TRex Frequently Asked Questions
================================
:author: TRex team
:email: trex.tgen@gmail.com 
:revnumber: 0.2
:quotes.++:
:numbered:
:web_server_url: http://trex-tgn.cisco.com/trex
:local_web_server_url: csi-wiki-01:8181/trex
:github_stl_path: https://github.com/cisco-system-traffic-generator/trex-core/tree/master/scripts/stl
:github_stl_examples_path: https://github.com/cisco-system-traffic-generator/trex-core/tree/master/scripts/automation/trex_control_plane/stl/examples
:toclevels: 6

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== FAQ

===  General 

==== What is TRex?
TRex is fast realistic open source traffic generation tool, running on standard Intel processors, based on DPDK. It supports both stateful and stateless traffic generation modes.

==== What are the common use cases for TRex?
1. High scale benchmarks for stateful networking gear. For example: Firewall/NAT/DPI.
2. Generating high scale DDOS attacks. See link:https://www.incapsula.com/blog/trex-traffic-generator-software.html[Why TRex is Our Choice of Traffic Generator Software]
3. High scale, flexible testing for switchs (e.g. RFC2544)- see link:https://wiki.fd.io/view/CSIT[fd.io]
4. Scale tests for huge numbers of clients/servers for controller based testing.
5. EDVT and production tests.

[NOTE]
=====================================
Features terminating TCP can't be tested yet.
=====================================

==== Who uses TRex?

Cisco systems, Intel, Imperva, Melanox, Vasona networks and much more.

==== What are the Stateful and Stateless modes of operation?

'Stateful' mode is meant for testing networking gear which save state per flow (5 tuple). Usually, this is done by injecting pre recorded cap files on pairs of interfaces of the device under test, changing src/dst IP/port. 
'Stateless' mode is meant to test networking gear, not saving state per flow (doing the decision on per packet bases). This is usually done by injecting customed packet streams to the device under test.
See link:trex_stateless.html#_stateful_vs_stateless[here] for more details.

==== Can TRex run on an hypervisor with virtual NICS?

Yes. Currently there is a need for 2-3 cores and 4GB memory. For VM use case, memory requirement can be significantly reduced if needed (at the cost of supporting less concurrent flows)
by using the following link:trex_manual.html#_memory_section_configuration[configuration]

Limitations:

1. Performance is limited. For each NIC port pair, you can utilize only one CPU core.
2. Using vSwitch will limit the maximum PPS to around 1MPPS.
3. Latency results will not be accurate.
          
==== Why not all DPDK supported NICs supported by TRex?
1. We are using specific NIC features. Not all the NICs have the capabilities we need.
2. We have regression tests in our lab for each recommended NIC. We don't claim to support NICs we don't have in our lab.

==== Is Cisco VIC supported?
No. Currently its DPDK driver does not support the capabilities needed to run TRex.

==== Is 100Gbs NIC QSFP+ supported?
Not yet. Support for FM10K and Mellanox Connectx5 is under development.

==== Is there a GUI?
TRex team is not developing it. Have a look link:https://groups.google.com/forum/#!searchin/trex-tgn/sari%7Csort:relevance/trex-tgn/R92-N2Yjy2Q/DIUe06YCBgAJ[here] for TRex Stateless mode GUI from Exalt company.

==== What is the maximum number of ports per TRex application?
12 ports

==== I can not see all 12 ports statistics on TRex server .
We present statistics only for first four ports because there is no console space. Global statistics (like total TX) is correct, taking into account all ports.
You can use the GUI/console or Python API, to see statistics for all ports.

==== Can I run multiple TRex servers on the same machine?
One option for running few instances on the same physical machine is to install few VMs.
Currently, it is complicated to do without using VMs (but possible with some advanced config file options). We are working on
a solution to make this easier.

==== Can I use multiple types of ports with the same TRex server instance?
No. All ports in the configuration file should be of the same NIC type.

==== What is better, running TRex on VM with PCI pass through or TRex on bare metal?
The answer depends on your budget and needs. Bare metal will have lower latency and better performance. VM has the advantages you normally get when using VMs.

==== I want to report an issue.

You have two options: +
1. Send email to our support group: trex.tgen@gmail.com +
2. Open a defect at our link:https://trex-tgn.cisco.com/youtrack[youtrack]. You can also influence by voting in youtrack for an
existing issue. Issues with lots of voters will probably be fixed sooner.


