IPv6 news

Tony Li tony.li at tony.li
Sun Oct 16 08:45:40 UTC 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




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