JP2001230804A - Packet multiplexer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To enable adaptive band allocation so as to optimize an output band, and to enhance a statistical multiplexing effect. Reduce the packet transfer delay time. SOLUTION: The amount of data waiting for transmission (queue length) stored in a plurality of buffers for storing an input packet for each identifier of an output packet is measured, and when judging from which of the plurality of buffers the buffer is to be read, a queue is used. Consider that the length has reached the payload length of the output packet, or that the input packet stored in the buffer is the last packet obtained by dividing one packet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for use in a network in which a packet is stored in another fixed-length frame and transferred.

[0002]

2. Description of the Related Art In a conventional packet multiplexing method involving packet conversion, as shown in FIG. 7, a packet conversion unit from an input packet A to a packet B as an output packet and output control to an output port. , And each is processed independently.

[0003] That is, an input packet is accumulated for each buffer of the identifier of the corresponding output packet, and is converted into an output packet of a fixed-length frame. Depending on the traffic situation of the input packet or the content of the input packet, Output processing such as scheduling to a preferential output port is not performed.

[0004]

When an input packet is stored in an output packet of a fixed length frame having a different length and configuration from that of the input packet and transferred, the effective input packet occupies in the output packet. The ratio (effective packet density) is one of the important factors for determining the multiplicity.

When the conventional technique is used, since the packet conversion process and the scheduling process are performed independently, the buffer has only input packets less than the band (output band) allocated to each output packet identifier. Even in such a case, if the order is read by the scheduling process, a predetermined number of output packets corresponding to the output band are read. That is, the read out predetermined number of output packets includes a lot of invalid empty bands, resulting in a decrease in effective packet density and a decrease in line use efficiency of output ports.

[0006] Alternatively, when one packet is divided into a plurality of input packets and transferred, the order in which the last packet of the one packet is read out by the scheduling process is rotated even though the last packet has arrived in the buffer. If not, the waiting time results in an increase in the transfer delay time of the one packet.

In particular, when another packet constituting the one packet has already been transmitted, the last one packet is delayed, so that the entire one packet is discarded outside the allowable delay time. It can happen.

The present invention has been made in view of such a background. By converting an input packet into an output packet in accordance with the traffic situation of the input packet and the content of the stored information, the output bandwidth is reduced. It is an object of the present invention to provide a packet multiplexing apparatus which enables adaptive band allocation so as to be optimal and enhances a statistical multiplexing effect. Another object of the present invention is to provide a packet multiplexing apparatus that can reduce the packet transfer delay time.

[0009]

SUMMARY OF THE INVENTION A packet multiplexing apparatus of the present invention measures the amount of queued data (queue length) stored in a plurality of buffers for storing input packets for each output packet identifier. When judging from which buffer of a plurality of buffers to read, the queue length must reach the payload length of the output packet, or
It is characterized in that the input packet stored in the buffer is the last packet obtained by dividing one packet.

That is, by adding that the queue length has reached the payload length of the output packet in addition to the transmission conditions of the conventional scheduler, the output packet can always be filled with valid data and transmitted.
In this way, transmission of inefficient output packets having a low effective packet density is suppressed, and only efficient output packets having a high effective packet density are transmitted, whereby effective use of bandwidth can be achieved.

When an input packet is provided with an identifier indicating the end of one packet, if the transmission condition by the conventional scheduler and the transmission condition by the queue length are limited, the queue length becomes equal to the payload length of the output packet. Until the final packet stored in the buffer is not sent out, and the transfer delay time as the one packet may increase.
An input packet to which an identifier indicating the end of the one packet has been added needs to be converted into an output packet and transmitted even if the effective packet density decreases.

[0012] Therefore, the present invention provides a method for the final packet of a plurality of input packets constituting one packet.
It is characterized in that it is converted into an output packet and transmitted without applying the condition of the queue length. According to the present invention, the transfer delay time of the one packet can be reduced.

That is, the present invention provides a packet multiplexing device comprising a plurality of input ports and one output port, and a means for multiplexing an input packet arriving at the input port into an output packet having a fixed packet length. Device.

Here, a feature of the present invention is that a buffer is provided for each packet identifier of an output packet,
Means for distributing and storing input packets in the buffer according to the identifier; means for measuring the data amount of the input packets stored in the buffer; and the data amount of the stored input packets corresponding to the packet length of the output packets. Means for preferentially multiplexing input packets in the buffer which has reached the threshold value and outputting them as output packets.

