Packet sending method, device, and system

A method for sending packets, comprising:

• receiving, by a second network device, a first packet destined for a destination device, wherein the first packet is from a first network device, and the first packet comprises a first indication identifier, wherein a segment routing header (SRH) is added to the first packet, and wherein the first indication identifier is carried in the SRH;
• determining, by the second network device, that a primary forwarding path from the second network device to the destination device is unreachable;
• and
• in response to determining that the primary forwarding path is unreachable, avoiding, by the second network device based on an indication of the first indication identifier, using a backup forwarding path to send the first packet to the destination device, wherein the backup forwarding path is a path from the second network device to the destination device, and wherein the backup forwarding path passes through the first network device.

A network device operating as a first network device, comprising:

• a memory comprising instructions;
• a processor coupled to the memory, wherein when the instructions are executed by the processor, the instructions cause the network device to:
• obtain a first packet destined for a destination device,
• add a first indication identifier to the first packet to generate a second packet, wherein the first indication identifier is used to indicate a second network device to avoid using a backup forwarding path from the second network device to the destination device to send the second packet to the destination device, wherein the backup forwarding path passes through the first network device, and wherein, to add the first indication identifier to the first packet to generate the second packet, the instructions, when executed by the processor, cause the network device to:
• add a segment routing header (SRH) to the first packet to generate the second packet, wherein the first indication identifier is carried in the SRH, and
• send the second packet to the second network device by using a first forwarding path, wherein the first network device and the second network device are part of a network system having a plurality of network devices.

A network device operating as a second network device, comprising:

• a memory comprising instructions;
• a processor coupled to the memory, wherein when the instructions is executed by the processor, the instructions cause the network device to:
• receive a first packet destined for a destination device, wherein the first packet is from a first network device, and the first packet comprises a first indication identifier, wherein a segment routing header (SRH) is added to the first packet, and wherein the first indication identifier is carried in the SRH;
• determine that a primary forwarding path from a second network device to the destination device is unreachable, wherein the first network device and the second network device are part of a network system having a plurality of network devices;
• and
• in response to determining that the primary forwarding path is unreachable, avoid, based on the first indication identifier, using a backup forwarding path to send the first packet to the destination device, wherein the backup forwarding path is a path from the second network device to the destination device, and wherein the backup forwarding path passes through the first network device.