[Mobopts] Re: Review of draft-irtf-mobopts-mpa-framework-00

Ashutosh Dutta <adutta@research.telcordia.com> Wed, 24 October 2007 16:00 UTC

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From: Ashutosh Dutta <adutta@research.telcordia.com>
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Cc: ktaniuchi@tari.toshiba.com, William Arbaugh <waa@cs.umd.edu>, Mobopts <mobopts@irtf.org>, vfajardo@tari.toshiba.com, Henning Schulzrinne <hgs@cs.columbia.edu>
Subject: [Mobopts] Re: Review of draft-irtf-mobopts-mpa-framework-00
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           Appreciate your careful review of the draft 
draft-irtf-mobopts-mpa-framework-00. We will take care of these comments 
and suggestions in the revised version of the draft.

Based on Rajeev's email few days back, I also take this opportunity to 
solicit comments and suggestions from others in the mailing list on this 


Christian Vogt wrote:
> Folks,
> Ashutosh asked me to take a look at
> draft-irtf-mobopts-mpa-framework-00, which I am happy to do.
> Draft-irtf-mobopts-mpa-framework-00 specifies a framework for efficient 
> and secure handovers of mobile hosts between administrative separate 
> networks.  This includes a pre-authentication of the mobile hosts to one 
> or more candidate networks.  The framework is generic in that it is 
> independent of the authentication mechanism and mobility protocol.
> A strength of this framework is that it is based on security
> relationships between a mobile host and different networks,
> whereas it does not depend on trust or security
> relationships between administrative separate networks.
> This is an advantage in terms of deployment scalability, in
> particular in a more and more heterogeneous Internet.
> The draft is of good editorial quality.  It also describes
> related work and clearly explains how it differs from that.
> Below some more specific technical comments:
> - One meta-question I have is why the proactive handover
> tunnel connects the mobile host's old point of attachment
> with the new access router, and not the mobile host's new
> point of attachment with the old access router.  In most
> cases, this may not make a difference.  But if the signal
> strength on the old link is fading quickly, it would be
> advantageous to have the mobile host connect to the new
> point of attachment as early as possible.  E.g., F-MIPv6
> follows the latter approach and may hence work better when
> the overlap between the old and new point of attachment is
> small.
> - Section 1.1 lists end-to-end delay as a performance
> requirement and cites ITU-T G.114 (One-Way Transmission
> Time).  The transmission time is not directly related to
> mobility management, however, unless you consider
> propagation stretches that arise from tunneling, such as in
> case of the proactive handover tunnel.
> - Section 1.1:
>> During a mobile's handover, transient traffic cannot
>> reach the mobile and this contributes to the jitter as
>> well.
> Transient traffic during a handover is lost, whereas jitter
> considers the deviation in inter-arrival times of
> successfully delivered packets.  So the loss of transient traffic during 
> a handover does not contribute to jitter.  I would rephrase this.
>> According to ETSI TR 101 [ETSI], a normal voice conversation can 
>> tolerate up to 2% packet loss.
> This value is, to my knowledge, the mean packet loss
> probability that can be repaired by loss concealment
> techniques.  The value hence does not apply to the handover
> case, which is special in that the packet loss probability
> is 100% for a short period.  Total packet loss cannot be
> repaired by loss concealment techniques -- although some
> techniques /attempt/ to repair it by repeating the last
> received voice frame several times with decreasing volume.
> A more appropriate metric than the average packet loss
> probability would be the handover delay (i.e., for how long
> there is a packet loss of 100%).  The handover delay is the time during 
> which the user does not hear anything. Unfortunately, ITU has to my 
> knowledge never developed a recommendations on what the maximum handover 
> delay should be.
> - Figure 1:  Connection between access routers misses in
> domain B.  L2 switch in domain B is not labeled.
> - Section 6.3:  Maybe you should add some recommendations on who eagerly 
> the mobile host should pre-authenticate with different candidate 
> networks.  These recommendations should optimally consider the mobile 
> host's policies, signaling overhead, and handover robustness.
> This is a valuable contribution.  Go ahead and publish once Rajeev and 
> William give you green light! :-)
> Ciao,
> - Christian

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