Loop locating apparatus and loop locating method in layer 3 network

Abstract

A loop locating apparatus and method enabling simple and fast identification of a Layer 3 loop fault occurring in a network, wherein, when the possibility of a Layer 3 loop is detected, a loop locating command function unit makes a packet transmission/reception function unit send a series of inspection packets (Pis) with successively incremented TTLs and monitors the return packets (te) of the inspection packets (Pis) by a return number counting function unit and wherein a loop location decision function unit finds the routers returning packets (te) with remarkably larger return numbers than the others and identifies the routers with return numbers over a predetermined threshold as the location of occurrence of the loop.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein:

FIG. 1 is a view of the basic configuration of the present invention;

FIG. 2 is a view of a more specific example of the basic configuration of FIG. 1;

FIG. 3 is a view of an example of a communication confirmation process triggering loop detection;

FIG. 4 is another view of an example of a communication confirmation process triggering loop detection;

FIG. 5 is a view of the relationship between inspection packets and return packets in the present invention;

FIG. 6 is a view of the content of a table 42 relating to FIG. 2;

FIG. 7 is a flow chart of the basic steps of a method of locating a loop according to the present invention;

FIG. 8 is a first part of a flow chart of an example of the specific steps based on FIG. 7;

FIG. 9 is a second part of a flow chart of an example of the specific steps based on FIG. 7;

FIG. 10 is a first part of a view of the format of an ICMP “time exceeded” packet;

FIG. 11 is a second part of a view of the format of an ICMP “time exceeded” packet;

FIG. 12 is a view of a first example of a multicast ping of an inspection packet in FIG. 5;

FIG. 13 is a view of the format of a multicast ping;

FIG. 14 is a view of a second example of using the inspection packet in FIG. 5 as an RTCP packet;

FIG. 15 is a view of the format of an RTCP packet;

FIG. 16 is a view of the state of occurrence of a Layer 3 loop fault; and

FIG. 17 is a view illustrating that a multicast route and a unicast route are sometimes different.

Claims

1. A loop locating apparatus for identifying the location of a Layer 3 loop occurring in a Layer 3 network including a plurality of routers, provided with: a loop location command function unit for commanding the identification of the location of occurrence of the Layer 3 loop,a packet transmission/reception function unit for transmitting at least a series of inspection packets for identification of the location of occurrence of said Layer 3 loop or receiving input packets from said Layer 3 network,a return number counting function unit for cumulatively counting the return number of said input packets corresponding to said inspection packets for each of the plurality of routers, anda loop location decision function unit for referring to the cumulative return number for each router counted by said return number counting function unit, confirming that said Layer 3 loop has occurred, and identifying the routers of the location of occurrence.

2. A loop locating apparatus as set forth in claim 1, wherein said loop location command function unit sends communication confirmation packets to a predetermined plurality of receiving terminals at substantially periodic intervals for confirmation of communication and issues a command to said packet transmission/reception unit to send said series of inspection packets when judging from the return packets that said Layer 3 loop may have occurred.

3. A loop locating apparatus as set forth in claim 2, wherein said communication confirmation packets are multicast pings (Packet InterNet Groper).

4. A loop locating apparatus as set forth in claim 2, wherein said communication confirmation packets are RTCP (Real-time Transport Control Protocol) packets.

5. A loop locating apparatus as set forth in claim 1, wherein said loop location command function unit issues a command to said packet transmission/reception unit to send said series of inspection packets when judging from return packets returned during transmission of stream data packets originally to be transferred that said Layer 3 loop may have occurred.

6. A loop locating apparatus as set forth in claim 1, wherein said series of inspection packets transmitted from said packet transmission/reception function unit are IP (Internet Protocol) packets with successively incremented TTL (Time to Live) settings and said input packets received by said packet transmission/reception function unit are a series of ICMP (Internet Control Message Protocol) “time exceeded” packets corresponding to the series of IP packets.

7. A loop locating apparatus as set forth in claim 6, wherein said inspection packets are multicast pings or RTCP (Real time Transport Control Protocol) packets.

8. A loop locating apparatus as set forth in claim 6, wherein the values of TTL in the IP packets are set to 1 to K (K is an integer of 2 to less than 256) as default values or are set to incremental values expressed by X+N, where X is any fixed integer, N is an integer incremented one by one, and X+N is an integer less than 256.

9. A loop locating apparatus as set forth in claim 6, wherein said packet transmission/reception function unit successively transfers the series of input packets Pin successively received to the return number counting function unit.

10. A loop locating apparatus as set forth in claim 6, wherein said packet transmission/reception function unit notifies said loop location decision function unit to start the loop location decision operation when finishing receiving the series of input packets.

11. A loop locating apparatus as set forth in claim 9, wherein the return number counting function unit includes a searching unit for analyzing the input packets successively transferred from the packet transmission/reception function unit to find the source address of the source sending the ICMP “time exceeded” packet forming each input packet from the source address contained in the same and a table for entering the source addresses found and cumulatively counting up the return number for each router on the table.

12. A loop locating apparatus as set forth in claim 11, wherein when the source address found by the searching unit is not in the table, the source address is newly entered into the table, while when the source address found by the searching unit is already entered in the table, said return number is increased by exactly “1” at that source address.

13. A loop locating apparatus as set forth in claim 11, wherein the loop location decision function unit refers to the cumulative return number shown by the table and judges that the Layer 3 loop has occurred at the routers corresponding to the source addresses with relatively larger cumulative return numbers than the rest.

14. A loop locating apparatus as set forth in claim 13, wherein the loop location decision function unit decides that the Layer 3 loop has occurred at two or more routers when there are two or more routers corresponding to source addresses with relatively large cumulative return numbers and identifies the two or more routers relating to the Layer 3 loop.

15. A loop locating apparatus as set forth in claim 13, wherein the loop location decision function unit confirms that the Layer 3 loop occurred at two or more routers when judging that the above cumulative return number exceeds a predetermined threshold value and identifies the two or more routers relating to the Layer 3 loop.

16. A loop locating apparatus as set forth in claim 11, formed inside a video distributing system or formed by a terminal provided in the same sub network as the video distributing system.

17. A loop locating method in a Layer 3 network having: a command step of detecting an inability of an IP packet sent to the Layer 3 network to reach its destination and issuing a command to identify the location of occurrence of the Layer 3 loop,a transmission step of sending a series of IP (Internet Protocol) packets with successively incremented TTLs (Time to Live) settings as the inspection packets of the Layer 3 loop,a reception step of receiving a series of ICMP (Internet Control Message Protocol) “time exceeded” packets returned in response to the inspection packets and corresponding to the series of IP packets,a count step of finding the source address of a source transmitting the ICMP “time exceeded” packet from the received ICMP “time exceeded” packet and cumulatively counting the number of the ICMP “time exceeded” packets returned for each same source address SA, anda judgment step of judging that the routers corresponding to the source addresses with relatively large cumulatively counted return numbers are the location of occurrence of the Layer 3 loop.