CAVEATS 5.5 KB

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  1. # $QuaggaId: $Format:%an, %ai, %h$ $
  2. C1 IGMPv3 backward compatibility with IGMPv1 and IGMPv2 is not
  3. implemented. See RFC 3376, 7.3. Multicast Router Behavior. That's
  4. because only Source-Specific Multicast is currently targeted.
  5. C2 IGMPv3 support for forwarding any-source groups is not
  6. implemented. Traffic for groups in mode EXCLUDE {empty} won't be
  7. forwarded. See RFC 3376, 6.3. Source-Specific Forwarding
  8. Rules. That's because only Source-Specific Multicast is currently
  9. targeted.
  10. C3 Load Splitting of IP Multicast Traffic over ECMP is not supported.
  11. See also: RFC 2991
  12. Multipath Issues in Unicast and Multicast Next-Hop Selection
  13. http://www.rfc-editor.org/rfc/rfc2991.txt
  14. C4 IPSec AH authentication is not supported (RFC 4601:
  15. 6.3. Authentication Using IPsec).
  16. C5 PIM support is limited to SSM mode as defined in section 4.8.2
  17. (PIM-SSM-Only Routers) of RFC4601. That's because only
  18. Source-Specific Multicast is currently targeted.
  19. C6 PIM implementation currently does not support IPv6. PIM-SSM
  20. requires IGMPv3 for IPv4 and MLDv2 for IPv6. MLDv2 is currently
  21. missing. See also CAVEAT C9.
  22. C7 (S,G) Assert state machine (RFC 4601, section 4.6.1) is not
  23. implemented. See also TODO T6. See also CAVEAT C10.
  24. C8 It is not possible to disable join suppression in order to
  25. explicitly track the join membership of individual downstream
  26. routers.
  27. - IGMPv3 Explicit Membership Tracking is not supported.
  28. When explicit tracking is enabled on a router, the router can
  29. individually track the Internet Group Management Protocol (IGMP)
  30. membership state of all reporting hosts. This feature allows the
  31. router to achieve minimal leave latencies when hosts leave a
  32. multicast group or channel. Example:
  33. conf t
  34. interface eth0
  35. ip igmp explicit-tracking
  36. C9 Only IPv4 Address Family (number=1) is supported in the PIM Address
  37. Family field.
  38. See also RFC 4601: 5.1. PIM Address Family
  39. See also CAVEAT C6.
  40. See also http://www.iana.org/assignments/address-family-numbers
  41. C10 FIXED Assert metric depends on metric_preference and
  42. route_metric. Those parameters should be fetched from RIB
  43. (zebra). See also pim_rpf.c, pim_rpf_update().
  44. C11 SSM Mapping is not supported
  45. SSM Mapping Overview:
  46. SSM mapping introduces a means for the last hop router to discover
  47. sources sending to groups. When SSM mapping is configured, if a
  48. router receives an IGMPv1 or IGMPv2 membership report for a
  49. particular group G, the router translates this report into one or
  50. more (S, G) channel memberships for the well-known sources
  51. associated with this group.
  52. When the router receives an IGMPv1 or IGMPv2 membership report for
  53. a group G, the router uses SSM mapping to determine one or more
  54. source IP addresses for the group G. SSM mapping then translates
  55. the membership report as an IGMPv3 report INCLUDE (G, [S1, G],
  56. [S2, G]...[Sn, G] and continues as if it had received an IGMPv3
  57. report. The router then sends out PIM joins toward (S1, G) to (Sn,
  58. G) and continues to be joined to these groups as long as it
  59. continues to receive the IGMPv1 or IGMPv2 membership reports and
  60. as long as the SSM mapping for the group remains the same. SSM
  61. mapping, thus, enables you to leverage SSM for video delivery to
  62. legacy STBs that do not support IGMPv3 or for applications that do
  63. not take advantage of the IGMPv3 host stack.
  64. SSM mapping enables the last hop router to determine the source
  65. addresses either by a statically configured table on the router or
  66. by consulting a DNS server. When the statically configured table
  67. is changed, or when the DNS mapping changes, the router will leave
  68. the current sources associated with the joined groups.
  69. C12 MRIB for incongruent unicast/multicast topologies is not supported.
  70. RPF mechanism currently just looks up the information in the
  71. unicast routing table.
  72. See also:
  73. RFC5110: 2.2.3. Issue: Overlapping Unicast/Multicast Topology
  74. Sometimes, multicast RPF mechanisms first look up the multicast
  75. routing table, or M-RIB ("topology database") with a longest
  76. prefix match algorithm, and if they find any entry (including a
  77. default route), that is used; if no match is found, the unicast
  78. routing table is used instead.
  79. C13 Can't detect change of primary address before the actual change.
  80. Possible approach is to craft old interface address into ip source
  81. address by using raw ip socket.
  82. See also:
  83. RFC 4601: 4.3.1. Sending Hello Messages
  84. Before an interface goes down or changes primary IP address, a
  85. Hello message with a zero HoldTime should be sent immediately
  86. (with the old IP address if the IP address changed).
  87. See also pim_sock_delete().
  88. C14 Detection of interface primary address changes may fail when there
  89. are multiple addresses.
  90. See also TODO T32.
  91. C15 Changes in interface secondary address list are not immediately
  92. detected.
  93. See also TODO T31.
  94. C16 AMT Draft (mboned-auto-multicast) is not supported.
  95. AMT = Automatic IP Multicast Without Explicit Tunnels
  96. See also:
  97. Draft
  98. http://tools.ietf.org/html/draft-ietf-mboned-auto-multicast
  99. http://tools.ietf.org/html/draft-ietf-mboned-auto-multicast-09
  100. AMT gateway implementation for Linux
  101. http://cs.utdallas.edu/amt/
  102. AMT for Streaming (IPTV) on Global IP Multicast by Greg Shepherd (Cisco)
  103. http://nznog.miniconf.org/nznog-2008-sysadmin-miniconf-greg-shepherd-iptv.pdf
  104. C17 SNMP / RFC 5060 (PIM MIB) is not supported.
  105. -x-