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OSPF. Risanuri Hidayat. Link State. Strategy send to all nodes (not just neighbors) information about directly connected links (not entire routing table) Each node creates a packet called link-state packet (LSP) Link State Packet (LSP) contains id of the node that created the LSP
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OSPF Risanuri Hidayat
Link State • Strategy • send to all nodes (not just neighbors) information about directly connected links (not entire routing table) • Each node creates a packet called link-state packet (LSP) • Link State Packet (LSP) contains • id of the node that created the LSP • A list of directly connected neighbor of that node, with the cost of the link to each directly connected neighbor • sequence number (SEQNO) • time-to-live (TTL) for this packet OSPF
Link State (cont) • Reliable flooding • store most recent LSP from each node • forward LSP to all nodes but one that sent it • generate new LSP periodically • increment SEQNO • start SEQNO at 0 when reboot • decrement TTL of each stored LSP • discard when TTL=0 OSPF
LSP X Y A LSP B B C X D Y C B C B Y X Y X A LSP D D D C A A LSP LSP LSP Reliable Flooding OSPF
4 5 4 3 1 A D G E F H C B 2 5 8 2 10 1 6 2 5 2 4 Link State OSPF
Djikstra Algorithm OSPF
C A D G B E H F 4 4 1 2 1 2 4 Djikstra Algorithm (7) OSPF
IP Header OSPF PACKET OSPF DATA OSPF Header Packet Type LSP LSP LSP LSP LSP LSP LSP LSP DATA LSP Header Open Shortest First Protocol (OSPF) • Menggunakan Prinsip Link-state • Ukuran maks packet OSPF untuk Cisco = 1500 octets • Encapsulated di dalam IP header (Protocol = 89) OSPF
version Type Packet length Router ID 8 31 0 16 Area ID Checksum AuType Authentication Authentication Packet Data OSPF Packet Header OSPF