sara fink wrote:
Someone knows if skype calls placed between 2 people in Israel, passes
via skype server in europe?
The short answer is not necessarily.
1. Skype calls do not go through a central server. A central server is
used to keep track of people's status etc.
2. If both ends of the call can make direct connections to each other
without going through NAT (i.e. if incoming connections can be made on a
particular port which I believe is picked at install time), the call is
made directly between both parties without being routed through any other
hosts.
3. If it is not possible to make a direct connection between both parties,
a third host is used to relay traffic back and forth.
Note that I'm not an expert on Skype and my understanding is mainly based
on my recollections of the contents of
http://www1.cs.columbia.edu/~salman/publications/skype1_4.pdf which is
admittedly a bit old now and which I read something like a year ago. You
can find a whole lot more of this kind of thing, some of it newer, at
http://www1.cs.columbia.edu/~salman/skype/
Is there a standard for voip? What I mean is if there are limits, for
download, upload, quality of service that produces a reliable
conversation?
Most of the time when people use the term "voip" nowadays, they are
refering to telephone-quality speech, generally using SIP, IAX2 or H323 at
8kHz sampling. An uncompressed call using ULAW or ALAW encoding (which is
what is used natively on US and European phone systems respectively) will
need 64kbps for the audio plus overhead for the protocol. Codecs like
Speex (open) and G729 (patented) however attempt to carry such signals at
only 8kbps, and largely succeed. I've run G729 calls over a dialup
connection, though I don't recommend it.
QOS is important. I don't know much about it myself, but I do know that
if you have the right QOS settings, you can happily do other stuff on your
connection and your voip trafic will get through quite nicely. If not,
even moderate network activity can be enough to scramble it.
Wish I could be of more help.
Geoff.
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