## 3 Reducing Transmission Overhead without Compromising Throughput
### Overview of LARep  
In an earlier study [28] on the impact of spatial locality on routing performance, we observed that less messages were delivered to destination nodes whose home regions were located farther away from that of the source. This also corresponds with results obtained in Section 2.4.2 (cf. Figure 10). Based on these findings, the basic idea behind LARep is to increase throughput by compensating for distance with more message copies, while keeping account of the progress messages have made towards their respective destinations in order to control excessive replication. Since buffer overflows may cause generated message copies to be lost, LARep implements a mechanism that drops messages according to the progress they have made towards their destination. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Acceptable Performance Does**} & \multicolumn{2}{c}{**Suitable under Increasing**} & \multicolumn{2}{c}{**Scenario**} \\ \cline{2-5}
**Replication Approach** & \multicolumn{2}{c}{**Not Require**} & & & **Lapest of Spatial** & **Node** & **Adapability** \\ \cline{2-5}  & **(Frequently) Metadata** & **Global** & **Knowledge** & **Locality** & **Population** & \\ \hline Gossiping [54] & \(\surd\) & \(\surd\) & \(\surd\) & \(\times\) & \(\times\) \\ Timer threshold [54] & \(\surd\) & \(\surd\) & \(\surd\) & \(\times\) & \(\times\) \\ VACCINE [54] & \(\times\) & \(\surd\) & \(\times\) & \(\times\) & \(\surd\) \\ [PERSON] et al. [55] & \(\times\) & \(\times\) & \(\surd\) & \(\times\) & \(\times\) \\ [PERSON] \& [PERSON] [57] & \(\surd\) & \(\surd\) & \(\times\) & \(\times\) \\ [PERSON] et al. [58] & \(\surd\) & \(\times\) & \(\surd\) & \(\times\) & \(\times\) \\ [PERSON] \& [PERSON] [56] & \(\surd\) & \(\times\) & \(\times\) & \(\surd\) & \(\times\) \\ [PERSON] et al. [49] & \(\times\) & \(\surd\) & \(\surd\) & \(\times\) & \(\surd\) \\ [PERSON] et al. [59] & \(\surd\) & \(\times\) & \(\times\) & \(\surd\) & \(\times\) \\ [PERSON] \& [PERSON] [53] & \(\surd\) & \(\surd\) & \(\times\) & \(\times\) & \(\times\) \\ [PERSON] et al. [51] & \(\surd\) & \(\surd\) & \(\times\) & \(\surd\) & \(\surd\) \\ [PERSON] et al. [60] & \(\surd\) & \(\times\) & \(\surd\) & \(\times\) & \(\times\) \\ Our proposal (LARep) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Replication approaches for reducing transmission overhead and their main features. LARep's message dropping policy gives more priority to messages that have made less progress towards their destination nodes as well as those that the carrier node can make more contributions towards delivering. In order to curb the effects of the \"slow start\" phase (which happens especially in higher degrees of spatial locality when the source node is unable to encounter a sufficient number of relay nodes that have higher forwarding utilities), LARep starts by spraying message copies. However, instead of utilizing a fixed quota during the spray phase, LARep implements a variable quota that adapts to current network conditions, such as the progress that the message has made towards the destination node and the distance between the source and destination nodes. In order to maximize throughput, LARep refrains from assuming strict rules for deleting messages that have been forwarded after the spray phase. Rather, messages are removed from the buffer only when there is need to create space for incoming or newly generated messages and the proposed message dropping policy is tasked with the selection of messages to be dropped. Therefore, after the spray phase, messages continue to be replicated to relay nodes presenting higher forwarding utilities, but only when the copies in the network are deemed insufficient. Hence, the task of minimizing transmission overhead without compromising throughput can be divided into four subtasks:  
1. Determining a measure for the relative distance between the source and destination nodes;
2.