Internet DRAFT - draft-contreras-pim-multiple-upstreams-reqs
draft-contreras-pim-multiple-upstreams-reqs
PIM Working Group LM. Contreras
Internet-Draft Telefonica
Intended status: Experimental CJ. Bernardos
Expires: September 8, 2015 Universidad Carlos III de Madrid
March 7, 2015
Requiremnets for the extension of the MLD proxy functionality to support
multiple upstream interfaces
draft-contreras-pim-multiple-upstreams-reqs-00
Abstract
The purpose of this document is to define the requirements for a MLD
proxy with multiple interfaces covering a variety of applicability
scenarios.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Problem statement . . . . . . . . . . . . . . . . . . . . . . 3
4. Scenarios of applicability . . . . . . . . . . . . . . . . . 4
4.1. Fixed network scenarios . . . . . . . . . . . . . . . . . 5
4.1.1. Multicast wholesale offer for residential services . 5
4.1.1.1. Requirements . . . . . . . . . . . . . . . . . . 5
4.1.2. Multicast resiliency . . . . . . . . . . . . . . . . 5
4.1.2.1. Requirements . . . . . . . . . . . . . . . . . . 6
4.1.3. Load balancing for multicast traffic in the metro
segment . . . . . . . . . . . . . . . . . . . . . . . 6
4.1.3.1. Requirements . . . . . . . . . . . . . . . . . . 6
4.1.4. Summary of the requirements needed for fixed network
scenarios . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Mobile network scenarios . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The aim of this document is to define the functionality that an MLD
proxy with multiple upstream interfaces should have in order to
support different scenarios of applicability in both fixed and mobile
networks. This compatibility is needed in order to simplify node
functionality and to ensure an easier deployment of multicast
capabilities in all the use cases described in this document.
2. 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 RFC2119 [RFC2119].
This document uses the terminology defined in RFC4605 [RFC4605].
Specifically, the definition of Upstream and Downstream interfaces,
which are reproduced here for completeness.
Upstream interface: A proxy device's interface in the direction of
the root of the tree. Also called the "Host interface".
Downstream interface: Each of a proxy device's interfaces that is
not in the direction of the root of the tree. Also called the
"Router interfaces".
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3. Problem statement
The concept of MLD proxy with several upstream interfaces has emerged
as a way of optimizing (and in some cases enabling) service delivery
scenarios where separate multicast service providers are reachable
through the same access network infrastructure. Figure 1 presents
the conceptual model under consideration.
downstream upstream
interface interface A
| |
| | _______________
| +-------+ v / \
| | O-------( Multicast Set 1 )
+----------+ v | MLD | \_______________/
| Listener |------| | _______________
+----------+ | Proxy | / \
| O-------( Multicast Set 2 )
+-------+ ^ \_______________/
|
|
upstream
interface B
Figure 1: Concept of MLD proxy with multiple upstream interfaces
The current version of the document is focused on fixed network
scenarios. Mobile network scenarios will be covered in future
versions.
In the case of fixed networks, multicast wholesale services in a
competitive residential market require an efficient distribution of
multicast traffic from different operators or content providers, i.e.
the incumbent operator and a number of alternative providers, on the
network infrastructure of the former. Existing proposals are based
on the use of PIM routing from the metro/core network, and multicast
traffic aggregation on the same tree. A different approach could be
achieved with the use of an MLD proxy with multiple upstream
interfaces, each of them pointing to a distinct multicast router in
the metro/core border which is part of separated multicast trees deep
in the network. Figure 2 graphically describes this scenario.
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downstream upstream
interface interface A
| |
| | _______________
| +--------+ v / \
| | O-------( Multicast Set 1 )
| | Aggr. | \_______________/
+----+ v | Switch | (e.g. from the Incumbent
| AN |-------| | Operator)
+----+ | (MLD | _______________
(e.g. | Proxy) | / \
DSLAM | O-------( Multicast Set 2 )
/OLT) +--------+ ^ \_______________/
| (e.g. from an Alternative
| Provider)
|
upstream
interface B
Figure 2: Example of usage of an MLD proxy with multiple upstream
interfaces in a fixed network scenario
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
Having multiple upstream interfaces creates a new decision space for
delivering the proper multicast content to the subscriber. Basically
it is now possible to implement channel-based or subscriber-based
upstream selection, according to mechanisms or policies that could be
defined for the multicast service provision.
