let's take this a little further, shall we? =) Down at the data level, and at email and WWW levels, your own Cafe model works here. Yup. In fact looking at your diagrams gave me flashbacks to my networking classes. 1) You connect to your ISP Out through your phone line, your computer is joining a table at a cafe. Sitting at this table are possibly hundreds of other people connected through their phone lines. Now, considering there is no way the cafe could ever have a table big enough for everyone at this table, there is a limit to the number of seats. So when you 'sit down,' you're sitting in a chair someone else might have had not ten minutes ago. --This is your dynamic IP address; your designated seat (IP) at this table (ISP) in this cafe (Internet). 2) How traffic gets out All of the tables in our cafe are connected via 'magic seats' (for lack of a better term, I should just call them routers --that's what they are). As you are talking at the table, everything you say (packet) has attached to it your table+seat number (IP address), and the table+seat number you want to talk to. Talking to a seat at your table is like placing the mustard on a lazy susan and spinning it. The correct seat will pick it up when it comes by. As it spins, you pick up anything that has your seat number on it. --Though you could 'see' what others at your table are passing around, you ignore it. (Someone who eavesdrops is called a packet sniffer). If the seat happens to be at another table, the 'magic seat' at your table passes your mustard along to the next. He also keeps an eye on the next table's lazy susan looking for anything that belongs at your table. Here is where classic routing algorithms come into play, as each table (ISP) can be connected to multiple other tables. The 'magic seats' (routers) maintain intelligent information to determine which table to send your sentence to. You say something, and it gets passed table-by-table to the right seat, where a reply is said and it comes back (more or less) the same way. Slow tables happen ;) Since your table+seat number is attached to everything you say, the other tables now how to find you. --Its like a return address on a piece of mail. Performing a 'ping' tests how fast the table+seat you want to talk to can get back to you; a 'traceroute' shows which tables are used and how fast they can pass things along. 3) Email & WWW Some seats at your table have specific duties. When you say "email my mom at table 23" to the email chair (server) at your table, it asks where 'table 23' is, and the email chair it needs to talk to. (This is through DNS, which has been mentioned already.) Then it tries to send your email to the email server at table 23. If he's swamped with other email, or your email server has a hard time finding out where table 23 is (did they move it out to the patio??), it holds on to your message and tries again multiple times over certain intervals (human configurable, a common setting is to retry for 48 hrs). When the email is delivered, the email server at table 23 holds onto it until your mom asks it if she has any new mail. More information is contained on the email envelope (email headers) than what is sent out above (packets). Your table+seat number for sure, but also information the email chairs use to talk amongst themselves, like "this came from Peter at table 1423," and "the email chair at table 56 was used to pass it along at 2:53pm." When you want to talk to a www chair (server), you ask for the table+seat number (IP address), and then send a kind request for information (I'll call this the URL, though technically a URL encompasses the IP address). While you are waiting, your request is being passed along to the www server at the far table. The www chair looks at your request, packages an answer, and sends it back. He's very curt, and has a bad case of amnesia. He has to be able to handle lots of requests from lots of seats, so he only replies back with what you asked for, ends the conversation, and instantly forgets he talked to you. You have to ask him again if you want more, but trust me, he's forgotten all about you and you have to ask very specifically and remind him who you are each time. Such is stateless communication. If he likes you, he'll want to remember you by sending you some cookies. Sending them back triggers his memory and he's not so forgetful anymore. What he wants to remember about you determines what kind of cookies you get. Not everybody likes cookies, though. ;) 4) You disconnect from your ISP Simple; you get up and leave the table (hang up the line). If there's anything left on the lazy susan for you, it eventually gets thrown away because its been there too long. hope this helps, i winged it sgd -- work: http://www.ti3.com/ non: http://thinksafely.org/ > -----Original Message----- > From: Anthony Baratta [mailto:Anthony at Baratta.com] > > When you want to talk to www.evolt.org - your computer does a > "shout-out" for > www.evolt.org to your local Domain Name Server. This > shout-out comes back as an IP > address. Then your machine sends a "Where are you?" message > to the IP Address you > just got from the Domain Name Server. If there is a response > from your target IP > Address, you then begin a communication.