pptp connection was terminated after it was started for a while

Question

I tried to set up VPN connection on an ubuntu host. here were my steps. after the connection was terminated, I had to last two steps. Any idea why the connection is not stable? I did this work on AWS EC2 instance. Many thanks!

sudo -s
apt-get install pptp-linux
pptpsetup --create alauda_build --server 52.68.x.x --username vpn_tester --password <password> --encrypt
pon vpn_test debug dump 2 logfd nodetach
route add default dev ppp0

output:

pppd options in effect: 
debug        # (from command line) 
nodetach        # (from command line) 
persist        # (from /etc/ppp/peers/vpn_test) 
logfd 2        # (from command line) 
dump        # (from command line) 
noauth        # (from /etc/ppp/peers/vpn_test) 
name vpn_tester        # (from /etc/ppp/peers/vpn_test) 
remotename vpn_test        # (from /etc/ppp/peers/vpn_test) 
        # (from /etc/ppp/peers/vpn_test) 
pty pptp x.x.x.x --nolaunchpppd        # (from /etc/ppp/peers/vpn_test), hide the password 
crtscts        # (from /etc/ppp/options) 
        # (from /etc/ppp/options) 
asyncmap 0        # (from /etc/ppp/options) 
lcp-echo-failure 4        # (from /etc/ppp/options) 
lcp-echo-interval 30        # (from /etc/ppp/options) 
hide-password        # (from /etc/ppp/options) 
ipparam vpn_test        # (from /etc/ppp/peers/vpn_test) 
nobsdcomp        # (from /etc/ppp/peers/vpn_test) 
nodeflate        # (from /etc/ppp/peers/vpn_test) 
require-mppe-128        # (from /etc/ppp/peers/vpn_test) 
noipx        # (from /etc/ppp/options) 
using channel 34 
Using interface ppp0 
Connect: ppp0 <--> /dev/pts/4 
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x63662628> <pcomp> <accomp>] 
rcvd [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0xfb01ac1> <pcomp> <accomp>] 
sent [LCP ConfAck id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0xfb01ac1> <pcomp> <accomp>] 
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0x63662628> <pcomp> <accomp>] 
sent [LCP EchoReq id=0x0 magic=0x63662628] 
rcvd [LCP EchoReq id=0x0 magic=0xfb01ac1] 
sent [LCP EchoRep id=0x0 magic=0x63662628] 
rcvd [CHAP Challenge id=0x36 <6937cf224af1afe0a65568ddc9f186ae>, name = "pptpd"] 
sent [CHAP Response id=0x36 <3d8e45c218d89529219e105db021e2fd0000000000000000f274aef515020c066234c7220443bcb6b02173d361f642f500>, name = "vpn_tester"] 
rcvd [LCP EchoRep id=0x0 magic=0xfb01ac1] 
rcvd [CHAP Success id=0x36 "S=9B5067A80B921CC0454FCFB594344C1472D6067D M=Access granted"] 
CHAP authentication succeeded 
sent [CCP ConfReq id=0x1 <mppe +H -M +S -L -D -C>] 
rcvd [CCP ConfReq id=0x1 <mppe +H -M +S -L -D -C>] 
sent [CCP ConfAck id=0x1 <mppe +H -M +S -L -D -C>] 
rcvd [CCP ConfAck id=0x1 <mppe +H -M +S -L -D -C>] 
MPPE 128-bit stateless compression enabled 
sent [IPCP ConfReq id=0x1 <compress VJ 0f 01> <addr 172.31.x.x>] 
rcvd [IPCP ConfReq id=0x1 <addr 192.168.240.1>] 
sent [IPCP ConfAck id=0x1 <addr 192.168.240.1>] 
rcvd [IPCP ConfRej id=0x1 <compress VJ 0f 01>] 
sent [IPCP ConfReq id=0x2 <addr 172.31.x.x>] 
rcvd [IPCP ConfNak id=0x2 <addr 192.168.240.17>] 
sent [IPCP ConfReq id=0x3 <addr 192.168.240.17>] 
rcvd [IPCP ConfAck id=0x3 <addr 192.168.240.17>] 
local  IP address 192.168.240.17 
remote IP address 192.168.240.1 
Script /etc/ppp/ip-up started (pid 5333) 
Script /etc/ppp/ip-up finished (pid 5333), status = 0x0 
Script pptp 52.68.x.x --nolaunchpppd finished (pid 5317), status = 0x0 
Modem hangup 
Connect time 5.6 minutes. 
Sent 252 bytes, received 252 bytes. 
Script /etc/ppp/ip-down started (pid 5399) 
MPPE disabled 
sent [LCP TermReq id=0x2 "MPPE disabled"] 
Connection terminated. 

Answer 1

need change the MTU set in VPN server config to 1356