Why is l2tp slow on mikrotik?

Question

VPN

Good afternoon! There are two mikrotik routers: hEx and hap ac2, they are in different houses with different providers. An l2tp tunnel was built between them with ipsec with BCP enabled (for dlna). Accordingly, there is l2 network connectivity. The hex network has nas, the ac2 network has a client. I'm downloading a file from nas to a client - the speed does not exceed 500 kilobytes per second. If you upload a file from a client to nas, then the entire channel between routers (about 100 Mbps) is utilized. For some reason, it is on l2tp that there is such an asymmetry. If we replace the tunnel with pptp, then the upload and download speeds are roughly comparable, although less than the rate at rates. Where to dig in this case?

vpn profiles on both routers:

add bridge=HOME bridge-learning=no name=HOME_bridging use-encryption=yes

l2tp server config:

/interface l2tp-server server
set authentication=mschap2 default-profile=VPN-Private enabled=yes \
ipsec-secret=*** use-ipsec=yes

Answer 1

I would suggest checking this table https://wiki.mikrotik.com/wiki/Manual:IP/IPsec#Har...
In particular, check that the encryption settings are set so that both devices can use hardware acceleration for cryptographic operations.
Check that packets are not fragmented - set mtu less for l2tp, ipsec

Answer 2

MTU for L2TP tunnel set to 1390.