Using Wireshark SIP Analysis for VoIP scenarios

Troubleshooting VoIP issues can be troublesome. When something goes wrong, the lack of direct visibility as to what is occurring on the network with SIP and RTP packets can initially be intimidating to network and voice engineers. However, Wireshark SIP analysis turns ordinary engineers into superheroes, allowing them to see deep into the network and determine exactly what is happening.

In a series of previous articles, we took a look at several methods that can be used to capture voice packets on a network. We also introduced the Wireshark packet sniffing software, providing you with a solid foundation for understanding how captured packets are obtained and stored.

In this article, we’ll get our hands dirty by examining a real voice packet capture from a production network. We’ll go through the whole scenario, delving deeply into the details of the voice packets being exchanged. Let’s get started!

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Wireshark Packet Analysis – A Preparation for VoIP Analysis

When there’s trouble in the network, and voice services are suffering, those in need will call upon you, the networking superhero! As a superhero, you use your x-ray vision to zoom in to the microscopic world of voice packets, to perform a Wireshark packet analysis, and to investigate the malfunction and make things right. Then you will be hailed as the liberator and protector of the network!

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Using SPAN Port Mirroring for Wireshark VoIP Troubleshooting

Using SPAN Port Mirroring for Wireshark VoIP Troubleshooting

When I encounter a problem on a VoIP network that needs troubleshooting, I just wish that I had microscopic X-ray vision, like a superhero who is able to peer into the subatomic level of things.
It would be so advantageous to be able to instantaneously see what is going on with transmissions on the network.
When you experience voice quality issues, one way or choppy voice, or call setup problems, it would be great to be able to see, are the voice packets arriving? How are they arriving?
What kind of signaling is getting through and what is being blocked and where?
These are questions I wish I had instant access to, and this is what port mirroring is all about.

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How to Solve Cisco IP Phone Voice Quality Issues. The step by step guide.

How to solve Cisco IP Phone Voice Quality Issues

You get a call from a user stating that they have experienced poor voice quality issues with their Cisco IP phone.
Your mind goes numb, your palms get sweaty, and your eyes glaze over. What do you do? Where do you start? It’s so much easier to deal with problems where something stops working completely, rather than trying to resolve an intermittent fault such as bad voice quality.

Why are poor voice quality issues so difficult to tackle?
It’s usually because there is a myriad of different causes, and the methodology to investigate those causes is not always readily or intuitively clear. For voice troubleshooters, it is important to have a battle plan in place to quickly zero in on causes of voice degradation and to diagnose, identify, and resolve them as quickly as possible.

This article will focus on this battle plan so that you can identify the problem quickly, and determine the first troubleshooting steps, which are often the most difficult to decide upon.

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Cisco Voice Translation Rules. The Only Guide You’ll Ever Need.

Cisco Voice Translation Rules

Hey UC Pros! The need to interoperate across organizational and logical borders with different numbering requirements exists since the very beginning of the digital telephony.
Whether you interconnect with a SIP ITSP or your own legacy PBX, you will likely need to manipulate digits you exchange on both ends.
In Cisco IOS (and IOS-XE later) running either CUBE or Voice Gateway, Voice Translation Rules and Profiles come to a play to help you get things done.

In this article, we are going to demonstrate how this powerful feature works in general and how it applies to most common interoperability scenarios in real UC world.

Let’s begin.

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SIP Response Codes Explained

Why don’t we start with some trivia?
Did you know that SIP response codes are based on HTTP/1.1 response 404-not-foundcodes?

Actually, SIP response codes are the extent of the original HTTP ones and even define a new class with more response codes. I’ll let you know which one when we get to it.

That said, not all of the HTTP codes are relevant and mapped to SIP response codes, so if you know some HTTP, don’t expect to find them all in this list.
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Cisco SIP Gateway configuration: The Ultimate Guide

Connecting the Cisco IOS Voice Gateway to CUCM via SIP has been the preferred way to do it in the past couple of years.

The slowly dying H323 protocol (ISDN based) is not being developed anymore while SIP (HTTP based) became the industry standard for VoIP. So whenever PSTN connection is implemented via an IOS Voice Gateway, the choice should be really between SIP & MGCP.

This is how it’s done, step by step, using SIP.

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