bandwidth issue

gaby_978 · December 2008

Hey guys,

Its been a while since I posted anything.

I work for an ISP NOC. Sometimes we get trouble tickets regarding bandwidth. What is the best way for a customer to troubleshoot their ckt for bandwidth verification. All I have access is to the routes that connects the customer to our MPLS network. I dont have access to customers routers.

Most of the time i will look at the ckt, check for bounces, utilization, errors and stuff. I will also run some extended pings trying to max the ckt out to prove the customer that the bandwidth is there. In some instances I will have the cust plug a laptop to their router and do some uploads and download test. I had a customer who has a 45meg ckt and download and upload speeds were not good according to cust.

I guess I need a better understanding on this, but everytime i have a bandwidth trouble ticket I cant seem to prove to the customer that there is nothing wrong. Most of the time they complain about the time it takes them to download a big file. They believe that because they have a big ckt the downloads or uploads should be faster.

Can somebody give an explanation as far as the bandwidth and speed relationship. Will the higher the bandwidth, the faster the download? How does this really works?

Thanks in advance..

JavonR · December 2008

Theoretically? Yes. The higher the bandwidth, the faster a client will be able to download a file.

So, if they have a 45Mb connection - they should be able to download at a rate of 5.625MB per second (45/8 to figure out bytes per second). That is an insane rate, and I highly doubt they will be able to hit that rate from 1 source, especially if it's across the internet. Things like network congestion, server upload capability, routing etc. all come into play. Now, you could certainly have several downloads going from multiple servers and you would hit that sweet spot (45mb per second, or 5.625MB). This one is a hard one for me to explain as well to customers, most can't seem to get it through their thick skull that network communication is a 2 way process. You can only download as fast as the other side can upload

dtlokee · December 2008

You should be able to see the data rate of the interface on the PE side if you work for an ISP.

networker050184 · December 2008

Obviously the Circuit is not the only piece of the puzzle here. Maybe the site they are downloading from only has a T1 or a link on their LAN that negotiated 10/half.... Could just be over utilization on either side or QoS limiting their web traffic bandwidth. Many pieces that could cause slow downloads.

malcybood · December 2008

So many questions here.....

How many users use the 45Mb pipe?

Is the issue all the time or at certain times of the day?

Do they have any "cloud computing" for content scanning i.e. Messagelabs?

Is this an MPLS link which breaks out to the internet from the cloud or to provide site to site WAN access?

Is this a core or edge site?

Is there not a customer portal that they can login to in order to check bandwidth utilisation on the CPE?

Particular applications or all applications slow?

I would bet they're choking the link somehow, which will probably depend on how strict their security policy is etc if users can download things and if it is anything they want, alternatively if their network is centralized with 20/80 rule 45MB might just not be enough bandwidth to serve their user base. If they're downloading from Windows "large" files over the WAN it's not going to be speedy depending on how many users are using it and their strategy.

Surely they have some kind of SNMP monitoring software installed or a network probe they can stick on the LAN and check for top talkers and applications?

1 - Check Bandwidth Utilisation on the ISP portal
2 - If high then dig deeper into applications / top talking applications at that site
3 - If not check the CPE for drops
4 - Check the LAN switch uplink for errors / config (half/full duplex, auto-neg or nailed up to 100mbps etc)
5 - Check for spanning tree loops / configuration on LAN switch

My bet would be it is either 1, 2 or 3 that is causing the issue. I am guessing that the 45MB connection is a fiber circuit between the NTE & POP? a break in fiber between the NTE & POP can cause these types of issues.

I would ask them to take some http watch traces www.httpwatch.com (great tool & free version is good enough) and also for general performance / route trace get them to run win MTR end-to-end over the MPLS. They may need to do it pluggd directly into the router as you previously have done the download test as proxy servers and firewalls can prevent this tool from working on the LAN. This will show if and where it's slowing down.

http://winmtr.sourceforge.net/

Get them to download WinMTR bin.zip and you download it also. This will detail every hop from you to them or to wherever they enter as the destination and highlight loss and response times etc per hop. You can then export the results to a txt or HTML file.

One thing I would also say is "good" response times to a site doesn't always tell the full story. I've had an MPLS leased line responding at 50ms which isn't great but it's not anything out of the ordinary if the site is busy, when I checked the bandwidth utilisation it was constantly maxed at 100% so bandwidth utilisation check is always first point of call when users report "slow performance" for me anyway.

HTH

bandwidth issue

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