JP2002344509A - Method for controlling readout rate of router and packet and its process program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a router capable of dynamically controlling an allocation of a band for an input traffic of each quality service in order to realize communication services of each quality service. SOLUTION: A router 2 comprises a first class buffer 22 provided corresponding to a quality class which provides the most priority of a communication for storing a received packet; second and third class buffers 24, 26 provided corresponding to one or a plurality of quality classes other than the highest priority for storing the received packet, a monitor 30 for monitoring the queue length of the packet stored in the first class buffer 22, a readout rate control unit 40 for dynamically controlling the readout rate of the packet of the first to third class buffers 22, 24, 26 based on the queue length of the first class buffer 22 monitored, and a sending part 50 for sending the readout packet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a router for performing IP routing for realizing a quality service, and more particularly, to a router and a packet capable of dynamically controlling the allocation of a bandwidth to input traffic for each quality service. And a processing program therefor.

[0002]

2. Description of the Related Art At present, when business applications are used with a certain quality in an IP network,
PQ (Priority Queuing), WFQ (Weighted Fair Q)
ueueing) or a method PQWFQ combining PQ and WFQ (Miyasaka et al., “Delay and Throughput Characteristics in Diffserv Type Scheduler”, IEICE Technical Report, SSE99-1
61, Mar. 2000)). The PQ is a traffic control method in which a packet is read preferentially at the time of input to a router interface for which delay guarantee is set in advance, and is then transmitted. WFQ is a traffic control method that multiplexes with best-effort traffic and secures a response by weighting. It is a technology that can guarantee the minimum bandwidth usage and is suitable from the viewpoint of fairness in bandwidth usage for each quality class. is there. For example, SNA (System Network Architectur) which is a host communication protocol
Suitable for data traffic requiring high response such as e).

[0003] The PQWFQ is a technique using the PQ and the WFQ, and a packet is read via the WFQ only when a packet of the highest priority quality class read by the PQ does not exist in the queue. Here, in order to secure the bandwidth of the traffic of the quality class passing through the WFQ, it is necessary to limit the available bandwidth of the traffic of the quality class read by the PQ. In such a case, the necessary bandwidth for data traffic passing through the WFQ is secured by shaping and bandwidth usage restrictions.

[0004]

SUMMARY OF THE INVENTION As described above, PQW
In the case where the use bandwidth of a class read by the FQ is limited, when traffic accommodated in the class increases, communication quality deteriorates due to delay in the class. The traffic accommodated in the class is
It is assumed that the application requires strict quality assurance. In order to achieve the required quality, it is necessary to statically allocate a sufficient band as in the past, and the class passing through the WFQ at this time is required. However, there is a problem that the communication quality that can be guaranteed by the method is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to realize a communication service for each quality service in a router performing IP routing. It is an object of the present invention to provide a router capable of dynamically controlling the allocation of a band, a packet read rate control method, and a processing program therefor.

[0006]

(1) In order to achieve the above object, a router according to the present invention is provided corresponding to a quality class that defines the highest priority of communication, and stores received packets. A first buffer, one or more second buffers provided corresponding to one or more quality classes other than the highest priority and storing received packets, and one or more second buffers stored in the first buffer. Monitoring means for monitoring the queue length of packets, and dynamically controlling the rate of reading packets from the first buffer and the second buffer based on the queue length of the first buffer monitored by the monitoring means. It is characterized by having read rate control means and sending means for sending the read packet.

(2) In the router according to the present invention, in the router according to the above (1), the read rate control means may be configured such that the monitoring means causes the queue length of the first buffer to be a first predetermined length. , The rate of reading packets from the first buffer is increased,
If the queue length of the first buffer is monitored below a second predetermined length that is less than or equal to the first predetermined length, the read rate is changed to the read rate before increasing the packet read rate of the first buffer. It is characterized by doing.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a block diagram of a router according to the present invention. FIG. 2 is a flowchart for explaining the operation of the router in FIG.

The configuration of the router 2 according to the present invention will be described with reference to FIG. The router 2 includes a receiving unit 10, a class buffer group 20, a monitoring unit 30, a read rate control unit 40, and a sending unit 50.

[0010] The receiving unit 10 receives a packet transmitted from outside the router 2. The priority order of communication is determined for this packet. The receiving unit 10 transmits the received packet to a predetermined class buffer among the first to third class buffers 22, 24, and 26 for each priority order. The class buffer group 20 includes first to third class buffers 22, 24, and 26. First
Each of the class buffers 22, 24, and 26 of
It is provided corresponding to the priority order of the communication. Here, for example, the first class buffer 22 defines the highest communication priority (highest priority), the second class buffer 24 defines the medium communication priority, and the third class buffer 24 defines the third communication buffer.
In the class buffer 26, the priority of normal communication is defined. The monitoring unit 30 has a function of monitoring the queue length of the packet stored in the first class buffer 22.

