Shim6, was: Re: filtering /48 is going to be necessary

William Herrin bill at
Mon Mar 12 17:50:13 CDT 2012

On Mon, Mar 12, 2012 at 5:14 PM, Iljitsch van Beijnum
<iljitsch at> wrote:
> On 12 Mar 2012, at 21:15 , William Herrin wrote:
>> Not at all. You just build a second tier to the routing system.
> We already have two tiers: DNS names and IP addresses.

Hi Iljitsch,

If only that were true. The DNS doesn't sit to the side of TCP,
managing the moment to moment layer 4 to layer 3 mapping function the
way ARP sits to the side of IP. Instead, the DNS's function is
actuated all the way up at layer 7.

This was the crux of my complaint about the getaddrinfo/connect APIs
last week. Their design makes a future introduction of a transport
protocol, something which actually does interact with the name service
at the proper layer, needlessly hard.

That and the common non-operation of the DNS TTL invalidates DNS' use
as a routing tier.

Bill Herrin

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

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