ipppd software package provides ISDN utilities - PPP daemon, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install ipppd
ipppd is installed in your system.
Make ensure the ipppd package were installed using the commands given below,
$ sudo dpkg-query -l | grep ipppd *
You will get with ipppd package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Network |
| Package | ipppd |
| Version | 1:3.25+dfsg1-3.7ubuntu1 |
| Description | ISDN utilities - PPP daemon |
| Sub Section | Net |