KR100254771B1 - Address resolution method for the proxy based lan emulation client - Google Patents

Abstract

PURPOSE: A method for analyzing an address by a proxy LAN emulation client is provided to efficiently carry out address analysis procedures for an old Ethernet host and a terminal, in embodying an Ethernet and an ATM-LAN emulation bridge, based on a LAN emulation standardization method. CONSTITUTION: If a proxy LAN emulation client receives an address analysis request frame(41), the client searches a station cache table to check whether a requested destination MAC address exists(42). If the requested destination MAC address exists in the station cache table, the proxy LAN emulation client generates a response frame for requested address analysis and transmits it to a LAN emulation server(43). However, in case that the requested destination MAC address doesn't exist in the station cache table, the proxy LAN emulation client discards the address analysis request frame(44) and returns from the address analysis request processing routine(45).

Description

How to Resolve Addresses in Proxy LAN Emulation Clients

The present invention relates to an address resolution method of a proxy LAN emulation client for connecting an existing LAN to an asynchronous transmission mode (ATM).

In general, existing LANs have an address resolution protocol used between several devices connected to a LAN (hereinafter, referred to as a LAN), and are used to service existing LAN application software in an asynchronous transmission mode (hereinafter, referred to as ATM) network. The LAN emulation specification also specifies the address resolution protocol procedure between a LAN emulation server and a LAN emulation client.

However, the LAN emulation specification does not specifically address the address resolution procedure of the proxy LAN emulation client. It only mentions the function that broadcasts to all clients when the LAN emulation server fails to respond directly to the address resolution request, and forwards the response to the original requestor when receiving a response from any client.

Accordingly, the present invention implements an ATM-LAN LAN emulation bridge that transparently supports the application of Ethernet by interworking an Ethernet network, which is one of the representative existing LANs, based on the LAN emulation standardization scheme provided by the ATM forum. Therefore, an object of the present invention is to provide an address resolution method of a proxy LAN emulation client that can efficiently perform an address resolution procedure for an existing Ethernet host and terminal.

In order to achieve the above object, the present invention is characterized in that when the bridge LAN emulation client operates as a proxy client, an address resolution function is performed using a station cache necessary for performing a learning function of the bridge.

The present invention describes an address resolution method and procedure to be performed in a LAN emulation client function and enables efficient address resolution in practice.

The LAN emulation proxy interface is an optional feature and is only used when the LAN emulation client acts as a proxy client, such as a LAN emulation bridge or router. When acting as a proxy client, the LAN emulation client sets the Flags part of the subscription frame as the proxy flag during the joining of the LAN Emulation Server (LES) to control its own medium access. MAC address is not registered in the server, and indicates that it can provide a service by receiving an LE-ARP request for an unregistered MAC address.

For example, when a proxy LAN emulation client receives an address resolution request frame, if it cannot respond by checking the destination MAC address of the received frame, it discards the received frame. However, when the destination MAC address is a MAC address connected to its proxy client, a response frame including its ATM address is generated and transmitted to the LAN emulation server. Upon receiving this, the LAN emulation server sees the requested LAN emulation client identifier (LEC-ID) in the frame and forwards it to the corresponding LAN emulation client. The above address resolution procedure is a standardized procedure.

However, it does not mention the standardization of how the proxy client responds by distinguishing the existing LAN host and the terminal connected to it. This may be because the configuration of the existing LAN connected to the proxy client may vary. Accordingly, the present invention provides some efficient solutions to the problems associated with address resolution procedures when operating as a bridge LAN emulation client that connects an existing LAN to an ATM. Bridge LAN emulation There are three main types of LAN connections to clients.

The first is when one end system is connected. At initialization, one MAC address and one ATM address are entered into the LAN emulation server's address resolution table.

The second is a case where a few end systems are connected. The MAC and ATM addresses of all connected end systems are registered on the server by using one or more MACs. In this case too, the LAN emulation server performs a response service for address resolution. However, if there is a change in the connected end system, there may be the trouble of removing from the previous registration or registering again.

The third is when Ethernet segments are connected directly or when multiple end systems are connected. When connected to the Ethernet segment, how many terminals and host devices are actually connected to the segment, and there is no way to actually know all the MAC addresses of the connected devices at the MAC level. Therefore, it is also impossible to register each MAC address.

