Skype ate my PC

Went into the office and found the PC chomping away at something,
Netmeter showed 6 kbytes/s traffic both up and down.

IPtools showed 14 screens of TCP connections to skype.exe processes,
at least 400 active connections to a huge range of external IPs.

Router firewall reported 2000 active streams (its limit) rebooted it
with a new limit of 2500 and they were quickly filled up too.

Email and web browsing very unreliable, lots of timeouts.

Looked like dear old 192.168.0.35 had become part of Skype's
infrastructure again. Couldn't even make a Skype call as it couldn't
find a proxy ! bit off when it overloads the system to the point where
it can't work itself.

Such is life, Skype get paid millions by Ebay and I get to provide an
infinitesimal part of their infrastructure

Phil

 

Skpe uses your PC as a supernode. Search Skype's website for supernode.

 

Philip old boy, wasn't it you a week or so ago that described Skype
as

 

you have to test these things out to understand how they work and
their impact, then figure out how to solve any problems that arise.
Otherwise when asked for advice I wouldn't have a clue.


Phil

 

Good answer.
I have a spare expendable system for experiments like that.
Its amazing what Win98 will pick up if left in the DMZ for
an hour or two.

 

The Skype Network Administrators guide claims that you shouldn't
notice any decrease in performance when being used as a supernode.
Clearly their claim just isn't true.

"In addition, given the strict bandwidth limit placed on supernodes
and relay hosts, Skype end users cannot tell the difference beween a
given computer being used as a regular Skype node, supernode, or relay
host because the capabilities required to support the additional
functionality are transparent and have no noticable impact on a given
computer's performance."

See http://www.skype.com/security/guide-for-network-admins-30beta.pdf
for full details.

 

I run Skype 24x7 and have done so for the last two years.

I have never suffered any such problems so can only assume it must be your
local configuration

 

There seems to be a problem with the configuration of your newsreader,
it's top posting..!

Ivor

 

Wanker

 

Ah, the old "I know I'm wrong so I'll swear" defence.

It doesn't work.

<plonk>

Ivor

 

Wanker Squared

 

If you can point me to the relevant configuration option in Skype I
would be grateful. Something like "opt out of having 2500 unsolicited
connections" perhaps.

Phil

 

Don't run it as a service.
Put your machine in standby when not in use.
Use NAT.

 

how ? I don't recall Skype presenting me with that option, where's the
setting on the client ?

it's always in use remotely.

it is NATted, that's a myth.

Phil

 

Recently, Phil Thompson popped out over the fence
around uk.telecom.voip and said...
|
|>Don't run it as a service.
|
|how ? I don't recall Skype presenting me with that option, where's the
|setting on the client ?
|
Don't run it... full stop.

Or, should be installed to be fired up on request, not starting when the
PC is started. Probably is the "Install for just me" and "Install for
every user" option.

If you tell me how does it start, maybe I can help you.

Another option is to set up a proper QOS management, and choking the
service inside your network for the packets marked with the Skype tag.

NATting doesn't do, it's the client that advertises itself to the Skype
network as a Supernode when it detects a (large) broadband connection.
You are not "discovered" from outside, it's the client that does the
trick: it gets your public IP and port and broadcasts it to the world.
What annoys me is that this is done without the user knowledge or
consent on bog standard installations. This is a blatant breach of the
Computer Misuse Act, but nobody seems to care about it...

Whatever.

 

it's a test bed to see how Skype behaves in a practical installation.

the "on request" bit wouldn't work for incoming calls, presence
indication etc.

I'll look and see, also see who is the owner of the process.

My primary interest is to understand how a default Skype installation
behaves and what the consequences might be.

Phil

 

According to Skype itself: "a Skype client that is unable to
receive inbound network connections (such as a user behind a
NAT or firewall) will never become eligible to become a
supernode nor will it ever be asked to relay a third party’s
traffic"

Are you saying this is wrong?

 

yes.

Unless there is some other modus operandi not covered by the above
that involves data flow to and from the PC and 2500 simultaneous
connections.

At http://yarwell.blogspot.com/ you can see the IP address and ports
of the machine concerned. I am not port forwarding 1174 to that PC as
the above quote would suggest was necessary.

Phil

 

Were those connections all outbound, then? If not, it's a
puzzle how inbound connections could be established without
router port forwarding or a public IP address forwarding to
that PC. Maybe someone in the Skype user forums could
explain it.

Did you say the PC was providing remote access? Does this
provide a route through the firewall?

 

its trivial really, the Skype client behind the firewall can solicit
the inbound connections. They aren't "cold calling" connections they
are part of a P2P network with a client on my network.

The Skype client could send a packet out saying reply to this on port
xyz and the firewall would accept that as a reply associated with the
outbound request.

Type "netstat" at a windows command line and you'll see lots of
inbound connections that are responses to things like web browsers.

obviously, but not for Skype ports. Its running SNMP and a web server.

Phil