and ZZZ) is defined, VPI degeneration codes = 0, 1, and 2
= XXX, YYY, and ZZZ can be specified by 2-bit information.
Of course, finally, the output VPI
At the stage of replacement, in the VPI decoding unit 135, the output VPI degenerate code is decoded into a 12-bit VPI,
The VPI selector unit 137 changes the VPI.

On the other hand, the in-apparatus VPI (output side) is used for the following two purposes.

One is to notify the output IF unit 103 of the device address (input IF number) of the input IF unit 101 of the transmission source. For this purpose, the VPI in the device (output side)
, An input IF number field is defined as shown in FIG. The information written in this input IF number field is the number of the input IF unit 101 connected to each cross connect control unit 121, and is therefore fixed for each cross connect control unit 121. Here, N
× N cross connect unit 122 is used and the input IF
Since the number of units 101 is equal to the number of output IF units 102,
The field lengths of the input IF number and the output IF number are the same, and the conversion from the in-apparatus VPI (input side) to the in-apparatus VPI (output side) is performed for the fields without excess or shortage.

Second, the output VPI degeneration code specified on the in-apparatus VPI (input side) is incorporated into the in-apparatus VPI (output side) and notified to the output IF unit 103. For this reason, as shown in FIG. 3, a field of an output VPI degeneration code is defined also in the device VPI (output side). In this output VPI degeneration code field, information written in the output VPI degeneration code field of the in-device VPI (input side) is copied as it is.

As described above, in the present embodiment, the ATM
The VPI of the cell is replaced. If there is a free band that can be used for notification of the VPI in the device accompanying the main signal (for example, if there is an overhead added to each ATM cell in the device), The vacant band may be used. However, in this case, as the VP cross-connect unit, a special device that operates based on the information set in the vacant band is required instead of a simple fixed cross-connect for PVP.

Next, the AT in the connectionless node
The replacement of the VCI of the M cell will be described.

The VCI included in the ATM cell input to the input IF unit 101 is converted by the VCI selector
Replaced with CI. The VCI in the device is such that the cell passes through the cross-connect unit 102 and the VCI of the output IF unit 103
It is used until it reaches the selector section 136, and is replaced with a new output VCI by the VCI selector 136.

The in-device VCI is introduced in the output IF unit 103 to identify user packets that can simultaneously arrive from a single input IF unit 101. That is,
In the output IF unit 103, referring to the input IF number of the VPI (output side) in the apparatus, a plurality of different input IF units 101
Can be identified. However, a plurality of user packets being simultaneously received by a single input IF unit 101 may have different input VPIs but have the same input VCI. Here, the VPI area of the ATM cell is used as the in-device VPI in the connectionless node 152 for transferring routing information as described above. Therefore, the output I
In the F section 103, it becomes necessary to identify a user packet using only the remaining VCI. Therefore, the input IF unit 101 to the VP cross connect unit 102
When the cell is transferred to the device, the input VPI and the input VCI are made to correspond to the in-device VCI, and the output IF unit 103
Input IF unit 1 that differs depending on the input IF number of I (output side)
01 from the same input IF unit 1
The packet from 01 is identified by the device VCI.

Here, a problem arises as to how many in-device VCIs need to be defined. Input VPI and input VCI
Is associated with the in-apparatus VCI, which is information degeneration. Therefore, the input VCI and the input MID (Messag
As in the case where the e Identifier is degenerated to the SMID, a problem arises as to whether or not it is possible to cope with the case where the maximum number of user packets arrive at the same time. This problem is solved as follows.

In the input IF unit 101, the required number of in-device VCIs is the maximum number of user packets that can simultaneously arrive at the input IF unit 101. In the connectionless network assumed in the present embodiment, the maximum number of user packets arriving at each connectionless node is equal to the number of all edge devices. This will be described with reference to FIG.

