One document matched: draft-premec-netlmm-bulk-re-registration-02.txt
Differences from draft-premec-netlmm-bulk-re-registration-01.txt
NetExt Working Group D. Premec
Internet Draft Nokia Siemens Networks
Intended status: Informational B. Patil
Expires: September 2009 Nokia
S. Krishnan
Ericsson
March 9, 2009
Bulk Re-registration for Proxy Mobile IPv6
draft-premec-netlmm-bulk-re-registration-02.txt
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Abstract
The Proxy Mobile IPv6 specification requires the Mobile Access
Gateway (MAG) to send a separate Proxy Binding Update (PBU) message
to the Local Mobility Agent (LMA) for each mobile node (MN) to renew
the MN's mobility binding. This document defines a mechanism by which
a MAG can update the mobility bindings of multiple MNs attached to it
with a single PBU message to the serving LMA. This mechanism is also
intended to be used by a MAG to re-establish bindings at a new LMA
when its old LMA fails.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Table of Contents
1. Introduction...................................................2
2. Terminology....................................................4
3. Bulk Re-registration Overview..................................4
4. Message formats................................................6
4.1. Proxy Binding Update message..............................6
4.2. Proxy Binding Acknowledgment message......................7
4.3. Bulk Set Identifier.......................................8
5. MAG Operation..................................................8
6. LMA operation.................................................10
7. Security Considerations.......................................11
8. IANA Considerations...........................................12
9. Acknowledgments...............................................12
10. References...................................................12
10.1. Normative References....................................12
Author's Addresses...............................................13
1. Introduction
The Proxy Mobile IPv6 (PMIPv6) specification [RFC5213] defines a
PMIPv6 domain as a network which provides a network based IP mobility
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service by deploying the PMIPv6 protocol. A MAG performs the mobility
related signaling on behalf of a MN by sending the Proxy Binding
Update (PBU) message to a LMA. When the binding lifetime of a
particular MN is close to expiry, the MAG renews the registration of
the MN by sending a PBU message, to the LMA, requesting the extension
of the binding lifetime.
A single LMA serves multiple MAGs and the capacity of the LMA in
terms of the number of attached MNs can be quite large. It can be
expected that LMA capacity in managed networks may easily exceed
hundreds of thousands or more attached MNs.
The following simple formula gives an estimate of the average number
of re-registration transactions per second as a function of the
number of registered MNs and the binding lifetime period:
transactions/sec = (number of registered MNs) / (binding lifetime*4)
For 50.000 MNs and the binding lifetime of half an hour this gives:
50000 MNs / 1800 sec = 27,7 transactions/sec
Based on the above formula it is apparent that the default re-
registration process where the MAG sends a separate message for each
MN is inefficient or suboptimal. These re-registration messages
consume significant network resources both in terms of processing
power at the LMA and MAG and network bandwidth. In addition, since
the registration messages are sent per MN, there is no efficient way
for the MAG to recover from the failure of an LMA. It needs to resend
registration messages for each MN attached to it, towards a new LMA.
This increases the service disruption interval.
This document proposes an optimization of the re-registration process
by which the signaling load for re-registration can be reduced to a
single transaction per MAG, irrespective of the number of attached
MNs.
A MAG adds a MN to a set of MNs re-registered in a bulk mode by
setting the bulk re-registration bit (B) in the PBU message. A PBU
message with the B bit set may include multiple MNs and the LMA
creates new bindings for all the MNs listed in the bulk registration
message. The PBU message sent in response may contain the Bulk Set ID
mobility option (defined in section 4.3). The bulk set ID is an
opaque identifier allocated by the LMA which uniquely identifies the
bulk set to which the MN was added.
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A MAG requests a bulk re-registration for a set of MNs by sending a
single PBU message which includes a Bulk Set ID mobility option and
the LMA extends the binding lifetime of MNs that are members of the
received bulk set ID. By using this method, the MAG and LMA
accomplish the re-registration of MNs attached to a MAG in a single
transaction. The number of re-registration transactions at the LMA
becomes independent of the number of attached MNs; instead it is
dependent only on the number of MAGs.
In addition to minimizing the signaling overhead associated with the
lifetime extension of the mobility bindings, the MAG and LMA may use
a single timer per bulk re-registration set to monitor the binding
lifetime of all the member MNs instead of an individual timer per MN.
