The OSPF Routing Protocol - Départements

DIX, Département d’Enseignement et de Recherche d’Informatique
INF566 - Networks and Protocols
Exercise 3 - The OSPF Routing Protocol
Objectives
The objectives for today’s exercises are for you to:
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Acquire detailed understanding of the OSPF Routing Protocol
This in part, by way of designing an extension to the OSPF Routing Protocol, rendering
it applicable also over “strange, wireless links”.
Materials
For today’s exercises, you will need to consult the following documents, available on the WWW of
the course:
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RFC5218 - What Makes For a Successful Protocol
OSPF and Integrated IS-IS
RFC2328 - OSPFv2
Start by reading the introduction, the neighbor state machines, as well as that which concerns
NBMA interfaces, in the two latter.
Ecole Polytechnique - DIX, Département d’Enseignement et de Recherche d’Informatique
91128 Palaiseau cedex - Tél : +331 69 33 34 67 – Fax : +33 1 69 33 30 14
Email: [email protected] – WWW: http://www.dix.polytechniaue.fr/
DIX, Département d’Enseignement et de Recherche d’Informatique
Exercises:
It is a good idea to work with a buddy for todays exercises, and you are required to
1.
Consider OSPF and evaluate it by way of the criteria given in RFC5218
Note, this is a “preparation for your project”
2.
Now, familiarize yourself with basic OSPFv2, as described in the slides and in RFC
2328.
Consider the example network presented below. It is composed of several routers, the
figure gives the IP addresses of their interfaces and prefixes for stub networks. Links
have metrics denoted by m. AS 1 runs OSPF as IGP routing protocol. Router R5 learns
through BGP the information about the networks in AS 2 and injects it into AS 1. Area 1
is not a stub area. Give all advertisements either generated or transmitted by R3.
Ecole Polytechnique - DIX, Département d’Enseignement et de Recherche d’Informatique
91128 Palaiseau cedex - Tél : +331 69 33 34 67 – Fax : +33 1 69 33 30 14
Email: [email protected] – WWW: http://www.dix.polytechniaue.fr/
DIX, Département d’Enseignement et de Recherche d’Informatique
3.
Now, consider an area in an AS, exclusively composed by routers with wireless
interfaces / links, as indicated in the figure below:
a.
Clearly, the designated router / backup designated router mechanisms do not
work as intended for when forming adjacencies. Explain the reasons as to why
this is, as well as the consequences of running “stock OSPF” over a link of this
nature?
b.
While we are at it, enumerate the objectives of designated router / backup
designated router selection, as well as the conditions under which they work.
c.
This is the constructive part of the exercise.
Just as the designated router / backup designated router mechanism was
conceived so as to provide certain optimizations for when running over a full
broadcast link, design mechanism(s) so as to enable an OSPFv2 area to run over
these “weird links”. You are expected to describe the mechanism proposed and
provide justification (i.e. we do not expect full and complete proofs) for your
proposal.
Note that you are expected to detail changes to both the HELLO protocol, the
adjacency formation, the database exchange and the LSA flooding -- if any
(and, if not, you are expected to justify why not....)
4.
Email your answers to Mark & Thomas before January 28, at noon
[email protected]
Ecole Polytechnique - DIX, Département d’Enseignement et de Recherche d’Informatique
91128 Palaiseau cedex - Tél : +331 69 33 34 67 – Fax : +33 1 69 33 30 14
Email: [email protected] – WWW: http://www.dix.polytechniaue.fr/