Method and network device for transmitting data stream

A non-transitory hardware-readable storage medium storing a program that, when executed by hardware, cause the hardware to perform operations comprising:

• determining, according to a forwarding table, a plurality of candidate forwarding ports as a potential forwarding port used for transmitting a data stream, wherein the data stream is one of a plurality of data streams each with a designated data stream priority level;
• determining a port priority level of each of the plurality of candidate forwarding ports;
• selecting a first candidate forwarding port from the plurality of candidate forwarding ports for transmitting the data stream, wherein the port priority level of the first candidate forwarding port is lower than or equal to the designated data stream priority level of the data stream;
• transmitting the data stream over the first candidate forwarding port;
• during the transmission of the data stream over the first candidate forwarding port, determining that the first candidate forwarding port becomes congested;
• and
• switching the transmission of the data stream from the first candidate forwarding port to a second candidate forwarding port of the plurality of candidate forwarding ports, wherein the second candidate forwarding port is not congested, and the port priority level of the second candidate forwarding port is lower than or equal to the designated data stream priority level of the data stream,
• wherein the port priority level of the first candidate forwarding port is higher than the port priority level of the second candidate forwarding port,
• wherein each of the plurality of candidate forwarding ports corresponds to an individual port state table,
• wherein the selecting the first candidate forwarding port for transmitting the data stream comprises:
• querying the individual port state table for each of the plurality of candidate forwarding ports,
• wherein the individual port state table provides correspondence between the port priority level of one of the plurality of candidate forwarding ports, the data stream priority level for each of the plurality of data streams, and a port state for each of the plurality of data streams, and
• wherein the port state provides a singular indication of UP or DOWN for each of the plurality of data streams based on a comparison between the designated data stream priority level and the port priority level of one of the plurality of candidate forwarding ports.