JP2001177572A - Data communication system using catv network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent illegal access such as impersonated member that a subscriber being the user of a personal computer conducts communication by using an illegal IP address. SOLUTION: A data communication system using a CATV network is provided with a DHCP server 1 allocating the IP address, the Internet network 2 containing the DHCP server 1, head end modem 3 connected to the Internet network 2, a CATV network 4 connected to the head end modem 3, a cable modem 5 connected to the CATV network 4 and a personal computer(PC) 6 connected to the cable modem 5. The cable modem 5 is provided with a modem circuit 51 connected to the CATV network 4, a filter 52 making only the packet of the IP address pass through and a detection control circuit 53 detecting the IP address and controlling the filter 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system using a CATV network, and more particularly to a data communication system using a CATV network when a personal computer is connected to the Internet network via the CATV network to perform data communication. .

[0002]

2. Description of the Related Art As a prior art of a data communication system using a conventional CATV network, Japanese Patent Laid-Open Publication No.
There is a data communication system device, a connection terminal device and a server device. Referring to FIG. 2, a data communication system using a CATV network in the prior art is shown in FIG.
When the cable modem itself communicates as one client on the network, it is necessary to assign an identifier on the network also to the cable modem.
In this case, in order to connect one personal computer to the network and operate it, conventionally, two identifiers on the net were required for the cable modem and the personal computer, but one identifier is assigned. Only by allowing the cable modem and the personal computer to communicate as one client on the network, the identifier is prevented from being depleted.

[0003]

In a conventional data communication system using a CATV network, which is a prior art,
HCP (Dynamic Host Configur
Protocol obtained by the server
It is not possible to prevent unauthorized access such as impersonation in which a PC user (subscriber) communicates using an unauthorized IP address based on an (Internet Protocol) address or the like.

[0004]

A data communication system using a CATV network according to the present invention comprises: a DHCP server for allocating an IP address;
Receiving the IP address from the server,
A personal computer for performing data communication with the HCP server, an Internet network accommodating the DHCP server, a head-end modem interposed between the Internet network and the CATV network for performing data communication between the two networks, In a data communication system using a CATV network comprising a cable modem interposed between the CATV network and the personal computer and performing data communication between the two, based on the IP address obtained from the DHCP server, And preventing unauthorized access such as impersonation in which the personal computer user communicates using the unauthorized IP address.

In the data communication system using the CATV network according to the present invention, secondly, the cable modem passes only the packet of the IP address on a communication path between the DHCP server and the personal computer. A filter, and monitors the communication state between the DHCP server and the personal computer to detect the IP address assigned by the DHCP server so that only the packet of the IP address passes. This is a cable modem with a DHCP interlocking filter function including detection control means for controlling a filter.

Third, in the data communication system using the CATV network according to the present invention, the personal computer communicates with the DHCP server with a DHCP DISCOV.
Make an IP address acquisition request by ER message,
The DHCP server responds to the IP address acquisition request with D
By transmitting the IP address to the personal computer by returning the HCP OFFER message,
The personal computer obtains the IP address transmitted from the DHCP server by using the DHCP server.
The personal computer obtains its own IP address based on a series of sequences in which a DHCP REQUEST message is transmitted to the CP server, and the DHCP server returns a DHCP ACK message to the personal computer in response to the DHCP REQUEST message. I do.

[0007] In the data communication system using the CATV network according to the present invention, fourthly, the detection control means monitors the DHCP sequence by monitoring the series of operation sequences.
When the IP address is detected by an ACK message, the IP address is set in the filter, and the filter is controlled so that only the packet having the IP address passes.

Fifth, in the data communication system using the CATV network according to the present invention, the filter is controlled by the detection control means, and the source address of a packet transmitted from the personal computer to the DHCP server side is determined. Looking at the destination address of the packet sent from the DHCP server to the personal computer, filtering is performed so that the IP address other than the IP address acquired by the DHCP server cannot pass.

A data communication system using a CATV network according to the present invention is configured such that:
B.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a data communication system using a CATV network according to the present invention includes: a DHCP server 1 for allocating an IP address;
DHCP after receiving IP address assignment from server 1
A personal computer (PC) 6 as a subscriber terminal for performing data communication with the server 1, an Internet network 2 accommodating the DHCP server 1, and both networks interposed between the Internet network 2 and the CATV network 4. It comprises a head-end modem 3 for performing data communication between them, and a cable modem 5 interposed between the CATV network 4 and a personal computer (PC) 6 for performing data communication between them.

The cable modem 5 is connected to the CATV network 4 to perform data communication with a personal computer (PC) 6, and a cable between the modem circuit 51 and the personal computer (PC) 6. A filter 52 for passing only packets of the IP address assigned to the personal computer (PC) 6 by the DHCP server 1 via the communication path, and a DH
When the communication state between the CP server 1 and the personal computer (PC) 6 is monitored and the IP address assigned by the DHCP server 1 is detected, the filter 52 is controlled so that only the packet of the IP address is passed. And a detection control circuit 53.

