ld like to have service on IPv4, IPv6, or both. The SGSN adds the PDP Context to its context table. 2. Create PDP Context request is sent by the SGSN to the GGSN. The GGSN adds the new PDP Context to its context data structure. The GGSN allocates the IP address or Deploying IPv6 in 3GPP Networks addresses to the context, and sets the Protocol Configuration Option (PCO) information and sends them in the Create PDP Context response to the SGSN. 3. Activate PDP Context response message is sent by the SGSN with the IP address and PCO information received from the GGSN. This finishes the PDP Context activation procedure. 4. The IP traffic can then start flowing over the new PDP Context. In GPRS, the procedure in Figure 2.13 is used for the first PDP Context activation, and for subsequent activations. There are two types of PDP Context activations: Primary PDP Context activations, and Secondary PDP Context activations. The same proce- dure described in Figure 2.13 is used for both Primary and Secondary PDP Context activations - the difference is the message 'Update PDP 'Context'. It is used in Sec- ondary PDP Context activation to update the actual received QoS in the radio bearer negotiation (not shown in the picture). The Primary PDP Context activation does not use this message. The difference between Primary and Secondary PDP Context negotiation is the Primary PDP Context activation allocates a new IP address for the PDP Context. Secondary PDP Context activation only opens a new connection related to an already active PDP Context using the IP address allocated to it. The Secondary PDP Contexts can be used for QoS differentiation where different traffic is transferred over a different PDP Context with a different QoS profile. Making an analogy to the physical world, if the Primary PDP Context is the highway, a Secondary PDP Context is a car pool lane (in the USA, this is a lane reserved for cars containing two or more people, and therefore being less congested than the other lanes). GPRS does not distinguish between 