i saw this thread as well as others:
http://forum.mikrotik.com/t/l2tp-receive-errors/29473/1
Ive actually had this issue since 2.9.27 and no one at MT would acknowledge it, also they would often delete my threads that complained of this issue or blame the internet links. now that they have added the R/TX-errors counter as of 3.20, people are reporting this issue as its clear when that counter runs up.
soo, im still having this problem across both pptp and l2tp up to 3.29 ROS. its not just the RX/TX errors..its the fact that on several of these links i have 10+mbit lines, and from point a to point b with ftp or otherwise i will get the full 10mbit. however through either PPTP or L2TP i get about 1-2mbit. and just poor latency/RTT.
I have changed the MTU/MRU on both sides to just about every value under 1500..it will change the throughput but its still very pathetic speeds/performance. of course, no queue anywhere.
i only do vpns over internet links, but in several sisutations named above i have replaced the VPN with a all cisco solution (both sides) and will achive near full throughput (yes like 9 or 10mbit where the MT on the same link will get 1-2mbit).
anyone can offer any suggestions now that this is a known issue?
thanks,