JPH09270823A - Atm router - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a packet abort due to an overflowed system buffer, by allowing an ACK recognition section to detect an ACK signal from a reception host, delaying it by a delay generating section, and transferring the delayed ACK signal to a transmission host. SOLUTION: An ACK recognition section 9 in ATM routers 2, 3 to connect one and other LANs(local area networks) 4, 5 via an ATM(asynchronous transfer mode) network 1 detects an ACK signal from a reception host 7 of the other LAN 5, with respect to transmission data from a transmission host 6 of the one LAN 4 conducting flow control by using the ACK signal. A delay generating section 8 delays the detected ACK signal and sends it to the transmission host 6. The transmission timing of the transmission host 6 is delayed, by allowing the delay generating section 8 to delay the ACK signal as required and transferring the delayed ACK signal to the transmission host 6. An overflowed system buffer memory 10 is avoided, and occurrence of congestion is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM router for connecting local area networks via an ATM network. Local Area Network (Local
ATM (Asynchoronu) between Area Networks (LAN)
s Transfer Mode (Asynchronous Transfer Mode) An ATM router for connecting via a network is known. There is a demand for effective traffic control by this ATM router.

[0002]

2. Description of the Related Art Generally, a router for connecting a plurality of LANs is equipped with a buffer memory for temporarily storing data transferred between LANs, and the storage capacity of this buffer memory is limited. Therefore, one LAN
The buffer memory may overflow when the inflow traffic from the LAN is larger than the output traffic to the other LAN. Due to such overflow of the buffer memory, the data transferred via the router will be discarded.
Either end-to-end throughput will be reduced or data communication will be disrupted.

The standardized CSMA / CD (Car
rier Sense Multiple Acccess / Collision Dete
In the case of a LAN based on the communication method, when the buffer memory of the router approaches the state where it overflows, it is possible to stop the transmission of each terminal connected to the LAN by sending a collision signal from the router. It is possible to prevent the overflow of water. In this case, there is a problem that all terminals connected to the LAN cannot transmit.

As an IP (Internet Protocol) technique, when the buffer memory of the receiving terminal is about to overflow,
ICMP (Internet) that makes a transmission suppression request to the transmitting terminal
A technique is known in which a netControl Message Protocol (netControl) packet is transmitted to avoid overflow of the buffer memory. The function of sending the ICMP packet in this case is implemented in the receiving terminal, and the normal TCP / IP (Trans
mission Control Protocol / Internet Protocol
) It is not implemented in the router that connects LANs.

In addition, ABR (Available) in the ATM network
Standardization of Bit Rate service is in progress. This ABR service is a resource management cell (Resource Management Cell;
RM cell) is used to notify the transmission terminal of the transmission permission rate corresponding to the state of traffic in the ATM network, etc., and the transmission terminal does not exceed the peak cell rate PCR (Peak Cell Rate) declared at the time of connection setting. Then, the cell is transmitted according to the transmission cell rate calculated based on the transmission permission rate. In that case, in the ATM network, the minimum cell rate MCR (M
inimum Cell Rate).

As described above, the AT is connected between a plurality of LANs.
It can be connected via the M network, and in that case, an ATM router is provided between the LAN and the ATM network, for example, the configuration shown in FIG. In the figure, 101 ₁ and 10 ₁₂ are ATM routers, and 102 is an AT.
ATM switch for M network, 103 for terminal, 104 for LA
N and 111 are LAN modules, 112 is an ATM module, 113 is a routing processor, and 114 is a system buffer memory.

The ATM routers 101 ₁ and 10 ₁₂ are LA
LAN module 111 connecting N104 and ATM
The ATM module 112 for connecting the ATM switch 102 of the network, a routing processor 113, and a system buffer memory 114, ATM routers 101 ₂ on the right side shows only LAN module 111 for simplicity.

[0008] ATM router 101 _1, 101 ₂ of the ATM
The module 112 is the terminal 1 connected to the LAN 104.
The packet data (frame data) from 03 is divided into cells, and this user cell is sent to the ATM network. Also, the user cell received via the ATM network is assembled into a packet (frame) and sent to the terminal 103. In this case, ATM routers 101 _1, 101 _2, every time a certain number of transmitted user cells, and sends one RM cell.

This RM cell is, for example, an ATM router 1
When sending from 01 ₁ , as shown by the solid arrow, AT
It is returned at the M router 101 ₂ , and in this case, for example, the RM sent from the ATM router 101 _1.
The cell is called a forward direction RM cell (F-RM cell), and the AT
The RM cell folded in M-Router 101 ₂ are those referred to as backward RM cell (B-RM cell). Also, the ATM switch 102 uses the user cell to send an AT message when congestion occurs.
When notified to the M router 101 ₂ , the ATM router 101 ₂
Notifies the congestion to the ATM switch 101 ₁ using the B-RM cell. Alternatively, in the ATM switch 102, the B-RM cell is used to detect the occurrence of congestion in the ATM router 101.
₁ can be notified.

