Buffer underruns normal?

[fizikz]

Here are the RTP stats for 2 days worth of uptime:

PacketsSent   31607      
PacketsReceived   31517
BytesSent           5413160
BytesReceived   5420924
PacketsLost           21
Overruns           0
Underruns          14820

Is this number of underruns normal? Why does this happen?

I have not noticed any audio problems, so I could ignore it, but I am curious.

[fizikz]

Does no one else get buffer underruns?

Now with about 14 days of uptime, SP Service Stats shows:

PacketsSent         1021564 
PacketsReceived   1018084
BytesSent            175626796
BytesReceived      175099528
PacketsLost          420
Overruns             0
Underruns           94776


What kind of stats do others have? The seemingly large number of underruns catches my eye each time. As for the packet loss, considering it's much less than 1% loss, I suspect it's fine.