Internet DRAFT - draft-asaeda-pim-mldproxy-multif
draft-asaeda-pim-mldproxy-multif
PIM Working Group H. Asaeda
Internet-Draft NICT
Expires: August 29, 2013 S. Jeon
Institute de Telecomunicacoes
February 25, 2013
Multiple Upstream Interface Support for IGMP/MLD Proxy
draft-asaeda-pim-mldproxy-multif-01
Abstract
This document describes the way of supporting multiple upstream
interfaces for an IGMP/MLD proxy device. The proposed extension
enables that an IGMP/MLD proxy device receives multicast packets
through multiple upstream interfaces. The upstream interface is
selected with manually configured supported address prefixes and
interface priority value. A take-over operation switching from an
inactive upstream interface to an active upstream interface is also
considered.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Per-Channel Load Balancing . . . . . . . . . . . . . . . . . . 4
4. Candidate Upstream Interface Configuration . . . . . . . . . . 5
4.1. Supported Address Prefix . . . . . . . . . . . . . . . . . 5
4.2. Interface Priority . . . . . . . . . . . . . . . . . . . . 7
4.3. Default Interface . . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
7. Normative References . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
The Internet Group Management Protocol (IGMP) [1][2] for IPv4 and the
Multicast Listener Discovery Protocol (MLD) [3][2] for IPv6 are the
standard protocols for hosts to initiate joining or leaving of
multicast sessions. A proxy device performing IGMP/MLD-based
forwarding (as known as IGMP/MLD proxy) [4] maintains multicast
membership information by IGMP/MLD protocols on the downstream
interfaces and sends IGMP/MLD membership report messages via the
upstream interface to the upstream multicast routers when the
membership information changes (e.g., by receiving solicited/
unsolicited report messages). The proxy device forwards appropriate
multicast packets received on its upstream interface to each
downstream interface based on the downstream interface's
subscriptions.
According to the specification of [4], an IGMP/MLD proxy has *a
single* upstream interface and one or more downstream interfaces.
The multicast forwarding tree must be manually configured by
designating upstream and downstream interfaces on an IGMP/MLD proxy
device, and the root of the tree is expected to be connected to a
wider multicast infrastructure. An IGMP/MLD proxy device hence
performs the router portion of the IGMP or MLD protocol on its
downstream interfaces, and the host portion of IGMP/MLD on its
upstream interface. The proxy device must not perform the router
portion of IGMP/MLD on its upstream interface.
On the other hand, there is a scenario in which an IGMP/MLD proxy
device enables multiple upstream interfaces and receives multicast
packets through these interfaces. For example, a proxy device having
more than one interface may want to access to different networks,
such as Internet and Intranet. Or, a proxy device having wired link
(e.g., ethernet) and high-speed wireless link (e.g., WiMAX or LTE)
may want to have the capability to connect to the Internet through
both links. These proxy devices shall receive multicast packets from
the different upstream interfaces and forward to the downstream
interface(s).
This document adds the way to manually configure candidate upstream
interfaces for an IGMP/MLD proxy device and select "one" single
upstream interface from candidate upstream interfaces per session/
channel. When the selected upstream interface is down or disabled,
one of the other candidate upstream interfaces takes over the
upstream interface (if configured). This enables "per-channel load
balancing".
Note that this document only specifies the way to configure per-
channel load balancing; it does not specify any intelligent
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mechanism/algorithm (e.g., based on link or network condition/usage)
or threshold value to select an upstream interface from candidate
upstream interfaces to improve data reception quality. Also, an
IGMP/MLD proxy device does not select multiple upstream interfaces
for the same channels/sessions simultaneously; enabling redundant
paths to receive duplicate packets via multiple upstream interfaces
to improve data reception quality or robustness for a session/channel
is out of scope of 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 RFC 2119 [5].
In addition, the following terms are used in this document.
Upstream interface (or selected upstream interface):
A proxy device's interface in the direction of the root of the
multicast forwarding tree. An upstream interface is selected by
either manual or automatic configuration.
Downstream interface:
Each of a proxy device's interfaces that is not in the direction of
the root of the multicast forwarding tree.
Candidate upstream interface:
An interface that potentially becomes an upstream interface of the
proxy device. Candidate upstream interfaces are manually set up on
an IGMP/MLD proxy.
Supported address prefix:
The supported address prefix is the address prefix for which a
candidate upstream interface supposes to be an upstream interface.
The supported source address prefix and the supported multicast
address prefix an IGMP/MLD proxy device can configure. The supported
address prefix in this document means both source and multicast
address prefixes, unless otherwise specified.
3. Per-Channel Load Balancing
An IGMP/MLD proxy device enables "per-channel load balancing" using
multiple upstream interfaces to receive different multicast sessions/
channel through the different upstream interfaces. Per-channel load
balancing makes an IGMP/MLD proxy device select "one" single upstream
interface from candidate upstream interfaces per session/channel,
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based on the configurations, which will be described in Section 4.
If an IGMP proxy recognizes that an adjacent upstream router is not
working, the selected upstream interface attached to that router can
be taken over with the different candidate upstream interface. Or,
if the selected upstream interface is going down, the proxy would
switch from the inactive interface to the other active upstream
interface. This "take-over operation" recursively examines the
configurations of the candidate upstream interfaces (except the
disabled interface) and decides a new upstream interface from them.
Whether the upstream router is active or not would be decided by
checking a link condition or IGMP/MLD query message transmission.
However, this document does not describe how an IGMP/MLD proxy can
detect the upstream router's condition and when it takes that
interface over the different candidate upstream interface.