The aforementioned RM cell has, for example, the format shown in FIG.
The structure including the payload of bytes is the same as that of the user cell. GFC / VPI in this header is user
It is used as a flow control GFC when it is a network interface (UNI), and it is used as part of a virtual path identifier VPI when it is a network node interface (NNI). Therefore, the virtual path identifier VPI is UN
It has an 8-bit configuration for I and a 12-bit configuration for NNI. Further, VCI is a virtual channel identifier having a 16-bit configuration, PT is a payload type having a 3-bit configuration, for example, "000" indicates a user cell without congestion and "1".
10 "indicates an RM cell. CLP indicates a 1-bit cell loss priority indication, and CRC indicates an 8-bit header error control.

In the 48-byte payload of the RM cell, the 1-byte RM PROTOCOL ID is RM.
The protocol identifier or DIR (Direction) is a direction indicating bit, "0" indicates an F-RM cell (forward RM cell), and "1" indicates a B-RM cell (reverse RM cell). In addition, BN (Backward Explicit Congestion Notif)
ication) is a reverse congestion notification bit indicating a B-RM cell generated in the ATM network switch or receiving terminal, CI (Congestion Indecation) is a congestion indication bit, and NI (No Increase) is a cell rate non-cell Increase bit, RA (Request Acknowlege) is ABR
Request acknowledgment bit not used in service,
Further, Res having a 3-bit structure indicates an unused bit.

Also, an ER (Explicit Cell) of 2 bytes
Rate) is the explicitly indicated cell rate, or a 2-byte CCR
(Current Cell Rate) is the current cell rate, 2-byte MCR (Minimum Cell Rate) is the minimum cell rate declared at connection setup, and 4-byte QL (Queue Length) is a queue that is not used in the ABR service. Length, or SN (Sequence Number) consisting of 4 bytes is a sequence number or 30
Byte + 6-bit Res is an unused bit, or 10
A CRC having a bit structure indicates a cyclic code check bit.

In the above-mentioned ABR service, for example,
When the F-RM cell is transmitted from the ATM router 101 _1, the peak cell rate PC declared at the time of call setup is set in the field of the explicit instruction cell rate ER of the F-RM cell.
R is set, the allowable cell rate ACR is set in the field of the current cell rate CCR, and the minimum cell rate MCR is set.
The minimum cell rate MCR is set in the field.

[0014] When the ATM router 101 ₁ receives the B-RM cell, the congestion indication bit CI is, indicates no congestion by CI = "0", and the cell rate no increase bit NI
Indicates that the cell rate can be increased, the peak cell rate PC
Within a range not exceeding R, the cell rate can be increased according to a certain rule. Also, the congestion indication bit CI is C
When congestion is indicated by I = “1”, the cell rate is reduced according to a certain rule within a range not lower than the minimum cell rate MCR. Therefore, the allowable cell rate ACR of ATM router 101 _1, 101 _2, MC
When the ATM switch 102 is changed within the range of R ≦ ACR ≦ PCR and congestion does not occur, the peak cell rate P
It can be transmitted at a transmission cell rate near CR.

[0015]

As described above, the LAN
An ATM router for connecting the two via an ATM network can control the transmission cell rate to the ATM network according to the ABR service, but it does not have a configuration for transmitting an ICMP packet. Therefore, there is a problem that the inflow traffic from the LAN side cannot be controlled when the buffer memory overflows.

In this case, in the LAN of the above-mentioned CSMA / CD system or the like, it is possible to suppress the inflow traffic to the router by sending a collision signal, but L
Transmission of all terminals connected to the AN must be stopped, and there is a problem that communication is interrupted in an emergency. An object of the present invention is to control incoming traffic from the LAN side in an ATM router with a simple configuration.

[0017]

An ATM router according to the present invention will be described with reference to FIG. 1. (1) To connect local area networks 4 and 5 on one side and the other side via an ATM network 1. ACK at ATM routers 2 and 3
An ACK recognition unit 9 for detecting an ACK signal from a reception host 7 of the other local area network 5 for transmission data from a transmission host 6 of the one local area network 4 which performs flow control using a signal, and this AC
The delay generation unit 8 delays the ACK signal detected by the K recognition unit 9 and sends it to the transmission host 6. Again 2a
Is a LAN module, 2b is an ATM module, and 10 is a system buffer memory. The ACK signal is delayed by the delay generation unit 8 as necessary and transferred to the transmission host 6, thereby delaying the transmission timing of the transmission host 6. This makes it possible to avoid overflow of the system buffer memory 10 and avoid occurrence of congestion.

