* My provider, Telefonica/Movistar, dominant operator in Spain, is well known for its neglect to IPv6, which led Spain from top positions in IPv6 development/deployment to the bottom of world in deployment scale
* They don't offer native IPv6, and their ONT/router combo does not support 6to4 tunnels
* When I "unbundled" their VLANs so that the data one went into my MikroTik hAP ac as PPPoE, I started trying HE tunnels:
* MikroTik connects well, and ICMP/UDP packets flows well
* When I try to send TCP it fails. I was thinking (misled) that it were MTU/MSS issues, but they were not
* I decided to try a new strategy: to put a mirror ether port in the WAN side of the ONT, and another in the MikroTik (LAN) side, and wireshark it
What I found, is a strange traffic pattern:
* Outside of the Mikrotik the connection goes well upstream (packet seen in a normal TCP), but there is a lot of spurious retransmissions (from our side) as if the other side
responses were not arriving to my testing laptop.
* Inside of the Mikrotik those "normal" responses from upstream are not seen beyond the first two (SYN, SYN+ACK) packets.
The interesting finding is that all packets my laptop sends have, when seen from the WAN side, incorrect PPPoE payload length. A typical one would say in
. Those packets seem to arrive to destination, as answers arrive well to the router...3381 (Incorrect, should be 173)
Inside, in the LAN side, received packets that enter the MikroTik have the same incorrect PPPoE payload length.
My hypothesis is that their HGU (Home Gateway Unit, they call it) is corrupting the PPPoE packets, possibly when trying to do QoS or mark connection or flow.
This only happens after it sees a SYN+ACK, and affects the payload calculation in both directions. Apparently they PPPoE concentrators ignore the payload field, so everything works for them.
Now my question: can I have the RouterOS machinery ignore broken payload fields, and allow the Spanish market to use MikroTik for fibre IP tunnels in the main operator?
BTW, thanks for the hAP lite I got in the Valencia MUM, it was extremely helpful to finish this debugging process.