[arin-ppml] ARIN Draft Policy 2011-5: Shared Transition Space

William Herrin bill at herrin.us
Tue Jul 5 17:40:22 EDT 2011

On Tue, Jul 5, 2011 at 5:30 PM, Owen DeLong <owen at delong.com> wrote:
> On Jul 5, 2011, at 2:24 PM, William Herrin wrote:
>> On Tue, Jul 5, 2011 at 5:13 PM, Owen DeLong <owen at delong.com> wrote:
>>> On Jul 5, 2011, at 2:01 PM, William Herrin wrote:
>>>> 2. Router interface numbering is a potential use case. Filtering of
>>>> RFC1918 is too widespread to overcome, so using it outside the NAT
>>>> breaks path MTU detection. That's not inherently true of this new
>>>> space and nonfiltering could be encouraged in a way that renders it
>>>> usable in a few years.
>>> Not really... How would you know which ISP to route the packet
>>> back to?
>> You don't care. The packets you care about receiving from the router
>> are ICMP type 3 (destination unreachable) and ICMP type 11 (time
>> exceeded) . Those flow only one direction -- from the router back
>> towards you.
> If a packet is inbound towards me and needs fragmentation, for PMTU
> discovery, then, an ICMP type 3 would be sent back towards the
> originator of said packet.

Correct, but the originator doesn't care what address that packet
comes from and doesn't attempt to reply to it.

Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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