By Alok Saboo on March 22nd, 2010
There are several factors that influence the quality of our VoIP experience, including (but not limited to) our Internet speed, ISP VoIP shaping activities (e.g., blocking SIP ports), voice codecs, VoIP hardware (ATA) or software (SIP or soft phone), other networking equipments like routers, etc. While the Internet connection quality receives lot of attention, the other aspects do not get due attention. Today, I want to emphasize the importance of your router and provide you with some router settings so as to enhance your VoIP experience.
How your Router influences the VoIP quality?
In general, any device that you insert between your VoIP equipment (soft phone or ATA) and your ISP can potentially hurt your VoIP experience. Your router can affect your VoIP quality in the following way:
- A common practice nowadays is that ISP’s frequently throttle your Internet connections if they figure out that you are using a router. The assumption here is that you are feeding multiple devices through the router and hence consuming more bandwidth.
- Also, some incorrect settings on the router can hurt your VoIP quality.
Optimal router settings for VoIP
For the purpose of this tutorial, I am using a Linksys WRP400. Most of the Linksys devices have similar menus and settings, so you should be able to follow the tutorial with any other Linksys device. You can find similar settings in other routers as well (just look around for the options in various menus). So, here are some of the things that you may have to change:
- Clone your MAC address: ISPs use the MAC address of the device they are connected to determine if a router is being used or not (each router manufacturer has a range of MAC addresses allotted). MAC address is the physical address of your networking device (e.g., ethernet card). To fool your ISP in believing that you are not using a router, but connecting your computer directly, you need to clone your MAC address. If you change the MAC address of the router to the MAC address of your ethernet card, your ISP has no way to figure out if you are using a router and hence it should not indulge in traffic shaping activities.
Cloning your MAC address is an extremely simple process. Just go to Setup and you would see an option MAC Address Clone. Enable the option and click the Clone your PC’s MAC. This will automatically change the MAC address of your router to the MAC address of your PC. If you do not find the option to “Clone your PC’s MAC”, you can manually enter the MAC address in the field above. To find out your PC’s MAC address, go to command prompt and type “ipconfig/all” and look for the entry in the field “Physical Address” of your LAN card. Changing the MAC address should take care of most of your problems, but I would suggest that you also carry out the next step.
- Disable router firewall: While the router firewall may be an additional layer of protection, it may inadvertently also prevent some authentic traffic. If you are having trouble with your VoIP traffic, you may want to disable the firewall. This may sound more dangerous than it actually is. Disabling the router firewall effectively means that you are directly connected to the internet rather than using the router. You may want to install a personal firewall on your computer. To disable your router firewall, go to Security and change the settings as you see in the screenshot.
- Change RTP Packet size: Most routers ship with the default setting of 0.030 or 30ms, i.e., they transfer about 33 packets per second. This is not the most optimal setting in a lot of situations. I would recommend you change it to 0.02 (i.e., 50 packets per second) or even 0.010 (i.e., 100 packets per second). As you would have noticed, reducing the RTP packet size will increase the bandwidth consumed. But, it will significantly improve your call quality.
- Change Jitter Buffer settings: One last setting that you can play with is the jitter buffer setting. Without getting into the technical details, try changing the jitter settings from “High” to “Medium” or “Low”.
While these steps are not guaranteed to make VoIP work for you, they will ensure that the problem is not at your end. This tutorial, in addition to our earlier tutorial on trouble shooting your VoIP connection, should help you solve most of your VoIP issues.