(2) A detected by the ACK recognition unit 9
A random number generation unit for controlling the delay generation unit 8 can be provided so as to give different delay times to the ACK signals corresponding to the multiple connections of the TM network. Therefore, ACK signals to a plurality of transmission hosts can be transferred at random, so that it is possible to prevent simultaneous transmission of data from the transmission hosts and avoid overflow of the system buffer memory 10.

(3) A detected by the ACK recognition unit 9
Based on the delay time information of the system header and the header addition unit that adds the system header in which the delay time information of this packet is written to the packet including the CK signal,
A delay generation unit 8 for delaying a packet including a CK signal can be provided.

(4) A detected by the ACK recognition unit 9
Based on the delay time information of the system header and the header addition unit that adds the system header in which the delay time information of this packet is written to the packet including the CK signal,
It is possible to provide a delay generating means for rewriting the packet including the CK signal into the system buffer memory of the FIFO format.

Further, (5) it is possible to provide a delay generation unit 8 configured to delay the ACK signal corresponding to the virtual channel according to the transfer rate corresponding to the virtual channel.

(6) A buffer amount monitor for detecting the amount of storage in the system buffer memory 10, and a delay time of a packet including an ACK signal corresponding to the amount of storage in the system buffer memory 10 by the buffer amount monitor. It is possible to provide the delay generating section 8 for

(7) A delay time calculating section for measuring the round trip time corresponding to the virtual channel and calculating the delay time in the delay generating section based on this round trip time and the acknowledgment timeout time of the transmitting host. Can be provided.

(8) The ACK recognizing unit 9 performs ACK control from the receiving host to the transmitting host, in which the transport layer protocol performs flow control using the ACK signal, and the empty bit of the network layer packet header is used as the ACK bit.
A configuration for detecting an ACK packet that transfers a signal can be provided.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an explanatory view of essential parts of a first embodiment of the present invention, in which 11 is an ATM switch, and 12 and 1.
3 is an ATM router, 14 and 15 are local area networks (LAN), 16 is a sending host, 17 is a receiving host, 20 and 30 are ATM modules, 21 and 31 are LA.
N modules, 22 and 32 are routing processors,
23 and 33 are system buffer memories, 24 and 34 are cell transmission units, 25 and 35 are cell reception units, 26 and 36 are transmission rate management units, 27 and 37 are frame transfer units, 28 is a delay generation unit, and 29 is an ACK. It is a recognition unit.

The ATM switch 11 corresponds to the ATM network 1 of FIG. 1, the ATM routers 12 and 13 correspond to the ATM routers 1 and 2 of FIG. 1, and the LANs 14 and 15 correspond to the LANs 4 and 5 of FIG. The sending host 16 and the receiving host 17 correspond to the sending host 6 and the receiving host 7 in FIG.
A larger number of hosts can be connected to 15. The delay generation unit 28 corresponds to the delay generation unit 8 in FIG.
The recognition unit 29 corresponds to the ACK recognition unit of FIG. 1, the LAN modules 21 and 31 correspond to the LAN module 2a of FIG. 1, the ATM modules 20 and 30 correspond to the ATM module 2b of FIG. 1, and the system buffer memory 23. , 33
Corresponds to the system buffer memory 10 of FIG.

In this embodiment, the LANs 14 and 15 are connected via the ATM routers 12 and 13 and the ATM switch 11, and the transmission host 16 connected to the LAN 14 is connected.
From the case where data is transmitted from the LAN to the receiving host 17 connected to the LAN 15, the ATM routers 12 and 13 are ATM modules 20 and 30 mutually connected by an internal bus.
, LAN modules 21, 31, routing processors 22, 32, and system buffer memories 23, 3
3 and the ATM modules 20 and 30 include cell transmission units 24 and 34, cell reception units 25 and 35, transmission rate management units 26 and 36, and frame transfer units 27 and 37. is there.

The delay generating section 28 of the ATM module 20
The ACK recognition unit 29 and the ACK recognition unit 29 are also provided in the ATM module 30, but are not shown for simplification.
The routing processors 22 and 32 control each unit, and also perform control such as transfer of packets between the LAN modules 21 and 31 and the ATM modules 20 and 30 via the system buffer memories 23 and 33. .

The sending host 16 sends data to the receiving host 17 and ACKs the acknowledgment from the receiving host 17.
By identifying the (Acknowledement) signal,
The following data is transmitted, and the window control method in which an ACK signal is transmitted from the receiving host 17 every time one frame of data is received or every plural frames of data is received is applied. Further, the transmission frame from the transmission host 16 to the reception host 17 is received by the LAN module 21 of the ATM router 12 via the LAN 14, the header of the data link layer is removed, and the packet is transmitted to the system buffer memory 23 via the internal bus as a packet. Are transferred and accumulated.

