Core devices
Mobile Station(MS)
Base Station System(BSS)
Serving GPRS Support Node(SGSN)
The dividing line between mobile stations and data net. Its tasks include packet routing and transfer, mobility management, logical link management, and authentication and charging functions.
Gateway GPRS Support Node(GGSN)
The dividing line between the GPRS network and external networks, like the Internet and
X.25 networks.
Other devices
Mobile Switch Center(MSC)
Short Message Service(SMS)
Home Location Register(HLR)
Core interfaces
Um
The air interface for the GSM mobile telephone standard between MS and BSS(BTS).
Gb
Interface between BSS and SGSN. The transmission protocol could be Frame Relay or IP.
Gn
IP based interface between SGSN and other SGSNs and (internal) GGSNs. Uses the GTP
Protocol.
Gi
IP based interface between the GGSN and a public data network (PDN) either directly to
the Internet or through a WAP gateway.
Other interfaces
Ga
The interface servers the CDRs (accounting records) which are written in the GSN and
sent to the charging gateway (CG). This interface uses a GTP(GPRS tunnelling protocol )
-based protocol, with modifications that supports CDRs.
Gd
Interface between the SGSN and the SMS Gateway. Can use MAP1, MAP2 or MAP3.
Protocol Distribution
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