Solution for fun little challenge from Nick Russo https://twitter.com/nickrusso42518/status/1296852620959776777

dscp_conv_table.py

import csv
from pathlib import Path


def compute_dscp_class(dscp):
    quot, rmnd = divmod(dscp, 8)
    if rmnd == 0:
        dscpcl = "cs{}".format(quot)
    elif (quot, rmnd) == (5, 6):
        dscpcl = "ef"
    else:
        dscpcl = "af{}{}".format(quot, rmnd // 2)

    return dscpcl


def gen_conversion_table():
    tos_string_tbl = {
        0: "Routine",
        1: "Priority",
        2: "Immediate",
        3: "Flash",
        4: "FlashOverride",
        5: "Critical",
        6: "Internetworkcontrol",
        7: "Networkcontrol",
    }
    dscp_dec = [0, *list(range(8, 41, 2)), 46, 48, 56]
    conv_tbl = []

    for dscp in dscp_dec:
        tos_dec = dscp << 2
        dscpcl = compute_dscp_class(dscp)
        conv_tbl.append(
            {
                "DSCP Class": dscpcl,
                "DSCP (bin)": "{0:06b}".format(dscp),
                "DSCP (hex)": "{0:#04x}".format(dscp),
                "DSCP (dec)": "{}".format(dscp),
                "ToS (dec)": "{}".format(tos_dec),
                "ToS (hex)": "{0:#02x}".format(tos_dec),
                "ToS (bin)": "{0:08b}".format(tos_dec),
                "ToS Prec. (bin)": "{:08b}".format(tos_dec)[0:3],
                "ToS Prec. (dec)": "{}".format(dscp >> 3 & 1),
                "ToS Delay Flag": "{}".format(dscp >> 2 & 1),
                "ToS Throghput Flag": "{}".format(dscp >> 1 & 1),
                "ToS Reliability Flag": "0",
                "TOS String Format": "{}".format(tos_string_tbl[dscp // 8]),
            }
        )

    return conv_tbl


def main():
    conversion_table = gen_conversion_table()

    with Path("dscp_tos_conv_table.csv").open(mode="w", newline="") as fout:
        dict_writer = csv.DictWriter(f=fout, fieldnames=conversion_table[0].keys())

        dict_writer.writeheader()
        dict_writer.writerows(conversion_table)


if __name__ == "__main__":
    main()