Hot answers tagged

9 votes
Accepted

iperf: send specific volume?

The -l option is for the buffer and doesn't influence the amount of data transferred. You have to specify the desired amount of data with the client-only option -n in KByte or MByte. So for 10GB, ...
user avatar
  • 18.3k
6 votes

VOIP testing with IPERF tool

I think you're confused about what Iperf is, and what purpose it serves. From the Iperf Man Page: iperf is a tool for performing network throughput measurements. It can test either TCP or UDP ...
user avatar
  • 8,248
5 votes
Accepted

GNS3: performance tests using iperf3?

Don't trust GNS3 for throughput tests. As soon as you use a router in your topology you are likely only to get 5mb/sec tops, regardless of whether you use a serial, ethernet or fast ethernet interface ...
user avatar
  • 2,317
5 votes

VOIP testing with IPERF tool

iperf can be used to test transportation protocols like TCP and UDP. VOIP is an application protocol. This is another layer of the Internet Procol Suite. So the answer is: no, you cannot test VOIP, ...
user avatar
  • 15.6k
4 votes
Accepted

Iperf results on Bandwidth and Transfer do not make sense

The Raspberry Pi 1,2 and zero have a 100Mb/s network interface card, so this is likely what caps the traffic. (the raspberry pi 3 has a gigabit Ethernet interface but it is connected to the processor ...
user avatar
  • 18.3k
3 votes

Tuning UDP-lite protocol instead of UDP with "IPERF" tool

You can use patched IPERF compile, and then run: # iperf -s --udplite 0 ------------------------------------------------------------ Server listening on UDP-Lite port 5001 Receiving 1470 byte ...
user avatar
  • 700
3 votes
Accepted

Collect UDP packets lost during iPerf test

Depending on your Cacti version, we collect errors and discarded packets without any problems on Version 1.1.38. Here's how we do it. Select the tab Console, then extend Management and click devices....
user avatar
  • 1,701
3 votes
Accepted

Why I cannot see packet loss on GRE over capacity tunnels?

The bandwidth command sets the reported bandwidth and is used for metric calculation only. It does not affect the actual interface bandwidth. If you want to limit bandwidth, you will need to ...
user avatar
  • 62k
3 votes
Accepted

cisco catalyst 3560 rate-limit on vlan is not observable with iperf

If both devices are connected to VLAN 1, then that command has no effect. That command would be for traffic leaving the interface, but if both devices are on that VLAN, the traffic never leaves the ...
user avatar
  • 92.8k
3 votes
Accepted

IPoIB with Netem (Latency emulation) Poor performance

The most common mistake made when using netem to emulate network delay is to not increase the packet limit. You didn't. Therefore you tail drop a lot of packets and tcp cannot build a queue long ...
user avatar
3 votes

Lower throughput with fixed TCP window size?

That's not a shock. These day we automatically tune the amount of RAM assigned to TCP buffers (aka the maximum TCP window size), and by specifying the window size you are turning off the automated ...
user avatar
  • 1,161
3 votes

Lower throughput with fixed TCP window size?

As Marco mentioned, Receive window sizes (rwin) will increase and decrease automatically during a TCP session depending on how lossy the connection ends up being. It is therefore possible that ...
user avatar
  • 2,317
3 votes

Lower throughput with fixed TCP window size?

Receive window sizes (rwin) will increase and decrease automatically during a TCP session depending on how lossy the connection ends up being. It is therefore possible that when you omit the -w flag ...
user avatar
3 votes
Accepted

Where are UDP packets lost during iPerf test?

