1. Distance-Vector Routing Department of Computer Science Southern Illinois University Edwardsville Fall, 2013 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu CS 447 Networks and Data Communication TCP_Distance_Vector/000

2. Distance Vector Routing Cost Next A B C DEF A B C D E F 1 1 1 1 1 1 1 1 1 Cost Next A B C DEF Cost Next A B C DEF 1 B 2 B 3 B 1 C 2 C 1 C 2 C 1 B 2 B 2 C 1 C 1 D 1 F 1 F 1 E 0 S 0 S 0 S TCP_Distance_Vector/001 CS 447 Networks and Data Communication

3. Distance Vector Routing (1)A node (router) initialize its private distance vector (= routing table) for only its direct neighbor(s) (2) Routers in direct neighborhood periodically exchange their cost matrix (3) Before a router sends its routing table to its neighbor, add the whatever link cost to the neighbor to every slot in the routing table (and transmit it). (4) If a router receives the routing table from one of its direct neighbors, compare the cost in the local routing table to the one in the new table. - If the cost in the new table is lower than what is in your local routing table, update the one in the local routing table by the new (cheaper cost) and update “next hop” by the neighbor’s router’s ID (ore address) - If the higher cost is reported by the new routing table, but if the neighbor is same as the one you learned, update it anyway. TCP_Distance_Vector/002 CS 447 Networks and Data Communication

4. Routing Loops in Distance Vector A B C D X 1 1 1 1 Cost Next A B C DX 1 1 0 2 D B B S 2 D Cost Next A B C DX 1 0 3 C C S 2 X 1 C TCP_Distance_Vector/003 CS 447 Networks and Data Communication

5. Cost A B C DX Cost (Distance) Vector Routing Loops in Distance Vector A B C D X 1 1 1 1 Cost Next A B C DX 1 1 0 2 D B B S 2 D Cost Next A B C DX 1 0 3 C C S 2 NA  C 3 1 2 4  TCP_Distance_Vector/004 CS 447 Networks and Data Communication

6. Routing Loops in Distance Vector A B C D X 1 1 1 1 Cost Next A B C DX 1 1 0 D B B S 2 Cost Next A B C DX 1 0 3 C C S 2 NA  C Cost A B C DX 3 1 2 4   NA TCP_Distance_Vector/005 CS 447 Networks and Data Communication

7. Routing Loops in Distance Vector A B C D X 1 1 1 1 Cost Next A B C DX 1 1 0 2 D B B S 2 D Cost Next A B C DX 1 0 3 C C S 2 NA  C Cost A B C DX 2 2 1 3 3 TCP_Distance_Vector/006 CS 447 Networks and Data Communication

8. Routing Loops in Distance Vector A B C D X 1 1 1 1 Cost Next A B C DX 1 1 0 2 D B B S 2 D Cost Next A B C DX 1 0 3 C C S 2 C Cost A B C DX 2 2 1 3 3 3 C A B C DX 3 1 2 4 4 TCP_Distance_Vector/007 CS 447 Networks and Data Communication

9. Routing Loops in Distance Vector A B C D X 1 1 1 1 Cost Next A B C DX 1 1 0 D B B S 2 4 D Cost Next A B C DX 1 0 3 C C S 2 C Cost A B C DX 2 2 1 5 3 3 C A B C DX 3 1 2 4 4 This problem is called “Counting-to-Infinity” TCP_Distance_Vector/008 CS 447 Networks and Data Communication

10. A solution for routing loops A B C D X 1 1 1 1 Cost Next A B C DX 1 1 0 D B B S 2 2 D Cost Next A B C DX 1 0 3 C C S 2 C Cost Next A B C DX 1 1 0 D B B S 2 3 D NA  Transmit the entire routing table Router D will check “Next” field in the routing table from C. If Router D sees that the origin of the information for “X” in the RT from C is actually itself, it will not use it to update its routing table. “Split Horizon” TCP_Distance_Vector/009 CS 447 Networks and Data Communication

11. Distance Vector Routing A B C D X 1 1 1 1 1 Cost Next X X 1 Cost Next X D 2 Cost Next X D 2 Cost Next X C 3 TCP_Distance_Vector/010 CS 447 Networks and Data Communication

12. Distance Vector Routing A B C D X 1 1 1 1 1 Cost Next X Cost Next X D 2 Cost Next X D 2 Cost Next X C 3 NA  Cost Next X NA  TCP_Distance_Vector/011 CS 447 Networks and Data Communication

13. Distance Vector Routing A B C D X 1 1 1 1 1 Cost Next X Cost Next X D 2 Cost Next X C 3 NA  Cost Next X NA  Cost Next X NA  TCP_Distance_Vector/012 CS 447 Networks and Data Communication

14. Distance Vector Routing A B C D X 1 1 1 1 1 Cost Next X Cost Next X D 2 Cost Next X C 3 NA  Cost Next X NA  Cost Next X NA  Cost Next X C 4 TCP_Distance_Vector/013 CS 447 Networks and Data Communication

15. Distance Vector Routing A B C D X 1 1 1 1 1 Cost Next X Cost Next X D 2 Cost Next X C 3 NA  Cost Next X A 4 Cost Next X C 4 Cost Next X A 5 TCP_Distance_Vector/014 CS 447 Networks and Data Communication

16. Distance Vector Routing A B C D X 1 1 1 1 1 Cost Next X D 2 Cost Next X C 3 Cost Next X A 4 Cost Next X C 4 Cost Next X A 5 Cost Next X B 5 Cost Next X B 6 TCP_Distance_Vector/015 CS 447 Networks and Data Communication

17. Distance Vector Routing A B C D X 1 1 1 1 1 Cost Next X D 6 Cost Next X C 3 Cost Next X A 4 Cost Next X C 4 Cost Next X A 5 Cost Next X B 5 Cost Next X B 6 TCP_Distance_Vector/016 CS 447 Networks and Data Communication