Webbing Network Events Log Training

Modified on Wed, 9 Apr at 2:23 PM

Main Network Elements & Roles

VLR: Visitor Location Register
HLR: Home Location Register – maintains subscriber database and profile
SGSN: Serving GPRS Support Node – temporary subscriber DB & profile for data services
MME: Mobility Management Entity – temporary subscriber DB & profile for LTE
OTASMSC: SMS Center – manages SMS (text and OTA)
PGW: Packet Data Network Gateway – handles APN management, IP allocation, QoS, internet breakout, and usage counting
RADIUS: Used for IP allocation, APN allocation, and reporting

Basic Network Procedures

Send Authentication Info: Authentication and keys exchange (not visible in the network events log)
Update Location: Registration updates via SGSN/VLR/MME to provide the subscriber profile (ISD)
Create PDP Context (2G-3G) / Create Session (4G): Establish the GTP tunnel (not visible in the log)
Access Request: IP/APN allocation; PGW signals to return the SIM internal IP
Accounting Start: Initiates GTP session and logs PDP/Bearer details (APN, IP, etc.)
Accounting Stop: Ends the session and reports usage units
Accounting Interim: Usage/time-based reports (triggered after every 10MB of data usage)
Purge: HLR signaling event indicating disconnection
Purge MS/UE: Specific purge events for 2G/3G and 4G (LTE) respectively

Basic Roaming Structure

A simplified view of the roaming framework:

VLR + MSC
HLR
SGSN
MME
OTASMSC
PGW
RADIUS
SGW
Internet (spanning 2G, 3G, 4G, and local network HPLMN core)

End-to-End Connectivity

Network Selection: Involves scanning available networks, IMSI selection, and a combined decision by device and SIM logic
Registration & Authentication: Device and network registration along with location updates
APN Resolving & IP Allocation: Steps include APN mapping, dynamic/static IP allocation, DNS assignment, and session management
Data Transmission: Occurs once the data session is fully established

Registration Network Events

3G Registration: Events related to 3G network attachment (including location updates on VLR and SGSN)
4G/LTE Registration: Includes both combined attach and data-only attach events

Data Session Creation

Activation of PDP context / session request from the device
APN resolving and session request routing from the roaming network to the home network
Radius access and accounting to monitor the session

APN Mapping & IP Allocation

Static/Dynamic IP allocation
Session management
DNS assignment
Charging details

APN Resolving

Resolution typically via DNS at the network side (e.g., using PGW for IP address resolution)
Example: Apn.mnc035.mcc454.gprs???

Data Session Creation in Network Events

Visual representation of network events corresponding to session creation.

Data Transmission

Details the transmission of data within an established session.

Common Issue Scenarios

Roaming Not Allowed: Occurs when a specific network is not permitted for roaming with the given subscription.
APN Issues: Wrong or missing APN settings can lead to connection problems.
VPLMN PROD Block: Indicates that the network is blocked by the product configuration or an exclusion profile.

Network Events Log Filters

The network events search can be filtered using various parameters:

Main Type: The primary network element involved (e.g., HLR, PGW)
Type: The signaling message type
Status: Event outcome (Error, Information, Reject, Success)
Sub Status: Specific cause code for the event
Source: Which network element captured the event
Filters by ICCID, IMSI, MSISDN, IMEI (SV), SD, Country, VPLMN, MCC/MNC, Technology Generation (2G,3G,4G)
Dates: Time range for the events search

SMS OTA

Note: SMS used for over-the-air (OTA) updates are not visible in the network events log.

HTTP OTA Delivery & Force Polling

BIP (Bearer Independent Protocol): Facilitates the OTA server polling session using a different IP range.
SIM Timer: Every 7 days, the SIM will request the device to open a BIP session.
Device Reboot: Initiates BIP upon reboot.
Force Polling: Triggers BIP via an SMS command.

Additional Notes

This training provides an overview of end-to-end connectivity, including essential network elements, registration and session creation, common issues, and how to filter and analyze network events.