Discovering a reverse path for initiating bidirectional forwarding detection (BFD)

1. An initiator node operating in a network, the initiator node comprising:

a processing device, and

a memory device configured to store a computer program having instructions that, when executed, enable the processing device to

send an echo request in a forward direction to a reflector node operating in the network,

wherein the echo request is sent to the reflector node to discover a reverse path in a reverse direction from the reflector node to the initiator node,

wherein the reverse path is discovered for the purpose of initiating a Bidirectional Forwarding Detection (BFD) or Multi-Protocol Label Switching (MPLS) Ping procedure,

wherein the echo request includes an appeal to obtain information about one or more Segment Routing (SR) policies in the reverse direction, and wherein each of the one or more SR policies includes a label stack that defines one or more intermediate nodes in an SR path from the reflector node to the initiator node, and

wherein the information includes a court (N), one or more constraint flags, and one or more path constraint parameters, wherein the count N represents a maximum number of SR policies in the reverse direction to be obtained, and wherein each of the one or more constraint flags indicates whether a respective path constraint parameter is to be obtained.

2. The initiator node of claim 1 , wherein the echo request is a Multi-Protocol Label Switching (MPLS) ping message on a non-policy Segment Routing (SR) tunnel.

3. The initiator node of claim 1 , wherein each of the one or more path constraint parameters includes one or more of color, type, and origin, wherein color is a numeric value that distinguishes an SR policy from other SR policies, wherein type is a numeric value that represents a path type of each SR policy in the reverse direction, and wherein origin is a numeric value that represents an originator of each SR policy in the reverse direction.

4. The initiator node of claim 1 , wherein the one or more path constraint parameters are user-defined constraints.

5. The initiator node of claim 1 , wherein the instructions further enable the processing device to receive an echo reply from the reflector node in response to the echo request, wherein the echo reply includes a number (M) of reverse Segment Routing (SR) policies that meet one or more path constraint parameters, and wherein each of the M reverse SR policies includes a label stack and a Binding Segment Identifier (BSID).

6. The initiator node of claim 5 , wherein the instructions further enable the processing device to receive a user selection for selecting one of the reverse SR policies.

7. The initiator node of claim 6 , wherein the instructions further enable the processing device to initiate a Seamless BFD (S-BFD) procedure by transmitting an S-BFD request including the BSID of the selected reverse SR policy to the reflector node along a selected forward SR policy.

8. The initiator node of claim 7 , wherein, in response to receiving the S-BFD request, the reflector node is configured to cache the BSID, process a payload of the S-BFD request, and expand the BSID to include a list of one or more reverse Segment Identifiers (SIDs) for transmission of an S-BFD reply or MPLS Ping to the initiator node along the selected reverse SR policy.

9. A non-transitory computer-readable medium configured to store computer logic having instructions that, when executed, cause one or more processing devices to:

send an echo request in a forward direction from an initiator node to a reflector node,

wherein the echo request is sent to the reflector node to discover a reverse path in a reverse direction from the reflector node to the initiator node, and

wherein the reverse path is discovered for the purpose of initiating a Bidirectional Forwarding Detection (BFD) or Multi-Protocol Label Switching (MPLS) Ping procedure,

wherein the echo request includes an appeal to obtain information about one or more Segment Routing (SR) policies in the reverse direction, and wherein each of the one or more SR policies includes a label stack that defines one or more intermediate nodes in an SR path from the reflector node to the initiator node, and

wherein the information includes a count (N), one or more constraint flags, and one or more path constraint parameters, wherein the count N represents a maximum number of SR policies in the reverse direction to be obtained, and wherein each of the one or more constraint flags indicates whether a respective path constraint parameter is to be obtained.

10. The non-transitory computer-readable medium of claim 9 , wherein the echo request is a Multi-Protocol Label Switching (MPLS) ping message on a non-policy Segment Routing (SR) tunnel.

11. The non-transitory computer-readable medium of claim 9 , wherein each of the one or more path constraint parameters includes one or more of color, type, and origin, wherein color is a numeric value that distinguishes an SR policy from other SR policies, wherein type is a numeric value that represents a path type of each SR policy in the reverse direction, and wherein origin is a numeric value that represents an originator of each SR policy in the reverse direction.

12. A method comprising:

sending an echo request in a forward direction from an initiator node to a reflector node;

receiving, at the initiator node, an echo reply from the reflector node in response to the echo request;

receiving a user selection for selecting one of the reverse SR policies; and

initiating a Seamless BFD (S-BFD) procedure by transmitting an S-BFD request including the BSID of the selected reverse SR policy from the initiator node to the reflector node along a selected forward SR policy,

wherein the echo request is sent to the reflector node to discover a reverse path in a reverse direction from the reflector node to the initiator node, and

wherein the reverse path is discovered for the purpose of initiating a Bidirectional Forwarding Detection (BFD) or Multi-Protocol Label Switching (MPLS) Ping procedure,

wherein the echo reply includes a number (M) of reverse Segment Routing (SR) policies that meet one or more path constraint parameters, and

wherein each of the M reverse SR policies includes a label stack and a Binding Segment Identifier (BSID).

13. The method of claim 12 , wherein, in response to receiving the S-BFD request, the reflector node is configured to cache the BSID, process a payload of the S-BFD request, and expand the BSID to include a list of one or more reverse Segment Identifiers (SIDs) for transmission of an S-BFD reply or MPLS Ping to the initiator node along the selected reverse SR policy.