Extension of the MLD proxy functionality to support multiple upstream interfaces
draft-contreras-multimob-multiple-upstreams-00
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| Last updated | 2012-10-15 | ||
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draft-contreras-multimob-multiple-upstreams-00
MULTIMOB Working Group Luis M. Contreras
INTERNET-DRAFT Telefonica I+D
Intended Status: Proposed Standard Carlos J. Bernardos
Expires: April 18, 2013 Universidad Carlos III de Madrid
October 15, 2012
Extension of the MLD proxy functionality to support multiple
upstream interfaces
draft-contreras-multimob-multiple-upstreams-00
Abstract
This document presents different scenarios of applicability for an
MLD proxy running more than one upstream interface. Since those
scenarios impose different requirements on the MLD proxy with
multiple upstream interfaces, it is important to ensure that the
proxy functionality address all of them for compatibility.
The purpose of this document is to define the requirements in an MLD
proxy with multiple interfaces covering a variety of applicability
scenarios, and to specify the proxy functionality to satisfy all of
them.
Status of this Memo
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Copyright and License Notice
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Problem statement . . . . . . . . . . . . . . . . . . . . . . 4
4. Scenarios of applicability . . . . . . . . . . . . . . . . . . 4
4.1 Applicability to multicast listener mobility . . . . . . . 4
4.1.1 Single MLD proxy instance on MAG . . . . . . . . . . . 4
4.1.1.1 Requirements . . . . . . . . . . . . . . . . . . . 5
4.1.2 Remote and local multicast subscription . . . . . . . . 5
4.1.2.1 Requirements . . . . . . . . . . . . . . . . . . . 6
4.1.3 Dual subscription to multicast groups during handover . 6
4.1.3.1 Requirements . . . . . . . . . . . . . . . . . . . 7
4.2 Applicability to multicast source mobility . . . . . . . . 7
4.2.1 Support of remote and direct subscription in basic
source mobility . . . . . . . . . . . . . . . . . . . . 7
4.2.1.1 Requirements . . . . . . . . . . . . . . . . . . . 8
4.2.2 Direct communication between source and listener
associated with distinct LMAs but on the same MAG . . . 8
4.2.3.1 Requirements . . . . . . . . . . . . . . . . . . . 9
4.2.3 Route optimization support in source mobility for
remote subscribers . . . . . . . . . . . . . . . . . . 9
4.2.3.1 Requirements . . . . . . . . . . . . . . . . . . . 9
4.3 Summary of the requirements needed . . . . . . . . . . . . 10
5 Functional specification of an MLD proxy with multiple
interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6 Security Considerations . . . . . . . . . . . . . . . . . . . . 12
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 12
8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
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10.1 Normative References . . . . . . . . . . . . . . . . . . . 12
10.2 Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1 Introduction
The aim of this document is to specify the functionality that an MLD
proxy with multiple upstream interfaces should have in order to
support a set of different scenarios of applicability that have been
identified on the MULTIMOB working group. Such functional
specification is required to ensure the compatibility of the MLD
proxy instances deployed in PMIPv6 domains.
To do that, a set of requirements are firstly identified to satisfy
the different scenarios where an MLD proxy instance with multiple
upstream interfaces can be potentially applied.
2. Terminology
<To be completed>.
3. Problem statement
The concept of MLD proxy with several upstream interfaces has emerged
within the MULTIMOB working group as a way of optimizing (and in some
cases enabling) service delivery scenarios in both multicast listener
and source mobility cases.
Since those scenarios can motivate distinct needs in terms of MLD
proxy functionality, it is necessary to consider a comprehensive
approach, looking at the possible scenarios, and establishing a
minimum set of requirements which can allow the operation of a
versatile MLD proxy with multiple upstream interfaces as a common
entity to all of them (i.e., no different kinds of proxies depending
on the scenario, but a common proxy applicable to all the potential
scenarios).
4. Scenarios of applicability
The use of an MLD proxy supporting multiple upstream interfaces can
improve the performance and the scalability of multicast-capable
PMIPv6 domains.
4.1 Applicability to multicast listener mobility
Three sub-cases can be identified for the multicast listener
mobility.
4.1.1 Single MLD proxy instance on MAG
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The base solution for multicast service in PMIPv6 [2] assumes that
any MN subscribed to multicast services receive the multicast traffic
through the associated LMA, as in the unicast case. As standard MLD
proxy functionality only supports one upstream interface, the MAG
should implement several separated MLD proxy instances, one per LMA,
in order to serve the multicast traffic to the MNs, according to any
particular LMA-MN association.
