1. SDN for IP transport optimization

1.1 IP transport today

Historically, IP networks are based on hop-by-hop shortest-path routing.

In order to use a path other than the shortest path and to differentiate routing by flow, two solutions are possible:

• implementation of hop-by-hop routing policies. But this introduces a very high level of complexity (need to maintain the same policy on all equipment, manage failure cases, etc.), which greatly reduces its potential use;

• MPLS traffic engineering, the most frequently deployed solution.

From an architectural point of view, IP networks are most often built on WDM or OTN transmission networks, offering Ethernet interfaces for access and high data rates...