GTPv2 Core Network Mobility Management
OpenEPC Rel. 2 supports GPRS Tunneling Protocol (GTP) core network mobility management. This includes the development of the Serving GW and of the PDN GW components for the GTPv2. For providing a smooth start with the GTPv2 core network mobility management, it can be directly integrated with the DHCP server. Furthermore, it can be integrated with the eNode core network part and with the MME providing a complete functionality for the LTE access. The GTP based core network mobility management is based on the 3GPP standard for GTP (specified in 3GPP TS 29.274 and 3GPP TS 29.281) and follows the 3GPP EPC S5 reference point specified in 3GPP TS 23.401
The OpenEPC Rel. 2 GTPv2 Protocol Stack can be instantiated as the GTP stack for the Serving GW and for the PDN GW. Its role is to create and to maintain a set of GTP tunnels for the currently connected users and to manage the data packets forwarding to and from these user endpoints. The data forwarding is done through tunnels between the PDN GW and the Serving GWs connected to it.
As all the other main OpenEPC components, the GTPv2 protocol stack features in all the component instantiations, a MySQL database as a storage back-end, enabling it to store and expose the state.
The GTP component of the PDN GW is able to perform IP address allocation upon a new and a subsequent attachment - providing both IPv4 and IPv6 addresses. For this, the same IP allocation module is used as in the case of Proxy Mobile IP based Mobility Management. It also can interact with the PCC enabling the relay of the Layer 3 attachment and detachment events.
The GTP component of the Serving GW is able to directly communicate with the GTP component which communicates with the MME (via the S11 reference point) and with the eNodeB (via the S1-U reference point). Through this interaction, core network related mechanisms for the LTE access network can be completely showcased through the usage of chained GTP over the S1-U and S5 reference points. Furthermore, direct communication with a DHCP server can be used in case of reduced deployments which do not include MME or eNode components. Communication with the GTP component of the PDN GW is realized via
Supported features:
- support for attachment and detachment procedures (based on the procedures from 3GPP TS 23.401 Section 5.3.2.1 and Section 5.3.8.2)
- support for default and dedicated bearer establishment, modification and termination (based on the procedures from 3GPP TS 23.401 Section 5.3.2.1, Section 5.4.1 and Section 5.4.4)
- dual IPv4/IPv6 supported for GTP signaling
- ability to use various types of tunnels (ipip RFC2003, sit RFC4213, ipip6 RFC 2473, ip6ip6 RFC 2473), covering all possible IPv4/IPv6 connectivity combinations
- modular architecture, enabling the replacement of key components (IP allocation module, Tunnel Control module) with custom implementations
Supported features for PDN GW:
- binding cache and IP allocation state saved in a MySQL database
- dual IPv4/IPv6 IP address allocation for mobile clients
Support features for Serving GW:
- communication with a modified ISC-DHCP server serving IPv4/IPv6 addresses
- communication with the core network part supporting the LTE access
Limitations:
- GRE tunnels are not supported (in development, but not part of current release).
- network triggered detachments are not supported for now.
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