In this way, the LAN emulation client has to perform bridge function and address resolution for unregistered MAC when multiple end systems interwork with each other by LAN emulation. . In order to perform this address resolution function, a station cache constructed when the bridge function is performed is used. The station cache stores the source MAC address of each Ethernet port and the port from which LAN emulation data is received for a period of time, and compares it with the destination MAC address of the data coming from each port to determine the output port. This can be used as a means of reducing the data traffic broadcast. In any case, the bridge LAN emulation client maintains these station caches, so when receiving a LAN emulation address resolution request frame, it searches the station cache for each Ethernet port and responds to the destination MAC address contained in the received address resolution request frame if it exists. Will be sent to the server. It works as a proxy LAN emulation client to support the address resolution process. By using the station cache of the Ethernet port, the configuration of the end systems connected to the proxy LAN emulation client can be less affected. This is because the station cache performs an aging function that is deleted from the cache when there is no re-entry for a certain time after being entered once. If the connected end system does not exist in the station cache, it cannot respond to the address resolution request. This is not a problem, because LAN emulation performs a BUS (Broadcasting and Unknown Server) function to handle broadcasting data and data with unknown destination addresses. If an Ethernet packet, such as a response to the end system, is forwarded to the end system, and then forwarded to the reverse system, the MAC address of the source is stored in the Ethernet station cache so that the function of responding to the address resolution request can be performed thereafter.

1 is a configuration diagram of a LAN emulation apparatus to which the present invention is applied.

2 is a schematic diagram of a LAN emulation protocol stack to which the present invention is applied.

3 is a structure diagram of an address resolution protocol to which the present invention is applied.

4 is a process flow diagram at the time of receiving an address resolution request frame according to the present invention;

5 is a flowchart of a station cache update procedure in accordance with the present invention.

6 is a flowchart of a station cache aging procedure in accordance with the present invention.

7 is a diagram illustrating an internal configuration of a station cache according to the present invention.

<Explanation of symbols for main parts of drawing>

11, 12: Ethernet interface 13: Bridge function

14: LAN Emulation Function 15: ATM Adaptation Layer

16, 17: Traditional Ethernet interface 18: ATM interface

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

FIG. 1 is a schematic functional diagram of a LAN emulation apparatus to which the present invention is applied, and includes Ethernet interfaces 11 and 12 and Ethernet interfaces 11 and 12 that connect the existing Ethernet interfaces 16 and 17. 12, a bridge function processing unit 13 connected to perform a bridge function, a LAN emulation function block 14 connected to the bridge function processing unit 13 to process a LAN emulation protocol, a LAN emulation function block 14, and An ATM adaptation layer processing unit (AAL5) 15 connected between the ATM interfaces 18 is provided.

2 illustrates a LAN emulation protocol stack structure to which the present invention is applied.

The present invention corresponds to a bridge ATM-LAN emulation client that performs an ATM-LAN conversion function for connecting an existing LAN to an ATM among various operating forms of LAN emulation. To this end, one side must be connected to the ATM 28 and the other side must be connected to an Ethernet host 29 capable of connecting an existing LAN. To connect to the ATM 28, the physical layer 21, the ATM layer 22 as the upper layer of the physical layer 21, the ATM adaptation layer type 5 (AAL5) 23 as the upper layer of the ATM layer 22, AAL LAN emulation function 24 is performed on the fifth layer 23.

For the Ethernet 29 connection, the protocol of the MAC layer 26 is performed on the physical layer 27 and the physical layer 27 that performs the physical connection function of the Ethernet, and the bridge function 25 is performed on the MAC layer 26. Perform. The bridge function 25 performs a connection function between Ethernet or between ATM and Ethernet.

In the present invention, an address translation function of a LAN emulation is to be performed using a station cache for each port managed to perform a bridge function.

3 is a structural diagram of an address resolution protocol of LAN emulation according to the present invention. Address resolution is a process by which the LAN emulation clients 31 and 33 obtain the destination ATM address from the destination MAC address. This address resolution request is made from the LAN emulation client 31 to the LAN emulation server 32, and the response is mostly made by the LAN emulation server 32 with the address resolution response 35.

However, if the requested MAC address does not exist in the server's address resolution table, it broadcasts the address resolution request 36 frame received to all clients through a distributed connection. When the client 33 receives the address resolution request, the client 33 sends an address translation response 37 frame to the LAN emulation server 32 when it needs to respond. The received LAN emulation server 32 receives the original requesting client ( 31) to complete the address resolution process. This describes the standardized address resolution process.