2. Terminology
General mobility related terminology is defined in [RFC3775].
Additional PMIPv6 specific terminology can be found in [RFC5213].
PMIPv6 domain
Network providing the network based IP mobility service as
defined in [RFC5213].
PMIPv6
Proxy Mobile IPv6 protocol specified in [RFC5213].
Bulk re-registration
PBU/PBAck message exchange where the bulk re-registration flag
(B) is set to 1.
bulk re-registration set
a set containing the MNs to which the request for bulk
re-registration applies.
3. Bulk Re-registration Overview
The bulk re-registration mechanism allows the MAG and the LMA to
extend the binding lifetime for a number of MNs with a single
transaction. The MAG and LMA maintain a set of MNs that can be re-
registered in bulk mode. Such set is called a bulk re-registration
set and is a subset of the MNs attached to a MAG. There can be
multiple bulk re-registration sets for a given MAG-LMA pair.
Initially the bulk re-registration set is empty. MAG requests to add
individual MNs to the bulk set by sending a regular PBU message that
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identifies an individual MN and additionally the bulk registration
flag in the message is set to 1. Based on the received bulk re-
registration bit the LMA adds the MN to the bulk re-registration set
and responds with the PBAck message with the bulk registration flag
(B) set to 1.
Once there is a non-empty bulk re-registration set, MAG can request
to extend the binding lifetime for all MNs that are part of the bulk
re-registration set by sending a PBU message and omitting any options
that would identify an individual MN. In particular, the MAG omits
both the MN ID (Mobile Node Identifier) option and the HNP (Home
Network Prefix) options.
If the bulk registration message is being sent to recover from an LMA
failure the MAG MUST explicitly identify all the MNs that are
included in the bulk registration set and provide all the mobility
options that need to be included in an initial PBU. Due to the size
of these options, the MAG may not be able to fit all the MNs attached
to it into a single PBU. In this case the MAG will split the MNs
across multiple PBUs. The receiving LMA can use the information
included in these bulk PBUs to recreate the bulk registration set, so
that the MAG can renew the MNs' lifetimes later with a single PBU.
There may be different triggers that cause the MAG to request a bulk
re-registration. Typically the trigger is the binding lifetime expiry
of a MN that is a member of a bulk re-registration set. There could
be other triggers as well, but they may be implementation or domain
specific and outside the scope of this specification.
When the MAG requests the MN to be added to the bulk re-registration
set, the LMA may include the Bulk Set ID mobility option in the PBAck
message. The bulk set ID is an opaque identifier allocated by the LMA
that uniquely identifies the bulk set to which the MN was added. The
MAG associates the MN with the bulk set ID received in the PBAck.
The MAG includes the Bulk Set ID mobility option set to the value
previously received from the LMA to request the bulk re-registration
for the MNs that are part of this particular bulk re-registration
set. The MAG may include multiple instances of the Bulk Set ID option
in the PBU message to request lifetime refreshment for several bulk
sets in a single message.
The LMA extends the mobility binding of all MNs that are members of
indicated bulk re-registration sets and responds with PBAck message
echoing the received Bulk Set ID mobility options.
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A MAG may remove a MN from a bulk re-registration set by sending a
regular PBU message identifying the MN to be removed and with the
bulk re-registration flag set to 0.
When requested to add a MN to the bulk re-registration set, the LMA
may reject the request. In this case the LMA processes the PBU
message as if the bulk re-registration flag was not set and responds
with PBAck message where the bulk re-registration flag is set to 0.
4. Message formats
This section introduces extensions to PBU and PBAck messages used in
this specification.
4.1. Proxy Binding Update message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K|M|R|P|B| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 Proxy Binding Update message
A Proxy Binding Update message is defined in the [RFC5213]. A new
flag (B) is defined for the Binding Update message.
Bulk Registration Flag (B)
If the bulk registration flag (B) is set to 1, then the PBU message
is a request to add the MN to the bulk re-registration set. If the
bulk registration flag (B) is set to 0 and if the MN is found to be a
member of the bulk re-registration set, then the MN is removed from
the bulk re-registration set.
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Mobility Options
For descriptions of the mobility options, refer to [RFC5213]. When
the bulk registration flag is set to 1, the PBU message containing
multiple MN ID and HNP options is valid and is processed as described
in section 3. When set to refresh binding in a bulk mode, the PBU
message contains at least one Bulk Set ID mobility option and does
not contain the MN-ID and the HNP mobility options.
