Audio drops

Posts: 656 · Posted: Sat Feb 28, 2009 12:36 pm Post subject:

There is something you should configure in your DIR655 if you have not already. Under Advanced Settings, go to Firewall Settings. Disable the SPI Firewall at the top of the page and Disable Both SIP and RTSP at the bottom of the page. Save the settings and reboot the DIR-655.

The reason you are doing this is because SPI is Stateful Packet Inspection. This means all the packets are being inspected and sine we are dealing with a Real Time Protocol, during the inspection process, the router could be dropping many packets at a time resulting in the clips of lost audio.

The Application Layer Gateway attempts to help with certain applications but with SIP and RTP, this feature tends to cause more harm then good since Vonage already compensates for the problem of SIP / RTP through NAT.

This should be the first and quickest step to perform in order to seek resolution.

If this does not solve it for you, the next step is to reconfigure your network so that the Modem connects to the V-Portal's WAN port and then the V-Portal's LAN port connects to the DIR-655's WAN port. This way your router can be ruled out as the issue.

The occasional call quality issue could stem from you not configuring QOS in your router and any Internet traffic through your router would affect voice quality. Again this can be fixed with QOS settings in the DIR-655 or by doing the reconfiguration.

The echo could be as simple as the volume being too loud on the actual phone.

Posts: 21 · Vonage Forum Associate Joined: Jan 08, 2009 Posts: 21

VonTechMgr,
Thanks for the detailed response. I do have some questions.
First let me start by explaining that I have a "reserved" address assigned to my V-Portal and have setup QOS rules in the DIR655 to give priority to its traffic.

Now the questions...
1. Why would I disable SPI, stateful packet inspection? This is a desirable security feature which protects my home network.
2. I had already had SIP disabled which seemed to fix the issue I used to have with calls occasionally not having any audio at all. RTSP is enabled since it supposedly helps prioritize real time streaming. I stream Netflix, Hulu and CBS to my PS3/TV and I was under the impression this aided that. Is this not correct?

Thanks again for your help.
Regards,
RA

Posts: 293 · Vonage Forum Master Joined: Jan 22, 2006 Posts: 293

VonTechMgr wrote:

The reason you are doing this is because SPI is Stateful Packet Inspection. This means all the packets are being inspected and sine we are dealing with a Real Time Protocol, during the inspection process, the router could be dropping many packets at a time resulting in the clips of lost audio.

The Application Layer Gateway attempts to help with certain applications but with SIP and RTP, this feature tends to cause more harm then good since Vonage already compensates for the problem of SIP / RTP through NAT.

I think the key that VonTechMgr said is what I bolded. In this case you've got two things trying to do the same job and in essence getting in each others way. Since the Vonage device will be your best bet to know what it really needs then it really is the best bet to be up to the task.

Now you do have some firewall protection through NAT. If you still have concerns I'd suggest enabling the software firewalls as well. Otherwise, you'd need to change your network configuration around to essentially separate your Vonage system from your other network.

Posts: 21 · Vonage Forum Associate Joined: Jan 08, 2009 Posts: 21

outerfire wrote:

VonTechMgr wrote:

The reason you are doing this is because SPI is Stateful Packet Inspection. This means all the packets are being inspected and sine we are dealing with a Real Time Protocol, during the inspection process, the router could be dropping many packets at a time resulting in the clips of lost audio.

The Application Layer Gateway attempts to help with certain applications but with SIP and RTP, this feature tends to cause more harm then good since Vonage already compensates for the problem of SIP / RTP through NAT.

I think the key that VonTechMgr said is what I bolded. In this case you've got two things trying to do the same job and in essence getting in each others way. Since the Vonage device will be your best bet to know what it really needs then it really is the best bet to be up to the task.

Now you do have some firewall protection through NAT. If you still have concerns I'd suggest enabling the software firewalls as well. Otherwise, you'd need to change your network configuration around to essentially separate your Vonage system from your other network.

Okay guys. I will try it with these settings and see what happens.
Thanks for the suggestions.
Regards,
RA

Posts: 656 · Posted: Sat Feb 28, 2009 2:39 pm Post subject:

Quote:

1. Why would I disable SPI, stateful packet inspection? This is a desirable security feature which protects my home network.

While this provides a sense of security to the basic home user, it really does nothing more then inspect each packet which when performed on any streaming media type of packet, could result in dropped packets or delayed packets. In some routers, the SPI feature also ties into a DOS(denial of service) function and so many packets per second could generate this function to start rate limiting or completely drop periods of packets.

The NAT function of the router is what keeps you invisible to the internet and running a software firewall along with an anti-virus, anti-spyware, anti-malware application on your PC's will actually keep your PC safe.

Quote:

2. I had already had SIP disabled which seemed to fix the issue I used to have with calls occasionally not having any audio at all. RTSP is enabled since it supposedly helps prioritize real time streaming. I stream Netflix, Hulu and CBS to my PS3/TV and I was under the impression this aided that. Is this not correct?

QOS is what performs prioritization not the ALG. That is why the ALG fails under the Firewall Settings section of the router.

Definition of Application Layer Gateway:

In the context of computer networking, an application-level gateway [1] (also known as ALG or application layer gateway) consists of a security component that augments a firewall or NAT employed in a computer network. It allows customized NAT traversal filters to be plugged into the gateway to support address and port translation for certain application layer "control/data" protocols such as FTP, BitTorrent, SIP, RTSP, file transfer in IM applications etc. In order for these protocols to work through NAT or a firewall, either the application has to know about an address/port number combination that allows incoming packets, or the NAT has to monitor the control traffic and open up port mappings (firewall pinhole) dynamically as required. Legitimate application data can thus be passed through the security checks of the firewall or NAT that would have otherwise restricted the traffic for not meeting its limited filter criteria.

Vonage already compensates for SIP with 20 second registrations which will keep your NAT pinhole open and the use of the SIP Proxy with the help of Media Relay in the Vonage architecture is what will allow the RTP packets to traverse a network to reach the telephone adapter that is hidden behind a NAT router.

In most SIP and RTP type ALG implementations designed on today's routers, they are meant to assist with the function that Vonage already performs and in turn breaks the service from performing correctly.

Posts: 21 · Vonage Forum Associate Joined: Jan 08, 2009 Posts: 21

Okay, I tried all of the setting recommended... better for a short time and then bad again.

Then I moved the V-portal to be directly connected to my Cable modem with the DIR-655 behind the V-Portal. That worked for about 2 weeks and now my call quality is TERRIBLE AGAIN.... All the testing I do show about the same results... Seems the V-Portal is the issue....

Why is it so hard to get GOOD SERVICE????
RA