[ECOS] RE: ECOS PPP terminated because of echo-request being rejected by peer

["Weili Yao" <weili_yao at trimble dot com>]

It turns out that the LCP echo-reject from peer only happens on Sony
Ericsson T68i cell phone. I tried T-Mobile SIM and Cingular SIM in the
T68i cell phone and both SIM cards have the same behavior. But those SIM
cards just work fine on different cell phones (such as Nokia 6600).

In order for my device to work with T68i cell phone, I have to change
ECOS PPP so that it ignores LCP-echo-reject from peer. I treated the
LCP-echo-reject the same as LCP-echo-reply. 

I also compared the Linux PPP with ECOS PPP, and found that Linux PPP by
default does not send LCP-echo-request after PPP is up. Of course Linux
PPP allows user to set these parameters. 

I also compared the Windows-XP PPP, and Windows-XP does not send
LCP-echo-request either after PPP connection is established. 

By looking up the RFC documents, I could not find the meaning/reason of
LCP-echo-reject. So I think as long as my device is able to receive
LCP-echo-reply or LCP-echo-reject, I will consider the PPP connection is
fine and will keep the connection up. 

However, I am still wondering why Sony Ericsson T68i cell phone is
working differently. Maybe some bugs in Sony Ericsson T68i?

Cheers!

Weili Yao


-----Original Message-----
From: Weili Yao 
Sent: Friday, December 15, 2006 12:05 PM
To: ecos-discuss@sourceware.org
Cc: Weili Yao
Subject: ECOS PPP terminated because of echo-request being rejected by
peer



Hello, there:
    I have a device that is ECOS-based with Bluetooth connection to cell
phone (Sony-Ericsson T68i), and I have SIM card from T-Mobile in the
cell phone for the data connection. 
    When I established the PPP connection on the Bluetooth channel via
cell phone to T-Mobile ISP, the PPP would be up and running, but the
peer rejected echo-request made by ECOS like following (I decoded):

1) FF 03 C0 21 09 14 00 08 00 00 00 00 
    Sent to Peer:
   C0 21: LCP Protocol 
   09   : code (Echo Request)
   14   : ID (incremental)
   00 08: Length (including code, ID, len, and data followed)
   00 00 00 00: Magic Number
2) FF 03 C0 21 07 17 00 0C 09 14 00 08 00 00 00 00 
    Received from Peer:
    C0 21: LCP Protocol 
    07   : code (Code-Reject)
    17   : ID
    00 0C: len
    09 14 00 08 00 00 00 00: the original packet

    After 4 retries, the ECOS terminated the PPP connection. In that
period, the PPP was actually up and running. I just don't know why the
peer would reject the echo-request.

    In the net/ppp/current/src/pppd.c file, I then changed
lcp_echo_fails from 4 to 0 to ignore the LCP Code-Reject message from
peer. Then the connection will not be terminated by ECOS. The PPP
connection just works fine for me.

    Now my questions:

1) Is there any side-effect if I change lcp_echo_fails to 0 (i.e. ignore
the ECOH-Request reject message)?

2) The same SIM card is working fine with other cell phone (e.g. Nokia
6600) and GPRS/GSM modem without changing lcp_echo_fails. I don't see
the reject message. Did I miss something that is related to the cell
phone configuration?

   Thank you very much!

Weili Yao


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