Multiple Upstream Interface Support for IGMP/MLD Proxy
draft-asaeda-pim-multiif-igmpmldproxy-00

PIM Working Group                                              H. Asaeda
Internet-Draft                                              K. Matsuzono
Expires: September 24, 2015                                         NICT
                                                          March 23, 2015

         Multiple Upstream Interface Support for IGMP/MLD Proxy
                draft-asaeda-pim-multiif-igmpmldproxy-00

Abstract

   This document describes the way of supporting multiple upstream
   interfaces for an IGMP/MLD proxy device.  The proposed extension
   enables an IGMP/MLD proxy device to receive multicast sessions/
   channels through the different upstream interfaces.  The upstream
   interface is selected based on the pre-configured supported address
   prefixes and interface priority value.  A mechanism for upstream
   interface takeover that switches from an inactive upstream interface
   to an active upstream interface is also described.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Upstream Selection Mechanism  . . . . . . . . . . . . . . . .   5
     3.1.  Channel-Based Upstream Selection  . . . . . . . . . . . .   5
     3.2.  Subscriber-Based Upstream Selection . . . . . . . . . . .   5
   4.  Upstream Interface Takeover . . . . . . . . . . . . . . . . .   5
   5.  Candidate Upstream Interface Configuration  . . . . . . . . .   6
     5.1.  Subscriber Address Prefix and Supported Address Prefix  .   7
     5.2.  Interface Priority  . . . . . . . . . . . . . . . . . . .   8
     5.3.  Active Interval . . . . . . . . . . . . . . . . . . . . .   8
     5.4.  Default Upstream Interface  . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The Internet Group Management Protocol (IGMP) [2][4] for IPv4 and the
   Multicast Listener Discovery Protocol (MLD) [3][4] 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) [5] 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 [5], 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

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   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 a global network like the Internet and local-scope networks.
   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 describes the mechanism that makes an IGMP/MLD proxy
   device enable to receive multicast sessions/channels through the
   different upstream interfaces.  The mechanism is configured with
   either "channel-based upstream selection" or "subscriber-based
   upstream selection", or both of them.  By channel-based upstream
   selection, an IGMP/MLD proxy device selects one or multiple upstream
   interface(s) from pre-configured candidate upstream interfaces "per
   channel/session".  By subscriber-based upstream selection, an IGMP/
   MLD proxy device selects one or multiple upstream interface(s) from
   pre-configured candidate upstream interfaces "per subscriber/
   receiver".

   When a proxy device transmits an IGMP/MLD report message, it examines
   the source and multicast addresses in the IGMP/MLD records of the
   report message.  It then transmits the appropriate IGMP/MLD report
   message(s) from the selected upstream interface(s).  When a proxy
   device selects "one" upstream interface from the candidate upstream
   interfaces per session/channel, it enables load balancing per
   session/channel.  When a proxy device selects "more than two"
   upstream interfaces from the candidate upstream interfaces per
   session/channel, it potentially receives duplicate (redundant)
   packets for the session/channel from the different upstream
   interfaces simultaneously and improves the robustness of data
   reception.

   A mechanism for "upstream interface takeover" is also described in
   this document; when the selected upstream interface is going down or
   the state of the link attached to the upstream interface is inactive,
   one of the other active candidate upstream interfaces takes over the
   upstream interface (if configured).  The potential timer values to
   switch from an inactive upstream interface to an active upstream
   interface from a list of candidate upstream interfaces are discussed
   in this document as well.

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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 [1].

   In addition, the following terms are used in this document.

   Selected upstream interface (or simply, upstream interface):
   A proxy device's interface in the direction of the root of the
   multicast forwarding tree.  A proxy device performs the host portion
   of IGMP/MLD on its upstream interfaces.  An upstream interface is
   selected from a list of candidate upstream interfaces.

   Default upstream interface:
   A default upstream interface is the upstream interface for multicast
   sessions/channels for which a proxy device cannot choose other
   interfaces as the upstream interface.  A default upstream interface
   is manually configured.

   Active upstream interface:
   An active upstream interface is the upstream interface that has been
   receiving packets for specific multicast sessions/channels during the
   pre-defined active interval.

   Inactive upstream interface:
   An inactive upstream interface is the interface that has not received
   packets for specific multicast sessions/channels during the pre-
   defined active interval.

   Downstream interface:
   Each of a proxy device's interfaces that is not in the direction of
   the root of the multicast forwarding tree.  A proxy device performs
   the router portion of IGMP/MLD on its downstream interfaces.