In FIG. 4, connectionless node C
Estimate the number of packets being transferred simultaneously on the link between D. Considering the number of connections exiting from a certain edge device O and passing through the above link, the maximum number is the total number M of edges existing in the connectionless network. However, the operation of the connectionless network is based on the premise that the user LAN side of the edge device is input / output in packet units, and the connectionless node 15
The routing between the two is static and results in the routing of the smallest tree path based on some link cost. In this case, all connections passing through the link (between the connectionless nodes C and D) starting from the edge device O follow the same route to the connectionless node C. Also, all data from the edge device O, which is the starting point on the route, is in packet units.
Therefore, when observed at the output point of the connectionless node C, which is the starting point of the link, no matter how many connections originating from the edge device O exist, the edge device O
The number of packets being transferred starting from is always one. Since the same applies to all other edge devices, the maximum number of packets being simultaneously received at the input point of the connectionless node D which is the end point of the link is the number of all edge devices. According to the same logic, it can be seen that the number of packets that can simultaneously arrive at any point in any device constituting the connectionless network can be limited to the number of all edge devices. Therefore, the number of VCIs in the device may be prepared for all edge devices. Here, it is assumed that the VCI field is 16 bits, so if all are used, it can be applied to a connectionless network having 64000 edge devices. In order to cope with a larger scale, it is necessary to set the field of the number of VCIs in the device to 17 bits or more, and use an empty band other than the VCI field of the ATM header (overhead added to each ATM cell in the device). There is a need to.

Next, the operation of cell transfer in a connectionless node will be described.

First, the operation of the input IF unit 101 will be described with reference to FIG. ATM input to input IF unit 101
The cell is input to the VCI selector unit 116 to change the VCI, and further input to the VPI selector to change the VPI, and the VP cross-connect unit 10
2 is output. This is as described above. In order to perform such replacement of VPI and VCI, input IF
Each unit in the unit 101 performs the following operation.

The BOM detector 112 has a management table 501 inside. In the management table 501, FIG.
As shown in (1), receivable VPI / VCIs are registered in advance, and a reception state is set for each VPI / VCI.

The BOM detector 112 receives the input ATM.
The VPI / VCI included in the header of the cell is observed, and the reception state is confirmed in the management table 501. If the reception state corresponding to the VPI / VCI of the received cell is “not received”, a new user packet is transmitted (BO
M is received), and the receiving state of the management table 501 is changed to “receiving”. If the cell subsequently received is the same as the previous VPI / VCI, the reception state of the management table 501 is "receiving", and it can be determined that the received cell is COM or EOM. As described above, in the present embodiment, the reception of the BOM is determined using the management table, so that even in AAL5 in which the identification of the BOM / COM cell is not explicitly indicated, the BOM is determined.
The OM can be identified.

When the BOM detection unit 112 detects BOM reception, it outputs a BOM reception notification 510 to the routing table 113 and the cache table 114.

The EOM detector 111 determines that the received cell is EOM.
Is determined. When using AAL5, EOM
Only in case of PTI (Payload Type Identif
The bit of the ier) field is set to “1”. Therefore, the reception of the EOM can be detected by referring to only the corresponding bit of the PTI field.

When the EOM detection unit 111 detects an EOM, it sends an EOM detection notification 520 to the BOM detection unit 112.
And to the cache table 114.

Since the detection of the EOM indicates the end of the reception of the user packet, the BOM detection unit 112 changes the reception state of the corresponding VPI / VCI in the management table 501 to “not received”.

As described above, by the operations of the BOM detection unit 112 and the EOM detection unit 111, the BOM, COM, and EOM cell identification of each packet can always be determined using AAL5. Note that the BOM detection unit 112
FIG. 7 shows the above operation.

As shown in FIG. 8, the routing table 113 uses the destination connectionless address as an address entry, an output IF number indicating the output IF unit 103 to which a cell is to be transferred, and an output VPI to be replaced with a cell.
Is registered. The routing table 113 stores the BOM detection unit 11
In response to the BOM detection notification 510 from the BOM 2, a destination connectionless address is detected from the header of the intermediate frame included in the BOM, and a search is performed using the destination connectionless address. The retrieved output IF number and output VPI degeneration code are supplied to the VPI selector 117 and used for VPI replacement. Note that the received BOM is transferred to any output IF unit 103 based on the output IF number and the output VPI degeneration code obtained by the search.
It is possible to know what VPI to replace with the physical link.

The routing table 113 also supplies the retrieved output IF number and output VPI degeneration code to the cache table 114. This is because the same routing as the BOM is performed for the COM and the EOM (constituting the same user packet) following the BOM.

As shown in FIG. 9, the cache table 114 has fields of an output IF number, an output VPI degeneration code, an in-device VCI, and a reception state in correspondence with the VPI / VCI of an input cell. Here, the field of the reception state indicates whether the information registered in the cache table is valid.

When the cache table 114 receives the BOM detection notification 510 from the BOM detection unit 112, the cache table 114 searches for a row whose reception status is "not received", and
The VPI / VCI is detected from the OM, the routing information (output IF number, output VPI degeneration code) 530 from the routing table 113 is received, and the VCI in the device is received from the VCI pool 115 in the device. This information is retained. at the same time,
Change the receiving status of that row to "receiving".