This section describes in detail a number of scenarios of
applicability of an MLD proxy with multiple upstream interfaces in
place. A number of requirements for the MLD proxy functionality are
identified from those scenarios.
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4.1. Fixed network scenarios
Residential broadband users get access to multiple IP services
through fixed network infrastructures. End user's equipment is
connected to an access node, and the traffic of a number of access
nodes is collected in aggregation switches.
For the multicast service, the use of an MLD proxy with multiple
upstream interfaces in those switches can provide service flexibility
in a lightweight and simpler manner if compared with PIM-routing
based alternatives.
4.1.1. Multicast wholesale offer for residential services
This scenario has been already introduced in the previous section,
and can be seen in Figure 2. There are two different operators, the
one operating the fixed network where the end user is connected
(e.g., typically an incumbent operator), and the one providing the
Internet service to the end user (e.g., an alternative Internet
service provider). Both can offer multicast streams that can be
subscribed by the end user, independently of which provider
contributes with the content.
Note that it is assumed that both providers offer distinct multicast
groups. However, more than one subscription to multicast channels of
different providers could take place simultaneously.
4.1.1.1. Requirements
o The MLD proxy should be able to deliver multicast control messages
sent by the end user to the corresponding provider's multicast
router.
o The MLD proxy should be able to deliver multicast control messages
sent by each of the providers to the corresponding end user.
4.1.2. Multicast resiliency
In current PIM-based solutions, the resiliency of the multicast
distribution relays on the routing capabilities provided by protocols
like PIM and VRRP. A simpler scheme could be achieved by
implementing different upstream interfaces on MLD proxies, providing
path diversity through the connection to distinct leaves of a given
multicast tree.
It is assumed that only one of the upstream interfaces is active in
receiving the multicast content, while the other is up and in standby
mode for fast switching.
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4.1.2.1. Requirements
o The MLD proxy should be able to deliver multicast control messages
sent by the end user to the corresponding active upstream
interface.
o The MLD proxy should be able to deliver multicast control messages
received in the active upstream to the end users, while ignoring
the control messages of the standby upstream interface.
o The MLD proxy should be able of rapidly switching from the active
to the standby upstream interface in case of network failure,
transparently to the end user.
4.1.3. Load balancing for multicast traffic in the metro segment
A single upstream interface in existing MLD proxy functionality
typically forces the distribution of all the channels on the same
path in the last segment of the network. Multiple upstream
interfaces could naturally split the demand, alleviating the
bandwidth requirements in the metro segment.
4.1.3.1. Requirements
o The MLD proxy should be able to deliver multicast control messages
sent by the end user to the corresponding multicast router which
provides the channel of interest.
o The MLD proxy should be able to deliver multicast control messages
sent by each of the multicast routers to the corresponding end
user.
o The MLD proxy should be able to decide which upstream interface is
selected for any new channel request according to defined criteria
(e.g., load balancing).
4.1.4. Summary of the requirements needed for fixed network scenarios
Following the analysis above, a number of different requirements can
be identified by the MLD proxy to support multiple upstream
interfaces in fixed network scenarios. The following table
summarizes these requirements.
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+-----------------------------------+
| Fixed Network Scenarios |
+---------+-----------+-----------+-----------+
|Functio- | Multicast | Multicast | Load |
|nality | Wholesale | Resiliency| Balancing |
+---------+-----------+-----------+-----------+
|Upstream | | | |
|Control | X | X | X |
|Delivery | | | |
+---------+-----------+-----------+-----------+
|Downstr. | | | |
|Control | X | X | X |
|Delivery | | | |
+---------+-----------+-----------+-----------+
|Active / | | | |
|Standby | | X | |
|Upstream | | | |
+---------+-----------+-----------+-----------+
|Upstr i/f| | | |
|selection| | | X |
|per group| | | |
+---------+-----------+-----------+-----------+
|Upstr i/f| | | |
|selection| | X | |
|all group| | | |
+---------+-----------+-----------+-----------+
Figure 3: Functionality needed on MLD proxy with multiple upstream
interfaces per application scenario in fixed networks
4.2. Mobile network scenarios
To be done.
5. Security Considerations
To be completed
6. IANA Considerations
To be completed
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC4605] 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.
Authors' Addresses
Luis M. Contreras
Telefonica
Ronda de la Comunicacion, s/n
Sur-3 building, 3rd floor
Madrid 28050
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
URI: http://people.tid.es/LuisM.Contreras/
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
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