Terry Slattery
Terry Slattery, is a senior network engineer with decades of experience in the internetworking industry. Prior to joining Chesapeake NetCraftsmen as...
Read Full Bio >>

Terry Slattery | December 13, 2011 |


Detecting Network Packet Loss

Detecting Network Packet Loss Key steps include investigating user complaints, examining endpoints, and monitoring device interfaces and traffic flows.

Key steps include investigating user complaints, examining endpoints, and monitoring device interfaces and traffic flows.

I've been involved in network analysis with two customers recently who had problems with excessive packet loss. Of course, packet loss impacts all applications and voice/video is no exception. I thought that it would be useful to review some of the things that I found in the cases that I investigated.

Investigate Customer Complaints
I start by looking for evidence of packet loss. In the example that I described last month (see Know the Path Your Media Sessions Take, a video conferencing system showed evidence of packet loss. I could have also checked the video conferencing system operational statistics to see if it was experiencing packet loss, because the systems keep track of delay, jitter, and packet loss statistics for each call. The reports we received from customers and the technical staff indicated a consistent problem with packet loss.

We used traceroute to determine the path between the systems. The links in the path didn't show any evidence of packet loss. Fortunately, someone else checked the configuration of the video conferencing systems and found that they were using a media gateway that was on the Internet instead of the one within the enterprise. The relatively large bandwidth that was required for the video link was not able to transit the path via the Internet without a significant amount of loss. This scenario was a rather strange cause of packet loss, but highlights the point that when you've eliminated common sources of a problem, you have to start looking at less common sources.

Examine the Endpoints
Another similar source of packet loss information is from the communicating endpoints. Voice and video endpoints keep information about delay, jitter, and packet loss for at least the prior call. Some systems report the statistics at the end of each call to the call controller, where the statistics are recorded. I like to examine end device packet loss figures. In addition to the packet loss figures, I want to know the IP address of the other endpoint that was participating in the call. By looking a a lot of calls between different systems, I can determine if there is packet loss on subsets of calls. Then, looking at the geography of the endpoints, I can narrow the search for the origin of the packet loss.

I use the endpoint statistics to determine which endpoints have the highest packet loss. I then examine the set of destinations that were involved in calls with the highest packet loss. If a wide set of destinations are showing packet loss, the source of the problem is close to the endpoint that I'm examining. I will collect traceroute data for the calls and look for common network elements. Is a certain link, router, or switch always in the path when high errors are observed? I can then begin examining the network for the source of the problem.

Monitor Network Device Interfaces
Another approach is to look at interface statistics collected by the network management system (NMS). As I discovered recently (see Rethinking Interface Error Reports, simply looking at interfaces with high percentages of errors is not sufficient for finding all the sources of errors that need to be examined.

I am now also looking at the total number of errors on an interface. The total error count finds interfaces that have high volume and high errors, but because of the high volume, have a low percentage of errors. The high data volume tells me that it is an important interface and that the errors are impacting all applications using that path, not just voice and video. At one site, some interfaces were recording more than 1 million packet errors per day. Since there are 86,400 seconds in a day, that's 11 errors per second, if averaged over a day. In reality, more data is probably being sent during the day, so the peak error rate is likely much higher. Finding these problems and fixing them is key to improving overall network performance, and ultimately, the productivity of the organization.

What if you can't get good data from your network management systems? We were recently working with a customer who didn't have an NMS configured to monitor many network device interfaces. So we collected the output from running a series of "show interfaces" commands. We were then able to use some simple scripts to find interfaces that had high error counts. Several data center switch interfaces appeared in our list, so we immediately focused on them and identified problems that affected several key servers. While these servers were not voice or video servers, they impacted several very important business applications. We also identified a core link that had a bad cable, which was affecting voice, video, and data connectivity to a large number of WAN sites.

