IT Operation Workshop: Day-2 Interior Gateway Protocols Keyword: RIP, OSPF
Yasuhiro Ohara WIDE Project 2005/08/31
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RIP
RIPv2 is specified in [1]. RIP has following major limitations. 1. network’s diameter ≤ 15 hops 2. may depend upon ”counting to infinity” to converge
Node A
Node B
Node C Time
To C
via -
hop ∞
To C
via -
hop ∞
via dir
To C
hop 1
routing update C
-
∞
C
2
C
C
dir
1
C
dir
1
routing update C
3
B
C
2
C
Figure 1: distance vector principle
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The problems and remedies
Node A
Node B
Node C Time
To C
via B
hop 3
Node A
To C
via C
hop 2
To C
x
Node B
via dir
hop 1
Node C
C
B
3
C
-
∞
C
dir
1
C
B
3
C
A
4
C
dir
1
Figure 2: Bouncing Effect
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• Split horizon • Split horizon with poisonous reverse • Triggered update
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OSPF
Figure 3: Database exchange
LSA
Figure 4: LSA flooding
• link state principle • Link State Advertisement and LSDB • Dijkstra algorithm or SPF computation • Hello Protocol • DR Election • Areas • How to set Costs !? 3
References [1] G. Malkin. RIP Version 2. RFC 2453, IETF, November 1998.
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