Cisco Cisco ASR 5000
Attach Rate Throttling
How it Works ▀
SGSN Administration Guide, StarOS Release 18 ▄
How it Works
Attach Rate Throttling Feature
The Mobile Stations access the services of a GPRS Network by attaching themselves to the network through SGSN
nodes. The SGSN can process more than “5000” such attach requests per second. In a typical network the SGSN can be
connected to other network elements over a narrow band link and these network elements may not able to process
requests at high rates such as the SGSN. This may lead to an overload condition in other network elements. To prevent
such scenarios, the Attach Rate throttling feature is designed, this feature limits the rate at which the SGSN processes
requests.
nodes. The SGSN can process more than “5000” such attach requests per second. In a typical network the SGSN can be
connected to other network elements over a narrow band link and these network elements may not able to process
requests at high rates such as the SGSN. This may lead to an overload condition in other network elements. To prevent
such scenarios, the Attach Rate throttling feature is designed, this feature limits the rate at which the SGSN processes
requests.
The diagram below depicts the high level software architecture in a SGSN node:
Figure 22. Software architecture in a SGSN node.
In a SGSN node the Link Manager/Gb Managers and the IMSI Manager perform the following tasks:
1. Link Manager/GbManager:Manages the links towards different network elements such as RNC, HLR so on. The
Attach requests and ISRAU requests received on the Link Manager/Gb Manager are sent to the IMSI Manager.
2. IMSI Manager: The IMSI Manager assigns the new connection requests to the various Session Managers. The
assignment is done after verifying the load on the Session Managers. The Attach Rate Throttling feature is implemented
at the IMSI Manager.
at the IMSI Manager.
The IMSI manager is responsible for identifying the Session Manager to handle the incoming requests. The requests are
then queued for the identified Session Manager. These queues are processed at the maximum possible rate. With the
introduction of Attach Rate Throttling feature, an intermediary queue is introduced which buffers the incoming requests
and processes these requests at the rate configured by the operator. The requests from the intermediary queue are
then queued for the identified Session Manager. These queues are processed at the maximum possible rate. With the
introduction of Attach Rate Throttling feature, an intermediary queue is introduced which buffers the incoming requests
and processes these requests at the rate configured by the operator. The requests from the intermediary queue are