3 load-balanced T1's = how much total bandwidth?

[xyrx]

I work for a state agency that relies on another state agency for our network infrastructure. We currently do not have anyone with experience in advanced network connectivity, so we have to contract this responsibility out.

We currently have 3 T1's connected to a router. The people we contract out to insist that the 3 T1's are load-balanced, though, I highly suspect they are not. I believe they work in a way that if one T1 gets saturated, any additional connections are routed to the next T1, and so forth.

My question is, assuming that there is no network chatter going on, what would one expect to get for total bandwidth? I'm downloading large files from a website where at home (cable broadband, 3Mb) I can get around 250k/sec, but at work, I never see anything more than 130k/sec. I have another theory that the router on the other end can't handle the traffic of 3 T1's. Alot of unknowns, but I don't believe we are getting what we pay for. Anyone have any suggestions of what I could do to test this out?

 

[DigitalDragula]

The reason why your downloads are faster at home is because of the hosts servers are probably located closer to your home than at work. On the WWW, location is evrything (well at least very important). A server closer to your house will give give you faster speed rates than the ones farther. Internet traffic is also a big factor.

One way to troubleshoot the connection is to optimize all the T1's with a windows optimizing program, such as tune-up utilities 2004, or OSS Speed Booster. You can download those and others

http://www.download.com.

Another way is to load up help and support, (if you have Windows xp) wich can help you ping the T1 modems one by one. Check to see if all of the drivers are up to date. That's a very way to fix problems.

 

[jimbopalmer]

I suspect the T1's at work would allow 3 files to be downloaded at once, without slowing each other up, but cannot speed up anyone file download past the capibility of one T1.

We use two T1s for 1600 employees, and that is how ours work.

I tried to remain child-like, all I acheived was childish.

 

[xyrx]

Thanks for the info guys. I guess there's two types of balancing, from what you're telling me, jimbopalmer. One is where the 3 T1's will work like I stated before, where one T1 gets saturated and any more traffic falls over to the next T1. The other way is to combine all bandwidth into one pipe, and almost triple the speed of a T1, minus overhead. I'm not sure of the terminology, but if I wanted to call our networking people on this, I'll want to explain to them that we expected all 3 T1's to be combined. This should be possible, from what I've seen of our WAN/LAN.

 

[jimbopalmer]

for aggregation of the t1s to occur, the OTHER end needs to consider them a single pipe as well. This will require some electronics at each end (the buzzword may be inverse multiplexers)

http://www.radusa.com/Home/0,6583,2569,00.html

I tried to remain child-like, all I acheived was childish.

 

[tmt7734]

If you are getting only 130k/sec your T1's are not Bonded. I have 3 Bonded T1's (called NxT1) and get well over 500Kb/sec, this has to be setup in your ISP's router as well as your.

That however does not mean that your T1's are not "load balanced". They may have you setup in a redundancy over pure bandwidth scheme, where traffic such as SMTP is given the use of 2 T1's and HTTP or FTP are limited to only use the BW of 1 T1.

You probably want to get an explaination of how and why it's setup.

DigitalDragula, the distance from a server really has no impact on speed. Internet traffic basically travels at 186,000 miles/ sec (speed of light), so traveling halfway around the globe has little effect. However telecommunications infrastructure has a huge impact.

 

[tdelliott]

The 3 T1's are probably load balanced however, that does not mean you will get the aggregate bandwidth of three T1s.
Normally once you establish a connection your conversation will only use the one T1. The next client to establish a connection may use one of the other T1s. This is the concept of load balancing.

 

[bogeygolf]

The are several ways load sharing is accomplished, but none of them involves filling up one T1 and then going to another. Ciscos will automatically load-share either "per packet" which does a round-robin to each T1 (and evenly balances the traffic). Or on a "session" basis where individual flows (conversations) are distributed to each of the T1s. "Bonding" is more involved, usually requiring an inverse-mux to combine the T1s (or it could use multilink PPP if your provider supports it).

But how are you arriving at the 130k figure? If it is YOUR workstation getting 130k throughput, it may be that the path is providing 3 T1s of bandwidth but most of it is being used by other workstations, leaving only a little for you.

If you can, ask the people who manage the router to do a show interface for each T1 and look at the rxload and txload. This will be a ratio, some number over 255 (for example 125/255 would be half utilized). If they are load sharing all three T1s should show about the same ratio. Also if they are getting close to 255/255 then the T1s are fully utilized and that is why you are only getting a small piece of the pie.