   Candidate upstream interface:
   An interface that potentially becomes an upstream interface of the
   proxy device.  A list of candidate upstream interfaces with supported
   address prefixes is manually configured on an IGMP/MLD proxy device.

   Supported address prefix:
   The supported address prefix is the address prefix for which a
   candidate upstream interface supposes to be an upstream interface for
   specified multicast sessions/channels.  The supported source address
   prefix and the supported multicast address prefix an IGMP/MLD proxy
   device can configure.

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3.  Upstream Selection Mechanism

3.1.  Channel-Based Upstream Selection

   Channel-based upstream selection enables a proxy device to use one or
   multiple upstream interface(s) per session/channel from the
   "candidate upstream interfaces" based on the "supported address
   prefix" configuration (as will be in Section 5.1).

   A proxy device 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.

   When more than one candidate upstream interfaces are configured with
   the same source and multicast addresses as the supported address
   prefixes and the interface priority values are identical, these
   candidate upstream interfaces act as the upstream interfaces for the
   sessions/channels and receive the packets simultaneously.  This
   multiple upstream interface selection implements duplicate packet
   reception from redundant paths.  It may improve data reception
   quality or robustness for a session/channel, as the same multicast
   data packets can come from different upstream interfaces
   simultaneously.  However, this configuration does not guarantee that
   the packets come from disjoint paths.  It only configures that the
   adjacent upstream routers are different.

3.2.  Subscriber-Based Upstream Selection

   Subscriber-based upstream selection enables a proxy device to use one
   or multiple upstream interface(s) per session/channel from the
   "candidate upstream interfaces" based on the "subscriber address
   prefix" configuration (as will be in Section 5.1).

   It is also possible to configure both supported address prefix
   (described in Section 3.1) and subscriber address prefix.  If both
   prefixes are configured, the configuration of subscriber address
   prefix is prioritized.

4.  Upstream Interface Takeover

   If a selected upstream interface is going down or inactive, or an
   adjacent upstream router is not working, the upstream interface can
   be disabled and the other active upstream interface listed in the
   candidate upstream interfaces covering the same supported address
   prefix can act as a new upstream interface.  It recursively examines
   the list of the candidate upstream interfaces (except the disabled

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   interface) and decides a new upstream interface from them.  If no
   active candidate upstream interfaces exist, the default upstream
   interface takes its role.

   This function called "upstream interface takeover" is a default
   function for a proxy device that enables multiple upstream interface
   support.  If a proxy device simultaneously uses more than two
   upstream interfaces per session/channel, and one or some of these
   upstream interface(s) is/are inactive, the proxy device acts either
   of the following behaviors based on the configuration; (1) it only
   uses the active upstream interface(s) and does not add (i.e.,
   complement) other upstream interfaces, (2) it uses the active
   upstream interface(s) and another candidate upstream interface whose
   priority is highest among the configured upstream interfaces, or (3)
   it uses the active upstream interface(s) and the default upstream
   interface.

   The condition whether the upstream adjacent router is active or not
   can be decided by checking the link/interface condition on the proxy
   device or detected by monitoring IGMP/MLD Query or PIM [6] Hello
   message reception on the link.  There are the cases that PIM is not
   running on the link or IGMP/MLD Query messages are not transmitted by
   the upstream router (e.g., because of enabling the explicit tracking
   function [7]).  Therefore, network operators MUST configure either;
   (1) the proxy device disables the upstream interface takeover, (2)
   the proxy device triggers upstream interface takeover by detecting no
   IGMP/MLD Query message within the active interval, or (3) the proxy
   device triggers upstream interface takeover by detecting no PIM Hello
   message within the active interval, for each candidate upstream
   interface.

   Network operators may want to keep out of use for the inactive
   upstream interface(s).  This causes, for example, when subscriber-
   based upstream selection is configured, according to their accounting
   policy (because the specific subscribers are planned to use the
   specific upstream interface and cannot receive packets from other
   upstream interfaces.)  In that case, this upstream interface takeover
   must be disabled, and the proxy device keeps using that interface as
   the upstream interface for them (and waits for working the interface
   later again).

5.  Candidate Upstream Interface Configuration

   Candidate upstream interfaces are the interfaces from which an IGMP/
   MLD proxy device selects as an upstream interface.  The upstream
   interface selection works with the configurations of "subscriber
   address prefix and supported address prefix" and "interface priority"
   value.

