# US 2018/0026880 A1 · Target fec (forwarding equivalence class) stack based fec query in segment routing environments

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- Number: US 2018/0026880 A1
- Document ID: US20180026880A1
- Status: Published application
- Kind: A1
- Application number: 15/253,487
- Filed: 2016-08-31
- Published: 2018-01-25
- Earliest claimed: 2016-07-21
- Assignees: Cisco Technology, Inc.
- Applicants: Cisco Technology, Inc.
- Inventors: Nagendra Kumar Nainar; Carlos M. Pignataro; Faisal Iqbal
- Web page: https://patentgrep.com/patent/US20180026880A1

## CPC

- H04L 45/50: using label swapping, e.g. multi-protocol label switch [MPLS]
- H03M 13/47: Error detection, forward error correction or error protection, not provided for in groups H03M13/01 - H03M13/37
- H04L 1/004: {by using forward error control (H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00)}
- H04L 45/00: Routing or path finding of packets in data switching networks (routing or path finding in wireless networks H04W40/00)
- H04L 45/20: {Hop count for routing purposes, e.g. TTL}
- H04L 45/26: {Route discovery packet}
- H04L 45/28: using route fault recovery
- H04L 47/825: {Involving tunnels, e.g. MPLS}
- H04W 12/102: Route integrity, e.g. using trusted paths
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

In one embodiment, a method includes generating a first trace request at an initiator node configured for segment routing, the first trace request comprising a query for FEC (Forwarding Equivalence Class) information, transmitting the first trace request on a path comprising at least one node wherein FEC details for the node are unknown by the initiator node, receiving a response to the first trace request comprising the FEC information, transmitting a second trace request with the FEC information, and receiving a response to the second trace request providing FEC validation. An apparatus is also disclosed herein.

## Claims

### Claim 1

A method comprising:
generating a first trace request at an initiator node configured for segment routing, said first trace request comprising a query for FEC (Forwarding Equivalence Class) information;
transmitting said first trace request on a path comprising at least one node wherein FEC details for the node are unknown by the initiator node;
receiving a response to said first trace request comprising the FEC information;
transmitting a second trace request with the FEC information; and
receiving a response to said second trace request providing FEC validation.

### Claim 2 (depends on 1)

The method of claim 1 wherein said second trace request is transmitted on an LSP (Label Switched Path) over at least one MPLS (Multiprotocol Label Switching) tunnel.

### Claim 3 (depends on 1)

The method of claim 1 wherein said FEC validation provides end-to-end validation of an LSP (Label Switched Path).

### Claim 4 (depends on 1)

The method of claim 1 wherein said first trace request comprises a Target FEC Stack Sub-TLV containing said FEC query.

### Claim 5 (depends on 4)

The method of claim 4 wherein the Target FEC Stack Sub-TLV comprises said FEC query for each label in a label stack with unknown FEC details.

### Claim 6 (depends on 4)

The method of claim 4 wherein transmitting said second trace request comprises replacing said FEC query in the Target FEC Stack Sub-TLV with the received FEC information.

### Claim 7 (depends on 1)

The method of claim 1 wherein transmitting said second trace request comprises incrementing a Time-to-Live (TTL) by one.

### Claim 8 (depends on 1)

The method of claim 1 wherein transmitting said first trace request comprises setting a Time-to-Live (TTL) of a bottom label to one and inserting said FEC query into said first trace request for an egress node of an LSP (Label Switched Path).

### Claim 9 (depends on 1)

The method of claim 1 wherein the path comprises at least two stitched LSPs (Label Switched Paths).

### Claim 10

An apparatus comprising:
an interface for transmitting packets on an LSP (Label Switched Path);
a processor for generating a trace request at an initiator node configured for segment routing, the trace request comprising a query for FEC (Forwarding Equivalence Class) information, transmitting said trace request on a path comprising at least one node wherein FEC details for the node are unknown by the initiator node, and processing a response to said trace request comprising the FEC information; and
memory for storing the FEC information.

### Claim 11 (depends on 10)

The apparatus of claim 10 wherein the processor is further configured to transmit a second trace request with the FEC information and process a response to said second trace request providing FEC validation.

### Claim 12 (depends on 10)

The apparatus of claim 10 wherein the processor is further configured to transmit the FEC information to a controller for use by the controller.

### Claim 13 (depends on 10)

The apparatus of claim 10 wherein said trace request comprises a Target FEC Stack Sub-TLV containing said FEC query.

### Claim 14 (depends on 13)

The apparatus of claim 13 wherein the Target FEC Stack Sub-TLV comprises said FEC query for each label in a label stack with unknown FEC details.

### Claim 15 (depends on 10)

The apparatus of claim 10 wherein the processor is configured for transmitting a second trace request for use in FEC validation and incrementing a Time-to-Live (TTL) in said second trace request by one.

### Claim 16 (depends on 10)

The apparatus of claim 10 wherein transmitting said trace request comprises setting a Time-to-Live (TTL) of a bottom label to one and inserting said FEC query into said trace request for an egress node of the LSP.

### Claim 17

Logic encoded on one or more non-transitory computer readable media for execution and when executed operable to:
generate a first trace request at an initiator node configured for segment routing, said first trace request comprising a query for FEC (Forwarding Equivalence Class) information;
transmit said first trace request on a path comprising at least one node wherein FEC details for the node are unknown by the initiator node;
process a response to said first trace request comprising the FEC information;
transmit a second trace request with the FEC information; and
process a response to said second trace request providing FEC validation.

### Claim 18 (depends on 17)

The logic of claim 17 wherein said second trace request is transmitted on an LSP (Label Switched Path) over at least one MPLS (Multiprotocol Label Switching) tunnel.

### Claim 19 (depends on 17)

The logic of claim 17 wherein said FEC validation provides end-to-end validation of stitched LSPs.

### Claim 20 (depends on 17)

The logic of claim 17 wherein said first trace request comprises a Target FEC Stack Sub-TLV containing said FEC query.