4.2. Proxy Binding Acknowledgment message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status |K|R|P|B| Res. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 Proxy Binding Acknowledgment message
A Proxy Binding Acknowledgment message is defined in the [RFC5213]. A
new flag (B) is defined for the Binding Acknowledgment message.
Bulk Registration Flag (B)
A new flag (B) is included in the Binding Acknowledgment message to
indicate to the MAG that the MN was successfully added to the bulk
re-registration set. The flag MUST NOT be set to the value of 1 if it
was not set to 1 in the corresponding PBU message.
Mobility Options
For descriptions of these options, refer to [RFC5213]. When the bulk
registration flag is set to 1 in the PBU message, then the PBAck
message may also contain the Bulk Set ID mobility option. When the
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Bulk Set ID mobility were included in the PBU message, the PBAck
message echoes back the Bulk Set ID options from the PBU message.
4.3. Bulk Set Identifier
The format of the Bulk Set ID option is as shown below and its
alignment requirement is 4n+2.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bulk Set ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Bulk Set ID Mobility Option
Type: TBD, uniquely identifies the option as the Bulk Set ID
mobility option.
Length: 0 or 4
Bulk set ID: a 32-bit unsigned integer that identifies a bulk
re-registration set.
The Bulk Set ID option is valid in the Proxy Binding Update and Proxy
Binding Acknowledgment messages. The semantics of the Bulk Set ID
option is defined in section 3.
5. MAG Operation
When a new MN attaches to a MAG, the MAG SHALL register the MN with
the LMA by sending the PBU message formatted as described in
[RFC5213]. Additionally, the MAG MAY set the bulk registration flag
(B) in the PBU message to 1 to request the LMA to add the MN to the
bulk registration set. The decision to request the bulk re-
registration mode for a MN is a matter of local policy at the MAG and
is outside the scope of this specification.
The MAG SHALL add the MN to its bulk re-registration set when it
receives a PBAck message with the bulk registration bit set to 1 and
if the corresponding PBU message was requesting the LMA to add the MN
to the bulk re-registration set. The MAG SHALL maintain a separate
bulk re-registration set for each LMA. If the PBAck message contains
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the Bulk Set ID option, the MAG SHALL associate the MN being
registered with the indicated bulk set identifier.
When the binding lifetime of any MN contained in the bulk re-
registration set is about to expire, the MAG SHALL request the bulk
re-registration by sending the PBU message containing the Bulk Set ID
mobility option. The length of the Bulk Set ID option may be 0 in
which case the MAG is requesting a refreshment of the binding
lifetime for all MN attached to that MAG that were registered with
the B flag set. Alternatively, the MAG may include one or more Bulk
Set ID options containing the values that were indicated by the LMA
in the PBAck messages when the MN was added to the bulk set. In this
case the MAG asks for refreshment of specific bulk sets indicated by
the Bulk Set ID options. The MAG SHALL NOT include the MN ID and the
HNP options in the PBU message requesting bulk refreshment.
The MAG MAY also trigger a bulk re-registration at any time. The
policy and exact conditions for these additional triggers are outside
of scope of this specification.
If the bulk registration message is being sent to recover from an LMA
failure the MAG MUST explicitly identify all the MNs that are
included in the bulk registration set and provide all the mobility
options that need to be included in an initial PBU. Due to the size
of these options, the MAG may not be able to fit all the MNs attached
to it into a single BU. In this case the MAG MUST split the MNs
across multiple BUs.
When the MAG receives a PBAck message indicating success and which
echoes the Bulk Set ID options that were included in the
corresponding PBU message, the MAG SHALL update the binding lifetime
of all affected MNs to the lifetime value contained in the PBAck
message. If in the case of bulk re-registration the PBAck message
repeatedly indicates an error, the MAG SHALL fall back to individual
re-registration mode.
Instead of maintaining one timer per MN, the MAG MAY start a single
timer per bulk registration set to oversee the binding lifetime of
all MNs that are members of that bulk registration set.
If the MAG sets the bulk re-registration bit to 1 in a PBU message
but the bulk registration bit (B) is set to 0 in a PBAck message, the
MAG SHALL process the PBAck message as per [RFC5213]. In addition,
the MAG SHALL infer that the LMA does not support bulk re-
registration procedure. The MAG SHALL switch to regular, per-MN re-
registration mode as described in [RFC5213]. The MAG MAY retry the
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bulk re-registration procedure after sufficient time has elapsed from
the previous unsuccessful bulk re-registration. This amount of time
SHOULD be configurable at the MAG.
