Bandwidth Question

[dj214]

Hello All:

We currently have 2 - 3mb T1 bundles each running through their own identical firewall. 1 bundle is a RF wireless circuit and the other a standard frame relay bundle. I'm seeing the frame relay bundle simply bury the RF line as far as performance and reliability and wanted to know if anyone has had any experience with RF lines or perhaps could explain why the difference. I ran a series of tests on the 2 lines with a brief description of the test and the results below:

Note: no other traffic on either line during testing.

Set up 1 GIG file transfers to an FTP server behind each firewall, ran for an hour and opened another until 3 sessions were open simultaneously.

The results:

RF line -

1 FTP session - max transfer rate of 150K with 1400kbs showing in the bandwidth monitor.

2 FTP sessions - max transfer rate of 140k with 2200 kbs on the bandwidth monitor.

3 FTP sessions - max rate 125kb sec with 2600kbs on the bandwidth monitor.

Frame Relay Bundle:

1 FTp session - 350 kbs transfer rate and the bandwidth moonitor pegged at 3000kbs.

Didn't even bother with 2 and 3.

I simply cannot pish the RF line hard enough to max it out. I cannot get even, consistent bandwidth out if it. I don;t have alot of experience with RF lines but I would have to assume that either our ISP has an issue, or this is just a downside to RF lines.

The last test I will conduct is to jump in front of the firewall and conduct a transfer test just to ensure that it is not the firewall. I have a felling the results will be the same.

Does anyone have any experience with RF lines and or have any insights into what I am seeing here?

Thanks in advance.

DJ

[lgijssel]

Currently I am working a lot with all kinds of RF lines, varying from WLAN to satellite links and from that experience I might have the answer for you:

Did you already compare the latency of both links? RF links often have a signifcantly higher round-trip time than wired lines.

A higher latency has a direct impact on the througput, regardless of the available bandwidth so this might explain the difference.

You might want to try and adjust your protocol stacks to this situation altough it is not certain to help. Just google for "latency performance tuning".

Regards,

Leo

[dj214]

Thanks Leo - I'm actually getting better response time to the 1st hop on the RF line than I am on the copper. I beleive the RF line goes copper after the first hop.

I honestly beleive what I am seeing is just the downside of RF over copper. I have very little experience in RF and I know we're getting the bandwidth alot cheaper......which would explain why.

[Wilson Samuel]

Hi DJ,

We have had 2 Mbps WLAN for Internet, however we never noticed any significant delay on that and I would always prefer the WLAN over the Copper.

However since it was Internet connectivity and we never ran any delay sensitive traffic on that WLAN link, hence may be even if any delay existed we might not have noticed.

Kind Regards,

Wilson Samuel

[dj214]

What is your allotted bandwidth on that line and I'd be interested in seeing if your getting full allotted bandwidth.

I suspect that we have some equipment issue somewhere in our implementation that is causing the problem.

We really never noticed it either until we began investigating an issue whereby our clients we downloading files and ocassionally coming up corrupt when they tried unzipping them.

We were concerned with the possibility of line errors being the root cause and stumbled on this bandwidth issue. Having very little Wlan experience, I was just trying to get an idea of what could be going on.

Thanks for taking the time to reply.

[Wilson Samuel]

Hi DJ,

We have had 2 Mbps dedicated bandwith through the WLAN coming as Ethernet Link on L-1 terminated on a 2621 Fa0/0 Interface.

Also, please check that how far is the POP Antenna from your site, also, please ensure that Antenna alignment is correct, as in most of the WLAN cases the Antenna type and Antenna alignment plays a big role, along with the Line of Sight (both Visible Light and Radio)

Ideally there shouldn't be significant difference between Copper and WLAN over the response time.

Regards,

Wilson Samuel

[dj214]

Thanks - will work with our ISP to have these things checked.

[mike.botha]

There might want to check the MTU that you are able to get over the RF link and adjust the MTU and MSS to match the RF link.