A way of avoiding the multiplicity of MLD proxy instance in a MAG is
to deploy a unique MLD proxy instance with multiple upstream
interfaces, one per LMA, without any change in the multicast traffic
distribution.
4.1.1.1 Requirements
These are the requirements identified so far:
- The MLD proxy should be able of delivering the multicast control
messages sent by the MNs to the associated LMA.
- The MLD proxy should be able of delivering the multicast control
messages sent by each of the connected LMAs to the corresponding
MN.
- The MLD proxy should be able of routing the multicast data
coming from different LMAs to the corresponding MNs according to
the MN to LMA association.
- The MLD proxy should be able of maintaining a 1:1 association
between an MN and LMA (or downstream to upstream).
4.1.2 Remote and local multicast subscription
Standard MLD proxy definition, with a unique upstream interface per
proxy, does not allow the reception of multicast traffic from
distinct upstream multicast routers. In other words, all the
multicast traffic being sent to the MLD proxy in downstream traverses
a concrete, unique router before reaching the MAG. There are,
however, situations where different multicast content could reach the
MLD proxy through distinct next-hop routers.
For instance, the solution adopted to avoid the tunnel convergence
problem in basic multicast PMIPv6 deployments [3] considers the
possibility of subscription to a multicast source local to the PMIPv6
domain. In that situation, some multicast content will be accesses
remotely, through the home network via the multicast tree mobility
anchor, while some other multicast content will reach the proxy
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directly, via a local router in the domain.
4.1.2.1 Requirements
These are the requirements identified so far:
- The MLD proxy should be able of delivering the multicast control
messages sent by the MNs to the associated upstream interface
based on the location of the source, remote or local, for a
certain multicast group.
- The MLD proxy should be able of delivering the multicast control
messages sent either local or remotely to the corresponding MNs.
- The MLD proxy should be able of routing the multicast data
coming from different upstream interfaces to a certain MN
according to the MN subscription, either local or remote. Note
that it is assumed that a multicast group can be subscribed either
locally or remotely, but not simultaneously. However more than one
subscription could happen, being local or remote independently.
- The MLD proxy should be able of maintaining a 1:N association
between an MN and the remote and local multicast router (or
downstream to upstream).
- The MLD proxy should be able of switching between local or
remote subscription for per multicast group according to specific
configuration parameters (out of the scope of this document).
4.1.3 Dual subscription to multicast groups during handover
In the event of an MN handover, once an MN moves from a previous MAG
(pMAG) to a new MAG (nMAG), the nMAG needs to set up the multicast
status for the incoming MN, and subscribe the multicast channels it
was receiving before the handover event. The MN will then experience
a certain delay until it receives again the subscribed content.
A generic solution is being defined in [4] to speed up the knowledge
of the ongoing subscription by the nMAG. However, for the particular
case that the underlying radio access technology supports layer-2
triggers (thus requiring extra capabilities on the mobile node),
there could be inter-MAG cooperation for handover support if pMAG and
nMAG are known in advance.
This could be the case, for instance for those contents not already
arriving to the nMAG, where the nMAG temporally subscribes the
multicast groups of the ongoing MN's subscription via the pMAG, while
the multicast delivery tree among the nMAG and the mobility anchor is
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being established.
A similar approach is followed in [5] despite the solution proposed
there differs from this approach (i.e., there is no consideration of
an MLD proxy with multiple interfaces).
4.1.3.1 Requirements
These are the requirements identified so far:
- The MLD proxy should be able of delivering the multicast control
messages sent by the MNs to the associated upstream interface
based on the handover specific moment, for a certain multicast
group.
- The MLD proxy should be able of delivering the multicast control
messages sent either from pMAG or the multicast anchor to the
corresponding MNs, based on the handover specific moment.
- The MLD proxy should be able of handle the incoming packet flows
from the two simultaneous upstream interfaces, in order to not
duplicate traffic delivered on the point-to-point link to the MN.
- The MLD proxy should be able of maintaining a 1:N association
between an MN and both the remote multicast router and the pMAG
(or downstream to upstream).
- The MLD proxy should be able of switching between local or
remote subscription for all the multicast groups (from pMAG to
multicast anchor) according to specific configuration parameters
(out of the scope of this document).
4.2 Applicability to multicast source mobility
A couple of sub-cases can be identified for the multicast source
mobility.