The ATM module 20 of the ATM router 12 on the transmission side takes out a packet addressed to the receiving host 17 from the system buffer memory 23, divides it into cells, adds a header, and sets a virtual connection (VC) according to the set virtual connection (VC). At the set transmission cell rate, the data is sent from the cell transmission unit 24 to the ATM switch 11 of the ATM network. The transmission cell rate in this case is managed by the transmission rate management unit 26 based on the ABR service or the like.

Further, the A on the receiving side is sent through the ATM switch 11.
The cells transferred to the TM router 13 are received by the cell receiving unit 35 of the ATM module 30, assembled into packets, transferred to the system buffer memory 33 via the internal bus, and stored therein. This packet is read from the system buffer memory 33, the frame with the header added is sent from the LAN module 31 to the LAN 15, and the receiving host 17 receives it via the LAN 15.

The receiving host 17 sends an ACK signal as an acknowledgment signal when the frame is normally received until the predetermined data amount is reached. This ACK signal is sent to the LAN module 3 of the ATM router 13.
1, is temporarily stored in the system buffer memory 33, is then read by the ATM module 30 into cells, and is sent from the cell transmission unit 34 of the ATM module 30 to the ATM router 12 via the ATM switch 11.

The ATM router 12 on the transmitting side assembles the cells received by the cell receiving section 25 of the ATM module 20 into packets and transfers them to the system buffer memory 23.
Accumulate once. In that case, the AC of the frame transfer unit 27
The K recognition unit 29 detects whether or not the packet includes an ACK signal from the receiving side. Then, the LAN module 21 sends to the LAN 14 a frame in which a header is added to the packet read from the system buffer memory 23, and the sending host 16 receives this frame.

Since the system buffer memories 23 and 33 temporarily store the transmission / reception packets, the LAN 1
When the inflow traffic from 4, 15 increases, or the inflow traffic from the ATM switch 11 increases, if the state remains as it is, the accumulated amount increases and overflow occurs. When the routing processor 22 or a dedicated storage amount monitoring unit (not shown) detects that the storage amount of the system buffer memory 23 has increased, an ACK signal from the receiving side is detected by the ACK recognition unit 29. In that case, the ACK signal is transferred to the delay generation unit 28.

That is, when the ACK recognizing section 29 detects the ACK signal from the receiving host 17 when the storage amount in the system buffer memory 23 increases, the ACK signal is delayed by the delay generating section 28 to delay the system buffer memory. 23, and stores. Then, since the ACK signal read from the system buffer memory 23 is sent from the LAN module 21 to the LAN 14, the transmission host 16 receives the ACK signal after the delay time by the delay generation unit 28, and receives this ACK signal. Since the next frame is transmitted by doing so, the ATM router 1
It is possible to reduce the inflow traffic to No. 2.

When the amount of storage in the system buffer memory 23 increases, the ATM router 12 transfers to the ATM router 13,
By performing the congestion notification using the RM cell, the transmission rate management unit 36 of the ATM router 13 can perform control for reducing the transmission cell rate.

By the control as described above, overflow of the system buffer memories 23 and 33 can be surely avoided, and control can be performed so that the state of frame discard does not occur. Also, in a plurality of terminals, hosts, etc. connected to the LANs 14 and 15, only the transmitting host that receives the delayed ACK signal only delays the next transmission frame, and sends a collision signal to send a LAN signal. It is possible to effectively control the data transfer between LANs via the ATM network, as compared with the case where all the transmissions are stopped.

FIG. 3 is an explanatory view of the essential parts of the second embodiment of the present invention, in which the same symbols as in FIG.
Reference numerals 14 ₁ , 14 ₂ and 14 ₃ are LANs, 16 _{1 to} 16 ₃ are transmission hosts, 21 _{1 to} 21 ₃ are LAN modules, and 41 is a random number generator. In this embodiment, the ATM router 1
2 shows a case where a plurality of LANs 14 _{1 to} 14 ₃ are connected to another LAN via an ATM network (not shown).

The frames transmitted from the plurality of transmission hosts 16 _{1 to} 16 ₃ are received by the LAN modules 21 _{1 to} 21 ₃ via the respective LANs 14 _{1 to} 14 ₃ ,
The packet from which the frame header of the data link layer has been removed is transferred to the system buffer memory 23 via the internal bus and temporarily stored. The packet read from the system buffer memory 23 is used by the ATM module 2
At 0, the cells are divided and a header is added, and the cells are transmitted from the cell transmission unit 24 by a virtual connection (VC) set corresponding to the transmission hosts 16 _{1 to} 16 ₃ , and the transmission cell rate is the transmission rate management unit. 26.