Thereafter, the VPI / VCI of the received cell is registered in the cache table 114, and if “receiving”, the COM or E following the previously received BOM is registered.
Since it is OM, the output IF number and the output VPI degeneration code corresponding to the VPI / VCI of the received cell are output to the VPI selector 117, and the in-device VCI is output to the VCI selector 116.

The cache table 114 stores the EO
When EOM reception notification 520 is received from M detection section 111, it is determined that the reception of the packet of the corresponding VPI / VCI has been completed, and the reception state of the corresponding row is changed to “not received”.

Here, the operation of operating the cache table 114 needs to be performed for each cell, and high-speed processing is required. When the format shown in FIG. 9 is adopted as the cache table 114, there is a method of speeding up operations such as retrieval by configuring the cache memory itself with a cam (content addressable memory) or the like. Also,
As another configuration example of the cache memory, the input VPI /
Prepare a memory with the input VCI as the address, and
The CI, the output IF number, the output VPI degeneration code, and the reception state may be held as data. In this case, the search can be performed by one access using the input VPI / input VCI as an address entry. In addition, since only a few VPs are defined per physical link as a premise of the connectionless communication method, the amount of memory can be reduced by defining the input VPI of the above table as a degenerate code of several bits instead of 12 bits. is there.

As described above, the in-device VCI pool 115 is connected from the input IF unit 101 to the VP cross-connect unit 10.
VCI assigned to each user packet output to 2
Is managing. For example, 64000 in-device VCIs
Is prepared, a 64000-length FIFO (first in
first out) memory is prepared and VC is set in the initial state.
FI = VCI in the device with I = 000 to VCI = 64000
Hold in FO. Every time the BOM passes, the internal VCI from the top of the FIFO in the internal VCI pool 115
Is stored in the cache table 114 as in-device VCI information corresponding to the VPI / VCI of the BOM cell. Thereafter, cells having the same VPI / VCI as the BOM are changed to the in-device VCI held in the cache table 114 by the VCI selector 116 until the EOM arrives. When passing through the EOM, the corresponding VCI in the device is
From the cache table 114, the in-device VCI pool 11
By returning to 5, it is possible to always cope with 64000 user packets.

As described above, in the input IF unit 101, the in-apparatus VPI (input side) and the in-apparatus VCI are given to the selector units 117 and 116, respectively, and each selector unit performs replacement.

Next, the operation of the VP cross connect unit 102 will be described with reference to FIG.

The ATM cell transferred to the VP cross-connect unit 102 is input to the cross-connect control unit 121 provided for each input IF unit 101. In the cross connect control portion 121, the VPI conversion section 124 converts the internal VPI (input side) into the internal VPI (output side), and outputs the converted VPI to the output IF section 103 from the N × N cross connect section 122.

To perform the above operation, the PVP switching table 123 detects the in-device VPI (input side) of the ATM cell. Switching table 1 for PVP
Reference numeral 23 has a format shown in FIG. 11, searches for the VPI (input side) in the device as an address, and sends routing information (output IF number) of the cell to be transferred to the N × N cross-connect unit 122. The VPI that is output and replaced (output VPI) is output to the VPI conversion unit 124. Here, the routing information (output IF number)
The value of the field of the output IF number of the VPI (IN side) in the device is output as it is. Output VPI is VPI in the device
(OUT side), the input IF number that is fixedly connected to the output VPI degeneration code in the in-device VPI (IN side) is output.

The switching table 123 is characterized in that output data (output IF number, output VPI) is definitely determined by the input VPI and the input IF number to which the cross-connect control section 102 is fixedly connected. Is to be done. Therefore, the contents of the PVP switching tables 123 of all the cross-connect control units 121 can be prepared as fixed tables, and the load on the operation of the network operator can be reduced.

The N × N cross-connect unit 122 transfers the ATM cell to a predetermined output IF unit 103 based on the routing information (output IF number) output from the switching table of the cross-connect control unit 121.

As described above, the VP cross-connect unit 102 performs the switching of the VP cross-connect unit and the VPI conversion using only the information of the routing table 113 in the input IF unit 101.

Next, referring to FIG. 12, output IF section 10
Operation 3 will be described.

The ATM cells input to the output IF unit 103 are replaced by the VCI selector 136,
The selector 137 changes the VPI and outputs the VPI to the next connectionless node or edge device.

