Network Core: Packet Switching each end-end data stream resource contention: divided into packets r aggregate resource r user A, b packets share demand can exceed network resources amount available r each packet uses full link r congestion packets bandwidth queue, wait for link use resources used as needed r store and forward packets move one hop at a time Band/idth division into ' pieces m transmit over link Dedicated allocation m wait turn at next Resource reserva on link 1: Introduction 16
1: Introduction 16 Network Core: Packet Switching each end-end data stream divided into packets r user A, B packets share network resources r each packet uses full link bandwidth r resources used as needed, resource contention: r aggregate resource demand can exceed amount available r congestion: packets queue, wait for link use r store and forward: packets move one hop at a time m transmit over link m wait turn at next link Bandwidth division into “pieces” Dedicated allocation Resource reservation
Network Core: Packet Switching 10 Mbs Ethernet statistical multiplexing 1.5 Mbs queue of packets 45 Mbs waiting for output b璽粤E Packet-switching versus circuit switching: human restaurant analogy other human analogies? 1: Introduction 17
1: Introduction 17 Network Core: Packet Switching Packet-switching versus circuit switching: human restaurant analogy r other human analogies? A B C 10 Mbs Ethernet 1.5 Mbs 45 Mbs D E statistical multiplexing queue of packets waiting for output link
Network Core: Packet Switching Packet-switching packet packet switch destination store and forward behavior r break message into smaller chunks 234 packets r Store-and-forward switch waits until chunk has completely arrived then forwards/routes 5000 4998 ood agog.1 600 r Q: what if message was sent as single unit? time (msec. 1: Introduction 18
1: Introduction 18 Network Core: Packet Switching Packet-switching: store and forward behavior r break message into smaller chunks: “packets” r Store-and-forward: switch waits until chunk has completely arrived, then forwards/routes r Q: what if message was sent as single unit?