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

From: [email-masked]
Date: Tue, 1 Nov 2005 22:32:16 +0200

Hi,

A couple of points:
- This is getting a bit outside the scope of SIP, but: in some radio technologies, the terminal can actually go into some sort of dormant mode, where it only listens to some sort of paging/wake-up channel, and this consumes quite little energy. Even when the terminal only receives something, it has to switch from the dormant mode to active, and if this happens every 15 sec., it most likely has some impact on the battery life. In some other radios you don't have that type of operation at all, i.e. they are actively receiving constantly. For them the impact of just receiving packets is not that big, but in general the power consumption of those type of radios is anyway much bigger. For laptops this is not anymore such an issue, but it is still for handheld devices.
- Hopefully some NAT expert can answer: Is inbound traffic enough to keep a binding alive in all kinds of NATs, or are there also some where only outgoing packets actually refresh the binding?

Markus 

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On
> Behalf Of ext Juha Heinanen
> Sent: 01 November, 2005 12:23
> To: [email-masked]
> Subject: RE: [Sipping] Making SBCs more transparent for NAT traversal
> 
> 
> Juha Heinanen writes:
> 
>  > there is very little ietf can do about that.  if it is unfeasibly
>  > expensive or power consuming to keep nat binding open by 
> minimal size
>  > udp packets @ every 15 sec, then there is something wrong with the
>  > pricing models and/or the technology.
> 
> i would just like to clarify that it is the proxy that sends the udp
> packets send to keep the nat binding alive.  the mobile terminal only
> needs to RECEIVE them, not send anything unless there is real 
> sip/media
> traffic flow.
> 
> radio on my desk runs on same batteries for months and it even has
> amplifier in it.  so there should be no power issue with mobile
> terminals with the keepalives unless the their radio protocol 
> is really
> screwed up.
> 
> -- juha
> 
> _______________________________________________
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> This list is for NEW development of the application of SIP
> Use [email-masked] for questions on current sip
> Use [email-masked] for new developments of core SIP
> 

_______________________________________________
Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
Use [email-masked] for new developments of core SIP

---

From: "Henry Sinnreich" <[email-masked]>
Date: Wed, 2 Nov 2005 10:25:19 -0600

Markus,

I don't think you want to make the argument that mobile devices are so
crippled that they can work only using SBCs?

Thanks, Henry

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of [email-masked]
Sent: Tuesday, November 01, 2005 2:32 PM
To: [email-masked]; [email-masked]
Subject: RE: [Sipping] Making SBCs more transparent for NAT traversal

Hi,

A couple of points:
- This is getting a bit outside the scope of SIP, but: in some radio
technologies, the terminal can actually go into some sort of dormant mode,
where it only listens to some sort of paging/wake-up channel, and this
consumes quite little energy. Even when the terminal only receives
something, it has to switch from the dormant mode to active, and if this
happens every 15 sec., it most likely has some impact on the battery life.
In some other radios you don't have that type of operation at all, i.e. they
are actively receiving constantly. For them the impact of just receiving
packets is not that big, but in general the power consumption of those type
of radios is anyway much bigger. For laptops this is not anymore such an
issue, but it is still for handheld devices.
- Hopefully some NAT expert can answer: Is inbound traffic enough to keep a
binding alive in all kinds of NATs, or are there also some where only
outgoing packets actually refresh the binding?

Markus

---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 02 Nov 2005 12:05:16 -0500

inline.

[email-masked] wrote:

> - Hopefully some NAT
> expert can answer: Is inbound traffic enough to keep a binding alive
> in all kinds of NATs, or are there also some where only outgoing
> packets actually refresh the binding?

Actually, you want outbound packets. Note the following in the 
behave-udp spec:

  REQ-6: The NAT mapping Refresh Direction MUST have a "NAT Outbound
       refresh behavior" of "True".
       a) The NAT mapping Refresh Direction MAY have a "NAT Inbound
          refresh behavior" of "True".

    Justification: Outbound refresh is necessary for allowing the client
       to keep the mapping alive.
       a) Inbound refresh may be useful for applications with no outgoing
          UDP traffic.  However, allowing inbound refresh may allow an
          application to keep a mapping alive indefinitely.  This may be
          a security risk.  Also, if the process is repeated with
          different ports, over time it could use up all the ports on the
          NAT.

So, this would be an issue for wireless devices.

Mike Hammer asked:
> Is there a dependency here on the type of NAT and which side is inside
> v. outside?
> Are all NATs in question under SP control?

I think the much more interesting cases are those where it is not. The 
use case for such a thing is when the consumer buys a nat where the 
uplink to the Internet is via 3g wireless (i.e, EV-DO or UMTS or 
something like that). The nat then offers local wifi, over which 
softphones or even dual-mode cellular/wifi devices (in wifi mode) connect.

Such dual-mode devices through a big wrench into the perspective that 
client behavior should be specific to "wireless" as opposed to 
traditional wired broadband access.

There could also be nat in the SP network.

Thanks,
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

---

From: Juha Heinanen <[email-masked]>
Date: Thu, 3 Nov 2005 08:17:42 +0200

>           refresh behavior" of "True".

my claim is that this requirement is bogus.  our users have a large
number of different kinds of nats and no-one has yet complained about
ineffective inbound refresh.  there may very well be such nats, but it
is an overkill to require that they MUST be supported.

-- juha