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Short (mostly), quick and easy-to-read technical tips for network pros.

The Impact of Network Packet Loss and QoS on UC&C

Authored by Chris Greer

Unified Communications and Collaboration services have become a critical IT component for most business processes. UC&C combines messaging, voice, video, and data services into one platform, enabling employees and other personnel to quickly interact on projects regardless of their physical location or access method. UC&C can be hosted in a cloud or hybrid environment.

Like all services running over data networks, UC&C performance is susceptible to latency, delay, jitter and of course, packet loss.

When implementing and supporting UC&C, there are questions that may arise regarding how well packet loss is tolerated. What is an acceptable amount of network packet loss? At what point does it begin to impact the performance of sensitive network services such as Unified Communications and Collaboration?

How does packet loss impact UC&C Services?

UC&C services are typically delivered over a myriad of protocols and conversations, all working together to bring voice, video, data, messaging and more into one platform. As an example, Skype for Business utilizes more than 52 ports to deliver services to end users, some over UDP and others over TCP.

When packet loss is present on the network, the first UC&C components to be impacted are voice and video. Not only do these services generate the bulk of the bandwidth used by UC&C, they also are typically supported by connectionless streaming protocols which do not retransmit lost data. If a network connection is dropping these packets, the users will experience delays and service degradation.

Services that are delivered over TCP can also suffer due to packet loss, despite the retransmission capabilities of the protocol. Depending on the timing of the loss in the TCP stream, retransmissions can take up to three seconds to be sent, which will cause the service to lag or even disconnect when excessive.

How much packet loss is considered excessive? This has been a common question when implementing a UC&C solution, especially in a hybrid environment. According to one study, Skype for Business begins to suffer after 0.2% of traffic loss. This makes sense since these services are both sensitive and complex.

With such a low tolerance for packet loss, network engineers need to be vigilant about monitoring the network for links that have output drops, discards, and layer two errors, as well as ensuring they have implemented a solid QoS policy for UC&C. If just one switch or router in the path does not have the proper policy configuration, this can dramatically impact the quality of UC&C.

Make Sure to Monitor

Most, if not all organizations who implement UC&C will be utilizing a service provider network to connect them to cloud-based endpoints supporting the system. Network Engineers will not have visibility and control over these networks, so monitoring the performance of UC&C over the systems they have access to becomes even more critical. This will enable them to avoid the finger-pointing game with an ISP when the quality drops.

UC&C has become a critical component for doing business in many organizations. Make sure not to leave high quality to chance. Comb the network for signs and symptoms of packet loss before implementing UC&C, and monitor after deployment to ensure smooth sailing.

Want to get ahead of performance issues? Conduct a clean-up effort to stop the band-aids.

Download our Unified Communications Clean-up guide

Testing Power over Ethernet

As you prepare to either install new power sourcing equipment (PSE), which could be a PoE enabled switch or mid-span injector or you are working with an existing one, here’s a few things to keep in mind to ensure a smooth deployment.   

When provisioning the PSE for the various powered devices (PD) such as VoIP phones, security cameras, Wi-Fi access points and badge scanners to name a few, it is important to calculate the overall power requirement for all devices you are planning to connect to a given PSE to ensure it doesn’t get oversubscribed.  The chart below provides you with the level of power that is required at the PD depending on which IEEE standard you are working with.

While it’s ok to test the PoE voltage directly at the PSE, best practice is to test for the wattage or voltage level at the wall jack where the PD plugs in.  This is important because PoE will dissipate as it traverses the cable so you want to ensure the power at the wall jack is what is required per PD.

Keep in mind that PoE is subject to the same cable distance limitation as standard Cat 5, which is 100 meters or 328 feet.  If the physical cable is out of specification and longer than the TIA standard, power may be too weak by the time it reaches the PD.

Common PoE Issues to watch out for:

  • PoE is subject to the same distance limitations as standard network cable runs - 100m/328ft
  • Incompatibility between powered device (PD) and power sourcing equipment (PSE)
  • Switch over subscribed from a PoE perspective
  • Switch provisioning of PoE
  • Power limited per port
  • Cable faults

To get information on Troubleshooting PoE view our recorded webinar here.

UC Quality issues. Check Qos

The help desk may have received several reported problems involving the quality of recent voice calls or video sessions and troubleshooting the sources is often a challenge.  One area to consider is  the QoS classes assigned to applications and protocols throughout the enterprise environment. 

While many organizations have implemented QoS policies as part of their Voice and Video initiatives to help ensure high quality end-user experience, problems can still appear.

Consider the following possibilities:

  • Reports of poor VoIP experiences for employees at a regional office. 
    Source:  New routers at the branch offices were not configured with the proper QoS class assignments for Voice and Video – or for the data services for that matter
  • UC service quality throughout company may be experiencing intermittent problems.
    Source:  A new application service may have been introduced to the corporate environment and assigned the same QoS class as voice and video
  • Calls coming into a call center are being dropped as they are being transferred to home-based agents.
    Source: Traffic passing through a new SIP trunking service that mistakenly did not honor the QoS class assignment or mistakenly changes the QoS class assignments as it passes across their network

These are but a few examples that demostrate the importance QoS plays helping maintain a quality user experience with unified communications.  So the next time a UC performance problem is reported,  perhaps it has something to do with QoS class assignments.


11ac Deployments. Rip-n-Replace?

If you’ve chosen to move forward with an 11ac deployment, you will be faced with one of two deployment options: greenfield or upgrade. Either you are installing a Wi-Fi infrastructure for the first time or you are upgrading an existing deployment. Given the pervasive nature of Wi-Fi technology, it’s far more likely that you are considering an upgrade. You may also be facing a fiscal decision on whether your existing equipment has reached the end of its useful and/or cost-effective life.

When budgetary constraints allow it, “rip-n-replace” deployments can be exciting… so exciting in fact that some network managers miss the significance of moving from a legacy Single Input Single Output (SISO) system (e.g. 11a, 11b, & 11g) to a Multiple Input Multiple Output (MIMO) system (e.g. 11n and 11ac). These two types of systems are very different, and deployment of 11n or 11ac as a replacement to 11a/b/g systems should always entail a new network design, survey, and validation.

There are, additionally, very few scenarios in networking where eliminating a device, or device type, can yield a 10-fold performance increase. Removing legacy 11a/b/g clients and APs from the network can produce just such an increase due to removing the need for some MAC layer protection mechanisms. If an end user wants to maximize ROI and to experience the benefits that 11ac can bring, they must aggressively remove legacy clients and APs.

So, which option is best for you?

Learn more, download 802.11ac Migration Guide


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