IGPprotokollat

IGPprotokollat, often translated as the interior gateway protocol protocol data unit, refers to the fundamental message or packet that an Interior Gateway Protocol (IGP) uses to communicate routing information inside an autonomous system. Each IGP defines its own PDUs and encoding, but all PDUs serve the same purpose: to convey topology, reachability, metrics, and policy data that routers use to build and maintain their routing tables. PDUs are exchanged between neighboring routers to establish adjacencies, exchange state information, and drive convergence after topology changes.

Different IGPs organize PDUs in different ways. For neighbor discovery and maintenance, PDUs keep adjacencies alive and confirm liveness; for topology dissemination, they carry the actual routing information. In OSPF, the protocol uses a set of PDUs including Hello, Database Description, Link-State Request, Link-State Update, and Link-State Acknowledgment to discover neighbours and flood link-state data. In IS-IS, PDUs include types such as IIH (Hello), Link-State PDUs (LSP), and CSNP/PSNP to synchronize network topology. Routing-update information in distance-vector protocols such as RIP is carried in UDP datagrams that list routes and metrics. The emphasis across IGPs is efficient, bounded-control exchange within an AS, with PDUs designed to minimize overhead and respond quickly to changes.

PDUs are typically transported over IP networks (for IP-based IGPs) and may include authentication or integrity mechanisms to prevent misconfiguration or spoofing.