Subject: RE: [Sipping] Making SBCs more transparent for NAT traversal

From: "Christer Holmberg (JO/LMF)" <[email-masked]>
Date: Fri, 4 Nov 2005 14:19:40 +0100

Hi, 

>>How does the NAT know which packages are "keepalive" ones?
> 
>you could standardize it if it is not obvious otherwise. but 
>perhaps you prefer much more complex solutions for nat traversal.

I didn't say that. 

I asked how the NAT would know which packages are "keepalive" ones. Even
if you standardize some kind of "keepalive protocol", the NAT still only
sees IP packages, doesn't it?

Regards,

Christer

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From: Aki Niemi <[email-masked]>
Date: Fri, 04 Nov 2005 15:31:31 +0200

> sees IP packages, doesn't it?

My guess is the cleverness would be something like assuming empty UDP 
packets are keepalives, or similar such guesses.

However, this is where things usually go horribly wrong. I've seen 
people spend hours and hours debugging what later turns out to be a 
firewall being "clever".

Cheers,
Aki

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From: Juha Heinanen <[email-masked]>
Date: Sat, 5 Nov 2005 03:50:47 +0200

> sees IP packages, doesn't it?

i was talking about mobile operator NAT that usually is bundled with
GGSN.  sure ericsson and nokia must be able to implement such a NAT, if
you are able to implement IMS.

-- juha

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From: Juha Heinanen <[email-masked]>
Date: Sat, 5 Nov 2005 03:52:18 +0200

> people spend hours and hours debugging what later turns out to be a 

as i told, you would advertise to your customers that this APN is such
that it prevent needed packets over air interface by absorbing keepalive
packets.   that is all.

-- juha

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From: Jonathan Rosenberg <[email-masked]>
Date: Sun, 06 Nov 2005 17:21:53 -0500

I think there are several NAT scenarios that require consideration for 
wireless. The more interesting one IMHO is a customer owned nat. I 
posted a note previously on this situation. Its not theoretical either - 
there are shipping products doing this.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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From: Juha Heinanen <[email-masked]>
Date: Mon, 7 Nov 2005 15:03:53 +0200

> there are shipping products doing this.

i agree that customer owned nat behind mobile terminal is not
theoretical issue.  i just claimed that if there is a network behind the
terminal, it is highly likely that there is also other power source than
battery available for the mobile phone.  

the argument that keepalive packets would be too expensive i don't,
however, buy.  if they are then the network is useless also for many
other applications and thus irrelevant.

-- juha