Dead periods on LAN - is this a normal characteristic of a heavily loaded network?

Dead periods on LAN - is this a normal characteristic of a heavily loaded network?

I'm on a 10Mbit LAN in my residence at uni where there's a lot of file sharing going on, as the day goes on the network gets progressively more problematic, I assume this is down to the traffic building up as people get up (students work on a whole different time zone )

So at 8 am I can upload or download to/from a friends ftp at a consistant 600-800 Kb/sec. Once the the network loads up in the evening instead of just getting progressively slower I seem to get spurts where i can still transfer quickly (peeking up around 800 ksec for a few secs) then big gaps where it goes almost usuably slow, somtimes down to bytes a second then it'll suddenly pick up again for a few seconds and the whole process repeats. As the day goes on the fast periods get shorter and the dead spots get longer (first they're seconds long, but eventually minutes).

This happens with 2 different LAN adaptors (1 onboard, one generic pci) I'm not entirely sure of the topology of the network, but it's large and gets heavily loaded.

What I'm wondering is if this is normal behaviour to be expected of a big LAN or if theres something i can tweak to counter it

It sounds like it is a problem with the network being oversubscribed horribly. Another possibility is a layer 1 problem. Definately sounds like an overload of the network though.

If the network is built with hubs, then you are getting collisions. When a collision occurs, all traffic on the network halts momentarily.

If it is a switched network... then you may have a version of the blaster virus (which floods the network attempting to propogate itself...), a poorly crimped cable, a malfunctioning nic, etc.

But my first guess would be that the network uses hubs. Solution: replace hubs with switches.

or decrease the collision domain with cheap routers. or a bridge made out of an old p100. you could do that for your area, if two hubs are cascaded together and causing problems.

Eh.... gus... a switch creates seperate collision domains anyways. Specifically, a collision domain for every port on the switch. I believe you're thinking of broadcast domain, which requires a router to create.

However, now that I reread your post, I am lead to believe that the universitys internet connection is simply becoming saturated (100% use), or that the router they are using is not up to the task at hand.

Either way, you should confront the network administrator about it.

The problem is definately related to the network and not my hardware, they're making improvements and the situation is getting noticably better Of course they won't tell us what the topology or improvements is/are....

Even if your lan is completely switched, you can still max the bandwidth of a switch, which would still cause network unusability(is that a word? ). Sounds to me like there are too many users on the network.

Even if they are using hubs, and switches would solve the problem, not like he can go to the university and say hey, upgrade your network or i'm leaving. i'm guessing it's not really an option for him to go and replace all the hubs with switches.

Is your friends FTP site on the network with you, or across the net?

It's on the network here, there's also a dc hub which I believe is the cause of most of the problems, the other day while the dc hub was down everything was super fast. I think the uni is putting new gigabit backbones in which hopefully will help

atconc said:

It's on the network here, there's also a dc hub which I believe is the cause of most of the problems, the other day while the dc hub was down everything was super fast. I think the uni is putting new gigabit backbones in which hopefully will help

Click to expand...

Yep! All you can do is wait!

But that will help a lot. Sounds like your uni's tech dept has been lax with teh upgrades! What uni you go to?

I go to the university of essex in the UK. It's only the network in the accomodation that they neglect, the main campus network, comp labs etc are smoking fast

yes, i realize that a switch does this as well, its a bridge of sorts. but i think you might be more inclined to take an old computer from one of the labs and turn it into a router/bridge than to buy something and replace what the university has in place. but talk to your network administrator and ask if there is anything you could do to help get more bandwidth going in your dorm.

just being practical, as well as trying not to repeat what has been said.

Re: Dead periods on LAN - is this a normal characteristic of a heavily loaded network

atconc said:

I'm on a 10Mbit LAN in my residence at uni where there's a lot of file sharing going on, as the day goes on the network gets progressively more problematic, I assume this is down to the traffic building up as people get up (students work on a whole different time zone )

So at 8 am I can upload or download to/from a friends ftp at a consistant 600-800 Kb/sec. Once the the network loads up in the evening instead of just getting progressively slower I seem to get spurts where i can still transfer quickly (peeking up around 800 ksec for a few secs) then big gaps where it goes almost usuably slow, somtimes down to bytes a second then it'll suddenly pick up again for a few seconds and the whole process repeats. As the day goes on the fast periods get shorter and the dead spots get longer (first they're seconds long, but eventually minutes).

This happens with 2 different LAN adaptors (1 onboard, one generic pci) I'm not entirely sure of the topology of the network, but it's large and gets heavily loaded.

What I'm wondering is if this is normal behaviour to be expected of a big LAN or if theres something i can tweak to counter it

Click to expand...

10mb LAN? Are hubs used, or switches? 10mb is pretty slow for a LAN now, so I'd guess they're just using hubs. If there is a lot of traffic going through the hub/s, collisions can occur, which results in slowdowns on the network when certain systems have to repeat their transmissions. Only one computer can talk at a time on a hub =)

-ben

I think they've deleberately left the connections in the accomodation at 10mbit so we don't use toooo much bandwidth, I don't know whether they're hubs or switches, cos they won't tell us the topology for what ever reasons.