4. The Setup

All tests used the setup shown in Figure 8. The IxChariot console and first endpoint were run on an Athlon 64 3000+ machine running WinXP Pro SP1 that was on its own private 10/100 network connected to a CMC Emulation Engine a/b/g.

The EE was used to generate from 1 to 64 802.11g vSTAs, which all were associated with the access point under test. Since the AP is just a bridge, a second computer - a 2.4 GHz Pentium 4 running WinXP Home SP1 - was connected to the AP on a second private LAN and used as the second IxChariot endpoint to receive all the traffic.

Figure 8: The Test setup

The AP under test and Emulation Engine were located roughly 6 feet (2m) apart and no other 2.4 GHz stations or interference was present. You may think that the latter statement is a bold one on my part, given how widespread the use of wireless networking equipment is. But I live in a rural location without access to broadband and believe me, the 2.4 GHz airwaves are damned quiet around here!

As I mentioned previously, simple ping traffic generation can be done from the EE's web interface. But I quickly abandoned that approach as not flexible enough. I instead opted to use the EE's command-line interface and external mode that allowed vSTAs to accept traffic from an external generator - Ixia's IxChariot in this case.

I set each vSTA so that it could be stimulated by IxChariot, and left everything else at the EE's defaults. Note that the default settings make each vSTA a persistent connection, which means that after their initial authentication and association with the target AP, they are supposed to stay that way. This means my tests didn't include vSTAs cycling through authentication, association, de-authentication and disassociation. The Emulation Engine is capable of doing this, but I didn't have the time or the inclination to get into the Perl programming interface that is required to make the EE perform those tricks.

I decided to configure all the APs and EE so that 128bit WEP was used, since no self-respecting WLAN should be running without at least the protection - flawed though it may be - that WEP affords. I left all access points in their default mode settings, all of which were set to either "Auto" or "Mixed (11b/g)".

I also left access point 11b protection settings at their defaults, figuring this didn't matter since I made sure there were no 11b STAs in range during my testing. By the way, only the Buffalo Tech WLA-G54C came with protection enabled by default, and the SMC / 3Com twins didn't provide this setting at all.

Finally, I left any "burst" mode settings at their defaults which mirrored the 11b protection settings - or lack thereof in the case of the SMC / 3Com twins. Note that everything involved in the test was powered through APC UPSes, to avoid problems due to power glitches.