Moxa ANT-WSB-ANM-05 Manuel D’Utilisation
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Cellular Networks
APN in Packet Switch
Each external network is given a unique Access Point Name (APN) that is used by the mobile user to establish
the connection to the required destination network.
the connection to the required destination network.
• APN (Access Point Name)
- Access Point Name is a label according to DNS naming conventions describing the access point to the
external packet data network (PDN).
- An APN is a logical way to name a GPRS service.
- The Domain Name Service (DNS) server translates the APN into the GGSN IP address.
- APN string naming comes from the mobile operator. There is no common rule so customers need to
- The Domain Name Service (DNS) server translates the APN into the GGSN IP address.
- APN string naming comes from the mobile operator. There is no common rule so customers need to
request (1) GPRS service and (2) the APN string from their operator.
- Some operators offer different APNs according to the GPRS service level, such as public fixed IP
addresses, non-port blocking, or VPN.
• IP Address Allocation in GPRS
- Fixed addressing
IP address is stored in HLR
HLR sends IP address to SGSN, then SGSN sends IP address to the MS
IP address is sent to the MS when the MS wants to send data
HLR sends IP address to SGSN, then SGSN sends IP address to the MS
IP address is sent to the MS when the MS wants to send data
- Dynamic addressing
GGSN receives the IP address (DHCP/local address pool/RADIUS)
When the MS opens PDP context, GGSN assigns an address to the MS
When the MS opens PDP context, GGSN assigns an address to the MS
• Obtaining an IP Address
- From a local address pool on the GGSN
- Via DHCP
- Via RADIUS from an external RADIUS server
- From the customer’s network via an L2TP tunnel from the GGSN
- Via DHCP
- Via RADIUS from an external RADIUS server
- From the customer’s network via an L2TP tunnel from the GGSN
PDP context activation procedures are as follows:
1. Mobile phone sends out PDP context activation request and other relative parameters (e.g.,APN, QoS)
2. SGSN begins verification based on previously stored GPRS Attach information
3. DNS mechanism in SGSN analyzes the APN and returns a GGSN address
4. SGSN and GGSN build logic links
5. GGSN will instruct an IP address for the mobile phone and send it to the MS via SGSN. The external
2. SGSN begins verification based on previously stored GPRS Attach information
3. DNS mechanism in SGSN analyzes the APN and returns a GGSN address
4. SGSN and GGSN build logic links
5. GGSN will instruct an IP address for the mobile phone and send it to the MS via SGSN. The external
network can then start a session with the MS.