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From: The Natural Philosopher <tnp@invalid.invalid>
Newsgroups: comp.os.linux.misc
Subject: Re: I never thought of this scenario
Date: Mon, 22 Apr 2024 11:35:40 +0100
Organization: A little, after lunch
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On 21/04/2024 20:58, Grant Taylor wrote:
> On 4/21/24 05:17, The Natural Philosopher wrote:
>> Not at all true in the case of address translation, routing protocols, 
>> traffic shaping and the like.
> 
> Network address translation isn't routing.  NAT happens /after/ routing 
> happens.
> 
Routing itself *is* network address translation. The router removes the 
current next hop address and replaces it with a new one, and it reduces 
the TTL field. All NAT does is replace the *source* destination/port as 
well, and store the originating port/ip address ready for return packets.

Where that happens in time  is purely implementation dependent. It might 
even happen simultaneously with a multicore CPU


  Rest of semantic arguments about all the things a router does that are 
not 'routing' according to one persons ideal definition of it, removed.

As an engineer all  that a router does is modify some or all of the 
information in a packet header, look up where the next hop is in its 
routing tables, and receive dynamic updates to those routing tables 
where appropriate. And forward the *modified* packet to the next hop.

If you want to take some academic position that defines some of those 
modifications as routing and others as not, I cant stop you.

But I can avoid further argument




-- 
"The great thing about Glasgow is that if there's a nuclear attack it'll 
look exactly the same afterwards."

Billy Connolly