diff options
Diffstat (limited to 'pimd/CAVEATS')
| -rw-r--r-- | pimd/CAVEATS | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/pimd/CAVEATS b/pimd/CAVEATS new file mode 100644 index 0000000..120708b --- /dev/null +++ b/pimd/CAVEATS @@ -0,0 +1,182 @@ +C1 IGMPv3 backward compatibility with IGMPv1 and IGMPv2 is not + implemented. See RFC 3376, 7.3. Multicast Router Behavior. That's + because only Source-Specific Multicast is currently targeted. + +C2 IGMPv3 support for forwarding any-source groups is not + implemented. Traffic for groups in mode EXCLUDE {empty} won't be + forwarded. See RFC 3376, 6.3. Source-Specific Forwarding + Rules. That's because only Source-Specific Multicast is currently + targeted. + +C3 Load Splitting of IP Multicast Traffic over ECMP is not supported. + See also: RFC 2991 + Multipath Issues in Unicast and Multicast Next-Hop Selection + http://www.rfc-editor.org/rfc/rfc2991.txt + +C4 IPSec AH authentication is not supported (RFC 4601: + 6.3. Authentication Using IPsec). + +C5 PIM support is limited to SSM mode as defined in section 4.8.2 + (PIM-SSM-Only Routers) of RFC4601. That's because only + Source-Specific Multicast is currently targeted. + +C6 PIM implementation currently does not support IPv6. PIM-SSM + requires IGMPv3 for IPv4 and MLDv2 for IPv6. MLDv2 is currently + missing. See also CAVEAT C9. + +C7 FIXED (S,G) Assert state machine (RFC 4601, section 4.6.1) is not + implemented. See also TODO T6. See also CAVEAT C10. + +C8 It is not possible to disable join suppression in order to + explicitly track the join membership of individual downstream + routers. + - IGMPv3 Explicit Membership Tracking is not supported. + When explicit tracking is enabled on a router, the router can + individually track the Internet Group Management Protocol (IGMP) + membership state of all reporting hosts. This feature allows the + router to achieve minimal leave latencies when hosts leave a + multicast group or channel. Example: + conf t + interface eth0 + ip igmp explicit-tracking + +C9 Only IPv4 Address Family (number=1) is supported in the PIM Address + Family field. + See also RFC 4601: 5.1. PIM Address Family + See also CAVEAT C6. + See also http://www.iana.org/assignments/address-family-numbers + +C10 FIXED Assert metric depends on metric_preference and + route_metric. Those parameters should be fetched from RIB + (zebra). See also pim_rpf.c, pim_rpf_update(). + +C11 SSM Mapping is not supported + + SSM Mapping Overview: + + SSM mapping introduces a means for the last hop router to discover + sources sending to groups. When SSM mapping is configured, if a + router receives an IGMPv1 or IGMPv2 membership report for a + particular group G, the router translates this report into one or + more (S, G) channel memberships for the well-known sources + associated with this group. + + When the router receives an IGMPv1 or IGMPv2 membership report for + a group G, the router uses SSM mapping to determine one or more + source IP addresses for the group G. SSM mapping then translates + the membership report as an IGMPv3 report INCLUDE (G, [S1, G], + [S2, G]...[Sn, G] and continues as if it had received an IGMPv3 + report. The router then sends out PIM joins toward (S1, G) to (Sn, + G) and continues to be joined to these groups as long as it + continues to receive the IGMPv1 or IGMPv2 membership reports and + as long as the SSM mapping for the group remains the same. SSM + mapping, thus, enables you to leverage SSM for video delivery to + legacy STBs that do not support IGMPv3 or for applications that do + not take advantage of the IGMPv3 host stack. + + SSM mapping enables the last hop router to determine the source + addresses either by a statically configured table on the router or + by consulting a DNS server. When the statically configured table + is changed, or when the DNS mapping changes, the router will leave + the current sources associated with the joined groups. + +C12 FIXED MRIB for incongruent unicast/multicast topologies is not + supported. RPF mechanism currently just looks up the information + in the unicast routing table. + + See