Subject: [Speermint] domain-policy-ddds-00: SPIT question

From: Otmar Lendl <[email-masked]>
Date: Wed, 22 Mar 2006 17:49:06 +0100

[I'm listening to the webcast from monday again, and try to
answer a few question that came up during the presentaion of
http://www3.ietf.org/proceedings/06mar/slides/speermint-3.ppt ]

On slide 2 we stated that some SIP networks do not want to
interconnect using the open Internet model (as in the email case)
because of the fear of SPIT.

Someone (I think Jonathan; the microphone discipline wasn't that good)
remarked that he doubts that anybody can claim to have solved the SPIT
problem. Thus, some clarifications:

* I'm not talking about RFC-compliant, open SIP servers 
  on the public Internet who are per definition interconnected. 
  IMHO they don't need speermint. I try to cover them as a 
  special case but they are not the focus of this draft.
  
  Please keep that in mind.

* There are VoIP carriers who use SIP internally but refuse to
  accept calls from anybody over the Internet because they fear
  SPIT.

* These VSPs *do* accept calls via the PSTN where there
  are solutions and policies in place which mitigate
  the problem of unsolicted calls. (DNC-lists, laws, tracking
  capabilities, ...)

* Thus: If we want to get such VSPs to peer with each other
  using SIP we have to give them the means to open up
  their networks in a controlled and selective way. 

  If it is a binary choice between "No IP-interconnect" and
  "accept calls from anybody on the Internet", then a
  significant number of VSPs will opt for "No IP-interconnect".

  Of course, manually configured peerings between two VSPs
  work in the meantime. But this runs into severe scalalibity
  problems very quickly.

* Thus: If we can offer a solution which enables them
  to control with whom they peer then the SPIT problem
  is manageable. After all, contrary to email, you can
  shut down a SIP peering without affecting reachability
  as the calls fall back to the PSTN.

  Example: If a VSP opens up his SIP proxy to the set of other
  VSPs with whom he already has a PSTN/SS7 interconnect, then he does
  not introduce a new vector for SPIT into his network.

  Or: To much SPIT coming in from $country? Drop the SIP
  peering and let them call you via PSTN.

The main difference to email is the following:

Email (at least on the Internet) started out as a fully connected
network: everybody talks to everybody. There is no backup if you block
a transmission. Spam-filters usually work by elimitating unwanted
communication.

Voice is different: A lot of people used SIP to build islands of VoIP
interconnected via the PSTN. For them, we're trying to establish direct
communication paths. SPIT is controlled by only opening up to explicitly
wanted communication partners.

Back to the $country example: You can't just tell your customers that you
won't accept any email from $country due to spam originating there,
but you don't need to tell your customers whether that caller from $country 
reaches you via SIP or the PSTN.

Summary:

* Jonathan (or whoever that was) is correct that this draft
  does not solve the SPIT problem for the open SIP proxy case.

* It is not designed to solve that problem. 

* It just offers a gradual path for SIP islands to start
  interconnecting to each other. SPIT is just one reason why 
  VSPs will want to have that capability.

There this still controversial?

If yes, which points are disputed?

/ol
-- 
< Otmar Lendl ([email-masked]) | nic.at Systems Engineer >

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