Seems I have to explain why IP packet routing is not broadcasting some more. Those of you who understand that postcards have one trajectory from you to me can skip this.
My first post was a first-order Choate fix. This post is a second-order fix. I refuse to respond to the next gripe, where JC brings up quantum postcards that take all paths at the same time, until you open your mailbox. At 07:12 AM 12/17/02 -0600, Jim Choate wrote: >On Mon, 16 Dec 2002, Major Variola (ret) wrote: >> "The network?" Sorry, its one wire from here to there. > >No it isn't, try a traceroute to a regular site that isn't over your >internal network over several days, why does it change? In a *virtual* connection, the *physical* paths may change transparently. That's what *virtual* means. Each IP packet has one path though the sequence of packets may take different routes. Perhaps the mailing-postcards analogy is better than the telco one, since Ma Bell doesn't diddle the route after call setup AFAIK. But your postcards, once injected into the Postal Network, may take different routes. Not that you or your recipient knows. >> In particular, most protocols (e.g., TCP) set up a virtual, > >Wrong layer, think of httpd, ftp, telnet, etc. I was hoping not to have to elaborate, but basically a UDP based protocol is going to set up some kind of session "state". Often duplicating what TCP does. These are TCP based, although FTP uses UDP for data but TCP for control. Httpd is a daemon not a protocol or app BTW. >Nobody (but perhaps you by inference) is claiming it is identical, >however, it -is- a broadcast (just consider how a packet gets routed, >consider the TTL for example or how a ping works). Each packet you send >out goes to many places -besides- the shortest route to the target host >(which is how the shortest route is found). Modulo CALEA and multi-/broadcast packets, each postcard is handed off to exactly one other device, or dropped. At 10:46 AM 12/17/02 -0000, David Howe wrote: >there are plenty of setups (broadcast domains, egmp etc) where a single >packet is echoed out of multiple interfaces, and in fact some >amplification attacks rely on that. Yes. A service which xeroxes your postcard and resends to everyone in the neighborhood (or a phone conference call) might be construed as broadcasting to a limited audience. But it doesn't scale to WANs. And is now how the Aussies read Dow Jones or how DJ libels Aussies :-)
