Internet DRAFT - draft-vonhugo-multimob-dmm-context
draft-vonhugo-multimob-dmm-context
MULTIMOB Group D. von Hugo
Internet-Draft Telekom Innovation Laboratories
Intended status: Experimental H. Asaeda
Expires: September 20, 2013 NICT
P. Seite
France Telecom - Orange
March 19, 2013
Context Transfer for Multicast support in Distributed Mobility
Management (DMM)
draft-vonhugo-multimob-dmm-context-02
Abstract
This document describes a context transfer based concept to support
overarching IP multicast services applicable to various existing
approaches for Distributed Mobility Management.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 5
3. Handover Process . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Multicast Context Transfer Data Format . . . . . . . . . . 7
3.2. Multicast Context Transfer with MLD Proxy . . . . . . . . 7
3.3. Multicast Context Transfer with PIM-SM . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
This document describes an application of various existing approaches
for Distributed Mobility Management (DMM) [15] to support overarching
IP multicast services with Proxy Mobile IPv6 (PMIPv6) [3] and Client
Mobile IPv6 (MIPv6) [2], respectively. Key concept of Distributed
Mobility Management (DMM) in a flat network architecture where core
entities and functionalities are deployed in a distributed manner
assumes a mobile node to use the first access router (AR) it attaches
to as principal mobility anchor, i.e. Home Agent (HA) in MIPv6 or
Local Mobility Anchor (LMA) in PMIPv6. Requirements for future DMM
protocols are listed and discussed in [22]. Current proposals for
DMM based Mobility such as MIP-based Distributed Mobility Anchoring
(DMA) [16] and [21] as well as PMIP-based solutions for Distributed
Mobility Management [17], [20] ... and so forth define new AR
capabilities applicable to a flat architecture. Common idea of the
various approaches is to distribute functionalities for local
attachment of a MN to the network and for dynamically keeping track
of a MN and its current sessions, also in case of MN attachment to a
different AR, to all Access Routers. These ARs are denoted here by
DMM ARs (DARs) which are responsible for hosting (anchoring) newly
attached MNs and their started sessions (flows), and for relaying old
sessions to the MNs' previous DAR(s), respectively. Some solutions
refer to a common data base containing all relevant MN information
for retrieval which may be co-located with existing logical entities
such as DMM-defined Local Mobility Anchor (LMA) or a new common
central Mobility Database (MDB).
The MultiMob Base Protocol [12] specifies a mechanism for supporting
multicast reception within a PMIPv6 domain using Multicast Listener
Discovery (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying") [7].
Several extensions have been proposed to optimize Routing or session
continuity during Handover of a MN. While some approaches rely on
the LMA anchoring of a MN to speed up the subscription process during
handover as proposed in [19] others apply on an extension of Context
Transfer Protocol (CXTP) [10] specification directly [11] or via the
established fast HO approach using FPMIP/FMIP [14] to support
forwarding of multicast group subscription and traffic data between
MAGs. Within a DMM-like approach where location (i.e. anchoring) and
access functionality can be handled by the same entity a data
exchange between the current AR and a prior one to ensure low delay
and loss could be achieved without enhancing complexity too much by
applying the CTXP modification directly. In case of node mobility
during an ongoing multicast reception session the node should be able
to continuously receive the multicast data through the new AR just
after handover completion without any MLD signaling on the new
wireless link. This procedure is multicast context transfer that
provides multicast session continuity and avoids extra packet loss
and session disruption. Multicast context transfer will be the
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required function to support seamless handover, while for its
effective procedure, interaction with multicast communication
protocols should be taken into account. To synchronize multicast
with unicast traffic measures to prevent delay extension due to
waiting for multicast information should be established as proposed
in [19]
The Context Transfer Protocol (CXTP) specification [10] describes the
mechanism that allows better support for minimizing service
disruption during handover. This document proposes to extend CXTP
for forwarding of multicast context transfer in a DMM domain.
"Multicast-Context Transfer Data (M-CTD)" message as defined in [11]
is applied here for transferring multicast membership states between
the previously attached DAR (p-DAR) to a newly attached DAR (n-DAR)
within a DMM domain. The context transfer is either started from the
n-DAR on its own after attachment of the mobile node or initiated by
the p-DAR after being informed by the access network of the planned
handover. Existing DMM proposals assume that for data exchange
between p-DAR and n-DAR a dedicated tunnel already is in place.
Details of the set-up procedure for this tunnel are therefore out of
scope of this document.
