Cisco Cisco ASR 5000
Serving GPRS Support Node (SGSN) Overview
▀ Features and Functionality
▄ SGSN Administration Guide, StarOS Release 18
At this time, the Gn/Gp-SGSN supports the following APS/MSP parameters:
1+1 - Each redundant line pair consists of a working line and a protection line.
uni-directional - Protection on one end of the connection.
non-revertive - Upon restoration of service, this parameter prevents the network from automatically reverting to
the original working line.
The protection mechanism used for the APS/MSP uses a linear 1+1 architecture, as described in the ITU-T G.841
standard and the Bellcore publication GR-253-CORE, SONET Transport Systems; Common Generic Criteria, Section
5.3. The connection is unidirectional.
standard and the Bellcore publication GR-253-CORE, SONET Transport Systems; Common Generic Criteria, Section
5.3. The connection is unidirectional.
With APS/MSP 1+1, each redundant line pair consists of a working line and a protection line. Once a signal fail
condition or a signal degrade condition is detected, the hardware switches from the working line to the protection line.
condition or a signal degrade condition is detected, the hardware switches from the working line to the protection line.
With the non-revertive option, if a signal fail condition is detected, the hardware switches to the protection line and does
not automatically revert back to the working line.
not automatically revert back to the working line.
Since traffic is carried simultaneously by the working and protection lines, the receiver that terminates the APS/MSP
1+1 must select cells from either line and continue to forward one consistent traffic stream. The receiving ends can
switch from working to protection line without coordinating at the transmit end since both lines transmit the same
information.
1+1 must select cells from either line and continue to forward one consistent traffic stream. The receiving ends can
switch from working to protection line without coordinating at the transmit end since both lines transmit the same
information.
Figure 4.
SONET APS 1+1
Refer to the section on Configuring APS/MSP Redundancy in the SGSN Service Configuration Procedures section for
configuration details.
configuration details.
Authentications and Reallocations -- Selective
Subscriber event authentication, P-TMSI reallocation, and P-TMSI signature reallocation are now selective rather than
enabled by default.
enabled by default.
The operator can enable and configure them to occur according to network requirements:
every instance or every nth instance;
on the basis of UMTS, GPRS or both;
on the basis of elapsed time intervals between events.
There are situations in which authentication will be performed unconditionally:
IMSI Attach – all IMSI attaches will be authenticated
When the subscriber has not been authenticated before and the SGSN does not have a vector
When there is a P-TMSI signature mismatch