JP4191551B2 - Packet relay apparatus and packet relay method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a packet relay apparatus and a packet relay method for relaying packets in a packet communication network.
[0002]
[Prior art]
In a packet communication network, a packet transmitted to a predetermined destination is relayed and transferred by a packet relay device (node) such as a bridge, router, or gateway.
[0003]
Here, the packet relay device temporarily stores packets to be transferred to other packet relay devices or the like in a memory (hereinafter referred to as a buffer), and stores the stored packets based on the FIFO (First-in First-out) principle. Forward.
[0004]
In general, it is desirable that the capacity of the buffer be as large as possible, except for hardware restrictions, in order to prevent packets from being discarded.
[0005]
On the other hand, in voice communication or the like that requires real-time performance, the time during which packet delay can be tolerated (hereinafter referred to as the maximum allowable delay time) is short. Therefore, in order to ensure real-time performance, a smaller buffer capacity is desirable. .
[0006]
Specifically, as shown in FIG. 6A, if the buffer capacity is too large with respect to the maximum allowable delay time, the time that the packet stays in the buffer (hereinafter referred to as stay time) becomes longer. Packets (packet a and packet b) whose retention time exceeds the maximum allowable delay time remain accumulated in the buffer. Here, since the packets (packet a and packet b) whose residence time exceeds the maximum allowable delay time are unnecessary packets, resources (especially radio resources) used when transferring such packets are wasted. turn into.
[0007]
On the other hand, as shown in FIG. 6B, when the capacity of the buffer is too small, a packet (packet e) whose residence time has not reached the maximum allowable delay time is discarded, and communication quality deteriorates. End up.
[0008]
Therefore, the conventional buffer capacity is set to an appropriate level so that packets whose residence time exceeds the maximum allowable delay time will not be transferred, assuming that packets are transferred at a predetermined transfer rate. (For example, Patent Document 1).
[0009]
[Patent Document 1]
JP 2000-307602 A
[Problems to be solved by the invention]
However, since the conventional buffer capacity is set on the assumption that packets are transferred at a predetermined transfer rate, the transfer rate temporarily decreases due to congestion of the packet communication network or occurrence of reception errors. When an overflow occurs in this state, there is a problem that if the transfer rate increases, a packet that can be transferred without exceeding the maximum allowable delay time is discarded.
[0011]
Therefore, the present invention has been made to solve the above-described problem, and the transfer rate at the time of packet transfer temporarily decreased from a predetermined transfer rate due to congestion of the packet communication network or the occurrence of a reception error. In this case, a packet relay apparatus and a packet relay method are provided that can prevent a packet that may be transferred without exceeding the maximum allowable delay time if the transfer rate is increased, from being discarded. That is the purpose.
[0012]
[Means for Solving the Problems]
According to a first aspect of the present invention, a packet relay apparatus that relays a packet in a packet communication network includes a packet storage unit having a predetermined buffer capacity, a transfer rate measurement unit that measures a transfer rate when a packet is transferred, The gist of the present invention is to provide buffer capacity expanding means for expanding the buffer capacity when the transfer rate measured by the transfer rate measuring means is lower than a predetermined transfer rate.
[0013]
According to such a feature, when the transfer rate measured by the transfer rate measuring unit is temporarily lower than a predetermined transfer rate due to occurrence of congestion or reception error of the packet communication network, the buffer capacity expanding unit By enlarging the buffer capacity, the packet relay device can prevent a packet that can be transferred without the maximum delay time from being discarded if the transfer rate increases.
[0014]
The predetermined buffer capacity is set to an appropriate level so that packets whose residence time exceeds the maximum allowable delay time will not be transferred, assuming that packets are transferred at a predetermined transfer rate. It shall be. For example, the predetermined buffer capacity is set based on a product of a predetermined transfer rate and a maximum allowable delay time.
[0015]
A second feature of the present invention is that, in the first feature of the present invention, the packet relay apparatus has a predetermined transfer rate measured by the transfer rate measuring unit in a state where the buffer capacity is expanded by the buffer capacity expanding unit. The gist is to provide a buffer capacity reducing means for reducing the buffer capacity when the transfer rate is higher.
