Technical Tip: How latency affects WGET file transfer

GNU Wget is a free software package (see what is free software?) for retrieving files using HTTP, HTTPS, FTP, and FTPS: the most widely used Internet protocols. It is a non-interactive command-line tool, so it can easily be called from scripts, jobs, terminals, etc., without X-Windows support.

In this article, the tests done on Fortinet LAB will show the effect of latency when applied to a network used by WGET to transfer files.

Test 1 - A direct connection between FortiGates.

Test 1a - Download a file of 4.7GB from the File server without latency.

• Result: Bandwidth 70-90MB/s (560-720Mbit/s).

Test 1b - Download a file of 4.7GB from the File server with a latency of 50ms.

• Result: Bandwidth 1-5MB/s (8-40Mbit/s).

Test 2 - IPsec tunnel between FortiGates.

Test 2a - Download a file of 4.7GB from the File server without latency via IPsec.

• Result: Bandwidth 40-60MB/s (320-480Mbit/s).

Test 2b - Download a file of 4.7GB from the File server with a latency of 50ms via IPsec.

• Result: Bandwidth 800B-3MB/s (6.4-24Mbit/s).

Conclusion: The WGET application is very sensitive to latency. Comparing tests 1a and 1b shows that the bandwidth was reduced from 560-720Mbit/s to 8-40Mbit/s, i.e. a 95-99% reduction. Similar results were noticed when traffic crossed the IPsec.