Server virtualization has caused the scale of networks to increase as well, and this increased scale
has put pressure on layer two and layer three networks as they exist today. Some of these pressures
can be alleviated to some degree by tunnels and other types of technologies, but fundamental network
issues remain, even in those situations. Consequently, the degree of network virtualization required to
keep pace with data center expansion and innovation is not possible with the network technology that
is available today.
To summarize, advances in data center technology have caused weaknesses in the current networking
technology to become more apparent. This situation has spurred demand for better ways to construct
and manage networks [9], and that demand has driven innovation around SDN [10].