DYNAMIC HOST REGISTRATION INTERNET GROUP MANAGEMENT PROTOCOL - PowerPoint PPT Presentation

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DYNAMIC HOST REGISTRATION INTERNET GROUP MANAGEMENT PROTOCOL

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Title: DYNAMIC HOST REGISTRATION INTERNET GROUP MANAGEMENT PROTOCOL


1
DYNAMIC HOST REGISTRATION -- INTERNET GROUP
MANAGEMENT PROTOCOL
  • 2008.07.26
  • Yi-Cheng Lin

2
Outline
  • INTRODUCTION
  • IGMP MESSAGES
  • IGMPv3 MESSAGES
  • IGMP OPERATION
  • PROTOCOL DETAILS FOR IGMPv2
  • IGMP SNOOPING SWITCHES

3
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.

4
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

5
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
6
IGMP MESSAGES
  • The IGMP messages for IGMPv2

7
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.

8
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.

9
IGMPv3 MESSAGES
  • In IGMPv3 there are the following three variants
    of the Query message
  • general query
  • group-specific query
  • group-and-source-specific query

10
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

11
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.

12
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.

13
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.

14
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

15
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.

16
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.

17
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.

18
IGMP OPERATION
  • Figure 4.5 illustrates the process at a
    macrolevel here receivers seek to access a video
    multicast from an IPTV source.

19
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

20
PROTOCOL DETAILS FOR IGMPv2
  • Router State Diagram

21
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.

22
PROTOCOL DETAILS FOR IGMPv2
23
  • Thank you
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