North American Network Operators Group
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Re: IPv6 news

  • From: Tony Li
  • Date: Sun Oct 16 04:49:11 2005 




Doesn't NAT, or more specifically the most commonly used, NAPT, create

hard state within the network, which then makes it violate the

end-to-end argument ? Also, because it has to understand transport and

application layer protocols, to be able to translate embedded
addresses,

doesn't this also make it violate end-to-end ? I've understood the

fundamental benefit of following the end-to-end argument is that
you end

up with a application agnostic network, which therefore doesn't create

future constraints on which applications can then be used over that

network. In an end-to-end "compliant" network, any new transport layer

protocols, such as SCTP or DCCP, and new user applications, only
require

an upgrade of the end or edge node software, which can be performed in

an incremental, per edge node as needed basis. In other words, there

isn't any whole of network upgrade cost or functionality deployment

delay to support new applications, which was the drawback of
application

specific networks, such as the traditional POTS network.



Have I somehow misunderstood the intent or benefits of the end-to-end

argument ?





Mark,



This is probably the most common misunderstanding of the end-to-end
principle out there. Someone else can dig up the quote, but
basically, the principle says that the network should not replicate
functionality that the hosts already have to perform. You have to
look at X.25's hop-by-hop data windows to truly grok this point.



Many people pick this up and twist it into ~the network has to be
application agnostic~ and then use this against NATs or firewalls,
which is simply a misuse of the principle. Really, this is a
separate principle in and of its own right. It's not one that I
subscribe to, but that's a different conversation...



Regards,

Tony