Further, when one packet is divided into a plurality of input packets and transferred, regarding the buffer in which the last packet of the one packet has arrived, the buffer in the buffer in which the packet has arrived regardless of the threshold value It is desirable to have means for preferentially multiplexing input packets and outputting them as output packets.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a packet multiplexing apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a main part of a packet multiplexer according to a first embodiment of the present invention. FIG. 4 is a block diagram of a main part of a packet multiplexer according to a second embodiment of the present invention.

According to the present invention, a plurality of input ports I _{1 to} I _1
n and one output port O, and the input port I
Control unit B14 as a means for the input packets arriving ₁ ~I _n is the length of the packet multiplexed into the output packet of the fixed
Is a packet multiplexing device including

Here, the feature of the present invention is shown in FIG.
As shown in FIG.
Buffa B15₁~ B15_nIs provided, and the buffer B
Fifteen ₁~ B15_nInput packet according to the identifier
VPI / VCI identification as a means to sort and accumulate data
Part B11 and buffer B15₁~ B15_nAccumulated in
Queue as a means to measure the amount of data in incoming packets
The information management unit B12 includes a long reading unit B13.
The amount of data of the input packet
Buffer B15 that has reached the threshold value corresponding to the length_i(I is 1 to
n), the transmission right is given, and the control unit B14
Is the buffer B15 to which the transmission right is given._iInput in
Packets are multiplexed with priority and output as output packets
There.

When one packet is divided into a plurality of input packets and transferred, the EOP shown in FIG.
The identification unit B22 detects the arrival of the last packet of the one packet, and for the buffer B15 _j (j is any one of 1 to n) in which the last packet has arrived, the information management unit B12 sends the information to the control unit B14. against, certain incoming packets arriving buffer B15 the _j of the packet regardless of the threshold value at which an instruction to output as preferentially multiplexed output packets.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation of the present embodiment when a packet arrives. FIG. 3 is a flowchart showing the operation at the time of transmitting a packet according to the present embodiment. In this embodiment, the input packet to the packet multiplexer is an ATM cell, and the output packet is MPEG2-
TS packet (payload length = 184 bytes)
An example in which a function of controlling an output packet according to the traffic of an input packet is incorporated in an eficit Round Robin scheduling method (DRR method) will be described.

In the DRR method, the order of queues to be processed is managed by a scheduling list, and it is determined whether the queue at the head of the list can be transmitted. If the queue is transmittable, a packet is transmitted from the queue. If the packet remains in the corresponding queue, it is registered again at the end of the scheduling list.

In FIG. 1, a VPI / VCI identification unit B1
1, identifying the VPI / VCI of the arriving ATM cells, stores remain ATM cells to the appropriate buffer B15 ₁ ~B15 _n. Buffer B15 ₁ ~B15 _n is MPEG2
-Identifier PID (Packet Identificatio) of TS packet
n) is prepared for each, when packing the ATM cells are buffered in MPEG2-TS packets is performed from the same buffer B15 ₁ ~B15 _n.

In the packet multiplexing method according to the present embodiment, the queue length reading unit B13 detects the arrival of the ATM cell or the MPE.
When the queue length changes due to transmission of the G2-TS packet, the queue length in the corresponding buffer is checked. When the ATM cell arrives, the information management unit B12 registers it at the end of the scheduling list. The queue length in the buffer registered at the top of the scheduling list is MPE
When the G2-TS packet length has been reached, a transmission right is given. Control unit B14 controls the transmission from the buffer B15 _i given a transmission right in the information management unit.

In this embodiment, the functions of the present invention have been described based on the DRR method. However, similar effects can be obtained by incorporating the functions of the present invention in other scheduling methods.

Next, the operation of the first embodiment of the present invention will be described in more detail with respect to (initialization) (packet input) (packet output).

(Initialization) As parameters for each buffer, Q [i] indicating a queue length and DC [i] indicating a transmittable amount when a transmission right in the DRR method is given are prepared. Initialize (clear to 0).