also: + RFC5110: 2.2.3. Issue: Overlapping Unicast/Multicast Topology + + Sometimes, multicast RPF mechanisms first look up the multicast + routing table, or M-RIB ("topology database") with a longest + prefix match algorithm, and if they find any entry (including a + default route), that is used; if no match is found, the unicast + routing table is used instead. + +C13 Can't detect change of primary address before the actual change. + Possible approach is to craft old interface address into ip source + address by using raw ip socket. + + See also: + + RFC 4601: 4.3.1. Sending Hello Messages + + Before an interface goes down or changes primary IP address, a + Hello message with a zero HoldTime should be sent immediately + (with the old IP address if the IP address changed). + + See also pim_sock_delete(). + +C14 FIXED Detection of interface primary address changes may fail when + there are multiple addresses. + See also TODO T32. + +C15 Changes in interface secondary address list are not immediately + detected. + See also detect_secondary_address_change + See also TODO T31. + +C16 AMT Draft (mboned-auto-multicast) is not supported. + AMT = Automatic IP Multicast Without Explicit Tunnels + + See also: + + Draft + http://tools.ietf.org/html/draft-ietf-mboned-auto-multicast + http://tools.ietf.org/html/draft-ietf-mboned-auto-multicast-09 + + AMT gateway implementation for Linux + http://cs.utdallas.edu/amt/ + + AMT for Streaming (IPTV) on Global IP Multicast by Greg Shepherd (Cisco) + http://nznog.miniconf.org/nznog-2008-sysadmin-miniconf-greg-shepherd-iptv.pdf + +C17 SNMP / RFC 5060 (PIM MIB) is not supported. + +C18 MFC never recovers from removal of static route to source + + # route add -host 1.2.3.4 gw 192.168.56.10 + Before removal: + quagga-pimd-router# sh ip mroute + Source Group Proto Input iVifI Output oVifI TTL Uptime + 1.2.3.4 232.1.2.3 I eth1 3 eth0 2 1 00:00:36 + + # route del -host 1.2.3.4 gw 192.168.56.10 + After removal: sh ip mroute --> empty output + + # route add -host 1.2.3.4 gw 192.168.56.10 + After the route is restored: sh ip mroute --> never recovers (empty output) + + At this point, "no ip pim ssm" on the upstream interface (eth0) crashes pimd: + + 2014/02/14 16:30:14 PIM: ifmembership_set: (S,G)=(1.2.3.4,232.1.2.3) membership now is NOINFO on interface eth0 + 2014/02/14 16:30:14 PIM: pim_ifchannel_update_assert_tracking_desired: AssertTrackingDesired(1.2.3.4,232.1.2.3,eth0) changed from 1 to 0 + 2014/02/14 16:30:14 PIM: pim_zebra.c del_oif: nonexistent protocol mask 2 removed OIF eth0 (vif_index=2, min_ttl=0) from channel (S,G)=(1.2.3.4,232.1.2.3) + 2014/02/14 16:30:14 PIM: pim_ifchannel_update_could_assert: CouldAssert(1.2.3.4,232.1.2.3,eth0) changed from 1 to 0 + 2014/02/14 16:30:14 PIM: pim_ifchannel_update_my_assert_metric: my_assert_metric(1.2.3.4,232.1.2.3,eth0) changed from 0,0,0,10.0.2.15 to 1,4294967295,4294967295,0.0.0.0 + 2014/02/14 16:30:14 PIM: pim_zebra.c del_oif: nonexistent protocol mask 1 removed OIF eth0 (vif_index=2, min_ttl=0) from channel (S,G)=(1.2.3.4,232.1.2.3) + 2014/02/14 16:30:14 PIM: Assertion `!IGMP_SOURCE_TEST_FORWARDING(source->source_flags)' failed in file pim_igmpv3.c, line 412, function igmp_source_delete + +C19 Provision to prevent group mode clash + + Beware group mode clash. A host/application issuing IGMPv2 + any-source joins for a group will disrupt SSM multicast for that + group. + + For instance, support for source-specific static igmp WILL FAIL if + there is host/application issuing IGMPv2 any-source joins for the + same group. + + The reason is the IGMPv2 any-source join forces qpimd to switch + the group mode to ASM (any-source multicast); however, qpimd is + unable to program ASM groups into the kernel; multicast won't + flow. There could be some provision to prevent such a behavior, + but currently there is none. + +C20 Multicast traceroute module is based on: + draft-ietf-idmr-traceroute-ipm-07 + It only implements, so far, weak traceroutes. The multicast routing + state of the router is not quieried but RPF path is followed along + PIM and IGMP enabled interfaces. + +-x- |