Congestion control in an optical line terminal

An Optical Line Terminal (OLT) system comprising:

• a plurality of physical OLT Passive Optical Network (PON) ports, wherein each physical OLT PON port is for communicating with at least one Optical Network Unit (ONU), and wherein each physical OLT PON port having has a respective enforced maximum upstream bandwidth;
• an uplink port through which data received from each physical OLT PON port are transmitted;
• a buffer to store said data;
• and
• a bandwidth modifier for alleviating or preventing congestion of said data at the uplink port of the OLT system by reducing the enforced maximum upstream bandwidth for at least one physical OLT PON port of the plurality of physical OLT PON ports;
• wherein said reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON port includes:
• obtaining parameters relating to each physical OLT PON port and reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON by an amount dependent upon the parameters;
• obtaining an indication of whether there is congestion of said data in the buffer of the OLT system, the buffer storing said data prior to transmission through the uplink port of the OLT system, and said data comprising data of different classes;
• and reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON if there is congestion of said data in the buffer;
• wherein said reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON port of the plurality of physical OLT PON ports causes the at least one physical OLT PON port in the OLT system to perform at least one of:
• (i) reducing a number of transmission windows granted to at least one ONU connected to the at least one physical OLT PON port, and (ii) reducing a duration of one or more transmission windows granted to at least one ONU connected to the at least one physical OLT PON port.

A non-transitory computer readable medium having stored thereon computer readable instructions for execution in one or more processing devices in an Optical Line Terminal (OLT) system, the OLT system having:

• (i) a plurality of physical OLT Passive Optical Network (PON) ports, wherein each physical OLT PON port of the plurality of physical OLT PON ports is for communicating with at least one Optical Network Unit (ONU) and each physical OLT PON port of the plurality of physical OLT PON ports having a respective enforced maximum upstream bandwidth, and (ii) an uplink port through which data received from each of the plurality of physical OLT PON ports are transmitted;
• when executed, the computer readable instructions cause the one or more processing devices to perform a method comprising:
• preventing or alleviating congestion of said data at the uplink port of the OLT system by reducing an enforced maximum upstream bandwidth for at least one physical OLT PON port of the plurality of physical OLT PON ports;
• wherein said reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON port includes:
• obtaining parameters relating to each physical OLT PON port and reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON by an amount dependent upon the parameters;
• obtaining an indication of whether there is congestion of said data in a buffer of the OLT system, the buffer storing said data prior to transmission through the uplink port of the OLT system, and said data comprising data of different classes;
• and reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON if there is congestion of said data in the buffer;
• wherein said reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON port of the plurality of physical OLT PON ports causes the at least one physical OLT PON port in the OLT system to perform at least one of:
• (a) reducing a number of transmission windows granted to at least one ONU connected to the at least one physical OLT PON port, and (b) reducing a duration of one or more transmission windows granted to at least one ONU connected to the at least one physical OLT PON port.

An Optical Line Terminal (OLT) system comprising:

• a plurality of physical OLT Passive Optical Network (PON) ports, each physical OLT PON port of the plurality of physical OLT PON ports for communicating with at least one Optical Network Unit (ONU), and each physical OLT PON port of the plurality of physical OLT PON ports having a respective enforced maximum upstream bandwidth;
• an uplink port through which data received from each of the plurality of physical OLT PON ports are transmitted;
• and
• means for reducing the enforced maximum upstream bandwidth for at least one physical OLT PON port of the plurality of physical OLT PON ports to alleviate or prevent congestion of said data at the uplink port;
• wherein said reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON port includes:
• obtaining parameters relating to each physical OLT PON port and reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON by an amount dependent upon the parameters;
• obtaining an indication of whether there is congestion of said data in a buffer of the OLT system, the buffer storing said data prior to transmission through the uplink port of the OLT system, and said data comprising data of different classes;
• and reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON if there is congestion of said data in the buffer;
• wherein said reducing the enforced maximum upstream bandwidth for the at least one physical OLT PON port of the plurality of physical OLT PON ports causes the at least one physical OLT PON port in the OLT system to perform at least one of:
• (i) reducing a number of transmission windows granted to at least one ONU connected to the at least one physical OLT PON port, and (ii) reducing a duration of one or more transmission windows granted to at least one ONU connected to the at least one physical OLT PON port.

A method in an Optical Line Terminal (OLT) system having a plurality of physical OLT Passive Optical Network (PON) ports, each physical OLT PON port of the plurality of physical OLT PON ports for communicating with at least one Optical Network Unit (ONU), the OLT system further including an uplink port through which data received from each of the plurality of physical OLT PON ports are transmitted;

• the method comprising:
• preventing or alleviating congestion of said data at the uplink port of the OLT system by performing at least one of:
• (i) reducing a number of transmission windows granted to at least one ONU connected to at least one physical OLT PON port of the plurality of physical OLT PON ports, and (ii) reducing a duration of one or more transmission windows granted to at least one ONU connected to the at least one physical OLT PON port of the plurality of physical OLT PON ports;
• wherein said reducing the number of transmission windows and/or said reducing the duration of one or more transmission windows includes the steps of:
• obtaining parameters relating to each physical OLT PON port and reducing the number of transmission windows and/or reducing the duration of one or more transmission windows by an amount dependent upon the parameters;
• obtaining an indication of whether there is congestion of said data in a buffer of the OLT system, the buffer storing said data prior to transmission through the uplink port of the OLT system, and said data comprising data of different classes;
• and reducing the number of transmission windows and/or reducing the duration of one or more transmission windows if there is congestion of said data in the buffer;
• wherein the parameters include at least:
• (i) the number of active ONUs connected to each physical OLT PON port;
• and
• (ii) the total amount of data requested from each physical OLT PON port, the total amount of data requested from a physical OLT PON port representing a sum of the amount of data requested from ONUs connected to that physical OLT PON port;
• and
• (iii) a total peak information rate (PIR) of each physical OLT PON port, the total PIR of a physical OLT PON port representing the sum of the PIR of each of the ONUs connected to that physical OLT PON port, wherein the PIR specifies the maximum rate at which an ONU is allowed to transmit data;
• and
• (iv) a total committed information rate (CIR) of each physical OLT PON port, the total CIR of a physical OLT PON port representing the sum of the CIR of each of the ONUs connected to that physical OLT PON port, wherein the CIR specifies the minimum rate at which an ONU is guaranteed to transmit data;
• and
• (v) an upstream traffic rate at each physical OLT PON port.