The read rate controller 40 has a function of increasing the rate at which packets are read from the first class buffer 22 when the monitored queue length of the first class buffer 22 exceeds a predetermined length. This "exceeds"
In particular, the predetermined length of the immediately preceding queue length is referred to as the “upper limit of the threshold value”
Is defined. Further, when the queue length of the monitored first class buffer 22 falls below a predetermined length that is equal to or less than the upper limit value of the threshold after the queue length exceeds the upper limit value, It has a function of changing the rate at which packets of the first class buffer 22 are read out to a reading rate before the packet exceeds the upper limit. Note that the predetermined length of the queue length immediately before “below” is particularly defined as “the lower limit of the threshold value”. Further, the reading rate control unit 40
In order to realize the WFQ technology described above, a function is provided for controlling the read rates of the second and third class buffers 24 and 26, which are class buffers other than the first class buffer 22 having the highest priority. The sending unit 50 is configured to
The packet read from the third class buffers 22, 24, 26 is transmitted.

The router 2 mainly incorporates a monitoring unit 30 and a read rate control unit 40, which are characteristic configurations employed in the present invention, based on the PQWFQ technology described above.

Next, the operation of the router 10 will be described with reference to the flowchart of FIG. The receiving unit 10 receives the packet (Step S101). The receiving unit 10 sorts each packet according to the defined communication priority,
The data is transmitted to each of the first to third class buffers 22, 24, and 26 (step S102). The monitoring unit 30 checks whether the queue length of the first class buffer 22 has exceeded the upper limit of the threshold (Step S103). When confirming that the queue length has exceeded the upper limit of the threshold, the read rate control unit 40 obtains this confirmation information from the monitoring unit 30 and stabilizes the communication of the first class buffer 22 having the highest communication priority. In order to perform this, the read rate of the first class buffer 22 is increased (step S104).
Along with this, the reading of packets from the second and third class buffers 24 and 26 having relatively low priority is suppressed, and the reading rate of the first class buffer 22 is relatively increased.

The monitoring unit 30 includes the first class buffer 22
It is determined whether or not the queue length has become smaller than the lower limit value of the threshold (step S105). Upon confirming that the queue length has fallen below the lower limit value of the threshold value, the read rate control unit 40
Obtains the confirmation information from the monitoring unit 30 and recovers the read rates of the second and third class buffers 24 and 26 having relatively low priority in which packet reading is suppressed. The readout rate of step S22 is suppressed (step S106).

In step S103, unless the monitoring unit 30 confirms that the queue length of the first class buffer 22 has exceeded the upper limit of the threshold value, the communication at the same read rate is executed. . In step S105, the monitoring unit 30 sets the first
If it is not confirmed that the queue length of the class buffer 22 becomes smaller than the lower limit value of the threshold value, the communication at the high read rate is executed as it is.

Here, an example of a method of setting the upper limit value and the lower limit value of the above-described threshold value will be described in connection with a case where communication of certain voice data composed of a single fixed-length packet is defined as the highest priority. Will be explained.

Let α (msec) be the delay target value of the voice data in the router 2. At this time, the upper limit of the threshold is denoted by N ₂ , and the lower limit of the threshold is denoted by N ₁ .

The packet length of the application used in the highest priority quality class is a fixed length a (byte). The normal read rate of the highest priority quality class is b ₁ (kbps), and the read rate when the read rate is increased is b.
Assuming that ₂ (kbps), the transfer delays w ₁ and w ₂ of one packet at each readout rate are: w ₁ = 8a / b ₁ (msec) (formula a) w ₂ = 8a / b ₂ (msec) (Equation b). Here, MTU (Max Transfer Unit)
Taking into account that a transmission waiting time β (msec) having a packet length defined by the above may occur, the following two states (A) and (B) are considered as possible packet conditions.

The hits just before exceeding the upper limit value N ₂ of the threshold to increase the reading rate ((A) delays the previous packet of the upper limit value N ₂ of the threshold if the maximum) (N 2 _-1) -th packet In the case of the last column, the transfer delay when (N ₂ −1) packets are read out at the rate b ₁ is smaller than the delay target value α, so that it is necessary to satisfy the following (formula c). . w ₁ (N ₂ −1) + β ≦ α (Expression c) That is, N ₂ ≦ 1 + (α−β) / w ₁ (Expression d)

[0020] If the upper limit value N ₂ -th packet threshold to increase the reading rate ((B) the upper limit N ₂ and delay of N ₂ th packet that may be the largest threshold) is the last column Suppose that the delay of this packet is maximized. In this case, the last column from the _(N 2 -N ₁₎ pieces worth is the packet is read out at a rate _{b 2,} a packet from the front row _{one N} of read at the rate _{b 1} is transmitted. A delay of N ₂ -th packet should be a value smaller than the delay target value alpha, it is necessary to satisfy the following equation. w ₂ (N ₂ −N ₁ ) + w ₁ N ₁ + β ≦ α (formula e)

[0021] In practice, the maximum value of the delay for the case of the above (A) is dominant term, to approximate the delay target delay alpha, is set to the maximum value of the settable range N _2. Assuming that the maximum value that can be set from the above (formula d) is N ₂ , N ₂ = 1 + (α−β) / w ₁ (formula f)

[0022] In the case of the (B), since the timing of reading rate as the lower limit value N ₁ of the threshold is larger returns to b ₁ is a normal rate is faster, the number of reads to the correspondingly large amount of data based traffic Assigned.
Therefore, in order to reduce the deterioration of the quality of the traffic that passes through the WFQ, it becomes a solution in which the N ₁ obtained by solving the inequality of the equation (c) in the range satisfying equation (f) is determined, as follows. N ₁ = (α-β-w ₂ N ₂ ) / (w ₁ -w ₂ ) (formula g)

[0023] By the above method, it is possible to set the upper limit value N ₂ and the lower limit value N ₁ of the threshold, it is possible while satisfying the range of the delay guarantees, to reduce deterioration of the quality of the data-traffic accommodated class .

