High Ping times to/from 7920

dmavdn-tsg · ‎05-16-2007

I have noticed very high ping round trip times to the 7920 phones at six different sites. The voice is fine with no breakups. Is this a non-issue or something to worry about? I can't find any documentation from Cisco on this. Thanks.

migilles · ‎05-16-2007

The 7920 will enter sleep every other 2 seconds when not on call, so can be up to that period in delay in answering a ping.

If on call, should see the ping response very fast.

Of course will want to ensure proxy arp is enabled on the ap as well.

tkhan · ‎05-22-2007

I am noticing the same thing on 7921g phones connected to WLC 4402 running 4.1.171.0. The voice conversation itself does not suffer which makes me not trust a "ping" in this scenario. It would be helpful for Cisco to clear up what these high pings times are actually reflecting.

...Ty

migilles · ‎05-22-2007

With 7921, it will use PS-POLL when in idle, so could take up to 100ms (beacon period) before rx the packet.

Yes ping is not a reliable test.

If you want to use ping, then ensure the phone is on call, where it will then use U-APSD or PS-POLL depending on WMM status.

mheusinger · ‎05-23-2007

Hi,

ICMP should not be a protocol prioritized like voip packets. Thus also the AP or intermediate equipment like switches could add to the ping delay in transmitting other packets first. On the AP it also depends on the QoS settings for best effort traffic (above or below background). So even if a phone is on call, ping does not give precise values, unless you use an extended ping and set the TOS value to 184 (ef). If you do so on the other hand, you could interfere with your voip packets and degrade voice quality in the worst case.

Regards, Martin