The ACK signal from the receiving host is converted into cells, transferred, received by the cell receiver 25 of the ATM router 12, assembled into packets and transferred to the system buffer memory 23 via the internal bus. Packets corresponding to the LANs 14 _{1 to} 14 ₃ are read from the system buffer memory 23, headers are added, and the packets are sent from the LAN modules 21 _{1 to} 21 ₃ to the LANs 14 _{1 to} 14 ₃ . Therefore, each of the transmitting hosts 16 _{1 to} 16 ₃ can receive and identify the ACK signal from the respective receiving host and start transmitting the next frame.

At this time, the ACK recognition unit 29 detects whether or not the packet includes the ACK signal, and when the accumulated amount in the system buffer memory 23 increases, the packet including the ACK signal is transferred to the delay generation unit 28. After the set delay time, the data is transferred to the system buffer memory 23 via the internal bus. Therefore, for the sending host, A
The CK signal is delayed and transmitted.

In this case, each transmitting host 16 _{1 to} 16 ₃
In the case where ACK signals corresponding to a plurality of VCs are simultaneously transferred to each other, the respective transmission hosts 16 _{1 to} 16 ₃ simultaneously transmit the next frame, and the accumulated amount in the system buffer memory 23 is further increased. Will increase. Therefore, the random number generation unit 41 generates a random number corresponding to VC (virtual channel), and controls the delay generation unit 28 to give a delay time according to the random number to the ACK signal.

As a result, the ACK signals that arrive at the same time are transferred to the respective transmission hosts 16 _{1 to} 16 ₃ at different times, so that the transmission timing of the next frame also becomes random. Therefore, overflow of the system buffer memory 23 can be avoided. In this case, not only when the accumulated amount in the system buffer memory 23 exceeds the set value, but when the ACK signals corresponding to a plurality of VCs are simultaneously received even when the accumulated amount is less than the set value, the random number generator 41 outputs The delay time of the ACK signal corresponding to VC can be set according to the random number.

In the above embodiment, a plurality of LANs 14 ₁
To -14 _3, if it is the case that each sending host _{161-164 3} are connected, which are connected a plurality of sending host to one of the LAN, simultaneously ACK signal has arrived for each transmit host Can also be applied to.

FIG. 4 is an explanatory view of the main part of the third embodiment of the present invention, in which the same reference numerals as those in FIG. 2 indicate the parts having the same names,
42 is a header addition unit, and 43 is a delay generation unit. In this embodiment, the delay generating section 43 is connected to an internal bus, and a header adding section 42 for adding a system header to a packet in which received cells are assembled is provided. And ACK
When the recognizing unit 29 detects a packet including an ACK signal, the header adding unit 42 adds a system header in which delay time information is set, and the system buffer memory 2
3 is transferred via the internal bus and stored. The delay time in this case can be selected according to the amount of storage in the system buffer memory 23.

This system header has, for example, bit b.
Of the bits 0 to b7, 4 bits b0 to b3 can be used as delay time information representing the delay time as a multiple of the unit time T. For example, the delay time is zero when all are "0", and the delay time is twice the unit time T when b0 to b3 = "0010".
Therefore, the delay time information can be set by the bits b0 to b3 of the system header corresponding to the storage amount of the system buffer memory 23, and the system header can be added to the packet by the header adding unit 42.

Further, the routing processor 22 checks to which port the packet at the head of the queue of the system buffer memory 23 should be transferred next, sends a control signal to the LAN module 21 of the target port to be transferred, and transmits the packet to the system. The data is read from the buffer memory 23 and transferred to the LAN module 21. At this time, the header addition unit 4
Examine the system header added in 2 and, for example, b
When 0 to b3 = “0000”, the multiple is zero, so the delay time obtained by multiplying the unit time T by zero is zero, and the LAN
Transfer directly to module 21. B0 to b3 ≠
In the case of "0000", the magnification of the unit time T is not zero, and therefore, it is transferred to the delay generation unit 43. The delay generation unit 43 calculates the delay time based on a multiple of the unit time set in the system header, and ACKs according to the delay time.
After delaying the signal, LAN module 2 of the target port
Transfer to 1.

Therefore, when the accumulated amount in the system buffer memory 23 increases, the ACK signal can be delayed by the delay generating section 43 and transferred to the transmitting host 16, so that the overflow of the system buffer memory 23 is avoided. You can control. Since the system header in this case is used in the ATM router 12, various formats can be applied.

FIG. 5 is an explanatory view of the essential parts of the fourth embodiment of the present invention, in which the same reference numerals as those in FIG. 4 indicate the parts having the same names.
This embodiment shows a case where an ACK signal is delayed by using the system buffer memory 23, and as described above,
AC that the cell assembled by the cell receiving unit 25 includes the ACK signal from the receiving side in the packet
When it is detected by the K recognizing unit 29, the header adding unit 42 adds the system header in which the delay time information according to the magnification of the unit time T or the like is added, and the frame transfer unit 27 transfers it to the system buffer memory 23 via the internal bus. Transfer and store.

