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Bài giảng Các giao thức định tuyến: DSDV (Destination-sequenced distance-vector routing protocol)

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Bài giảng Các giao thức định tuyến: DSDV (Destination-sequenced distance-vector routing protocol). Chương này cung cấp cho học viên những nội dung gồm: introduction distance-vector; the property of ad-hoc networks; routing protocol; routing algorithm; link-state; DSDV protocol; route advertisements;... Mời các bạn cùng tham khảo chi tiết nội dung bài giảng!

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Nội dung Text: Bài giảng Các giao thức định tuyến: DSDV (Destination-sequenced distance-vector routing protocol)

  1. DSDV Destination-Sequenced Distance-Vector Routing Protocol
  2. Outline n  Introduction n  Distance-Vector n  DSDVProtocol n  Summary
  3. Introduction n  The property of ad-hoc networks n  Topology may be quite dynamic n  No administrative host n  Hosts with finite power
  4. Introduction n  The properties of the ad-hoc network routing protocol n  Simple n  Less storage space n  Loop free n  Short control message (Low overhead) n  Less power consumption n  Multiple disjoint routes n  Fast rerouting mechanism
  5. Introduction n  Routing Protocol: n  Table-driven (proactive) n  Source-initiated on-demand (reactive) n  Hybrid n  Routing Algorithm n  Link-State algorithm: n  Each node maintains a view of the network topology n  Distance-Vector algorithm: n  Every node maintains the distance of each destination
  6. Link-State n  Like the shortest-path computation method n  Each node maintains a view of the network topology with a cost for each link n  Periodically broadcast link costs to its outgoing links to all other nodes such as flooding
  7. Link-State A link costs F H B E C G D
  8. Distance-Vector n  known also as Distributed Bellman-Ford or RIP (Routing Information Protocol) n  Every node maintains a routing table n  all available destinations n  the next node to reach to destination n  the number of hops to reach the destination n  Periodically send table to all neighbors to maintain topology
  9. Distance Vector (Tables) 1 2 A B C Dest. Next Metric … Dest. Next Metric … Dest. Next Metric … A A 0 A A 1 A B 3 B B 1 B B 0 B B 2 C B 3 C C 2 C C 0
  10. Distance Vector (Update) B broadcasts the new routing information to his neighbors Routing table is updated (A, 1) (A, 1) (B, 0) (B, 0) (C, 1) (C, 1) 1 1 A B C Dest. Next Metric … Dest. Next Metric … Dest. Next Metric … A A 0 A A 1 A B 3 2 B B 1 B B 0 B B 1 C B 3 2 C C 1 C C 0
  11. Distance Vector (New Node) broadcasts to update tables of C, B, A with new entry for D (A, 1) (A, 2) (B, 0) (B, 1) (C, 1) (C, 0) (D, 2) (D, 1) (D, 0) 1 1 1 A B C D Dest. Next Metric … Dest. Next Metric … Dest. Next Metric … A A 0 A A 1 A B 2 B B 1 B B 0 B B 1 C B 2 C C 1 C C 0 D B 3 D C 2 D D 1
  12. Distance Vector (Broken Link) 1 1 1 A B C D Dest. Next Metric … Dest.c Next Metric … Dest. Next Metric … … … … … … … … … … D B 3 D C 2 D B D 1 ∞
  13. Distance Vector (Loops) (D, 2) (D, 2) 1 1 1 A B C D Dest. Next Metric … Dest. Next Metric … Dest. Next Metric … … … … … … … … … … D B 3 D C 2 D B 3
  14. Distance Vector (Count to Infinity) (D,5) (D,4) (D,4) (D,3) (D,2) (D,2) 1 1 1 A B C D Dest. Next Metric … Dest.c Next Metric … Dest. Next Metric … … … … … … … … … … D B 3, 5, … D C 2, 4, 6… D B 3, 5, …
  15. Distance Vector n  DV not suited for ad-hoc networks! n  Loops n  Count to Infinity n  New Solution -> DSDV Protocol
  16. DSDV Protocol n  DSDV is Destination Based n  No global view of topology
  17. DSDV Protocol n  DSDV is Proactive (Table Driven) n  Each node maintains routing information for all known destinations n  Routing information must be updated periodically n  Traffic overhead even if there is no change in network topology n  Maintains routes which are never used
  18. DSDV Protocol n  Keep the simplicity of Distance Vector n  Guarantee Loop Freeness n  New Table Entry for Destination Sequence Number n  Allow fast reaction to topology changes n  Make immediate route advertisement on significant changes in routing table n  but wait with advertising of unstable routes (damping fluctuations)
  19. DSDV (Table Entries) Destination Next Metric Seq. Nr Install Time A A 0 A-550 001000 B B 1 B-102 001200 C B 3 C-588 001200 D B 4 D-312 001200 n  Sequence number originated from destination. Ensures loop freeness. n  Install Time when entry was made (used to delete stale entries from table)
  20. DSDV (Route Advertisements) n  Advertise to each neighbor own routing information n  Destination Address n  Metric = Number of Hops to Destination n  Destination Sequence Number n  Rules to set sequence number information n  On each advertisement increase own destination sequence number (use only even numbers) n  If a node is no more reachable (timeout) increase sequence number of this node by 1 (odd sequence number) and set metric = ∞
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