The OLT uplink circuit usually refers to the circuit that connects the OLT to the BRAS. Currently, the bandwidth of the OLT uplink circuit is mainly divided into two types: 10GE and GE.
Usually, when the bandwidth utilization peak of the OLT’s upstream circuit reaches 70%, expansion is required. The bandwidth utilization value mentioned here generally comes from the OLT network management, referring to the average bandwidth utilization rate over 15 minutes. But the user’s internet experience is affected by real-time (10ms level) bandwidth utilization. When the peak real-time bandwidth utilization of the uplink circuit reaches 100% (which is actually only close to 100%), the network speed of the users carried by the OLT may be affected.
But what is the relationship between the 15 minute average peak bandwidth utilization (hereinafter referred to as “average peak”) and the real-time peak bandwidth utilization? Below, we will analyze the peak and average real-time bandwidth utilization rates (referred to as “second peak”) of some OLT uplink circuits in a provincial capital city.
Due to the fact that the upstream bandwidth utilization of the OLT’s upstream circuit is much lower than that of the downstream, the upstream bandwidth will not affect the user’s network speed, so we only analyze the downstream bandwidth utilization.
210GE upstream circuit
The main upstream circuit of OLT is 10GE. Based on the test results of a certain month in 2020, the second peak to average peak ratio (second peak/average peak) and difference (second peak to average peak) of the 10GE upstream circuit were analyzed; Due to the small second peak, the upstream bandwidth will not affect the user’s network speed, so only circuits with a second peak exceeding 30% were analyzed.
From the ratio of the second peak to the average peak, there is a clear linear relationship between the “second peak/average peak” and the average peak, with a slight decrease in the ratio as the average peak increases. When the average peak exceeds 50%, the average “second peak/average peak” is 1.18, and the maximum is 1.21.
From the perspective of the difference between the second peak and the mean, there is also a clear linear relationship between the “second peak mean peak” and the mean peak. As the mean peak increases, the difference gradually increases. When the average peak exceeds 50%, the average of “second peak average peak” is 10.57%, and the maximum is 12.4%.
3GE uplink circuit
Some of the OLT upstream circuits in rural areas are still GE, and many GE upstream circuits have a peak to second ratio exceeding 90%. Due to the impact of real-time (10ms level) bandwidth utilization on users’ internet experience, according to the analysis method in the previous section, it can be seen that when the second peak exceeds 90%, the 10ms level peak is likely to be limited by bandwidth, resulting in the limitation of the second peak.
This can also be seen from the relationship between the “second peak average peak” and the average peak in the GE upstream circuit. According to the analysis in the previous section, when the bandwidth of the upstream circuit is not limited, there is a clear linear relationship between the “second peak average peak” and the average peak, and the difference gradually increases as the average peak rises. But in the relationship diagram between the “second peak average peak” and the average peak in the GE upstream circuit, when the average peak is less than 43.98%, it is basically consistent with the above phenomenon; When the average peak exceeds 43.98%, as the average peak increases, the difference shows a significant decrease, indicating that the second peak is limited by bandwidth.
So we offer the following suggestions:
When the upstream bandwidth of OLT is 10GE, it is appropriate to set the expansion threshold at 70%. However, if it exceeds 75%, the second peak will exceed 90%, resulting in bandwidth limitation.
When the upstream bandwidth of OLT is GE, the second peak is greatly affected by user traffic; When the average peak exceeds 45%, the second peak begins to be limited to varying degrees by bandwidth; Therefore, the expansion threshold of GE’s upstream circuit should not exceed 45%.
