Subject: [Gen-art] Gen-ART review of draft-ietf-mipshop-transient-bce-pmipv6-06

From: "Spencer Dawkins" <[email-masked]>
Date: Wed, 25 Aug 2010 03:11:05 -0500

I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
< http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.

Please wait for direction from your document shepherd
or AD before posting a new version of the draft.

Document: draft-ietf-mipshop-transient-bce-pmipv6-06
Reviewer: Spencer Dawkins
Review Date: 24 August 2010
IESG Telechat date: 26 August 2010

Summary: This specification is ready for publication as an Experimental RFC.

Comments: I have a small number of nits, forwarded for the convenience of 
any downstream editors.

Abstract

   This document specifies a mechanism which enhances Proxy Mobile IPv6
   protocol signaling to support the creation of a transient binding
   cache entry which is used to optimize the performance of dual radio
   handover, as well as single radio handover.  This mechanism is
   applicable to the mobile node's inter-MAG handover while using a
   single interface or different interfaces.  The handover problem space
   using the Proxy Mobile IPv6 base protocol is analyzed and the use of
   transient binding cache entries at the local mobility anchor is
   described.  The specified extension to the Proxy Mobile IPv6 protocol
   ensures optimized forwarding of downlink as well as uplink packets
   between mobile nodes and the network infrastructure and avoids
   superfluous packet forwarding delay or even packet loss.

Spencer (nit): "or even packet loss"? maybe there's a qualifier missing? :D

1.  Introduction

   According to the PMIPv6 base specification, an LMA updates a mobile
   node's (MN) Binding Cache Entry (BCE) and switches the forwarding
   tunnel after receiving a Proxy Binding Update (PBU) message from the
   mobile node's new MAG (nMAG).  At the same time the LMA disables the
   forwarding entry towards the mobile node's previous MAG (pMAG).  In
   case of an inter-technology handover, the mobile node's handover
   target interface must be configured according to the Router
   Advertisement being sent by the nMAG.  Address configuration as well
   as possible access technology specific radio bearer setup may delay
   the complete set up of the mobile node's new interface before it is
   ready to receive or send data packets.  In case the LMA performs
   operation according to [RFC5213] and forwards packets to the mobile
   node's new interface after the reception of the PBU from the nMAG,
   some packets may get lost or experience major packet delay.  The
   transient BCE extension, as specified in this document, increases
   handover performance (optimized packet loss and forwarding delay)
   experienced by MNs, which have multiple network interfaces
   implemented while handing over from one interface to the other.  The
   transient BCE extension increases also handover performance for

Spencer (nit): s/increases also/also increases/

   single radio MNs, which build on available radio layer forwarding
   mechanisms, hence re-use existing active handover techniques.

3.1.  Handover using a single interface

   In some active handover scenarios, it is necessary to prepare the
   nMAG as handover target prior to the completion of the link layer
   handover procedures.  Packets sent by the LMA to the nMAG before the
   completion of the link layer handover procedure will be lost or need
   to be buffered.

Spencer (nit): "will be lost unless they are buffered"?

   In some systems, the nMAG will be the recipient of uplink traffic
   prior to the completion of the procedure that would result in the
   PBU/PBA handshake.  These packets cannot be forwarded to the LMA.

3.3.  Need for a common solution

   This document specifies transient BCEs as an extension to the PMIPv6
   protocol.  Set up and configuration of a transient BCE can be
   performed by means of extended PMIPv6 signaling messages between the
   MAG and the LMA component using a new Transient Binding mobility
   option.  The transient BCE mechanism supports three clearly
   distinguished sequences of transient states to suit various handover
   scenarios and to improve handover performance for both, inter- and

Spencer (nit): s/both,/both/

   intra-technology handover.  As a result of using transient BCEs,
   excessive packet buffering at the nMAG during the MN's handover
   process is not necessary and packet losses and major jitter can be
   avoided.

4.8.  Protocol Stability

   Lost connection with pMAG during late path switch:  In case an MN
      looses connectivity to its pMAG during a transient BCE phase with

Spencer (nit): s/looses/loses/

      late path switch and the nMAG fails to initiate turning a
      transient BCE into an active BCE to perform the path switch to the
      nMAG, in a worst case downlink packets are lost until the chosen
      TIMEOUT_1 expires.  After TIMEOUT_1 seconds, the protocol
      operation has been recovered successfully.  However, this case is
      very unlikely for two reasons: If the connectivity to the pMAG is
      lost, the pMAG will send a deregistration PBU for the MN to the
      LMA, which results in turning the transient BCE into an active BCE
      and in a path switch.  Furthermore, the nMAG will initiate turning
      the transient BCE into an active BCE as soon as the set up of the
      data link between the MN and the nMAG has been completed
      (Section 4.4).  Note that this case in particular affects downlink
      packets, whereas uplink packets can be sent through the new
      connection after a broken link to the pMAG has been detected.