Re: [Int-area] Some thoughts on draft-yong-intarea-inter-sites-over-tunnels

[Joe Touch <[e-mail]>]

On 12/6/2016 1:46 PM, Templin, Fred L wrote:
>> If there are multiple interfaces, why would it pick aero0? And what
>> would its QoS be? It can't have a single value, so the main IP
>> forwarding code can't decide between aero0 and other interfaces.
> The IP forwarding table has an entry such as:
>
>   2001:db8::/32 -> aero0
>
> Meaning that any IPv6 packet with a destination that matches 2001:db8::/32
> *and for which no more-specific route exists* goes out interface aero0
> unconditionally. The packet will have a TOS value, and it is that TOS that
> guides the aero0 interface on how to portion traffic over the underlying
> interfaces.
>
The problem is that this makes it impossible for the IP forwarding table
to control which aero0 encaps is used, thus which QoS it gets.

I.e., the main IP forwarding can't take QoS into account. I understand
that Aero can do the right thing, but only with the packets it already
has. It can't say "oh, I don't have a QOS for that, let me give it back
to the main IP forwarding for another interface".

If you have only one link, sure - there's no problem. But if you have
more than one (which is much more typical, even for hosts), then you do.

Joe