4 is a flowchart of a receiving process of an address resolution request frame according to the present invention. A process of substantially performing the content described in FIG. 3 is shown. First, when an address resolution request frame is received (41), a search is made for each port whether a destination MAC address requested in the station cache table of a bridge managed by the user exists (42). If there is a search result, a response frame for the requested address resolution is generated and transmitted to the server (43). Send your ATM address. If not present, the received address resolution request frame is discarded (44) and returned from the address resolution request processing routine (45).

5 is a flowchart of a station cache update procedure according to the present invention. Station caches are managed on a per port basis, and target ports include Ethernet ports and ports through which LAN emulation data is received via AAL 5. First, when an Ethernet packet or LAN emulation data is received (51), the station cache of the corresponding port is checked to see if the source MAC address already exists. If it already exists, only the aging time variable of the cache is initialized to 0 (54) and then returned. If not present, the source MAC address is added to the station cache table of the corresponding port (53), the aging time variable is initialized to a value of zero (54), and then returned (55).

6 is a flowchart of a station cache aging procedure according to the present invention. Station cache aging is performed periodically (61) and checks the station cache of the port to see if a source MAC address already exists (62). If it already exists, the aging variable of all cache information is increased by 1 at regular intervals (63) and if the increased aging time is greater than the maximum allowed time (64), then the source MAC address is deleted from the station cache (65). If the increased aging time is less than the maximum allowable time, the process 62 is repeated to search for the existence of the source MAC address. If there is no more cache to process in step 62 of searching for the existence of the source MAC address, it returns from the station cache aging procedure (66).

7 is an internal configuration diagram of a station cache according to the present invention. The internal configuration of the station cache 72 is managed for each port (71), and configured in a linked list structure to dynamically use the memory. Inside each station cache is a source MAC address, an aging time variable, and a pointer to the following: If the point is blank, it indicates that there is no longer valid information. This is the case of configuring the cache in software with memory. Another alternative is to use a hardware device such as CAM (Content Address Memory).

As described above, when the bridge LAN emulation client operates as a proxy client, the bridge cache is used to efficiently perform address resolution without managing an additional address table or additional functions.

In addition, since the cache of the Ethernet port is used, the configuration of end systems connected to the proxy LAN emulation client may not be affected. This is because the station cache performs an aging function that is deleted from the cache when there is no re-entry for a certain time after being entered once. If you don't age, you might get a wrong response. In addition, when multiple ATM terminals are connected to a LAN emulation client, only the MAC address of the end system being used is cached and used for address resolution, so that the retrieval speed is faster and less cache memory is required. In a similar application, the algorithm of the present invention can be applied.

Claims (5)

When the bridge LAN emulation client operates as a proxy client, address resolution is performed using the station cache necessary for performing the learning function of the bridge. The method of claim 1, wherein the address resolution method using the station cache comprises: searching for each port whether a destination medium access control address exists in the station cache table of a bridge managed by the bridge after receiving an address resolution request frame; , If the search result is present, generating a response frame for the requested address resolution, transmitting the same to the server, discarding the received address resolution request frame, and returning from the address resolution request processing routine; If the search result does not exist, immediately discarding the received address resolution request frame and returning from the address resolution request processing routine. The method of claim 1, wherein the updating of the station cache comprises: receiving an Ethernet packet or LAN emulation data, examining the station cache of the corresponding port in the station cache table to detect whether a source medium access control address already exists; Adding a source medium access control address to the station cache table of the corresponding port if present according to the search result, initializing only the aging time variable of the corresponding cache to 0, and returning from the station cache update processing routine; And if the search result does not exist, immediately resetting the aging time variable to a value of 0 and returning from the station cache update processing routine. The method of claim 1, wherein the station cache aging procedure periodically performs a station cache aging function, and then checks a station cache of a corresponding port to detect whether a source medium access control address already exists; Searching for whether the increased aging time is greater than the maximum allowable time by increasing an aging variable of all cache information by a predetermined time period if the search result already exists; If the search result is larger than the maximum allowable time, the source medium access control address is deleted from the station cache and the aging function is performed again. If the search result is less than the maximum allowable time, the aging function is immediately performed. And returning from the station cache aging processing routine if the source medium access control address does not exist. 2. The proxy LAN of claim 1, wherein the station cache comprises a source medium access control address, an aging time variable, and a pointer to the next content, indicating that there is no valid information when the pointer is blank. How to interpret the address of the emulation client.

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