KR20040001255A - Method for processing broadcast Frame for preventing Private Dynamic Host Configuration Protocol Server from assign IP address - Google Patents

Abstract

PURPOSE: A broadcasting frame processing method to interrupt IP allocation from a private DHCP(Dynamic Host Configuration Protocol) server is provided to process a broadcast frame in a switch or a DSLAM(Digital Subscriber Line Access Multiplexer) to prevent a private DHCP server from allocating an IP to a terminal requesting IP allocation. CONSTITUTION: If a frame is transmitted from a terminal(S30), a DSLAM checks whether the received frame is a broadcast frame(S32). In case that the received frame is a broadcast frame, the DSLAM judges whether the type of the frame is 'IP'(S36). In case that it is judged that the frame has an appointed IP code value, the DSLAM judges whether the IP packet is a UDP packet(S38). If the IP packet is a UDP packet, the DSLAM judges whether the UDP port number is a specific number corresponding to a DHCP message(S40). If the UDP port number is the specific number, the DSLAM judges whether an appointed port exists(S42). If an appointed port exists, the DSLAM judges whether only one port is appointed and the port received the frame(S44). If only one appointed port exists and the port received the frame, the DSLAM discards the frame(S48).

Description

Method for processing broadcast Frame for preventing Private Dynamic Host Configuration Protocol Server from assign IP address}

The present invention relates to a broadcast frame processing method for blocking IP (Internet Protocol) assignment from a private Dynamic Host Configuration Protocol (DHCP) server, and more particularly, a private DHCP server provides an IP address to a terminal requesting IP assignment. A broadcast frame processing method in a switch or a digital subscriber line access multiplexer (DSLAM) for preventing allocation.

Among the IP allocation methods of the high speed internet access service currently being used, DHCP allocation method, a dynamic IP address allocation method, is used for more efficient IP address allocation to high speed internet access providers and subscribers. DHCP method is used among IP allocation methods in LAN environment.

In this method, the subscriber terminal automatically requests an IP when booting, and when this request message is sent to the internet access service provider or a normal router switch (hereinafter referred to as a normal DHCP server) in the company, the server assigns an IP address to the subscriber. The assigned IP is used to use normal network service.

However, since the first DHCP IP assignment request message from the subscriber is broadcast, it is not only a normal router switch but also another router switch (hereinafter referred to as a private DHCP server) operated on the subscriber side. When the delivered private DHCP server assigns a private IP to a normal subscriber, the subscriber terminal assigned the private IP cannot use normal network services such as Internet access.

Hereinafter, the prior art of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a network using a general DHCP IP allocation method, in which the router switch 10 shown in the figure shows a case in which all ports of a subscriber are set to one VLAN (wide area LAN).

Briefly describing the network configuration, a plurality of router switches 10 connected to the internet 20 to allocate a private IP to the subscriber side and perform a routing function and a switching function so that the subscriber terminal can access the Internet. DSLAMs 20 and 30 are connected, and a plurality of terminals (terminals 1, 2, 3, ...) are connected to the DSLAM 20, and the terminal 11 and terminal 12, which function as a private DHCP server, are connected to the DSLAM 30. Terminal 13, which is a network device functioning as a private DHCP server, is connected, and terminal 11-1 and terminal 11-2 are connected to hub 11 through hub 34, and terminal 13-1,... Terminal 13-n is connected. Here, instead of the DSLAMs 20 and 30, a switch for transmitting / receiving a Mac frame (Bridging function, Layer 2 function) may be installed.

Next, a process of normally assigning an IP to a terminal in the above-described structure will be described with reference to the message flowchart shown in FIG. 2.

If the terminals 1, 2, 3, 11, 12, and 13 transmit the DHCP discovery message, which is a message for searching for DHCP, the DHCP discovery message is a broadcast message, so the DSLAM (20, 30) is not the receiving port. This message is transmitted to the port and forwarded to the normal router switch 10 (S10).

Since the subscriber-side port of the router switch 10 is set to one VLAN, the DHCP discovery message transmitted from the terminals 1, 2, and 3 is transmitted to the DSLAM 30, and the terminal 11, 12, and 13 are transmitted from the terminal. The DHCP Discovery message is sent to the DSLAM 20. Since the DHCP discovery message is a broadcast frame, the DSLAM 20 and 30 transmit the message to all terminals except the receiving port.

