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Python tools for TWAMP and TWAMP light

Twampy is a Python implementation of the Two-Way Active Measurement Protocol (TWAMP and TWAMP light) as defined in RFC5357. This tool was developed to validate the Nokia SR OS TWAMP implementation.

Supported features

  • unauthenticated mode
  • IPv4 and IPv6
  • Support for DSCP, Padding, JumboFrames, IMIX
  • Support to set DF flag (don't fragment)
  • Basic Delay, Jitter, Loss statistics (jitter according to RFC1889)

Modes of operation

  • TWAMP Controller
  • TWAMP Control Client
  • TWAMP Test Session Sender
  • TWAMP light Reflector

Installation

$ git clone https://github.com/nokia/twampy
Cloning into 'twampy'...

Usage Notes

Use padding to configure bidirectional packet/frame sizes:

IP Version Padding Packet Size Frame Size
IPv4 >=27 Padding+42 Padding+56
IPv6 >=27 Padding+62 Padding+76

Padding default is 27 bytes (to enforce bidirectional behavior).

Use padding value '-1' for IMIX traffic generation:

L2 Size Packets Ratio(Packets) Ratio(Volume)
64 7 58% 10%
590 4 33% 55%
1514 1 8% 35%

TOS/DSCP user settings neet to be enabled on WINDOWS:

  1. Open Registry Editor
  2. Go to key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TcpIp\Parameters
  3. Create new DWORD value:
EntryName Value
DisableUserTOSSetting 0x00000000 (0)

  1. Quit Registry Editor

  2. Restart you computer

  3. Command prompt for validation (capture needed)

    $ ping -v 8

Reference: http://support.microsoft.com/kb/248611

DF flag implementation supports Linux und Windows. To support other Operating Systems such as OS X (darwin) or FreeBSD the according code such as sockopts need to be added and validated.

Possible Improvements

  • authenticated and encrypted mode
  • sending intervals variation
  • enhanced statistics
    • bining and interim statistics
    • late arrived packets
    • smokeping like graphics
    • median on latency
    • improved jitter (rfc3393, statistical variance formula): jitter:=sqrt(SumOf((D[i]-average(D))^2)/ReceivedProbesCount)
  • daemon mode: NETCONF/YANG controlled, ...
  • enhanced failure handling (catch exceptions)
  • per probe time-out for statistics (late arrival)
  • Validation with other operating systems (such as FreeBSD)
  • Support for RFC 5938 Individual Session Control
  • Support for RFC 6038 Reflect Octets Symmetrical Size

Error codes (as per RFC 4656)

Error Code Description
0 OK
1 Failure, reason unspecified (catch-all).
2 Internal error.
3 Some aspect of request is not supported.
4 Cannot perform request due to permanent resource limitations.
5 Cannot perform request due to temporary resource limitations.

Usage example: getting help

Help on modes of operation:

$ ./twampy.py --help
usage: twampy.py [-h] [-v]
                 {responder,sender,controller,controlclient,dscptable} ...

positional arguments:
  {responder,sender,controller,controlclient,dscptable}
                        twampy sub-commands
    responder           TWL responder
    sender              TWL sender
    controller          TWAMP controller
    controlclient       TWAMP control client
    dscptable           print DSCP table

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         show program's version number and exit

Specific help:

$ ./twampy.py sender --help
usage: twampy.py sender [-h] [-l filename] [-q | -v | -d]
                        [--tos type-of-service] [--dscp dscp-value]
                        [--ttl time-to-live] [--padding bytes]
                        [--do-not-fragment] [-i msec] [-c packets]
                        [remote-ip:port] [local-ip:port]

optional arguments:
  -h, --help            show this help message and exit
  -q, --quiet           disable logging
  -v, --verbose         enhanced logging
  -d, --debug           extensive logging

Debug Options:
  -l filename, --logfile filename
                        Specify the logfile (default: <stdout>)

IP socket options:
  --tos type-of-service        IP TOS value
  --dscp dscp-value            IP DSCP value
  --ttl time-to-live           [1..128]
  --padding bytes              IP/UDP mtu value
  --do-not-fragment            keyword (do-not-fragment)

TWL sender options:
  remote-ip:port
  local-ip:port
  -i msec, --interval msec     [100,1000]
  -c packets, --count packets  [1..9999]

Usage example against SR OS TWAMP server

Router configuration:

A:VSR# configure test-oam
A:VSR>config>test-oam># info
----------------------------------------------
        twamp
            server
                prefix 0.0.0.0/0 create
                exit
                no shutdown
            exit
        exit
----------------------------------------------

Running the test:

$ ./twampy.py controller 192.168.255.2
===============================================================================
Direction         Min         Max         Avg          Jitter     Loss
-------------------------------------------------------------------------------
  Outbound:       92.89ms    196.63ms     95.15ms       576us      0.0%
  Inbound:            0us         0us         0us         0us      0.0%
  Roundtrip:        339us    103.53ms      1.91ms       638us      0.0%
-------------------------------------------------------------------------------
                                                    Jitter Algorithm [RFC1889]
===============================================================================