Technical Tip: SMB speed on IPSec depending of the WAN quality

[ydong01]

Description	This article describes the SMB speed related to packet loss and delay in the WAN/IPSec network.
Scope	FortiGate.
Solution	The SMB protocol is designed for local file sharing with low latency. Even a slight packet loss or delay in these exchanges can cause noticeable slowdowns. Therefore, it is highly sensitive to packet loss rate, out-of-order, latency, and other issues in network communication, meaning even a small issue can significantly impact its performance.  Example: PC -> 40F (Spoke) -> 1G (IPSec)-> (Hub) -> Server. Without Delay and Packet Loss, SMB speed is around 70MB/s in PC, almost 500 Mbps in an IPSec tunnel in Spoke. With 5ms Delay and without Packet Loss, SMB speed is around 56MB/s in PC, almost 400 Mbps in IPSec tunnel in Spoke. With 5ms Delay and 6% Packet Loss, SMB speed is around 9MB/s in PC, almost 52 Mbps in IPSec tunnel in Spoke. Compare with Reorder Corrupt Duplicates, such as out-of-order, corrupt, affecting speed much faster than others: No Delay, no packet loss, 6% Corrupt, SMB speed is around 27.9MB/s in PC, almost 214 Mbps in IPSec tunnel in Spoke. Different delays cause different Max speeds: Conclusion: SMB is not suitable for file transfer over a WAN link; it is for local file sharing. SMB speed depends on the WAN link quality.