public static void logWireSend(Span span, long wireSendTimeNanos, RequestLog requestLog) {
        span.annotate(SpanContextUtil.wallTimeMicros(requestLog, wireSendTimeNanos),
                      WIRE_SEND_ANNOTATION);
    }
Semi-official annotation for the time the first bytes were received on the wire.
brave/brave6/src/main/java/com/linecorp/armeria/internal/common/brave/SpanTags.java