RIP v 1 and v 2 RFC 1058

Distance Vector Network Discovery 10. 1. 0. 0 E 0 10. 2. 0. 0

Distance Vector Topology Changes Process to update this routing table A • Updates proceed

Distance Vector Topology Changes Process to update this routing table Router A sends out

Distance Vector Topology Changes Process to update this routing table B Process to update

Problem: Routing Loops 10. 1. 0. 0 E 0 10. 2. 0. 0 A

Symptom: Counting to Infinity 10. 1. 0. 0 E 0 10. 2. 0. 0

Solution: Defining a Maximum 10. 1. 0. 0 E 0 10. 2. 0. 0

Solution: Split Horizon 10. 1. 0. 0 E 0 10. 2. 0. 0 A

Solution: Poison Reverse 10. 1. 0. 0 E 0 10. 2. 0. 0 A

Solution: Hold-Down Timers Network 10. 4. 0. 0 is unreachable Update after hold-down Time

Solution: Triggered Updates Network 10. 4. 0. 0 is unreachable 10. 1. 0. 0

Implementing Solutions in Multiple Routes D 10. 4. 0. 0 E X B C

Implementing Solutions in Multiple Routes (cont. ) Network 10. 4. 0. 0 is possibly

Implementing Solutions in Multiple Routes (cont. ) D Update after holddown time 10. 4.

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RIP v 1 and v 2 RFC 1058 & RFC 2453 Routing Information Protocol

Illustration 1 Good case

Distance Vector Network Discovery 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table S 0 10. 3. 0. 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 E 0 0 • Routers discover the best path to destinations from each neighbor

Distance Vector Network Discovery 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table S 0 10. 3. 0. 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 E 0 0 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 1 10. 2. 0. 0 S 0 1 10. 1. 0. 0 S 0 1 • Routers discover the best path to destinations from each neighbor

Distance Vector Network Discovery 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table S 0 10. 3. 0. 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 E 0 0 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 1 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 2 10. 1. 0. 0 S 0 1 10. 1. 0. 0 S 0 2 • Routers discover the best path to destinations from each neighbor

Illustration 2 Bad case

Distance Vector Topology Changes Process to update this routing table A • Updates proceed step-by-step from router to router Topology change causes routing table update

Distance Vector Topology Changes Process to update this routing table Router A sends out this updated routing table A • Updates proceed step-by-step from router to router Topology change causes routing table update

Distance Vector Topology Changes Process to update this routing table B Process to update this routing table Router A sends out this updated routing table A • Updates proceed step-by-step from router to router Topology change causes routing table update

Problem: Routing Loops 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table 10. 3. 0. 0 S 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 E 0 0 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 1 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 2 10. 1. 0. 0 S 0 1 10. 1. 0. 0 S 0 2 • Each node maintains the distance from itself to each possible destination network

Problem: Routing Loops 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table 10. 3. 0. 0 S 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 E 0 Down 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 1 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 2 10. 1. 0. 0 S 0 1 10. 1. 0. 0 S 0 2 • Slow convergence produces inconsistent routing X

Problem: Routing Loops 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table 10. 3. 0. 0 S 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 E 0 2 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 1 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 2 10. 1. 0. 0 S 1 1 10. 1. 0. 0 S 0 2 • Router C concludes that the best path to network 10. 4. 0. 0 is through Router B X

Problem: Routing Loops 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table 10. 3. 0. 0 S 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 S 0 2 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 3 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 4 10. 1. 0. 0 S 0 1 10. 1. 0. 0 S 0 2 • Router A updates its table to reflect the new but erroneous hop count X

Symptom: Counting to Infinity 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table 10. 3. 0. 0 S 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 S 0 5 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 4 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 3 10. 1. 0. 0 S 0 1 10. 1. 0. 0 S 0 2 • Packets for network 10. 4. 0. 0 bounce between routers A, B, and C, incrementing hop count X

Solution: Defining a Maximum 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table 10. 3. 0. 0 S 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 S 0 16 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 16 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 16 10. 1. 0. 0 S 0 1 10. 1. 0. 0 S 0 2 • Define a limit on the number of hops to prevent infinite loops X

Solution: Split Horizon 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table X 10. 3. 0. 0 S 0 B S 1 Routing Table X 10. 4. 0. 0 S 0 C E 0 Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 S 0 0 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 1 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 2 10. 1. 0. 0 E 1 2 10. 1. 0. 0 S 0 2 • It is never useful to send information about a route back in the direction from which the original packet came X

Solution: Poison Reverse 10. 1. 0. 0 E 0 10. 2. 0. 0 A S 0 Routing Table 10. 3. 0. 0 S 0 B S 1 Routing Table 10. 4. 0. 0 S 0 C E 0 X Routing Table 10. 1. 0. 0 E 0 0 10. 2. 0. 0 S 0 0 10. 3. 0. 0 S 1 0 10. 4. 0. 0 S 0 Infinity 10. 3. 0. 0 S 0 1 10. 4. 0. 0 S 1 1 10. 2. 0. 0 S 0 1 10. 4. 0. 0 S 0 2 10. 1. 0. 0 E 1 2 10. 1. 0. 0 S 0 2 • Routers set the distance to infinity if the destination is routed on that link

Solution: Hold-Down Timers Network 10. 4. 0. 0 is unreachable Update after hold-down Time 10. 1. 0. 0 10. 2. 0. 0 E 0 A S 0 Update after hold-down Time S 0 10. 3. 0. 0 B S 1 10. 4. 0. 0 S 0 C E 0 X Network 10. 4. 0. 0 is down then back up then back down • Router keeps an entry for the network down state, allowing time for other routers to recompute for this topology change

Solution: Triggered Updates Network 10. 4. 0. 0 is unreachable 10. 1. 0. 0 E 0 Network 10. 4. 0. 0 is unreachable 10. 2. 0. 0 A S 0 10. 3. 0. 0 B S 1 10. 4. 0. 0 S 0 C E 0 X • Nodes send messages as soon as they notice a change in their routing table

Implementing Solutions in Multiple Routes D 10. 4. 0. 0 E X B C Routing Table 10. 4. 0. 0 A E 0 Infinity

Implementing Solutions in Multiple Routes (cont. ) Network 10. 4. 0. 0 is possibly down D 10. 4. 0. 0 E B X Update after holddown time A Network 10. 4. 0. 0 is possibly down C

Implementing Solutions in Multiple Routes (cont. ) Network 10. 4. 0. 0 is possibly down D Update after holddown time 10. 4. 0. 0 E Network 10. 4. 0. 0 is possibly down B A Update after holddown time X C

Implementing Solutions in Multiple Routes (cont. ) D Update after holddown time 10. 4. 0. 0 E Packet for Network 10. 4. 0. 0 B A Update after holddown time X C