Skype and supernodes

Blaster99

I did a bit of research into the bandwidth that Skype may use as part of its P2P setup last night and some crowd has done research that seemed to prove that if any of the participants in a call sit behind a firewall and NAT, then the call traffic needs be routed through a supernode. A supernode is a machine on a public IP with open ports presumably. Skype seems to claim that a supernode only ever needs to contribute about 5KB/s worth of bandwidth.

I was a on a Skype call earlier with somebody in Ireland and I did a "netstat -a" during the call to see if I had any connections to anyone in Ireland. I did not. Both of us are behind firewalls and NAT. It seems that voice traffic went through a 3rd party somewhere. Pretty nasty for that 3rd party if that's the case.

Rew

They put in a few of their own supernodes AFAIK. Most people are NAT'd these days as well making the whole thing more complex. You get better call quality if you expose the port externally.

causal

According to Skype

How much bandwidth does Skype use when there are no active calls?

On average Skype uses 0-0.5 kilobytes/sec while idle. This is used mainly for contact presence updates. The exact bandwidth depends on many factors.

But according to this Skype user

I'm not real happy with Skype, as I've seen it saturate my uplink without me having done anyting at all on Skype, which means that my computer was turned into a proxy/super node/whatever they want to call it. Without being able to opt out, nor being able to throttle it any way, I no longer run it. If it had not been causing issues on my end, I probably wouldn't have even caught it doing that. But when it's chewing up bandwidth from my machine, let alone the other machines on the network, that's when I do have a problem. I've seen the same thing with other P2P programs, but I've also seen the same thing with other non-P2P programs as well.

When I ran skype (in the dark old days before Gizmo) I set my software firewall not to allow skype act as a server.

causal

Blaster99

Surely your firewall by default blocks all incoming ports? This prevents Skype from being a server and also prevents it from being able to do P2P telephony without going through supernodes.

So what does Gizmo do better? It seems it has a following because it's open source, which is neither here nor there.

causal

Blaster99 wrote:

Surely your firewall by default blocks all incoming ports? This prevents Skype from being a server and also prevents it from being able to do P2P telephony without going through supernodes.

I think all (bar 515 for some obscure reason) - but that doesn't stop ZoneAlarm asking me if I want to let all sorts of software act as a server - and I deny access. Maybe the hard firewall would do the trick but there's no harm having ZoneAlarm setup to refuse incoming server requests.

So what does Gizmo do better?

In one word: SIP In another word interoperability.
Open source and significantly open standard.
In practical terms: You can phone my blueface number (or anyones VoIP number) for free using Gizmo - you can't do that with Skype because it uses it's own unique proprietary standard. I've said many times on this forum that, imho, if Skype doens't adopt open standards (SIP really) then it will have a short lifetime.

Gizmo on Gizmo

Founding Principles

At the core of Gizmo Project is a commitment to open standards, which is critical to deliver the true potential of VoIP. SIPphone believes that like web pages, email and IM, calls should be free. And we believe the more people you can call the better. Which is why we use the industry VoIP standard, SIP.

causal