In order to change the VPI and VCI, each unit of the output IF unit 103 operates as follows.

The output IF unit 103 can uniquely specify a user packet based on the input IF number written in the device VPI (output side) of the ATM cell and the device VCI.

The BOM detection unit 132 manages the management table 11
01. This management table 1101 corresponds to FIG.
3 and B of the input IF unit 101.
It operates similarly to the OM detection unit 112. That is, when the BOM detection unit 132 receives the ATM cell,
In 01, when the reception state corresponding to the input IF number of the reception cell / in-device VCI is "not received", it is determined that a new user packet has been transmitted from a certain input IF unit 101, and it is determined that the BOM has been received. Change the status to "receiving". Thereafter, COMs having the same input IF number / in-device VCI are received, but since they are “receiving” by referring to this table, COM or EOM
Is determined. Then, the BOM detection unit 132
When the BOM is detected, the BOM is stored in the cache table 133.
An M detection notification 1110 is output.

The EOM detection section 131 is also connected to the input IF section 1
01 operates in the same manner as the EOM detection unit 111, and determines whether or not the received cell is an EOM. Then, when the EOM is detected, the EOM detection unit 131 notifies the EOM detection notification 112.
0 to the cache table 133 and the BOM detection unit 132
Output to

[0093] The BOM detection unit 132 outputs the EOM detection notification 1
120, the reception of the packet is completed,
The receiving state of the corresponding input IF number / in-device VCI is changed to “not received”.

The cache table 133 is configured, for example, as shown in FIG. The cache table 133 stores the BOM detection notification 1 from the BOM detection unit 132.
When 110 is received, a line whose reception status is “not received” is searched. Then, the input IF number of the input BOM / internal VCI and the new VCI received from the output VCI pool 134 are stored in that row in association with each other. at the same time,
Change the receiving status of the same line to “receiving”.

Thereafter, the same input IF number / in-device VCI
Are received, since those cells are COM or EOM with the same user packet as the previously input BOM, the corresponding VCI is output to the VCI selector unit 136 with reference to the cache table 133. You.

When the EOM detection notification 1120 is received from the EOM detection unit 131, the cache table 133 determines that the reception of the packet of the corresponding input IF number / in-device VCI has been completed, and changes the reception state in the cache table 133 to “not received”. Change to

The cache table 133 is also required to be high-speed because it performs processing in units of cells, similarly to the cache table 114 of the input IF unit 101. However, as described above, the use of a CAM or the input IF number / device This can be realized by using a memory or the like having the internal VCI as an address entry.

The output VCI pool 134 is connected to the output IF unit 1
The VCI manages a VCI assigned to a new packet unit output from 03 to a physical link. This output VCI pool is configured similarly to the internal VCI pool in the input IF unit 101. That is, when 64000 in-device VCIs are prepared, a 64000-length FIFO memory is prepared, and as an initial state, VCI = 000 to VCI = 640.
The value of 00 is kept in the FIFO. Every time the BOM passes, the available VCI is output from the top of the FIFO of the output VCI pool 134 and stored in the cache table 133 as the output VCI corresponding to the input IF number of the BOM cell / in-device VCI. Thereafter, cells having the same input IF number / in-device VCI as the BOM are stored in the cache table 1 by the VCI selector 136 until the EOM arrives.
The output VCI is replaced with the output VCI held in 33. Also,
At the time of passing through the EOM, the output VCI held in the cache table 133 is returned to the output VCI pool 134.

The VPI decoding unit 135 calculates 12b from the output VPI degeneration code of the in-device VPI (output side) of the ATM cell.
It decodes the VPI of the
I conversion. Output VPI degeneration code and 12-bit VP
The correspondence of I is set in the output IF unit 103 in advance.

[0100]

According to the present invention, the input IF unit and the output IF
And a VP cross-connect unit can constitute a connectionless node. In the configuration of the present invention, the input VPI
A function of a connectionless node that performs switching based on / VCI, an input IF number, and a destination connectionless address can be realized by a VP cross-connect unit having only a PVP cross-connect function. Since the functions of a typical ATM cross-connect and an ATM switch can be used, there is an effect that the device cost is reduced and the installation of a connection network is facilitated.

Also, by introducing the VPI in the device, the input I
Since all transfer processes can be specified only by the information of the routing table in the F section, and as a result, the switching information of the cross-connect section can be prepared as fixed data.
Operation load on the cross-connect part can be reduced.

