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The Edge Tech Tips

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.

Compare MSS with Window size

The two parameters are completely different. Maximum segment size (MSS) refers to the maximum number of octets that may appear in each transmission. The window size indicates how much temporary buffer the receiving host has set aside for received data that has not yet processed.

The MSS option announces the maximum received segment size that the sender of that option is expecting. It is made during the initial connection setup only.  For most Ethernet implementations the MSS is 1460 bytes, which is the maximum Ethernet frame size of 1518 minus all the OSI Layers 2, 3, 4 header information.  One of the first troubleshooting steps to take when having difficulties establishing and maintaining a TCP connection when no errors are present might be to reduce the MSS.*

*Source: Network Maintenance and Troubleshooting Guide, Second Edition, by Neal Allen.

    Get Ready to Manage New Technologies

    7 questions from Engr. Change WP

    No company will successfully implement any new technology if they can’t effectively manage it.

    Is your network operations team fully prepared to address the issues that arise with both internal and external technologies?

    Here are 7 questions to ask:

    1. Does your IT organization have a well-understood, integrated plan for the evolution of its applications, compute, storage, networking and security?
    2. Does your organization have a well-understood plan for how network management will evolve to respond to the ongoing business and technology changes?
    3. Does your organization have a well-understood plan for the evolution of the skills of its network engineers?
    4. Does your organization regularly assess the tools used for network management and budget for upgrades or more contemporary solutions?
    5. How much of a consideration is the ability to troubleshoot problems when your organization makes decisions to adopt new services such as public cloud services or implement SDN?
    6. How often does your organization identify and eliminate problems before they impact the user?
    7. To what degree does your organization have a CYA approach to network management whereby each technology domain tries to prove that they are not the source of the problem?