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Unread 02-17-2009, 03:13 AM   #11
boatman
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Twinkle is a softphone for Linux. I was testing to 214880@200.56.193.12:5060, not using voxalot. It looks like you are not using the GF210 at this time. Whichever UA you are using sent me the following packet:

SIP/2.0 200 OK
Via: SIP/2.0/UDP 98.246.79.161;rport=1024;branch=z9hG4bKwnyaynzd
From: "boatman" <sip:boatman@proxy01.sipphone.com>;tag=xypvh
To: <sip:214880@200.56.193.12:5060>;tag=186704036
Call-ID: vvgfdtgdjudhyuo@localhost
CSeq: 570 OPTIONS
Allow: INVITE, ACK, OPTIONS, CANCEL, BYE, SUBSCRIBE, NOTIFY, MESSAGE, INFO, PRACK
Content-Length: 0

Note the rport=1024, it should be rport=5060 as I am using 5060 as my SIP port.
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Unread 02-17-2009, 09:04 AM   #12
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Quote:
Originally Posted by boatman View Post
Note the rport=1024, it should be rport=5060 as I am using 5060 as my SIP port.
That's true only if your NAT device preserves the port numbers.
In your case I suspect your NAT device have random port algorithm.
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Unread 02-17-2009, 05:59 PM   #13
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In my case I have forwarded port 5060, so my SIP port is 5060 on both sides of my NAT router.

I can think of two possible reasons why the remote SIP user agent would return rport=1024. Either the device has faulty software/firmware, or there is an intervening router changing the source port number before it reaches the remote SIP user agent.

Last edited by boatman; 02-17-2009 at 06:26 PM.
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Unread 02-17-2009, 06:45 PM   #14
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Quote:
Originally Posted by boatman View Post
In my case I have forwarded port 5060, so my SIP port is 5060 on both sides of my NAT router.
Not exactly. You have no control on the WAN side of your NAT router.
External port will be selected by the router on it's own, basing on it's internal algorithm. It will be either the same as the private source port (port is preserved) or it will be randomly chosen (port is random).
Port forwarding simply gives you some freedom. You may use any port number in your Contact field for example; as soon as this port is forwarded the incoming request will come through, regardless of the router's dynamic NAT mapping.
You may have 5060 locally, and your router will randomize it and map to something like 12345 then proxy will see your requests coming from 12345 and not 5060 and your NAT router will allow incoming traffic on WANaddr:12345 only and not on WANaddr:5060 .
If your SIP UA is not aware of the router's behavior it may put port 5060 instead of 12345 into the Contact header for example. If this will happen you will be able to receive incoming calls only if you will configure port forwarding for 5060.

Quote:
I can think of two possible reasons why MarkosJal's SIP UA would return rport=1024. Either the device has faulty software/firmware, or there is an intervening router changing the source port number before it reaches the GF210.
There is no problem with either SIP UA or router.
SIP UA is not returning rport=1024, provider's proxy is doing that! SIP UA is only indicating it's capabilities using rport with no value.

"A client, compliant to this specification (clients include UACs and
proxies), MAY include an "rport" parameter in the top Via header
field value of requests it generates. This parameter MUST have no
value; it serves as a flag to indicate to the server that this
extension is supported and requested for the transaction."

rport= is always returned by the proxy, indicating the port number the packet really came from:

"When a server compliant to this specification (which can be a proxy
or UAS) receives a request, it examines the topmost Via header field
value. If this Via header field value contains an "rport" parameter
with no value, it MUST set the value of the parameter to the source
port of the request."

Please refer to RFC 3581 - An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing

Last edited by green; 02-17-2009 at 06:56 PM.
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Unread 02-17-2009, 07:46 PM   #15
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Quote:
Originally Posted by green View Post
Not exactly. You have no control on the WAN side of your NAT router. External port will be selected by the router on it's own, basing on it's internal algorithm. It will be either the same as the private source port (port is preserved) or it will be randomly chosen (port is random).
None of my NAT routers change the port number when the port has been forwarded, they all preserve the port number. My "from port" is 5060 on both sides of my router. It's easy to check using Wireshark, or I can look at the rport response from any normal SIP UA.

Quote:
Originally Posted by green View Post
There is no problem with either SIP UA or router.
SIP UA is not returning rport=1024, provider's proxy is doing that! SIP UA is only indicating it's capabilities using rport with no value.
During my test there were no packets sent to or from any proxy, it was a direct connection between my UA and that of MarkosJal.
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Unread 02-17-2009, 08:07 PM   #16
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Quote:
Originally Posted by boatman View Post
During my test there were no packets sent to or from any proxy, it was a direct connection between my UA and that of MarkosJal.
Are you familiar with the SIP terminology? UAC? UAS?

Please refer to the RFC 3261:
"User Agent Server (UAS): A user agent server is a logical entity
that generates a response to a SIP request. The response
accepts, rejects, or redirects the request. This role lasts
only for the duration of that transaction. In other words, if
a piece of software responds to a request, it acts as a UAS for
the duration of that transaction. If it generates a request
later, it assumes the role of a user agent client for the
processing of that transaction."

This was already quoted from RFC 3581:
"When a server compliant to this specification (which can be a proxy or UAS)... it MUST set the value of the parameter to the source port of the request"

This means that MarkosJal's UA sent you rport=1024 while that UA played a role of UAS.

Do you think his UA is reporting incorrect information?

The best way to identify OP's problem will be to analyze SIP debug on Voxalot side. Without this we can only guess.
We can try to observe the signaling with another SIP server but this will not give us the complete picture.

Last edited by green; 02-17-2009 at 09:29 PM.
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Unread 02-18-2009, 11:50 AM   #17
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MarkosJal,
please check PM and try to register with the test server. May be we will see something unusual coming from your side.
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Unread 02-20-2009, 07:24 AM   #18
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The phone registers to the test server fine.

This is not a NAT issue as this is a wifi phone and I have tested from several hot spots. Also, Voxalot appears to be the only problematic server.

Green, you have a PM reply, I will leave the phone registering to the test account.
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Unread 02-20-2009, 01:49 PM   #19
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I've checked registration to the test server and it's looking OK.
It was a few 401 Authentication required retransmits but that's it...

Another observation - you're requesting Expires=60, if Voxalot will reply to this it will send you back Expires=600, but as soon as you are not receiving anything back from Voxalot this is not relevant.

Have no idea, sorry.
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Unread 02-20-2009, 05:49 PM   #20
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green,

I am curious about the rport issue. Did you see if the correct rport was returned to you?

MarkosJal,

Can you confirm that your DNS server is correctly resolving the voxalot proxy names? They should be:
us.voxalot.com: 64.34.173.199
eu.voxalot.com: 85.17.19.194
au.voxalot.com: 202.60.88.238

Have you tried registering to one of the other proxies?
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