The router according to the present invention sets an upper limit value and a lower limit value of a threshold value based on a delay guarantee value required for traffic, and changes a read rate based on these values,
It is possible to dynamically control bandwidth allocation. This makes it possible to suppress quality degradation for each quality service in a router that performs IP routing, and to realize communication service QoS.

The present invention is not limited to the example described with reference to FIGS. 1 and 2, and various changes can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the packet reading rate is changed (for example,
Although the rate R1 is set, a plurality of threshold values for changing the read rate (for example, rate R1 <R2 <R
3, three types). By doing so, it becomes possible to reliably execute processing of continuously received packets without lowering the quality of service QoS. In this case, a function of monitoring the plurality of threshold values (R1, R2, R3) by the monitoring unit 30 in FIG. 1 and changing the packet read rate by the read rate control unit 40 is added.

In FIG. 1 of the above-described embodiment, the first to third class buffers 22, 24, and 26 are used as buffers related to the quality service. However, the present invention is not limited to these three quality services. , Two or more buffers corresponding to the quality service may be used.

Further, in the above-described embodiment, the operation and effect have been described based on the PQWFQ technology. However, even when the monitoring unit 30 and the readout rate control unit 40 in the present invention are used for the PQ technology, it is an object of the present invention. Dynamic control of band allocation can be performed.

In the above-described embodiment and the above-described various modifications, a program for performing the processing may be stored as application software in a recording medium such as a hard disk. By doing so, it becomes possible to store and sell the program or the like on a portable recording medium such as a CD-ROM, or to carry the program.

[0029]

The router according to the present invention sets an upper limit and a lower limit of a threshold value based on a delay guarantee value required for traffic, changes the readout rate based on these values, and activates bandwidth allocation. It is possible to control it. This makes it possible to suppress quality degradation for each quality service in a router that performs IP routing, and to realize communication service QoS. Also, by applying the means for controlling the packet reading rate according to the present invention to the conventional PQ technology, PQWFQ technology, or the like, it becomes possible to realize a function of dynamically allocating a band.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a router according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the router shown in FIG. 1;

[Explanation of symbols]

 2: Router 10: Receiving unit 20: Class buffer group 22: First class buffer 24: Second class buffer 26: Third class buffer 30: Monitoring unit 40: Read rate control unit 50: Sending unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takanori Iwai 2-3-1 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Inventor Hiroshi Ota 2-3-3, Otemachi, Chiyoda-ku, Tokyo No. 1 Nippon Telegraph and Telephone Corporation F-term (reference) 5K030 HD03 KA03 LA03 MB15

Claims (6)

[Claims] 1. A first buffer for storing a received packet, the first buffer being provided corresponding to a quality class that defines the highest priority of communication, and one or more quality classes other than the highest priority being stored. One or more second buffers for storing received packets, monitoring means for monitoring the queue length of packets stored in the first buffer, and the second buffer being monitored by the monitoring means. A read rate control means for dynamically controlling a read rate of packets of the first buffer and the second buffer based on the queue length of the first buffer; and a sending means for sending the read packets. A router comprising: 2. The router according to claim 1, wherein the read rate control unit monitors the queue length of the first buffer exceeding a first predetermined length by the monitoring unit. Increasing the rate of reading packets from the first buffer, and thereafter monitoring the queue length of the first buffer below a second predetermined length that is less than or equal to the first predetermined length. A router that changes the read rate of the packets in the first buffer to the read rate before the increase. A monitoring step of monitoring a queue length of a packet stored in a first buffer for storing a received packet, the monitoring step being provided in correspondence with a quality class defining the highest priority of communication; The first buffer is provided corresponding to one or a plurality of quality classes other than the highest priority based on the queue length of the first buffer monitored by the first buffer and stores received packets. A read rate control step of dynamically controlling a read rate of a packet with one or a plurality of second buffers. 4. The read rate control method according to claim 3, wherein the read rate control step monitors the queue length of the first buffer exceeding a first predetermined length by the monitoring step. The reading rate of the packets of the first buffer is increased, and thereafter, the queue length of the first buffer falls below a second predetermined length that is equal to or less than the first predetermined length. The first
The packet read rate of the buffer of (b) is changed to the read rate before the increase. 5. A packet read rate control processing program for causing a computer to execute each processing in the packet read rate control method according to claim 3 or 4. 6. A computer-readable recording medium on which the packet read rate control processing program according to claim 5 is recorded.