Tag Archives: VoFi

Organizations should consider VoFi, but they need to be aware of the issues first

WildPackets recently hosted a webinar on the proliferation of wireless handheld devices, especially tablets and smart phones, during which we discussed how they put increased strain on today’s wireless networks. As technology continues to rapidly evolve, network engineers are in a race to keep up – both with system interoperability concerns and throughput, reliability, and security issues. New problems accompany new technologies, and voice over Wi-Fi, sometimes called VoFi, is no different.

So why do we need VoFi? Even in today’s technological environment with cell towers going up all around the country, phone call quality can still be quite spotty. Especially in office buildings, behind glass, aluminum and concrete, voice quality is reduced significantly.

VoFi enables organizations to utilize the 802.11 network rather than rely on a regular cellular network, improving quality of voice due to stronger signals and a well-controlled infrastructure. VoFi is available on most devices, and all new devices that support 802.11ac, making it much simpler to deploy, and offering organizations the convenience of not having to purchase new equipment. Lastly, because VoFi essentially relies on BYOD, organizations are no longer responsible for supplying the device, which decreases the total cost involved.

However, while organizations may consider VoFi for the quality, convenience and cost benefits, VoFi has very unique networking requirements as compared to typical data traffic on the network. Voice traffic is highly susceptible to packet loss, jitter and latency – resulting in dropped calls, interruptions and other issues. Below, we take a deeper dive into each of these issues and what organizations should look for to ensure they don’t occur.

  • Latency: Most people think of latency as network propagation delay. But it often gets introduced in many other ways. With VoFi, latency occurs because packets must move from one handset to another, making their way through a number of switches and routers along the way. As a result, VoFi calls can experience halting conversations, echoing and overlapping sounds (noises, words). While latency is inherent in any network, the lower the latency, of course, the better the voice quality. Industry guidelines put the highest acceptable latency at 150 milliseconds (ms). Any higher and quality begins to degrade.
  • Jitter: Jitter deals with the variance in the packet delivery interval and takes place when packet delivery suffers from variable delay. VoFi expects that packets are delivered at a very regular interval, but as soon as some variation in delivery occurs, the quality of conversations suffers. To help compensate for this, jitter buffering is often employed to smooth the variability and allow for reordering voice packets, which may arrive out of order, but adds some latency. In addition, severe jitter can lead to packet loss, as packets that are delayed too long are not allowed to enter the jitter buffer.
  • Packet loss: Packet loss exists on every network and is caused by physical layer corruption, congestion without QoS provisions, and as we mentioned above, jitter buffer discards due to excessive latency. As a rule, packet loss in VoIP (and VoFi) should never exceed 1 percent, which essentially means one voice skip every three minutes. DSP algorithms may compensate for up to 30 ms of missing data; any more than this, and missing audio will be noticeable to listeners.

For much more information on VoFi, including the tools needed for securing your network and optimizing performance, and how you can identify and monitor the maximum threshold for voice and video over Wi-Fi capacity, please refer to our VoFi web seminar.

Check out a quick preview of the OnDemand webcast talking about the impact of “Just One More Call” on a VOIP and/or VoFi network. The full OnDemand webcast can be accessed here.

Are Your Users Complaining? Pinpoint the Reason with OmniPeek

Try as you might, making users happy with network performance is a difficult task. Sometimes problems arise with applications and sometimes with the network itself. Either way, it is your job to make the end user experience the best that it can be.

Luckily, if you are using OmniPeek, problems of any type, whether application or network, or common or rare, can be easily remedied. Let’s take a look at some common user experience issues and how OmniPeek can help to identify the root cause and guide you towards a permanent solution.

Network Downtime
Fortunately unplanned network downtime is a pretty rare occurrence nowadays, but if it does occur the response must be instantaneous. With OmniPeek you can immediately assess the scope of the outage, from a few specific users to an entire subnet. If distributed, 24×7 analysis is in place, you can rewind the network to see exactly what was going on when the outage occurred, providing the best clues possible for determining the root cause, which in this case is probably equipment failure somewhere in the network path of the effected users.

Not Enough Bandwidth? Find the Hog
Bandwidth issues typically arise not because of a lack of bandwidth, but because a user or users are consuming an abnormally high amount of bandwidth. This is becoming more common with the wide availability of video streaming sources, particularly those that are not work related. The Compass dashboard in OmniPeek is an easy way to isolate bandwidth hogs, allowing you to identify not only the user but the type of traffic, providing the ammunition you need to ensure that network traffic is strictly business related.

