November 22

Yiz Segall

What do the Network Events in your connectivity portal mean?

IoT Core Networks Explained

Network events tell the story of your SIM card. These events go far beyond knowing how much data a SIM card is using. It is the behind the scenes of your connectivity. 

Understanding the relationship between network events can help you identify and troubleshoot breakdowns, find unusual activity, protect against potential security breaches and understand how active your device really is.

Understanding the Categories of Network Events

Cellular connectivity is a highly sophisticated technology, designed to allow global operation on any supporting network, seamless handover between cells to ensure a continuous connection and experience as well as the ability to bill customers for their actual usage.

Connecting to a cellular network – any network – involves many smaller steps and multiple message exchanges between the device and the (core) network, all defined under the global protocol called “Signaling System #7”, or SS7.  These range from authentication, registration with the network, and determining the device’s usage profile, to negotiating the actual data session. 

These network events can be consolidated into several categories:

In this article, we will look at each category, and dive a bit deeper on the technical information you can retrieve from each. Psst: Keep reading until the end for an exclusive list of terms! 

Registration

Send Authentication Info

Description

This is used for validation. There are unique authentication details on both the SIM & the core network, which work like security keys. This event sends those details with a special state token. If the results and the state token are the same on both, then the SIM has been validated and can use the network.

Remember, for 4G networks, If this event is successful, it will retrieve a 5-6 digit MCC/MNC (Mobile Country Code/Mobile Network Code). When using 3G, it retrieves a Global Title.

Triggers

This event is triggered before any new registration attempt. In some networks, it is done before any device-originated activity, for example starting a call or a data session.

Associated Events

You may  see one or more of the following events after this:

Authentication Failure Report

Description

In some cases, the ‘Send Authentication Info’ event doesn’t go as planned. For a SIM to authenticate on a network, the authentication details in both the core network and the SIM need to be the same. If they don’t match, the SIM will return a failure. Many networks will send a report that says ‘fail to authorize’.

Triggers and Associated Events

This will be a direct result of a failure during the Send Authentication Info event

Update Location

Description

This event is the way that you will be informed of an update to the location of the device on either a 3G & 4G network. If this event is successful, for 4G networks, it will retrieve a 5-6 digit MCC/MNC (Mobile Country Code/Mobile Network Code). For 3G connections, a Global Title will be retrieved. The location may be the Cell ID, Location Area Code (LAC), SGSN/SGW address etc.

Triggers

When will this event occur? This network event is triggered every time there is a new registration, or if the device changes its location. In some networks, this is sent periodically on a schedule, usually every 24 hours.

Associated Events

Before this event, you should see ‘Send Authentication Info’.

Afterwards, if successful, you will see ‘insertSubscriberData

Update GPRS Location

Description

For 2G carriers, Update Location is not available, and instead, you will use Update GPRS Location from the SGSN (Serving GPRS Support Node).

Triggers

A new registration or a change to device location will trigger this event on 2G networks, after using Send Authentication Info.

Associated Events

Cancel Location

Description

Whenever an ‘Update Location’ returns a new location, a new subscriber profile is created. At that time, the old subscriber profile that was used for the previous location needs to be deactivated and replaced. 

Triggers

If device information is returned with a new location via the ‘Update Location’ event, the Cancel Location event will be sent directly from the core network. floLIVE’s webAPI can also automatically trigger this for best practice security and control. 

Associated Events

Purge MS

Description

Within the core network, there are 2 different elements that control roaming SIMs and local SIMs. They are the VLR (or MME for 4G) for roaming, and the HLR (HSS in 4G). This event will be used when the roaming network informs the local network that certain subscribers are no longer available.

Triggers

There will be different triggers depending on the network in question. Most networks conduct periodic checks, usually every 24 hours, and then send this event for all SIMs which haven’t experienced any activity for at least 24 hours. However, some networks don’t check at all. 

There are other use cases for a Purge MS event. For example, when using 4G, after the Update Location is used during registration, if the SGW is unable to create a session in the PGW for any reason (wrong APN, wrong DNS, no billing, etc), then the MME will send a Purge MS event.

 

Subscriber Info

insertSubscriberData

Description

Once a SIM has been authenticated, a subscriber profile is created or updated that tells the network what this particular device/SIM is capable of doing. It has other elements attached to it like registration details, any APNs, restrictions and location. This event occurs when this subscriber profile needs to be updated. 

