A novel method for estimating the variable and constant components of one-way delays without using the synchronized clocks

摘要

One-way delay monitoring is necessary for the time-sensitive media streaming. The conventional methods of one-way delay measurement require the clocks used at both the source and sink nodes of a path have to be synchronized. Clock synchronization can be performed either through GPS or NTP-based methods. Both approaches bear certain limitations. This paper describes a novel method of estimating the variable and constant components of one-way delays without requiring the local clocks at the end nodes to be synchronized. This method requires a sequence of probing packet batches to be sent from a source to a sink along a fixed one-way path. The timestamps of sending and receiving the packets at the source and the sink are recorded with respect to the local clocks. The variable and constant components of one-way delays can be estimated based on carefully crafting the relationship between the timestamps measured with respect to local clocks. The variable delay component is estimated based on the difference between the inter-arrival times between batches that are measured at the source and the sink, respectively. The constant delay component offset by the clock skew can then be estimated by making use of the estimated values of the variable delay component and the timestamps measured locally at the source and the sink. A novel concept of nominal service duration for a packet batch is introduced in modeling the one-way delays. The introduction of the nominal service duration makes this estimation method to be able to estimate the variable component of one-way delays in the existence of cross traffic. Without the knowledge of the offset of the local clocks at the source and the sink, this estimation method can only estimate the constant delay component up to the offset value of the actual constant delay.