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HP Recommended

In the columns Average Packets Lost (Tx) and (Rx), what is the equation that calculates this value?  I want a total number and there is none.

 

For example, we had a unit connected for 1:14:17.  It reports the Average Packeta Lost (Rx) as 6746.5.  The total was well over 13,000.  Another call was for 00:02:17 with a packet loss (Rx) of 230 packets total but the average is 71.  I can't seem to figure out what the formula is for this "average."  Usually it is a division over a unit of time, but I don't see what that unit is because the first could be dividing by 2 but the second is dividing by 3.25. 

 

I need a difinitive answer because we are trying to diagnose a packet loss issue to determine where the loss occurs using packet sniffers to keep count between points on the network.c

14 REPLIES 14
HP Recommended

I don't know why this value was called "Average" but HDX Admin's Guide defines "Average Packets Lost (Rx)" as "The number of packets from the far site that were lost during an H.323 call". According to this definition the term "Total" seems to be more adequate.

 

In my practice I prefer to look at "Average Percent of Packet Loss (Tx/Rx)" values.

HP Recommended

Hi lucasaj,

Logic is Here 

 

RX= Received packet ,

TX=Transmitted Packet,

Total =  RX+TX  = VC CALL

RX AND TX BOTH Are Different Thing 

Loss And Lost BOTH Are Different Thing

1. Duration   =  VC Call Duration

2. Average Percent Packet Loss (Rx)   = average % of packet LOSS during Receiving Far End Side Video       

3. Average Packets Lost (Rx) =  Average of total LOST packet during Receiving Far End Side Video           

4. Average Percent Packet Loss (Tx)   = average % of packet LOSS during Sending Near End Side Video

5. Average Packets Lost (Tx) =  Average of total LOST packet during Sending Near End Side Video

 

In Your 2nd Case

230 =  Average Packets Lost (Rx)

71 = Average Percent Packet Loss (Rx)

 

In Simple Word

Because Of (Average Percent Packet Loss (Rx)) is = 71 % 

That's Why you have 230 (Average Packets Lost (Rx)) In very short Duration 

 

 

ASK ME AGAIN IF ANY DOUBT

 

HP Recommended

First, I know the difference between transmit (Tx) and receive (Rx).  Please actually read my question before you decide to talk down to me and explain stuff that I actually know.

 

Lets review what I said.  Apparently I have to break it down for you to understand my question better:

"In the columns Average Packets Lost (Tx) and (Rx), what is the equation that calculates this value?  I want a total number and there is none."

 

So, Here I am referring to the TWO columns (note the plural) , which I apparently have to type out fully, called Average Packets Lost (Tx) and Average Packets lost (Rx).  What is the equation that is being used to come up with these values?

 

For example, we had a unit connected for 1:14:17.  It reports the Average Packets Lost (Rx) as 6746.5.  The total was well over 13,000.  Another call was for 00:02:17 with a packet loss (Rx) of 230 packets total but the average is 71.  I can't seem to figure out what the formula is for this "average."  Usually it is a division over a unit of time, but I don't see what that unit is because the first could be dividing by 2 but the second is dividing by 3.25. 

 

I guess I have to spell this out better.  I will be referring to the CDR (that is the Call Detail Report) under Utilities and the Call Statistics page under Diagnostics on the web interface for an HDX unit.  Funny thing, there is a difference between TOTAL and AVERAGE.  There is no TOTAL in the CDR.  Keep in mind, I am not looking for a percentage lost which is why it was never mentioned it so I don't know where you got 71% loss when I said the average packets lost was 71 (in the CDR) of the 230 total packets lost reported on the Call Statistics page.  Apparently I cannot talk in present tense (loss) verses past tense (lost).

 

So here it is again:

 

Example 1:

Conference length: 1:14:17

 

Call Statistics:

Total Packets Lost (Rx):  Around 13300 (I lost the actual total because I glanced away for 1 second and the conference connection ended)

 

CDR:

Average Packets Lost (Rx):  6746.5

 

This average is roughly 1/2.

 

Example 2:

Conference Length:  00:02:17

 

Call Statistics:

Total Packets Lost (Rx):  230

 

CDR:

Average Packets Lost (Rx):  71

 

This average is roughly 1/3. 

 

Do you see the discrepancies??  What is the formula?  In the first example it seems to have been divided by 2 and the second one was actually divided 3.25.