[0016]
According to such a feature, when the transfer rate decreased due to congestion or reception error of the packet communication network is increased due to elimination of congestion or reception error of the packet communication network, the buffer capacity reduction means increases the buffer capacity. By returning (reducing) to a predetermined buffer capacity, the packet relay apparatus can maintain the buffer capacity at an appropriate level and effectively use the resources required to store the packets.
[0017]
A third feature of the present invention is that, in the first feature of the present invention, the packet relay apparatus reduces the buffer capacity when a predetermined time has elapsed with the buffer capacity expanded by the buffer capacity expanding means. The gist of the invention is to provide a buffer capacity reduction means.
[0018]
According to such a feature, the buffer capacity reduction means recovers the transfer rate that has been reduced due to congestion of the packet communication network or reception error when a predetermined time has elapsed with the buffer capacity expanded. By estimating and reducing the buffer capacity, the packet relay apparatus can maintain the buffer capacity at an appropriate level and effectively use the resources required for storing the packets.
[0019]
According to a fourth feature of the present invention, in the third feature of the present invention, the buffer capacity expanding means expands the buffer capacity according to the difference between the transfer rate measured by the transfer rate measuring means and a predetermined transfer rate. The gist of the invention is that the buffer capacity reducing means reduces the buffer capacity according to the difference between the transfer rate measured by the transfer rate measuring means and a predetermined transfer rate.
[0020]
According to such a feature, the packet capacity increasing means increases the buffer capacity in accordance with the difference between the transfer rate measured by the transfer rate measuring means and the predetermined transfer rate, so that the packet relay device is more than necessary. It is possible to prevent the buffer capacity from being increased.
[0021]
Further, the buffer capacity reducing means reduces the buffer capacity according to the difference between the transfer rate measured by the transfer rate measuring means and the predetermined transfer rate, so that the packet relay apparatus reduces the buffer capacity more than necessary. Can be prevented.
[0022]
According to a fifth aspect of the present invention, there is provided a packet relay method in which a packet relay apparatus having a predetermined buffer capacity relays a packet in a packet communication network, step A in which a transfer rate at the time of packet transfer is measured, and step A And a step B in which the buffer capacity is expanded when the transfer rate measured in (1) is lower than a predetermined transfer rate.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
(Configuration of packet relay device)
Hereinafter, the configuration of the packet relay apparatus according to the present embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a packet communication network in which a packet relay device according to this embodiment is installed.
[0024]
As shown in FIG. 1, the packet communication network includes radio base stations 2a and 2b, gateways 3a and 3b, and routers 4a to 4f. Hereinafter, a mode in which predetermined information is transmitted from the terminals 1a to 1d to the terminals 5a to 5d via the packet communication network will be described.
[0025]
Specifically, the terminals 1a and 1b such as a mobile phone and the terminal 1c such as a notebook personal computer divide predetermined information into packets and transmit them to the wireless base station 2a via a wireless line. Further, the terminal 1d such as a personal computer divides predetermined information into packets and transmits them to the gateway 3a.
[0026]
The radio base station 2a transmits the packets received from the terminals 1a to 1c to the gateway 3a. Further, the radio base station 2b transmits the packet received from the gateway 3b to the terminals 5a to 5c.
[0027]
The gateway 3a transmits the packet received from the radio base station 2a to the gateway 3b via the routers 4a to 4f. The gateway 3b transmits the packet received from the gateway 3a via the routers 4a to 4f to the radio base station 2b or the terminal 5d.
[0028]
The routers 4a to 4f relay packets from the gateway 3a to the gateway 3b according to a predetermined routing protocol.
[0029]
The terminals 5a and 5b such as a mobile phone and the terminal 5c such as a notebook personal computer receive a packet from the radio base station 2b via a radio line. Further, the terminal 5d such as a personal computer receives the packet from the gateway 3b.
[0030]
In the present embodiment, the packet relay device is provided in the radio base stations 2a and 2b, the gateways 3a and 3b, the routers 4a to 4f, the radio control device (not shown), or the like.
