TWC ISP Connectivity Problem

D

d4nnn

[H]ard|Gawd
Joined
Apr 8, 2004
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Hey guys,

Had a question for everyone..We just took over a servicing a school that had a contract with another company. The problem I am noticing is when I download large files, I will maintain full speed (~1MB/s), but the download will stop and then drop all the way down to zero. It will then come back after a few seconds

Some details:

We have a 10down/2up TWC Business connection at a small school.

Network has a main cisco managed switch, 2 HP 2900 managed switches.. 10-15 unmanaged switches, fiber drops to each managed switch and to each unmanaged switch (placed in each room) and about 8-10 WAPs across the school.

It has three servers, one Xserve for open directory, one Win2008 Server for local caching on a school program they use. and the other is the old server we are going to replace.

We also have 1 sonicwall. We are looking at about ~50 or so desktops that don't get used all too often. ~30-50 laptops also not used all too often.

There is no VoIP and most network traffic is within the LAN.

Any thoughts? The TWC tech said we are oversaturating out network (we are using the pipe @ 11down/2up instead of the provided 10/2... which doesn't make sense).

Thanks!
 
Most likely some kind of packet queuing somewhere, I would highly suggest a web cache such as Squid and WSUS on that kind of network then apply QoS to start with.
//Danne
 
Without graphing your internet usage, TWC may or may not be correct in that statement they made.
Your Sonicwall should support SNMP. Get MRTG or PRTG up and running and graph the WAN interface. See how much bandwidth you are using.
 
Please let me know what you find on this. I have a customer with a Watchguard firewall that is complaining of the same issue when he downloads files at full tilt.
 
Ok, I won't be on site till friday, but I'll see if I can do something remotely.
 
Update:

So far.. One of the managed switches was causing huge latency issues.

I have now updated the sonicwall and have a bandwidth monitoring software. So far the issues have gone away, but I will now be monitoring whats going on.

So far I'm at about 50% usage. We'll see in a few days.
 
Keep in mind SNMP polls at fairly long intervals, when monitoring interfaces it may or may not give u a true picture of the bandwidth utilization. If you had a user use the entire pipe for the minutes between poll intervals, it could saturate the line but not show in a graph. You can set the poll interval much closer together for more accuracy, but also creates a lot more traffic depending on how many devices/interfaces you're monitoring.

The best way to have better visibility into the connection find a sflow / netflow analyzer.

With that in mind, for SNMP monitoring I do like cacti.
 
Are you running multiple vlans or a single vlan. If you are using a single vlan. If it is possible to do multiple vlans you can narrow down specifics subnets.
 
We have multiple Vlans.

I have been monitoring it and it looks like I am maxed out during school hours. So I guess the TWC guy was right about that. However, the connection is not dropping out and resetting constantly anymore.. that might have been solved by looking at the internal devices.

I will have to narrow it down to see where the majority of the bandwith is coming from. All I'm seeing is "General HTTP".
 
What you describe sounds similar to an issue I had. Sonicwall was blocking downloads after halfway through. I don't recall if it was blocking thinking it was a security breach or if it was a tcp session failure or something but just take a look at the sonicwall log next time you notice some issue.
 
I have seen some buggy firmware some cable modems specifically the Motorola modems with IP Flood detection. Double check to see if you have a firewall in the modem provided by your ISP or if it is just bridged because I have seen ip flood detection cause the Docsis 3 modems cut transfer right in the middle.

Do you have a network monitoring system set to to see how much bandwidth certain devices are using? I have a PF Sense Router installed on one of the Production Networks I manage and I have a bandwidth montioring package which tells me which IP/machine is using the most Bandwidth.
 
There is an SMC cable model installed in bridge modem to the sonicwall.

I am currently using the built in sonicwall bandwidth monitoring software. I will have to go with a program like that to specific which ip's are taking up the most bandwidth.
 
I have the SMC-D3GN Docsis 3 Modem. Since the New York City Division of TWC started the 50x5 service. I think this SMC is rock solid and I had no issues with it at all. Good luck with investigation.
 
update!

Located most of the bandwith hogging coming from one of the learning centers with 30 imacs. Each session, all 30 log into flash coded games for the kids to use..

I have installed BWM with the sonicwall for condensing the traffic flow throughout the school and that seems to be working, but it looks like we will eventually need to go for more bandwidth.

As you have stated naota, the SMC is pretty rocksolid. Now if you can just tell your socal friends to bump us up to that 50x5 connection that would be awesome.

Thank you everyone!
 
the 50x5 connection I Have is residential services. I do know they should have at least 15x2 or 20x2 in your area. I would say visit https://twcbc.com/West/Products/Internet/ Plug in the zip code where the school is located and see whats available there in your area and within the pricepoint of the budget. If you need speeds faster they do offer Dedicated services but I don't know what the pricing is. . I would say for now. You may want to do some traffic shaping to further optimize the traffic either letting higher priority traffic like Voice, Local Video Services and Local Web services and destinations needed for high priority and then throttle down the lower priority traffic like external web traffic.
 
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