# Towards a Highly Available Model for Processing Service Requests Based on Distributed Hash Tables
## 2 Materials and Methods
### System Scalability Based on the Intrinsic Properties of the Chord DHT
Nevertheless, despite their very good quality to balance loads, a feature which derives from the properties of the hash function, the authors have not identified DHTs and peer-to-peer networks to be used in order to simplify and make more available services of data processing. On the other hand, there is a growing need on the market for high availability in request processing services, such as for example in IP telephony and conferencing, during a time when people have been forced to used more virtual meeting means than physical ones. This is where the current original solution, for highly available processing of requests can be very useful and applicable, could become useful, while keeping in mind that the obtained high availability introduces a small but manageable delay, due to the DHT extra layer that is found between the transport layer and the application layer from the TCP/IP protocol stack. Using peer-to-peer networks as an overlay network, i.e., abstract network, is not new, this concept being often connected today also with virtualization [46]. The authors have used the DHT layer similar to how VRRP (Virtual Router Redundancy Protocol) is classically used in order to transparently provide redundancy and finally high availability in a network [47] the enormous plus of DHTs being that they are far more flexible. In the future, we would like to evaluate the improved model introduced by this paper also on a more geographically distributed architecture, in order to have even less functional dependencies among some sets of nodes, but also to see the overhead that this novel DHT-based improved solution introduces in such a deployment. Moreover, we would like to apply this recipe for a set of popular distributed request processing services, to turn each of them into highly available services, with minimum or no changes to the interface to their clients. Conceptualization, V.I. and N.T. ; methodology, V.I. ; software, V.I. ; validation, V.I. and N.T. ; formal analysis, V.I. and N.T. ; investigation, V.I. ; writing--original draft preparation, V.I. ; writing--review and editing, N.T. and V.I. ; supervision, N.T. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The authors wish to thank [PERSON] for his advice and contributions to this work. The authors declare no conflict of interest. ## References

* (1) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON] Wide-area cooperative storage with CFS. In Proceedings of the 18 th ACM Symposium on Operating Systems Principles, Banff, AB, Canada, 21-24 October 2001. * (2) [PERSON] [PERSON]; [PERSON]; [PERSON] [PERSON] LightChain: A DHT-based Blockchain for Resource Constrained Environments. arXiv **2019**, arXiv:abs/1904.00375. * (3) [PERSON]; [PERSON] Blockchain and DHT Based Lookup System Aiming for Alternative DNS. In Proceedings of the 2020 2 nd International Conference on Computer Communication and the Internet (ICCCI), Nagoya, Japan, 26-29 June 2020; pp. 98-105. * (4) [PERSON]; [PERSON] From Cloud Computing to Sky Computing. In Proceedings of the Workshop on Hot Topics in Operating Systems (HotOS: '21), Ann Arbor, MI, USA, 31 May-2 June 2021. * (5) [PERSON]; [PERSON]; [PERSON]; [PERSON] Sky computing: Exploring the aggregated cloud resources--Part i. In Proceedings of the 16 th Iberian Conference on Information Systems and Technologies, Chaves, Portugal, 23-26 June 2021. * (6) [PERSON]; [PERSON] NJ. Data replication mechanisms in the peer-to-peer networks. Int. J. Commun. Syst. **2019**, 32, e3996. [CrossRef]
* (7) [PERSON]; [PERSON] A Decentralized Distributed Database Built on Top of the Chord DHT. In Proceedings of the 8 th RoEduNet International Conference, Galati, Romania, 3-4 December 2009; pp. 151-155. * (8) MongoDB. Available online: [[https://www.mongodb.com/](https://www.mongodb.com/)]([https://www.mongodb.com/](https://www.mongodb.com/)) (accessed on 3 January 2022).