Depending on the scenario of multicast application the real-time
delivery of content may be more important than lossless and error-
free transmission. Thus to allow for temporary storage or buffering
at a previous access router during handover and subsequent forwarding
may be advantageous to some file transmission use cases whereas for
real-time video services such as live IPTV the focus is on low delay.
Here only transfer of the MN's subscription context shall be
considered for simplicity reasons.
To decide on a multicast flow quality requirements dedicated flags
may be defined to be stored in and retrieved from the common data
base or policy storage. Deteiled considerations on these parameters
are out of scope of this document.
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2. Conventions and Terminology
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 RFC 2119 [1].
The following terms used in this document are to be interpreted as
defined in existing proxy and client mobility protocols and in future
upcoming Distributed Mobility Management (DMM) protocol
specifications, see e.g. [15]: Distributed Access Router (DAR),
Mobility Data Base (MDB), Mobile Node (MN), Proxy Care-of Address
(Proxy-CoA), Mobile Node Identifier (MN-Identifier), Distributed
Binding Update (DBU), and Distributed Binding Acknowledgement (DBA).
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3. Handover Process
DAR is responsible for detecting the mobile node's movements to and
from the access link and for initiating a per-flow binding
registration either as mobility anchor (primary point of attachment).
In case a MN attaches to the DAR which was already previously
assigned to another (previous or primary) DAR (p-DAR) the new DAR
(n-DAR) tracks the mobile node's movements to and from the access
link and performs signaling of the status to that p-DAR and to a
common MDB. In DMM Multicast, it SHOULD NOT be required for mobile
nodes to initiate re-subscription to multicast channels, and DAR
SHOULD keep multicast membership state for mobile nodes even if they
attach a different DAR during the ongoing session.
For multicast context transfer, an IGMP/MLD-based explicit membership
tracking function [18] MAY be enabled on DAR (whether the DAR behaves
as a router or proxy). The explicit tracking function enables a
router to keep track of downstream multicast membership state created
by downstream hosts attached on the router's link. When a mobile
node attaches to a new network, thanks to the explicit tracking
function, the p-DAR extracts the mobile node's multicast membership
state from complete multicast membership state the p-DAR has
maintained and transmits it to the n-DAR.
The assumed architecture for a DMM-based multicast mobility is shown
in Figure 1.
+--------------------+
| Mobility Data Base |
+--------------------+
/ | \
/ | \
/ | \
/ | \
+--------+ +--------+ + ------+
| DAR1 |______| DAR2 |____| DAR3 |
| = p-DAR|______| = n-DAR| | |
+--------+ +--------+ +-------+
|
+----+
| MN |
+----+
Figure 1: Distributed mobility for flat architecture
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3.1. Multicast Context Transfer Data Format
Multicast Context Transfer Data (M-CTD) is a message used with CXTP
to transfer multicast membership state from p-DAR to n-DAR. The
following information is included in M-CTD to recognize mobile node's
membership state.
1. Receiver address - indicates the address of the MN sending the
Current-State Report.
2. Filter mode - indicates either INCLUDE or EXCLUDE as defined in
[5].
3. Source addresses and multicast addresses - indicates the address
pairs the MN has joined.
The M-CTD message MUST contain the 'A' bit set as defined for the CTD
message format in [10] for to initiate the transmission of a reply
message by the new DAR.
The following information included in a reply to M-CTD (similar to
the CTDR message defined in [10]) is used to request the old DAR to
store still incoming multicast data, to forward them to the new DAR,
and finally to leave the multicast group after successful handover
from n-DAR to p-DAR.
1. Receiver address - indicates the address of the MN sending the
Current-State Report.
2. Flag indicating the p-DAR to start (B) buffering the received
multicast data (in case the new connection is not yet fully set
up), to forward (F) the buffered data after successful handover,
or to leave (L) the multicast groups unless there are still
other active subscriptions for the corresponding groups on the
p-DAR.
3. Source addresses and multicast addresses - indicates the address
pairs the MN has joined.
The M-CTDR message MUST contain the 'S' bit set as defined for the
CTD message format in [10] for to indicate the successful reception
of context data at the new DAR.
3.2. Multicast Context Transfer with MLD Proxy
This section describes the case that DAR operates as an MLD proxy, as
defined in [7] and specified in the base MultiMob solution [12].
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The MLD listener handover with CXTP and MLD proxy shown in Figure 2
is defined as follows.
1. A MN is assumed to be attached to the p-DAR wishing to receive
multicast content and sending the corresponding MLD Report. The
serving p-DAR subscribes to the group as MLD proxy and forwards
the multicast traffic to the MN via the access link. In case
the MN's multicast session is completed while being attached to
p-DAR no corresponding entry into the Mobility Data Base needs
to be created (regular IPv6 routing). However in case the MN
wants to maintain the multicast session (together with ongoing
unicast connections) during movement it either registers the
address configured at the p-DAR as home address, as described in
[21] or the p-DAR has to create a binding entry in the central
MDB as proposed e.g. in [20] or [16].
