,< 資 管 Lee 附錄 A0 IGMP vs Multicast Listener Discovery

,< 資 管 Lee IGMP in IPv4 Class D address ◦ Range ~ Group identifier Report Query ICMP IGMP IP ARP RARP

,< 資 管 Lee IGMP message format VerTypeUnusedChecksum Group address in report, all 0s in query Ver: four-bit field defines the version of the protocol, version 1 Type: four-bit defines the type of the message: 1 for query and 2 for report Checksum: 16-bit field defines the checksum Group address:this 32-bit field defines the group address in a report message. It is Filled with 0s in the query message. In a report message, this field defines either The groupid that a system wants to join or the groupid wants to continue the Membership.

,< 資 管 Lee LAN List of groups Having loyal members Four situations of IGMP: Joining a group: Monitoring the group: Membership continuing: Leaving a Group:

,< 資 管 Lee Report 2 Group address Query 1 All 0s Report 2 Group address No response to query

,< 資 管 Lee Changing IP address to Physical Addresses bits23 bits of multicast address bit class D address 48-bit Ethernet address unused IGMP message IP Data IP header Trail (if any) Frame Data Frame header Encapsulation

,< 資 管 Lee Teaching Objects in Multicast Design Group-Joining module Group-leaving module Input module Output module    Timers Group table Multicast Lister report Multicast Lister Query/report A request to join a group A request to leave a group Application Layer IP Layer Group table: four fields State: FREE, DELAYING, IDLE Interface no.: interface no. to which multicast is sent. Group address: Reference count:

,< 資 管 Lee Group-Joining Module Receive: a request from a process to join a group 1. Look for the corresponding entry in the table 2. If (found) 1. increment the reference count 3. If (not found) 1. create an entry with reference count set to one 2. Add the entry to the table 3. Inform the data link layer to update its configuration table. 4. Set the state to DELAYING. 5. Start a timer. 6. Return

,< 資 管 Lee Group-Leaving Module Receive: a request from a process to leave a group 1. Look for the corresponding entry in the table 2. If (found) 1. Decrement the reference count 2. if (reference count is zero) 1. if (any timer for this entry) cancel the timer. 2. Change the state to FREE. 6. Return

,< 資 管 Lee Input Module Receive: an Multicast listener query/report 1. Check the message type 2. If (query) 1. Start a timer for each entry in the table with the state IDLE 2. Change each IDLE state to DELAYING state 3. Return 3. If (report) 1. Look for the corresponding entry in the table 2. if (found and state is DELAYING) 1. Cancel the timer for this entry. 2. Change the state to IDLE 4. Return

,< 資 管 Lee Output Module Receive: a signal from a timer 1. Look for the corresponding entry in the table 2. If (found and state is DELAYING) 1. Create a report 2. Send the report 3. Reset the state to IDLE 3. Return

,< 資 管 Lee MLD in IPv6

,< 資 管 Lee Lesson Objectives Multicast Listener Discovery (MLD) protocol Describe how IPv6 hosts and routers support multicast communication Describe the structure of an MLD messages Describe the structure and purpose of each type of MLD messages

,< 資 管 Lee Overview of Multicast Listener Discovery IPv6 equivalent of Internet Group Management Protocol version 2 (IGMPv2) for IPv4 Enables routers to discover the set of multicast addresses for which there are listening nodes for each attached interface

,< 資 管 Lee IPv6 Multicast Overview In IPv4, multicast support is optional. In IPv6,multicast support is required. Elements in multicast are: ◦ Multicast provides one-to-many delivery ◦ The set of hosts listening on a specific IPv6 multicast address is called a multicast group ◦ Multicast group membership is dynamic, and hosts can join and leave the group at any time ◦ There are no limitations to the size of a multicast group ◦ A multicast group can span IPv6 routers across multiple subnets ◦ A host can send traffic to a multicast address without being a member of the group

,< 資 管 Lee Host Support for Multicast To send multicast packets: ◦ Determine the IPv6 multicast address to use ◦ Place the IPv6 multicast packet on the medium To receive multicast packets: ◦ Applications inform IPv6 to receive multicast traffic ◦ Register the multicast MAC address with the network adapter: instructs the network adapter to listen for and pass to higher protocol layers ◦ Inform local routers  The host must inform local subnet routers that it is listening for multicast traffic at a specific multicast address. The protocol that registers multicast group information for IPv6 is MLD. The host sends an MLD Multicast Lister Report message to register membership in a specific multicast group.

,< 資 管 Lee Router Support for Multicast Receive all IPv6 multicast traffic Forward IPv6 multicast traffic Receive and process MLD Multicast Listener Report and Multicast Listener Done messages Query attached subnets for host membership status Communicate group membership to other IPv6 multicast routers

,< 資 管 Lee MLD Packet Structure

,< 資 管 Lee Structure of an MLD Message Packet IPv6 Header Next Header = 0 (Hop-by-hop Options) MLD MessageHop-by-Hop Options Header IPv6 Router Alert Option Next Header = 58 (ICMPv6)

,< 資 管 Lee Structure of the Multicast Listener Query Message Type Code Checksum Maximum Response Delay Unused Multicast Address = 0 = 130 = 0

,< 資 管 Lee Structure of the Multicast Listener Report Message Type Code Checksum Maximum Response Delay Unused Multicast Address = 0 = 131 = 0

,< 資 管 Lee Structure of the Multicast Listener Done Message Type Code Checksum Maximum Response Delay Unused Multicast Address = 0 = 132 = 0

,< 資 管 Lee Review Multicast Listener Discovery (MLD) protocol Multicast communication for IPv6 hosts and routers MLD messages