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What is the maximum number of x25 SVCs supported on a Cisco 7204VXR

I have a number of Cisco 7204 VXRs with NPE300s being used as Encapsulation Engines for XOT. I have a requirement to uplift the total number of concurrent SVCs from 2100 to around 4000. Can anyone supply any information regarding the maximum number of concurrent SVCs a 7204VXR can support, or point me in the direction of some information regarding sizing to accommodate.

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Re: What is the maximum number of x25 SVCs supported on a Cisco

X.25 encapsulation is a CPU intensive task as it involves sequence checking, flow control, fragmentation. The maximum performance bringing the CPU to 100% utilization can be approximated to 40% of the maximum figures advertised for the process-switching of IP packets. XOT should incur slightly higher CPU load as the TCP encapsulation is intensive as well.

Main system memory usage is unlikely to be an issue. With a gross estimate of 1kB per virtual circuit, there are few hardware configurations where the memory usage for x.25 contexts is a big issue. Shared I/O memory on the low end, or system buffers on the high-end may be an issue when the x.25 interface has either to buffer traffic outgoing to X.25 or reassemble incoming X.25 traffic. This impacts memory usage on the high-end and Shared Memory Usage on the low end. Do not be shy with Shared Memory Options, considering that eventual dynamic Protocols would use buffers as well.

The short answer though is to check your current resources used, and then do the math.

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