[0031]
FIG. 2 is a block diagram showing the configuration of the packet relay device in this embodiment. As shown in FIG. 2, the packet relay device 10 includes a reception unit 11, a reception buffer unit 12, a transfer buffer unit 13, a transfer unit 14, a transfer rate measurement unit 15, a buffer capacity change unit 16, a packet And a disposal unit 17.
[0032]
A plurality of receiving units 11 are provided for each of the other packet relay apparatuses 10 connected to the packet relay apparatus 10 (hereinafter referred to as a reception source). Each receiving unit 11 receives a predetermined packet from a receiving source assigned to the receiving unit 11.
[0033]
The reception buffer unit 12 corresponds to each of the plurality of reception units 11. Each reception buffer unit 12 stores a packet received by the reception unit 11 corresponding to the reception buffer unit 12. Further, the packet stored in the reception buffer unit 12 is input to a predetermined transfer buffer unit 13 according to the destination of the packet and a predetermined routing table.
[0034]
The transfer buffer unit 13 corresponds to each of the plurality of transfer units 14. Each transfer buffer unit 13 stores the packets transferred by the transfer unit 14 corresponding to the transfer buffer unit 13 in the order of input from the reception buffer unit 12.
[0035]
The reference capacity of the transfer buffer unit 13 is based on the assumption that the packet is transferred to a transfer destination assigned to the transfer buffer unit 13 at a predetermined transfer rate (hereinafter referred to as a reference transfer rate). It is assumed that the packet is set to an appropriate level so that a packet exceeding the allowable delay time is not transferred.
[0036]
The reference transfer rate is an average value of transfer rates when transferring packets to a transfer destination. Further, the reference transfer rate may be a different value for each transfer destination.
[0037]
Here, in the present embodiment, the transfer buffer unit 13 constitutes a packet storage unit having a predetermined buffer capacity.
[0038]
A plurality of transfer units 14 are provided for each of the other packet relay devices 10 connected to the packet relay device 10 (hereinafter referred to as transfer destination). Each transfer unit 14 inputs a packet stored in the transfer buffer unit 13 corresponding to the transfer unit 14 to the transfer destination assigned to the transfer unit 14, and the packet is input to the transfer buffer unit 13. Transfer in order (based on FIFO principle). The transfer unit 14 transfers the packet at a transfer rate according to the state of the packet communication network up to the transfer destination assigned to the transfer unit 14.
[0039]
The transfer rate measuring unit 15 constitutes a transfer rate measuring unit that measures a transfer rate when a packet is transferred from the transfer unit 14 to a transfer destination assigned to the transfer unit 14.
[0040]
When the transfer rate measured by the transfer rate measuring unit 15 is lower than the reference transfer rate, the buffer capacity changing unit 16 expands the capacity of the transfer buffer unit 13 according to these differences. Further, the buffer capacity changing unit 16 responds to these differences when the transfer rate measured by the transfer rate measuring unit 15 is higher than the reference transfer rate while the capacity of the transfer buffer unit 13 is expanded. The capacity of the transfer buffer unit 13 is reduced.
[0041]
Specifically, the buffer capacity changing unit 16 changes the capacity of the transfer buffer unit 13 as shown in FIG. FIG. 3 is a diagram for explaining how the capacity of the transfer buffer unit 13 is changed along the time axis. In FIG. 3, it is assumed that the transfer buffer unit 13 has a reference capacity of 3 packets, a reference transfer rate of 1 packet per unit time, and the transfer buffer unit 13 always receives one packet per unit time. . The maximum allowable delay time of the packet input to the transfer buffer unit 13 is assumed to be 7 unit times.
[0042]
In the first unit time, the packet a stored in the transfer buffer unit 13 is transferred to a predetermined transfer destination by the transfer unit 14, and the packet d stored in the reception buffer unit 12 is transferred to the transfer buffer unit 13. Entered.
[0043]
Here, since the transfer rate (1 packet / unit time) measured by the transfer rate measuring unit 15 is the same as the reference transfer rate (1 packet / unit time), the buffer capacity changing unit 16 Do not change capacity.