Further, by introducing an in-device VCI according to the network scale, even if simultaneous transfer of the maximum number of user packets occurs in a connectionless node, cell-based transfer becomes possible without any limitation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a connectionless data communication device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an in-apparatus VPI (input side).

FIG. 3 is a diagram for explaining an in-apparatus VPI (output side).

FIG. 4 is a diagram for explaining a maximum value of the number of simultaneously arrivable packets.

FIG. 5 is a block diagram illustrating details of an input IF unit in FIG. 1;

FIG. 6 is a diagram for explaining a management table of a BOM detection unit in FIG. 5;

FIG. 7 is a diagram for explaining control on the management table in FIG. 6;

FIG. 8 is a diagram illustrating a routing table of an input IF unit in FIG. 5;

FIG. 9 is a diagram for explaining a cache table of the input IF unit in FIG. 5;

FIG. 10 is a block diagram illustrating details of a cross-connect unit in FIG. 1;

FIG. 11 is a diagram for explaining a PVP switching table of the cross-connect control unit in FIG. 10;

FIG. 12 is a block diagram illustrating details of an output IF unit in FIG. 1;

FIG. 13 is a diagram for explaining a management table of the BOM detection unit in FIG.

FIG. 14 is a diagram for explaining the cache table of FIG. 12;

FIG. 15 is a diagram for explaining a conventional connectionless network.

16 is a diagram for explaining conversion of a user packet into an ATM cell in the edge device of FIG. 15;

FIG. 17 is a diagram illustrating a format of an ATM cell.

FIG. 18 is a diagram illustrating the connectionless node in FIG.
FIG. 3 is a diagram for explaining a method of performing VCI assignment in units of packets on a link.

[Explanation of symbols]

 101 Input IF Unit 102 VP Cross Connect Unit 103 Output IF Unit 111 EOM Detector 112 BOM Detector 113 Routing Table 114 Cache Table 115 Internal VCI Pool 116 VCI Selector (SEL) 117 VPI Selector (SEL) 121 Cross connect control unit 122 N × N cross connect unit 123 PVP switching table 124 VPI conversion unit 131 EOM detection unit 132 BOM detection unit 133 Cache table 134 Output VCI pool 135 VPI decoding unit 136 VCI selector unit 137 VPI selector unit 150 Connectionless Network 151 Edge device 152 Connectionless node 153 Address resolution server (ARS) 154 User LAN

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-46625 (JP, A) JP-A-6-85830 (JP, A) JP-A-6-62038 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H04L 12/28

Claims (11)