VoIP Quality Issues
VoIP is the most commonly used real-time protocol on corporate networks. Given its real-time nature, it is extremely sensitive to network problems like too much latency, dropped packets, and jitter, much more so than “regular” network traffic. For real-time data to be useful, it must arrive in order, and within a few hundred milliseconds of being sent, otherwise it is no longer “real-time” and doesn’t fit into the overall conversational flow. Problems with real-time data will continue to grow as more corporate video is transmitted over IP networks, and as more wireless networks are used for the last 100m of data delivery (voice over Wi-Fi, or VoFi).

From a network perspective, VoIP, VoFi, or video over IP are just data on the network. In order to identify problems with real-time traffic, you first need to isolate the traffic, while still seeing it in the context of the overall network. To do this, you can use the Voice and Video dashboard in OmniPeek to see how real-time traffic is coexisting with the rest of the network. Then, the Calls and Media views will allow you to see a more detailed analysis of the packet-by-packet performance of the real-time flow, including detailed analytical metrics and a bounce diagram so you can pinpoint exactly where the problem is, and compare it with network activity to correlate real-time transport problems with overall network usage.

If you are experiencing another kind of reoccurring issue on your network, please leave us a comment and we’ll address best practices for remedying this issue.

Best Practices for Analyzing Voice over Wi-Fi (VoFi) with WildPackets

With 802.11n in full swing and 802.11ac rolling out next year, Voice over Wireless, or VoFi, is becoming more and more common in the workplace. Not only does this technology reduce cellular usage, but it also eliminates the issue of dropped calls at the office. Luckily for all of you, VoFi is also not a difficult technology to monitor and analyze with WildPackets.

Scan Your Environment
From a WildPackets perspective, VoFi data, like traditional VoIP, is just another data type on the network, so the first step in analyzing VoFi is no different than the first step in analyzing your overall Wi-Fi network – perform a scan of the 802.11 bands in use, 2.4GHz, 5GHz, or both. All that’s needed is a single, supported WLAN adapter for capturing traffic with OmniPeek, and you’re on your way. OmniPeek will scan through all of the channels you choose, dwelling on each channel for 500msec, or whatever dwell time you configure. A scan provides a great deal of information about not only your network, but the overall WLAN environment as well. The scan will identify all of your networks and APs (based on the location where the capture is performed), as well as all neighboring WLAN activity. Based on this information you may decide to do some channel reallocation to avoid conflicts with neighboring APs that are not under your control, or you may even decide to physically move some assets. The scan will also allow you to see the utilization of each of your APs, indicating potentially oversubscribed APs. Pay close attention to the wireless Expert events generated by OmniPeek, especially events like “Wireless RF Interference” and “Wireless Transmission Retries” which give you an overall indication of environmental issues that are affecting your WLAN performance, and which are likely to adversely affect VoFi performance.

Zoom In On Your Network
Now that you know exactly how your network fits in with your surroundings, it’s time to zoom in on your specific network. The best way to do this is to configure a supported WLAN adapter to capture traffic with OmniPeek on each channel in use by your WLAN, or at least each of the channels in use that can be seen from your current measurement point. This will give you complete, 100% coverage for all channels in use, making sure that you don’t miss any critical packets, and allowing for advanced inter-channel analysis like roaming. Identifying roaming events and measuring the overall roaming timing is critical for time-sensitive data like VoFi, as roaming latencies in excess of 150msec (not uncommon) will adversely affect VoFi call quality for any mobile VoFi user on your network.

Zoom In On Your VoFi Calls
As stated earlier, VoFi is just another data type on your network as far as OmniPeek is concerned, so if you’re capturing WLAN traffic you’re capturing VoFi traffic. There are several ways in OmniPeek to instantly isolate your VoFi traffic so you can get an immediate assessment. First, there’s the Voice and Video dashboard, which provides summary information regarding call quality, call volume (number of calls over time), and network utilization for VoFi versus all other data. A quick scan of the dashboard will let you know if you need more detailed analysis.  When you do, proceed to the Calls and Media views, which provide a detailed breakdown of each VoFi call. The Calls view provides detailed analysis regarding the signaling for each call, including a detailed, packet-by-packet bounce diagram so you can “see” the call setup in detail. The Media view breaks down each call into individual flows, since the packet path between the caller and the callee can differ from that between the callee and the caller. This view includes details of the quality of the actual voice transmission, including analysis of latency, packet loss, jitter, and MOS and R-Factor voice quality metrics. And if you’re really not sure how all of these metrics stack up regarding “real world” quality, you can play back either the entire call or just each leg of the call to hear what it really sounded like.

Remember that VoFi is just another data type or application on your network, so analysis is similar to any other running app. Start by testing out your overall environment, the end user experience, and gradually dive deeper into your network to find the problem.