How to Configure Quality of Service (QoS) On Your VoIP Applications

Voice over Internet Protocol (VoIP) is rapidly replacing landlines for delivering phone calls to homes and businesses. Common residential home VoIP providers include Vonage, Skype and now Google Voice. Businesses are replacing their now antiquated digital systems with providers delivering services called Hosted PBX, Hosted VoIP, IP PBX, Virtual PBX and many more. If you have plans to implement or have already implemented VoIP, you should review your network for Quality of Service (QoS) prioritization.

VoIP voice quality problems can have many causes. Missing or inadequate voice prioritization or QoS is a primary source of VoIP problems. This article provides some background on where QoS needs to be enforced in the network and gives an explanation on what needs to be done.

QoS provides priority to VoIP packets at network choke points. The most common network choke point, for most homes and businesses, is where the data traffic transitions from the Local Area Network (LAN) to the Internet. The LAN can be running at speeds of 10Mb to 100Mb (million bits per second) or more. DSL and cable Internet services may have speeds out to the Internet as low as 256Kb (thousand bits per second). In essence, the data is transitioning from a 10 lane superhighway to a 1 lane road. As VoIP is very sensitive to delays, it must not wait for its turn to enter the 1 lane road, your Internet connection.

QoS is put into effect by a router that examines each packet and ships specific ones to the head of the line. QoS can be accomplished through Virtual Local Area Networks (VLANs) or Differentiated Service Code Point (DSCP) inside the Type of Service field for IPv4 or Traffic Class Octet in IPv6. For those familiar with the 7 layers of the network, VLAN operates in layer 2 and DSCP is layer 3.

VLAN

A VLAN is a virtual subnet that creates smaller broadcast domains within the LAN to ensure efficient use of bandwidth. For example, your VoIP telephones can be grouped together in one VLAN and your computers into another. Separate voice and data VLANs can protect VoIP traffic from service disruptions caused by virus or worm activity because Ethernet switches may not bridge IP traffic between VLANs.

The data VLAN carrying general traffic to the Internet is given the lowest priority. The voice VLAN is given the highest priority.

DSCP

DSCP relies on packets being classified and marked as belonging to a specific class. DSCP aware routers implement Per Hop Behaviors (PHBs), which implement packet forwarding mechanisms with each class of traffic. DSCP is the primary protocol routers use to provide different levels of service.

Although a network can implement up to 64 different classes of traffic, certain encodings in the DSCP field are recommended. Most networks use the commonly defined PHBs of default, Expedited Forwarding (EF), Assured Forwarding (AF) and Class Selector. The EF PHB is for applications that require low delay, low jitter and low packet loss which makes it suitable for VoIP, video and other realtime services.

The primary disadvantage of DSCP is any application can mark the EF bit and compete with your network's mission critical traffic. For example, your company may use a Virtual PBX instead of a traditional telephone system. Your calls to the Public Switched Telephone Network must transverse the Internet with low delay, jitter and packet loss. A router between the LAN and Internet gives packets marked with EF priority out to the Internet. Employees within your company may use personal Skype, Google Voice or other video services which may mark the EF bit as well and compete with your mission critical VoIP traffic. This problem is solved by certain routers that can inspect each packet and only keep the EF bit set for packets destined to specific IP addresses.

Although more difficult to implement, VLANs can provide superior voice prioritization if your computers and VoIP telephones are different devices. VLANs will prioritize all traffic within the subnet including call signaling. DSCP is easier to implement but is less accurate. However, smaller networks such as small businesses and homes, installing a router with DSCP traffic management is enough.

Inadequate voice prioritization is only one source of VoIP problems. Please read "Top 7 Common Causes of VoIP voice Quality Problems" to learn about other sources of trouble. Visit my website to learn how Hosted PBX from Hosted VoIP providers can help your business. You can contact my knowledgeable sales engineers at 866-242-6161.

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7 Reasons to Add SIP Trunking to Your Telephone System

Voice over Internet Protocol (VoIP) usually brings to mind popular consumer services such as Vonage, Skype and Google Voice. Many businesses have replaced their old telephone systems with VoIP through services commonly called Hosted VoIP, Hosted PBX, IP Centrex & Virtual PBX from business VoIP providers. However, integrating VoIP with legacy telephone systems is gaining popularity through Session Initiation Protocol or SIP trunking.

SIP trunking is not limited to newer telephone systems that can accept them directly. Older telephone systems can use a SIP trunk with the aid of an integration box. Here is a list of SIP trunk benefits that most any telephone system can take advantage:

1. Direct Inward Dial (DID) DID is a telephone number that rings directly to a desk phone or a department. The number can be published on business cards, the Internet and directories or it can be private. Older telephone systems require expensive circuits or telephone lines for DID. Newer digital systems can handle DID with the use of a Primary Rate Interface (PRI) circuit. Although PRIs are an efficient way to take advantage of DIDs, they can be costly for telephone systems of 20 phones or less. SIP trunks can provide DIDs economically for very small phone systems.

2. Publish Local Numbers in other Market Areas The 10 digit telephone numbers that point to SIP trunks are not limited by geographical areas. A telephone system located in Dallas could have local numbers on its from Dallas, Seattle, Los Angeles, New York and Chicago. Someone calling the local Chicago telephone number would have no idea that they are talking to someone in Dallas.

3. Stop Guessing at the Required Number of Telephone Lines Most businesses with older phone systems almost always guess at the number of telephone lines that they need. The penalty for guessing wrong is paying too much for too many lines or losing business and frustrating callers with too few. Although many SIP services are priced base upon the number of concurrent calls that they will pass, the price point for each path is significantly less than traditional service. In addition, many SIP providers can advise on whether a business has the correct number of concurrent call paths.

4. Back-Up Circuits Companies that experience periods of heavy call volume or cannot afford to be without telephone service can employ SIP trunks as back-up. SIP Trunks affordable price makes them a better alternative than other options. If the Internet provider is a cable company or wireless ISP, SIP trunks can also offer a diverse cable route into the building since they are delivered over the Internet.

5. Disaster Recovery SIP trunk providers deliver their service from 'soft' switches that are far more flexible than the large hardware central office switches of large telephone companies. Beyond providing a diverse cable route into the business, many SIP trunk providers can automatically re-route calls to other 10 digit telephone numbers including mobile phones in the event they lose contact with their customer. Further, they can process calls through automated attendants and voicemail at their Point of Presence (POP).

6. Unlimited Long Distance SIP trunk services are delivered with a wide variety of price packages. Businesses can easily find a package that will meet their needs. Some packages include unlimited domestic long distance within the Continental United States. SIP trunks can be used for outbound long distance calls only, turning exorbitant long distance bills into a flat monthly rate.

7. Quickly Re-configure Service to Meet Changing Needs The 'soft' switch architecture of SIP trunk providers allows them to be agile in meeting a changing customer's needs. They can quickly add and subtract features and concurrent calls paths within hours and without sending a service technician on-site.

SIP trunks can add value and enhance the features of any telephone system including old legacy systems. They adapt quickly, control costs and offer features not available from standard telephone line service. With the aid of integration boxes, any business can start taking advantage of VoIP and its many benefits without changing out their complete telephone system.

Visit my website to learn how Hosted VoIP and Hosted PBX can help your business. You can contact my knowledgeable Hosted PBX sales engineers at 866-242-6161.

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