# 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  
Proposals are made to incorporate new BGP network capabilities by changing the protocol behavior, extensions of the BGP or additional control information that is used with the BGP protocol. Table 4 presents the works related to incremental improvements of inter-domain routing. For inter-domain routing, the authors in [38] claimed that the fully-distributed path selection computation in IP routers limits the capacity of individual ASs in terms of management scalability of path selection. Thus, they proposed a Routing Control Platform (RCP), a platform that avoids the complexity of fully-distributed path computation in the inter-domain routing system by centralizing routing control logic. Due to the architecture network abstraction designed by the RCP, it did not describe how, in fact, to explore the path diversity of inter-domain routing; hence, these criteria are not applicable to the RCP. However, the RCP is one important area of research and a precursor of SDN concepts, in which it is indicated that the control plane of a domain should be built in a centralized way [43]. In addition to centralized routing control and to enable multipath routing on the Internet (the BGP uses a single best path), Multi-path Interdomain ROuting (MIRO) [63] proposed the use of overlay networks and specific packet tags to enable multiple paths for inter-domain routing. The idea was to allow a new control plane logic where ASs negotiate alternative paths, as needed, from their \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Proposal and Authors** & **Concepts** & **Approach** & **Control Plane Placement** & **Explore Path Diversity** \\ \hline RCP: [PERSON] et al. [38] & Traditional & Architecture & Logical Centralized & N/A \\ MIRO, [PERSON] et al. [63] & Traditional & Architecture and Protocol & Distributed & Inter-domain negotiations \\ R-BGP, [PERSON] et al. [64] & Traditional & Protocol & Distributed & Alternative routes \\ YAMG, [PERSON] et al. [65] & Traditional & Protocol & Distributed & Alternative routes \\ STAMP, [PERSON] et al. [66] & Traditional & Protocol & Distributed & Alternative routes \\ COIN, [PERSON] and [PERSON] [34] & SDN & Architecture & Centralized & Based on flows \\ SIREN, [PERSON] et al. [36] & SDN & Architecture & Centralized & Based on flows \\ SDX and iSDX, [PERSON] et al. [67; 68] & SDN & Architecture and Protocol & Logical Centralized & Inter-domain negotiations \\ [PERSON] [10] & SDN & Architecture & Centralized & Based on flows \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Classification for proposals to evolve the inter-domain routing with incremental improvements. MIRO, Multi-path Interdomain ROuting; R-BGP, Resilient BGP; YAMR, Yet Another Multipath Routing Protocol; STAMP, Selective Announcement Multi-Process; COIN, COntrol INbound; iSDX, Industrial-Scale Software-Defined Internet Exchange Point. ISPs. MIRO defaults to the single-path routing provided by the conventional BGP, but allows ASs to negotiate alternative paths as needed. This provides flexibility where required while remaining compatible with BGP. Compared to source routing, MIRO gives transit ASs more control over the flow of traffic in their networks. An idea to protect the inter-domain links against failures is the Resilient BGP (R-BGP) [64]. R-BGP produces failover paths to mitigate the unavailability of the best path selected from the BGP decision process. Thus, when a link fails, the failover path was already computed and ready to be used, avoiding the path exploration time for discovering new paths to networks affected by the failed link. Furthermore, to avoid unavailability when external links fail, Yet Another Multipath Routing Protocol (YAMR) [65] is a resilient solution that explores advertising additional paths that are not contained in the primary path (resulting from the BGP's best path algorithm). Thus, each alternative path receives a label that identifies the links the path needs to avoid.