Monitoring a PPP Connection

[Doug Hardie]

I have a device that connects via PPP on a phone line (V.90) to my ISP. 
  However, I am seeing significant delays on the connection but can't 
find a cause.  I am looking for something that will monitor the phone 
line - like tcpdump for a phone line.  I know that there are some 
expensive devices out there that do that, but this doesn't warrant 
spending that much.  I don't see any easy way to capture both the 
uplink and downlink signals though.  Regular modems only monitor the 
downlink side.