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Knowledgebase: Digital Phone Services
VOIP QoS Strategy - A How to guide
Posted by Nicky Smith on 13 January 2010 10:51 PM
Quality of Service (QoS) is the secret sauce of many custom VOIP solutions. The big bottleneck for VOIP QoS and the place that causes most of the quality problems is the very first outbound link. This is frequently the slowest link, being a DSL or cable modem link of a little as 128k upstream. If you can get out that first link with delay and jitter under control, getting quality VOIP performance through the big pipes in the network will be no problem.

As you plan your VOIP installation, keep in mind that the most important factor for the quality of service of the VOIP calls is the priority assigned on the first outbound link. Picking a product that can quickly and accurately identify and prioritize the important voice traffic is the critical issue for your quality of service.

You must also consider other factors to guarantee the best voice quality. Segregating VOIP and data into separate broadcast groups (Virtual LAN / VLAN) can be important in some networks. The use of Virtual Private Networks (VPN) to remote locations are critical to maintain services to remote IP phones; don't forget to think about how you will apply QoS to that remote IP phone over the VPN.

A very popular Router that supports QoS is the Linksys/Cisco RV016 or model RV082 available online for under $300.00 

Cisco Small Business Routers support:

  • VPN: Virtual private network technology lets your remote workers connect to your network through a secure Internet pathway. They can access their email and files as if they were in the office.
  • Security: Built-in firewalls, advanced encryption, and authentication features protect your network from external threats, keeping your business assets safe.
  • Connectivity: All Cisco Small Business Routers come with multiple connection options for maximum network expandability. Whether you're using them for an increased number of physical ports or wireless connectivity, these routers are built to deliver advanced connection sharing.
Learn more at Cisco's web site http://www.cisco.com/en/US/products/ps9926/index.html


Example QoS Settings for Cisco/Linksys RV016 and RV082 Router/Firewall.

In most cases your bandwdith provider is already providing you with more downloading ability that upload. So in this QoS configuration for best quality VoIP I have set three HIGH priority Upstream so TCP and UDP port 5060, TCP ports 10000-20000 as HIGH.





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