public vs private data network

Private vs Public refers to the IP addressing scheme. You can use either globally routed IP's (public) or private IP's 10.0.0.0 - 10.255.255.255 (10/8 prefix) 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) 192.168.0.0 - 192.168.255.255 (192.168/16 prefix). See RFC 1918 for more details.

I might have been misinterpreted in my question. I was asking public and private data networks in terms of wide area implementation of connecting geographically separated locations using telcos and not in terms of ip addressing scheme.

In article , jonnah wrote: :what is the difference between public and a private data network? am I :correct in assuming that if you use a *public* data network to connect :your remote offices with your branch offices, you either use the :Internet as the Public DN or frame relay (as the Public DN of a telco) :but if you use leased lines or pt to pt links, then is it considered :as a *private* data network? (since you're not sharing the links with :others) if anybody knows, please enlighten me

Pretty much. If a random person around the world can get packets to your security gate then you are on a public data network. If only a closed list of places can get to your security gate, and you can't get out either then you are on a private data network.

In between would be semi-private networks that have clouds of accessible devices and security gateways to public networks. For example, a research network might allow public email in and might allow insiders a wide variety of outward accesses, but the basic security controls might be far away from most of the member systems.

To really be considered a private network in the traditional PSTN sense, there can't be -any- cross-border traffic possible through the network facilities.

No, your question was clear, and your own explanation was close on -- Walter's (elsewhere) this thread might have amplified on it a bit, but notice that as he introduced "semi-private" (or was it "semi-public" ) that these concept are somewhat dependent on context and point of view.