# SALMA: A Novel Middlebox Infrastructure System Based on Integrated Subnets
## 9 Conclusions and Future Directions  
Middleboxes are considered an essential part of current network infrastructure, since they provide critical services, such as security, performance enhancement, and traffic shaping. We found that the cost of middleboxes in today's networks is close to the cost of L3 routers. Furthermore, middleboxes are topology-dependent, as they usually reside between trusted and untrusted networks. Hence, their availability is a serious concern and has a severe impact on network operation. Given the rapid growth of SDN solutions and the recent advances in middlebox configuration management, the consolidation of middleboxes is becoming easier than before. In this work, we introduced a new practical solution, called _SALMA_, that addresses several challenges associated with middleboxes, including cost, low utilization, load balancing and topology-dependent deployment. Middleboxes of the same type are consolidated into a single middlebox, and the policy sequence is encoded in the packet address and into the separated tables of the middleboxes' subnet switch. Various types of middleboxes are aggregated into multiple subnets, and the middlebox manager is responsible for forwarding the traffic to the right middleboxes' subnet, and balancing the traffic load among them. In the future, we are planning on studying the optimal placement of the middleboxes' subnets and the optimal members in every subnet. Additionally, it is interesting to look at the possibility of integrating SALMA with the emerging network security solutions, such as the intelligent security operations center (iSOC). Conceptualization, A.A. and A.S.; methodology, A.A.; software, A.A.; validation, A.A. and A.S.; formal analysis, A.A.; data curation, A.S.; writing--original draft preparation, A.A.; writing--review and editing, A.S.; visualization, A.S. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Institutional Review Board Statement:** Not applicable. * (19) OpenFlow Discovery Protocol and Link Layer Discovery Protocol. Figshare. Available online: [[https://groups.geni.net/geni/wiki/OpenFlowDiscoveryProtocol#WhatisLLDP](https://groups.geni.net/geni/wiki/OpenFlowDiscoveryProtocol#WhatisLLDP)]([https://groups.geni.net/geni/wiki/OpenFlowDiscoveryProtocol#WhatisLLDP](https://groups.geni.net/geni/wiki/OpenFlowDiscoveryProtocol#WhatisLLDP)) (accessed on 3 August 2022). * (20) [PERSON]; [PERSON]; [PERSON] Understanding BGP Misconfiguration. _SIGCOMM Comput. Commun. Rev._**2002**, 32, 3-16. [CrossRef]
* (21) Network Firewall Security Management Software. Available online: [[https://www.solarwinds.com/security-event-manager/use-cases/firewall-security-management](https://www.solarwinds.com/security-event-manager/use-cases/firewall-security-management)]([https://www.solarwinds.com/security-event-manager/use-cases/firewall-security-management](https://www.solarwinds.com/security-event-manager/use-cases/firewall-security-management)) (accessed on 3 August 2022). * (22) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Reproducible Network Experiments Using Container-based Emulation. In Proceedings of the 8 th International Conference on Emerging Networking Experiments and Technologies, CoNEXT '12, Nice, France, 10-13 December 2012; pp. 253-264. * (23) POX. Available online: [[https://github.com/noxrepo/pox](https://github.com/noxrepo/pox)]([https://github.com/noxrepo/pox](https://github.com/noxrepo/pox)) (accessed on 3 August 2022). * (24) iPerf. Available online: [[https://iperf.fr/](https://iperf.fr/)]([https://iperf.fr/](https://iperf.fr/)) (accessed on 3 August 2022). * (25) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] AOMB: Extensible Open Middleboxes with Commodity Servers. In Proceedings of the Eighth ACM/IEEE Symposium on Architectures for Networking and Communications Systems, ANCS '12, Austin, TX, USA, 29-30 October 2012; pp. 49-60. * (26) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] The Click Modular Router. _ACM Trans. Comput.