GSN-Lite Features

GSN-Lite as SGSN
GSN-Lite as GGSN
Combined GSN functionality

GSN-Lite as an SGSN

GSN-Lite, when deployed as an SGSN, handles inbound and outbound packet data traffic, addressed to/from mobile stations of users in a geographical area. In addition, it also handles interactions with the GSM circuit switched and the short messaging infrastructures.

As an SGSN, Aricent’ GSN Lite provides the following functionalities:

• Mobility Management: SGSN supports all mobility management functions including Attach, Detach, Inter, and Intra SGSN Routing Area Update (RAU) and Paging.
  
  SGSN supports HLR addressing, based on an E.214 Mobile Global Title, derived by the SGSN from the IMSI for inter-PLMN signaling (or on the SPC if intra-PLMN Signaling).
  
  
• Session Management: SGSN provides session management functions, including establishment of Packet Data Protocol (PDP) contexts, for routing purposes, with the GGSN used by the GPRS subscriber.
  
  At PDP context activation, the SGSN negotiates the Quality of Service (QoS) with the Mobile Station (MS) when the QoS level requested by the MS cannot be supported. The QoS is re-negotiated when the QoS, negotiated by the mobile from the previous SGSN, cannot be supported at inter-SGSN RAU.
  
  The SGSN supports reliability classes 2,3,4, and 5. and accepts all delay classes. However, there is no special processing done by the SGSN in terms of enforcing relative importance or absolute time values.
  
  The SGSN also supports the Admission Control function at each PDP context activation request. The Admission Control function results either in negotiation of the QoS with the mobile or in rejection of the PDP Context Activation request. A request is rejected when the number of simultaneously attached or activated subscribers increases beyond a specified value.
  
  The SGSN also supports Service Precedence classes by discarding the packets based on the Precedence Class negotiated by MSs.
  
  As a part of session management, the SGSN assists in mean and peak throughputs and policing. While it ensures that the mean and peak throughputs given to an MS never exceed the negotiated value, there is no guarantee that the mean or peak throughput rates can be achieved or sustained for any period.
  
  
• SMS: The SGSN supports mobile-originated and mobile-terminated short messaging through GPRS radio channels.
  
  
• Charging Functions: The SGSN supports Call Description Record (CDR) generation. M-CDRs, S-CDRs, SMS-MO-CDRs, and SMS-MT-CDRs generated by the SGSN are sent to the Charging Gateway over the Ga interface using the GTP’ protocol.
  
  
• Authentication and Identity Check: The SGSN supports mobile authentication and identity check procedures during 'Attach' and inter-SGSN routing area updates.
  
  
• Security: The SGSN supports encrypted communication to and from mobiles using GEA1 and GEA2 ciphering algorithms. The GSN-Lite software includes implementation of GEA1 and GEA2 ciphering algorithms.
  
  
• Compression: The SGSN supports TCP header compression using Van Jacobson and V.42bis data compression techniques to conserve radio bandwidth while sending data to and from a mobile station.
  
  
• Routing: The SGSN routes the packets received from a mobile to an appropriate GGSN, based on the APN requested by the mobile. The SGSN supports interrogation of the DNS to translate the APN into the IP address of the GGSN.
  

GSN-Lite as GGSN

The GGSN is primarily a router and in packet data networks, it routes packets to a GPRS mobile terminal. For packets sent by the mobile terminal, the GGSN is the 'point of entry' into the packet data network.

As a GGSN, Aricent’ GSN-Lite provides the following functionalities:

• Subscriber Session/Data Management: The GGSN assigns an IP address to a mobile station. The GGSN supports PDP context activation for PDP type IPv4.
  
  The GGSN supports dynamic IP addressing for subscribers to enable the operator to use and reuse IP addresses from a pool of IP addresses allocated to the PLMN/Network by using local pools configured at the GGSN. Alternatively, the GGSN may use DHCP for IP address allocation from a configured DHCP server on a 'per APN' basis.
  
  The GGSN supports static IP address allocation so that the subscribers are always provided the same IP address defined at the time of subscription in the HLR. Else, the RADIUS protocol could be configured to allocate the same IP address to a specific subscriber.
  
  A maximum of five PDP contexts are supported for one MS. There is one distinct IP address per PDP context. Negotiated QoS classes for the PDP contexts of an MS can be different.
  
  
• Charging Function: Charging function in the GGSN sends G-CDRs to the Charging Gateway. G-CDRs output from the GGSN are ASN.1/BER encoded. In case of a CGF/link failure, the CDRs are buffered in non-volatile memory (hard-disk) and are transferred to the CGF on CGF/link recovery.
  
  
• Routing: The GGSN routes the packets received from the SGSN to a default gateway, statically configured at the GGSN, and routes the packets received from an external PDN for a mobile to an appropriate SGSN serving the mobiles.
  
  
• Radius Accounting: GSN-Lite, when used as a GGSN, can be configured to send accounting information to RADIUS servers configured according to APN configuration rules. This facilitates the user to configure the network for applying accounting principles using the RADIUS mechanism.

Combined GSN functionality

As a combined entity, GSN-Lite supports the functionality of an SGSN and a GGSN as detailed earlier. The combined GSN can support Inter-SGSN procedures while acting as a GGSN in the Public Land Mobile Network (PLMN) in which it is deployed. It will continue to act as a GGSN for the subscribers who have roamed in another PLMN.

In addition, GSN-Lite can be configured to notify occurrence of any significant event or alarm to configured e-mail addresses. Features such as these are highly useful to monitor the system remotely.

Optional Procedures supported GSN-Lite supports the following optional procedures as per the specifications:

• Anonymous PDP context activation/deactivation procedures.
  
  
• Network-Requested PDP Context activation procedure. This is provided by the support of an optional Gc interface at the GGSN.
  
  
• Combined GPRS/GSM procedures for circuit switched services. This is provided by using the Base Station Subsystem Application Part + (BSSAP+) at the optional Gs interface at the SGSN.

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