Subject: RE: [Ieprep] Diffserv Code Point for Emergency calls

From: "Reinaldo Penno" <[email-masked]>
Date: Sat, 22 Oct 2005 08:45:43 -0400

Your point is well taken James.

I guess the risk is no different from what we face nowadays with doom
packets marked with EF DSCP. The solution as well is no different from
what we have today to deal with those packets. Usually independently of
the DSCP an endpoint might put in a packet, the edge router perform
classification and if necessary remarks the packet with whatever DSCP it
should have. 

Therefore, if we just continue with just EF for normal and emergency
voice calls, the risk is the same, the drawback that I see is that we
cannot prioritize emergency over normal calls.

So, in general an edge device that can perform SIP parsing and mark
emergency calls with the emergency DSCP and others with EF DSCP.
Alternatively, in a decomposed gateway scenario the SIP Proxy can let
the router know that a certain call is an emergency and that it should
be marked differently.

Regards,

Reinaldo

> -----Original Message-----
> From: James M. Polk [mailto:[email-masked]]
> Sent: Friday, October 21, 2005 11:02 PM
> To: Reinaldo Penno
> Cc: ken carlberg; [email-masked]
> Subject: Re: [Ieprep] Diffserv Code Point for Emergency calls
> 
> Reinaldo
> 
> Adding fuel to a discussion that has churned on many lists over the
last
> several years, I'd really want to understand the threat anaylsis
observed
> by such a proposal (for a emergency DSCP) to ensure it could not be
used
> for a fairly trivial to generate DDOS on the network - even all the
way to
> the PSAP, or just used by neighbors wanting the very best throughput
for
> their game of Doom.
> 
> At 10:57 AM 10/21/2005 -0400, ken carlberg wrote:
> >Hello Reinaldo,
> >
> >>I read
>
>>http://www.ietf.org/internet-drafts/draft-ietf-ieprep-framework-10.txt
> >>and was somewhat puzzled at section 4.1.2. I understand that the
IETF
> >>wants to be conservative in standardizing new DSCP, but it seems to
an
> >>emergency call DSCP would be accepted by the community (am I
wrong?).
> >
> >well, from my own take, I would say that the "community" is not
> >against an emergency call DSCP per se, but rather awaits specific
> >proposals with a cautious mindset.  Recall from that section 4.1.2
> >that there is a need to define a behavior in addition to identifying
> >a code point.  So if you want a code point of 1 or more bits for
> >"emergency", what would be its defined forwarding behavior?
> >
> >one such proposal, primarily aimed at MLPP, is called Multi-Level
> >Expedited Forwarding (MLEF) and can be found at:
> >ftp://ftp.rfc-editor.org/in-notes/internet-drafts/draft-silverman-
> >tsvwg-mlefphb-03.txt
> >
> >I would also suggest reading a counter proposal that avoids defining
> >a new DSCP:
> >ftp://ftp.rfc-editor.org/in-notes/internet-drafts/draft-ietf-tsvwg-
> >mlpp-that-works-02.txt
> >you can dig around the TSVWG archives over the past 2 months for some
> >comments on the draft.
> >
> >-ken
> >
> >
> >_______________________________________________
> >Ieprep mailing list
> >[email-masked]
> >https://www1.ietf.org/mailman/listinfo/ieprep
> 
> 
> cheers,
> James
> 
>                                  *******************
>                  Truth is not to be argued... it is to be presented.

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---

From: "Steve Silverman" <[email-masked]>
Date: Sat, 22 Oct 2005 09:11:42 -0400

If calls to a locally pre-specified emergency number (e.g., 911) are
given high priority, it is no great exposure.
One would think such calls would have locally routable destinations
and couldn't travel very far or be used for DDOS attacks.  (Except
against the actual emergency systems. How we protect them is another
problem. )

In the absence of limited addressing or strong user authentication (as
the DOD uses) giving Joe Hacker the ability to get extra high priority
seems like a bad idea to me.

It would be helpful if someone (probably ITU rather than IETF) could
standardize on a limited number of local emergency calling numbers.

Steve Silverman

> From: [email-masked]
> [mailto:[email-masked]]On Behalf
> Of Reinaldo Penno
> Sent: Saturday, October 22, 2005 8:46 AM
> To: James M. Polk
> Cc: [email-masked]; ken carlberg
> Subject: RE: [Ieprep] Diffserv Code Point for Emergency calls
>
>

---

From: "James M. Polk" <[email-masked]>
Date: Sat, 22 Oct 2005 22:09:20 -0500

>given high priority, it is no great exposure.

"a locally pre-specified number".. hmmm

several comments:

- is a URI a number in this context?
         as SIP is defining a URI, not a number, for emergency calls

- How many routers that will have a PHB on this DSCP are between you and 
the local PSAP?
         could be 5, could be 10 - that impact is greater than the local 
Class 5 switch from old telco designs

- If you DDOS the local broadband segment, you eliminate the possibility of 
anyone on that segment from making a emergency call.
         single HFC segments can be as far away as 100 miles, is that local 
anymore?

>against the actual emergency systems. How we protect them is another

How do you protect a layer 3 packet that has a layer 3 marking and no 
authorization indication in that packet?

>standardize on a limited number of local emergency calling numbers.

see
http://www.ietf.org/internet-drafts/draft-ietf-ecrit-requirements-00.txt

cheers,
James

                                 *******************

---

From: "James M. Polk" <[email-masked]>
Date: Sat, 22 Oct 2005 22:22:58 -0500

>cannot prioritize emergency over normal calls.

so here's the problem as has been presented to me by both regulators and 
lawyers:

In larger emergencies, many people will likely be calling for emergency 
help, and some of them are not going to be calling (the equivalent of) 911, 
they will be calling their doctors directly - yet to "the system", these 
will appear as normal packets, or normal voice (EF marked) packets. In your 
pondering, these packets will be subject to some form of lesser treatment 
than perhaps the 10th or 100th call to 911, informing the PSAP of the same 
event (perhaps a building burning).

Here's the catch: who determined the 10th or 100th call to the PSAP is more 
important than the patient's call with their doctor - getting one-on-one 
advice/help.

I think the first lawsuit will stop that preferential treatment. I've had 
this hinted to me by many

>the router know that a certain call is an emergency and that it should

or there could be a path coupled mechanism for such calls, but that has its 
challenges too

cheers,
James

                                 *******************

---

From: Fred Baker <[email-masked]>
Date: Wed, 26 Oct 2005 14:59:05 -0400

From my perspective, the question in the data plane is not whether  
the packet is part of an emergency session, but whether it is  
authorized to use the bandwidth. Emergency authorization is a control  
plane problem.

That is why I have suggested authorization of users to use the EF  
code point during CAC.