Inbound audio choppy

Posts: 148 · Vonage Forum Senior Joined: Feb 28, 2005 Posts: 148

reebok wrote:

ok, I actually didn't read your post before my first reply, because let's face it, it was long. so now that I have read, it sounds like your problem is jitter (which also shows up on testyourvoip), especially noting the wireless connection, and especially the signal strength. this is the best explanation of jitter I found:
http://www.dslreports.com/forum/remark,8353924
jitter is a variance in delay. So at one moment you may have 10ms of end to end delay and then it may jump up to 100ms back down to 30ms, etc. All of this causes the voice packets to arrive erratically; in spurts.

if this isn't good enough/easy enough to understand, I'll come up with my own interpretation, but it probably won't be until tomorrow or the next day.

OK, I think you are on the right track with jitter. I noticed when doing my ping to the local POP that the return times were all over the place. I also went here:

http://www.voip-info.org/wiki-QoS

where it states:

Quote:

Jitter
Jitter can be measured in several ways. There are jitter measurement calculations defined in:

IETF RFC 3550 RTP: A Transport Protocol for Real-Time Applications
IETF RFC 3611 RTP Control Protocol Extended Reports (RTCP XR)
But, equipment and network vendors often don't detail exactly how they are calculating the values they report for measured jitter. Most Voip endpoint devices (e.g. Voip phones and ATAs) have jitter buffers to compensate for network jitter. Quoting from Cisco:

Jitter buffers (used to compensate for varying delay) further add to the end-to-end delay, and are usually only effective on delay variations less than 100 ms. Jitter must therefore be minimized.

Whats an acceptable level of jitter in a network? Several network providers now speciify maximum jitter in their SLA?s.

Quest SLA 2ms maximum jitter - Measured Actual for Oct 2004: 0.10ms
Viterla SLA 1ms maximum jitter
Axiowave SLA 0.5ms maximum jitter
Verio SLA 0.5ms average, not to exceed 10ms maximum jitter more than 0.1% of time
Internap SLA 0.5ms maximum jitter

The SLA numbers above are for backbone providers, the total jitter for a Voip call may also include additional jitter in the Voip provider's and the user's local ISP networks.

My vairations in packet return times are way beyond 2ms, the easiest spec here. Which one of these does Vonage use?

That site also states:

Quote:

Packet Loss
Voip is not tolerant of packet loss. Even 1% packet loss can "significantly degrade" a Voip call using a G.711? codec and other more compressing codecs can tolerate even less packet loss. (Intel whitepaper)
Cisco says:

The default G.729 codec requires packet loss far less than 1 percent to avoid audible errors. Ideally, there should be no packet loss for Voip (Cisco Whitepaper)

Most network SLA?s specify maxium packet loss

Quest SLA 0.5% maximum packet loss - Measured Actual for Oct 2004: 0.03%
Axiowave SLA 0% maximum packet loss
Verio SLA 0.1% maximum packet loss
Internap SLA 0.3% maximum packet loss

The SLA numbers above are for backbone providers, the total packet loss for a Voip call may also include additional packet loss in the Voip provider's and the user's local ISP networks.

With the combination of my dropped packets and jitter, it's no wonder I'm having problems. Looks like I need to get my ISP to fix it or switch to another broadband method.

Posts: 24 · Vonage Forum Associate Joined: Jan 27, 2005 Posts: 24

jMon54 wrote:

The techie at the ISP assures me Vonage should work fine with their system, they have it in their offices.

LOL! I'm guessing they're not getting their internet over wireless at their office so they have a much better chance of it working.

Posts: 148 · Vonage Forum Senior Joined: Feb 28, 2005 Posts: 148

Noticed that very early in the morning (1AM), I get a very good signal to the tower (hardly any packet drops), and the phone works near perfect. During the day is the problem. I would think this points to either a traffic congestion problem with the ISP or Vonage.

Posts: 36 · Vonage Forum Junior Joined: Feb 24, 2005 Posts: 36

Widescreen wrote:

Wireless ISP's have huge latency problems. I'll bet that's the problem and unfortunately there's probably nothing you can do to fix it.

I have wireless ISP. My average latency is in the 40s, Vonage says anything lower than 200 gets you good quality. I do have some packet loss, though not more than 1% on average. Unfortunately, even though I have 1mb up & down, even with no computers on I still experience choppy audio.