Scaling up an LTE core network is a major challenge for operators, particularly the Diameter signaling load generated by user management, dynamic policy, and charging. Service providers, Operators and Original Equipment Manufacturers (OEM) are scaling their networks and networks elements for the extremely high volume of Diameter signaling traffic that is expected in the next few years.
Network elements such as the PCRF and OCS, along with the DRA, must be prepared for this expected traffic volume. These nodes have the difficult task of maintaining the state of the subscribers, one of the most valuable resources for a network operator. Charging systems such as the OCS will see high traffic volume as more LTE elements come online.
Part of the preparation is devising reasonable high availability (HA) schemes for the networks and the nodes that make up the networks. Since previously established performance and capacity expectations quickly become obsolete, testing these HA scenarios efficiently and effectively are of upmost priority for service providers and OEMs.
HA schemes can take many forms, including functional or geographical redundancy, load balancing, throttling, active/standby, hot backups, and combinations of these factors. Each scheme has its own advantages and disadvantages, including cost of implementing. Network operators and OEMs will choose the combination of capabilities that best matches their requirements, architectures, and network growth expectations.
Developing Solutions has simplified the testing of the HA scenarios with dsTest.
dsTest allows you to:
- Test and evaluate high availability and failover schemes;
- Test and evaluate load balancing scenarios;
- Simulate complex real world network scenarios;
- Evaluate network nodes, and the reaction of the network, before the nodes are placed into service;
- Simulate both Diameter servers and clients;
- Test several interfaces at the same time.
Consider the example in the diagram above. A pair of Diameter Signaling Controller/Diameter Routing Agents (DSC/DRA) is configured for Geo-Redundancy for PCRF and OSC clusters.
With dsTest, configure multiple PCEF and CSCF nodes each having a primary and secondary Diameter connection to the DSC/DRAs for the Gx, Rx, and Ro interface applications. This enables comprehensive DRA element protocol testing capability.
- Test the DSC/DRA network element’s ability to load balance across the Diameter interfaces from the client nodes to the PCRF and OCS clusters. Monitor the active subscribers on each PCRF and OCS to insure that the load balancing is in agreement with the load balancing configuration(s);
- During the test, disable the connections to one of the DSC/DRAs, or take one of the DSC/DRAs out of service. Verify the retransmission of in-progress messages is directed to the appropriate PCRF or OCS. This verifies the DSC/DRA’s ability to maintain the state of the subscribers in the appropriate PCEF and OCS.
- Test the DSC/DRA’s ability to throttle traffic by rejecting some of the retransmitted in-flight messages or new connections until the Policy and Charging clusters catch up. This will verify that throttling will prevent a PCRF or OCS from being overrun by traffic, a critical ability when a node goes down to avoid a domino effect.
By using dsTest client simulators, this specific example represents a test of the HA features of a Diameter Router and/or PCRF and OCS clusters.