On Packet Reordering in Time-Sensitive Networks

Time-sensitive networks (IEEE TSN or IETF DetNet) may tolerate some packet reordering. Re-sequencing buffers are then used to provide in-order delivery, the parameters of which (timeout, buffer size) affect worst-case delay and jitter. There is so far no precise understanding per-flow reordering metrics nor dimensioning re-sequencing in order guarantees, as required such networks. First, we show that a previously proposed metric, late time offset (RTO), determines timeout value. If network lossless, another defined byte (RBO), buffer. losses cannot be ignored, larger than RBO, depends on jitter, an arrival curve flow at its source, timeout. Then develop calculus compute RTO for path; method uses novel relation with jitter curve, together decomposition path into non order-preserving elements. We also analyse effect delay, propagation curves. particular that, lossless (but order-preserving) network, “for free”, namely, it does not increase whereas lossy increases apply analysis evaluate performance impact placing intermediate points illustrate results two industrial test cases.