Subject: [MOBILE-IP] Flow control for R-P interface

From: Ajoy Singh <[email-masked]>
Date: Tue, 7 Mar 2000 12:36:22 -0600

Hello All,

I have some concern regarding the R-P interface protocol that is being
proposed to tunnel PPP traffic from RNN to PDSN and vice versa for CDMA
2000 type of wireless network.

Current proposal for R-P interface does not talk about any flow control
scheme between RNN and PDSN. This kind of makes me nervous because in
the current situation,  RNN will end of doing buffering when it is
unable to send traffic to mobile node due to unavailability of radio
interfaces. In this model a RNN has to discard PPP traffic when buffer
overflows for a particular session.  As PPP framing is done between MS
and PDSN, so this type of approach will end of dropping fractions of
multiple frames by RNN unless HDLC framing is done by RNN, which is not
likely to happen.  Moreover in case of wireless network, we are talking
about using various header/payload compression schemes which is known to
degrade the performance in a lossy network. Is it not possible to
implement some type of flow control scheme between RNN and PDSN ?  I
think,  PDSN can use  that information to discard IP packets before
performing any header/payload compression ?  I know the flow control
scheme is removed from L2TP,  but i think it might be worth to discuss
the problem in case of R-P interface, as we are talking about shared
channel being used by different mobiles which is not true in current
L2TP implementations.  Moreover  in  case of L2TP framing is done by
LAC, so it is not possible that unframed data will be discarded between
LAC to LNS.

I am working on a draft that talks about flow control mechanism which
can be implemented between RNN and PDSN. I would like to find out view
of mobile ip working group members, whether they perceive this as a
problem or not.

regards,
ajoy