[Freeswitch-users] Best practices question about SIP registration

[Sean Devoy]

Great info Lawrence, especially the MX analogy.  Thanks.

I have to take this one more step and ask a question.  We have FS configured
for multitenant.  Of course the "domains" for the tenants are FQDNs.  I
found it simple to setup and wonderful for setting up customers as their own
virtual switches.

Clearly this is a case where the sip address has to contain the FQDN. (It
also gives me a chuckle every day when I see those a-holes'  registration
failures for "100@<ip address>" when a name is required!)

My FS Domains are like "fs_A.xyz.com" and "FS_B.xyz.com" which I currently
have as A records with the same IP address.
If I add an SRV record for _sip._udp.xyz.com to that IP Address, are you
saying I won't need the A records? Or do I need SRV records for each
sub-domain?

Of course this is assuming I set my hardware (Cisco SPA 5xx) to "Use SRV?
Yes"

Thanks for the information.

Sean

-----Original Message-----
From: freeswitch-users-bounces at lists.freeswitch.org
[mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Lawrence
Conroy
Sent: Tuesday, January 08, 2013 7:05 PM
To: FreeSWITCH Users Help
Subject: Re: [Freeswitch-users] Best practices question about SIP
registration

Hi again Steven,
 with apologies for top-posting ...
Re. flowroute.com
Many of us have sup-domains for different classes of users -- looks like
your sub-domain is sip.flowroute.com.

However, flowroute.com does have a NAPTR (it has two):
;; ANSWER SECTION:
flowroute.com.		21600	IN	NAPTR	100 10 "s" "SIP+D2U" ""
_sip._udp.flowroute.com.
flowroute.com.		21600	IN	NAPTR	102 20 "s" "SIP+D2T" ""
_sip._tcp.flowroute.com.

Also, the _sip._udp.flowroute SRV shows:
;; ANSWER SECTION:
_sip._udp.flowroute.com. 43200	IN	SRV	20 10 5060
sip-ca1.flowroute.com.
_sip._udp.flowroute.com. 43200	IN	SRV	10 10 5060
sip-nv1.flowroute.com.

as does the _sip.tcp.flowroute.com SRV:
;; ANSWER SECTION:
_sip._tcp.flowroute.com. 43200	IN	SRV	10 10 5060
sip-nv1.flowroute.com.
_sip._tcp.flowroute.com. 43200	IN	SRV	20 10 5060
sip-ca1.flowroute.com.

so -- if a client is trying to call to sip:1000 at flowroute.com, that client
looks up the NAPTR set for flowroute.com (the sip domainpart), gets back the
two entries, and chooses to look for a SRV under _sip._udp.flowroute.com (if
it wants to call using UDP) or _sip.tcp.flowroute.com (if it wants to call
using TCP or use sips:).
flowroute would prefer that you contacted them by UDP (it has a lower
preference -- 10 versus the D2T's 20).
If you do contact them, they'd prefer that you used sip-nv1.flowroute.com.
(as that has a better/lower preference than sip-cal).

On to the polycoms -- I don't have any of these, so I'm guessing, but ...
It looks strongly like the registration server is at fs.domain.local, which
has an IP address of 10.10.10.11 for the DNS-challenged, and is listening on
port 5060.
The AuthID/UserID for this 'phone to use 1000, which is kinda apparent from
the SIP address the phone has, which is sip:1000 at fs.domain.local.
I'd AssUMe that there's also a password field :).

So ... if you had mydomain.com, and for your internal use you had a
sub-domain of, say, internal.mydomain.com, and you had one fS handling your
local 'phones, running on a machine called fs.internal.domain.com which had
an IP address of 10.10.10.11, I'd put into the local view of DNS:

internal.mydomain.com. IN NAPTR 100 10 "s" "SIP+D2U" ""
_sip._udp.internal.mydomain.com.
_sip._udp.internal.mydomain.com. IN SRV 10 10 5060 fs.internal.mydomain.com
fs.internal.mydomain.com. IN A 10.10.10.11

Note that I'm assuming that you'd be using a split-view DNS (i.e., your
local DNS server would only give these answers to its local machines) as
it's kinda impolite to give private addresses like 10.10.10.11 to the
outside world -- clients are sometimes too dumb to realise they can't
contact that server using this address.
[...which is why we have one way audio -- stupid implementers :]p

Hope that helps,
  Lawrence

On 8 Jan 2013, at 23:02, Steven Schoch wrote:
> On Tue, Jan 8, 2013 at 1:56 PM, Lawrence Conroy
<lconroy at insensate.co.uk>wrote:
> 
>> Hi there,
>> at the risk of butting in on someone else's party ...
>> Nope; your interpretations is NOT best practice.
>> 
> 
> This party is open to all.  I appreciate these answers, and as usual I 
> have noticed that the fastest way to learn is to do it wrong, and then 
> have somebody correct me!  Thanks!
> 
> 
>> With SIP (see RFC 3263), you do a lookup on the SRV record (at
>> _sip._udp.<sipdomain>) to find the machine that handles SIP 
>> registrations/incalls for the domain. That also gives you the port on 
>> which that machine is listening.
>> 
> 
> For example, I did a lookup:
> 
> $ dig SRV _sip._udp.sip.flowroute.com.
> 
> This returns:
> 
> _sip._udp.sip.flowroute.com. 43200 IN   SRV     20 10 5060
> sip-ca1.flowroute.com.
> _sip._udp.sip.flowroute.com. 43200 IN   SRV     10 10 5060
> sip-nv1.flowroute.com.
> 
> 
> 
>> (Yup, you can also have a NAPTR record in the domain to tell you 
>> where the SRV record is, but many folks don't bother -- for Best 
>> Practice, you should, but ...)
>> 
> 
> $ dig NAPTR sip.flowroute.com
> 
> sip.flowroute.com.      42818   IN      NAPTR   100 10 "s" "SIP+D2U" ""
> _sip._udp.sip.flowroute.com.
> sip.flowroute.com.      42818   IN      NAPTR   102 20 "s" "SIP+D2U" ""
> _sip._tcp.sip.flowroute.com.
> 
> I found that _sip._tcp.sip.flowroute.com does not have a SRV record.  
> I don't know what that means.  The RFC says that you should use 
> "SIP+D2T" for TCP.
> 
> Now, as this relates to the Polycom phone example, there are these fields:
> 
>    reg.1.address="1000 at fs.domain.local"
>    reg.1.auth.userId="1000"
>    reg.1.server.1.address="10.10.10.11"
>    reg.1.server.1.port="5060"
> 
> Since this is a VoIP phone that loads its configuration from the 
> server, not VoIP software that is configured by the user, it really 
> only needs the IP address, so the server address field is kind of moot.
> 
> But the example domain here is "fs.domain.local".  Why not just 
> "domain.local"?  Why didn't Flowroute use "flowroute.com" instead of "
> sip.flowroute.com"?
> 
> And my other question was how is the address "1000 at fs.domain.local" used?
> Does FreeSwitch use that or does it just use the auth.userId?
> 
> --
> Steve
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>  
> 
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