# US 2018/0324078 A1 · System and method for loopback and network loop detection and analysis

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- Number: US 2018/0324078 A1
- Document ID: US20180324078A1
- Status: Published application
- Kind: A1
- Application number: 16/032,366
- Filed: 2018-07-11
- Published: 2018-11-08
- Earliest claimed: 2014-09-04
- Assignees: Accedian Networks Inc.
- Applicants: Accedian Networks Inc.
- Inventors: Stephane St-Laurent; Donald Stevenson
- Web page: https://patentgrep.com/patent/US20180324078A1

## CPC

- H04L 43/50: Testing arrangements
- H04L 1/243: {at the transmitter, using a loop-back}
- H04L 12/4641: {Virtual LANs, VLANs, e.g. virtual private networks [VPN] (LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272)}
- H04L 43/10: Active monitoring, e.g. heartbeat, ping or trace-route
- H04L 43/16: Threshold monitoring
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A method of determining the presence of a loopback in one or more networks comprises storing information related to a test instance; sending a loopback detection beacon (LPDB) containing information related to the test instance from a port on an originating device; monitoring the port for a predetermined time period to detect LPDBs arriving at the port during the predetermined time period; and determining whether a detected LPDB contains information corresponding to the stored information, to detect the presence of a loopback. The method may determine whether a detected loopback is a port loopback, a tunnel loopback or a service loopback. The stored information related to the test instance may be deleted if an LPDB arriving at the port and containing information corresponding to the stored information is not detected within the predetermined time period.

## Claims

### Claim at position 1

1-31. (canceled)

### Claim 32

A method of determining the presence of a tunnel loopback a multi-section network at a port, the method comprising:
assigning a section level to each section of said multi-section network;
assigning a unique domain number to one or more domains wherein one domain comprises one or more sections at the same section level and zero or more section at a lower section level;
storing a protocol data unit (PDU) that includes a Virtual Local Area Network (VLAN) signature;
sending a loopback detection beacon (LPDB) containing said PDU, a domain number and a time stamp;
restricting said LPDB to one or more sections related to the domain number in the LPDB;
determining whether a detected LPDB arriving at said port contains information corresponding to said stored PDU, to detect the presence of a loopback; and
determining that said detected loopback is a tunnel loopback if said detected LPDB contains said VLAN signature and whether said detected loopback is a hard cable loopback or a remote facility loopback based on a difference between said time stamp and the arrival time of said detected LPDB.

### Claim 33 (depends on 32)

The method of claim 32 wherein said restriction is done within a forwarding rule.

### Claim 34 (depends on 32)

The method of claim 32 in which said detected loopback is a port loopback or a service loopback, and wherein said method includes determining whether said detected loopback is a port loopback or a service loopback.

### Claim 35 (depends on 32)

The method of claim 32 in which said originating device is a network device.

### Claim 36 (depends on 32)

The method of claim 32 in which said PDU is deleted if an LPDB arriving at said port and containing information corresponding to said PDU is not detected within said predetermined time period.

### Claim 37 (depends on 32)

The method of claim 32 which includes determining whether a detected port loopback is a hard cable loopback or a facility loopback.

### Claim 38 (depends on 32)

The method of claim 32 in which said detected loopback is determined to be a hard cable loopback if said difference is smaller than a predetermined threshold, and is determined to be a facility loopback if said difference is greater than said predetermined threshold.

### Claim 39 (depends on 34)

The method of claim 34 in which said LPDB includes a Virtual Local Area Network (VLAN) signature that includes a Customer Service Specification (CSS) and a Network Service Specification (NSS), and wherein said method includes determining whether said detected loopback is a service loopback if (1) the CSS of an LPDB. arriving at said port matches the CSS of an LPDB sent from said port, or (2) the NSS of an LPDB arriving at said port matches the NSS of an LPDB sent from said port.

### Claim 40 (depends on 32)

The method of claim 32 in which the monitoring and determining are implemented on said originating device.

### Claim 41 (depends on 32)

The method of claim 32 in which the monitoring and determining are implemented on a device or server separate from said originating device.

### Claim 42 (depends on 32)

The method of claim 32 in which affected traffic is discarded in response to the detection of a loopback.

### Claim 43 (depends on 32)

The method of claim 32 in which future traffic is blocked at said port in response to the detection of a loopback.

### Claim 44 (depends on 32)

The method of claim 32 in which said LPDB is restricted to one or more selected sections of the one or more networks.

### Claim 45 (depends on 32)

The method of claim 32 in which said LPDB is generated using a software tool.

### Claim 46 (depends on 32)

The method of claim 32 in which said software tool is used to detect loopback based on said LPDB.

### Claim 47

A system of determining the presence of a tunnel loopback a multi-section network at a port, the method comprising:
a section level assigned to each section of said multi-section network;
a unique domain number assigned to one or more domains wherein one domain comprises one or more sections at the same section level and zero or more section at a lower section level;
a protocol data unit (PDU) stored on a memory at the port, wherein said PDU includes a Virtual Local Area Network (VLAN) signature;
a loopback detection beacon (LPDB) containing said PDU, a domain number and a time stamp transmitted by said port into said network wherein said LPDB is restricted to one or more sections related to the domain number in the LPDB;
wherein said port receives said LPDB and determines whether a received LPDB contains information corresponding to said stored PDU, to detect the presence of a loopback;
and said port determines that said detected loopback is a tunnel loopback if said detected LPDB contains said VLAN signature and whether said detected loopback is a hard cable loopback or a remote facility loopback based on a difference between said time stamp and the arrival time of said detected LPDB.

### Claim 48 (depends on 47)

The method of claim 47 wherein said restriction is done within a forwarding rule.

### Claim 49 (depends on 47)

The method of claim 47 in which said detected loopback is a port loopback or a service loopback, and wherein said method includes determining whether said detected loopback is a port loopback or a service loopback.