Next, the operation will be described. In the configuration shown in FIG. 1, when connecting to the Internet network 2 via the CATV network 4, the head end modem 3 is provided on the CATV center side (DHCP server side), and the cable modem is provided on the personal computer (PC) 6 which is a terminal. 5 is required. A subscriber who is a user of the personal computer (PC) 6 can communicate with the DHCP server 1 by connecting the personal computer (PC) 6 to the cable modem 5.

[0013] The DHCP server 1 on the CATV center side
Change the IP address of the personal computer (PC) 6 to D
This is necessary for assignment by HCP.

In the cable modem 5, an internal detection control circuit 53 monitors the communication state between the DHCP server 1 and the personal computer (PC) 6, detects an IP address assigned by DHCP, and detects the detected IP address.
By setting the address in the internal filter 52, it is possible to control so that only the packet having the IP address passes through the filter 5, that is, the cable modem 5.

Next, a personal computer (PC) 6
Is DHCP ・ DISCOV for DHCP server 1
An IP address acquisition request is issued by the ER message. D
The HCP server 1 is a personal computer (PC)
6 receives an IP address acquisition request from DHCP
Return the FFER message and tell the IP address.

And a personal computer (PC)
6 transmits a DHCP REQUEST message to the DHCP server 1 in order to obtain the IP address, and sends a DHCP REQUEST message from the DHCP server 1 to the DHCP REQUEST message.
The IP address is formally obtained by the ACK message. This series of sequences is monitored by the detection control circuit 53 of the cable modem 5. The detection control circuit 53 detects an IP address that has been properly obtained from the DHCP / ACK message from the DHCP server 1 so that the filter 52 is applied by the detected IP address, that is, so that only the packet of the IP address passes. The filter 52 is controlled.

The filter 52 checks the source address of the packet sent from the personal computer (PC) 6 and the destination address of the packet sent from the DHCP server 1 to the personal computer (PC) 6. In the case of an IP address other than the IP obtained by the DHCP server 1, filtering is performed so that the IP address cannot be passed.

In the system configuration diagram of FIG. 1, it is apparent that the same operation is performed even when the Internet network 2 is configured by a HUB.

[0019]

According to the data communication system using the CATV network according to the present invention, the I
Based on the P address and the like, it is possible to prevent unauthorized access such as impersonation in which a subscriber who is a personal computer user communicates using an unauthorized IP address.

Further, even when the IP address of the personal computer is changed each time by the DHCP server, the filtering can be performed in conjunction with the DHCP server.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a data communication system using a CATV network according to an embodiment of the present invention.

FIG. 2 is a system configuration diagram showing a data communication system using a conventional CATV network.

[Explanation of symbols]

 Reference Signs List 1 DHCP server 2 Internet network 3 Headend modem 4 CATV network 5 Cable modem 6 Personal computer (PC) 51 Modem circuit 52 Filter 53 Detection control circuit

Claims (6)

[Claims] 1. DHC for allocating an IP address
P server, a personal computer that receives the IP address assignment from the DHCP server and performs data communication with the DHCP server,
An Internet network accommodating a server, a head-end modem interposed between the Internet network and the CATV network for data communication between the two networks, and an Internet network interposed between the CATV network and the personal computer and CAT composed of cable modems that perform data communication
In a data communication system using a V network, preventing unauthorized access such as impersonation in which the personal computer user communicates using the illegal IP address based on the IP address acquired from the DHCP server. A data communication system using a CATV network. 2. The wireless communication system according to claim 1, wherein the cable modem includes a filter that passes only the packet of the IP address on a communication path between the DHCP server and the personal computer, and further includes a filter between the DHCP server and the personal computer. Monitoring the communication status of the DHC
When the P server detects the IP address assigned, the cable modem has a DHCP interlocking filter function including a detection control means for controlling the filter so as to pass only the packet of the IP address. A data communication system using the CATV network according to claim 1. 3. The personal computer includes a DH.
A DHCP server issues an IP address acquisition request to the CP server using a DHCP DISCOVER message.
P server responds to IP address acquisition request with DHCP
By returning the FFER message, the personal computer transmits the IP address to the personal computer, and the personal computer transmits a DHCP REQUEST message to the DHCP server to obtain the IP address transmitted from the DHCP server. The personal computer acquires its own IP address based on a series of operation sequences in which the DHCP server returns a DHCP ACK message to the personal computer. A data communication system using the CATV network described in the above. 4. The detection control means sets the IP address in the filter when detecting the IP address in the DHCP ACK message by monitoring the series of operation sequences, and sets the IP address in the filter.
4. The CA according to claim 3, wherein the filter is controlled so as to pass only the packet of the address.
A data communication system using a TV network. 5. The filter is controlled by the detection control means, and the filter is transmitted from the personal computer to the D filter.
Look at the source address of the packet sent to the HCP server and the destination address of the packet sent from the DHCP server to the personal computer, and pass if the IP address is other than the IP obtained by the DHCP server. 3. The data communication system using a CATV network according to claim 2, wherein filtering is performed so as not to be performed. 6. The data communication system using a CATV network according to claim 1, wherein said Internet network is a hub.