Handling port identifier overflow in spanning tree protocol
Techniques for handling port identifier overflow when implementing Spanning Tree Protocol (STP) in a networking system are provided. According to one embodiment, a network device can receive a spanning tree protocol (STP) bridge protocol data unit (BPDU) and can extract a port identifier value from the BPDU. The network device can then determine a port number component of the port identifier value by decoding the least significant fourteen bits of the port identifier value and can determine a port priority component of the port identifier value by decoding the most significant two bits of the port identifier value.
1. A method comprising:
receiving, by a network device, a spanning tree protocol (STP) bridge protocol data unit (BPDU);
extracting, by the network device, a port identifier value from the BPDU;
determining, by the network device, a fourteen-bit port number associated with the BPDU by decoding the least significant fourteen bits of the port identifier value; and
determining, by the network device, an eight-bit port priority associated with the BPDU by:
decoding the most significant two bits of the port identifier value; and
converting the most significant two bits of the port identifier value into the eight-bit port priority, the converting comprising padding the least significant six bits of the eight-bit port priority with zeroes.
2. The method of claim 1 , wherein extracting the port identifier value comprises extracting a sixteen-bit value from octets 26 and 27 of the BPDU.
3. The method of claim 1 , wherein the network device is part of a system of network devices that includes more than 4095 ports on which STP is run.
4. The method of claim 1 , wherein the network device is a device in an 802.1BR-based system of devices.
5. The method of claim 1 , wherein a value of the eight-bit port priority is configurable within a range of zero to 192.
6. The method of claim 5 , wherein the value of the eight-bit port priority is configurable using steps of 64 within the range of zero to 192.
7. The method of claim 5 , wherein the value of the fourteen-bit port number is configurable within a range of zero to 16,383.
8. A non-transitory computer readable storage medium having stored thereon program code executable by a device, the program code causing the device to:
receive a spanning tree protocol (STP) bridge protocol data unit (BPDU);
extract a port identifier value from the BPDU;
determine a fourteen-bit port number associated with the BPDU by decoding the least significant fourteen bits of the port identifier value; and
determine an eight-bit port priority associated with the BPDU by;
decoding the most significant two bits of the port identifier value; and
converting the most significant two bits of the port identifier value into the eight-bit port priority, the converting comprising padding the least significant six bits of the eight-bit port priority with zeroes.
9. The non-transitory computer readable storage medium of claim 8 , wherein extracting the port identifier value comprises extracting a sixteen-bit value from octets 26 and 27 of the BPDU.
10. The non-transitory computer readable storage medium of claim 8 , wherein the device is part of a system of devices that includes more than 4095 ports on which STP is run.
11. The non-transitory computer readable storage medium of claim 8 , wherein the device is a network device in an 802.1BR-based system of network devices.
12. The non-transitory computer readable storage medium of claim 8 , wherein a value of the eight-bit port priority is configurable within a range of zero to 192.
13. The non-transitory computer readable storage medium of claim 12 , wherein the value of the eight-bit port priority is configurable using steps of 64 within the range of zero to 192.
14. The non-transitory computer readable storage medium of claim 8 , wherein the value of the fourteen-bit port number is configurable within a range of zero to 16,383.
15. A network device comprising:
a processor; and
a non-transitory computer readable medium having stored thereon program code that, when executed by the processor, causes the processor to:
receive a spanning tree protocol (STP) bridge protocol data unit (BPDU);
extract a port identifier value from the BPDU;
determine a fourteen-bit port number associated with the BPDU by decoding the least significant fourteen bits of the port identifier value; and
determine an eight-bit port priority associated with the BPDU by:
decoding the most significant two bits of the port identifier value; and
converting the most significant two bits of the port identifier value into the eight-bit port priority, the converting comprising padding the least significant six bits of the eight-bit port priority with zeroes.
16. The network device of claim 15 , wherein extracting the port identifier value comprises extracting a sixteen-bit value from octets 26 and 27 of the BPDU.
17. The network device of claim 15 , wherein the network device is part of a system of network devices that includes more than 4095 ports on which STP is run.
18. The network device of claim 15 , wherein the network device is a device in an 802.1BR-based system of devices.
19. The network device of claim 15 , wherein a value of the eight-bit port priority is configurable within a range of zero to 192.
20. The network device of claim 19 , wherein the value of the eight-bit port priority is configurable using steps of 64 within the range of zero to 192.
21. The network device of claim 15 , wherein the value of the fourteen-bit port number is configurable within a range of zero to 16,383.