6. LMA operation
When the LMA receives a PBU message with a bulk registration bit (B)
set to 1, the LMA SHALL first process the PBU message as per
[RFC5213]. Upon successful processing of the message, the LMA SHALL
perform additional processing of the PBU message as described further
below for bulk mode re-registrations.
If the PBU message contains multiple MNIDs and/or HNP options, and
the LMA cannot find a matching binding cache entry, the LMA MUST
consider this to be equivalent to receiving multiple PBUs with one
MNID and/or HNP option each.
If the bulk re-registration flag in the PBU message is set to 1, the
LMA MAY add the MN(s) indicated in the PBU to the set of MNs re-
registered in a bulk mode, subject to the local policy. The decision
whether to enable bulk re-registration mode is a matter of local
policy at the LMA and is outside the scope of this specification.
If the LMA decides to accept the bulk re-registration mode for the
MN, it SHALL add the MN to a bulk re-registration set. The LMA SHALL
maintain distinct bulk re-registrations set per MAG and there could
be several such sets per single MAG.
Upon adding the MN to the bulk re-registration set, the LMA SHALL
respond with the PBAck message containing the bulk registration bit
set to 1. The LMA may include the Bulk Set ID option in the PBAck
message. The bulk set ID is allocated by the LMA and identifies the
particular bulk set to which the MN is assigned.
The PBU message without the MN ID and HNP options but including the
Bulk Set ID mobility option is a valid message and indicates a
request for bulk mode re-registration of all MNs that are members of
the indicated bulk re-registration set. There MAY be several Bulk Set
ID options in the PBU message, in which case the MAG requests the
bulk refreshment of all MNs that are members of the indicated bulk
sets. If the length of the Bulk Set ID option is zero, the MAG is
requesting a lifetime refreshment of all the MN attached to the MAG
that are members of any bulk set. The LMA SHALL extend the binding
lifetime of all affected MNs attached to the MAG that sent the bulk
PBU.
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The LMA SHALL set the binding lifetime of all MNs re-registered in a
bulk mode to expire at the same point in time.
Upon successful processing of bulk mode re-registration request, the
LMA MUST respond with a PBAck message indicating success and echoing
the mobility options received from the PBU. The lifetime in the PBAck
message indicates the time when binding cache entries of affected MNs
will expire.
The LMA MAY reject the request for bulk re-registration. In this case
the LMA MUST NOT update binding cache entries of any MNs and SHALL
respond with PBAck indicating the reason for the rejection in the
status code.
After successfully processing the bulk PBU message, the LMA SHOULD
start a single timer to oversee the binding lifetime of all MNs
affected by this bulk re-registration transaction.
The LMA not supporting this specification ignores the bulk re-
registration bit (B) and the Bulk Set ID option in a PBU message and
processes the message as per the baseline specification [RFC5213]. In
this case the PBAck message sent in response contains the bulk re-
registration bit (B) is set to 0.
If the LMA that does not support this specification receives a bulk
PBU message that does not contain any options identifying a
particular MN then the LMA responds with the PBAck message where the
status field contains one of the following error codes:
MISSING_HOME_NETWORK_PREFIX_OPTION
MISSING_MN_IDENTIFIER_OPTION
These error codes are defined in the baseline specification
[RFC5213].
7. Security Considerations
The bulk re-registration mechanism does not introduce any new
security threat or vulnerability to the PMIPv6 specification.
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8. IANA Considerations
None.
9. Acknowledgments
Thanks to Jouni Korhonen for his review and input.
This document was prepared using 2-Word-v2.0.template.dot.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in
IPv6", RFC 3775, June 2004.
[RFC5213] Gundavelli, S., Ed., "Proxy Mobile IPv6", RFC 5213, August
2008
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Author's Addresses
Domagoj Premec
Nokia Siemens Networks
Heinzelova 70a
10000 Zagreb
Croatia
Email: domagoj.premec.ext@nsn.com
Basavaraj Patil
Nokia
6000 Connection Drive
Irving, TX 75039
USA
Email: basavaraj.patil@nokia.com
Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
Email: suresh.krishnan@ericsson.com
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