# NDN Content Store and Caching Policies: Performance Evaluation
## 6 Conclusions  
This work evaluated the performance of four caching policies (i.e., LRU, LFU, FIFO and random) in two network topologies (i.e., NDN testbed and Abilene) configured with seven different scenarios (different number of CS), and with two different content request rates, 100 and 5 packets/s. Additionally, one specific scenario with a consumer request rate of 1000 packets/s was simulated. For each scenario, two configurations were considered: one with 41 consumers and 1 producer and another composed of 32 consumers and 10 producers. The requests were considered, following the MZipf distribution. Two values of the skewness factor were chosen in order to evaluate the performance considering two different content types. The results were achieved through simulations using ndnSIM.  
In general, LFU performs better for all considered metrics. For NDN testbed, random presents similar performance as the LRU replacement policy when the network is equipped with CS in more than 80% of its routers. A different situation is presented by the Abilene network, where LRU presents a slightly higher performance than random.  
For a lower value of \(\alpha\), the popularity of contents in the MZipf distribution decreases, thus decreasing the CHR. For all scenarios, the retrieval delay, traffic, and hop-count present relatively constant but high values compared to the configuration with higher \(\alpha\). This is expected because with lower popularity, the interest takes more time and goes through a longer route to fetch the requested content.  
Although desirable, the evaluation of the performance with a higher content request rate was limited by the available computational resources. This limitation may be overcome in future, and this work may then be extended. Moreover, as referred to earlier, the extension of this work to include more caching replacement policies, combining different caching decision strategies, may be considered. Additionally, for future work, it would be interesting to evaluate the performance of these policies in a dynamic network, such as the _vehicular ad hoc network_ (VANET), similar to the work in [64], which is specific to caching decision strategies.  
Figure 9: Interest re-transmissions, NDN testbed with 32 consumers and 10 producers.  
**Author Contributions:** Conceptualization, E.T.d.S. and J.M.H.d.M.; methodology, E.T.d.S.; software, E.T.d.S.; validation, E.T.d.S., J.M.H.d.M. and A.L.D.C.; formal analysis, E.T.d.S.; investigation, E.T.d.S.; resources, E.T.d.S., J.M.H.d.M. and A.L.D.C.; data curation, E.T.d.S.; writing--original draft preparation, E.T.d.S.; writing--review and editing, E.T.d.S., J.M.H.d.M. and A.L.D.C.; visualization, E.T.d.S.; supervision, E.T.d.S., J.M.H.d.M. and A.L.D.C.; funding acquisition, J.M.H.d.M. and A.L.D.C. All authors have read and agreed to the published version of the manuscript.  
This work has been supported by FCT - Fundacao para a Ciencia e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020.  
Not applicable.  
**Data Availability Statement:** The data presented in this study are openly available in zenodo.org accessed on 24 January 2022, at [[https://doi.org/10.5281/zenodo.5902395](https://doi.org/10.5281/zenodo.5902395)]([https://doi.org/10.5281/zenodo.5902395](https://doi.org/10.5281/zenodo.5902395)) accessed on 24 January 2022.  
The authors declare no conflict of interest.