PDP Context

By Zahid Ghadialy (zahidtg@yahoo.com)

Last Updated: 02/02/2008

What is PDP Context and whats the difference between Primary and Seconday PDP Context?

Please refer to the PDP Context Tutorial in Tutorials Section.

Can you please tell me what AT commands to use to Secondary PDP Context activation? We use AT+CGATT for Primary PDP Context activation.

The following AT commands are generally used for PDP Context activation:

Format: AT+CGDCONT=<cid>,<PDP_type>,[<APN>,[<pdp_addr>]]
Example 1: AT+CGDCONT=1,”IP”
Example 2: AT+CGDCONT=1,”IP”,”internet”

Where

<cid>: Local PDP Context Identifier. A numeric parameter which specifies a particular PDP context definition and can be quoted in other PDP context related commands as reference (e.g. in AT+CGDSCONT, AT+CGTFT, AT+CGEQREQ, AT+CGACT, etc.)

<PDP_type>: Packet Data Protocol Type. A string parameter, typically “IP” is used (for IPv4)

<APN>: Access Point Name. A string parameter (case insensitive) which is used to select an access point in the GGSN. If the value is null (“”) or omitted, the subscribed value will be requested.

<PDP_addr>: PDP Address. A string parameter that identifies the MT in the address space applicable to the PDP. In case of IP PDP type this means the IP address. If the value is null or omitted the TE may provide the address (which will be used at PDP context activation) or a dynamic address will be requested and assigned by the GGSN. Typically dynamic IP address assignment is used (dynamic HPLMN PDP address).

For Secondary PDP Contexts

Format: AT+CGDSCONT=<cid>,<p_cid>
Example 1: AT+CGDSCONT=2,1
Example 2: AT+CGDSCONT=3,1

Where

<cid>: Local PDP Context Identifier. A numeric parameter which specifies a particular secondary PDP context definition and can be quoted in other PDP context related commands as reference (e.g. in AT+CGTFT, AT+CGEQREQ, AT+CGACT, etc.)

<p_cid>: Primary PDP Context Identifier. The secondary PDP context will be associated with this (already defined) primary PDP context.

Note:

  • The primary PDP context with the identifier has to be defined in advance (with the use of AT+CGDCONT)
  • Context identifier(s) already assigned to primary context(s) can not be used for the secondary context(s) (i.e. the context identifier pool is common for all the primary and secondary contexts)

References:
3GPP TS 27.007: AT command set for User Equipment (UE)





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