Does trex has option to set TCP window scaling

[Rashi Krishna]

Hi All,

Does trex has option to set TCP window scaling? I checked the documentation for ASTF, I found tcp.initwnd, not sure if it is the same thing.

https://www.geeksforgeeks.org/what-is-tcp-window-scaling/

[hanoh haim]

Hi, 

You can set the CC and maximum window size, the TCP stack will handle the right value in tcp scaling 

[Rashi Krishna]

Hi Hanoch,

Thanks for your reply!
Actually for our use case we want to manually set window scaling value.
Do you know how exactly the tcp stack calculates the window scaling based on the initial window value?
Then we can set the initial window to get the window scale we want.

Thanks !

Rashi

[hanoh haim]

Hi Rashi, 

You can set initwnd 

Thanks

Hanoh

[Rashi Krishna]

Hey Hanoch,

Ok, so initwnd defines window scaling? When I tried doing pkt capture using trex-console, I saw the same value for window scaling, even for different tcp.initwnd value.

from trex.astf.api import *

import argparse

# IPV6 tunable example

#

# ipv6.src_msb

# ipv6.dst_msb

# ipv6.enable

#

class Prof1():

def __init__(self):

pass

def get_profile(self, tunables, **kwargs):

parser = argparse.ArgumentParser(description='Argparser for {}'.format(os.path.basename(__file__)),

formatter_class=argparse.ArgumentDefaultsHelpFormatter)

args = parser.parse_args(tunables)

# ip generator

ip_gen_c = ASTFIPGenDist(ip_range=["16.0.0.0", "16.0.0.255"], distribution="seq")

ip_gen_s = ASTFIPGenDist(ip_range=["48.0.0.0", "48.0.255.255"], distribution="seq")

ip_gen = ASTFIPGen(glob=ASTFIPGenGlobal(ip_offset="1.0.0.0"),

dist_client=ip_gen_c,

dist_server=ip_gen_s)

c_glob_info = ASTFGlobalInfo()

c_glob_info.tcp.mss = 1400

c_glob_info.tcp.initwnd = 3

c_glob_info.tcp.wnd_scale = 4

s_glob_info = ASTFGlobalInfo()

s_glob_info.tcp.mss = 1100

s_glob_info.tcp.initwnd = 3

c_glob_info.tcp.wnd_scale = 4

return ASTFProfile(default_ip_gen=ip_gen,

# Defaults affects all files

default_c_glob_info=c_glob_info,

default_s_glob_info=s_glob_info,

cap_list=[

ASTFCapInfo(file="../avl/delay_10_http_browsing_0.pcap", cps=1)

]

)

def register():

return Prof1()

Thanks,
Rashi

[Justin]

Hi, it depends on size of socket receive buffer which can be set by tcp.rxbufsize.

please look into this source code to see how the scale value is identified.