Latency and CDR CCM 4.1.3

henry.benjamin · ‎09-12-2007

Hi Folks , has anyone ever seen where phones don?t report any latency in the CDR records even though you know there is, is there a service parameter that may have been changed?? I know this is standard, and the phone picks up the NTP timestamp from the RTP packets and calculates it from there. LAN calls appear to have 0 latency but not sure about WAN calls , any ideas thanks

Henry

bwilmoth · ‎09-18-2007

latency value is an estimate of the network latency, expressed in milliseconds. This is the average value of the difference between the Network Time Protocol (NTP) timestamp indicated by the senders of the RTCP messages and the NTP timestamp of the receivers, measured when these messages are received. The average is obtained by summing all the estimates, then dividing by the number of RTCP messages that have been received.Jitter and latency are only measures for incoming packets trough a WAN, to the endpoint, because generally on a LAN there is enough bandwidth not to worry about quality.The incoming packets are the ones generated by Call Management Record (CMR) records. In order to determine QoS, three factors are used. They are lost packets, jitter, and latency. This latency has no default values, so in the test environment, the value of 0 could be true depending on how packets are buffered and by what device.

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a00803f526c.html#wp1032132