saa voip udp operation

[rabeder]

hi,

we have a 7206 router which does saa jitter operation measurement for about 50 access-location.

to one location we had a 2mb/s fr link and the mos value was 4,06.

we have this value from hp-ov which reads out the mib from the 7206.

today i upgraded the link to this location to 10mb/s (eth) - but the mos value did not change at all.

i know that 4,06 is ggod, but in my logical point of understanding i thought that if i have 5 times a quicker connection - it should be recognizable - although the jitter value which we also measure has decreased a lot

[mheusinger]

Hi,

MOS of ISDN (PCM) is 4.1 to my knowledge. so I would assume you can not get better than that!? I do not know however, how HP-OV does the calculation.

Regards, Martin

[rabeder]

hi,

thx f answer,

but what do u mean with isdn (PCM) - the connection i am talking is a ethernet to ethernet with a siemens voip equipment.

there is no isdn .

thx

[mheusinger]

Hi,

I mean, that the PCM (G.711) codec, which is normally used for Ethernet to Ethernet VoIP would not provide a MOS better than 4.1 (as far as I remember). PCM is also used with ISDN (64 kbps) telephony.

As you need to digitize an analog signal (voice) there needs to be a codec (coder - decoder). Depending on your codec of choice MOS values above 4 are not possible. And with PCM you get around 4.1 - so 4.06 should be close to the optimum. The underlying reason is, that digitizing usually involves degradation of voice quality. "Normal" telephones f.e. will cut off any frequencies outside 300 Hz - 3.4 kHz.

The question is, however, how HP-OV measures MOS and whether the two values are comparable. Between which values could those MOS values from HP-OV potentially be? Normally MOS is on a scale from 1 (unusable) to 5 (very good).

Regards, Martin