Can area routing reduce the routing traffic in OSPF?

[Bin Liu <[e-mail]>]

Hello there,

Even though area routing is proposed to reduce the routing traffic, I quite
doubt its effect. OSPF is mainly applied for for transit AS in term of its
ability to accommodate a large number of external routes. However, as we
know, each AS external LSA floods throughout the whole network
transparently. So when the majority of LSAs in the database of OSPF router
are AS external LSAs, which dominate the amount of link bandwidth consumed
by OSPF traffic [OSPF protocol analysis], the benefit of reducing routing
traffic by dividing network into areas is seriously undermined.

If my inference is right, then
1. What is the benefit of area routing, which makes routing not flexible.
2. Does that the longer update period in OSPF (i.e., 30 minutes between the
origination of LSAs) accomplish the work, i.e., reduce routing traffic.

Many thanks and looking forward to seeing reply.

yours
Bin Liu

ps. Relevent information
In 1991, the number of external LSAs in 15 router NASA Science Internet
(NSI) is 496, in another 14 router BARRNet, the number is 1816 [experience
with OSPF, RFC 1246].