==== I have Intel X710 NIC with 4x10Gb/sec ports and I can not get line rate.
x710da4fh with 4 10G ports can reach a maximum of 40MPPS (total for all ports) with 64 bytes packets. (can not reach the theoretical 60MPPS limit).
This is still better than the Intel x520 (82559 based) which can reach ~30MPPS for two ports with one NIC.

==== I have XL710 NIC with 2x40Gb/sec ports and I can not get line rate
XL710-da2 with 2 40G ports can reach maximum of 40MPPS/50Gb (total for all ports) and not 60MPPS with small packets (64B)
Intel had in mind redundancy use case when they produced a two port NIC. Card was not intended to reach 80G line rate.

==== I want to contribute to the project
You have several ways you can help: +
1. Download the product, use it, and report issues (If no issues, we will be very happy to also hear success stories). +
2. If you use the product and have improvment suggestions (for the product or documentation) we will be happy to hear. +
3. If you fix a bug, or develop new feature, you are more than welcome to create pool request in GitHub.

==== What is the release process? How do I know when a new release is available?
It is a continuous integration. The latest internal version is under 24/7 regression on few setups in our lab. Once we have enough content we release it to GitHub (Usually every few weeks).
We don't send an email for every new release, as it could be too frequent for some people. We announce big feature releases on the mailing list. You can always check the GitHub of course.

===  Startup and Installation

==== Can I experiment with TRex without installing?
You can. Check the TRex sandbox at Cisco devnet in the following link:https://devnetsandbox.cisco.com/RM/Diagram/Index/2ec5952d-8bc5-4096-b327-c294acd9512d?diagramType=Topology[link].

==== How do I obtain TRex, and what kind of hardware do I need?
You have several options. +
1. For playing around and experimenting, you can install TRex on VirtualBox by following this link:trex_vm_manual.html[link]. +
2. To run the real product, check link:trex_manual.html#_download_and_installation[here] for hardware recommendation and
installation instructions.

==== During OS installation, screen is skewed / error "out of range" / resolution not supported etc

        * Fedora - during installation, choose "Troubleshooting" -> Install in basic graphic mode
        * Ubuntu - try Ubuntu server, which has textual installation

==== How to determine relation between TRex ports and device under test ports

Run the TRex with following command and check incoming packet on router interfaces:

[source,bash]
----
        sudo ./t-rex-64 -f cap2/dns.yaml --lm 1 --lo -l 1000 -d 100
----

==== How to determine relation between Virtual OS ports and Hypervisor ports

Compare the MACs address + name of interface, for example:

[source,bash]
----
* > ifconfig +
*eth0*    Link encap:Ethernet  *HWaddr 00:0c:29:2a:99:b2* +
          ...

* > sudo ./dpdk_setup_ports.py -s +
*03:00.0* 'VMXNET3 Ethernet Controller' *if=eth0* drv=vmxnet3 unused=igb_uio
----

[NOTE]
=====================================
If at TRex side the NICs are not visible to ifconfig, run: +
....
sudo ./dpdk_nic_bind.py -b <driver name> <1> <PCI address> <2>
....

<1> driver name - vmxnet3 for VMXNET3 and e1000 for E1000
<2> 03:00.0 for example

We are planning to add MACs to `./dpdk_setup_ports.py -s`
=====================================

==== TRex traffic does not show up on Wireshark, so I can not capture the traffic from the TRex port
TRex uses DPDK which takes ownership of the ports, so using Wireshark is not possible. You can use switch with port mirroring to capture the traffic.

==== How can I map betwean TRex port-id (e.g. port 0) and physical router interface?
Load TRex in stateless mode, run traffic from each port, and look at the counters on the router interfaces.


===  Stateful 

==== How do I start using the stateful mode?
You should first have a YAML configuration file. See link:trex_manual.html#_traffic_yaml_parameter_of_f_option[here].
Then, you can find some basic examples link:trex_manual.html#_trex_command_line[here].

==== TRex is connected to a switch and we observe many dropped packets at TRex startup.
A switch might be configured with spanning tree enabled. TRex initializes the port at startup, making the spanning tree drop the packets. 
Disabling spanning tree can help. On Cisco nexus, you can do that using `spanning-tree port type edge`
This issue would be fixed when we consolidate 'Stateful' and 'Stateless' RPC.