(Packet Input) The operation when a packet arrives will be described with reference to FIG. When an ATM cell arrives (F101), the ATM cell length (53 bytes) is added to Q [i] indicating the queue length of the buffer of the corresponding PID [i] (F102). Next, if the PID [i] group is not already registered in the scheduling list (F103), it is registered at the end of the scheduling list and the DC [i] value is cleared to 0 (F10).
4). ATM arriving at the last corresponding buffer [i]
The cell is stored (F105). Also, the PID [i]
If the group is already registered in the scheduling list, the arriving ATM cell is stored in the buffer [i].

(Packet Output) The operation at the time of packet transmission will be described with reference to FIG. The buffer information of the PID [i] group listed at the head of the scheduling list is read (F202), and the queue length [i] of the PID [i] group reaches the payload length (184 bytes) of MPEG2-TS. When you are (F203),
The user-specific weight value [i] proportional to the guaranteed bandwidth is D
The value is added to the C [i] value (F204). And DC [i]
It is determined whether the packet can be transmitted based on the value (F20).
5), 1 MPEG from buffer [i] approved to be sent
2- Send a TS packet (F206). DC [i]
If the transmission is not permitted by the value, it is registered again at the end of the scheduling list (F208), and the same processing is performed for the next registered PID [i] group.

When the queue length [i] does not reach the MPEG2-TS packet length, the user-specific weight is added to the DC [i] value only when the DC [i] value does not reach the queue length [i]. The value [i] is added (F210). Then, it is registered again at the end of the scheduling list (F20
8).

After transmission, the queue length [i] and DC
[I] 184 which is the MPEG2-TS packet length from the value
(F207), it is confirmed whether or not the buffer [i] of the PID [i] group becomes empty due to the transmission of the data of one MPEG2-TS packet. When the buffer [i] is empty, the registration is deleted from the scheduling list.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a flowchart showing the operation of the present embodiment when a packet arrives. FIG. 6 is a flowchart showing the operation at the time of transmitting a packet according to the present embodiment. In this embodiment, the input packet to the packet multiplexer is an ATM cell, and the output packet is MPEG2-
A TS packet, which has a function of controlling an output packet according to the traffic of the input packet and a function of controlling the output packet according to whether or not the input packet is the last packet according to the Definit Round Robin scheduling method (DRR method). Shows the case where it is incorporated. In the DRR method, the order of queues to be processed is managed by a scheduling list, a determination is made as to whether the queue at the head of the list can be transmitted, and if transmission is possible, a packet is transmitted from the queue and the queue is transmitted. If a packet remains in the scheduling list, it is registered again at the end of the scheduling list.

In FIG. 4, a VPI / VCI identification unit B1 is provided.
1, identifying the VPI / VCI of the arriving ATM cells, stores remain ATM cells to the appropriate buffer _B15 1 _{~B15 n.} The EOP identification unit B22 sends the arriving AT
If the M cell is an EOP cell by identifying whether it is an EOP cell or not, the fact that the last buffer (EOP cell) is included in the corresponding buffer is recorded. Buffer B15 ₁
~ B15 _n is the identifier PID of the MPEG2-TS packet
Prepared in the (Packet for the Identification) each, when packing the ATM cells are buffered in MPEG2-TS packets is performed from the same buffer _B15 1 _{~B15 n.}

In the packet multiplexing method according to the present embodiment, the queue length reading unit B13 detects the arrival of an ATM cell or the MPE.
When the queue length changes due to transmission of the G2-TS packet, the queue length in the corresponding buffer is checked. When the ATM cell arrives, the information management unit B12 registers it at the end of the scheduling list. The queue length in the buffer registered at the top of the scheduling list is MPE
A transmission right is given when the G2-TS packet length is satisfied. Even when such a condition is not satisfied, a transmission right is given when an EOP cell is included in the buffer.
Control unit B14 controls the transmission from the buffer B15 _i given a transmission right in the information management unit B12.

In this embodiment, the functions of the present invention have been described based on the DRR method. However, similar effects can be obtained by incorporating the functions of the present invention in other scheduling methods.

Next, the operation of the second embodiment of the present invention will be described in more detail with respect to (initialization) (packet input) (packet output).

(Initialization) As parameters for each buffer, Q [i] indicating the queue length in bytes and D indicating the transmittable amount when the transmission right in the DRR method is given.
C [i] is prepared, and each is initialized (cleared to 0).

