OSPF packets

Intra-area - O
Inter-area - O IA (Summary routes)
External - O E2 or O E1

Preference order for destinations with multiple routes:

1. Intra-area 
2. Inter-area
3. External E1 (external+internal cost)
4. External E2 (only external cost)

LSA Types:

Type 1 (RL): Router Links.
Type 2 (NL): Network Links.
Type 3 (SL): Summary Links.
Type 4 : ASBR Summary Links.
Type 5 (EL): External Links.