Subject: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

From: RADHIKA.R.ROY at saic.com (Roy, Radhika R.)
Date: Thu, 7 Dec 2006 23:51:07 -0500

Issue is this: Mobile ad hoc network - no fixed infrastructure where
everything is P2P. No one knows who will be the next peer after a certain
period of time. The speed of each peer may vary.
 
DNS is used assuming that there is at least one fixed non-mobile node. It is
the problem that we want to get rid of.
 
First, let us understand what works in this environment.
 
IETF MANET WG has all the drafts and RFCs.
 
Best regards,
Radhika
 
PS: 
 
1. It is not about DNS or mDNS or multicasting per se.
2. Let us find our what works in the above environment, i.e., MANET.
Everything is distributive as P2P in mobile ad hoc environment. Period.
3. The routing protocol for MANET that will be used in the about environment
best commercially (to be accepted as standard soon as all alternative
protocols have provided their performance and simulations results, but this
is expected to be chosen as s finalist - draft is available in the IETF
MANET WG Archive): OSPFv3-MDR.
4. We may have to enhance the charter for the P2P-SIP in the future as the
present scope of this would be WG is not enough. However, it is a different
story as a first step let us accomplish what is in the present charter.

  _____  

From: David Barrett [mailto:dbarrett at quinthar.com]
Sent: Thu 12/7/2006 8:23 PM
To: 'Roy, Radhika R.'; 'Eunsoo Shim'
Cc: 'P2P-SIP'
Subject: RE: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

I'm not very familiar with MANET, but I think it supports multicast, so mDNS
could probably play a role in it.

Either way, if someone goes to the trouble of setting up some kind of
grid/mesh network, they'll probably want to do more than just VoIP.  They'll
need *some* kind of DNS to use for everything else.  It's probable they'll
find a way to tunnel normal DNS.  It's possible they'll find a way to use
normal mDNS.  Before inventing a custom, non-DNS solution, it seems sensible
to see how they're going to solve the DNS problem first and put our weight
behind that, rather than inventing a new, competing solution.

-david

PS: What is inadequate about DNS and mDNS for your network today?

  _____  

From: Roy, Radhika R. [mailto:RADHIKA.R.ROY at saic.com] 
Sent: Thursday, December 07, 2006 2:45 PM
To: David Barrett; Eunsoo Shim
Cc: P2P-SIP
Subject: RE: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

David:

Do DNS and mDNS also cover P2P Mobile Ad Hoc Networks (MANET)?

We are looking for MANET support right now for P2P-SIP networking.

Best regards,

Radhika

PS: We are using DNS right now, but no insufficient.

  _____  

From: p2p-sip-bounces at cs.columbia.edu on behalf of David Barrett
Sent: Thu 12/7/2006 4:37 PM
To: 'Eunsoo Shim'
Cc: 'P2P-SIP'
Subject: Re: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

Hm, I will agree that the conversation has covered all the useful ground
it's going to cover.  As for the confusions you raise:

-          DNS is used when available (internet or private network), and
mDNS otherwise (ad hoc subnet)

-          Multicast only works on subnets.  Ad hoc networks are typically
single-subnets.  Thus mDNS works on ad hoc networks.

-          Multicast does not work between subnets.  The internet and
private networks use multiple subnets.  Thus mDNS will not work across the
internet or on private networks spanning multiple subnets.  However, DNS is
typically available in this case, and thus DNS is used instead. 

-          DNS and mDNS cover the total range of real-world networking
environments.

-          I understand P2P-SIP is currently proposed to use DNS as an
optional extension to the mandatory DHT.  I think it'd be more sensible to
have mandatory support for DNS with optional DHT, particularly because the
DHT is hard work for no real-world gain and it seems wasteful to force
everyone to pay it.

-          The "P2P" system I propose as a replacement for DHT is merely
what Adam originally proposed: configure P2P-SIP UAs to update a DNS record
that points to another P2P-SIP UA as a proxy.  

-          Whether or not that is P2P "enough" is a long boring religious
discussion.  But so far as we've been able to determine, this solves all the
same use cases as the DHT, but with less work and better integration with
existing SIP.

-          P2P works; it's what pays my bills.  But it's a question of when
and where is appropriate.

Please let me know if you have any more questions about this idea or need me
to clarify it more, but I think we've covered it exhaustively.

