Subject: RE: [Sipping] Comments on draft-peterson-sipping-ieprep-00

From: "Peterson, Jon" <[email-masked]>
Date: Thu, 13 Mar 2003 13:43:24 -0500

> From: King, Kimberly S. [mailto:[email-masked]]
> 
[snip]
> 
> Suppose there are Internet Telephony Service Providers (or cable operators
> offering telephony services) that are willing to modify gateways to the
PSTN
> to provide preferential access for authorized users.  The idea would be in
> times of gateway congestion, authorized users might have advantage in
> obtaining resources.  If the providers run stateful proxies, those proxies
> could also favor authorized users.  To receive preferential treatment,
> authorized users must be customers of these particular providers.  Isn't
> this partial ETS coverage potentially useful?
> 

This is useful for combatting gateway congestion, yes. If the reality is
that congestion is more likely to arise in other parts of the system (like,
the access links), then alleviating congestion at gateways is unlikely to
increase the overall odds of call completion significantly. If odds are that
you will never be able to get to the gateways, then managing gateway
congestion will make little difference; we need to know if the interposition
of one administrative domain that does not support ETS in a call's path
crushes the odds that calls will complete reliably in emergencies. This is
the sort of analysis that needs to be done. 

I agree that managing gateway congestion by routing prioritized calls to
reserved emergency gateways is realistic. But if it turns out that this is
the only aspect of managing prioritization that is actually realistic, then
that tells us something about the mechanism (for one thing, that all SIP
calls whose priority can be managed would have telephone numbers in their
Request-URI). This could have significant ramifications for the ongoing
design work.

> If some government wanted to create a priority scheme over its own
priviate
> network (e.g., MLPP/Assured Service over government owned network) then is
> that reasonable?
> 

On totally private networks, I find the whole ETS SIP concept entirely
plausible. I would note that the "I" in "IEPREP" is for Internet, though. I
have always understood that to be the capital-"I" Internet, as in RFC3271.

> Some people from the NGN PSTN camp are thinking about priviate packet
> networks for telephony.  They envision trading traffic with their peers in
a
> manner mirroring their current methods.  (For example, see 
> http://www.msforum.org/techinfo/reports/MSF-TR-QoS-001-FINAL.pdf )
> Suppose the majority of ETS locations used a handful of providers and
those
> providers traded traffic as in the MSF report augmented with ETS support.
> Given the assumed architecture, would this partial ETS coverage be
> potentially useful?  
> 

This concept of 'partial' is slightly different than the one I was
suggesting for further analysis. I think this 'partial ETS coverage'
suggests partial deployment of ETS in the world, but in deployments such
that, within controlled environments, it is possible to have ETS support
end-to-end. The 'partial' ETS I'm concerned with is the specific effects of
partial support of ETS in a particular call path (which is, among other
things, the motivation for wanting ETS to propagate through unaware networks
- unaware networks would constitute a segment of the call path in which ETS
is not supported).

And again, private packet networks are not the native environment for SIP -
nor would I have thought that they were the only meaningful customer of
IEPREP. The MSF architecture specified by the document referenced above
relies on numerous assumptions that are not general Internet tenets. That
much said, these private networks are not harmful to the Internet, they are
potentially useful, and so on. However, I don't think any ETS system that
relied exclusively on the traversal such networks would be a general
solution for Internet emergency preparedness. 

Jon Peterson
NeuStar, Inc.

> Is this the type of analysis you seek for partial ETS coverage?  
> 
> Kimberly
> 
> 
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---

From: Henning Schulzrinne <[email-masked]>
Date: Thu, 13 Mar 2003 16:02:29 -0500

At least my impression from the IEPREP discussion was that access link 
congestion is an important factor, but that it is a separable concern. 
For that, indications and reservations at the IP layer seem like the 
more appropriate consideration, which seem pretty far afield from SIP 
territory.

> the sort of analysis that needs to be done. 

I just don't see you we can "analyze" this, since there is no real data 
on access link congestion in the places where people would like to place 
ETS calls. At least on 9/11 (and, I believe, during most disasters where 
ETS was used, such as the various earthquakes in CA), Internet traffic 
volume wasn't significantly higher than usual, but all such past events 
took place in an environment where few people used the Internet for 
real-time communications.

How do you propose to arrive at an analysis?

> Request-URI). This could have significant ramifications for the ongoing

They might have phone numbers before they hit the gateway, but they may 
well have 'regular' SIP URIs at the origin, translated by some proxy or 
B2BUA.