# A Survey on Efforts to Evolve the Control Plane of Inter-Domain Routing
## 5 Classification of Efforts for Evolving the Control Plane
### Efforts to Evolve the Control Plane of Inter-Domain Routing
#### 5.2.2 Incremental Improvement
YAMR is deployed in a distributed way, where the control plane of YAMR can be implemented as an extension of the BGP protocol. The main contribution of the Selective Announcement Multi-Process (STAMP) protocol is executing several BGP instances inside the AS that is used to discover complementary paths [66]. The goal of those complementary paths is established paths that are not affected by the same set of network events. Thus, the STAMP requires minimal modification of the BGP process to become an operational solution and to achieve an improvement in routing stability compared with the standard BGP protocol. The integration between SDN technologies and BGP has already been investigated and implemented by some researchers [69; 36]. The integration with SDN solutions and BGP networks is vital to a practical deployment of SDN proposals. In fact, modern SDN controllers have mechanisms to exchange BGP information with BGP speaker components that behave as legacy routers. For example, the Open Network Foundation (ONF) ATRIUM project proposes a framework to support BGP by use of the ONOS controller [70] and Quagga [71]. Another widely-used SDN controller is the Ryu [72] support, interworking between OpenFlow and BGP, since a BGP function is installed in the Ryu SDN framework. The COntrol INbound traffic (COIN) framework [34] proposed to evolve the control plane routing system with the OpenFlow protocol. The COIN framework expanded the Ryu SDN controller to provide mechanisms for controlling inbound traffic from ISPs to its multi-homed ASs customers. Thus, the customers could manage how network traffic reaches them through the use of applications in the SDN controllers' ISPs. Those applications, when required and allowed, override the BGP behavior of the ISPs' network infrastructure to fulfil the customer's network traffic management requirements. With the focus on merging SDN and traditional network concepts, SIREN [36] presented a proposal to integrate the control plane of those two approaches. It combines BGP and SDN principles to improve the convergence time of the BGP at the inter-domain level. To reach that goal, SIREN allows an AS to outsource routing functionality and export it to its ISP control. SIREN is an extension of the previous idea explored in [PERSON] et al. [73]. However, a pitfall of SIREN is that this approach limits the ability of the innovation of an AS, considering that a domain has to be subordinate to the requirements established by the outsourcing agreements for managing its network. Using the idea of overriding the BGP behavior, the proposal of Software-Defined Internet exchange (SDX) [67] and its extension Industrial-Scale Software-Defined Internet Exchange Point (iSDX) [68] explore the SDN centralized control inside the Internet Exchange Point (IXP). iSDX allows the reduction of the forwarding table size of OpenFlow devices used by the IXP participants, the creation of more flexible forwarding policies and the end-to-end enforcing of QoS. iSDX requires a brokerage system to establish multilateral peering; innovation is processed in the Layer 2 scheme (using Ethernet MAC addresses), and a third party orchestrates traffic between participants. [PERSON] [10] presented a new architecture to manage network traffic in the inter-domain using OpenFlow networks. The idea of the proposed architecture was to use BGP and SDN technologies to provide new mechanisms that allow different ASs to coordinate how traffic should be handled between them using network applications inside SDN controllers. Thereby, a proof of concept scenario demonstrated that stub ASs can appropriately manage network traffic towards its domain by controlling the parameters of those network applications in its ISPs. The achieved results indicated the potential of the idea to apply different strategies for routing in the inter-domain environment.