This event occurs to update the core network element responsible for handling subscriber profiles.

Triggers

Any changes to the current subscriber profile will trigger this event, including a change in location from ‘Update Location’ or ‘Update GPRS Location’. 

This event can also be triggered when any change is made to the SIM profile through an API for example, or through a connectivity management platform (CMP).

Associated Events

deleteSubscriberData

Description

What about when elements of a subscriber profile are removed? When certain capabilities of a subscriber are deleted, the subscriber profile in the core network will need an update. This event is only sent when editing the current subscriber profile. In cases where a new subscriber profile is created like ‘Update Location’, this is not sent.

Triggers

This event will be triggered by any changes in the profile that removes any functionality

Restore Data

Description

Remember we spoke about the MME and VLR/MSC, the two elements in the core network? This event is used when either of these elements wants to get the information from the subscriber profile without going through the event ‘Update Location’. Caution! This is very rare. This could also indicate a security issue and third party sources are blocked.

Triggers

An IMS program that just wants to read profile to check a billing element

Associated Events

insertSubscriberData 

Any Time Interrogation

Description

This event is one which usually signals a high level of risk. The event retrieves all the information about a subscriber. As this is very rare, it is usually considered a security threat. floLIVE blocks this as standard. 

PSI

Description

Usually initiated by an external source or third party, this event retrieves all the information about a subscriber. This is very rare and is usually considered a security threat. As a result, it’s blocked by most networks. 

Calling

SRI (Send Routing Info)

Description

This is a two part exchange, alongside PRN. When an incoming call comes to a subscriber, MSCGMSC sends an SRI event to the Core Network to get the MSRN (Mobile Subscriber Roaming Number).

The expected result is the MSRN, but the second part of the exchange is the PRN, below. 

Triggers

Any incoming calls

Associated Events

PRN

PRN (Provide Roaming Number)

Description

After SRI, the PRN event makes the request from the core network to the destination MSC.  It tells the MSC (which maintains all the subscriber profiles) to provide the MSRN to the requester (i.e. the incoming call) and can also return information about Call Forward, Terminating Triggers, and errors.

Triggers and Associated Events

SRI

IDP (Initial Detection Point)

Description

In some cases, when an incoming or outgoing call is made, there is a need to understand the details of the call. You might want to know who called, where the call came from, the destination number, how long the call was for, and how it ended. 

This is even more essential when there is some kind of control on the plan. For example it may be prepaid, or if there could be overages to consider, or simply a usage cut off point. 

For these types of plans, before the network allows a call to start, it needs to know if the SIM has already reached any limits. So it sends this event to get prior usage details.

The order of events for incoming calls will generally be SRI, then IDP, then SRI with CAMEL (protocol) suppress and then PRN.

Triggers

When a subscriber tries to set up a call

Associated Events

Messaging

SRI for SM (Send Routing Info for Small Messages)

Description

Think about this event as the same as SRI but instead of for calls, for SMS. It asks for the location of MSISDN. It gets the location and the SIM. 

It’s usually preceded by the MO SMS event but only if the request came from a device itself. If the SMS request comes from a different source, like an API, you will see this event without the MO SMS event. 

Triggers

Incoming SMS

Associated Events

Report SM Delivery Status

Description

When an incoming SMS completes SRI for SM, it sends an event called MT SMS. This is the actual sending of the SMS. 

What happens if it doesn’t deliver as planned? If there is a temporary error, a two-stage process occurs. First the SMSC requests the HLR for an update when the device is ready. The HLR gets this from making a request to the MSC. Remember, this only occurs when there are temporary errors. Something more permanent would have failed in MO SMS or SRI for SM. The second stage is actually letting the SMSC know that the device is ready.

Triggers

This event occurs when SMSC receives a temporary error message when trying to send an SMS.

Associated Events

Ready for SM

Description

When the SMSC sends the Report SM Delivery Status event, this triggers the MSC to search to see when the device is ready. When it is ready, it sends a ‘Ready for SM’ event to the HLR. This is the equivalent of the green light, to notify the SMSC. The HLR then sends that alert through ‘Alert SC’. 

Triggers

When a device signal has been found.

