twork inside the network operator's infrastructure, and in the roaming interface between the network operators. The operator identifier is not usually visible to the user. However, sometimes the user may have to manually configure the network identifier part of the APN to their connection settings on a UE. An observant reader would notice a strange thing in the domain name that results from the APN: the Top Level Domain (TLD) is gprs. We discussed the DNS in Section 1.6, and how the DNS is managed. However, gprs has not been applied for through the Internet Corporation for Assigned Names and Numbers (ICANN) process, and it is managed by GSMA. Basically, the GSMA has created an alternate DNS root for the 3GPP network infrastructure. This gprs TLD is, however, only used for GPRS networks. The 3gppnetwork. org is used in EPS, and eventually will supersede the gprs TLD. However, it will take quite a long time before all GPRS networks have been replaced with EPS networks - if ever. The 3GPP DNS naming is described in [45], and the EPS procedures in [49]. The GSMA equivalent DNS document for both naming and procedures is [50], which relies entirely on the 3GPP counterparts. 2.5.3 Traffic Flow Template The concept of the TFT is relatively simple - it is a filter that identifies what kind of pack- ets are supposed to go down a certain PDP Context or EPS Bearer. There has to be always one PDP Context or EPS Bearer without a TFT associated to it. Hence, there is always a default connection where packets can pass through. On the other hand, the other Secondary PDP Contexts and dedicated EPS Bearers do need a TFT associated with them. Again, this is to make sure that the intended traffic will go through the connection. There is a TFT for downlink and uplink traffic to ensure that the packets go through the right connection regardless of their direction. There are eight different parameters that can be set in a TFT: local address [33, 51] remote address protocol number (IPv4) / next header (IPv6) local port range remote port 