I don't understand why it is necessary or useful for routers.
+1 I agree, it would be really useful as Mikrotik doesn't currently support dynamic multipoint VPN (DMVPN) or similar technology.
Zeroteir is a really a very easy/user friendly DMVPN clone (of sorts) which a lot of people deploy when they don't have native support for DMVPN.
It also doesn't require kernel drivers, its all done in usermode as well as uses typical linux tools/devices such as tun/tap, bridges and so forth which means it should't be rocket science to implement to ROS. Memory requirements is fairly minimal (about 4-5MB with about 50+ routes/networks connected).
The throughput is also very very decent and is only just a shy short of native IPSEC connections which is done in the kernel. I get high end 400Mbits (around 480Mits) on a gig connection with minimal CPU load running in usermode. If they did port it to kernel, it would beat IPSEC hands down.
p.s IMO its the best solution right now if you have OpenVZ machines you need to link up to your network/pool where you can't use IPSEC for whatever reason.
This is taken from a 4 CPU system (Intel(R) Xeon(R) CPU E3-1241 v3 @ 3.50GHz) and during the tests only two cores were maxed and this is all done in usermode, no kernel drivers and different DC/ISP.
iperf3 -c 172.30.50.1 Connecting to host 172.30.50.1, port 5201 [ 4] local 172.30.0.165 port 55866 connected to 172.30.50.1 port 5201 [ ID] Interval Transfer Bandwidth Retr Cwnd [ 4] 0.00-1.00 sec 70.3 MBytes 590 Mbits/sec 157 233 KBytes [ 4] 1.00-2.00 sec 78.9 MBytes 662 Mbits/sec 0 411 KBytes [ 4] 2.00-3.00 sec 76.7 MBytes 643 Mbits/sec 173 247 KBytes [ 4] 3.00-4.00 sec 76.9 MBytes 645 Mbits/sec 38 188 KBytes [ 4] 4.00-5.00 sec 75.6 MBytes 634 Mbits/sec 7 263 KBytes [ 4] 5.00-6.00 sec 74.6 MBytes 626 Mbits/sec 33 215 KBytes [ 4] 6.00-7.00 sec 78.2 MBytes 656 Mbits/sec 12 317 KBytes [ 4] 7.00-8.00 sec 75.1 MBytes 630 Mbits/sec 44 148 KBytes [ 4] 8.00-9.00 sec 69.9 MBytes 586 Mbits/sec 39 172 KBytes [ 4] 9.00-10.00 sec 72.3 MBytes 607 Mbits/sec 19 231 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth Retr [ 4] 0.00-10.00 sec 748 MBytes 628 Mbits/sec 522 sender [ 4] 0.00-10.00 sec 745 MBytes 625 Mbits/sec receiver