Does using an outbound sip proxy add latency?

[mcquaid]

Hello, I've been using vbuzzer for awhile now and my problem is this. On my end callers always seem to break up. However everyone says they hear me crystal clear. I have left several voice mails to my land line and verified this. No break ups whatsoever. So my issue is only one way.

As a test, I removed the sip outbound proxy from the voip client I use in linux and, even though I could no longer make call to landlines via vbuzzer, I called several test sip addresses and there was no breakups at all.

Now, initially, I thought a sip outbound proxy was for users who are behind firewalls. But it seems vbuzzer requires this. I am behind a firewall that has nat enabled, but I've never had to enable nat or use stun in any voip clients, I just put it the outbound proxy and it's just worked.

However I read on a voip site saying that using an outbound proxy adds latency. Somewhat surprised it would only be one way so I wanted to confirm a few things.

1) Do all voip providers use a sip outbound proxy?

2) Is this the actual source of my breakups or does this sound like a firewall issue. I never asked the individual running the linux server I'm behind to map any rtp ports or anything, all voip software has just worked without me enabling nat or stun in any voip client.

Vbuzzer's trial is about to end and wanted to sign up with a voip provider and was wanting more info about outbound proxy's and is this lag inherit to a provider using one or is this something resolvable on my end.

Also if this could be a firewall issue on my end, the individual who runs the linux server on my end knows nothing of voip. What would I have to ask him to map to get voip working properly if this is actually the case. I guess it involves iptables? But I'm not too sure of this. I'd rather avoid bugging him on this though if it's not actually the issue, so if anyone is knowledgable on outbound proxy's and their benefits/limitations that would be appreciated.

[PhoneBoy]

The vast majority of VoIP providers whose settings I am familiar with utilize an outbound proxy. Depending on where you are in relation to the outbound proxy, that may cause some issues.

[mcquaid]

After playing with my settings, I've determined that I don't actually need to use the sip outbound proxy. As long as I added :80 to vbuzzer.com to the registar, I was fine.

However, my issue remains the same, incoming audio, laggy, with breakups, outgoing perfect. Again this is only on landline calls. So I'm am thinking this is either a firewall issue on my end or with vbuzzers' service.

Because when I call sip addresses the calls are fine. It's only calling to landlines so in effect the calls with issues are my ip to vbuzzer and not just some ip to ip call on the net. It's the last mile that's causing issues. Still find it strange that outgoing audio is fine. I would think if I had a latency issue with vbuzzer that there would be breakups both ways. But I tested several voice mails to my landline with no breakups. And everyone says they hear me crystal clear. It's me who is always asking people to repeat themselves.

Any other suggestions on dealing with this would be greatly appreciated.