Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-04-21
2003-06-03
Nguyen, Steven (Department: 2665)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S466000, C709S241000
Reexamination Certificate
active
06574229
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a wide area load distribution apparatus and method for allocating services provided to clients by a plurality of servers, depending on the states of load of the servers, and more particularly to a wide area load distribution apparatus and method in which the servers belonging to different networks are subjected to load distribution.
2. Description of the Related Arts
A recent rapid prevalence of internet and intranet is increasing a demand for effective utilization of servers providing network services and for service stability. An optimum service allocation for avoiding any access concentration to a specific server is indispensable for the effective utilization of the servers and stable service provision, so that a load distribution method for allocating the services depending on the state of load of the servers is desired.
Hitherto known as the load distribution method for performing service allocation depending on the server load state are a method utilizing a domain name system (hereinafter, referred to as DNS) and a method utilizing an virtual server. The method utilizing DNS is a method in which a plurality of DNSs are arranged in each network area in a distributed manner and in which an optimum server IP address is correlated with a domain name for each network area. Each DNS allows a single domain name to be correlated with a plurality of IP addresses so that a round robin selects an IP address for the transfer to the client. More specifically, when a client sends a domain name, e.g., “www, flab, fujitsu, co jp” to a DNS arranged in an area to which the client belongs, the DNS which has received the domain name makes an access to a most significant first layer DNS lying outside the area, then to a DNS of each layer, i.e., from the first layer to a second layer, from the second layer to a third layer, and further from the third layer to a fourth layer. The client acquires a server IP address from the fourth layer DNS for sending. This IP address from the fourth layer DNS is cached by the DNS of the network to which the client belongs. When the same domain name is then received from another client, an IP address response is issued due to the cache hit. In the method utilizing the virtual server, a virtual server is disposed in front of a plurality of servers so that all the accesses from the clients pass through the virtual server, which allocates and relays service demands from the clients in ratios depending on the state of load of the servers. Known as this virtual server method is for example “UXP/DS InfoDispatcher” supplied by Fujitsu Ltd.
A load distribution mechanism for use in the method utilizing the virtual server is described in for example
I) “4T-01 Smart Scatter: Internet/Intranet Load Distribution Mechanism—General Configuration and Control Part—” 55th Information Processing National Conference Trans. 1997, by Satoru HOSOI, Eiichi TAKAHASHI, Takuya YAMADA, Koichi TAKABASHI, Motomitsu ADACHI; and
II) “4T-2 Smart Scatter: Internet/Intranet Load Distribution Mechanism—Packet Allocation Part—” 55th Information Processing National Conference Trans. 1997, by Yuji IMAI, Hiromitsu KISHIMOTO, Koichi TAKABASHI, Tsunehiko YAHAGI.
In the conventional load distribution method utilizing the DNS, however, among the externally provided first to fourth layer DNSs the fourth layer DNS manages the IP addresses of a plurality of servers for the domain name, so that if a response of only one IP address among them is made, this is cached in the DNS associated with the client. This allows the accesses to be concentrated to one server cached in the DNS, preventing the load distribution. Furthermore, the clients are fixed on an area to area basis, so that there must be estimated the number of clients in order to provide sufficient services. In the load distribution method utilizing the virtual server on the other hand, there are found no measures for the cases where all the servers to be subjected to the load distribution are in high load or at a stop. Furthermore, accordingly as the network scale becomes larger, the number of the servers to be subjected to the load distribution will increase, with the result that the accuracy of the load measurement of the servers belonging to the other network remote from the load distribution apparatus may lower. Thus, the load distribution apparatus itself may possibly become a bottleneck, preventing an appropriate load distribution, and imposing a restriction on the servers to be subjected to the load distribution.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a wide area load distribution apparatus and method ensuring a proper load distribution and failure concealment among servers belonging to different networks.
The present invention provides a wide area load distribution apparatus which allocates services provided to clients by a plurality of servers existing in the different networks, depending on the state of load of the servers. The wide area load distribution apparatus comprises a transfer transmission unit, a transfer reception unit, a server allocation unit, a server transfer unit, a client relay unit, a connection management unit and a load information management unit.
The server allocation unit allocates a service for a client packet from a client to a server of its own network or a server of the other network which is selected on the basis of load information.
The transfer transmission unit creates a transfer packet containing the client packet in the form of transfer data when the server allocation unit allocates the service to the server of the other network, to transfer the transfer packet by a predetermined transfer protocol to a wide area load distribution apparatus of the other network.
The transfer reception unit fetches the client packet from the transfer packet when the transfer packet is received from a wide area load distribution apparatus of said the other network. The server transfer unit converts the destination of the client packet fetched by the transfer reception unit from a transferor wide area load distribution apparatus address to a server address and converts the sender from a client address to a self address for sending the packet to the server.
The client relay unit converts the destination of a server packet which is a response to a transferred service from a server, from a self address to a client address and converts the sender from a server address to a transferor wide area load distribution apparatus address for relaying the packet to the client.
Furthermore, the connection management unit holds for each service a correlation for retrieval among a client, a transferee and a server for a packet processed by the server allocation unit, the transfer transmission unit, the transfer reception unit, the server transfer unit and the client transfer unit.
Such a wide area load distribution apparatus enables the servers belonging to different networks to be subjected to load distribution without impairing the service consistency, with the result that the sites of arrangement of the servers to be subjected to the load distribution can freely be determined.
Furthermore, the protocol for use in the transfer can freely be determined, so that it becomes possible to enhance the flexibility and efficiency including the addition of additional information to the transfer packet and continuous establishment of connection for the transfer.
According to a second aspect of the present invention, there is solved a problem that the service may possibly be excluded by a security device for checking incorrect addresses since the sender address of the response packet to the client from the wide area load distribution apparatus is Lx, instead of a correct sender address Ly.
The wide area load distribution apparatus comprises a transfer transmission unit, a transfer reception unit, a server allocation unit, a server transfer unit, a client relay unit, a connection management unit and a
Aoki Takeshi
Kikuchi Shinji
Okano Tetsuya
Takahashi Eiichi
Fujitsu Limited
Nguyen Steven
Staas & Halsey , LLP
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