Re: [Bloat] [Cerowrt-devel] FQ_Codel lwn draft article review

[Greg White <g.white@CableLabs.com>]

Jitter on its own is not useful for estimating VoIP quality.

For (c), I've used:

	
		
		
	
	
		
			
				
					Cole, Robert G., and Joshua H. Rosenbluth. "Voice over IP performance
monitoring." ACM SIGCOMM Computer Communication Review 31, no. 2 (2001):
9-24.

Which I generally simplify to:
	
		
		
	
	
		
			
				
					R= 94.2 - 0.024*Latency - 0.11*max(0,Latency-177.3 ms) - 30*log(1 +
15*Loss).

				
			
		
	
where Loss is mean packet loss rate (counting packets with latency >
(min_latency + 60ms) as lost), Latency is mean latency for packets not
counted as lost.


				
			
		
	
You can then translate R into an estimate of MOS using Eq.1 in the above
reference.

-Greg


On 11/27/12 5:51 PM, "Toke Høiland-Jørgensen" <toke@toke.dk> wrote:

>Oliver Hohlfeld
><oliver@net.t-labs.tu-berlin.de> writes:
>
>> The jitter measurements you have in mind will give you an idea on the
>> jitter specific to the chosen traffic scenario, nothing more --- and
>> in particular not the VoIP quality (although low vs. high jitter could
>> /indicate/ certain /possible/ quality degradations).
>
>Well no, in this sense the only "real" test for voip quality is picking
>up the (soft)phone and talking to someone. However, since the context
>here is automated measuring tools (preferably generating solid
>quantitative, comparable data), that is hardly feasible.
>
>I guess the goal of a comprehensive testing suite is to gather as many
>indicators of quality degradations (in the widest possible sense) as
>possible and testing for them under a variety of traffic conditions. I
>am by no means an expert on VoIP, but someone suggested measuring jitter
>could be useful, and I've proposed a possible way to do that (using
>iperf udp flows at a low-ish bandwidth).
>
>Since for the purpose of this particular discussion I seem to be in the
>test tool building business (at least for the time being), what I really
>need before going forward with this is someone to comment on (a) if
>using iperf udp flows is a valid way to measure jitter, (b) if measuring
>jitter is actually something someone wants to do and (c) if there are
>other tests that would be useful for testing VoIP (or general)
>conditions instead of / in addition to the jitter measurements.
>
>So far I don't have an answer to (a), only negative answers to (b) and
>nothing concrete for (c). So for the time being I'm shelving the idea,
>and will just note that it seems quite feasible to return to it should
>someone change their mind on (b) :)
>
>
>-Toke
>
>-- 
>Toke Høiland-Jørgensen
>toke@toke.dk