Introduction to OSPF

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RFC 1247: OSPF Version 2

The first three sections of this specification give a general overview of the protocol’s capabilities and functions. Sections 4-16 explain the protocol’s mechanisms in detail. Packet formats, protocol constants, configuration items, and required management statistics are specified in the appendices. The following list runs through the sections of the RFC.

  Section 1: Introduction. This section of the RFC briefly explains the history and background of the OSPF. It also includes a brief description of some of the more important design goals surrounding its use and operation.
  Section 2: Topological Database. This section of the RFC goes into great detail regarding the layout and operation of OSPF’s database. It includes information regarding its functionality and usage.
  Section 3: Splitting the AS into Areas. This section of the RFC details the methods and procedures regarding the segmentation of Autonomous Systems (AS) into various OSPF areas. It also discusses some of the unique characteristics the routers within an area will have regarding the OSPF protocol.
  Section 4: Functional Summary. This section of the RFC contains information regarding the overall functionality of the protocol and includes the operation of the shortest path algorithm.
  Section 5: Protocol Data Structures. This section of the RFC describes in detail the terms of its operation on various protocol data structures. Discussion and a list is provided that comprises the top-level OSPF data structures. Areas, OSPF interfaces, and neighbors also have associated data structures that are described later in this specification.
  Section 6: The Area Data Structure. This section of the RFC discusses the characteristics of areas and how the protocol operates within that structure.
  Section 7: Bringing Up Adjacencies. This section of the RFC discusses, in general terms, the purpose and function of how OSPF forms adjacencies with the majority of routers that are neighbors.
  Section 8: Protocol Packet Processing. This section of the RFC discusses the general processing of routing protocol packets and their importance. The packet header of these routing protocol packets is also broken down for the reader.
  Section 9: The Interface Data Structure. This section of the RFC details their purpose and place within the operation of the protocol of an interface.
  Section 10: The Neighbor Data Structure. This section of the RFC covers the protocol’s ability to converse with other routers that are considered its neighbors. This discussion includes additional information on adjacencies and how they are part of this structure.
  Section 11: The Routing Table Structure. This section of the RFC details the structure of the routing table and how the information provided within it can be used to forward packets correctly.
  Section 12: Link-state Advertisements. This section of the RFC discusses the functions of the five distinct types of link-state advertisements and how they form into the link-state database. Additional information regarding the link-state header structure is provided.
  Section 13: The Flooding Procedure. This section of the RFC provides an overview of how link-state update messages provide the mechanism for flooding advertisements throughout an area.
  Section 14: Aging The Link-state Database. This section of the RFC describes in detail the process of how a link-state advertisement uses its age field after it is placed in the database to determine which advertisement is most current.
  Section 15: Virtual Links. This section of the RFC provides information on the purpose and operation of virtual links and the part they play in ensuring the connectivity of different areas through the backbone.
  Section 16: Calculation Of The Routing Table. This section of the RFC details the OSPF routing table calculation.

RFC 1248: OSPF Version 2 Management Information Base

This RFC defines the experimental portion of the Management Information Base (MIB). Specifically, it defines objects for managing OSPF version 2. Additional information regarding the content of this RFC will not be provided, as it quickly became obsolete twice over through the publication of RFCs 1252 and 1253.

RFC 1252: OSPF Version 2 Management Information Base

This RFC defines the experimental portion of the Management Information Base (MIB). Specifically, it defines objects for managing OSPF version 2. This RFC replaced RFC 1248, which contained some minor errors in referring to “experimental” and “standard-mib.” Additional information regarding the content of this RFC will not be provided, as it too quickly became obsolete.

RFC 1253: OSPF Version 2 Management Information Base

This RFC defines the experimental portion of the Management Information Base (MIB). Specifically, it defines objects for managing OSPF version 2. This memo replaces RFC 1252, which contained an error in the “standard-mib” number assignment in Section 5.

This RFC discusses network management and which RFCs were used as the basis for defining the new MIB objects associated with OSPF. A thorough discussion is then presented so that the reader has the ability to fully comprehend the standards of the MIBs implemented with OSPF.

RFC 1364: BGP OSPF Interaction

This RFC defines the various network design specifications and considerations to keep in mind when designing Autonomous System Border Routers (ASBR) that will run BGP with other ASBRs external to the Autonomous System (AS) and OSPF as its Interior Gateway Protocol (IGP).

RFC 1370: Applicability Statement for OSPF

This is probably one of the few RFCs that actually seems to encourage comments and suggestions. The purpose of this RFC was driven by the requests of users and vendors who wanted IP routers to have the ability to “interoperate” through the use of an Interior Gateway Protocol (IGP). Because OSPF was designed as an “open” standard, the protocol was recommended as follows:

“An IP router that implements any routing protocol (other than static routes) is required to implement OSPF [1] and the OSPF MIB [2]. Within OSPF, implementation of all features except TOS (Type-of-Service) routing is required; implementation of TOS routing is recommended.” [direct quote rfc 1370]


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OSPF Network Design Solutions
OSPF Network Design Solutions
ISBN: 1578700469
EAN: 2147483647
Year: 1998
Pages: 200
Authors: Tom Thomas

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