6.4.a Implement and troubleshoot IP SLA

  • 6.4.a [i] ICMP, UDP, Jitter, VoIP

The IP SLAs ICMP jitter operation supports the following statistical measurements:

● Jitter (source-to-destination and destination-to-source)

● Latency (source-to-destination and destination-to-source)

● Round-trip time latency

● Packet loss

● Successive packet loss

● Out-of-sequence packets (source-to-destination, destination-to-source, and round-trip)

● Late packets

IP SLAs ICMP jitter uses a two ICMP timestamp messages, an ICMP Timestamp Request (Type 13) and an ICMP Timestamp Reply (Type 14), to provide jitter, packet loss, and latency. IP SLAs ICMP jitter operations differ from IP SLAs ICMP echo operations in that ICMP echo uses ICMP Echo request and reply (ping). Devices that are fully compliant with ICMP must be able to respond to the time stamp messages without requiring an IP SLA responder at the destination.

The IP Service Level Agreements (SLAs) UDP jitter operation diagnoses network suitability for real-time traffic applications such as VoIP, video over IP, or real-time conferencing.

However, the IP SLAs UDP jitter operation does more than just monitor jitter. As the UDP jitter operation includes data returned by the IP SLAs UDP operation, the UDP jitter operation can be used as a multipurpose data gathering operation . The packets that IP SLAs generate carry packet-sending and receiving sequence information, and sending and receiving time stamps from the source and the operational target. Based on this information, UDP jitter operations are capable of measuring the following:

● Per-direction jitter (source to destination and destination to source)

● Per-direction packet loss

● Per-direction delay (one-way delay)

● Round-trip delay (average round-trip time)

As paths for sending and receiving data may be different (asymmetric), the per-direction data allows you to more readily identify where congestion or other problems are occurring in the network. IP SLA responder, on a target device, is not required for any probes.

The UDP jitter operation functions by generating synthetic (simulated) UDP traffic. Asymmetric probes support custom-defined packet sizes per direction with which different packet sizes can be sent in request packets (from the source device to the destination device) and in response packets (from the destination device to the source device).

The IP SLAs operations function by generating synthetic (simulated) network traffic. A single IP SLAs operation (for example, IP SLAs operation 10) repeats at a given frequency for the lifetime of the operation. IP SLA requires schedule to be configured before it can be functional and out of default pending state.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 6092-6102).  . Kindle Edition.