[0044]
In the second unit time, the packet b stored in the transfer buffer unit 13 is transferred to a predetermined transfer destination by the transfer unit 14, and the packet e stored in the reception buffer unit 12 is transferred to the transfer buffer unit 13. Entered.
[0045]
Here, since the transfer rate (1 packet / unit time) measured by the transfer rate measuring unit 15 is the same as the reference transfer rate (1 packet / unit time), the buffer capacity changing unit 16 Do not change capacity.
[0046]
Note that the residence time of the packets c to d increases by one unit time. For example, the residence time of the packet c is 3 unit hours.
[0047]
In the third unit time, the packet c stored in the transfer buffer unit 13 is not transferred due to congestion of the packet communication network or a reception error, and the packet f stored in the reception buffer unit 12 is transferred. The data is input to the buffer unit 13.
[0048]
Here, since the transfer rate (0 packet / unit time) measured by the transfer rate measuring unit 15 is lower than the reference transfer rate (1 packet / unit time), the buffer capacity changing unit 16 uses the transfer rate measuring unit 15. The capacity of the transfer buffer unit 13 is expanded according to the difference (1 packet / unit time) between the measured transfer rate and the reference transfer rate.
[0049]
That is, the buffer capacity changing unit 16 increases the capacity of the transfer buffer unit 13 by one packet, and the transfer buffer unit 13 stores the input packet f without discarding the packet.
[0050]
Note that the residence times of the packets c to e increase by one unit time. For example, the residence time of the packet c is 4 unit hours.
[0051]
In the fourth unit time, the packet c stored in the transfer buffer unit 13 is not transferred due to congestion of the packet communication network or occurrence of a reception error, and the packet g stored in the reception buffer unit 12 is transferred. The data is input to the buffer unit 13.
[0052]
Here, since the transfer rate (0 packet / unit time) measured by the transfer rate measuring unit 15 is lower than the reference transfer rate (1 packet / unit time), the buffer capacity changing unit 16 uses the transfer rate measuring unit 15. The capacity of the transfer buffer unit 13 is expanded according to the difference (1 packet / unit time) between the measured transfer rate and the reference transfer rate.
[0053]
That is, the buffer capacity changing unit 16 increases the capacity of the transfer buffer unit 13 by one packet, and the transfer buffer unit 13 stores the input packet g without discarding the packet.
[0054]
Note that the residence time of the packets c to f increases by 1 unit time. For example, the residence time of the packet c is 5 unit hours.
[0055]
In the fifth unit time, the packet c stored in the transfer buffer unit 13 is not transferred due to congestion of the packet communication network or a reception error, and the packet h stored in the reception buffer unit 12 is transferred. The data is input to the buffer unit 13.
[0056]
Here, since the transfer rate (0 packet / unit time) measured by the transfer rate measuring unit 15 is lower than the reference transfer rate (1 packet / unit time), the buffer capacity changing unit 16 uses the transfer rate measuring unit 15. The capacity of the transfer buffer unit 13 is expanded according to the difference (1 packet / unit time) between the measured transfer rate and the reference transfer rate.
[0057]
That is, the buffer capacity changing unit 16 expands the capacity of the transfer buffer unit 13 by one packet, and the transfer buffer unit 13 stores the input packet h without discarding the packet.
[0058]
Note that the residence times of the packets c to g increase by 1 unit time. For example, the residence time of packet c is 6 unit hours.
[0059]
During the sixth unit time, the packets c to e stored in the transfer buffer unit 13 are transferred to a predetermined transfer destination by the transfer unit 14 due to elimination of congestion of the packet communication network, reception errors, and the like. The packet i stored in the unit 12 is input to the transfer buffer unit 13.
[0060]
Here, the buffer capacity changing unit 16 has a transfer rate (3 packets / unit time) measured by the transfer rate measuring unit 15 higher than the reference transfer rate (1 packet / unit time). The capacity of the transfer buffer unit 13 is reduced according to the difference (2 packets / unit time) between the transfer rate measured by the transfer rate measuring unit 15 and the reference transfer rate.
