Apart from routers (if you have one) and where they are located, where the DVG ATA plugs in, what ISP you are using, or the QoS test on Primus' website, there is an important point to understand:
What is the Latency, Jitter, & Packet Loss between your DVG ATA and Primus' TBB servers ? And for a VOIP call, to the last network hop?
1) If Latency is large, it may not affect your file downloads; but it will very likely affect VOIP in terms of a perceived "delay" or LAG.
You need to consider the Latency not just from the DVG ATA to the TBB Server, but also through the network to the last hop before connecting to a VOIP or PSTN phone. So a High Latency in a TBB server ping may provide some clues to such a LAG problem, but not always.
The max acceptable round trip delay for conversations is about 350ms... beyond which we humans become irritated with the LAG and interruptions.....
2) Network Latency is variable depending on the time of day; ie the ISP network and Primus' network (the Internet for that matter) are not static; things are always happenning. This can be more prevalent on cablemodem due to shared lines/network, but this can also occur on DSL because "the network" is always shared at some point.
Furthermore, at a given time, the Latency should be fairly consistent, with a slight variance (JITTER) around the average. This means packets including VOIP packets are being routed somewhat the same through the network.. you are probably getting good QOS.
However if the Latency varies considerably (Large JITTER) at a given time (within a few minutes..), then this can mean that packets are being held up somewhere in the network due to congestion or network topology (load-balancing, packets take different routes, etc). These will most certainly cause VOIP choppiness.
See these and other links for more info:
voip-info: »www.voip-info.org/wiki-QoS
quality issues: »www.freeway.com/voipqualityissues.htm
The results of "ping" and "traceroute" MAY help to determine where a problem may lie. However, CAUTION, other factors need to be taken into account before pointing a finger at any particular node (server, router).
NOTE: Try and isolate the problem even further by testing your ATA on another BroadBand connection.
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by canoe 
last modified: 2006-04-17 19:54:21 |
