Cisco Cisco Packet Data Gateway (PDG) Documentation Roadmaps
New In This 8.0 Release
SGSN Features ▀
Cisco ASR 5000 Series Product Overview ▄
OL-22937-01
../../../GRAPHICS/Production/SGSN/NetShare_MOCN_v1.wmf
With these two configurations, the SGSN supports multiple scenarios such as MOCN with non-supporting UE, MOCN
with supporting UE, GWCN with supporting UE, and GWCN with non-supporting UE.
with supporting UE, GWCN with supporting UE, and GWCN with non-supporting UE.
NPU FastPath
TP6514
The NPU FastPath feature is proprietary and only available on the ASR 5000 SGSN systems. The purpose of this type
of internal direct tunnel is to optimize resource usage and reduce latency when processing GTP-U packets. Incoming
traffic passes through the switch fabric and the routing headers are changed to re-route traffic from the incoming
Network Processing Unit (NPU) of the ingress PSC directly to the outgoing NPU of the egress PSC. This means that
intervening NPUs and CPUs are by-passed. This provides the SGSN with router-like latency and increased node
signaling capacity.
of internal direct tunnel is to optimize resource usage and reduce latency when processing GTP-U packets. Incoming
traffic passes through the switch fabric and the routing headers are changed to re-route traffic from the incoming
Network Processing Unit (NPU) of the ingress PSC directly to the outgoing NPU of the egress PSC. This means that
intervening NPUs and CPUs are by-passed. This provides the SGSN with router-like latency and increased node
signaling capacity.
Figure 5.
SGSN NPU FastPath
../../../GRAPHICS/Production/SGSN/SGSN-FastPath_v3.wmf
Fast path is established when both ends of a tunnel are available. Two fast path flows are established, one for the uplink
and one for the downlink direction for a given PDP context.
and one for the downlink direction for a given PDP context.
If FastPath cannot be established, the NPU forwards the GTP-U packets to a CPU for processing and they are processed
like all other packets.
like all other packets.
The following situations will not have packets moved through FastPath:
Traffic Policing & Shaping
Subscriber Monitoring
Lawful Intercept (LI)
IP Source Violation Checks
Intra-SGSN RAU
Iu-connection release
QoS Traffic Policing per Subscriber
The SGSN now offers QoS traffic policing which enables the operator to configure and enforce bandwidth limitations
on individual PDP contexts of a particular traffic class. Traffic policing typically deals with eliminating bursts of traffic
and managing a traffic flow in order to comply with a traffic contract.
on individual PDP contexts of a particular traffic class. Traffic policing typically deals with eliminating bursts of traffic
and managing a traffic flow in order to comply with a traffic contract.
The SGSN conforms to the DiffServ model for QoS by handling the 3GPP defined classes of traffic, QoS negotiation,
DSCP marking, traffic policing, and support for HSDPA/HSUPA.
DSCP marking, traffic policing, and support for HSDPA/HSUPA.
The SGSN can police uplink and downlink traffic according to predefined QoS negotiated limits fixed on the basis of
individual contexts - either primary or secondary. The SGSN employs the Two Rate Three Color Marker (RFC2698)
algorithm for traffic policing.
individual contexts - either primary or secondary. The SGSN employs the Two Rate Three Color Marker (RFC2698)
algorithm for traffic policing.