4.2.1 Support of remote and direct subscription in basic source
mobility
In the basic case of source mobility, the multicast source is
connected to one of the downstream interfaces of an MLD proxy.
According to the standard specification [1] every packet sent by the
multicast source will be forwarded towards the root of the multicast
tree.
However, linked to the mobility listener problem, there could be the
case of simultaneous remote subscribers, subscribing to the multicast
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content through the home network, and local subscribers, requesting
the contents directly via a multicast router residing on the same
PMIPv6 domain where the source is attached to.
Then, in order to provide the co-existence of both types of
subscribers, an MLD proxy with two upstream interfaces could
simultaneously serve all kind of multicast subscribers.
Basic source mobility is being defined in [6] but the solution
proposed there does not allow simultaneous co-existence of remote and
local subscribers (i.e., the content sent by the source is either
distributed locally to a multicast router in the PMIPv6 domain, or
remotely by using the bi-directional tunnel towards the mobility
anchor, but not both simultaneously).
4.2.1.1 Requirements
These are the requirements identified so far:
- The MLD proxy should be able of forwarding (replicating) the
multicast content to both upstream interfaces, in case of
simultaneous remote and local distribution.
- The MLD proxy should be able of handling control information
incoming through any of the two upstream interfaces, providing the
expected behavior for each of the multicast trees.
- The MLD proxy should be able of routing the multicast data
towards different upstream interfaces for both remote and local
subscriptions that could happen simultaneously.
- The MLD proxy should be able of maintaining a 1:N association
between an MN and both the remote and local multicast router (or
downstream to upstream).
4.2.2 Direct communication between source and listener associated with
distinct LMAs but on the same MAG
In a certain PMIPv6 domain can be MNs associated to distinct LMAs
using the same MAG to get access to their corresponding home
networks. For multicast communication, according to the base solution
[2], each MN <-> LMA association implies a distinct MLD proxy
instance to be invoked in the MAG.
In these conditions, when a mobile source is serving multicast
content to a mobile listener, both attached to the same MAG but each
of them associated to different LMAs, the multicast flow must
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traverse the PMIPv6 domain from the MAG to the LMA where the source
maintains an association, then from that LMA to the LMA where the
listener is associated to, and finally come back to the same MAG from
where the flow departed. This routing is extremely inefficient.
An MLD proxy with multiple upstream interfaces avoids this behavior
since it allows to invoke a unique MLD proxy instance in the MAG. In
this case, the multicast source can directly communicate with the
multicast listener, without need for delivering the multicast traffic
to the LMAs.
4.2.3.1 Requirements
These are the requirements identified so far:
- The MLD proxy should be able of forwarding (replicating) the
multicast content to different upstream or downstream interfaces
where subscribers are present.
- The MLD proxy should be able of handling control information
incoming through any of the upstream or downstream interfaces
requesting a multicast flow being injected in another downstream
interface.
- The MLD proxy should be able of maintaining a 1:N association
between an MN and any of the upstream or downstream interfaces
demanding the multicast content.
4.2.3 Route optimization support in source mobility for remote
subscribers
Even in a scenario of remote subscription, there could be the case
where both the source and the listener are attached to the same
PMIPv6-Domain (for instance, no possibility of direct routing within
the PMIPv6, or source and listener pertaining to distinct home
networks). In this situation there is a possibility of route
optimization if inter-MAG communication is enabled, in such a way
that the listeners in the PMIPv6 domain are served through the
tunnels between MAGs, while the rest of remote listeners are served
through the mobility anchor.
A multi-upstream MLD proxy would allow the simultaneous delivery of
traffic to such kind of remote listeners.
A similar route optimization approach is proposed in [7].
4.2.3.1 Requirements
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These are the requirements identified so far:
- The MLD proxy should be able of forwarding (replicating) the
multicast content to both kinds of upstream interfaces, inter-MAG
tunnel interfaces and MAG to mobility anchor tunnel interface.
- The MLD proxy should be able of handling control information
incoming through any of the two types of upstream interfaces,
providing the expected behavior for each of the multicast trees
(e.g., no forwarding traffic on one inter-MAG link once there are
not more listeners requesting the content).
- The MLD proxy should be able of routing the multicast data
towards different upstream interfaces for both remote and route
optimized subscriptions that could happen simultaneously.
- The MLD proxy should be able of maintaining a 1:N association
between an MN and both the remote and local MAGs (or downstream to
upstream).
4.3 Summary of the requirements needed
After the previous analysis, a number of different requirements can
be identified by the MLD proxy to support multiple upstream
interfaces. The following table summarizes these requirements.
