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S1AP View of LTE Attach and EPS Bearer Setup

This sequence diagram looks at LTE Attach and EPS Bearer Setup from the S1AP vantage point. The following signaling is covered:

  1. UE Attach, authentication and security signaling
  2. Setup of two EPS Bearers (RAB id 5 and 6)
  3. Release of UE context due to inactivity
  4. Reestablishment of the UE context with a Service Request.

You can click on individual messages in the sequence diagram to see field level details.

Click to see the "S1AP View of LTE Attach & EPS Bearer Setup"  sequence diagram

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Voice Over LTE (VoLTE) Originating Call

Voice over LTE (VoLTE) is the standard for voice call setup in LTE networks. When VoLTE is deployed, phones will not need to fallback to 3G for voice calls.

VoLTE uses IMS SIP signaling to set up voice calls. The following VoLTE call flow describes the IMS call setup and release. An example of sending an SMS over IMS is also included. Sample RTP and RTCP messages are also shown in the flow.
Voice over LTE Call Flow

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The Anatomy of an INVITE Request

SIP Adventures

As a high school student, I loved biology. I loved learning about the natural world and how our bodies function. The spleen was my friend — not to mention the pancreas, liver, and lungs.

Unlike many of my classmates, I didn’t mind dissecting frogs and the obligatory fetal pig. Okay, I wasn’t overly fond of the smell of formaldehyde, but it was mesmerizing cutting into the skin and exploring what lurked below.

I look upon SIP in a very similar fashion except instead of using a knife, my dissection tool of choice is Wireshark. Followers of this blog should already know that from reading my article, How to Debug SIP.   Wireshark is powerful software that not only captures SIP packets, but displays them in a very readable manner. On top of that, you can also capture and replay audio streams. If you want to call yourself a SIP professional…

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Visualize and Diagnose Wireshark PCAP Files with Sequence Diagrams

Introducing VisualEther Protocol Analyzer 6.1. Diagnose and debug Wireshark logs with sequence diagrams. Convert PCAP files into sequence diagrams and call flow diagrams by just defining the message fields that should be included in the diagrams. VisualEther takes of the rest, generating a well formatted sequence diagram. You can click on individual messages in the sequence diagram to see field level details.

VisualEther 6.1 adds the following features:

  • Full IPv6 Support
  • Convert any custom protocol to sequence diagrams. Fully customize the diagram generation.
  • Display message details as an expandable list.
  • Added support for Wifi and Ethernet frames

Wireshark to sequence diagrams

Visually debug protocol interactions


Generate sequence diagrams and call flow diagrams from Wireshark output. The sequence diagrams provide a visual trace of the packet flow between different nodes.

Use regular expressions to identify and flag error scenarios. Messages reporting session failure can be bookmarked in a PDF file, thus giving you quick access to the cause of failure. Protocol experts can identify the error scenarios upfront to speed up protocol debugging.

Summarize Wireshark output…

Wireshark Extraction Template

Define templates to select messages and the fields to be included in the generated diagrams. VisualEther analyzes the Wireshark output to generate documents that match the defined template. The template is defined as a simple XML file.

Support for IPv4, IPv6, Ethernet and Wifi is built in. TCP, UDP and SCTP transport layer support is also available out of the box.

You can customize the templates for any protocol that has an Wireshark dissector. Any custom source and destination addresses can be used to define the sequence diagram instance axes.

…while maintaining full message detail

Wireshark message shown in full detail.

Click on any message in PDF sequence diagrams. VisualEther shows you complete field level details of that message in a browser window.

The message nodes can be expanded and collapsed. This way you can focus on the part of the message that interests you.

Reverse engineer system design

Reverse engineer design from Wireshark

Reverse engineering system design by analyzing the message flow in an operational system. Design documents are generated from the Wireshark traces. The generated documents can be edited and reformatted using EventStudio System Designer.

Automate diagram generation from Wireshark PCAP Files

Wireshark to sequence diagram generation script

Automate capture of Wireshark logs with tshark and then use the VisualEther command-line mode to generate sequence diagrams and context diagrams.

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Sequence diagrams from Wireshark PCAP files

Announcing the release of VisualEther Protocol Analyzer 6.0.015 release.

VisualEther - Wireshark to Sequence Diagram Generation

  • Automate sequence diagram generation from the PCAP files with the built in command-line support. VisualEther can now be invoked from a script.
  • Built in support for Wi-Fi and Ethernet messages
  • Simplified message field analysis with collapsible message definition
  • Improved filtering to weed out repeated packets like RTP packets and broadcast messages.
  • Full support for .cap, .pcap, .pcapng and their .gz counterparts
  • Improved bookmarking for important messages. Bookmarked messages are appear in the bookmark pane of your PDF reader.
  • Improved processing for large PCAP files. VisualEther now automatically splits large files.
  • Reduced memory footprint in sequence diagram generation

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LTE S1-interface handover between eNodeBs

LTE networks prefer using the X2 interface for performing inter eNodeB handovers. An S1 handover is a fallback for scenarios where X2 interface is not available.

As the name suggests, S1 handovers take place over the S1-interface. The MME and the SGW are involved during the handover procedure.

An interesting part of LTE S1 handovers is the indirect tunnel that is established to carry the downlink data during the handover process. Refer to the S1 handover call flow for a detailed signaling flow.

Inter eNodeB S1 handover in LTE