(57) [Claims] In a connectionless communication device used in a connectionless network, a plurality of input IF units, a plurality of output IF units, and a connection between the plurality of input IF units and the plurality of output IF units. Each of the plurality of input IF units detects a destination connection address included in an input ATM cell, and outputs an output IF unit and an output VP corresponding to the destination connection address.
The VPI in the first device including the information indicating
The VCI area of the cell is defined, and the in-device VCI is defined in the VCI area of the ATM cell, and the ATM cell is output to the VP cross-connect section. In the VPI area, a second device VPI including information indicating an input IF unit that has output the ATM cell and information indicating the output VPI is defined in place of the first device VPI, and the first device VPI is defined. Outputting the ATM cell to an output IF unit specified by the in-device VPI, wherein each of the plurality of output IF units includes an output included in the second in-device VPI in a VPI area of the input ATM cell. An output VPI is defined based on the information indicating the VPI,
In the VCI area, an output VCI instead of the in-device VCI
A connectionless communication device characterized by defining and outputting to the outside. 2. A series of ATM cells constituting one packet by each of the plurality of input IF units detecting an input VPI and an input VCI from the VPI area and the VCI area of an input ATM cell. 2. The connectionless communication device according to claim 1, wherein the same first device-internal VPI and device-internal VCI are defined for the communication device. 3. The VP cross-connect unit includes a VP switch that performs switching based on an input IF unit that outputs an input ATM cell and a first in-device VPI included in the ATM cell. The connectionless communication device according to claim 1 or 2, wherein: 4. A connector overlaid on an ATM network.
To configure the Yonresu network, in Konekushi <br/> Yonresu communication device for use with the edge device and the address resolution servers connected to each other, and N input IF section, and N output IF section, between them
Connected to the N input IF sections,
Output to any of the N output IF sections.
A loss connect unit, and the input IF unit is configured such that the ATM cell is BOM
Judge whether or not it is BOM and generate BOM reception notification if it is BOM
BOM detection unit for, the ATM cell is either a EOM not
An EOM detection unit that generates an EOM reception notification if the EOM is an EOM, and a destination connector included in the ATM cell.
Output number and output VP corresponding to the applicationless address
Routing table for outputting I-retraction code , inside the device
In-device VCI pool for managing VCI , the ATM cell
VCI and VCI included in the BOM reception notification,
EOM reception notification, output IF number, output VPI
Receiving the retraction code and the in-device VCI,
VCI, the output IF number, and the output VPI regression code.
Cache table that outputs the data and the ATM cell
The output IF number and the output VPI
V to be replaced with VPI in the input device based on the retraction code
PI selector and VCI included in the ATM cell
And a VCI selector unit that replaces the VCI with the in- device VCI. The VP cross-connect unit
The VPI in the input device included in the TM cell is output to the output device.
And converts the input-side device VP
Cross-connect control section for outputting an output IF number corresponding to I, and on the basis of the output IF number, the ATM cell
Is composed of N × N cross-connect unit for outputting Le to the corresponding output IF section, the output IF section, respectively, the VP cross-connects
It is determined that the ATM cell from the section is a BOM or not and is a BOM.
A BOM detection unit that outputs a BOM reception notification in the case
Determine whether the TM cell is EOM and if it is EOM
EOM detection unit that outputs EOM reception notification , output VCI
Output VCI pool to be managed , output side device of the ATM cell
Local VPI and local VCI, the BOM reception notification,
Receiving the fine the EOM received notification, key <br/> catcher Tsu shoe table for outputting an output VCI, device V included in the ATM cell Le
A VCI selector unit for replacing CI with the output VCI ,
Output from VPI in the output side device included in the ATM cell
VPI decoding unit for decoding VPI , output of the ATM cell
VPI cell that replaces the VPI in the external device with the output VPI
It is composed of selector unit, in the interior of the connectionless communication device, A input
The in-device VPI is defined in the VPI area of the TM cell,
× N with reference to only the input IF number and VPI of the ATM cell to the cross connect unit with using a VP switch for switching, to define the device VCI to VCI area of said ATM cell, cell-based in the output IF section A connectionless communication apparatus characterized in that user packet units can be identified in the processing of (1). 5. The connectionless communication device according to claim 4, wherein the BOM detection unit of the input IF unit has a management table for managing reception of a user packet. 6. The connectionless communication apparatus according to claim 4, wherein the cross-connect control unit includes a PVP switching table and a VPI conversion unit. 7. The connectionless communication device according to claim 4, wherein the BOM detection unit of the output IF unit has a management table for managing reception of a user packet. 8. The input IF as the in-device VPI
A first in-device VPI composed of an output IF number and an output VPI degeneration code, which are routing information indicated in the routing table of the unit, and an input to which the output VPI degeneration code and the cross-connect control unit are fixedly connected. V in the second device composed of the input IF number of the IF unit
The VPI of an ATM cell input to the connectionless communication device is converted into the first device VPI by a VPI selector of the input IF unit, and the first device VPI is defined. Is converted into the second in-device VPI by the VPI conversion unit of the cross-connect control unit of the VP cross-connect unit,
The output VPI degeneration code included in the PI is the output IPI
5. The connectionless communication according to claim 4, wherein the output VPI is decoded by a VPI decoding unit of an F unit, and the output VPI is rewritten by the VPI selector unit of the output IF unit. apparatus. 9. The cross-connect control unit according to the output IF number included in the first in-device VPI.
× N The switching control of the cross connect unit is performed, the information of the PVP switching table in the cross connect control unit is preset as fixed data, and the cell transfer in the connectionless communication apparatus is performed by the input IF.
9. The connectionless communication device according to claim 8, wherein the connectionless communication device is integrally controlled by only a routing table of the unit. 10. The VCI of an ATM cell input to the connectionless communication device is converted into the in-device VCI by a VCI selector of the input IF, and the output IF is defined by the second in-device VPI. Each input IF is determined by the input IF number
9. The connectionless communication apparatus according to claim 8, wherein a user packet transferred simultaneously from a unit can be identified, and the in-device VCI is rewritten to an output VCI by a VCI selector unit of the output IF unit. 11. The in-device VCI is a VPI and VCI of an ATM cell input to the connectionless node.
In-device VCI assigned and assigned in accordance with
Is defined as the upper limit of the number of all edge devices in the connectionless network, so that the maximum number of user packets can be transferred without restriction even if simultaneous transfer occurs in the connectionless node. The connectionless communication device according to claim 10, wherein: