Gateway GPRS support node (GGSN) 相关资料

GPRS core network

http://en.wikipedia.org/wiki/GPRS_core_network

这篇文章有对GPRS（ general packet radio service  ） 的结构和 GGSN的功能和接口有所介绍。

GGSN 主要是连接外部IP网络和内部SGSN的关键部分。根据上篇文章要实现的结构有。

Gi

IP based interface between the GGSN and a public data network (PDN) either directly to the Internet or through a WAP gateway.

Gmb

The interface between the GGSN and the Broadcast-Multicast Service Center (BM-SC), used for controlling MBMS bearers.

Gn

IP Based interface between SGSN and other SGSNs and (internal) GGSNs. DNS also shares this interface. Uses the GTP Protocol.

Gx

The on-line policy interface between the GGSN and the charging rules function (CRF). It is used for provisioning service data flow based on charging rules. Uses the diameter protocol.

Gy

The on-line charging interface between the GGSN and the online charging system (OCS). Uses the diameter protocol (DCCA application).

其中的关键实现部分是用 GPRS tunnelling protocol (GTP)  协议来传输  Packet Data Protocol (PDP) context

GTP协议的wiki介绍

http://en.wikipedia.org/wiki/GPRS_Tunnelling_Protocol

相关的开源项目有openggsn

https://github.com/chantra/openggsn

开源的GTP协议实现

http://www.amitchawre.net/nw-gtpv2.html