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5.1.  Subscriber Address Prefix and Supported Address Prefix

   An IGMP/MLD proxy device can configure the "subscriber address
   prefix" and "supported address prefix" for each candidate upstream
   interface.  A proxy selects an upstream interface from its candidate
   upstream interfaces based on the configuration below:

      (subscriber address prefix, source address prefix, multicast
      address prefix)

   If network operators want to select specific upstream interface(s)
   without depending on subscriber address prefix, subscriber address
   prefix in this record is "null".  If network operators want to assign
   a specific upstream interface for specific subscribers without
   depending on source and multicast address prefixes, both source and
   multicast addresses in this record is "null".

   The default values of subscriber address prefix and both source and
   multicast address prefixes are "null".  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 5.2.

   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.

   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 5.2.

   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

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   interface A, which supports the source address prefix, as the
   upstream interface, and transmits the (S,G) record via the interface
   A.

5.2.  Interface Priority

   An IGMP/MLD proxy device can 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 either of the
   following conditions is 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 for more than one candidate upstream interface.

   o  Neither source nor multicast address is included in the supported
      address prefixes for 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 for
      more than one candidate upstream interface.

   In these conditions, the candidate upstream interface with the
   highest priority is chosen as the upstream interface.  And as stated
   in Section 3.1, if the priority values for candidate upstream
   interfaces are identical, all of these interfaces act as the upstream
   interfaces for the supported address prefix and may receive duplicate
   packets.

5.3.  Active Interval

   Active interval is a period, after which a proxy device recognizes
   that the selected upstream interface is inactive.  Active interval
   for each candidate upstream interface SHOULD be configured.  The
   active interval values are different in the situation whether the
   network operators want to trigger by either IGMP/MLD or PIM messages.
   The default active interval to detect an inactive upstream interface
   is around twice of IGMP/MLD General Query interval and PIM Hello
   interval.  [TBD]

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5.4.  Default Upstream Interface

   An IGMP/MLD proxy device SHOULD configure "a default upstream
   interface" for all incoming sessions/channels.  A default upstream
   interface is selected as the upstream interface, when none of the
   candidate upstream interfaces configure the supported address prefix
   and interface priority value, or with either of the following
   conditions.

   o  Neither source nor multicast address is included in the supported
      address prefixes for any of the candidate upstream interfaces, and
      all candidate upstream interfaces' priorities are identical.

   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 for more than one
      candidate upstream interface, yet these candidate upstream
      interfaces' priorities are identical.

   If a default upstream interface is not configured on an IGMP/MLD
   proxy device, the candidate upstream interface whose IPv4/v6 address
   is the highest of others is configured as the default upstream
   interface for the proxy device.

6.  IANA Considerations

   This document has no actions for IANA.

7.  Security Considerations

   This document neither provides new functions nor modifies the
   standard functions defined in [2][3][4]; hence there is no additional
   security consideration provided for these protocols themselves.  On
   the other hand, it may be possible to encounter DoS attacks to make
   the function for upstream interface takeover stop if attackers
   illegally sends IGMP/MLD Query or PIM Hello messages on a LAN within
   a shorter period (i.e., before expiring the active interval for the
   upstream interface).  To bypass such threats, it is recommended to
   capture the source addresses of IGMP/MLD Query or PIM Hello message
   senders and check whether the addresses correspond to the correct
   adjacent upstream routers.

8.  References

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8.1.  Normative References

   [1]        Bradner, S., "Key words for use in RFCs to indicate
              requirement levels", RFC 2119, March 1997.

   [2]        Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
              Thyagarajan, "Internet Group Management Protocol, Version
              3", RFC 3376, October 2002.

   [3]        Vida, R. and L. Costa, "Multicast Listener Discovery
              Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

   [4]        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.

   [5]        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.

   [6]        Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
              "Protocol Independent Multicast - Sparse Mode (PIM-SM):
              Protocol Specification (Revised)", RFC 4601, August 2006.

8.2.  Informative References

   [7]        Asaeda, H., "IGMP/MLD-Based Explicit Membership Tracking
              Function for Multicast Routers", draft-ietf-pim-explicit-
              tracking-11 (work-in-progress), March 2015.

Authors' Addresses

   Hitoshi Asaeda
   National Institute of Information and Communications Technology
   Network Research Headquarters
   4-2-1 Nukui-Kitamachi
   Koganei, Tokyo  184-8795
   Japan

   Email: asaeda@nict.go.jp

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   Kazuhisa Matsuzono
   National Institute of Information and Communications Technology
   Network Architecture Laboratory
   4-2-1 Nukui-Kitamachi
   Koganei, Tokyo  184-8795
   Japan

   Email: matsuzono@nict.go.jp

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