==== I can not see RX packets
TRex does not support ARP yet, you should configure the DUT to send the packets to the TRex port MAC address. From Stateless mode, you can change the port mode to promiscuous. +
Also, revisit your MAC address configuration in the TRex config file. Wrong MAC address configuration will cause all packets to be dropped.

==== Why is the performance low?

TRex performance depends on many factors:

1. Make sure trex_cfg.yaml is optimal see "platform" section in manual 
2. More concurrent flows will reduce the performance 
3. Short flows with one/two packets (e.g. cap2/dns.yaml ) will give the worst performance 

==== Is there a plan to add TCP stack?
Yes. We know this is something many people would like, and are working on this. No ETA yet. Once a progress is made, we will announce it on the TRex site and mailing list.

==== How can I run the YAML profile and capture the results to a pcap file?
You can use the simulator. see link:trex_manual.html#_simulator[simulator]
The output of the simulator can be loaded to Excel. The CPS can be tuned.

==== I want to have more active flows on the DUT, how can I do it?
After stretching TRex to its maximum CPS capacity, consider the following: DUT will have much more active flows in case of a UDP flow due to the nature of aging (DUT does not know when the flow ends while TRex knows).
In order to artificialy increse the length of the active flows in TRex, you can config larger IPG in the YAML file. This will cause each flow to last longer. Alternatively, you can increase IPG in your PCAP file as well.


==== How do I support more active flows?
The default maximum supported flows are 1M total (TRex prospective). DUT could have much more due to aging. When active flows are more than 1M flows there is message that there is no enough memory. 

[source,Python]
--------
Active-flows    :  1045562  Clients :    80120   Socket-util : 0.0207 %
--------

Look link:trex_manual.html#_memory_section_configuration[here]

This example support 10M flows 

[source,Python]
--------
- port_limit    : 2
  version       : 2
  interfaces    : ['04:00.0', '0c:00.0']   # list of the interfaces to bind run ./dpdk_nic_bind.py --status 
  port_info       :  # set eh mac addr 

          - dest_mac        :   [0x18, 0x8b, 0x9d, 0xa3, 0xae, 0x84]
            src_mac         :   [0x18, 0x8b, 0x9d, 0xa3, 0xae, 0x83]
            
          - dest_mac        :   [0x18, 0x8b, 0x9d, 0xa3, 0xae, 0x83]
            src_mac         :   [0x18, 0x8b, 0x9d, 0xa3, 0xae, 0x84]

  memory    :                                          
        dp_flows    : 10048576   <1>
--------
<1> 10M flows


==== ERROR The number of ips should be at least number of threads 
The range of clients and servers should be at least the number of threads. 
The number of threads is equal (dual_ports) * (-c value)

==== Incoming frames are from type SCTP why?
Default latency packets are SCTP, you can remove `-l 1000` or change it to ICMP see manual for more info 
 

===  Stateless 

==== How do I get started with stateless mode?
You should first have a YAML configuration file. See link:trex_manual.html#_traffic_yaml_parameter_of_f_option[here].
Then, you can have a look at the stateless manual link:trex_stateless.html[here]. You can jump right into the link:trex_stateless.html#_tutorials[tutorials section].

==== Is pyATS supported as client framework 

Yes. Both Python 3 and Python 2

==== Python API does not work on my Mac with the below ZMQ library issue 

We are using Python ZMQ wrapper. It needs to be compiled per platform and we have a support for many platforms but not all of them.
You will need to build ZMQ for your platform if it is not part of the package.

[source,Python]
----
    from .trex_stl_client import STLClient, LoggerApi
  File "../trex_stl_lib/trex_stl_client.py", line 7, in <module>
    from .trex_stl_jsonrpc_client import JsonRpcClient, BatchMessage
  File "../trex_stl_lib/trex_stl_jsonrpc_client.py", line 3, in <module>
    import zmq
  File "/home/shilwu/trex_client/external_libs/pyzmq-14.5.0/python2/fedora18/64bit/zmq/__init__.py", line 32, in <module>
    _libzmq = ctypes.CDLL(bundled[0], mode=ctypes.RTLD_GLOBAL)
  File "/usr/local/lib/python2.7/ctypes/__init__.py", line 365, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: /lib64/libc.so.6: version `GLIBC_2.14' not found (required by /home/shilwu/trex_client/external_libs/pyzmq-14.5.0/python2/fedora18/64bit/zmq/libzmq.so.3)
 
----


==== Is multi-user supported

Yes. Multiple TRex clients can connect to the same TRex server.

