Communication system, relay apparatus, end system, and communicating method

• US 20010046212A1
• Filed: 01/16/2001
• Published: 11/29/2001
• Est. Priority Date: 05/26/2000
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakajima, Masaki
• Granted Patent: US 6,856,593 B2
• Time in Patent Office: Days
• US Class Current: 370/278
• CPC Class Codes: H04L 43/0811 by checking connectivity
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/28 using route fault recovery

Abstract

In a relay apparatus, when an error of the next relay destination is detected at the time of reception of a connection establishment request, the connection establishment request is refused by a connection negative response unit and a negative response relay unit, and a negative response is transmitted to a relay source. When the negative response is received from the relay destination, a connection establishment requesting unit of an end system of a communicating source again issues a connection establishment request in which another relay destination has been selected without notifying an application of a failure of the connection establishment, and establishes a connection to a communicating destination end system by another path.

Claims

1. A communication system for establishing a connection via a plurality of relay apparatuses between an end system of a communicating source and an end system of a communicating destination and communicating data, wherein

each of said relay apparatuses comprises:

a connection negative response unit which, when an error of a next relay destination is detected at the time of reception of a connection establishment request, refuses the connection establishment request and transmits a negative response to a relay source; and

a negative response relay unit which, when said negative response is received from the relay destination, transmits the received negative response to the relay source, and

said end system of the communicating source has a connection establishment requesting unit which, when said negative response is received from the relay destination after said connection establishment request is transmitted, issues again the connection establishment request in which another relay destination has been selected without notifying an application of a failure of the connection establishment and establishes a connection to the communicating destination end system by another path.

2. A system according to

claim 1

, wherein said end system of the communicating source has a plurality of relay apparatuses as a plurality of relay destinations, and in the case where the negative response is received after a specific relay apparatus is selected and the connection establishment request is transmitted, said communicating source end system selects another relay apparatus and retransmits the connection establishment request.

3. A system according to

claim 1

, wherein said end system of the communicating source has a plurality of relay adapters provided for one relay apparatus as a plurality of relay destinations, and in the case where the negative response is received after a specific relay adapter is selected and the connection establishment request is transmitted, said communicating source end system selects another relay adapter and retransmits the connection establishment request.

4. A system according to

claim 1

, wherein said relay apparatus has a relay selecting unit which, when said negative response is received from the relay destination after said connection establishment request is relayed, issues again the connection establishment request in which another relay destination has been selected and establishes a connection to said communicating destination end system by another path.

5. A system according to

claim 4

, wherein said relay apparatus has a plurality of relay apparatuses as a plurality of relay destinations, and in the case where the negative response is received after a specific relay apparatus is selected and the connection establishment request is transmitted, said relay apparatus selects another relay apparatus and retransmits the connection establishment request.

6. A system according to

claim 4

, wherein said relay apparatus has a plurality of relay adapters provided for one relay apparatus as a plurality of relay destinations, and in the case where the negative response is received after a specific relay adapter is selected and the connection establishment request is transmitted, said relay apparatus selects another relay adapter and retransmits the connection establishment request.

7. A system according to

claim 1

, wherein each of said end system and said relay apparatuses switches a communication path by 4-layer switches for establishing a TCP connection.

8. A system according to

claim 1

, wherein:

said negative response relay unit of said relay apparatus stores refusal reasons and location information of a fault occurrence relay apparatus into an optional area or a user data area of a negative response packet and transmits them to the relay source; and

when said negative response packet is received, said connection establishment requesting unit of said communicating source end system changes a status of the relay destination in which a fault path occurred to an unusable state and, thereafter, selects another relay destination and retransmits the connection establishment request.

9. A system according to

claim 8

, wherein the location information of the abnormal relay apparatus which is stored in said negative response packet is an IP address of an abnormal relay apparatus and the number of hopping times indicative of the number of normal relay apparatuses to the abnormal relay apparatus.

10. A system according to

claim 8

, wherein said negative response relay unit of said relay apparatus further stores a self IP address into the optional area or user data area of said negative response packet and transmits it to the relay source.

11. A relay apparatus for establishing a connection between an end system of a communicating source and an end system of a communicating destination and communicating data, comprising:

a connection negative response unit which, when an error of a relay destination is detected at the time of reception of a connection establishment request, refuses the connection establishment request and transmits a negative response to a relay source; and

a negative response relay unit which, when said negative response is received from the relay destination, transmits the received negative response to the relay source.

12. An apparatus according to

claim 11

, wherein said negative response relay unit stores refusal reasons, an IP address of an abnormal relay apparatus indicative of a location of a fault occurrence relay apparatus, and the number of hopping times indicative of the number of normal relay apparatuses to the abnormal relay apparatus into an optional area or a user data area of a negative response packet and transmits them to the relay source.

13. An end system for establishing a connection via a plurality of relay apparatuses and communicating data, comprising:

an application which issues a communicating request by setting a specific end system to a partner destination; and

a connection establishment requesting unit which, when a negative response is received from a relay destination after a connection establishment request based on said communicating request is transmitted, issues again a connection establishment request in which another relay destination has been selected without notifying said application of a failure of the connection establishment and establishes a connection to a communicating destination end system by another path.

14. A system according to

claim 13

, wherein when a negative response packet is received, said connection establishment requesting unit changes a status of the relay destination in which a fault path occurred to an unusable state and, thereafter, selects another relay destination and retransmits the connection establishment request.

15. A communicating method of establishing a connection via a plurality of relay apparatuses between an end system of a communicating source and an end system of a communicating destination and communicating data, comprising the steps of:

when an error of a next relay destination is detected in one of said relay apparatuses at the time of reception of a connection establishment request, refusing the connection establishment request and transmitting a negative response to a relay source; and

when the relay apparatus receives said negative response from a relay destination, transmitting the received negative response to the relay source from said relay apparatus,

wherein when said negative response is received from the relay destination after said connection establishment request is transmitted, said end system of the communicating source issues again the connection establishment request in which another relay destination has been selected without notifying an application of a failure of the connection establishment and establishes a connection to the communicating destination end system by another path.