Day-two

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IT Operation Workshop: Day-2 Interior Gateway Protocols Keyword: RIP, OSPF

Yasuhiro Ohara WIDE Project 2005/08/31

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1

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

2

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

2

• Split horizon • Split horizon with poisonous reverse • Triggered update

3

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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