Upon receiving the DHCP discovery message, the normal router switch 10 transmits a DHCP Offer message including an assignable IP to the terminals 1, 2 3, 11, 12, and 13 that have transmitted the DHCP discovery message (S12).

Accordingly, the terminals 1, 2, 3, 11, 12, and 13 receiving the DHCP Offer message transmit a DHCP Request message including an IP request to the router switch 10 in broadcast (S14), and the DHCP Request The normal router switch 10 receiving the message transmits a DHCP Ack message including an IP assignable to the terminals 1, 2, 3, 11, 12, and 13 (S16).

Terminals 1, 2, 3, 11, 12, and 13 that receive the DHCP Ack message can use IP as a service, thereby enabling network services such as Internet access.

In the case of the terminal 11 and the terminal 13, the terminal 11-1, 11-, which is a terminal connected with its own downlink in the network structure after being assigned an IP from the normal router switch 10, is itself a private DHCP server. 2, 13-1,... When the server is asked to assign an IP address from 13-n, it assigns a private IP address.

Accordingly, when the terminals 11-1 and 11-2 transmit a packet using the private IP to the terminal 11, the terminal 11 may change the packet to an IP (usually a public IP) assigned by the router switch and may use the network such as an Internet connection. To be.

Similarly, terminal 13-1,... When the 13-n transmits a packet using the private IP to the terminal 13, the terminal 13 converts the packet to an IP (usually a public IP) allocated from the normal DHCP 10 to use a network service such as an Internet connection.

Meanwhile, in the above-described scheme, terminals 11 and 13 are set as private DHCP servers, and 1 is a terminal connected to the upper layer in response to a DHCP IP allocation request from the upper link rather than its own down link in the network structure. If the private IPs are assigned to 2, 3, and 12, the terminals 1, 2, 3, and 12 cannot receive normal network services and are in a faulty state.

That is, before the terminal 1, 2, 3, 12 is assigned an IP from the private DHCP server (terminal 11, terminal 13) before the IP is allocated from the normal router switch 10, the terminal 1, 2, 3, 12 Since the assigned IP is not a public IP, normal network service cannot be obtained.

In the above scheme, the DSLAMs 20 and 30 perform a frame processing procedure as shown in FIG. 3. When receiving a predetermined frame from the port (S20), it is checked whether the corresponding frame is a broadcast frame (S22) and the corresponding frame is broadcasted. If it is a frame (YES in S22), the frame is transmitted to all ports except the receiving port, and if the frame is not a broadcast frame (NO in S22), the frame is transmitted to the corresponding port except the receiving port. In this case, the frame is a code indicating whether it is broadcast (FF: FF: FF: FF: FF: FF) or unicast.The destination address, the source address, the type or length of the frame ( Length) and frame information (Data).

As a result, a DHCP Discover message or a DHCP Request message is also sent to the private DHCP servers 11 and 13, so that the private DHCP servers 11 and 13 can allocate an IP before the normal router switch 10. Terminals assigned IP from the private DHCP servers 11 and 13 cannot normally use network services.

Accordingly, the present invention has been made in view of the above circumstances, and provides a frame processing method of a switch or DSLAM for blocking IP allocation from a private DHCP server in a network of a high-speed Internet access provider or a LAN environment network of a general office. Its purpose is.

1 is a configuration diagram of a network using a general DHCP IP allocation scheme.

2 is a message flow diagram in a network using a conventional DHCP IP allocation scheme.

3 is a flowchart for explaining a frame processing procedure in a network using a conventional DHCP IP allocation scheme.

4 is a flowchart for explaining a broadcast frame processing method for blocking IP allocation from a private DHCP server according to an embodiment of the present invention.

Broadcast frame processing method for blocking IP allocation from a private DHCP server according to an embodiment of the present invention for achieving the above object,

In the broadcast frame processing method in a device installed between a DHCP client (terminal) and a router switch to perform frame transmission between both devices,

Determining whether the frame is a broadcast frame when a frame is received from an arbitrary port;

It is determined whether the frame is a DHCP message, and if it is determined that the frame is a DHCP message, a second process of transmitting the DHCP message only to an uplink port may be performed.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail.

