Key Concept #2: Dumb Network Original Internet design interior nodes (routers)have no knowledge* of ongoing connections going through them Not: how you picture the telephone system works Which internally tracks all of the active voice calls Instead the postal system Each Internet message ("packet" ) self-contained Interior routers look at destination address to forward If you want smarts, build it"end-to-end, not hop-by-hop Buys simplicity robustness at the cost of shifting complexity into end systems Today's Internet is full of hacks that violate this9 Key Concept #2: Dumb Network • Original Internet design: interior nodes (“ r o u ters” ) h a v e no knowledge* of ongoing connections going through them • Not: how you picture the telephone system works – Which internally tracks all of the active voice calls • Instead: the postal system! – Each Internet message (“packet”) self-contained – Interior routers look at destination address to forward – If you want smarts, build it “end-to-end” , not “hop-by-hop” – Buys simplicity & robustness at the cost of shifting complexity into end systems * Today’s Internet is full of hacks that violate this