[0061]
That is, the buffer capacity changing unit 16 reduces the capacity of the transfer buffer unit 13 by two packets, and brings the capacity of the transfer buffer unit 13 close to the reference capacity.
[0062]
Note that the residence times of the packets c to h increase by 1 unit time. For example, the residence time of the packet c is 7 unit hours, but the packet c is transferred without exceeding the maximum allowable delay time (7 unit times).
[0063]
In the seventh unit time, the packet f and the packet g stored in the transfer buffer unit 13 are transferred to a predetermined transfer destination by the transfer unit 14 due to elimination of congestion of the packet communication network, a reception error, and the like. The packet j stored in the unit 12 is input to the transfer buffer unit 13.
[0064]
Here, the buffer capacity changing unit 16 has a transfer rate (2 packets / unit time) measured by the transfer rate measuring unit 15 higher than the reference transfer rate (1 packet / unit time). The capacity of the transfer buffer unit 13 is reduced according to the difference (1 packet / unit time) between the transfer rate measured by the transfer rate measuring unit 15 and the reference transfer rate.
[0065]
That is, the buffer capacity changing unit 16 reduces the capacity of the transfer buffer unit 13 by one packet, and returns the capacity of the transfer buffer unit 13 to the reference capacity.
[0066]
The residence time of packet f to packet i increases by one unit time.
[0067]
Further, the buffer capacity changing unit 16 is configured to reduce the capacity of the transfer buffer unit 13 when a predetermined time elapses while the capacity of the transfer buffer unit 13 is larger than the reference capacity. Also good.
[0068]
In the present embodiment, the buffer capacity changing unit 16 constitutes a buffer capacity expanding unit that expands the capacity of the transfer buffer unit 13 when the transfer rate measured by the transfer rate measuring unit 15 is lower than the reference transfer rate. To do. Further, the buffer capacity changing unit 16 transfers the transfer buffer when the transfer rate measured by the transfer rate measuring unit 15 is higher than the reference transfer rate while the capacity of the transfer buffer unit 13 is larger than the reference capacity. The buffer capacity reducing means for reducing the capacity of the unit 13 is configured.
[0069]
The packet discard unit 17 discards the packet having the longest residence time in the transfer buffer unit 13 when an overflow occurs.
[0070]
Specifically, as illustrated in FIG. 4, the packet discard unit 17 has the longest residence time in the transfer buffer unit 13 when an overflow occurs in a state where the packets a to f are stored in the transfer buffer unit 13. Packet a is discarded and packet g is stored in transfer buffer unit 13.
[0071]
(Operation of packet relay device)
FIG. 5 describes the operation of the packet relay apparatus according to this embodiment with reference to the drawings. FIG. 5 is a flowchart showing the operation of the packet relay device 10.
[0072]
As shown in FIG. 5, in step 10, the packet relay apparatus 10 measures a transfer rate at the time of transferring a packet.
[0073]
In step 20, the packet relay device 10 compares the transfer rate measured in step 10 with the reference transfer rate. When the transfer rate measured in Step 10 is smaller than the reference transfer rate, the packet relay apparatus 10 proceeds to Step 30, and in the case where the transfer rate measured in Step 10 is larger than the reference transfer rate. The process proceeds to step 40.
[0074]
In step 30, the packet relay device 10 expands the capacity of the transfer buffer unit 13 according to the difference between the transfer rate measured in step 10 and the reference transfer rate.
[0075]
In step 40, the packet relay device 10 compares the capacity of the transfer buffer unit 13 with the reference capacity. When the capacity of the transfer buffer unit 13 is larger than the reference capacity, the packet relay apparatus 10 proceeds to step 50, and when the capacity of the transfer buffer unit 13 is not larger than the reference capacity. In this case, the series of processes is terminated.
[0076]
In step 50, the packet relay device 10 reduces the capacity of the transfer buffer unit 13 according to the difference between the transfer rate measured in step 10 and the reference transfer rate.
