OSPF Router Database Synchronization Using SHA-1 Digests
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Solution Overview
Problem
In Mobile Ad-hoc Networks (MANET), the overhead of maintaining routing peering with all possible neighbors is prohibitive, leading to lost forwarding paths and inefficient database exchange processes in OSPF networks, where full database synchronization is required before announcing adjacencies, wasting processing resources and network throughput.
Innovation Solution
The method involves using a SHA-1 digest value to determine database synchronization between routers, allowing them to skip or reduce database description exchanges by comparing hash values, and introducing a new bit in the OSPFv3 packet options field and a new TLV in the LLS data block to carry database digest values, enabling incremental and order-independent updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full database exchange is performed before announcing adjacency in OSPF, then database synchronization is ensured, but processing overhead and network traffic increase significantly
Solution Approach 1:
The patent extracts the essential verification function from the full database exchange process by using only the router ID and sequence number fields to determine database synchronization. This selective extraction allows routers to verify synchronization status without exchanging complete database contents, thereby reducing processing overhead while maintaining reliability.
Solution Approach 2:
Instead of performing complete database exchange, the patent applies partial action by exchanging only critical identification fields (router ID and sequence number). This partial exchange is sufficient to determine synchronization status in most cases, reducing the amount of data processing required while still ensuring database consistency when needed.
2Reliability
If full database exchange is performed before announcing adjacency, then synchronization is verified, but network throughput is reduced due to excessive database description packets
Solution Approach 1:
The patent extracts only the essential synchronization verification fields (router ID and sequence number) from the complete database description packets. By transmitting only these critical fields, the patent significantly reduces packet size and transmission overhead, thereby improving network throughput while maintaining the ability to verify database synchronization.
Solution Approach 2:
The patent uses partial database information (router ID and sequence number only) instead of complete database exchange to determine synchronization. This partial approach reduces network traffic and improves throughput while still providing sufficient information to verify database consistency and make adjacency announcements.
3Reliability
If routing peering is maintained with all possible neighbors in MANET, then forwarding paths are preserved, but overhead costs become prohibitive
Solution Approach 1:
The patent applies partial action by using only essential database fields (router ID and sequence number) for synchronization verification instead of complete database exchange. This reduction in verification overhead makes it feasible to maintain peering with multiple neighbors in MANET environments, preserving forwarding paths while keeping overhead costs acceptable.
4Reliability
If database description packets are exchanged frequently, then database synchronization is maintained, but processing resources are wasted
Solution Approach 1:
The patent extracts only the critical router ID and sequence number fields from database description packets for synchronization verification. This extraction approach maintains database synchronization reliability while significantly reducing the processing resources required to handle frequent packet exchanges, as routers only need to compare these small field values rather than processing complete databases.
Data Source
AI summary
The present invention provides a method of determining whether database located on a first router is synchronized with the database located on a second router by performing a hash function on the values contained in a link state database to derive a SHA-1 digest value. In an embodiment, the digest value is based on LSA type. The digest value is exchanged initially during a database description packet swap between the first router and second router. If the digest values are the same, the databases are already synchronized. The routers thus skip the database description packet exchange of LSAs in the database and go directly to FULL state, indicating full synchronization between databases on the first and second router and announcing adjacency to each other. If the digest differs, normal database description packet exchange is performed as specified in OSPF.