Hosts & Router. Multicast sent. Forwarded by Router as members exist on other LAN TRANSCEIVER TRANSCEIVER TRANSCEIVER TRANSCEIVER. 10Bbase2.

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1 Link Level gain Ethernet Base Hosts Router Base Multicast sent Base Forwarded by Router as members exist on other L Base Group Members receive packet Other hosts ignore it Easy on traditional cable ethernet Packets pass all transceivers which send everything to IC which accepts all relevant packets Ethernet Multicast Base Router knows members on link Earlier report message told it oone knows how many members oone cares Modern Ethernet Base Switching Hub TM CoreBuilder Com m tpl tpl m Switch replaces cable Base Com CoreBuilder TM Switching Hub tpl tpl m m allows parallel packets packets sent only to appropriate ports switch learns what is where Causes problems for multicast Learning is from source addresses when packets transmitted Multicast addresses never source addresses

2 Modern Ethernet Multicast Base Com CoreBuilder TM Switching Hub tpl tpl m m Router sends multicast Switch must forward But Where Base Com CoreBuilder TM Switching Hub tpl tpl m m But not efficient Unknown destinations are rare Either address does not esist o point sending to it Or it will reply and become known quickly Multicast packets can be high volume ever any reply Can just broadcast send everywhere Simple and correct Same as any unknown destination Modern Ethernet Multicast Base Com CoreBuilder TM Switching Hub tpl tpl m m Router sends multicast Switch should forward efficiently How Base Com CoreBuilder TM Switching Hub tpl tpl m m IGMP snooping Switch monitors IGMP protocol Layer device switch Layer protocol IGMP Layering voiolation It works But isn t easy Modern Ethernet Multicast Base Com CoreBuilder TM Switching Hub tpl tpl m m Group members send reports group address is destination Base Com CoreBuilder TM Switching Hub tpl tpl m m Report supression makes this hard not all hosts answer query Switch Cheats Does not forward reports to anyone but router Knows what is a router it sends query Switch remembers which ports are in which groups

3 Multicast with IGMPv s multicast traffic grew problem noticed Only enabledisable traffic by group address ny sender can transmit to a valid group Flood net with unwanted traffic pplications can ignore it but net must still carry deliver it lso difficult for switches to be both efficient and correct IGMP v created to alleviate these IGMP v IGMP v extends PI Previously application could ask to join a multicast group ask to leave a multicast group ow ask to join with a specified sender set includes ask to join with all but a specified set excludes ote leave is gone o longer needed leave join with empty sender set v v join join with empty exclude set IGMPv also deletes report suppression hosts now always reply to Query Even if another host replied replies sent to dedicated group address used only for reports Host Requirements System must Combine application include exclude sets Keep track of what senders for which application Send a report whenever result alters pplication changes set Change from include to exclude or reverse ew application joins group pplication leaves group ot just for first application joining group Reports include List of addresses IncludeExclude flag IGMPv allows reports for multiple groups merged into one packet Everything much more complex

4 IGMP v Query x Max Resp Group ddress QQIC umber of Sources Source ddress Source ddress Source ddress ote Smallest IGMPv query packet bytes IGMP vv query packets all bytes Can distinguish without change IGMP v Query x Max Resp Group ddress QQIC umber of Sources Source ddress Source ddress Source ddress Three Query types General Query Similar to v Query v general Query Group ddress GroupSpecific Query Similar to v group specific query umber of Sources GroupndSourceSpecific Query ew Query type umber of Sources IGMP v Query x Max Resp Group ddress QQIC umber of Sources Source ddress Source ddress Source ddress ew fields S Suppress Router Timer Updates llows query without affecting other routers Hosts query router election ignore this bit QRV Query Robustness Variable umber of times router transmits query QQIC Querier s Query Interval Specifies repeat interval for queries

5 IGMP v Query x Max Resp Group ddress QQIC umber of Sources Source ddress Source ddress Source ddress Max Resp and QQIC encoding In IGMPv Max Resp is seconds in standard In IGMPv Max Resp is seconds In IGMPv Max Resp is seconds Or floating point format if e m m e Max Resp units of seconds QQIC units of second same encoding IGMP v Query x Max Resp Group ddress QQIC umber of Sources Source ddress Source ddress Source ddress Source ddresses GroupndSourceSpecific Query Seek to discover Does any node want traffic To the Group ddress From any of the Source ddresses Only limit on number of source addresses is max packet size MTU of link IGMP v Report x umber of Group Records M Group Record Group Record Group Record M Entirely new format new type value Report contains M Group Records M limited by packet size Can send multiple packets Rules handle if Group Record too big Group Record describes Multicast Group Replaces Group ddress in earlier Reports

6 IGMP v Group Record Record ux Data Len umber of Sources Multicast ddress Source ddress Source ddress Source ddress uxiliary Data Multicast ddress is the Group ddress The multicast group reported Source ddresses ddresses to include or exclude as senders s many as required by applications on host and algorithm for combining IGMP v Group Record Record ux Data Len umber of Sources Multicast ddress Source ddress Source ddress Source ddress uxiliary Data Record type Indicates Include or Exclude or change of various types kinds ux Data ux Data Len For future expansion ux Data Len in IGMPv o ux Data included Excluding Sources Excluding a source address llows router to not send packets to link If they are from excluded source But Only if no host on link requests that sender nd so if all hosts are IGMPv Hosts must still filter Only one packet sent to link Sent if any host wants it Received by all who joined group Special Case The ll Hosts Multicast Group ever reported ll hosts join Known to exist on every link Same for IGMP v v v

7 IP v Clearly need a new protocol IGMP has v addresses everywhere v addresses don t fit Multicast Listener Discovery MLD v RFC v RFC v derived from IGMP v v derived from IGMP v ote Multicast is inherent in IPv not an addon as in IPv MLD is required in LL v nodes MLD is part if ICMPv Uses ICMPv packet formats Messages have new type codes MLD v Query Group ddress Multicast ddress Multicast Listener Query ICMPv field unused with MLD set to ICMPv field checksum of MLD packet pesudo header milliseconds MLD v Report Group ddress Multicast ddress Multicast Listener Report ICMPv field unused with MLD set to ICMPv field checksum of MLD packet pesudo header Unused in Report

8 MLD v Done Group ddress Multicast ddress Multicast Listener Done ame change from Leave in IGMP s in previous message types Unused in Done MLD v Same changes as IGMP v IGMP v For the same reasons dd include or exclude list of source addresses Change timers to floating point Max Response e m m e units of milliseconds QQIC uses same format as IGMP units of second e m m e MLD v Query Max Response Group ddress QQIC umber of Sources Source ddress

9 MLD v Report um of Mcast ddr Records M Multicast ddress Record Multicast ddress Record Multicast ddress Record M MLD v Report Record Record ux Data Len umber of Sources Multicast ddress Source ddress Source ddress MLD v Report Record Report Records Identical Procedures to IGMPv Same record types Include Exclude Change ux Data still not used ux Data Len Just bigger addresses Max source addresses More likely multiple report messages required