-david

  _____  

From: Eunsoo Shim [mailto:eunsooshim at gmail.com] 
Sent: Thursday, December 07, 2006 4:12 AM
To: David Barrett
Cc: Peter Pan; Henning Schulzrinne; P2P-SIP
Subject: Re: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

mDNS works only in a subnet. If you limit P2PSIP applications only to that
environment, mDNS should work. You can go to SIPPING to talk about it. Many
of us understand it.
If you suggest mDNS even for other environments, please have the Internet
changed to support multicast almost everywhere first. Then we can talk about
using mDNS for P2PSIP in a general sense. 

dynDNS is just another DNS system, i.e. relying on DNS SERVERs. Using dynDNS
is same as retrieving a redirect server information from DNS and getting the
location of a particular user from the redirect server. That means, even we
don't have to update the DNS infrastructure! Just use existing DNS and SIP
and you can get what you propose.

You continuously try to imply that P2PSIP does not use DNS at all. I pointed
out that DNS was assumed for inter-domain connections for P2PSIP (and
actually SIP). All left from your argument is that we got to use DNS servers
even for intra-domain lookups, which is equivalent to using a central
location server. 

Now it sounds to me that you are saying "p2p does not work. Stick to central
servers!"
I have no interest in arguing whether C/S architecture or P2P architecture
is better. Neither are many people in this list, I believe. We understand
there are tradeoffs. Maybe you can enjoy that kind of discussion with people
from Skype or eDonkey. 

I think we passed already time for that kind of discussion here.

Already the current SIP systems use central servers for location
registration and voicemail storage. 
If you are interested in another way/protocol of using central servers for
SIP, this is not a right place to propose it. 
If you have a problem with DHT, please propose a different 'P2P' mechanism
for 'P2PSIP'.

Thanks.

Eunsoo

On 12/6/06, David Barrett <dbarrett at quinthar.com
<mailto:dbarrett at quinthar.com> > wrote:

I'm not sure the DNS infrastructure needs much updating at all.  Perhaps
there will be more demand for DNS registrars to offer automated (aka
"dynamic") record updating, but that's really just standardizing what they
already do.

As for voicemail, no, I wouldn't expect to put that into DNS; that's
something best handled by some real storage provider.  You *could* do it in
a DHT, but it'd just be slower and less reliable, and the engineering cost
of building that would pay for central storage many, many times over.

Again, in a vacuum without taking anything else into consideration, be it
engineering cost, performance, reliability, existing systems, standards
support and so on, yes, a DHT could be used.  But when everything else is
factored in, it just makes no sense at all.

-david

  _____  

From: Peter Pan [mailto:huang-ming.pan at comcast.net
<mailto:huang-ming.pan at comcast.net> ] 
Sent: Wednesday, December 06, 2006 12:09 PM
To: David Barrett; 'Henning Schulzrinne'
Cc: 'P2P-SIP'

Subject: Re: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

Great summary. Please see my feedback inline.

Peter

----- Original Message ----- 

From: David Barrett <mailto:dbarrett at quinthar.com>  

To: 'Henning Schulzrinne' <mailto:hgs at cs.columbia.edu>  

Cc: 'P2P-SIP' <mailto:p2p-sip at cs.columbia.edu>  

Sent: Wednesday, December 06, 2006 12:07 AM

Subject: Re: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

I think the value of this discussion is in identifying and clarifying
misimpressions about how DNS and mDNS work (and do not work) so we can make
a more informed choice on whether or not to use them.  Already we've
clarified:

How can DNS records be automatically updated? (Through dynamic DNS
protocols)

- [pp]: what is the cost and feasibility to upgrade existing DNS
infrastructure to support dynamic DNS globally? is it similiar to the
deployment of ipv6 and ip mobility?

- How fast can DNS propagate?  (Extremely fast with short TTLs)

- What if I have multiple SIP proxies? (Put multiple IPs into the DNS
record) 

Is DNS only for IP addresses? (No, can store other records) 

- [pp]: can/will these DNS server also store data like voicemail or other
p2p application data?

- How does DNS work in on ad-hoc networks? (Using mDNS via multicast) 

- Where is multicast supported? (Only everywhere it's needed - on subnets)

- Is mDNS an IETF standard? (It's on the standards track.)

- Is mDNS actually in use? (It's the foundation of zeroconf, which is used
extensively by Apple)

- Are there any use-cases that DHT supports that DNS/mDNS cannot?
(Apparently not.)

Lack of clarity on these points could call for the unnecessary dismissal of
these technologies on false premises, which I think nobody wants.

