5. Look at what's happening:

The master logs in into the slave, starts pppd, and redirects this all thing into a local pty. It consists of the following steps:

• allocating a new pty
• sshing into the slave
• running pppd on the slave
• the master runs pppd in this local pty
• and sets up the routing table on the client.

There are (not very tight) timing considerations involved, this is why that 'sleep 10s'.