OSPF Risanuri Hidayat

26 June 2015OSPF2 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

26 June 2015OSPF3 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

26 June 2015OSPF4 Reliable Flooding A C B D X LSP Y X A C B D Y D X A C B Y B D X A C Y

26 June 2015OSPF5 Link State A DG BEH CF RouterNeighborCost AB2 AD4 AE4 RouterNeighborCost BA2 BC1 BE10 RouterNeighborCost CB5 CF2 RouterNeighborCost EA5 EB2 ED3 EF2 EG1 EH8 RouterNeighborCost DA4 DE3 DG5 RouterNeighborCost FC2 FE2 FH4 RouterNeighborCost GD5 GE1 RouterNeighborCost HE8 HF6

26 June 2015OSPF6 Djikstra Algorithm CandidateCost total TreeDescription A,A,0Router A sebagai root A,B,2 A,D,4 A,E, A,A,0 Candidate list dari A ke B, cost 2 Candidate list dari A ke D, cost 4 Candidate list dari A ke E, cost 4 A,D,4 A,E,4 B,C,1 B,E, A,A,0 A,B,2Cost terendah masuk ke Tree Semua tetangga B Candidate list Dibuang, kalah dari A,E,4

26 June 2015OSPF7 Djikstra Algorithm (2) CandidateCost total TreeDescription A,D,4 A,E,4 C,F, A,A,0 A,B,2 B,C,1Cost terendah masuk ke Tree Semua tetangga C Candidate list A,D,4 A,E,4 F,E,2 F,H, A,A,0 A,B,2 B,C,1 C,F,2Cost terendah masuk ke Tree Semua tetangga F Candidate list F,E,2 kalah dari A,E,4

26 June 2015OSPF8 Djikstra Algorithm (3) CandidateCost total TreeDescription A,E,4 F,H,4 D,E,3 D,G, A,A,0 A,B,2 B,C,1 C,F,2 A,D,4Cost terendah masuk ke Tree Semua tetangga D Candidate list D,E,3 kalah dari A,E,4

26 June 2015OSPF9 Djikstra Algorithm (4) CandidateCost total TreeDescription F,H,4 D,G,5 E,B,2 E,D,3 E,F,2 E,G,1 E,H, A,A,0 A,B,2 B,C,1 C,F,2 A,D,4 A,E,4Cost terendah masuk ke Tree Kalah dari A,E,4 & E,G,1 Semua tetangga E Candidate list E,B,2 & E,D,3 kalah dr A,B,2 & A,D,4 Kalah dari A,B-B,C-C,F Kalah dari F,H,4

26 June 2015OSPF10 Djikstra Algorithm (5) CandidateCost total TreeDescription F,H,49 A,A,0 A,B,2 B,C,1 C,F,2 A,D,4 A,E,4 E,G,1Cost terendah masuk ke Tree

26 June 2015OSPF11 Djikstra Algorithm (6) CandidateCost total TreeDescription A,A,0 A,B,2 B,C,1 C,F,2 A,D,4 A,E,4 E,G,1 F,H,4

26 June 2015OSPF12 Djikstra Algorithm (7) A DG BEH CF

26 June 2015OSPF13 Open Shortest First Protocol (OSPF) Menggunakan Prinsip Link-state Ukuran maks packet OSPF untuk Cisco = 1500 octets Encapsulated di dalam IP header (Protocol = 89) IP Header OSPF PACKET OSPF Header OSPF DATA Packet Type LSP LSP Header LSP DATA

26 June 2015OSPF14 OSPF Packet Header versionTypePacket length Router ID Area ID ChecksumAuType Authentication Packet Data