-david

  _____  

From: Henning Schulzrinne [mailto:hgs at cs.columbia.edu
<mailto:hgs at cs.columbia.edu> ] 
Sent: Tuesday, December 05, 2006 4:20 PM
To: David Barrett
Cc: 'Eunsoo Shim'; 'P2P-SIP'
Subject: Re: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

I have to admit that I'm confused by this whole discussion. I thought we had
agreement that

(1) specifying mDNS + SIP operation is useful (and hopefully simple), but
easily handled within the framework of SIPPING;

(2) specifying dynamic DNS + SIP might be useful, subject to working out
issues such as proxy discovery, authentication and the like and that
interested parties should work out, at least to the extent of identifying
the pieces that might need work (as a random example: can I expect my SIP
Digest secret to work as a DNS update secret?). If, as claimed, this is easy
to do, SIPPING is again the natural home for such a BCP effort, with the
DNS-related WGs as the home for any DNS extensions that might prove
necessary.

Maybe those individuals interested in solving (2) should form an informal
design team and get beyond the hand-waving stage and identify the problems,
if any, that would have to be addressed in either protocol or operational
standards. I have unfortunately seen little such effort so far, although I
suspect that such level of detail isn't terribly well suited to be hashed
out in front of several hundred mailing list members.

We also have had 2 BOFs and numerous ad-hoc meetings on this topic, with a
rough consensus on the current charter. Are you trying to keep people from
working on a specific topic you consider inferior?

We seem to be rehashing the same arguments again and again. 

Henning

On Dec 5, 2006, at 7:02 PM, David Barrett wrote:

Does the actual, real-world availability of multicast factor into the
decision as to whether or not to use it?

I mean, we *could* assume that every odd IP address won't work, and then
design around that.  But odd IP addresses *do* work.

Likewise, multicast *is* (or could easily be made) available for all of the
real-world use cases that demand it.

It just seems like there are much more interesting *actual* problems to
solve than those that don't affect real users.  But if you're excited about
solving the non-multicast ad-hoc P2P-SIP problem on the assumption that
someday, somebody will have reason to use it (even though we can't really
brainstorm anybody who would use it today), then I guess that's a cool
research project.

But it's a *research* project, not an IETF standardization exercise.  DNS
and mDNS work everywhere the *actual* users are, and thus I think the IETF
should focus on them, first.

-david

  _____  

From: Eunsoo Shim [ mailto:eunsooshim at gmail.com
<mailto:eunsooshim at gmail.com> ] 
Sent: Tuesday, December 05, 2006 3:04 PM
To: David Barrett
Cc: P2P-SIP
Subject: Re: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

I understand that mDNS can be used in ad-hoc networks where multicast works.
Some of us, including me, have discussed about using mDNS and noticed that
there is little to do to use mDNS or any other multicast-based discovery
protocol. 
Those people decided not to focus on the approach because assuming multicast
availability was not general and they did not want to limit P2PSIP into such
network environments.
They said such an approach (using mDNS or similar ones) could be discussed
maybe in SIPPING. 

The proposed charter is targeting to address intra-domain lookup that works
even if there is no multicast support.

Using DNS for intra-domain lookup is not different from using a central
server, which is not interesting to many of us, I believe. So transition
from mDNS to DNS is not appealing, either. 

What do you say?
Thanks.

Eunsoo

On 12/5/06, David Barrett <dbarrett at quinthar.com
<mailto:dbarrett at quinthar.com> > wrote: 

  _____  

From: Eunsoo Shim 
Subject: [p2p-sip] DNS for inter-domain? Yes; intra-domain? No

So my understanding is that what P2PSIP group is trying to do is designing
mechanisms for P2P-style intra-domain location lookup where location records
are distributed among peers rather than in a central location server.

...

Am I missing any important aspect?

I agree, this is what P2P-SIP is trying to do.  I'm just not certain why,
because mDNS can do the same thing in a way that is already standardized,
already deployed, and already works.  Basically, for every real-world case,
it seems mDNS is adequate for ad-hoc unauthenticated namespaces, and DNS is
adequate for global, authenticated namespaces.  There is already a seamless
interface to graduate from mDNS to DNS depending upon what is available; it
already covers the whole range of use cases (minus the extreme security
cases, which I believe remain unsolved problems by any means).

I don't dispute you could make a DHT bootstrapped with UPnP or whatever.
You can build a lot of things.  I just don't see why we should bother when
there are easier, adequate technologies available.

-david

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---

From: dbarrett at quinthar.com (David Barrett)
Date: Fri, 8 Dec 2006 00:37:06 -0800

I'm not sure I follow you here.

The "m" in "mDNS" stands for multicast because you send your DNS requests to
a multicast channel instead of to a fixed DNS server.  Anyone who knows the
answer broadcasts a reply.  It's designed precisely for an ad hoc network
with no fixed nodes.

Does this address your concern?

-david

> -----Original Message-----
> Sent: Thursday, December 07, 2006 8:51 PM