RFC 1584 (rfc1584) - Page 2 of 102

Multicast Extensions to OSPF

RFC 1584              Multicast Extensions to OSPF            March 1994


Table of Contents

    1       Introduction ........................................... 4
    1.1     Terminology ............................................ 5
    1.2     Acknowledgments ........................................ 6
    2       Multicast routing in MOSPF ............................. 6
    2.1     Routing characteristics ................................ 6
    2.2     Sample path of a multicast datagram .................... 8
    2.3     MOSPF forwarding mechanism ............................ 10
    2.3.1   IGMP interface: the local group database .............. 10
    2.3.2   A datagram's shortest-path tree ....................... 14
    2.3.3   Support for Non-broadcast networks .................... 16
    2.3.4   Details concerning forwarding cache entries ........... 16
    3       Inter-area multicasting ............................... 18
    3.1     Extent of group-membership-LSAs ....................... 19
    3.2     Building inter-area datagram shortest-path trees ...... 22
    4       Inter-AS multicasting ................................. 27
    4.1     Building inter-AS datagram shortest-path trees ........ 28
    4.2     Stub area behavior .................................... 30
    4.3     Inter-AS multicasting in a core Autonomous System ..... 31
    5       Modelling internal group membership ................... 31
    6       Additional capabilities ............................... 33
    6.1     Mixing with non-multicast routers ..................... 34
    6.2     TOS-based multicast ................................... 35
    6.3     Assigning multiple IP networks to a physical network .. 36
    6.4     Networks on Autonomous System boundaries .............. 37
    6.5     Recommended system configuration ...................... 38
    7       Basic implementation requirements ..................... 40
    8       Protocol data structures .............................. 40
    8.1     Additions to the OSPF area structure .................. 41
    8.2     Additions to the OSPF interface structure ............. 42
    8.3     Additions to the OSPF neighbor structure .............. 43
    8.4     The local group database .............................. 43
    8.5     The forwarding cache .................................. 44
    9       Interaction with the IGMP protocol .................... 45
    9.1     Sending IGMP Host Membership Queries .................. 46
    9.2     Receiving IGMP Host Membership Reports ................ 46
    9.3     Aging local group database entries .................... 47
    9.4     Receiving IGMP Host Membership Queries ................ 47
    10      Group-membership-LSAs ................................. 48
    10.1    Constructing group-membership-LSAs .................... 49
    10.2    Flooding group-membership-LSAs ........................ 52
    11      Detailed description of multicast datagram forwarding . 52
    11.1    Associating a MOSPF interface with a received datagram  55
    11.2    Locating the source network ........................... 55
    11.3    Forwarding locally originated multicasts .............. 57
    12      Construction of forwarding cache entries .............. 58
    12.1    The Vertex data structure ............................. 59



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