JP2003273919A - Connection management method, program, router, cable modem and network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance quality of bi-directional service by preventing system congestion caused in burst mode by traffic in a CATV Internet system. <P>SOLUTION: When connection to be established via first and second network devices is managed, the first network device transmits a predetermined signal 1 to the second network device according to use conditions of network resources. The second network device refers to whether or not a signal 2 that requests establishment of new connection is included in signals to be transmitted from the second network device to the first network device according to the signal 1. When the signal 2 is detected, the second network device breaks off a prescribed unit of data including the signal 1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for suppressing communication congestion in a CATV station of a cable television (CATV) Internet system.

[0002]

2. Description of the Related Art There is a so-called cable television (CATV) Internet system as one means for providing an environment for connecting to the Internet. In the CATV Internet system, a coaxial cable that connects a CATV station and its subscriber's home is used to deliver various TV channels to the subscriber's home, and to perform vertical transmission and reception to the subscriber's home. Provide an internet connection environment.

Generally, CATV stations deliver not only terrestrial broadcasting but also satellite broadcasting. A two-way communication function has been added to BS digital broadcasting. For this reason, full-scale provision of viewer-participating programs, such as quiz programs that the viewers themselves answer and programs that require the viewers to directly answer the questionnaire during the program, is expected.

The CATV subscriber also uses a coaxial cable as an upstream transmission line for this two-way communication. Upstream communication at each subscriber's house is via a CATV station, management IP network (man
aged Internet Protocol ne
via the network) to the aggregation server of the broadcasting station.

[0005]

When an attempt is made to collect upstream data in a viewer participation type program, a large number of subscribers will simultaneously reply. Then, the CATV station and management I
Traffic congestion may occur in the P network,
As a result, service quality may be impaired.

The present invention has been made in view of such a situation, and the problem to be solved by the present invention is to prevent system congestion due to bursty generation of traffic in the CATV Internet system as described above. , To improve the quality of interactive services.

[0007]

In order to solve this problem, the present invention provides the following connection management method, program, router, cable modem and network system.

According to the present invention, in a method for managing a connection established via first and second network devices, the first network device sends the second network device to the second network device according to the usage status of network resources. It is determined whether the step 1 of transmitting a predetermined signal A and the signal B requesting the establishment of a new connection are included in the signals transmitted from the second network device to the first network device. , Step 2 referred to by the second network device according to the signal A, and Step 3 in which, when the signal B is detected in Step 2, the second network device discards a predetermined unit of data including the signal B. A connection management method characterized by including the above.

Subsequent to the step 3, the first network device is further changed to the second network device according to the use status of the network resource.
It is preferable to include a step 4 of transmitting a predetermined signal to the network device in step 2 and a step 5 of stopping the data discarding in step 3 by the second network device in response to the signal B.

It is conceivable that the first network device judges the utilization status of the network resource by comparing the amount of data retained inside with a predetermined threshold value.

Different thresholds may be applied in steps 1 and 4.

Instead of discarding the data in step 3, the second network device may retain the data.

As a typical example, the connection management method is characterized in that the first network device is a router and the second network device is a cable modem.

The present invention relates to a method for suppressing congestion in a communication system that uses the TCP / IP protocol, and according to the usage status of network resources, TCP (Transmission Control) is used.
l Protocol) header control flag S
It can also be regarded as a congestion suppressing method characterized by discarding a frame in which YN is 1.

Further, according to the present invention, in a program for controlling the operation of a router, a signal A for instructing to discard a request for establishment of a new connection is provided to the downstream of the traffic according to the amount of traffic in one direction. Provided is a program that causes a router to execute a process of transmitting.

In this program, further, according to the amount of traffic, to the downstream of the traffic,
It is desirable to cause the router to execute a process of transmitting a signal indicating the suspension of discarding the establishment request.

The amount of data accumulated in the router may be compared with a predetermined threshold value, and the router may be caused to execute a process of determining whether to transmit the signal A and the packet A according to the comparison result. .

The threshold for determining the transmission of the signal A and the threshold for determining the transmission of the signal A may be different.

As a typical example, it is conceivable to connect a cable modem to the downstream of the traffic and transmit the signal A and the signal to the cable modem.

The above program may be recorded in a machine-readable recording medium and provided. Further, it may be provided as a router which stores such a recording medium and operates according to a program.

Further, according to the present invention, in the program for controlling the operation of the cable modem, when the signal A according to the use condition of the network resource is received, the signal transmitted to the network is referred to and a new connection is established. A program characterized by causing a cable modem to execute a process 1 of detecting the presence or absence of a signal B requesting establishment and a process 2 of discarding a predetermined unit of data including the signal B when the signal B is detected. provide.

In this program, further, when a signal according to the usage status of network resources is received,
It is desirable to cause the cable modem to execute the processing of stopping the processing 2.

