As with any protocol, the capability to scale is important because it allows a network to grow in a controlled and stable manner. Many factors determine whether a network will successfully scale. If a network is inherently unstable, it will be difficult to scale. The instabilities might be because of flapping links, which frequently are not under the control of the network operator. However, the network operator can impose certain changes to contain the instabilities.
The main factors that contribute to network scalability are as follows:
Number of routers
Number of links
Number of internal and external routes
Stability of links
Processing capacity (CPU)
The flooding ...