Computer Networks · TEE · papers
Q3B · OSPF packet types
Final · 5 December 2025
TEE · Actual TEE paper · all questions · current syllabus 702AI0C023
Actual PYQ · Q3B. Explain the different types of OSPF packets used for communication between routers. [5 marks]
Answer
Diagram: OSPFv2: five distinct packet types. Labels: OSPFv2: five distinct packet types | OSPFv2: five distinct packet types | 1. Hello | Discover and maintain neighbour relationships. | 2. Database Description | Summarize link-state database contents. | 3. Link State Request | Ask for particular missing or newer LSAs. | 4. Link State Update | Carry one or more LSAs. | 5. Link State Acknowledgment | Acknowledge receipt of LSAs.
| Packet type | What it does | Simple example |
|---|---|---|
| Hello | Discover/maintain neighbours and exchange relationship parameters | Are we still neighbours? |
| Database Description (DD/DBD) | Summarize link-state database contents during synchronization | Here are the LSA headers I have |
| Link State Request (LSR) | Ask for specific missing/newer link-state information | Please send this LSA |
| Link State Update (LSU) | Carry one or more LSAs | Here is the requested or newly flooded link-state information |
| Link State Acknowledgment (LSAck) | Acknowledge receipt of LSAs | I received these LSAs |
Database Description packets carry summaries; Link State Update packets carry LSAs themselves. Do not confuse an LSA type with an OSPF packet type.
Source: Final · 5 December 2025, original question paper page 2. Original marks retained; solution independently authored.