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Stable paths for information exchange over the Internet are vital for the revolutionizing current networking infrastructures into a fully integrated Future Internet. The Internet consists of numerous self-administered autonomous systems. Fluctuation of routes degrades the delivery of packets and changes the distribution of traffic load over the network. Border Gateway Protocol (BGP) is an important network protocol that may cause instability in the Internet.
The global routing protocol BGP is used as a path vector routing protocol for the autonomous systems. The information of routes learned from external BGP nodes is spread inside the autonomous systems. BGP does not redistribute the information learned from the iBGP (internal BGP) neighbor within the autonomous system to avoid the redundancy of updates (Chakraborty & Sardar, 2014). Therefore, in past, one of the alternatives iBGP full mesh is used, which required the full mesh BGP connection among the iBGP peers for the visibility of complete topological information.
In iBGP full mesh topology, every router connects with other routers through iBGP sessions. The fully mesh connection between all the routers produces shorter convergence time after receiving the path information advertised by the eBGP (external BGP) neighbor. On the other hand, the full mesh iBGP connection makes the topology more complex in terms of installation. This also causes scalability problem within the autonomous system. Thus, iBGP full mesh connections are only suitable for the small topologies. Consequently, the large-scale autonomous systems required the solutions which eliminate the scalability issues.
In an autonomous system, the iBGP scaling issues have been alleviated with the help of BGP confederations and Route Reflectors (Sun et al., 2016). Both the solutions manage the complexity and scalability. In the first approach, the network operators designate some special routers which are known as Route reflector (Sarakbi & Maag, 2010). The BGP Route Reflector works as a representative of the set of routers which advertised the learned path to the connected neighboring routers. Several cases have been reported in the literature where Route Reflectors clients have selected the sub-optimal paths due to the invisibility of optimal paths (Sun et al., 2016). For this reason, BGP Route Reflectors require major changes in the path selection policies and configurations (Schrieck et al., 2010). To handle the scalability issue, BGP confederation subdivides the autonomous system into several sub-autonomous systems (Sub AS). Each subdivided autonomous system behaves as a whole autonomous system and the other subpart works as an external autonomous system (AS). The Sub-AS may have own iBGP rules (Flavel & Roughan, 2009). The subdivision of AS decreases the number of iBGP connections significantly. Although the subdivision of AS increases complexity and maintenance overhead in the AS. Notwithstanding the fact, the flexibility of the AS in the existing ASes must be stable and sustainable.