Instead of discarding the data in process 2, the cable modem may be caused to execute a process of storing the data.

Similar to the program described above, the program may be provided as a machine-readable recording medium. Further, such a recording medium may be stored and provided as a cable modem that operates according to a program.

Further, the present invention provides a network system including the above router and cable modem.

This network system is particularly connected to a terminal device (set-top box or personal computer) connected to a cable modem, an IP network connected to a router, and an IP network, and collects data from the terminal device. A server may be further provided.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION A system configuration of a CATV Internet system 100 according to a first embodiment of the present invention will be described with reference to FIG.

The broadcasting station 10 puts a television program on a digital signal and sends it via a satellite 20 to a cable TV (CATV).
Deliver to station 30. The CATV station 30 delivers the digital signal received by the digital broadcasting facility 31 to the subscriber's home 40 of the CATV network. Actually, CATV
Although a plurality of subscriber homes 40 exist under the control of the station 30, they are omitted here.

On the other hand, the digital broadcasting facility 31 constantly monitors the digital signal, predicts the occurrence of viewer data from the control information superimposed on the digital signal, and notifies the management server 32 of this. Here, the viewer data is data transmitted in the upstream direction from the subscriber's house to the broadcasting station. The management server 32 is a server that determines the band allocation policy for the CATV uplink, dynamically determines the band allocation policy in consideration of other conditions, and then notifies the cable modem termination device (CMTS) 33 of this. To do. Here, the policy determined by the management server 32 includes the best effort traffic (hereinafter BE) and the QoS (Qual).
It is the guaranteed distribution of viewer data traffic.

The CMTS 33 is a station side device in the CATV Internet system 100, and allocates the time band of the CATV uplink to various applications (data reservation area, health check area, user data area) and CM 41.
Communication control. Further, according to the notification from the management server 32, the user data area is further divided into BE and viewer data band, and the upstream band is allocated.

The CM 41 is a subscriber side device in the CATV Internet system 100, and under the control of the CMTS 33, performs upstream and downstream Ether frame communication. Further, the CM 41 has a packet classification function, and judges whether the Ethernet frame received from the subordinate PC 42 or the set top box (STB) 43 is BE data or viewer data, and according to each QoS level. Uplink transmission processing is performed under the control of the CMTS 33.

The viewer data transmitted from the STB 43 reaches the totaling server 11 of the broadcasting station 10 via the hub (HUB) 44, CM 41, CMTS 33, router 34, and management IP network 50. The counting server 11 counts the viewer data in response to the viewer data. This tabulation result is the program broadcasting device 1.
It is referred to from 2 and reflected in the program.

Next, the CATV Internet system 1
The operation of 00 to suppress congestion will be described below. For example, when viewers' responses frequently occur frequently, when the processing performance of the router is insufficient, or when the surplus bandwidth of the management IP network is insufficient, viewer data is accumulated in the router and congestion occurs. As a result, the quality of service to most viewers may deteriorate. On the other hand, C
In the ATV Internet system 100, the router 34
Predicts the occurrence of a congestion state, and when the possibility of falling into the congestion state increases, the CM 41 suppresses the generation of new traffic.

That is, the router 34 predicts the occurrence of a congestion state based on the amount of data buffered in itself.
When there is a high possibility that a congestion state will occur, a new TCP will be sent to all CMs 41 under its control before falling into the congestion state.
A signal (hereinafter referred to as a suppression signal) that instructs not to transmit the connection establishment request is transmitted.

The CM 41, which has received the inhibition signal, detects the presence / absence of a signal requesting the establishment of a connection. That is, the SYN flag of the control flag in the TCP header of each upstream Ethernet frame is referred to. Then, when an upstream Ethernet frame whose SYN flag is 1 is detected, the upstream Ethernet frame is discarded. By this process, new TCP
It will prevent the connection from being established. as a result,
The communication of the currently maintained TCP connection is guaranteed.

The SYN flag will now be described with reference to FIG. 2. The TCP header has a 6-bit control flag, and the control flag serves as data control information in the order of 0th bit to 5th bit. UR
It has G, ACK, PSH, RST, SYN, and FIN bits. SYN is a Synchronize Flag
When one computer A requests another computer B to establish a connection, a packet with the SYN flag set to 1 is transmitted from the computer A to the computer B.

When the TCP connection that is currently maintained is completed and the connection is closed, the amount of data buffered in the router 34 gradually decreases. When the amount of data has decreased to a predetermined amount, the router 3
4 transmits to the CM 41 a signal (hereinafter referred to as a restart signal) that allows the restart of the transmission of the new connection establishment request.

Upon receiving the restart signal, the CM 41 stops checking the SYN flag, and restarts packet classification and uplink priority transmission control according to the original QoS level.