The routing processor 22 checks to which port the packet at the head of the queue of the system buffer memory 23 should be transferred next, sends a control signal to the LAN module 21 of the target port to be transferred, and transfers the packet to the system buffer. It is read from the memory 23 and transferred to the LAN module 21. At this time, the header addition unit 42
The system header added in the above is checked. For example, the system header is b0 to b0 as in the case of the above-described embodiment.
Since the delay time is zero when b3 = "0000",
Transfer to the LAN module 21.

The system header b0 to b3 ≠ “000”
In the case of 0 ", since the delay time is set, the delay time is stored again in the system buffer memory 23. In this case, the time from the writing to the system buffer memory 23 of the FIFO format until the reading is a unit time. Let T be
Reading and writing will be repeated by a multiple of the delay time information. Also, b0 to b3 of the system header
By subtracting the contents of the above and re-accumulating in the system buffer memory 23, it is assumed that the predetermined delay time has elapsed when b0 to b3 of the system header of the next read packet are all “0”. It can be transferred to the LAN module 21.

Therefore, the system buffer memory 23 in this case realizes the function of the delay generation unit for delaying the ACK packet by repeatedly reading and writing in accordance with the delay time information of the system header. The overflow of the system buffer memory 23 can be avoided by setting the delay time according to the accumulated amount of the system buffer memory 23.

FIG. 6 is an explanatory view of the fifth embodiment of the present invention, and the same reference numerals as those in FIG. 2 indicate the parts having the same names. The operation of transmitting data from the transmitting host 16 to the receiving host (not shown) via the LAN 14 and transmitting the next data by receiving the ACK signal from the receiving host is the same as in the above-described respective embodiments.

In this embodiment, the transmission rate management unit 26
From the current transmission rate (ACR) to the delay generation unit 28, and the delay generation unit 28 calculates the delay time based on this transmission rate. For example, when there is no congestion or the like and the transmission rate is high, the delay time is shortened, and conversely, when the transmission rate is low, the delay time is increased.

The delay time resulting from the processing of the delay generator 28 is given to the ACK signal, transferred from the delay generator 28 to the system buffer memory 23 via the internal bus, and accumulated. Therefore, the AC transferred to the sending host 16
Since the K signal is given a delay time corresponding to the transmission rate, it is possible to avoid the overflow of the system buffer memory 23 and the occurrence of congestion.

FIG. 7 is an explanatory view of the essential parts of the sixth embodiment of the present invention, in which the same reference numerals as those in FIG.
Reference numeral 5 is a buffer amount monitoring unit. In this embodiment, the storage amount of the system buffer memory 23 is set to the buffer amount monitoring unit 4
5, and notifies the delay generation unit 28 of the accumulated amount. The delay generator 28 controls the delay time corresponding to the accumulated amount to be given to the packet including the ACK signal.

Therefore, when the storage amount of the system buffer memory 23 increases, the delay generation unit 28 delays the ACK signal by a large amount to delay the data transmission from the transmission host 16 and avoid the overflow of the system buffer memory 23. Can be made. The sending host 16
The operation of transmitting data to the receiving host (not shown) via the LAN 14 and transmitting the next data by receiving the ACK signal from the receiving host is the same as in the above-described respective embodiments.

FIG. 8 is an explanatory view of the seventh embodiment of the present invention, in which the same reference numerals as those in FIG. 2 indicate the same parts, 51 is a delay time calculating section, and 52 and 53 are ACK bit writing sections. .
Although the ATM routers 12 and 13 have the same configuration, the delay generation unit 28, the ACK recognition unit 29, and the delay time calculation unit 51 on the ATM router 13 side are not shown for simplification. ing. Also, the dotted arrow indicates A by RM cell.
Shows the route of BR control, and ATM routers 12, 13 and A
The TM switch 11 is connected by a high-speed transmission line such as an optical transmission line in which a plurality of VCs are set.

The sending host 16 and the receiving host 17 are
The case where communication is performed using TCP / IP is shown. TCP corresponds to a transport layer protocol, IP corresponds to a network layer protocol, and is a lower protocol IP of TCP.
The case where the ACK writing units 52 and 53 are provided in FIG. In addition,
TCP has a header including a transmission port number, a reception port number, a sequence number, an ACK number, etc.
It is possible to notify the sending host 16 of the ACK signal from the.

FIG. 9 shows the format of an IP packet. VERS is a 4-bit version number, HLEN is a 4-bit header length in 32-bit units, and SERVI.
C TYPE is an 8-bit service type,
As shown in (B), the priority PRECE having a 3-bit structure.
DENCE, 1-bit delay display bit D, and 1
It is composed of a throughput indicating bit T having a bit structure, a reliability indicating bit R having a 1-bit structure, and an unused bit UNUSED having a 2-bit structure.

