【正文】 memberships are satisfied. This filtermode may change in response to the reception of particular types of group records or when certain timer conditions occur. Conceptually, when a group record is received, the router filtermode for that group is updated to cover all the requested sources using the least amount of state. As a rule, once a group record with a filter mode of EXCLUDE is received, the router filtermode for that group will be EXCLUDE. Alberto Ornaghi 2022 38 IGMP v3 The protocol (for multicast routers) Action on Reception of Reports Reception of CurrentState Records When receiving CurrentState Records, a router updates both its group and source timers. In some circumstances, the reception of a type of group record will cause the router filtermode for that group to change. Reception of FilterMode and SourceList Change Records When a change in the global state of a group occurs in a system, the system sends either a SourceListChange Record or a FilterModeChange Record for that group. As with CurrentState Records, routers must act upon these records and possibly change their own state to reflect the new desired membership state of the work. Alberto Ornaghi 2022 39 IGMP v3 The protocol (for multicast routers) Action on Reception of Queries ? Timer Updates ? Querier Election IGMPv3 elects a single querier per sub using the same querier election mechanism as IGMPv2, namely by IP address. If a router receives an older version query, it MUST use the oldest version of IGMP on the work. Alberto Ornaghi 2022 40 IGMP v3 Interoperation with older version IGMP version 3 hosts and routers interoperate with hosts and routers that have not yet been upgraded to IGMPv3. This patibility is maintained by hosts and routers taking appropriate actions depending on the versions of IGMP operating on hosts and routers within a work. The IGMP version of a Membership Query message is determined as follows: IGMPv1 Query: length = 8 octets AND Max Resp Code field is zero IGMPv2 Query: length = 8 octets AND Max Resp Code field is nonzero IGMPv3 Query: length = 12 octets Alberto Ornaghi 2022 41 IGMP v3 Interoperation with older version Group Member Behavior In the Presence of Older Version Queriers In order to be patible with older version routers, IGMPv3 hosts MUST operate in version 1 and version 2 patibility modes. IGMPv3 hosts MUST keep state per local interface regarding the patibility mode of each attached work. A host39。s Query Interval Code field specifies the [Query Interval] used by the querier. The Number of Sources (N) field specifies how many source addresses are present in the Query. The Source Address [i] fields are a vector of n IP unicast addresses, where n is the value in the Number of Sources (N) field. Membership Query Message Alberto Ornaghi 2022 19 IGMP v3 Message format There are three variants of the Query message: 1. A General Query” 2. A GroupSpecific Query” 3. A GroupandSourceSpecific Query” Membership Query Message In IGMPv3, General Queries are sent with an IP destination address of , the allsystems multicast address. GroupSpecific and GroupandSourceSpecific Queries are sent with an IP destination address equal to the multicast address of interest. Alberto Ornaghi 2022 20 IGMP v3 Message format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +++++++++++++++++++++++++++++++++ | Type = 0x22 | Reserved | Checksum | +++++++++++++++++++++++++++++++++ | Reserved | Number of Group Records (M) | +++++++++++++++++++++++++++++++++ | | . Group Record [1] . | | +++++++++++++++++++++++++++++++++ | . | . . . | . | +++++++++++++++++++++++++++++++++ | | . Group Record [M] . | | +++++++++++++++++++++++++++++++++ Membership Report Message Alberto Ornaghi 2022 21 IGMP v3 Message format Each Group Record has the following internal format: +++++++++++++++++++++++++++++++++ | Record Type | Aux Data Len | Number of Sources (N) | +++++++++++++++++++++++++++++++++ | Multicast Address | +++++++++++++++++++++++++++++++++ | Source Address [1] | + + . . . . . . + + | Source Address [N] | +++++++++++++++++++++++++++++++++ | | .