GPRS Tunnelling Protocol (GTP) is a group of IP-based communications protocols used to carry general packet radio service (GPRS) within GSM, UMTS and LTE networks. In 3GPP architectures, GTP and Proxy Mobile IPv6 based interfaces are specified on various interface points.
What is the GTP proxy challenge?
Certain Operators have sponsored/inter-standard roaming agreements with other Mobile Network Operators (MNO’s) who use a dual IMSI solution that employs the visited IMSI for roaming. Problem is that for data connections the other MNO end-user's mobile will use the APN’s known from the IMSI of the VPLMN while the APN should be used by his HPLMN of the other MNO. Today the mobile phone tries to setup a data connection to GGSN/PGW of the VPLMN instead of GGSN/PGW of the other MNO.
There is no ideal solution available to solve this issue. The idea is to address this in the network via manipulation on a so-called GPRS Tunneling Protocol Proxy (GTP proxy). Until now there wasn't a commercial off the shelf product available.
Our GTP proxy solution
Our solution acts as a GTP proxy meaning that for GTPv1 and GTPv2 control-plane traffic Nomios' solution terminates the GTP tunnel and analyses the IMSI. In case the IMSI from the other MNO is recognized by checking a configuration table holding IMSI sub-ranges then Nomios opens a new GTP tunnel and sends the request to the known Gateway GPRS Support Node/Packet Gateway (GGSN/PGW) of the real Home MNO and potentially also manipulates the APN name inside the request so it can access the known APN on the own Home MNO's GGSN/PGW. The configuration table is easily configurable by the VPLMN engineers.
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