Wait, isn’t “no buffer space available” the same message we saw when there was a bug with the PPP driver filling up the kernel route cache? In cursemipn’s other thread that he linked to, he mentions his router runs a PPPoE server with hundreds of clients. He also mentions that he has no problems with 6.7 and his problems start with 6.8. RouterOS 6.8 was the version that included the large PPP driver rewrite, and for several versions after that, MikroTik had to fix tons of PPP bugs that 6.8 introduced. The kernel route cache memory leak was fixed for most PPP interfaces on 6.13, but maybe MikroTik missed one that still exists.
His packet loss issue could easily be explained by a runaway PPP driver filling up the kernel route cache, which would prevent the router from being able to transmit anything, and then the kernel route cache garbage collector intermittently managing to clear out some of the entires in the route cache (which would allow the router to once more transmit responses) before it gets filled up again.
This is the thread in question: http://forum.mikrotik.com/t/rb2011uas-2hnd-stops-responding-spontaneously/75301/1
To cursemipn: the next time this happens, please paste the results of “/ip route cache print” to this thread.
– Nathan