The take-over operation is enabled by default. When it is disabled
(by operation), even if no data comes from the selected upstream
interface, the IGMP/MLD proxy device keeps using that interface as
the upstream interface for the corresponding sessions/channels.
Per-channel load balancing does not implement duplicate packet
reception from redundant paths using multiple upstream interfaces to
improve data reception quality or robustness for a session/channel;
therefore IGMP/MLD report messages containing the same IGMP/MLD
records are not transmitted from different upstream interfaces
simultaneously.
4. Candidate Upstream Interface Configuration
Candidate upstream interfaces are the interfaces from which an IGMP/
MLD proxy device selects as an upstream interface. They are manually
enabled. The upstream interface selection is done based on
"supported address prefix" and "interface priority" value.
4.1. Supported Address Prefix
An IGMP/MLD proxy device MAY configure the "supported address prefix"
for each candidate upstream interface. A proxy selects an upstream
interface from its candidate upstream interfaces based on the
configured supported address prefix. The supported address prefix is
manually configured. The supported address prefix consists of the
following information:
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(source address prefix, multicast address prefix)
When the proxy device transmits an IGMP/MLD report message, it
examines the source and multicast addresses in the IGMP/MLD records
of the report message and transmits the appropriate IGMP/MLD report
message(s) from the selected upstream interface(s) that are
configured with the range of the supported source and multicast
address prefixes.
The default values of both source and multicast address prefixes are
a wildcard. If no address prefix value is configured on a candidate
upstream interface, the default value is implicitly set up for the
candidate upstream interface. The wildcard multicast address prefix
is represented by the entire multicast address range (i.e.,
'224.0.0.0/4' for IPv4 or 'ff00::/8' for IPv6). The wildcard source
address prefix is represented by any host. If the default value is
set up on a candidate upstream interface, the decision whether the
candidate upstream interface is selected as the upstream interface or
not is made by the "interface priority" value described in
Section 4.2.
The same address prefix may be configured on different candidate
upstream interfaces. As well as the above-mentioned default
configuration, when the same address prefix is configured on
different candidate upstream interfaces, an upstream interface for
that address prefix is selected based on each interface priority
value described in Section 4.2.
For upstream interface selection, source address prefix takes
priority over multicast address prefix. This avoids conflict of
upstream interface selection. For example, consider the case that an
IGMP/MLD proxy device has a configuration with source address prefix
S_p for the candidate upstream interface A and multicast address
prefix G_p for the candidate upstream interface B. When it deals with
an IGMP/MLD record whose source address, let's say S, is in the range
of S_p, and whose multicast address, let's say G, is in the range of
G_p, the proxy device selects the candidate upstream interface A,
which supports the source address prefix, as the upstream interface,
and transmits the (S,G) record via the interface A.
Obviously, an IGMP/MLD proxy selects a candidate upstream interface
having supported source and multicast address prefixes that include
both source and multicast address, rather than the other one whose
supported source and multicast address prefixes includes either
source or multicast address.
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4.2. Interface Priority
An IGMP/MLD proxy device MAY configure the "interface priority" value
for each candidate upstream interface. It is an integer value and
manually configured. The default value of the interface priority is
the lowest value.
The interface priority value effects only when the following
conditions are satisfied.
o None of the candidate upstream interfaces configure the supported
address prefix.
o Both source and multicast addresses are included in the supported
address prefixes configured by more than one candidate upstream
interface.
o Neither source nor multicast address is included in the supported
address prefixes configured by any of the candidate upstream
interfaces.
o The supported source address prefix is not configured or does not
include the source address, but (on the other hand) the multicast
address is included in the supported multicast address prefix
configured by more than one candidate upstream interface.
In these conditions, the candidate upstream interface with the
highest priority is chosen as the upstream interface.
4.3. Default Interface
In the following conditions, the candidate upstream interface whose
IPv4/v6 address is lowest is selected as the upstream interface for
that session/channel.
o None of the candidate upstream interfaces configure the supported
address prefix and interface priority value.
o Both source and multicast addresses are included in the supported
address prefixes configured by more than one candidate upstream
interfaces, and these candidate upstream interfaces' priorities
are identical.
o Neither source nor multicast address is included in the supported
address prefixes configured by any of the candidate upstream
interfaces, and all candidate upstream interfaces' priorities are
identical.
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o The supported source address prefix is not configured or does not
include the source address, and the multicast address is included
in the supported multicast address prefix configured by more than
one candidate upstream interface, yet these candidate upstream
interfaces' priorities are identical.
5. IANA Considerations
This document has no actions for IANA.
6. Security Considerations
This document neither provides new functions nor modifies the
standard functions defined in [1][3][2]. Therefore there is no
additional security consideration provided for these protocols.
7. Normative References
[1] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version 3",
RFC 3376, October 2002.
[2] Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet Group
Management Protocol Version 3 (IGMPv3) and Multicast Listener
Discovery Version 2 (MLDv2) Protocols", RFC 5790, February 2010.
[3] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004.
[4] 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.
[5] Bradner, S., "Key words for use in RFCs to indicate requirement
levels", RFC 2119, March 1997.
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Authors' Addresses
Hitoshi Asaeda
National Institute of Information and Communications Technology (NICT)
Network Architecture Laboratory
4-2-1 Nukui-Kitamachi
Koganei, Tokyo 184-8795
Japan
Email: asaeda@nict.go.jp
Seil Jeon
Institute de Telecomunicacoes
Campus Universitario de Santiago
Aveiro 3810-193
Portugal
Email: seiljeon@av.it.pt
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