(Packet Input) The operation when a packet arrives will be described with reference to FIG. When the ATM cell arrives (F301), the buffer [i] of the corresponding PID [i]
The ATM cell length (53 bytes) is added to Q [i] indicating the queue length of (F302). At this time, the ATM that arrived
If a new MPEG2-TS packet is generated by the cell (F303), the EOP identification flag [i] is lowered (F304).

Next, if the PID [i] group is not registered in the scheduling list (F30
5) At the same time as registering at the end of the scheduling list, the DC [i] value is cleared to 0 (F306). If the arrived ATM cell is an EOP cell (F307),
The EOP identification flag [i] is set (F308). Finally, the ATM cell arriving at the corresponding buffer [i] is stored (F309).

(Packet Output) The operation at the time of packet transmission will be described with reference to FIG. The buffer information of the PID [i] group at the head of the scheduling list is read (F402), and the queue length [i] of the PID [i] group has reached the payload length (184 bytes) of MPEG2-TS (F403). ) Or when the EOP identification flag [i] is set (F404), the user-specific weight value [i] proportional to the guaranteed bandwidth is set to DC.
[I] is added to the value (F405).

Next, it is determined whether the packet can be transmitted based on the DC [i] value (F406), and a 1 MPEG2-TS packet is transmitted from the buffer [i] whose transmission has been recognized (F407). If the transmission is not permitted due to the DC [i] value, it is registered again at the end of the scheduling list (F409), and the same processing is performed for the PID [i] group listed next to the scheduling list.

When the queue length [i] does not reach the MPEG2-TS packet length and the queue [i] does not include an EOP cell, the DC [i] value does not reach the queue length [i]. Only in this case, the user-specific weight value [i] is added to the DC [i] value (F411). Then, it is registered again at the end of the scheduling list (F409).

After transmission, the queue length [i] and DC
[I] 184 which is the MPEG2-TS packet length from the value
(F408), and confirms whether the buffer [i] of the PID [i] group becomes empty due to the transmission of the data of one MPEG2-TS packet. When the buffer [i] is empty, the registration is deleted from the scheduling list.

[0043]

As described above, according to the present invention,
By converting an input packet into an output packet in accordance with the traffic situation of the input packet and the content of the stored information, it is possible to allocate an adaptive band so that the output band is optimized, and to enhance the statistical multiplexing effect. Can be. Further, the packet transfer delay time can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a packet multiplexer according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation when a packet arrives according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing an operation at the time of outputting a packet according to the first embodiment of the present invention.

FIG. 4 is a block diagram of a main part of a packet multiplexer according to a second embodiment of the present invention.

FIG. 5 is a flowchart showing an operation when a packet arrives according to the second embodiment of the present invention.

FIG. 6 is a flowchart showing an operation at the time of outputting a packet according to the second embodiment of the present invention.

FIG. 7 is a block diagram of a main part of a conventional packet multiplexer.

[Explanation of symbols]

B11 VPI / VCI identification unit B12 information management unit B13 queue length reader B14 controller B15 ₁ ~B15 _n buffer B22 EOP identification section I ₁ ~I _n input ports O output port

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayoshi Nakayama 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Tohru Otsu 2-3-1, Otemachi, Chiyoda-ku, Tokyo No. 1 F-term in Nippon Telegraph and Telephone Corporation (reference) 5K030 GA02 HA08 JA01 KA19 KX12 MA14 MB15

Claims (2)

[Claims] 1. A packet multiplexing apparatus comprising: a plurality of input ports; and an output port, wherein the packet multiplexing apparatus includes means for multiplexing an input packet arriving at the input port into an output packet having a fixed packet length. A buffer is provided for each packet identifier of the output packet, means for sorting and storing input packets in the buffer according to the identifier, means for measuring the data amount of input packets stored in the buffer, and stored input packets. Means for preferentially multiplexing input packets in a buffer whose data amount has reached a threshold value corresponding to the packet length of output packets, and outputting the multiplexed packets as output packets. 2. When one packet is divided into a plurality of input packets and transferred, regarding a buffer in which the last packet of the one packet has arrived, regardless of the threshold value, 2. The packet multiplexing apparatus according to claim 1, further comprising means for multiplexing input packets with priority and outputting the multiplexed packets as output packets.