Ipv4 carries 32 bit addresses on each packet olen 15

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Unformatted text preview: storing it temporarily if necessary before forwarding it onwards –  We use sta8s8cal mul8plexing to share link bandwidth over 8me 12 6 10/23/13 Datagram Model •  Packets contain a des8na8on address; each router uses it to forward each packet, possibly on different paths ISP’s equipment 13 Datagram Model (2) •  Each router has a forwarding table keyed by address –  Gives next hop for each des8na8on address; may change A’s table (ini8ally) A’s table (later) C’s Table E’s Table B B 14 7 10/23/13 IP (Internet Protocol) •  Network layer of the Internet, uses datagrams (next) –  IPv4 carries 32 bit addresses on each packet (olen 1.5 KB) Payload (e.g., TCP segment) 15 Virtual Circuit Model •  Three phases: 1.  Connec8on establishment, circuit is set up •  Path is chosen, circuit informa8on stored in routers 2.  Data transfer, circuit is used •  Packets are forwarded along the path 3.  Connec8on teardown, circuit is deleted •  Circuit informa8on is removed from routers •  Just like a telephone circuit, but virtual in the sense that no bandwidth need be reserved; sta8s8cal sharing of links 16 8 10/23/13 Virtual Circuits (2) •  Packets only contain a short label to iden8fy the circuit –  Labels don’t have any global meaning, only unique for a link ISP’s equipment 17 Virtual Circuits (3) •  Each router has a forwarding table keyed by circuit –  Gives output line and next label to place on packet H1 Circuit #1 1 F A...
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