DYNAMIC HOST REGISTRATION INTERNET GROUP MANAGEMENT PROTOCOL

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DYNAMIC HOST REGISTRATION -- INTERNET GROUP
MANAGEMENT PROTOCOL

• 2008.07.26
• Yi-Cheng Lin

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Outline

• INTRODUCTION
• IGMP MESSAGES
• IGMPv3 MESSAGES
• IGMP OPERATION
• PROTOCOL DETAILS FOR IGMPv2
• IGMP SNOOPING SWITCHES

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INTRODUCTION

• IGMP is used by host receivers to join or leave a
  multicast host group.
• IGMP is used by IPv4-based receivers.
• The latest version at press time was Version 3.
• IGMPv3 supports receivers that explicitly signal
  sources from which they wish to receive traffic.

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INTRODUCTION

• Specifically, IGMPv3 is employed by hosts to
  signal channel access in SSM (Source Specific
  Multicast ).
• Benefits of SSM
• Optimized access bandwidth utilization
• Risk reduction

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IGMP MESSAGES

• In Version 1 , there are two types of IGMP
  messages MQ and MR.
• IGMPv2 message types are MQ,MR, and Leave Group
  (LG).
• MQ generic (general MQ), specific
  (group-specific MQ).

MQ
router
receiver
MR
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IGMP MESSAGES

• The IGMP messages for IGMPv2

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IGMPv3 MESSAGES

• Version 3 allows receivers to subscribe to or
  exclude a specific set of sources within a
  multicast group, rather than just an individual
  source (this is called, as noted, source specific
  multicast).
• With this feature, IGMPv 3 adds support for
  source filtering.
• IGMPv3 is not widely implemented as of press
  time.

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IGMPv3 MESSAGES

• Receivers signal membership to a multicast host
  group in the following two modes
• INCLUDE mode.
• EXCLUDE mode.
• To support this capability the membership query
  packet (type of 0x11) has been changed in
  addition, a new packet type of 0x22 has been
  added.

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IGMPv3 MESSAGES

• In IGMPv3 there are the following three variants
  of the Query message
• general query
• group-specific query
• group-and-source-specific query

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IGMPv3 MESSAGES

• The Max Resp Code field specifies the maximum
  time allowed before sending a responding report.
• Represented in units of 1/10 s and is derived
  from the maximum response code.
• lt 128, the value of the maximum response time
• Max Resp Code gt128, Max Resp Code represents a
  floating-point

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IGMPv3 MESSAGES

• If Max Resp Code gt 128
• Ex assume that the value of the maximum response
  code is decimal 178.
• 10110010
• Byte 0 1
• Exp 011
• Mant 0010
• The subsequent calculations are
• ( Mant 0x10) (001010000) 10010
• Expt11 011 11 110 (basically, 3 3 6 in
  base 10, or 110 in base 2)
• Therefore, when the maximum response code is
  decimal 178, the maximum response time is 1152
  tenths of a second.

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IGMPv3 MESSAGES

• The QRV field (Queriers Robustness Variable)
  carries a parameter that is used in tuning timer
  values for expected packet loss.
• The QQIC field (Queriers Query Interval Code)
  carries a value specifying the query interval, in
  seconds, used by the originator of this query.
• Number of Sources field indicates how many source
  addresses are contained within the Query message.

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IGMPv3 MESSAGES

• As noted earlier, IGMPv3 adds a new type of 0x22
  to support the IGMPv3 MR.
• MRs are sent by IP systems to report (to
  neighboring routers) the current multicast
  reception state.

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IGMPv3 MESSAGES

• The Record Type field indicates whether the group
  record type is a current-state,
  filter-mode-change, or source-list-change record.
• Version 3 reports are sent with an IP destination
  address of 224.0.0.22, to which all
  IGMPv3-capable multicast routers listen.
• Because of its higher complexity, IGMPv3 is not
  universally supported by all the receiver hosts,
  IGMPv2 is more common, especially in IPTV
  applications

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IGMP OPERATION

• IGMP is an asymmetric protocol.
• Host Operations
• To receive multicast datagrams, a host must join
  a group. To join a group, the host sends an IGMP
  membership report packet through an attached
  interface.

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IGMP OPERATION

• Multicast Router Operations
• Multicast routers listen to all multicast
  addresses to detect membership reports.
• 1. receiver (host) signals to join a group,
• 2. creates an entry in the local group database.
• 3. To verify group membership, multicast routers
  regularly send an IGMP Query message.

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IGMP OPERATION

• Switches Using IGMP Snooping
• IGMP snooping utilizes a router to send out IGMP
  Query messages to identify potentially interested
  receivers.
• Membership reports are returned to the router,
  which builds a mapping table of the group and
  associates forwarding filters for the member
  port.
• If no router is available, some switches can take
  on the query function. RFC 4541 provides
  mechanisms to allow switches to snoop on IGMP
  traffic.
• This reduces the amount of unnecessary multicast
  traffic flooding to locally attached networks
  that have no active receivers.

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IGMP OPERATION

• Figure 4.5 illustrates the process at a
  macrolevel here receivers seek to access a video
  multicast from an IPTV source.

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PROTOCOL DETAILS FOR IGMPv2

• Receiver (Host) State Diagram
• A host may be in one of the following three
  possible states with respect to any single IP
  multicast group on any single network interface

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PROTOCOL DETAILS FOR IGMPv2

• Router State Diagram

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PROTOCOL DETAILS FOR IGMPv2

• In addition, to keep track of which groups have
  members, a router may be in one of the four
  possible states with respect to any single IP
  multicast group on any single attached network.

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PROTOCOL DETAILS FOR IGMPv2
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• Thank you