Further, TOTAL LENGTH is a 16-bit total length, INDENTIFICATION is a 16-bit identification value, FLAGS is a 3-bit flag, FRAGMENT OFFSET is a 13-bit fragment offset, and TIME TO LIVE.
Is an 8-bit survival time, PROTOCOL is an 8-bit protocol number, HEADER CHECKS
UM is a 16-bit header checksum, SOUR
CE ADDRESS is a 32-bit sender address, DESTINATION ADDRESS is a 32-bit receiver address, IP OPTION is a variable-length IP option, and PADDING is a variable-length padding. There is. DATA indicates variable length data.

Further, (C) is a 2-bit unused bit U of the service type SERVICE TYPE shown in (B).
1 bit in NUSED is set to ACK bit (ACKbi
When receiving the window size data from the sending host 16, the receiving host 17 sets the ACK bit in the ACK bit writing unit 53 to “1” and sends the data to the sending host 16. An acknowledgment can be sent.

When the ACK packet in which the ACK bit is set to "1" is sent from the receiving host 17 to the LAN 15, the ATM router 13 causes the ATM router 13 to transmit the ATM packet as described above.
The cells are transferred to the ATM router 12 via the switch 11. In the ATM router 12, the cell receiving unit 25 receives, assembles the packet, and transfers it from the frame transfer unit 27 to the system buffer memory 23 via the internal bus. In this case, the ACK recognition unit 29 identifies whether or not the ACK bit of the IP header is "1". If the ACK bit is “1”, it is an ACK packet and is transferred to the delay generation unit 28.

The delay generation unit 28 sets the delay time calculated by the delay time calculation unit 51, delays the ACK packet, and then transfers it from the frame transfer unit 27 to the system buffer memory 23 via the internal bus. . Therefore,
The ACK signal from the reception host 17 is delayed and transferred to the transmission host 16, and the transmission of the next data from the transmission host 16 is delayed, so that overflow of the system buffer memory 23 can be avoided. Further, the ACK recognition unit 29 identifies the ACK bit of the network layer packet header (IP packet header) to determine the ACK.
Since it can be discriminated whether it is a packet or not, the time required for the discrimination processing can be remarkably shortened.

The delay time calculation unit 51 calculates the transmission rate from the transmission rate management unit 26 according to the following equation. D = Dmax × (PCR-ACR) / PCR where Dmax is the maximum delay time, PCR is the peak cell rate, and ACR is the permitted cell rate.

The maximum delay time Dmax is Dmax =
Calculated by RTO'-RTT '. In addition, RTT '
Is the round trip time in ABR control, RT
O ′ is a timeout time calculated each time the round trip time is measured. Therefore, the delay time D can be obtained in time for the timeout of the ACK signal in the transmitting host 6 and according to the permitted cell rate ACR. In this case, if the permitted cell rate ACR is large,
The delay time D is reduced, and when the permitted cell rate ACR decreases near the congestion, the delay time D is increased. Therefore, the system buffer memory 23
It is possible to avoid overflow and congestion.

The amount of storage in the system buffer memory 23 is detected by, for example, the buffer amount monitor 45 in the embodiment shown in FIG. 7, the delay time D is calculated by the following equation, and the delay generator 28 is used. It is also possible to delay the ACK signal. D = Dmax × (C−Cth) / (Cmax−Cth) where C = current storage amount, Cth = threshold start threshold, and Cmax is the storage capacity of the system buffer memory 23. In this case, the threshold value Cth can be set to a plurality of types, and the delay time D corresponding thereto can be obtained. In this case, when the storage amount C increases, the delay time D also increases, the transmission rate from the transmission host 16 can be reduced, and overflow of the system buffer memory 23 can be avoided.

FIG. 10 is an explanatory diagram of the delay generating section according to the embodiment of the present invention, which shows the function of the delay generating section 28 in each of the above-described embodiments.
(B) to (D) show the contents of each unit time T of the queue.
That is, when the ACK recognition unit 29 detects an ACK packet, the ACK packet is transferred to the delay generation unit 28,
The addresses are accumulated in the delay buffer shown in (A), and the addresses aaaa, bbbbb, cccc, dddd, and eeee are stored.
Write e, ffff in the queue. In that case, for example,
In FIG. 8, data is written corresponding to a delay time that is an integral multiple of the unit time T calculated by the delay time calculation unit 51. In the state of (B), the addresses aaa, bbbb,
The delay time of the cccc ACK packet is T, address d
The delay time of the ACK packet of ddd and eeee is 3T,
The case where the delay time of the ACK packet of the address ffff is 4T is shown.