Monitor Traffic Flows
One of the best ways to identify network packet loss is to install packet capture and analysis systems at key locations within the network. Several products, such as those from NetScout, Opnet, and Wireshark can collect voice and video data, analyze the resulting packet streams, and report whether packet loss is occurring. Many of these systems can also report on high jitter or high delay (delay is harder to identify, due to the need to measure transit time across the network). If packet loss is found, the monitoring system may need to be moved to identify the specific source of the packet loss.

Detecting packet loss is the first step. Remediation is the next step. I'll describe several causes of packet loss and how to fix them in the next post.


Enterprise Connect Orlando 2018
March 12-15 | Orlando, FL

Connect with the Entire Enterprise Communications & Collaboration Ecosystem

Stay Up-to-Date: Hear industry visionaries in Keynotes and General Sessions delivering the latest insight on UC, mobility, collaboration and cloud

Grow Your Network: Connect with the largest gathering of enterprise IT and business leaders and influencers

Learn From Industry Leaders: Attend a full range of Conference Sessions, Free Programs and Special Events

Evaluate All Your Options: Engage with 190+ of the leading equipment, software and service providers

Have Fun! Mingle with sponsors, exhibitors, attendees, guest speakers and industry players during evening receptions

Register now with code NOJITTEREB to save $200 Off Advance Rates or get a FREE Expo Pass!

March 7, 2018

Video collaboration is experiencing significant change and innovation-how can your enterprise take advantage? In this webinar, leading industry analyst Ira Weinstein will present detailed analysis

February 21, 2018

Business agility has become the strongest driver for enterprises to begin migrating their communications to the cloud-and its a benefit that enterprises are already realizing. To gain this benefit

February 7, 2018

Enterprises are starting to grasp the critical importance of security and compliance in their team collaboration deployments. And once the risks are mitigated, your enterprise can integrate these n

