[e2e] Header length field in IP header

Zartash Afzal Uzmi zartash at lums.edu.pk
Fri Sep 24 12:51:23 PDT 2004

> -----Original Message-----
> From: end2end-interest-bounces at postel.org
> [mailto:end2end-interest-bounces at postel.org]On Behalf Of Zaphod
> Beeblebrox
> Sent: Friday, September 24, 2004 2:21 AM
> To: end2end-interest at postel.org
> Subject: Re: [e2e] Header length field in IP header
> (I just wanted to keep the flow of the argument going,
> no disrespect meant to anyone)
> as an humble observation by an observer from another
> galaxy,
> Why don't earthlings do this:
>              DNS-------DNS----DNS
>               |          |      |
> Endhost1----NAT1-------NAT2---NAT3-----endhost2
> Since all end hosts will always do a name resolution,
> we can treat that as a way to setup the path :), just
> like a TCP handshake :)

unless the source uses destinaiton's IP address without going through the
name resolution. And if I trust arp caching, I am always going to get the
same route. Further, this same route may have been "tore off" by the
intermediate NAT gateways! So yes, the scheme will work in another galaxy
where inhabitants do obey lots of constraints but earthlings are a different
creature, they will go ahead and call your NAT gateway an LSR :)

> In other words, if I want to talk to
> endhost1.beeblebrox.com wants to talk to
> endhost2.end2end.org , it contacts the DNS on NAT1,
> gets a local IP on each side, NAT1 contacts NAT2 and
> gets a locally significant IP on each side and so
> on...
> we could use nice words and call it "downstream on
> demand IP distribution mode"
> Hope this helps :),
> -ZB
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