VOIP, GSM and 3G Call Flows

The call flow diagrams were generated using EventStudio System Designer.

SIP and H.323 Call Flow Diagrams

SIP to PSTN Sequence Diagram

In this scenario, Alice is a SIP phone or other SIP-enabled device. Bob is reachable via the PSTN at global telephone number. Alice places a call to Bob through a Proxy Server (Proxy 1) and a Network Gateway (NGW 1).

SIP to ISDN PBX Sequence Diagram

Alice is a SIP device while Carol is connected via a Gateway (GW 1) to a PBX. The PBX connection is via a ISDN trunk group.

SIP Originating Call with Authentication

SIP originating call flow. The call flow includes the authentication procedure between the SIP client and server. All messsages in this flow can be clicked to access complete message structure.

H.323 Call Flow

The call flow diagram presents the flow of an H.323 call. Covers: H.225/Q.931 Call Setup; H.245 Negotiation and Voice Path Setup; RTP/RTCP Based Voice Communication

GSM Circuit Switched Call Flows

GSM Network Example

This example shows a few cells in a GSM network. We will be referring to this diagram in several sequence diagrams and call flows.

GSM Mobile Originated Call Flow

A detailed call flow of a GSM mobile originated call.

GSM Mobile Originated Call Flow - Explore More

GSM call setup is analyzed in detail. The role of each participant is documented with a separate call flow.

GSM Location Update Sequence Diagram

How does the cellular provider know where you are? Here we look at the location updating procedure initiated by mobiles to keep the cellular provider updated on their current location.

GSM Location Update - Explore More

GSM Location Update analyzed in detail. The role of each participant is documented with a separate sequence diagram.

GSM Mobile Terminated Call Flow

In this call flow we will look at how a terminating call is handled in GSM. Setting up a terminating call is a two step process. (1) Interrogation procedure to locate the subscriber (2) Actual call setup after the subscriber has been located.

GSM RR Call Flows

GSM Radio Resource Management (RR) Call Flows.

GSM RR Collaboration Diagram

GSM Radio Resource Management (RR) Collaboration Diagram.

GSM MM Call Flows

GSM Mobility Management (MM) Call Flows.

GSM MM Collaboration Diagram

GSM Mobility Management (MM) Collaboration Diagram.

GSM Mobile Originated SMS Session

This scenario describes the session setup for a GSM originating SMS. This sequence diagram describes the SMS signaling and data transfer between the mobile subscriber and the SMS service center.

GSM Mobile Terminated SMS Session

This scenario describes the session setup for a GSM terminating SMS. This sequence diagram describes the SMS signaling and data transfer between the SMS service center and a mobile user.

GSM Handover Call Flows

GSM Handover Call Flow (Intra MSC)

This call flow covers a simple case of call handover in GSM. Here a user has an active call and is moving from the Rockville Cell to the Bethesda Cell.

GSM Inter-MSC Handover Call Flow

This call flow describes the handover between two cells handled by different MSCs.

GSM Inter-MSC Handover Call Flow (Explore More)

Inter MSC handover is analyzed in detail. The role of each participant is documented with a separate call flow.

GSM GPRS Sequence Diagrams

GPRS Combined Attach and PDP Context Activation

The combined attach and PDP context activation of a Class B GPRS terminal will be covered here.

New SGSN Interfaces Attach and Activation

Sequence diagram listing all the interactions involving the new SGSN.

User Terminal Interfaces in Attach and PDP Activation

Sequence diagram summarizing the user terminal interactions in attach and PDP context activation.

3G UMTS Sequence Diagrams

3G UMTS Originating Call

Mobile originated 3G call that details RANAP and RRC signaling. Just click on RANAP messages to get full field level detail.

3G UMTS Terminating Call

Mobile terminating 3G call that details RANAP and RRC signaling. Just click on RANAP messages to get full field level detail.

ISDN User Part (ISUP) Call Flows

SS7 ISUP to ISUP Call (Called Subscriber Clears First)

An ISUP Incoming to ISUP Outgoing transit call is covered here. Call is released first by the called subscriber.

SS7 ISUP to ISUP Call (Calling Subscriber Clears First)

An ISUP Incoming to ISUP Outgoing transit call is covered here. Call is released first by the calling subscriber.

SS7 ISUP to ISUP Call (Failure Scenario)

An ISUP Incoming to ISUP Outgoing transit call is covered here. Call is released on receipt of call failed indication from called side.

V5.2 Protocol Call Flows

V5.2 to V5.2 Call (DTMF, Called Subscriber Goes Onhook)

Setup and release of a V5.2 subscriber to V5.2 subscriber call. Calling subscriber uses DTMF dialing and the called subscriber goes onhook.

V5.2 to V5.2 Call (Pulse, Calling Subscriber Goes Onhook)

Setup and release of a V5.2 subscriber to V5.2 subscriber call. Calling subscriber uses pulse dialing and calling subscriber clears first.

SIGTRAN Protocols

SCTP Sequence Diagram

Stream Control Transmission Protocol (SCTP) is a relatively new transport protocol in the IP stack. It has been designed to carry Telecom signaling protocols over IP.