4 is a flowchart illustrating a broadcast frame processing method for blocking IP allocation from a private DHCP server according to an embodiment of the present invention.

If the frame transmitted from the terminal is received (S30), the DSLAM (20, 30) checks whether the frame is a broadcast frame (S32), if the frame is not a broadcast frame and transmits the frame to the corresponding port (S34) ).

However, as a result of the determination in step S32, if the frame is a broadcast frame, it is determined whether the frame type is 'IP' (S36), and it is determined that the frame type is designated as an IP code value, for example, '0800'. In operation S38, it is determined whether the IP packet is a UDP packet.

If the IP packet is determined to be a UDP packet as a result of the determination in step S38, it is determined whether the UDP port number is a specific number corresponding to a DHCP message (DHCP Discovery message or DHCP Request message), for example, '67'. Determine (S40).

If the determination result in step S40 is that the UDP port number is a specific number 67, it is determined whether there is a designated port (pre-designated uplink port) (S42). It is determined whether or not the corresponding designated port is a port that receives the frame (S44).

As a result of the determination in step S44, if the designated port is one but the port is not the port for receiving the frame or if the designated port is not one, the DSLAM 20 and 30 select the corresponding frame only through the designated port. Transmit, and do not transmit to the remaining ports (S46).

However, unlike the above case, if the determination result in step S44 is one designated port and the port that receives the frame is the designated port (Yes), the frame is discarded (S48).

The determination result in step S36 is that the frame type is not IP (No), the determination result in step S38 is that the IP packet is not UDP (no), or the determination result UDP port is specified in S40. If it is not the port 67 (No), or if there is no predetermined uplink port as a result of the determination in S42 (No), the DSLAM (20, 30) transmits the frame received in the step S30 to all ports ( S50).

According to the above-described procedure, even if the DHCP Discovery message transmitted from the terminals 1, 2, 3, 12 is transmitted to the DSLAM 30 by the normal router switch 10, the DSLAM 30 is a port on which the DHCP Discovery message is received. Since the same as the port designated as the uplink is discarded without transmitting the frame containing the DHCP Discovery message.

As a result, the frame is not transmitted to the private DHCP servers (terminals 11 and 13), thereby preventing the private DHCP servers (terminals 11 and 13) from allocating private IPs to terminals 1, 2, 3, and 12. You can do it.

According to the present invention as described above, when the terminal is assigned an IP from the router switch in order to use the network service, it is possible to prevent the occurrence of a failure by being assigned an IP from the private DHCP server, the quality of the Internet access service There is an effect that can be improved.

On the other hand, the present invention is not limited to the above-described embodiment, but can be modified and modified within the scope not departing from the gist of the present invention, such modifications and changes should be regarded as belonging to the following claims. will be.

Claims (4)

In the broadcast frame processing method in a device installed between a DHCP client (terminal) and a router switch to perform frame transmission between both devices, Determining whether the frame is a broadcast frame when a frame is received from an arbitrary port; Determining whether the frame is a DHCP message transmitted from the router switch when the frame is broadcast; and transmitting the DHCP message only to an uplink port when the frame is determined to be a DHCP message. Broadcast frame processing method for blocking IP assignment from a private DHCP server, characterized in that consisting of. The method of claim 1, The procedure of determining whether the frame is a DHCP message transmitted from the router switch in the second process; A first step of determining whether the type of the frame is IP; A second step of determining whether the IP packet is UDP if the frame type is IP; If the IP packet is UDP as a result of the determination, it is determined whether the UDP port is a specific port for the DHCP message, and if the UDP port matches the specific port as a result of the determination, determining the frame as a DHCP message. A broadcast frame processing method for blocking IP assignment from a private DHCP server. The method of claim 1, If it is determined that the DHCP message in the second process, the procedure for transmitting only to the uplink port; A fourth step of determining whether an uplink port exists; If the uplink port is at least one or the uplink port is one but the uplink port is not the same as the port that received the frame, the DHCP message is sent to the uplink port, and the uplink port is 1 And a fifth step of discarding the frame if the uplink is the same as the port receiving the frame. The method of claim 1, The DHCP message of the second step is a DHCP discovery message or a DHCP request message transmitted by the broadcast from the DHCP client, the broadcast frame processing method for blocking IP allocation from the private DHCP server.