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SIP call setup with authentication

This call flow shows the SIP call setup between a SIP client ( and a SIP server ( The flow also shows the RTP message flow between the SIP client and the Media Gateway (
The example covers the following:

  1. SIP invite from the client.
  2. The SIP server challenges the client to authenticate.
  3. The client responds to the authentication challenge.
  4. The call is connected.
  5. The call enters the conversation phase with RTP traffic.
  6. The SIP call is cleared.

SIP call flow with authentication

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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.

Explore more

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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



3G UMTS Originating Call Flow

3G UMTS Originating Call Flows

A 3G UMTS originating voice call call setup involves complex signaling to setup and release the call.

  • RRC (Radio Resource Control) signaling between the UE and RAN sets up the radio link.
  • RANAP (Radio Access Network Application Part) signaling sets up the session between the RAN and the Core Network (MSC).

Click on the image to see the full call flow. You can click on most RANAP messages in the call flow to complete field level details of the RANAP messages.

3G UMTS Originating Call with RRC and RANAP signaling

Click here for the 3G UMTS originating voice call flow 

Introducing VisualEther Protocol Analyzer 6

Generate Sequence Diagrams from Wireshark PCAP files

visually debug protocol interactions

Generate sequence diagrams and context diagrams from Wireshark output. The sequence diagrams provide a visual trace of the packet flow between different nodes. The collaboration diagrams give a birds-eye-view of the protocol interactions.

Sequence diagram generated from Wireshark PCAP file

summarize Wireshark output…

Templates for identifying Wireshark messages that should be included in the sequence diagram.

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

…while maintaining full message detail

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

Click on any message in the sequence diagram to see full message details.

reverse engineer system design

wireshark to message sequence chart generation template

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.

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LTE X2 Handover Sequence Diagrams

Let’s examine the X2 Handover in detail. We look at the X2 handover signaling procedure through sequence diagrams that focus on different aspects of the procedure.

The sequence diagrams presented here were generated with EventStudio System Designer.

LTE X2 Handover

Full signaling details are presented here.


Now we examine the same flow at a higher level of abstraction. The diagram focuses on the interactions between the mobile, eNodeBs and the MME/SGW.

UE Interactions

We now explore the signaling procedures that involve the UE.

Source eNodeB Role

Examine the interactions that involve the eNodeB that initiated the handover.

Target eNodeB Role

We now look at the interactions involving the eNodeB that will be serving the UE after the handover.

RRC Signaling the X2 Handover

The Radio Resource Control (RRC) signaling between the UE and the eNodeBs is covered here.

X2AP Signaling Between eNodeBs

X2AP is used for signaling between the eNodeBs. Here we examine the X2AP interactions.

Data Path Changes During an X2 Handover

The data path switching goes through several steps to accomplish a seamless handover.

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What’s New in EventStudio System Designer 6

Introducing EventStudio System Designer 6. A free 45 day trial is available for download.

New features in the release:

Message endpoint tagging

Specify tags

Tag the message source and destinations. This can be used to identify the endpoint port numbers, and specify the protocol layer or software entities.

“BSSMAP PAGING”: A-bssmap -> B-bssmap
HTTPGet : Client -> Server-“80”
Cascade : A-rr -> B-cc -> C-“80”
A-bcch multicasts SI to B-bcch, C-bcch
Cascade : A-cc -> B-cc -> C-rr
Chain1(par1,param2,param3):A-cc-> B-cc
Chain2: B-cc -> C-rr

Style tags

Each type of tag can be individually formatted. The color, font and font size may be specified. The styles for tags should be named as <tag>_tag_style. A few examples are shown below:

style rr_tag_style: color=RED, bgcolor=RED, textcolor=WHITE
style sccp_tag_style: color=DODGERBLUE, bgcolor=DODGERBLUE, textcolor=WHITE
style isup_tag_style: color=GREY, bgcolor=GREY, textcolor=WHITE
style bssmap_tag_style: color=MIDNIGHTBLUE, bgcolor=MIDNIGHTBLUE, textcolor=WHITE
style cc_tag_style: color=DARKSLATEGRAY, bgcolor=DARKSLATEGRAY, textcolor=WHITE
style bcch_tag_style: color=DODGERBLUE, bgcolor=DODGERBLUE, textcolor=WHITE
style “80_tag_style”: color=DODGERBLUE, bgcolor=DODGERBLUE, textcolor=WHITE

Tag specific diagrams

Use tags to filter and generate sequence diagrams that just contain messages with a specific tag.


Control the look and feel of documents with default styles. Automatically apply these styles that match regular expressions. For example, specify a style for all messages that start with specific text. Styles have been enhanced to change colors for the background, text, and parameters.

Group interactions with sequences

Simplified sequence definitions

Grouping interactions has been simplified. Just enclose the interactions in a sequence statement. EventStudio automatically identifies the interacting entities.

Nest sequences

Sequences may be nested. Quickly access a sequence from a PDF bookmark, which are nested too.

Collapse sequences

Complete sequences are shown the first time they occur in a sequence diagram. Subsequent occurrences of the sequence are shown as a simple clickable box. Clicking on the box takes the user to the expanded sequence.
module: Module_01
component: Component_01 in Module_01
eternal: a in Component_01, b in Component_01, c in Component_01
feature "Sequence Grouping"
  sequence "Call Setup"
     IAM : a -> b
     b takes action "Check digits"
     ACM : a <- b
     leg "Called Party Free":
       a, b take action "Set up the  voice path"
     leg "Called Party Busy": 
       a, b take action "Feed busy tone"
  sequence "Call Release"
     REL : a -> b
     RLC : a <- b

Classify systems with 5 levels of hierarchy

Generate sequence diagrams at any of the five abstraction levels.

