Aswath Rao comments in his blog about some recent analysis of Skype's super nodes. Most interesting is the observation that being behind a NAT router with a private IP address doesn't necessarily keep one from becoming a Supernode.
Both Columbia University's analysis of Skype (http://www1.cs.columbia.edu/~library/TR-repository/reports/reports-2004/cucs-039-04.pdf), though the Skype Network Administrator's Guide at http://www.skype.com/security/guide-for-network-admins.pdf notes that only machines that are "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).
Aswath notes that those behind a "well behaved NAT" could become Skype supernodes, since they could be open to receiving an unsolicited session request.
This is important stuff for enterprise network managers to be aware of as they determine the proper Skype policy for their organization.
Comments