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+----------------------------------------------------+
| Scenarios |
+--------------------------+-------------------------+
| Mulicast Listener | Mulicast Source |
+---------+--------+--------+--------+--------+--------+-------+
| | Single| Remote | Dual | Direct |Listener| Route |
|Functio- | MLD |& local | subscr.|& remote|& source|optimi.|
|nality | Proxy | subscr.| in HO | subscr.| on MAG | |
| | (4.1.1)|(4.1.2) | (4.1.3)|(4.2.1) |(4.2.2) |(4.2.3)|
+---------+--------+--------+--------+--------+--------+-------+
|Upstream | | | | | | |
|Control | X | X | X | X | X | X |
|Delivery | | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|Downstr. | | | | | | |
|Control | X | X | X | | X | |
|Delivery | | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|Upstream | | | | | | |
|Data | | | | X | | X |
|Delivery | | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|Downstr. | | | | | | |
|Data | X | X | X | | X | |
|Delivery | | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|1:1 MN to| | | | | | |
|upstream | X | | | | | |
|assoc. | | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|1:N MN to| | | | | | |
|upstream | | X | X | X | X | X |
|assoc. | | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|Upstr i/f| | | | | | |
|selection| | X | | | | |
|per group| | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|Upstr i/f| | | | | | |
|selection| | | X | | | |
|all group| | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
|Upstream | | | | | | |
|traffic | | | | X | | X |
|replicat.| | | | | | |
+---------+--------+--------+--------+--------+--------+-------+
Table I. Functionality needed on MLD proxy with multiple
upstream interfaces per application scenario
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5 Functional specification of an MLD proxy with multiple interfaces
<To be completed>.
6 Security Considerations
<To be completed>.
7 IANA Considerations
<IANA considerations text>.
8 Conclusions
Through this document several scenarios of applicability of an MLD
proxy with multiple upstream interfaces have been presented.
<To be completed>.
9 Acknowledgements
The authors thank Stig Venaas for his valuable comments and
suggestions.
The research of Carlos J. Bernardos leading to these results has
received funding from the European Community's Seventh Framework
Programme (FP7-ICT-2009-5) under grant agreement n. 258053 (MEDIEVAL
project), being also partially supported by the Ministry of Science
and Innovation (MICINN) of Spain under the QUARTET project (TIN2009-
13992-C02-01).
10 References
10.1 Normative References
[1] B. Fenner, H. He, B. Haberman, and H. Sandick,"Internet Group
Management Protocol (IGMP) / Multicast Listener Discovery (MLD)-
Based Multicast Forwarding ("IGMP/MLD Proxying")", RFC 4605,
August 2006.
10.2 Informative References
[2] T.C. Schmidt, M. Waehlisch, and S. Krishnan, "A Minimal
Deployment Option for Multicast Listeners in PMIPv6 Domains",
RFC6224, April 2011.
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[3] J.C. Zuniga, L.M. Contreras, C.J. Bernardos, S. Jeon, Y. Kim,
"Multicast Mobility Routing Optimizations for Proxy Mobile
IPv6", work in progress, draft-ietf-multimob-pmipv6-ropt-01,
September 2012.
[4] L.M. Contreras, C.J. Bernardos, I. Soto, "PMIPv6 multicast
handover optimization by the Subscription Information
Acquisition through the LMA (SIAL)", work in progress, draft-
ietf-multimob-fast-handover-01, July 2012.
[5] T.C. Schmidt, M. Waehlisch, R. Koodli, G. Fairhurst, "Multicast
Listener Extensions for MIPv6 and PMIPv6 Fast Handovers", work
in progress, draft-schmidt-multimob-fmipv6-pfmipv6-multicast-06,
May 2012
[6] T.C. Schmidt, S. Gao, H. Zhang, M. Waehlisch, "Mobile Multicast
Sender Support in Proxy Mobile IPv6 (PMIPv6) Domains", work in
progress, draft-ietf-multimob-pmipv6-source-01, July 2012.
[7] J. Liu, W. Luo, "Routes Optimization for Multicast Sender in
Proxy Mobile IPv6 Domain", work in progress, draft-liu-multimob-
pmipv6-multicast-ro-02, July 2012.
Authors' Addresses
Luis M. Contreras
Telefonica I+D
EMail: lmcm@tid.es
Carlos J. Bernardos
Universidad Carlos III de Madrid
EMail: cjbc@it.uc3m.es
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