ttcp_atm: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/ttcp_atm - from package: atm-tools

You may install the required package with command apt-get install {package}

Error in other languages:
ttcp_atm: bevel nie gevind nie
ttcp_atm: comandă negăsită
ttcp_atm: comando não encontrado
ttcp_atm: commande introuvable
ttcp_atm: command not found
ttcp_atm: käsku ei ole
ttcp_atm: không tìm thấy lệnh
ttcp_atm: komanda nerasta
ttcp_atm: Kommando nicht gefunden.
ttcp_atm: kommandot finns inte
ttcp_atm: komut yok
ttcp_atm: nie znaleziono polecenia
ttcp_atm: níor aimsíodh an t-ordú
ttcp_atm: no se encontró la orden
ttcp_atm: no s'ha trobat l'ordre
ttcp_atm: opdracht niet gevonden
ttcp_atm: parancs nem található
ttcp_atm: perintah tidak ditemukan
ttcp_atm: príkaz nenájdený
ttcp_atm: příkaz nenalezen
ttcp_atm: команда не найдена
ttcp_atm: командата не е открита
ttcp_atm: 命令找不到
ttcp_atm: コマンドが見つかりません