2. When the MN moves to another DAR with the multicast session
ongoing the p-DAR detects the detachment and subsequently sends
a request to create a Binding Cache Entry for the MN in the MBD,
denoted by BCE Create Request (BC-Req).
3. After attaching a new DAR, the mobile node sends a Router
Solicitation (RS) as specified in [8]. In case the MN shall
remain unaware of any change in connectivity the n-DAR has to
identify the p-DAR address during retrieving the MN's BCE from
the mobile node's MDB e.g. via newly specified Distributed
Binding Update (DBU) and corresponding Acknowledgement (DBA).
n-DAR then sends a request for context transfer (CT-Req) to the
p-DAR as defined in [10]. Since the MN cannot initiate the
related Context Transfer Activate Request (CTAR) message that
may be sent by the MDB. In case the mobile node has the
capability and the chance to signal to the p-DAR the link status
and the potential new DAR address (e.g. as is specified in terms
of Event Services by [9]) the p-DAR will send a CTAR message to
n-DAR on behalf of the mobile node. Alternatively the p-DAR or
the n-DAR may have information on potential DARs in their
vicinity to which such a CTAR or CT-Req message may be
multicasted.
4. p-DAR provides together with the other feature data the
multicast states corresponding to the moving MN-Identifier to
n-DAR. p-DAR utilizes a context transfer protocol to deliver
MN's Policy Profile to n-DAR, and sends Multicast Context
Transfer Data (M-CTD) (defined in Section 3.1) to n-DAR.
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5. If there are multicast channels the MN has subscribed but the
n-DAR has not yet subscribed, n-DAR subscribes via sending
(potentially aggregated) MLD [5][6] Membership Report messages
(i.e. Join) to the corresponding MDB.
6. After successful completion of MN attachment the n-DAR replies
to M-CTD with a Multicast Context Transfer Response message
signalling the handover completion upon which p-DAR may leave
the multicast group in case no other MN attached to p-DAR has
subscribed to that group.
MN p-DAR n-DAR MDB
| | | |
|-MLD Report->|==== MLD Report (aggregated Join) =======>
| | | |
|<------------|<=========== Multicast data ==============
| | | |
Detach | | |
| | | |
| |----- BC-Req ------------------------->|
| | | |
Attach | | |
| | | |
|------------- RS --------------->| |
| | |------- DBU ------>|
| | | |
| | |<-------DBA--------|
| | | |
| |<----- CT-Req -------------------------|
| | | |
| |------ CXTP ------>| |
| | M-CTD | |
| | |=== MLD Report ===>|
| | | |
|<----------- RA -----------------| |
| | | |
| | |<= Multicast data =|
| |<------ CXTP ------| |
| | M-CTDR | |
| | | |
|<-------- Multicast data --------| |
| | | |
| |=== potential MLD Report (leave) =====>|
| | | |
Figure 2: MLD listener handover with CXTP and MLD proxy
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After MN attaches to n-DAR, the forwarded multicast data from p-DAR
will be delivered to the MN immediately. Afterwards the current
multicast data are delivered as received from MDB and the MN's
multicast membership state at the p-DAR is cancelled.
3.3. Multicast Context Transfer with PIM-SM
This section describes the case that DAR operates as a PIM-SM [4]
router, as described in a proposed solution [13].
The MLD listener handover with CXTP and PIM-SM is identical as
described in Section 3.2 except that instead of "MLD report
(aggregated Join)" the DARs will send "PIM Join" messages and that
the "MLD Report (leave)" , to be sent if there are no attached mobile
nodes listening the multicast channels at p-DAR, is replaced by "PIM
Prune" message.
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4. IANA Considerations
This document proposes to extent messages defined by the
experimental Context Transfer Protocol [10] for the sake of
supporting Multicast control. To achieve such a support the Context
Transfer Data (CTD) Message and the Context Transfer Data Reply
(CTDR) Message shall be modified to enable transfer of multicast
related data, i.e. M-CTD and M-CTDR. The such transported data
consist of subscription states and flags indicating specific actions
to the PMIP defined anchor MAG. Such extensions described in sect.
3.1. of this draft may require an allocation process by IANA as
already described in [11].
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5. Security Considerations
Security is an important issue in all kinds of mobile and wireless
communication to protect aspects as described in [22], i.e. both
access security to allow only legitimate nodes to access mobile
multicast service and end-to-end security of signaling messages which
may contain confidential data. As outlined in e.g. [22] sufficiently
strong protection mechanisms mut be applied.
