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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.
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