Next, the operation of the router 34 will be described with reference to FIG. A flag FLG indicating whether or not the CM 41 is currently instructed not to transmit a request to establish a new connection is provided, and an initial value 0 is given (step S
31). The amount of frames retained in the internal buffer of the router 34 is regularly monitored and compared with a predetermined threshold value (step S32). When the amount of staying frames exceeds the threshold value, the router 34 broadcasts a suppression signal to all the CMs 41 under its control (step S34).
The flag FLG is changed to 1 (step S35). After that, while the amount of staying frames exceeds the threshold,
The loop consisting of steps S32 and S33 is repeated.

When the amount of staying frames decreases and falls below the threshold value, steps S32 to S32 are performed.
Head to 36. If the restart signal has not been sent yet after the inhibition signal is sent, the flag FLG is 1, so the router 34 broadcasts the restart signal to all CMs 41 under its control (step S37), and at the same time, the flag FLG. 0
To (step S38). While the flag FLG is 0, that is, while the CM 41 is allowed to transmit a request for establishing a new connection, steps S32 and S36 are repeated until the retained frame amount exceeds the threshold value.

Next, the operation of the CM 41 will be described with reference to FIG.

Upon receiving the upstream frame from the Ethernet interface (step S41), the CM 41 determines whether or not the router 34 is permitted to establish a new connection at that time. If the inhibition signal has not been received yet, or if the inhibition signal has not been received since the last restart signal was received, the CM 41 is permitted to transmit a new connection establishment request. On the other hand, when the inhibition signal is received but the corresponding restart signal is not received, the CM 41 is in a state in which the transmission of the new connection establishment request is not permitted.

If the transmission of the request for establishing a new connection is permitted, packet classification (step S43) is performed, and then BE and viewer response data are sent to the respective Qs.
Uplink transmission control according to the oS level is performed (step S
44).

On the other hand, if the transmission of the new connection establishment request is not permitted, the SYN flag of the upstream frame is checked (step S44). If the SYN flag is 1, it is a request to establish a new connection, and the frame is discarded (step S45). SY
If the N flag is 0, it means that the frame is related to the connection that has already been maintained. Therefore, the communication control as usual (steps S43 and S44) is performed.

Although the present invention has been described based on the embodiments, the present invention is not limited to this, and modifications and improvements can be made within the scope of ordinary knowledge of those skilled in the art. Of course.

For example, in the above embodiment, the CM 41
In the above, the upstream frames having the SYN flag of 1 are uniformly discarded, but instead of this, the frames may be retained / held in the CM 41. However, in this case, STB43 or P
Due to data retransmission from C42, a plurality of uplink frames with the SYN flag of 1 may stay in CM 41.
In this case, it is necessary to take into consideration that an end-to-end (End to End) sequence abnormality may occur between the STB 43 or PC 42 and the totaling server 11, which may rather reduce the communication efficiency.

Further, in the above-described embodiment, the router 34
An algorithm as shown in FIG. 3 has been shown as the processing in step 1. However, according to this algorithm, when the stay amount vibrates across the threshold value, there is a possibility that a lot of suppression / restart signals occur.
In order to avoid such a problem, the determination process may be performed with a hysteresis property, separately from the thresholds for the inhibition transmission and the restart transmission.

[0048]

According to the present invention, since establishment of a new TCP connection is suppressed, congestion can be prevented in advance. At the same time, the TCP connection that is currently maintained can be preferentially communicated.

Therefore, for example, in a service application such as a viewer participation program in which bursty traffic occurs, there is an effect of preventing network congestion. Moreover, by focusing on suppressing new TCP connections, established TCP connections can be preferentially communicated, and communication quality can be improved as compared with the uniform communication suppression method.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a CATV internet system 100 that is an embodiment of the present invention.

FIG. 2 is a diagram illustrating a format of a TCP header.

FIG. 3 is a flowchart for explaining the operation of the router 34.

FIG. 4 is a flowchart for explaining the operation of the CM 41.

[Explanation of symbols] 10 broadcasting stations 11 aggregation server 12 Program broadcasting equipment 20 satellite broadcasting network 30 CATV stations 31 Digital broadcasting equipment 32 Management server 33 Cable Modem Terminator (CMTS) 34 router 35 headend 40 subscriber's house 41 Cable Modem (CM) 42 Personal Computer (PC) 43 Set Top Box (STB) 44 Hub (HUB) 45 TV receiver (TV) 50 Management IP network

