Comprehensive and Detailed in-depth Step-by-Step Explanation:In OSPF, Link State Advertisements (LSAs) are used to exchange routing and topology information. Each LSA in the OSPF network is uniquely identified using a 3-tuple identifier, which consists of:
* Link State ID:
* The Link State ID uniquely identifies the LSA within the OSPF area. Its value depends on the LSA type. For example, for a Router LSA, the Link State ID is the originating router's Router ID.
* Advertising Router:
* This is the Router ID of the router that generated the LSA. It identifies which router is responsible for creating and advertising this LSA.
* LSType:
* This field identifies the type of LSA (e.g., Router LSA, Network LSA, Summary LSA, AS- External LSA, etc.). It is crucial for interpreting the purpose and content of the LSA.
The LS Sequence Number is not part of the 3-tuple that uniquely identifies the LSA. Instead, it is used to determine the most recent version of the LSA in case there are multiple instances of the same LSA.
References:
* Huawei HCIA-Datacom Study Guide, Chapter on "OSPF LSAs and LSDBs".
* RFC 2328 - OSPF Version 2 (Section 12.1.6).