When more traffic than a link can handle is sent to a link, the interface to that link will end up dropping the packets destined for that link. This is congestion, and there are some small mitigations ...
user avatar
  • 92.8k
3 votes

Iperf 'set bandwidth' command issues

I'm inclined to believe that it is your caps/non-caps on the bandwidth designations (i.e. -b 10M -l 32K -w 128K). I can't test it because we don't know what version you're running. Iperf does make a ...
user avatar
  • 5,449
3 votes
Accepted

Iperf results on UDP Bandwidth

There is one particularity about iperf 2.0.x with UDP: Within the limits (CPU, NIC, UDP/IP stack and its buffers) of the sending system, iPerf will send traffic at the payload rate you specify with ...
user avatar
3 votes

Bandwidth, Latency, Download speed and Upload speed

iperf measures bandwidth. Tools like Ookla Speedtest report download and upload speed. "Speed" is a term that's often misused. All these tools measure throughput -- the amount of data sent ...
user avatar
  • 62k
2 votes
Accepted

Calculating the Jain Fairness Index of two connections - what values to use?

Yes, a set of equal values will give a Jain of 1. Your values are extremely similar, I calculated 0.999971.
user avatar
  • 15.9k
2 votes
Accepted

There's huge gap between two results for iperf

Welcome to the downside of cloud computing! Jitter (latency variability) and aggressive oversubscription. Your node is competing for shared resources at many different points that can be greatly ...
user avatar
2 votes

VOIP testing with IPERF tool

Like user27884 said, you could configure Iperf server in this way: iperf -s -u -p 5061 -S 0xC0 -l 200 ..and the iperf client like this: iperf -c 127.0.0.1 -u -p 5061 -S 0xC0 -l 200 -t 200 -b 200k -...
user avatar
2 votes

WiFi TCP iperf throughput: upstream vs down stream

While passing downlink traffic (from the Access Point (AP)) to client-nodes, the AP schedules the packets from the packet-queues in the appropriate way and also does not face any contention on the ...
user avatar
  • 56
2 votes

IPERF TCP vs UDP

TCP uses SLOW START to maximize bandwidth and minimize lost packets, so it adapts to the slowest link in the chain by waiting for acks to come back. UDP leaves it to the application layer, and iperf ...
user avatar
2 votes
Accepted

IPERF TCP vs UDP

What does iperf UDP streams do iperf will attempt to send UDP packets to reach the rate given in --bandwidth. If that parameter is missing, it will attempt to achieve the rate of the transmitting ...
user avatar
  • 1,161
2 votes
Accepted

Definition of bandwidth capacity for an internet connection

There are two aspects for bandwidth: The link speed as indicated by the interface presents the upper limit of what that interface can transport. The practical throughput (maximum capacity) you can ...
user avatar
  • 69.5k
2 votes

How can I find bottlenecks using IPERF3?

iperf can help you generate flows of a certain bandwidth. You can then check if your network behaves as designed and examine your equipment for signs of problems: packet drops due to exceeding ...
user avatar
  • 69.5k
2 votes
Accepted

Understanding Throughput of interfaces problem on Cisco Routers

Cisco CSR does not have support for SR on AWS, see here for AWS requirements/support. There is no support for SR as in SR-IOV "single root virtualization", there is support for SR as in segment ...
user avatar
1 vote
Accepted

iperf without TCP server

Hi and welcome to network engineering! iPerf 1.7.x and iPerf 2.0.x run well in an UDP-only mode. Use the -u parameter on both server (usually: receiver) and client (usually: sender) side. iPerf 3.x....
user avatar
1 vote
Accepted

TCP cwnd is increasing when congestion occur

I found an answer. It is not weird behavior. I'm just short in understanding. Before the congestion occur, the transmitted packets are queuing in the switch buffer. As the number of packets in the ...
user avatar
  • 25
1 vote
Accepted

Why is there a difference on the amount of data transferred during a UDP iperf measurement?

Here's a iperf3 client RaspberryPi3B running current Raspbian to a iperf3 server MacbookPro8,2 running current Fedora 29 x86_64, across a cheap DLink DGS-1005A gigabit ethernet switch, same parameters ...
user avatar
  • 1,161
1 vote

How to verify that the connection is 10G?

That could be issue with Window Auto-Tuning which is implemented in windows. Due to default settings size of window never will be bigger than 256 KB. To switch off Windows Auto-Tuning you need to ...
user avatar

Only top scored, non community-wiki answers of a minimum length are eligible