Re: [BEHAVE] (no subject)

It seems worthwhile to differentiate home router NAT implementations from enterprise/SP router NAT implementations. And the question to ask ourselves is whether we need a common set of requirements for both scenarios !!

Cheers,
Rajiv

> -----Original Message-----
> From: behave-bounces@ietf.org [mailto:behave-bounces@ietf.org] On
> Behalf Of ivan c
> Sent: Tuesday, June 18, 2013 4:33 PM
> To: Senthil Sivakumar (ssenthil)
> Cc: Behave
> Subject: Re: [BEHAVE] (no subject)
> 
> Hi Senthil,
> 
> Thanks for your message. You might want to read
> http://tools.ietf.org/html/draft-ietf-behave-requirements-update-00
> It features the list of updates to the existing RFC, adapted to new usage
> contexts such as CGNs, mobile networks, etc.
> 
> 
> On Tue, 18 Jun 2013 19:24:50 +0000, "Senthil Sivakumar (ssenthil)"
> 
> >>
> >>Are you talking about UDP port preservation?
> >
> > Both TCP & UDP. The latest implementation in some router families is not
> > to have port preservation
> > (for both TCP & UDP).
> >
> 
> The discussion here is not about UDP. UDP port preservation should
> generally not be implemented by NATs, as it could generate conflicts when
> 2
> internal hosts using the same local port, each with a session to the same
> endpoint. This would break end-to-end connectivity in rare cases, as there
> is no fallback mechanism (as opposed to TCP).
> 
> To be clear, the requirements are as follows:
> * NAT SHOULD NOT use UDP port preservation
> * NAT SHOULD use TCP port preservation
> 
> Here are some NATs that have been tested and implement TCP port
> preservation:
> in the UK:
> BT (British Telecom) (house-made gateway) - number 1 provider
> Virgin (house-made gateway) - number 2 provider
> Sky (Sagemcom) - number 3 provider
> 
> in France:
> Orange (Livebox) (house-made gateway) - number 1 provider
> Free (Freebox) (house-made gateway) - number 2 provider
> SFR/Neuf (Neufbox) (house-made gateway) - number 3 provider
> 
> This covers the overwhelming majority of subscribers.
> 
> We have the same results in Spain in Italy.
> 
> Misc:
> Linksys E1200, latest generation.
> Netgear, various models
> 
> 
> It is difficult to find any NAT that does *not* implement TCP port
> preservation in these countries.
> If you think some gateway implementations have dropped TCP port
> preservation, you need to substantially support your claim by a reference.
> We are not aware of anything that would support it.
> 
> 
> >
> > Most of the NATs that I know don’t do port overloading any more.
> > RFC 5382 also says,
> > REQ-7:  A NAT MUST NOT have a "Port assignment" behavior of "Port
> >       overloading" for TCP.
> >
> 
> This is the purpose of the new draft
> http://tools.ietf.org/html/draft-ietf-behave-requirements-update-00 , to
> make the use case for port overloading, as it is needed in CGNs. It wasn't
> needed nearly as much in 2005 when RFC 5382 was first written.
> 
> REQ-7: A NAT MUST NOT have a "Port assignment" behavior of "Port
> overloading" for TCP
> is too stringent, as proved in my earlier message and in the
> draft-ietf-behave-requirements-update-00, and not needed.
> 
> Port overloading is perfectly acceptable when the remote endpoints are
> distinct, as it preserves the uniqueness of the 5-tuple.
> 
> As a result, REQ-7 must be corrected.
> 
> 
> 
> --
> _Ivan Chollet_
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