Sgsnemu » History » Version 4

laforge, 09/06/2017 11:56 AM

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h1. sgsnemu
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@sgsnemu@ is part of the [[OsmoGGSN]] project and implements a Serving GPRS Support Node (SGSN) emulator. It can be used for testing Gateway GPRS Support Nodes (GGSNs), GPRS core networks as well as GPRS roaming connections.
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For more information abou the role of SGSNs and GGSNs, see
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The GPRS functionality and protocols has been standardized by the Third Generation Partnership Project (3GPP).  According to the 3GPP specificaitons, an SGSN has several interfaces. @sgsnemu@ emulates the GN/Gp interface which is used towards GGSNs.
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The Gn/Gp inteface can be seen as the uplink interface of the SGSN. It is used for communicating with a GGSN which is typically connceted to the Internet (or any other private IP network).  The Gn/Gp interface uses the GPRS tunneling protocol (GTP).  User data packets (typically IP packets) are tunneled over GTP, which again uses UDP over IP as underlaying transport.
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@sgsnemu@ will establish a number of tunnels (aka _PDP Contexts_) to the GGSN.  An internal ping facility will transmit ping requests through the established tunnels.  Alternatively, a local network interface can be created. In this case, @sgsnemu@ will forward packets between the local network interface and the established tunnels on the Gn/Gp interface.
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@sgsnemu@ uses the TUN/TAP driver for the local interface. A tun network interface is established for each tunnel established to the GGSN.
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@sgsnemu@ errors are reported using the Osmocom logging framework.
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For detailed syntax, please see the sgsnemu man page included in the [[OsmoGGSN]] distribution.  You can also access the man page at
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