SERVER AND CONNECTING DESTINATION SERVER SWITCH CONTROL METHOD

• US 20090248871A1
• Filed: 11/24/2008
• Published: 10/01/2009
• Est. Priority Date: 03/26/2008
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Sano, Takeshi, Takase, Masaaki
• Granted Patent: US 7,904,562 B2
• Time in Patent Office: Days
• US Class Current: 709/226
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/125 by balancing the load, e.g. traffic engineering
• CPC Class Codes: H04L 47/19 at layers above the network layer network arrangements for networked applications for scheduling or organising the servicing of application requests H04L67/60

Abstract

A connecting destination server switch control method for switching a server and the connecting destination of the server is provided, the method realizing a larger-scaled network system by distributing a load to each cache server, thus reducing the total load and dynamically modifying a logical network according to the load of each cache server even when there is a plurality of content servers that are content distributors. In a situation where cache servers whose management sources differ are connected in many steps, the total load caused by content acquisition can be reduced by modifying the content acquisition source server of a cache server for each piece of content.

Claims

1. A cache server for caching content of a content server according to a request from a client and distributing the content to the client, comprising:

a cache control unit for determining whether the load is overloaded by measuring a load of the cache server, the overload being caused by a load source cache server that is subordinated to the cache server caching content cached on the cache server and comparing a value of the load with a predetermined overload setting value, and for retrieving a connecting destination of the load source cache server from the content server or other cache servers,

selecting content to switch and content to be switched by another cache server or content server such that a total load after switching can become equal to or less than the overload setting value and generating connecting destination retrieve request information including information about each piece of selected content and

generating a request requesting the load source cache server to switch its connection to a connecting destination indicated by connecting destination information on the basis of the connecting destination information indicating a connecting destination retrieved from the content server or the cache server that has received the connecting destination retrieve request information via the content server or the cache server; and

a communication management unit for transferring information about a cache to the cache control unit.

2. The cache server according to claim 1, wherein

when a connecting destination connectability determination result indicating connectability of a connecting destination of the load source cache server cannot be useful, the result having been transmitted from the content server or the cache server that has received the connecting destination retrieve request information, the cache control unit transfers the connecting destination retrieve request information to another cache server subordinated to it via the communication management unit.

3. The cache server according to claim 2, wherein

when a connecting destination is selected according to connecting destination switch request information that is connecting destination information indicating a connecting destination retrieved from the content server or the cache server by the content server or the cache server, the cache control unit determines whether it can be used as the load source cache server on the basis of its load status, and, if it can be connected, returns its response to the content server or the cache server that is a transmitting source of the connecting destination switch request information.

4. The content server according to claim 1, comprising:

a communication management unit for receiving a connecting destination connectability determination result that is a response including whether it can be used as a connecting destination of the load source cache server from a cache server specified in one of claims 1 through 3 that is a destination to which the connecting destination retrieve request information is transferred; and

a cache control unit for generating information including the connecting destination connectability determination result of a switching destination cache server and a cache server subordinated to the switching destination cache server on the basis of the connecting destination connectability determination result, and transmitting it to a cache server to which the load source cache server is connected, wherein

the information is transmitted to a connecting destination cache server of the load source cache server by the communication management unit.

6. The cache server according to claim 3, wherein

the cache server determines its connectability on the basis of a load increase by switching the acquisition source of content cached by the load source cache server and on the basis of a load decrease by switching the load source cache server connected to the other cache server that is subordinated to the content server to a cache server to be cached.

5. A connecting destination server switch control method implemented in a content distribution network for content of a content server according to a request from a client, wherein

a cache server that caches content of the content server

measures a load of the cache server, the load being caused by a load source cache server subordinated to the cache server caching content cached by the cache server, and

transmits, by comparing the measured load with a predetermined value, connecting destination retrieve request information for making a request to search for a connecting destination of a load source cache server that is a source of the load to the content server when it is determined that the load is overloaded;

the content server

receives the connecting destination retrieve request information transmitted from the cache server and

transfers the received connecting destination retrieve request information to another cache server subordinated to the content server;

the other cache server

determines whether it can be used as a connecting destination of the load source cache server on the basis of its load by receiving the connecting destination retrieve request information transferred from the content server and

transmits, to the content server that has transmitted the connecting destination retrieve request information to it, a connecting destination connectability determination result indicating whether the determined connecting destination can be used;

the content server

transmits a notice including information about a switching destination cache server and a cache server subordinated to the switching destination cache server to a cache server to which the load source cache server is connected on the basis of the connecting destination connectability determination result; and

the cache server

communicates in order to modify connecting destinations of the cache server, the load source cache server subordinated to the cache server, the switch destination cache server, and a cache server to be switched that is subordinated to the switch destination cache server.

7. The connecting destination server switch control method according to claim 5, wherein

a request to switch its connection to a connecting destination indicated by connect request information retrieved from the content server or retrieved from the other cache server that has received the connecting destination retrieve request information via the content server or via the other cache server is generated on the basis of the connecting destination information and transmitted to a cache server to which the load source cache server is connected.

8. The connecting destination server switch control method according to claim 5, wherein

its connectability is determined on the basis of a load increase by switching the acquisition source of content cached by the load source cache server and on the basis of a load decrease by switching the load source cache server connected to the other cache server that is subordinated to the content server to a cache server to be cached.