7 posts categorized "Viavi" Feed

Network Troubleshooting Through the OSI Model (by Melany Joy Beck)

Network Troubleshooting Through the OSI Model

When it comes to network troubleshooting, working through the Open Systems Interconnection (OSI) model is a straightforward process. With the exception of Layer 1, each layer of the OSI model relies on the next lower layer to provide services as specified. Requests drop down and are completed, as every layer interacts with the next layer, both above and below. When dealing with different layers, understanding how each delivers data and functions impacts how you will troubleshoot.


Viavi guide to enterprise protocols poster – Get yours today. 

Viavi free osi

Layer Highlights and Functions - A complete view from Layer 1 through Layer 7!

Read on to see each layer overview and more free links below - 


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The Payoff of having a double sided capture! (by Mike Motta)

The complaint came in that it was taking from 4 to 20 minutes to transfer data.

Why is the network slow?  Is it the network?

Could it be the infamous SNAIL problem?


At first the client sent me a trace only from the client side.  The trace file showed packets out of order and some re-transmissions along with low TCP windows.  I asked the client if it was possible to get a capture from both sides, client and server and the answer was “yes” (In my world that is the best way to eliminate any magic!)  

First: I looked at the server side trace file first.  It showed the server re-transmitting over a thousand times.  (Uh Oh)   

By having both sides I was able to prove that the server did indeed send the packet but the client did not receive it. 

We can also see that they are 5 hops from each other, which means something is dropping packets. 

Next : It is time to interrogate router interfaces and firewall interfaces for discards or drops. 

Watch this Video for the problem visibility process, guiding us to the issue at https://youtu.be/WW0SjeeteK8 

Get a TAP to see every bit of your Data!

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LMTV LIVE | Networking Trends for 2017 (with Mike Canney of Viavi)

Live Broadcast starts @ 9:30 AM PST, Wednesday, January 11, 2017

ViaviMike canneyWith the New Year’s celebrations behind us, it’s time to put down the eggnog and look forward to the key technologies and trends that will impact network professionals in 2017.

LMTV will kick off this year with Mike Canney, Principal Strategic Architect and troubleshooter of Viavi Solutions, to take a look into our crystal ball to discuss the biggest things to impact IT.

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Why Packetheads Need Not Fear Cisco ACI (by Mike Canney)

Why Packetheads Need Not Fear Cisco ACI

There seems to be much mystique and confusion over Cisco’s ACI and how we as network analysts will troubleshoot in this new network environment. It’s an architecture to which few seem to have completed the move, but many are planning to do so in the near future. Now is the time to architect with visibility in mind.


With Cisco ACI there has been some misunderstanding based on early claims of ‘not needing packets anymore’ to discussions on ’how the heck are we going to do this?’ Eager to confirm my beliefs about ACI, I attended many sessions at the Cisco Live conference this year. There was a lot of clarification and confirmation of how to best instrument new networks for full visibility. 

The Short Answer:  Not much has changed as far as building a visibility fabric. If you have familiarity with building such a fabric in the VMware Nexus ‘Top of the Rack’ design, you will have no issue capturing in an ACI environment. Wherein the Nexus model, to get east-west traffic, you would simply tap the uplinks between the top of the rack and the aggregation layer, in an ACI environment you tap between the spine and leaf switches to obtain traffic. 


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LMTV LIVE | Steve Brown and Warren Caron of Viavi Solutions


This week we will speak with Steve Brown and Warren Caron of Viavi Solutions, who are their Director of Solutions Marketing and Solutions Engineer, respectively.

With network teams increasingly involved in all aspects of security from threat prevention to breach investigation and remediation, understanding how to be proactive is critical. In this week's LMTV LIVE, we’ll discuss how network pros can more effectively work with security teams on threat prevention, investigations, and cleanup efforts.

  • Proactively ID anomalous network behavior
  • Recognize malware, ransomware, and DDoS
  • Assess damage post-attack
  • Reconstruct or playback breaches
  • Ensure successful remediation
  • Overcoming key visibility and intelligence issues
  • Strategies to ensure security events are fully captured

3 Network Nightmares (by Melany Joy Beck)

True Tales of IT Terror

It’s that time of year again.

Region Capture

These bloodcurdling tales of IT terror will give you chills and send you scrambling for your monitoring tools.

  1. The Case of the Disappearing Network

Let’s face it, nothing’s worse than logging on to find that your entire network has made like Houdini and disappeared from the face of the earth. But that’s exactly what happened to Peter Lee at Northern Devon Healthcare in the UK when a legacy switch went bump in the night.

“One day, we came in and lost the whole network. It was completely gone.” 

“About 6 years ago, there were a number of legacy Cisco 3500XL series switches in existence on the campus,” says Lee, Network Technology Specialist at Northern Devon Healthcare. “I suspected as soon as I started working here that they could be a potential source of problems. One day, we came in and lost the whole network. It was completely gone.”

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