Beside that to our knowledge no new security risks are introduced
with this concept.
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6. Acknowledgements
Many of the specifications described in this document are discussed
and provided by the multimob mailing-list. Detailed comments by Luis
Miguel Contreras Murillo are gratefully acknowledged.
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7. References
7.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to indicate requirement
levels", RFC 2119, March 1997.
[2] Perkins, C, Ed., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[3] Gundavelli, S, Ed., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[4] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[5] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004.
[6] Liu, H., Cao, W., and H. Asaeda, "Lightweight IGMPv3 and MLDv2
Protocols", RFC 5790, February 2010.
[7] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet
Group Management Protocol (IGMP) / Multicast Listener Discovery
(MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")",
RFC 4605, August 2006.
[8] Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet Model: The
Relationship between Links and Subnet Prefixes", RFC 5942,
July 2010.
[9] "IEEE Standard for Local and Metropolitan Area Networks - Part
21: Media Independent Handover Services, IEEE LAN/MAN Std
802.21-2008", January 2009.
7.2. Informative References
[10] Loughney, Ed., J., Nakhjiri, M., Perkins, C., and R. Koodli,
"Context Transfer Protocol (CXTP)", RFC 4067, July 2005.
[11] von Hugo, D. and H. Asaeda, "Context Transfer Protocol
extensions for Multicast",
draft-vonhugo-multimob-cxtp-extension-03.txt (work in
progress), February 2013.
[12] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base Deployment
for Multicast Listener Support in Proxy Mobile IPv6 (PMIPv6)
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Domains", RFC 6224, April 2011.
[13] Asaeda, H. and P. Seite, "Multicast Routing Optimization by
PIM-SM with PMIPv6",
draft-asaeda-multimob-pmip6-extension-11.txt (work in
progress), October 2012.
[14] Schmidt, TC., Waehlisch, M., Koodli, R., Fairhurst, G., and D.
Liu, "Multicast Listener Extensions for MIPv6 and PMIPv6 Fast
Handovers",
draft-ietf-multimob-fmipv6-pfmipv6-multicast-01.txt (work in
progress), February 2013.
[15] Patil, B. (Ed.), Williams, C., and J. Korhonen, "Approaches to
Distributed mobility management using Mobile IPv6 and its
extensions", draft-patil-dmm-issues-and-approaches2dmm-00.txt
(work in progress), March 2012.
[16] Seite, P. and P. Bertin, "Distributed Mobility Anchoring",
draft-seite-dmm-dma-06.txt (work in progress), January 2013.
[17] Liu, D., Song, J., and W. Luo, "PMIP Based Distributed Mobility
Management Appproach",
draft-liu-dmm-pmip-based-approach-02.txt (work in progress),
March 2012.
[18] Asaeda, H., "IGMP/MLD-Based Explicit Membership Tracking
Function for Multicast Routers",
draft-ietf-pim-explicit-tracking-05.txt (work in progress),
February 2013.
[19] Contreras, LM., Bernardos, CJ., and I. Soto, "PMIPv6 multicast
handover optimization by the Subscription Information
Acquisition through the LMA (SIAL)",
draft-ietf-multimob-fast-handover-03.txt (work in progress),
October 2012.
[20] Bernardos, CJ., de la Oliva, A., Giust, F., and T. Melia, "A
PMIPv6-based solution for Distributed Mobility Management",
draft-bernardos-dmm-pmip-01.txt (work in progress), March
2012.
[21] Bernardos, CJ., de la Oliva, A., and F. Giust, "A IPv6
Distributed Client Mobility Management approach using existing
mechanisms", draft-bernardos-mext-dmm-cmip-00.txt (work in
progress), March 2011.
[22] Chan, H. (Ed.) et al., "Requirements of distributed mobility
management", draft-ietf-dmm-requirements-03.txt, (work in
progress), December 2012.
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Authors' Addresses
Dirk von Hugo
Telekom Innovation Laboratories
Deutsche-Telekom-Allee 7
Darmstadt 64295
Germany
Email: Dirk.von-Hugo@telekom.de
Hitoshi Asaeda
National Institute of Information and Communications Technology
Network Architecture Laboratory
4-2-1 Nukui-Kitamachi
Koganei, Tokyo 184-8795
Japan
Email: asaeda@nict.go.jp
Pierrick Seite
France Telecom - Orange
4, rue du Clos Courtel
BP 91226
Cesson-Sevigne 35512
France
Email: pierrick.seite@orange.com
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