Developers may work at the component and object level. System architects analyze the design at a system and subsystem level.

Improved modeling


Actions, which have a distinct beginning and ending, can be modeled with the new continuous action support. Also, actions may be specified at different levels in the hierarchy.


Lost messages can be modeled in sequence diagrams. Additionally, messages can be represented through a single simple statement.

“Lost Message”: A ->X B
“Message Cascade”: A -> B -> C

Enhanced tracing support

Flexible object interactions

Method invocation rules have been relaxed to make them compatible with sequence diagram generation from trace messages ( Method calls to caller classes are permitted.

Command line

Command line mode is used to generate sequence diagrams from scripts. The command line can now be customized with specific conditional defines and include paths.

Model large systems

Share instance axes

Large number of interacting entities need not result in a large number of axis in diagrams. Dynamic objects can share a single instance axis, thus reducing the total number of axes needed in a sequence diagram.

Really large sequence diagrams

Sequence diagrams can now run into hundreds of pages. This is useful when converting large trace documents to sequence diagrams.

XML export

Export scenarios and interactions to XML. This enables generation of custom diagrams and documents.

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IMS subscriber to PSTN subscriber call flow

IP Multimedia Subsystem is an IP based signaling system for setting up and tearing down multimedia sessions. SIP based signaling is used to setup these sessions.

We have covered call flows for an IMS to IMS and PSTN to IMS calls. We now look at the call flow for a IMS to PSTN subscriber call.

The call is routed via the BGCF (Border Gateway Control Function) to the MGCF (Media Gateway Control Function). The MGCF uses one context with two terminations in IM-MGW (Media Gateway). The termination RTP1 is used towards IMS Core network subsystem entity and the bearer termination TDM1 is used for bearer towards PSTN CS network element.

The call flow is complex and it is analyzed with multiple diagrams. Some of the diagrams are presented here:

IMS to PSTN sequence diagram

A detailed call flow describing all message interactions in a IMS to PSTN call

IMS to PSTN high level flow

A high level view that abstracts out individual component details and just presents the flow between the UE, IMS Core and the PSTN.

IMS to PSTN UE collaboration diagram

Here we examine the call flow from the UE point of view. The call flow is represented as a collaboration diagram.

Link: IMS subscriber to PSTN subscriber call flow

All documents:

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PSTN subscriber to IMS subscriber call flow

IP Multimedia Subsystem is the new IP based signaling system for setting up multimedia sessions. We have already covered the call flow for an IMS subscriber calling another IMS subscriber. Here we will look at the call flow of a regular PSTN subscriber calling an IMS user.

PSTN to IMS call flow

PSTN subscriber to IMS subscriber call flow

This call flow covers the handling of a CS network originated call with ISUP. In the diagram the MGCF requests seizure of the IM CN subsystem side termination and CS network side bearer termination. When the MGCF receives an answer indication, it requests the IM-MGW to both-way through-connect the terminations. Originating and terminating end initiated call releases are also covered.

The following sequence is covered:

  1. ISUP IAM Handling and Initial IM-MGW and MGCF (Mn) Interactions
  2. Initial Handshake between MGCF and IMS CSCF Servers
  3. Mn Interactions for Codec selection
  4. ISUP ACM related interactions on Mn interface
  5. IMS Answer to ISUP ANM Handling
  6. Conversation Mode
  7. Call Release:
    • Calling PSTN Subscriber Initiated Call Release
    • Called Subsciber Initiates Call Release

Link: PSTN subscriber to IMS call flows

Focus on different aspects of the call flow

PSTN to IMS call is a very complex flow. The main sequence flow is supplemented with flows that focus on a particular aspect of the flow. A snapshot of one such diagrams is shown here:PSTN subscriber to IMS subscriber - Terminating S-CSCF interactions

Link: PSTN subscriber to IMS call flows

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LTE Attach and Default Bearer Setup Sequence Diagram

LTE Attach and Default Bearer Setup

Click to open the PDF sequence diagram describing LTE attach and default bearer setup

This call flow describes the signaling involved in LTE attach and default bearer setup. The sequence diagram covers the following phases:

  1. Random Access Procedure: The UE uses a slotted aloha procedure to access the eNodeB. The UE sends a preamble on a random access channel, the network replies with corrected timing and resource assignments.
  2. RRC Connection Establishment: The UE and the eNodeB then interact to establish a Signaling Radio Bearer (SRB). The SRB will be used for the signaling between the eNodeB and the UE.
  3. Attach and Authentication: The UE now registers with the Core Network. Session contexts are setup at the MME and the Serving Gateway. This step also results in the authentication of the UE and the Network.
  4. Default Radio Bearer Setup: Finally, the default bearer for data transfer is established. Default bearer session is established at the UE, eNodeB, MME, Serving GW and PDN Gateway. User data sessions is exchanged once the default bearer is setup.

The sequence diagram also contains links to access further details about the messages. Click on the messages with blue title for details about the message.

RRC Connection, LTE Attach and Default Radio Bearer Setup