Re: [lisp] IPv6 UDP checksum issue

[Dino Farinacci <dino at cisco.com>]

> Since we're up-levelling the discussion, I don't understand why one  
> would use UDP as a router-router protocol in the first place,  
> especially for IPv6, where the chance that the packet will hit a NAT  
> are probably exactly zero.

Because when you use tunnel encapsulation, core routers attached to  
LAGs will see packets from one flow and polarize traffic on one member  
of the LAG.

So if the encapsulator can modify the source port of the UDP header  
based on a 5-tuple hash of the inner header, then there can be evenly  
balanced LAGs.

Core routers today load-split traffic across members of LAGs by doing  
a 5-tuple hash. And the 5 tuple hash works for TCP and UDP protocol  
numbered packets only.

The LISP authors received a lot of good input from network operators  
to not create this LAG problem. Hence, LISP uses UDP encapsulation.

> What I'm saying is that *if* UDP us used, it needs to be used  
> according to the RFCs that capture the IETF consensus on their use,  
> or the IETF consensus must be revised.

And what we are are saying is to be practical (and sensible).

Dino