Re: [pcp] TR: I-D Action: draft-boucadair-pcp-sip-ipv6-00.txt

["Tirumaleswar Reddy (tireddy)" <[e-mail]>]

> -----Original Message-----
> From: Sebastian Kiesel [mailto:[e-mail]]
> Sent: Monday, August 26, 2013 11:29 PM
> To: Tirumaleswar Reddy (tireddy)
> Cc: [e-mail]; [e-mail]
> Subject: Re: [pcp] TR: I-D Action: draft-boucadair-pcp-sip-ipv6-00.txt
> 
> Hi,
> 
> On Fri, Aug 23, 2013 at 12:34:02PM +0000, Tirumaleswar Reddy (tireddy) wrote:
> > > -----Original Message-----
> > > From: Sebastian Kiesel [mailto:[e-mail]]
> > > Sent: Tuesday, August 20, 2013 2:03 AM
> > > To: [e-mail]
> > > Cc: [e-mail]
> > > Subject: Re: [pcp] TR: I-D Action: draft-boucadair-pcp-sip-ipv6-00.txt
> > >
> > > Hi,
> > >
> > > On Wed, Jun 26, 2013 at 05:04:52PM +0200, [e-mail]
> wrote:
> > > > Dear all,
> > > >
> > > > I submitted this short I-D to explain how PCP can be used in IPv6 SIP
> > > deployments (with a focus on the managed networks case).
> > >
> > > > Objet: I-D Action: draft-boucadair-pcp-sip-ipv6-00.txt
> > >
> > > I have read this draft and I think this is a very interesting topic.
> > > However, it is not very clear to me what the key message of this draft is.
> > >
> > > I think there are at least two topics that deserve investigation and
> > > discussion, with different target audiences:
> > >
> > > 1. A gap analysis for PCP, i.e., tell the PCP folks what should be
> > > changed or added to PCP to better support this use case (if any).
> > >
> > > 2. Tell the SIP folks about PCP and its benefits. IMO this chapter
> > > should start with a short discussion what's new compared to older
> > > (managed) NAT/Firewall traversal approaches, e.g., MIDCOM [RFC5190,
> > > RFC4540] and NSIS [RFC5973]. Is the interaction really straightforward,
> > > or are there any pitfalls (e.g., [draft-kiesel-mmusic-firewall-sip-00]) to
> > > consider?
> >
> > The problems discussed in draft-kiesel-mmusic-firewall-sip-00 can also
> > be addressed using PCP
> > http://tools.ietf.org/html/draft-wing-pcp-third-party-authz-00; we
> > have taken example of WebRTC in the draft to explain the problems and
> > solution.
> 
> 
> I wouldn't say that draft-wing-pcp-third-party-authz-00 addresses the
> problems identified in draft-kiesel-mmusic-firewall-sip-00 - it's more
> like it avoids them by using a rather different solution approach, which
> might have other drawbacks.
> 
> Once upon a time some people thought that with MIDCOM, a SIP B2BUA would
> be able to control a firewall on the RTP media path, completely
> transparent for the user agents.  

Yes, PCP solves that problem using PCP THIRD_PARTY option (http://tools.ietf.org/html/rfc6887#section-13.1), where SIPB2BUA can act as PCP client.

But for scenarios where the Application Server is outside the site (for example over-the-top services) it will not be able to use PCP THIRD_PARTY option, draft-wing-pcp-third-party-authz-00 is targeted to such use cases to solve both Firewall and QOS problems (http://tools.ietf.org/html/draft-penno-pcp-mobile-qos-00) 

> draft-kiesel-mmusic-firewall-sip-00
> summarizes problems with that approach and argues that at least for the
> handling of error conditions there must be some limited support in the
> user agents. Adding a PCP client to the SIP phone avoids these problems,
> but seems to be more, not less, additional effort.
> 
> 
> Sebastian
> 
> 
> p.s.: speaking of draft-wing-pcp-third-party-authz-00: this draft could
> be improved by explaining more explicitly how Figure 1 is related to
> Figure 3.  

Sure, will update in the next version of the draft.

> Specifically, what is the relation between "WebRTC Server"
> and "Authorization Server" ?

PCP client is host (Alice); PCP server is PCP-controlled firewall; Authorization server is WebRTC Server.

--Tiru.