Associated Events

Alert SC

Description

All systems ready to go! This event sends the SMS Mobile Subscriber (SMSC) the alert that the device/subscriber is ready to receive the message. This then triggers another SRI for SM and, if all goes well, MT SMS

Triggers

HLR receives a notification from MSC that device is ready to receive SMS

Associated Events

MO SMS (Mobile Originating SMS)

Description

When a device sends an SMS, this is step one. Think of this as the originating event that sets into motion all the other events related to sending an SMS to a device.

Triggers

Triggered by the originating device when it tries to send an SMS

Associated Events

MT SMS (Mobile Terminating SMS)

Description

End of the road. This is the event at the end of the SMS sequence, when the SMS has been sent, and delivered as planned. This states that the device can be contacted and hasn’t returned any temporary or permanent errors.

Triggers

When the target device returns a successful active record using the SRI for SM event. 

Associated Events

USSD (Unstructured Short Data)

Description

Although this is another way to send information between devices & HLR, it is much less common. 

Triggers

Sends IMEI

Data Sessions

Create PDP (Packet Data Protocol)

Description

The start of a new data session.

Associated Events

AAA Access Request (Accounting Access Authorization)

Description

Depending on the APN, sometimes a rate request is requested from the rating server to see how much is left on the plan. If the request is accepted and the data quota hasn’t been used up, then a data session is created. If not, it will be denied. In other words, it checks to see that the SIM hasn’t gone over its data plan.

Triggers and Associated Events

Create PDP

AAA Accounting

Description

This event allocates an IP address for the device in question. Sometimes the IP is allocated between the PGW and Radius server, but that will depend on the APN.

Triggers and Associated Events

AAA Access Request

Close PDP (Packet Data Protocol)

Description

When the device stops transmitting data, this is the end of the data session, and will trigger a network event to display this information. 

Associated Events

GGSN Keep Alive (Interi)

Description

Most data sessions are short. However, for long data sessions, such as those coming from devices which need to stream data for hours at a time, session details need to be updated periodically. This usually happens to check data usage against plan limits.

Triggers

For long data sessions, this event is usually triggered once per hour

Associated Events

GGSN Modify Bearer

Description

Sometimes during a data session, something fundamental changes. Perhaps the  device changes location or switches carriers, or maybe it changes from a 4G band to a 3G band. 

Usually this would need an ‘Update Location’ or ‘Send Authentication Info’ event to update the MSC, but this could cause disruption or impact performance. In order not to disrupt the data session, a GGSN Modify Bearer is sent to keep the active MSC alive but to still request and log the new information.

Triggers

Any change in the server node during a data session

Associated Events

Translating Network Events for Greater Insight and Understanding

From the point of registering a device, through to understanding subscriber and device data, making and receiving calls, dealing with incoming and outgoing messages, and diving into data sessions, your network events are the key to unlocking greater insight into each and every SIM. 

We hope this deep dive into network events has helped you to peek behind the curtain of your devices, and get greater insight into how to recognize key milestones and triggers for your IoT environment. Any questions about these events, or any others? We’re always here to help! 

Talk Network Events Like a Pro: Your Exclusive List of Key Terms

TermDefinition
GGSNGateway GPRS support node (3G/UMTS)
Core NetworkThe system that manages all the authentication and activities that a SIM card can make. In a 3G core network, it would include components like the HLR and VLR which manages subscribers on the home and roaming network. In a 4G core, it is the HSS and MME, respectively.

 This also allows access to the PGW (Packet Gateway) to allow for internet access, as well as calling, sms, etc.

PGWPacket Data Network Gateway (4G/LTE)
LACThe Location Area Code (LAC) is a unique number given to each geographic area within a mobile operator’s network. Every LAC consists of one or more cells
Cell ID (CID)A unique number given to each cell in a cellular radio network
MMEMobility Management Entity
SMSCShort message service center
MSCMobile Switching Center
USSDUnstructured Supplementary Service Data
HLRHome Location Register (2G/3G)
HSSHome Subscriber Server (4G)
RADIUSRemote Authentication Dial-In User Service
SGSNServing GPRS Support Node (3G/UMTS)
SGWServing Gateway (4G/LTE)
MSC-VLRVisitor location register
MSRNMobile Subscriber Roaming Number
MCCMNCMobile Country Code/Mobile Network Code
MOMobile Originating
MSISDNMobile Station International Subscriber Directory Number
GMSCGateway for Mobile Switching Center
CAMEL A protocol that controls the signaling of voice calls.

November 22

Yiz Segall

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