The platform-independent IP Service Level Agreements (SLAs) is a feature embedded in Cisco software. It allows you to understand IP service levels, increase productivity, lower operational costs, and reduce the frequency of network outages. IP SLAs performs the active monitoring of the network performance and can be used for network troubleshooting, network readiness assessment, and health monitoring.
IP SLAs in Cisco software is incapable of generating the high data rates, 4 to 16 Mbps, which are typical of video applications. To eliminate the protocol overhead and the process scheduling delays that contribute to the limitations of the earlier IP SLAs software to generate video traffic, the Cisco IP SLAs Video Operation feature makes the traffic generation and transmission routines platform dependent. The Application programming interface (API) calls in the IP SLAs video operation software to enable a more precise timer interrupt than the general system timer, which is insufficient for the packet generation requirements for a true video stream. Devices that can act as a source or a responder for an IP SLAs video operation are limited to Cisco devices that are capable of providing platform-assisted video traffic generation and reflection.
An IP SLAs video operation differs from other IP SLA operations in that all traffic is one way only, with a responder required to process the sequence numbers and time stamps locally and to wait for a request from the source before sending the calculated data back.
The source sends a request to the responder when the current video operation is done. This request signals the responder that no more packets will arrive, and that the video sink function in the video operation can be turned off. When the response from the responder arrives at the source, the statistics are read from the message, and the relevant fields in the operation are updated.
Because all video operation traffic is one way, the responder is responsible for actually collecting and verifying the packets. The software that does packet count verification and time stamp jitter calculations is shared by both the source and responder. The responder stores this information until such time that the source requests the data, or a timer expires and the data is released.
Because the responder cannot directly read the video packets, the responder creates two queues and a block of reallocated memory for use by both video sink and the responder itself.
When a packet arrives at video sink, it is processed to extract the sequence numbers and time stamps, and that information is put into one of the pre-allocated memory blocks. A pointer to this block is put into the used queue for later processing by the main responder task.
At periodic timer intervals, the responder processes a number of the packet information blocks from the used queue and updates the statistics appropriately. When the data is processed, the blocks are returned to the free-memory list to be used again.
This procedure continues until the video operation is complete.