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 000005821             Matsushita Electric Industrial Co., Ltd             1006 Kadoma, Kadoma-shi, Osaka (71) Applicant 000005016             Pioneer Corporation             1-4-1 Meguro, Meguro-ku, Tokyo (71) Applicant 000102728             NTT DATA Corporation             3-3-3 Toyosu, Koto-ku, Tokyo (72) Inventor Yasumasa Tamura             2-31-25 Shiba, Minato-ku, Tokyo             -Cable Media Co., Ltd. (72) Inventor Yoshinori Rokugo             2-31-19 Shiba, Minato-ku, Tokyo Communications and broadcasting             Within the mechanism (72) Inventor Takeo Matsuura             2-31-19 Shiba, Minato-ku, Tokyo Communications and broadcasting             Within the mechanism (72) Inventor Kazushi Tahara             2-31-19 Shiba, Minato-ku, Tokyo Communications and broadcasting             Within the mechanism (72) Inventor Hiroshi Nakamoto             2-31-19 Shiba, Minato-ku, Tokyo Communications and broadcasting             Within the mechanism (72) Inventor Kenji Yashiro             Pies, 4-15-5 Omorinishi, Ota-ku, Tokyo             Onia Co., Ltd. (72) Inventor Katsuro Osawa             2-31-25 Shiba, Minato-ku, Tokyo             -Cable Media Co., Ltd. F term (reference) 5C064 BA01 BB04 BC06 BC14 BC16                       BD02 BD05 BD08 BD09 BD11                 5K030 GA13 HA08 LB19 LC09 LC11                       MB15

Claims (21)

[Claims] 1. A method of managing a connection established via first and second network devices, wherein said first network device is said to said second network device according to the usage status of network resources. Whether the step 1 of transmitting a predetermined signal A and the signal B requesting the establishment of a new connection are included in the signals transmitted from the second network device to the first network device. Step 2 in which the second network device refers to
And a step 3 in which, when the signal B is detected in the step 2, the second network device discards a predetermined unit of data including the signal B, the connection management method. 2. The connection management method according to claim 1, further comprising, following step 3, the first network device in advance with respect to the second network device in accordance with the usage status of network resources. A connection management method comprising: a step 4 of transmitting a predetermined signal and a step 5 of stopping the data discarding of the step 3 by the second network device according to the signal B. 3. The connection management method according to claim 1, wherein the first network device compares the amount of data retained inside with a predetermined threshold value, and A connection management method characterized by determining the usage status of a resource. 4. The connection management method according to claim 3, wherein different thresholds are applied in the step 1 and the step 4. 5. The connection management method according to claim 1, wherein the second network device retains data instead of discarding the data in step 3. . 6. The connection management method according to claim 1, wherein the first network device is a router and the second network device is a cable modem. Method. 7. A method for suppressing congestion in a communication system that performs communication using TCP / IP protocol, wherein TCP is used according to the usage status of network resources.
(Transmission Control Pro
tocol) A congestion suppressing method characterized by discarding a frame in which the control flag SYN of the header is 1. 8. A program for controlling the operation of a router, according to the amount of traffic in one direction, transmitting a signal A for instructing discard of a request for establishment of a new connection to the downstream of the traffic. A program characterized by being executed by a router. 9. The program according to claim 8, wherein
Further, according to the amount of the traffic, the program causes the router to execute a process of transmitting a signal "instruction to stop discarding the establishment request" to the downstream of the traffic. 10. The program according to claim 8, wherein the amount of data accumulated in the router is compared with a predetermined threshold value, and the signal A and A are transmitted according to the comparison result. A program for causing a router to execute a process of determining whether or not to perform. 11. The program according to claim 10, wherein a threshold for determining the transmission of the signal A and a threshold for determining the transmission of the signal A are different from each other. 12. The program according to any one of claims 8 to 11, wherein a cable modem is connected downstream of the traffic, and the signal A and B are transmitted to the cable modem. 13. A machine-readable recording medium in which the program according to any one of claims 8 to 12 is recorded. 14. A router which stores the recording medium according to claim 13 and operates according to the program. 15. A program for controlling the operation of a cable modem, when receiving a signal A according to the usage status of network resources, requests the establishment of a new connection by referring to the signal transmitted to the network. A program for causing a cable modem to execute a process 1 for detecting the presence or absence of a signal B, and a process 2 for detecting a signal B and discarding a predetermined unit of data including the signal B. 16. The program according to claim 15, further comprising causing a cable modem to execute a process of stopping the process 2 when receiving a signal according to a use status of network resources. 17. The program according to claim 15, wherein the cable modem executes a process of storing the data instead of discarding the data in the process 2. 18. A machine-readable recording medium on which the program according to claim 15 is recorded. 19. A cable modem that stores the recording medium according to claim 18 and operates according to the program. 20. A network system comprising the router according to claim 14 and the cable modem according to claim 19. 21. The network system according to claim 20, wherein a terminal device connected to the cable modem, an IP network connected to the router, and an IP network connected to the terminal device collects data from the terminal device. A network system further comprising: