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Posted Aug 23, 2007 5:13 UTC (Thu) by eru (subscriber, #2753)
Parent article: The Skype outage

From what I gathered from the article, Skype seems to have a central system for authentication. I think the problem is right there. This does not scale. Compare this with cellular phone systems, where the responsibility for authentication of a handset is distributed between the various operators. Each will of course have somewhere a database of their own subscribers, but no global database of all cellular users is needed.

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Posted Aug 23, 2007 10:01 UTC (Thu) by lacostej (guest, #2760) [Link]

> but no global database of all cellular users is needed.

Same for VoIP. Skype has their own database, OpenWengo has theirs, ekiga has theirs, etc...

A better comparison might be with DNS which is also a directory. DNS is distributed and has several root servers. But information takes time to be updated, something that a phone network wouldn't want.

I am not sure how Skype servers are networked, there are probably several of them and some redundancy. But as always, the performance peak supported by one infrastructure is often a percentage above the maximum peak experienced in the network. If they need to support 1000 logins per second, maybe their network can today support 5 or 10 000, which is usually sufficient, except when 90% of their clients restart within 48h...

They've made a mistake and they will probably learn from it.

But on the other side, I'd rather have skype disappear and get everyone on an open standard technology. Be it SIP or anything else that stands the time.


Posted Aug 29, 2007 22:25 UTC (Wed) by job (guest, #670) [Link]

> Same for VoIP. Skype has their own database, OpenWengo has theirs, ekiga has theirs

That's just wrong. My email relies on solely on my own server and not on somebody else's database. My VoIP as well. If you would call me using the standard protocol, SIP, no other server than my own would be involved (don't actually do this, it's probably night over here and I'll be cranky).

There is absolutely zero reason to use this proprietary crap, and to rely on a third party which whom you probably don't even have a valid service contract.


Posted Aug 30, 2007 4:27 UTC (Thu) by lacostej (guest, #2760) [Link]

> If you would call me using the standard protocol, SIP, no other server
> than my own would be involved

That's because you're running your own dynamic/static DNS, right ?
Or because you give your IP to someone before they call you ?

The problem is still there for most people.

Your email address doesn't change when you move. The email is dropped to a mail box and you as a user go and fetch it from there.

For a phone call, the phone call has to reach you, so you have to register your current location first.

I don't see how one can change that without impacting a lot the network, appart from generalizing dynamic DNS maybe.

Am I missing something ?


Posted Aug 31, 2007 4:05 UTC (Fri) by rqosa (subscriber, #24136) [Link]

> Am I missing something ?

What you're missing is that a SIP client can potentially be used with any SIP registrar, and can make calls to users on other registrars. Thus, SIP, is decentralized, like email, and unlike Skype.


Posted Aug 31, 2007 5:27 UTC (Fri) by lacostej (guest, #2760) [Link]

I still don't get your point. Thanks for being patient !!

I mean I think I understand your point but I feel that we're both right. Yes you can use other registars, but when your registar is down, you lose part of your service.

SIP still need you to log in to a registar server.

It is inter operable but within one service provider, you still have to register. As I initially said one must do it with ekiga and openwengo (2 different SIP providers).

So now you tell me, if this service is dead, you can register somewhere else. Yes, but how usable that is ? E.g. I have a Sipura SIP phone at home.
If the registar service (telio) dies,
1- I have to use a browser to change the config and point to a different SIP server (e.g. to ekiga registar)
2- if I change SIP server, I will still be able to call other parties, but
* I may need to pay some new fees that my current SIP service will already have covered in my agreement
* furthermore, people won't be able to call me to my land phone number (because my SIP provider provides me a bridge land phone-SIP).
* people won't be able to call me on my usual SIP address

So yes I can call, but I loose some features.

It looks to me to be the same as with Skype.

So I wonder again. Am I missing something ?


Posted Aug 31, 2007 16:44 UTC (Fri) by njs (guest, #40338) [Link]

The important thing about email and SIP isn't that you can change providers on the drop of a hat -- indeed, in both cases, you're generally at the mercy of your provider's technical acumen when it comes to scaling, uptime, etc.

The important thing about email and SIP is that there are lots and lots of providers, and they interoperate. So if your current provider sucks consistently, you can get fed up and switch to one that works better; because there are lots and lots of providers competing, there almost certainly *is* one that works better, and because they interoperate, you can switch even if your friends don't. (You can even run your own registrar and switch to that.) With Skype, everyone's pretty much stuck, and at the mercy of the one company. They might do pretty well as companies go (for now), but it's unlikely they'll do as well as any company that managed to climb to the top over heavy competition -- why should they bother, they're making money now.

(See also Jabber vs. proprietary IM protocols, and any article on vendor lock-in...)


Posted Aug 31, 2007 17:21 UTC (Fri) by lacostej (guest, #2760) [Link]

This I already know. You don't need to convince me on the benefits of using :) I don't use much Skype, I have a SIP enabled phone at home. I just hope that an openmoko-like phone can fulfill my needs of an open phone.

But the initial discussion on this thread was:

> but no global database of all cellular users is needed.

to which I responded that the problem was the same today with SIP.

Can we agree on the 2 following sentences:

* the fact that Skype is a lock-in solution and doesn't interop with other VoIP solutions

* SIP also requires some sort of "global database" for each particular service provider, thus forcing you to login to a registrar to make use of *your* SIP id, meaning that if you registrar is down, you cannot be reached (but can make calls by reconfiguring your phone to use a different service provider)


Posted Aug 31, 2007 19:47 UTC (Fri) by njs (guest, #40338) [Link]

Fair enough -- I admit I was picking the parts of the argument that made sense to me and responding to those, myself :-)

The initial post in this thread was not one that made any sense to me. Scalability is completely a red herring here; scalability is merely a technical concern. Do we have the hardware and knowledge to build a database that can scale to millions of subscribers? Yes, obviously, we do it right now. (AT&T might be only one of many cell phone providers, but I bet they're still routing more calls per second than Skype on its best day.) There are reasons that we have more than one cellular operator, but scalability is just not one of them.

Then the discussion went off in a different direction that I also don't understand. What is a global database for each particular service provider? I mean, if there are multiple service providers, your database is either global, or particular to one of them, it can't be both at once... For Skype, there effectively is only one service provider, so it makes sense to talk about their database being global, but for SIP there are hundreds, and you can run your own if you want (just like you can run your own email server). Like you say, SIP is a little more complicated than email because a call request needs to be deliverable in real-time, but this is just a technical detail.

I sort of get the impression that other posters were similarly confused about this part, and also guessed at what you were trying to say and then replied based on those guesses.


Posted Sep 1, 2007 5:45 UTC (Sat) by rqosa (subscriber, #24136) [Link]

My point was that, with SIP, it's unlikely that there would ever be an outage for all SIP users; the failure of one registrar doesn't cause an outage for users on others. I think that was what the original poster meant (except that post referred to cellular phone systems, rather than SIP).

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