When the unit time T elapses, the state of (C) is entered, the addresses aaa, bbbb, cccc are read in this order, and along with this, the ACK packet is read from the delay buffer and transferred to the system buffer memory. Transferred from the buffer memory to the sending host. Therefore, the ACK packets of the addresses aaa, bbbb, and cccc are transferred to the sending host after a delay of the unit time T. When the unit time T further elapses, the state becomes (D). When the unit time T further elapses, the addresses dddd and eeee are read in order, the ACK packet is read from the delay buffer, and transferred to the system buffer memory. , From this system buffer memory to the sending host. Therefore, the address dd
The ACK packet of dd and eeee is given a delay time of 3T. Similarly, A at address ffff
The CK packet is given a delay time of 4T.

The present invention is not limited to the above-mentioned respective embodiments, but various additions and modifications can be made.
Further, a configuration by combining the respective embodiments is also possible. For example, the storage amount of the system buffer memory 23 and the ATM
It is also possible to control the delay of the ACK packet by calculating the delay time including the permitted cell rate ACR on the network side.

[0071]

As described above, according to the present invention, the ACK
The recognizing unit 9 detects the ACK signal from the receiving host 7, and the delay generating unit 8 delays and transfers the ACK signal to the transmitting host 6. Therefore, from the ATM router to the A on the LAN side.
The transmission rate of the transmission host 6 corresponding to the CK signal can be controlled. Therefore, packet discard due to overflow of the system buffer memory 10 can be avoided. Further, when ACK signals for a plurality of transmission hosts are simultaneously detected by the ACK recognition unit 9, the delay time according to the random number from the random number generation unit is given to each ACK signal, so that the data transmission from the plurality of transmission hosts can be performed. Since the timing can be shifted, overflow of the system buffer memory 10 can be avoided.

Further, by calculating the above-mentioned delay time in accordance with the storage amount of the system buffer memory 10 and the permitted cell rate of the ATM network 1, etc., the optimized delay time can be given to the ACK signal. Therefore, overflow of the system buffer memory 10 can be avoided, and stable operation of the system can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of a main part of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a main part of a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a main part of a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a main part of a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a main part of a fifth embodiment of the present invention.

FIG. 7 is an explanatory view of a main part of a sixth embodiment of the present invention.

FIG. 8 is an explanatory diagram of a seventh embodiment of the present invention.

FIG. 9 is an explanatory diagram of a format of an IP packet.

FIG. 10 is an explanatory diagram of a delay generation unit according to the embodiment of this invention.

FIG. 11 is an explanatory diagram of a conventional ATM router.

FIG. 12 is an explanatory diagram of a format of an RM cell.

[Explanation of symbols]

 1 ATM network 2,3 ATM router 4,5 Local area network 6 Sending host 7 Receiving host 8 Delay generating section 9 ACK recognizing section 10 System buffer memory

Claims (8)

[Claims] 1. An ATM router for connecting between one local area network and the other local area network via an ATM network, wherein an ACK signal is used to perform flow control from a transmitting host of the one local area network. An ACK recognition unit that detects an ACK signal from the reception host of the other local area network for the transmission data, and a delay generation unit that delays the ACK signal detected by the ACK recognition unit and sends the delayed ACK signal to the transmission host. An ATM router characterized by that. 2. The A detected by the ACK recognition unit
2. An ATM router according to claim 1, further comprising a random number generator for controlling the delay generator so as to give different delay times to ACK signals corresponding to a plurality of connections in the TM network. 3. The A detected by the ACK recognition unit
A header adding unit for adding a system header in which delay time information of the packet is written to a packet including a CK signal,
The ACK based on the delay time information of the system header
3. The ATM router according to claim 1, further comprising a delay generation unit that delays a packet including a signal. 4. The A detected by the ACK recognition unit
A header adding unit for adding a system header in which delay time information of the packet is written to a packet including a CK signal,
The ACK based on the delay time information of the system header
3. An ATM router according to claim 1, further comprising delay generating means for rewriting a packet including a signal into a FIFO type system buffer memory. 5. The ACK signal corresponding to a virtual channel,
3. The ATM router according to claim 1, further comprising a delay generation unit configured to delay according to the transfer rate corresponding to the virtual channel. 6. A buffer amount monitoring unit for detecting a storage amount of the system buffer memory, and the AC corresponding to the storage amount of the system buffer memory by the buffer amount monitoring unit.
The AT according to claim 1 or 2, further comprising: a delay generation unit that sets a delay time of a packet including a K signal.
M router. 7. A delay time calculating unit for measuring a round trip time corresponding to a virtual channel, and calculating a delay time in the delay generating unit based on the round trip time and an acknowledgment timeout time of a transmitting host. The ATM router according to claim 1, wherein the ATM router is provided. 8. The ACK recognizing unit performs flow control using an ACK signal as a transport layer protocol,
And AC is used for empty bits in the network layer packet header
2. The ATM router according to claim 1, further comprising a structure for detecting an ACK packet for transmitting an ACK signal from the receiving host to the transmitting host, which has K bits.