NFV Tunnel Performance

The NFV tunnel uses TCP transport and can handle both delay and a certain amount of packet loss without losing the PM function.

Note: Buffering is limited; there are limits for the tunnel performance. Overall capacity is reduced with higher delay and packet loss.

This table shows the expected maximum aggregated PM bandwidth at different scenarios:

The limiting factor to consider is the total amount of bandwidth that the tunnel can carry; this can then be used to calculate how many PM sessions of a certain type would be safe to use for a specific situation.

If the Module is placed “close” to the Sensor Control, that is, in the same rack or datacenter, the delay between the Sensor Control and the Module will be negligible and it would be possible to use up to the max capacity of 2,000 simultaneous TWAMP sessions at 20PPS per Module (total of 4,000 per Sensor Control if using two Modules).

Note: 100ms is a very long distance (e.g., Amsterdam <-> Washington), and typically, this type of link is not suitable for NFV-type functions. For example, placing a VNF Firewall in the US to support a service in the Netherlands may not be ideal.

Example:

If the Module is deployed 50ms away from the Sensor Control (100ms roundtrip), then the expected maximum PM bandwidth using this Module as an NFV sender will be 12.5Mbps. If occasional packet loss is expected, the expected value drops to 4Mbps. This is because the tunnel will have to start buffering and retransmit the lost packets.

Testing for Capacity

To test for capacity between the Sensor Control and the Module during deployment and provisioning, verify that:

1. Test methodology can either be TWAMP generated from the Sensor Control (controlled from Skylight orchestrator) or a layer-3 SAT test from a Module close to the Sensor Control, towards the Module to be tested.

2. To test for 12.5Mbps, set up a test transmitting 1,030 packets per second with packet size 1500B (Ethernet payload size).
   You can use this table for reference:

Validating Test Results

To validate the test results, check if:

1. The test shows lower throughput than the desired bandwidth (ideally measured over 24hrs on a weekday).

2. Occurrences of packet loss above 0.01% are present.

3. RTT varies more than 10% over time (50ms and up).

If none of the above is true, then this path is sufficient to carry the NFV tunnel.

The following table can be used to quickly assess how many expected PM sessions (TWAMP) correspond to a specific NFV tunnel bandwidth.

Using the 100ms/12.5Mbps scenario as an example, it would amount to 625 concurrent TWAMP sessions through the NFV tunnel using the default 82Byte IP payload size (=128Byte Ethernet on the wire).

The calculation is linear, so 50ms RTT = 100ms RTT.