Why is it when doing a speed test (or when everyone total maxes the upload of a connection), my ping response shoots through the roof?

Posted on 2012-08-10
Medium Priority
Last Modified: 2013-12-24
This may be a very easy question to explain or answer but why is it when my internet connection cable or dsl is being taxed on the upload, which is easily noticeable during a speed test, the ping response sky rockets and everyone on the network suffers while trying to surf the web?
Question by:E J Pope
LVL 13

Expert Comment

ID: 38281915
You're using up all the bandwidth and the response time is slow.

Picture it like a running tap.  If the water is running out of the tap with nothing in the way it goes fast and the stream is very thick.  If you divert this water into different cups then the remaining water stream isn't as fast and the stream is smaller (less available to use).

Hope that makes sense.

Expert Comment

ID: 38281967
i like the analogy to running a tap.  i like the car trip analogy better:

think of this.  you have to go to the grocery store and back.  now, this is a 24-hours store to you can go whenever.

you could go at 1am - this way there is no traffic.  you get there and back super quick because no one is on the roads - all the lights are green.

or you could go at 5pm - rush hour!  everyone is on the road, you have to wait at stop lights!  round trip time is much higher.

same thing is happening with your ping response time.  too many cars on the road!  things are getting backed up at routers (traffic lights)

Expert Comment

ID: 38282054
if you feel the need, you can solve this with using a good traffic shaper / QoS in your routing device, e.g. any m0n0wall device.
Who's Defending Your Organization from Threats?

Protecting against advanced threats requires an IT dream team – a well-oiled machine of people and solutions working together to defend your organization. Download our resource kit today to learn more about the tools you need to build you IT Dream Team!


Author Comment

by:E J Pope
ID: 38282921
I'm using PFSense. Can someone give me a bit of a spoon fed help on this? I'm also using dual WAN at one of the locations I'm using PFSense. DSL and Cable.
LVL 23

Expert Comment

ID: 38283111
What happens is there is more data attempting to be transferred than the link can carry.

When a network connection is congested, some packets can be sent at any particular moment, and some packets cannot.

What happens is one of two things:

(1)  Packets that cannot be sent yet are "buffered" or  wait for their turn to be sent out the congested link;   the bigger  the buffer space configured for the links,  the greater the "queue depth"  (number of packets waiting in line)  is allowed to be,  BUT the longer the wait time.

If the wait time is long enough, the sender will not receive an acknowledgement, and may attempt to re-send the packet that is actually just waiting in line,  because they will believe the packet got lost/discarded.

The wait time increase due to buffering increases the latency and reduces the response/performance for every packet that has to wait;  normally there is no 'preference' there, so all packets with similar size have a similar chance of being impacted, and all network activities  are effected by congestion.

(2) Packets that cannot be sent yet are dropped, if they cannot be buffered; beyond a few milliseconds, this is the preferred response.... e.g. too many packets waiting in line, exceeds the buffer space  --  if using TCP, the sender will detect the problem and send/re-send new packets.

It is possible to manage congestion by ensuring that end-to-end the buffers are appropriately small,  and  that you implement prioritization of highly latency-sensitive
traffic using  traffic classification and QoS priority queuing.

However, this only  really works if the traffic you need to prioritize, comfortably
fits within the available link capacity, with sufficient extra headroom for TCP.

Accepted Solution

penguinjas earned 2000 total points
ID: 38283879
I found an article on traffic shaping for your device.  You want to limit the amount of bandwidth any one connection can use.  In Cisco firewall speak you create a policy to limit available bandwidth.


Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

WARNING:   If you follow the instructions here, you will wipe out your VTP and VLAN configurations.  Make sure you have backed up your switch!!! I recently had some issues with a few low-end Cisco routers (RV325) and I opened a case with Cisco TA…
This month, Experts Exchange’s free Course of the Month is focused on CompTIA IT Fundamentals.
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
Michael from AdRem Software outlines event notifications and Automatic Corrective Actions in network monitoring. Automatic Corrective Actions are scripts, which can automatically run upon discovery of a certain undesirable condition in your network.…

579 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question