Really, the apropriate place for content filtering is at the application layer. It *could* be done at the transport layer, but that's really not the place for it.
Clearly the IETF believed that the network layer was an appropriate place for general classification when they developed IPv4. I haven't verified it, but I suspect that IPv6 has (or will have) an appropriate mechanism for indicating security classification. The identical mechanism may be used for packet labelling, with the broad
Security classification and "decent/indecent" ratings are rather different, IMHO. With security, the author of the data has to decide the best rating for his/her own security. With decent/indecent filtering, the author has to decide what is best for _other_people_. I suppose it's not as bad as that with the third-party ratings in PICS, but there will still be inconsistancies. The main reason I think decent/indecent filtering should be done at the application level is, if they create a ratings system and later decide that they've screwed up and another system would be better (which is quite possible, if you understand the previous paragraph), all that's really required is re-writing the application software. OTOH, if they did it at the transport layer and later decided to switch to something else, they would have to change the protocol, which is very difficult. And, depending on the changes, they may have to re-write the apps again anyways. Also, at the application layer, ANYONE could create their own ratings system, and the market could decide which is best. (The downside of that is that there would be nonstandardized chaos for a while). Just My Humble Opinion. ===================================================================== | Steve Reid - SysAdmin & Pres, EDM Web (http://www.edmweb.com/) | | Email: steve@edmweb.com Home Page: http://www.edmweb.com/steve/ | | PGP Fingerprint: 11 C8 9D 1C D6 72 87 E6 8C 09 EC 52 44 3F 88 30 | | -- Disclaimer: JMHO, YMMV, IANAL. -- | ===================================================================:)