 

Here is our issue.  We are experiencing packet loss to certain units.  We are trying to determine where this loss is happening along our network.  We have set up packet sniffers to count the number of packets along the path from our RMX to one of the units experiencing the loss.  I need the total packets lost so I can compare the data (and make sure that the laptops running Wireshark are not dropping the packets also).  I cannot sit there staring at the Call Statistics page and control 3 to 4 instances of Wireshark.  I would like to work backwards with the formula to get the total packets lost.
HP Recommended

Without discussing about the Polycom formulas for packet lost let me say two words about the issue itself.

 

1. For searching the problem point along the network I could recommend you to use an utility like PingPlotter (www.pingplotter.com). This tool gives a real time plot of the network status. Attachment shows an example.

 

2. Diagnostics of very high level of real time packet lost (25 to 50 percents) may be caused by the presence of parallel routes what leads to the packet reordering. In this case the standard methods (pingplotter including) might be unuseful.

HP Recommended

Never did I say that we had 25% to 50% packet loss.  We don't have a dual router setup yet, but when we do, it would load balance by site instead of just splitting up packets evenly between routers.

 

Ping Plotter will not help.  I can trace route and pathping just fine.  We have used iperf to flood the line with UDP traffic to simulate the traffic and lose nothing.  We are experiencing packet loss between point A to B.  In between Point A (oour RMX) and Point B (our remote site) is a router, a 50Mbps connection to our MPLS cloud, and a Quad T1 line connection from the MPLS cloud to our remote site.  We are trying to figure out where the thousnads of packets are being lost.  Is it the router (my suspicion), the telco connection (our network sysadmins supicion and the telco's denial), or the RMX itself (which no one suspects because we have no packet loss at this location)?  I need to have the total packets lost value because we are counting packets with Wireshark that go out of the RMX, out of the router, and into the HDX unit on the other side.  I cannot control several instances of Wireshark and pay attention to grab the total packets lost from the call stats on the remote HDX unit's web interface for that last second it is on the page at the end of the call before it disappears.

HP Recommended

By my mind "a Quad T1 line connection" is a key word. Try to disable three lines and test the result with the last one.

HP Recommended

Hi lucasaj,

 

Let's take Example 2:

 

1.According Call Statistics page      Total Lost RX is 230 

2.According Call Detail Report         Average Packets Lost (Rx):  71.5

3.Conference length                          00:02:17                                 

 

in Call Static Page You See Real Time Total Number of packet lost.

in Call Detail Report You see Complicated Calculated Data * mention below 

Two Factor 

Duration 

Packet Loss 

 

Try to Understand backend Process.

1. start a call with 0% packet Loss                                                                                         =    0 Packet Lost (in Call Statistics page )

2. during call You have facing network Issue with 1% Packet Loss for 10 sec              =    100 Packet Lost (in Call Statistics page )

3. after 10 sec network Stable then 0% Packet Loss                                                           =    100 at 0% packet loss Nothing will increase  (in Call Statistics page )

4. during call You have facing network Issue again with 2Packet Loss for 7 sec      =   240 Packet Lost (100+140)(in Call Statistics page )

5. after 10 sec network Stable then 0Packet Loss                                                           =   240 it will not increase bcoz of presently network is stable (in Call Statistics page )

6. call disconnect.                                                                                                                       =   240 Total Packet Lost (in Call Statistics page )

 

In CDR here Duration mattars. Because here is value in Average.It can be 71 or 50 or 95 now its totally upon on duration.  

 

you see in (Call Statistics page ) = Total No. of Packet Lost 

You see in (Call Detail Page )      = Average Packets Lost

 

if it's clear then we will start for some more Discussion.

For Solution ?

 

 

Give me Kudos if you don't Mind

 

HP Recommended

Wow.  I think I know how the packets are being added up.  I took math classes up through Calculus.

 

Can someone please give me the unit of time, ex: 1 min, 5 min, 30, min, 1 hour, etc that is used to calculate the average???

 

Usually the formula for an average looks like this:

(average packets lost) = (total packets lost)/(unit of time)

 

That is how average is found.  What is that unit of time that is being used to find the average?

HP Recommended

It is not the T1 lines.  Besides, we have no control over turning them on and off.  That is unfortunately under the control of the telco and they refuse to give us the passwords to the Adtrans.  It takes 24 hours or more to get them to turn off a T1 line.

 

We found where some of the packet loss was happening.  We watched the number of packets enter the router and the number that left and the number that left were higher then the ones that entered.  The router's MTU was set lower than the RMX's default 1500.  So the Router was slicing the packets up.  Once we changed the router to match the rest of the network and telco's defaults of 1500, we were seeing much less loss, but we are still experiencing loss.  We might play with reducing the MTU size on the HDX and RMX units next week, but we still need to have the total number of packets lost instead of the so called average so we can track where we are dropping packets.

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