[arin-ppml] Modified Header Forwarding for scalable routing

On Sun, Dec 20, 2009 at 3:21 AM, Robin Whittle <rw at> wrote:
> Short version:    Owen DeLong suggested a scalable routing solution
>                  would be to have DFZ routers modified to handle
>                  packets with modified header structure.  As I
>                  understand it, the new packet format would contain
>                  the ASN of the destination ISP and the DFZ routers
>                  forward it on this basis, without looking at the
>                  destination address, which would remain unaltered.

This isn't sounding that far off from just running MPLS in the DFZ
core, and passing labels around, with a set of label values
representing the peering edge routers of other ASNs.  Just
seems like if we already have a code base for passing packets
along based on a single tag value instead of doing address
parsing and lookups, with routing of the internal packet being
handled at the far end like normal after popping off the intervening
tag, we might consider leveraging an encapsulation format that's
been widely deployed and operated for the past decade.
Then the challenges become around how best to propagate
label assignment data between ISPs; the encapsulation and
decapsulation code is already well baked in PE devices the world

I suppose the 20 bit MPLS label limit will bite us in a decade or
so, when there's enough ISP edge routers to exhaust the 20 bit
label space, but it's sufficiently larger than the current number of
ASNs and ISP edge routers in the DFZ to work for quite a while.

This probably would be a better discussion on NANOG or some
other more routing-operations focused list, rather than a numbers
resource policy list, though.  ^_^;