[0077]
(Operation and effect of packet relay device)
According to the packet relay apparatus 10 in the present embodiment, when the transfer rate measured by the transfer rate measuring unit 15 is temporarily lower than the reference transfer rate due to the occurrence of packet communication network congestion or reception error, the buffer The capacity changing unit 16 expands the capacity of the transfer buffer unit 13 in accordance with the difference between the transfer rate and the reference transfer rate, so that the packet relay device 10 has the maximum allowable residence time when the transfer rate increases. Packets that may be transferred without exceeding the time can be prevented from being discarded.
[0078]
Further, according to the packet relay device 10 in the present embodiment, when the transfer rate measured by the transfer rate measuring unit 15 is higher than the reference transfer rate due to the congestion of the packet communication network or the elimination of the reception error, the buffer capacity When the changing unit 16 reduces the capacity of the transfer buffer unit 13 according to the difference between the transfer rate and the reference transfer rate, the packet relay device 10 increases the capacity of the transfer buffer unit 13 more than necessary. This can be prevented.
[0079]
【The invention's effect】
According to the packet relay apparatus and the packet relay method of the present invention, the packet relay apparatus temporarily decreases the transfer rate when transferring a packet from a predetermined transfer rate due to congestion of the packet communication network or occurrence of a reception error. In this case, if the transfer rate is increased, it is possible to prevent a packet that may be transferred without exceeding the maximum allowable delay time from being retained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a packet communication network in which a packet relay apparatus 10 packet relay apparatus according to the present embodiment is installed.
FIG. 2 is a block diagram illustrating a configuration of a packet relay device 10 according to the present embodiment.
FIG. 3 is a diagram for explaining enlargement / reduction of the capacity of a transfer buffer unit 13 in the present embodiment;
FIG. 4 is a diagram illustrating a manner in which a packet stored in a transfer buffer unit 13 is discarded when an overflow occurs in the present embodiment.
FIG. 5 is a flowchart showing an operation of the packet relay apparatus 10 in the present embodiment.
FIG. 6 is a diagram for explaining the capacity of a buffer in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a-1d ... terminal, 2a * 2b ... wireless base station, 3a * 3b ... gateway, 4a-4f ... router, 5a-5d ... terminal, 10 ... packet relay apparatus, 11 ... receiving part, 12 ... receiving buffer part, 13 Transfer buffer unit 14 Transfer unit 15 Transfer rate measurement unit 16 Buffer capacity changing unit 17 Packet discard unit

Claims (5)

A packet relay device that relays a packet in a packet communication network,
Packet storing means having a predetermined buffer capacity;
A transfer rate measuring means for measuring a transfer rate when transferring the packet;
Buffer capacity expanding means for expanding the buffer capacity when the transfer rate measured by the transfer rate measuring means is lower than a predetermined transfer rate determined in accordance with the transfer destination of the packet ;
The packet relay apparatus, wherein the predetermined buffer capacity is determined according to a maximum allowable delay time that is a delay time allowed for the packet and the predetermined transfer rate .   Buffer capacity reducing means for reducing the buffer capacity when the transfer rate measured by the transfer rate measuring means is higher than the predetermined transfer rate with the buffer capacity enlarged by the buffer capacity expanding means. The packet relay device according to claim 1, comprising:   2. The packet relay according to claim 1, further comprising buffer capacity reduction means for reducing the buffer capacity when a predetermined time elapses with the buffer capacity being enlarged by the buffer capacity expansion means. apparatus. The buffer capacity expanding means expands the buffer capacity according to a difference between the transfer rate measured by the transfer rate measuring means and the predetermined transfer rate,
The packet according to claim 3, wherein the buffer capacity reducing means reduces the buffer capacity according to a difference between the transfer rate measured by the transfer rate measuring means and the predetermined transfer rate. Relay device. A packet relay method in which a packet relay device having a predetermined buffer capacity relays a packet in a packet communication network,
Step A in which a transfer rate when transferring the packet is measured;
The buffer capacity is increased when the transfer rate measured in the step A is lower than a predetermined transfer rate determined according to the transfer destination of the packet ; and
The packet relay method according to claim 1, wherein the predetermined buffer capacity is determined according to a maximum allowable delay time which is a delay time allowed for the packet and the predetermined transfer rate .

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