PPP Modem Hangup

Hello,

I am working on establishing a ppp connection over serial (UART)
between two devices (Ubuntu/Linux machine and AOSP Target Device.

From the logs I see that the connection negotiation happens smoothly.
The request/ack is correctly exchanged between the two devices and a
ppp connection is established (ppp0 interface is created.

After about 6secs, there is Modem Hangup on the AOSP target device.
There are exchanges of data where data is sent from the Ubuntu/Linux
device and received on AOSP target device but no data is sent from the
AOSP target device.

I have played around with my options file; adjusting the baud rate,
MTU/MRU, compression is disabled, flow control and behavior settings
etc. But, it did not help with resolving the issue.

The options file for Ubuntu/Linux below:
# UART interface and baud rate
/dev/ttyUSB0 115200

#silent
nolock
kdebug 7

# Do not support ipv6
noipv6

# Flow control and behavior settings
xonxoff                   # Enable software flow control (XON/XOFF)
nodetach                  # Prevents ppd from running in the
backgroud. O/Ps logs to the terminal
debug                     # Enable detailed logging for debugging purposes
nocrtscts                 # Disable hardware flow control (no RTS/CTS
handshaking)
noauth                    # No authentication (open connection)
dump                      # prints out all the option values

# Serial communication settings
local                     # Do not use modem control lines; assume a
direct serial connection

# Compression settings (disable all forms of compression)
noccp                     # Disable CCP (Compression Control Protocol)
nobsdcomp                 # Disable BSD compression
nodeflate                 # Disable Deflate compression
novj                      # Disable Van Jacobson style TCP/IP header compression

# Connection persistence
persist                   # Automatically attempt to keep the
connection alive if it drops

# Transmission Settings
mtu 128                  # Set the Maximum Transmission Unit
mru 128                  # Set the Maximum Receive Unit

# IP addressing and routing settings
nodefaultroute             # Do not add a default route through the
PPP connection
noipdefault              # Do not request a specific IP address from the peer
10.0.0.1:10.0.0.2         # Local IP:Remote IP

# IPCP settings
ipcp-accept-remote        # Accept the IP address provided by the peer
#ipcp-accept-local
maxfail 0

# Link Control Protocol (LCP) settings
lcp-echo-interval 0       # Disable LCP echo requests (used to detect
dead connections)
lcp-echo-failure 0        # Disable LCP echo failure detection

the options file on AOSP Target device
# UART interface and baud rate
/dev/ttyMSM0 115200

kdebug 7

# Do not support ipv6
noipv6

# Flow control and behavior settings
xonxoff                  # Enable software flow control (XON/XOFF)
nodetach          # Prevents ppd from running in the backgroud. O/Ps
logs to the terminal
debug             # Enable detailed logging for debugging purposes
nocrtscts                 # Disable hardware flow control (no RTS/CTS
handshaking)
noauth                    # No authentication (open connection)
dump                      # prints all the option value

# Serial communication settings
local                     # Do not use modem control lines; assume a
direct serial connection
nolock

# Compression settings (disable all forms of compression)
noccp                     # Disable CCP (Compression Control Protocol)
nobsdcomp                 # Disable BSD compression
nodeflate                 # Disable Deflate compression
novj                      # Disable Van Jacobson style TCP/IP header compression

# Connection persistence
persist                   # Automatically attempt to keep the
connection alive if it drops

# Transmission Settings
mtu 128                  # Set the Maximum Transmission Unit
mru 128                  # Set the Maximum Receive Unit

# IP addressing and routing settings
nodefaultroute            # Do not add a default route through the PPP
connection
noipdefault               # Do not request a specific IP address from the peer
10.0.0.2:10.0.0.1   # Local IP : Remote IP

# IPCP settings
ipcp-accept-remote        # Accept the IP address provided by the peer

# Link Control Protocol (LCP) settings
lcp-echo-interval 0       # Disable LCP echo requests (used to detect
dead connections)
lcp-echo-failure 0        # Disable LCP echo failure detectioin

Error Logs on AOSP Target:
using channel 932
Using interface ppp0
Connect: ppp0 <--> /dev/ttyMSM0
sent [LCP ConfReq id=0x3 <mru 128> <asyncmap 0xa0000> <magic
0xc875a15e> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x3 <mru 128> <asyncmap 0xa0000> <magic
0x184ddd9> <pcomp> <accomp>]
sent [LCP ConfAck id=0x3 <mru 128> <asyncmap 0xa0000> <magic
0x184ddd9> <pcomp> <accomp>]
rcvd [LCP ConfAck id=0x3 <mru 128> <asyncmap 0xa0000> <magic
0xc875a15e> <pcomp> <accomp>]
sent [IPCP ConfReq id=0x3 <addr 10.0.0.2>]
rcvd [IPCP ConfReq id=0x3 <addr 10.0.0.1>]
sent [IPCP ConfAck id=0x3 <addr 10.0.0.1>]
rcvd [IPCP ConfAck id=0x3 <addr 10.0.0.2>]
local  IP address 10.0.0.2
remote IP address 10.0.0.1
Modem hangup
Connect time 0.1 minutes.
Sent 0 bytes, received 1276 bytes.
Connection terminated.

Any inputs to resolve the issue would be helpful.

Thanks,
Devesh