# A Comprehensive Survey of In-Band Control in SDN: Challenges and Opportunities
## 4 A Survey of In-Band SDN Control in SDN
### Network Bootstrapping  
This section examines works that include network bootstrapping in their design. Additionally, some of them might provide automatic routing and/or failure recovery as well. As a summary, Table 4 gathers all works, ordered by publication year. **[PERSON]** et al. [79] devise an automatic bootstrapping method to set up the in-band control connection. To the best of our knowledge, they were the first to implement an in-band configuration channel for OpenFlow. They provide a very detailed and thorough explanation of the bootstrapping process. The switch relies on Dynamic Host Configuration Protocol (DHCP) to learn the IP address and Address Resolution Protocol (ARP) to learn the MAC address of the controller. The controller uses packet probes similar to Link Layer Discovery Protocol (LLDP) to acquire the full network topology. The method is tested on emulated networks of different shapes (linear, ring, star, and mesh topologies) and sizes, using the NOX controller. The tests show minimal bootstrapping times and good scalability response. **[PERSON]** et al. [80] apply an in-band SDN control plane in which they use standard Ethernet switches on a DC network for the communication of Virtual Machines (VMs). They place a special software agent in each server and a central SDN controller with a directory server and a route algorithm server to control all communications. Based on the in-band control plane, they could also implement load balancing and fast failure recovery. **[PERSON]** et al. [6] devise a new in-band control plane called ERIC, a hybrid-band scalable control designed for DC networks. They use pre-computed rules installed in the switches, both for the initial bootstrapping and in case of link failures or network congestion; however, they do not provide further details about it. They tested ERIC against the out-of-band approach on a Mininet simulator with the Floodlight controller and show similar RTT with a 9% throughput loss. **[PERSON]** et al. [81] propose a SDN in-band control plane to be deployed on standard avionic and industrial Ethernet networks to simplify network configuration and save additional cabling, which otherwise, means weight, complexity, and cost. Using the OpenFlow protocol in aeronautical use-cases requires: (1) the network has to be configurable via in-band, (2) the configuration must be done within a certain time, and (3) the configuration traffic must not interfere with data traffic. Two mechanisms are devised: (1) when a switch starts, it needs some preinstalled rules to connect to the controller, while at the same time, packet storm should be avoided; (2) a limitation to the in-band channel traffic based on traffic policing and admission-control techniques. They implement a proof-of-concept in Mininet and evaluate bootstrapping, fail-over times, and the influence of rate limitation in the overall configuration time under linear, ring, and mesh topologies. **[PERSON]** et al. [82] define FASIC, which permits automatic bootstrapping of an OVS-based network by leveraging OVS Database (OVSDB), which allows the configuration of the SBI in the ODL controller. With the Floodlight controller, they monitor the congestion of the in-band connections. They use the ODL controller as a manager to move in-band