==== Can I create a corrupted packets?

Yes. You can build any packet you like using Scapy. 
However, there is no way to create corrupted L1 fields (Like Ethernet FCS), since these are usually handled by the NIC hardware.

==== Why the performance is low?
What would reduce the performance: 

1. Many concurent streams.
2. Complex field engine program.

Adding 'cache' directive can improve the performance. See link:trex_stateless.html#_tutorial_field_engine_significantly_improve_performance[here]

and try this:

[source,bash]
----
$start -f stl/udp_1pkt_src_ip_split.py -m 100% 
----

[source,python]
----

 vm = STLScVmRaw( [   STLVmFlowVar ( "ip_src",
                                            min_value="10.0.0.1",
                                            max_value="10.0.0.255",
                                            size=4, step=1,op="inc"),

                             STLVmWrFlowVar (fv_name="ip_src",
                                             pkt_offset= "IP.src" ),

                             STLVmFixIpv4(offset = "IP")
                         ],
                         split_by_field = "ip_src",
                         cache_size =255 # the cache size             <1>
                        );
----
<1> cache 


==== I want to generate gratuitous ARP/NS IPv6.

See example link:trex_stateless.html#_tutorial_field_engine_many_clients_with_arp[here]

==== How do I create a deterministic random stream variable

use `random_seed` per stream   

[source,python]
----
        return STLStream(packet = pkt,
                         random_seed = 0x1234,
                         mode = STLTXCont())
----

==== Can I have a synconization betwean different stream variables?

No. each stream has it own, seperate field engine program 


==== Is there a plan to have LUAJit as a field engine program?

It is a great idea to add it, we are looking for someone to contribute this support.


==== Streams with latency enabled do not get amplified by multiplier, why?

Reason for this (besides being a CPU constrained feature) is that most of the time, the use case is that you load the DUT using some traffic streams, and check latency
using different streams. The latency stream is kind of 'testing probe' which you want to keep at constant rate, while playing with the rate of your other (loading) streams.
So, you can use the multiplier to amplify your main traffic, without changing your 'testing probe'.
If you do want to amplify latency streams, you can do this using 'tunables'.
You can add in the Python profile a 'tunable' which will specify the latency stream rate and you can provide it to the 'start' command in the console or in the API.
Tunables can be added through the console using 'start ... -t latency_rate=XXXXX'
or using the Python API directly (for automation):
STLProfile.load_py(..., latency_rate = XXXXX)
You can see example for defining and using tunables link:trex_stateless.html#_tutorial_advanced_traffic_profile[here].

==== Latency and statistic per stream is not supported for all types of packets.

Correct. We use NIC capabilities for counting the packets or directing them to be handled by software. Each NIC has its own capabilities. Look link:trex_stateless.html#_tutorial_per_stream_statistics[here] and link:/trex_stateless.html#_tutorial_per_stream_latency_jitter_packet_errors[here] for details.

==== Java API instead of Python API 

Q:: I want to use the Python API via Java (with Jython), apparently, I can not import Scapy modules with Jython.
The way I see it I have two options:

1. Creating python scripts and call them from java (with ProcessBuilder for example)
2. Call directly to the Trex server over RPC from Java

However, option 2 seems like a re-writing the API for Java (which I am not going to do)
On the other hand, with option 1, once the script is done, the client object destroyed and I cannot use it anymore in my tests.

Any ideas on what is the best way to use Trex within JAVA?

A:: 

The power of our Python API is the scapy integration for simple building of the packets and the field engine.
There is a proxy over RPC that you can extend to your use cases. It has basic functionality, like connect/start/stop/get_stats.
You could use it to send some pcap file via ports, or so-called python profiles, which you can configure by passing different variables (so-called tunabels) via the RPC.
Take a look at link:trex_stateless.html#_using_stateless_client_via_json_rpc[using_stateless_client_via_json_rpc].
You can even dump the profile as a string and move it to the proxy to run it (Notice that it is a potential security hole, as you allow outside content to run as root on the TRex server).

See link:https://github.com/zverevalexei/trex-http-proxy[here] an example for simple Web server proxy for interacting with TRex.

==== Where can I find a reference to RFC2544 using TRex

link:https://gerrit.fd.io/r/gitweb?p=csit.git;a=tree;f=resources;hb=HEAD[here]



