Nodes and Supernodes

There is a very nice picture and explanation about "nodes and supernodes" and why the Skype outage, found on the blog of Mike McGrath! Click on the picture below to go to the post ...
However, i think the picture is oversimplified: i thought ordinary hosts also could have direct links with each other, even when not in a call, therefore transferring a small part of the "sound/data" packages of other people.


Albyxx said...

Hi Jean,
I too thought the same as you. I have noticed that my PC is sometimes directly communicating to other PC's on my local network through skype.exe.
By the way, great blog; it's in my Google Reader!!

Jean Mercier said...

Great to see you on my blog! :-)

Anonymous said...

Hi Jean,

I'm Reese from www.phipe.com and I came across your blog while looking for some Skype related resources at http://www.skype-news.com/ Since I could not find your email id I took the liberty of getting in touch with you through this commenting system.

Phipe.com is an automatic dialer for Skype and could be a great resource for your visitors, whereas your blog with all the info you have here would also be a lovely resource for visitors of my site. It would be great if we can mention each other at our respective sites.

Please let me know if www.phipe.com could get a mention at your links section. I would like to mention your blog at http://www.phipe.com/resources.html

Reese Henderson

Anonymous said...

Wikipedia on Skype:

"The Skype user directory is entirely decentralized and distributed among the nodes in the network, which means the network can scale very easily to large sizes (currently about 220 million users)[5] without a complex and costly centralized infrastructure.

Skype also routes calls through other Skype peers on the network to ease the crossing of Symmetric NATs and firewalls. This, however, puts an extra burden on those who connect to the Internet without NAT, as their computers and network bandwidth may be used to route the calls of other users."

Jean Mercier said...

To Reese:
your site isn't a blog, but is promoting a product. Therefore, i will not link it, otherwise i will have to link 1000 other Skype related sites.
No offense!

To Anonymous on Wikipedia: thanks, interesting clarification!

Anonymous said...

It should be pointed out that only certain users are selected as supernodes. Skype doesn't reveal the actual number of supernodes, but it is believed to be about 25,000 out of all users logged in at the same time. According to a report from 2006 in Computerworld, under certain conditions, Skype is willing to accept thousands of connections, but (officially) stated to limit itself to 40 kb/s upload and download. (En earlier Skype Guide for network administrators for version 3.0 claims that supernodes carried only control traffic up to 5 kbytes/s.) Even though this practice is allowed in the Software license agreement, Skype has never revealed how much bandwidth is acutally being used in this manner.

The report: http://www.computerworld.co.nz/news.nsf/news/7AB67323D6305E49CC2570A1001698C0 (Computerworld)

Jean Mercier said...

Thanks for the link to Computerworld :-)