March 12, 2018
An effective E-911 implementation doesn't just happen; it takes a solid strategy. Tune in for tips from IT expert Irwin Lazar, of Nemertes Research.
March 9, 2018
IT consultant Steve Leaden lays out the whys and how-tos of getting the green light for your convergence strategy.
March 7, 2018
In advance of his speech tech tutorial at EC18, communications analyst Jon Arnold explores what voice means in a post-PBX world.
February 28, 2018
Voice engagement isn't about a simple phone call any longer, but rather a conversational experience that crosses from one channel to the next, as Daniel Hong, a VP and research director with Forrester....
February 16, 2018
What trends and technologies should you be up on for your contact center? Sheila McGee-Smith, Contact Center & Customer Experience track chair for Enterprise Connect 2018, gives us the lowdown.
February 9, 2018
Melanie Turek, VP of connected work research at Frost & Sullivan, walks us through key components -- and sticking points -- of customer-oriented digital transformation projects.
February 2, 2018
UC consultant Marty Parker has crunched lots of numbers evaluating UC options; tune in for what he's learned and tips for your own analysis.
January 26, 2018
Don't miss out on the fun! Organizer Alan Quayle shares details of his pre-Enterprise Connect hackathon, TADHack-mini '18, showcasing programmable communications.
December 20, 2017
Kevin Kieller, partner with enableUC, provides advice on how to move forward with your Skype for Business and Teams deployments.
December 20, 2017
Zeus Kerravala, principal analyst with ZK Research, shares his perspective on artificial intelligence and the future of team collaboration.
December 20, 2017
Delanda Coleman, Microsoft senior marketing manager, explains the Teams vision and shares use case examples.
November 30, 2017
With a ruling on the FCC's proposed order to dismantle the Open Internet Order expected this month, communications technology attorney Martha Buyer walks us through what's at stake.
October 23, 2017
Wondering which Office 365 collaboration tool to use when? Get quick pointers from CBT Nuggets instructor Simona Millham.
September 22, 2017
In this podcast, we explore the future of work with Robert Brown, AVP of the Cognizant Center for the Future of Work, who helps us answer the question, "What do we do when machines do everything?"
September 8, 2017
Greg Collins, a technology analyst and strategist with Exact Ventures, delivers a status report on 5G implementation plans and tells enterprises why they shouldn't wait to move ahead on potential use ....
August 25, 2017
Find out what business considerations are driving the SIP trunking market today, and learn a bit about how satisfied enterprises are with their providers. We talk with John Malone, president of The Ea....
August 16, 2017
World Vision U.S. is finding lots of goodness in RingCentral's cloud communications service, but as Randy Boyd, infrastructure architect at the global humanitarian nonprofit, tells us, he and his team....
August 11, 2017
Alicia Gee, director of unified communications at Sutter Physician Services, oversees the technical team supporting a 1,000-agent contact center running on Genesys PureConnect. She catches us up on th....
August 4, 2017
Andrew Prokop, communications evangelist with Arrow Systems Integration, has lately been working on integrating enterprise communications into Internet of Things ecosystems. He shares examples and off....
July 27, 2017
Industry watcher Elka Popova, a Frost & Sullivan program director, shares her perspective on this acquisition, discussing Mitel's market positioning, why the move makes sense, and more.
July 14, 2017
Lantre Barr, founder and CEO of Blacc Spot Media, urges any enterprise that's been on the fence about integrating real-time communications into business workflows to jump off and get started. Tune and....
June 28, 2017
Communications expert Tsahi Levent-Levi, author of the popular blog, keeps a running tally and comprehensive overview of communications platform-as-a-service offerings in his "Choosing a W....
June 9, 2017
If you think telecom expense management applies to nothing more than business phone lines, think again. Hyoun Park, founder and principal investigator with technology advisory Amalgam Insights, tells ....
June 2, 2017
Enterprises strategizing on mobility today, including for internal collaboration, don't have the luxury of learning as they go. Tony Rizzo, enterprise mobility specialist with Blue Hill Research, expl....
May 24, 2017
Mark Winther, head of IDC's global telecom consulting practice, gives us his take on how CPaaS providers evolve beyond the basic building blocks and address maturing enterprise needs.
May 18, 2017
Diane Myers, senior research director at IHS Markit, walks us through her 2017 UC-as-a-service report... and shares what might be to come in 2018.
April 28, 2017
Change isn't easy, but it is necessary. Tune in for advice and perspective from Zeus Kerravala, co-author of a "Digital Transformation for Dummies" special edition.
April 20, 2017
Robin Gareiss, president of Nemertes Research, shares insight gleaned from the firm's 12th annual UCC Total Cost of Operations study.
March 23, 2017
Tim Banting, of Current Analysis, gives us a peek into what the next three years will bring in advance of his Enterprise Connect session exploring the question: Will there be a new model for enterpris....
March 15, 2017
Andrew Prokop, communications evangelist with Arrow Systems Integration, discusses the evolving role of the all-important session border controller.
March 9, 2017
Organizer Alan Quayle gives us the lowdown on programmable communications and all you need to know about participating in this pre-Enterprise Connect hackathon.
March 3, 2017
From protecting against new vulnerabilities to keeping security assessments up to date, security consultant Mark Collier shares tips on how best to protect your UC systems.
February 24, 2017
UC analyst Blair Pleasant sorts through the myriad cloud architectural models underlying UCaaS and CCaaS offerings, and explains why knowing the differences matter.
February 17, 2017
From the most basics of basics to the hidden gotchas, UC consultant Melissa Swartz helps demystify the complex world of SIP trunking.
February 7, 2017
UC&C consultant Kevin Kieller, a partner at enableUC, shares pointers for making the right architectural choices for your Skype for Business deployment.
February 1, 2017
Elka Popova, a Frost & Sullivan program director, shares a status report on the UCaaS market today and offers her perspective on what large enterprises need before committing to UC in the cloud.
January 26, 2017
Andrew Davis, co-founder of Wainhouse Research and chair of the Video track at Enterprise Connect 2017, sorts through the myriad cloud video service options and shares how to tell if your choice is en....
January 23, 2017
Sheila McGee-Smith, Contact Center/Customer Experience track chair for Enterprise Connect 2017, tells us what we need to know about the role cloud software is playing in contact centers today.