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Computer Networks IP Multicast
Recall <ul><li>Unicast </li></ul><ul><li>Broadcast </li></ul><ul><li>Multicast </li></ul><ul><ul><li>sends to a specific g...
Unicast
Multicast
Introduction to IP Multicast <ul><li>Class D group address (224-239.x.x.x) </li></ul><ul><ul><li>First bits must be 1110 o...
IP Multicast Addressing <ul><li>Some reserved addresses </li></ul><ul><ul><li>224.0.0.0/24 Link local reserved </li></ul><...
Internet Group Multicast Protocol (IGMP) <ul><li>Standardized in RFC 1112 and 2236 </li></ul><ul><li>Host/Router signallin...
Multicast routing <ul><li>Backwards from unicast routing </li></ul><ul><ul><li>Reverse Path Forwarding (RFP) </li></ul></u...
Distance Vector Multicast Routing Protocol (DVMRP) <ul><li>Similar to RIP </li></ul><ul><li>Infinity = 32 hops </li></ul><...
Multicast OSPF (MOSPF) <ul><li>LSAs carry multicast route information </li></ul><ul><li>Each router learns entire multicas...
Protocol Independent Multicast Dense Mode (PIM-DM) <ul><li>Uses any underlying routing protocol </li></ul><ul><ul><li>e.g....
Protocol Independent Multicast Sparse Mode (PIM-SM) <ul><li>Supports source and shared trees </li></ul><ul><li>Uses a Rend...
PIM-SM Illustrated
Internet MBONE <ul><li>Multicast backbone overlay on the Internet </li></ul><ul><li>Originally used DVMRP, now mostly uses...
Common MBONE Tools <ul><li>SDR </li></ul><ul><li>VAT/RAT </li></ul><ul><li>VIC </li></ul><ul><li>WB </li></ul><ul><li>IP/T...
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  1. 1. Computer Networks IP Multicast
  2. 2. Recall <ul><li>Unicast </li></ul><ul><li>Broadcast </li></ul><ul><li>Multicast </li></ul><ul><ul><li>sends to a specific group </li></ul></ul>
  3. 3. Unicast
  4. 4. Multicast
  5. 5. Introduction to IP Multicast <ul><li>Class D group address (224-239.x.x.x) </li></ul><ul><ul><li>First bits must be 1110 of first octet </li></ul></ul><ul><li>How to join/leave a multicast group? </li></ul><ul><li>How to map to hardware address? </li></ul><ul><li>How to route to a IP multicast group? </li></ul>
  6. 6. IP Multicast Addressing <ul><li>Some reserved addresses </li></ul><ul><ul><li>224.0.0.0/24 Link local reserved </li></ul></ul><ul><ul><ul><li>e.g. 224.0.0.9 - RIPv2 routers </li></ul></ul></ul><ul><ul><li>239.0.0.0/8 Private (Administratively Scoped) </li></ul></ul><ul><li>IP Multicast to ethernet multicast mapping </li></ul><ul><ul><li>place low-order 23 bits of IP address into low-order 23 bits of special Ethernet address 01:00:5e:00:00:00 </li></ul></ul><ul><ul><li>problem... IP multicast has 28 significant bits! </li></ul></ul>
  7. 7. Internet Group Multicast Protocol (IGMP) <ul><li>Standardized in RFC 1112 and 2236 </li></ul><ul><li>Host/Router signalling protocol </li></ul><ul><li>Hosts send IGMP join messages </li></ul><ul><li>Router periodically queries </li></ul><ul><li>IGMPv3 in draft </li></ul><ul><ul><li>Hosts only listen to specific group sources </li></ul></ul>
  8. 8. Multicast routing <ul><li>Backwards from unicast routing </li></ul><ul><ul><li>Reverse Path Forwarding (RFP) </li></ul></ul><ul><li>Route away from source </li></ul><ul><li>Could follow the shortest (source tree) path </li></ul><ul><li>Could build a shared distribution tree </li></ul><ul><ul><li>Rendevous Point (RP) </li></ul></ul><ul><li>Dense (Push) and Sparse (Pull) Modes </li></ul>
  9. 9. Distance Vector Multicast Routing Protocol (DVMRP) <ul><li>Similar to RIP </li></ul><ul><li>Infinity = 32 hops </li></ul><ul><li>Flood and Prune builds distribution tree </li></ul><ul><li>Grafting adds back a link </li></ul><ul><li>Was widely used in early MBONE </li></ul><ul><li>Does not scale </li></ul>
  10. 10. Multicast OSPF (MOSPF) <ul><li>LSAs carry multicast route information </li></ul><ul><li>Each router learns entire multicast tree </li></ul><ul><li>Only works with OSPF networks </li></ul><ul><li>Does not scale well </li></ul><ul><li>Not popular </li></ul>
  11. 11. Protocol Independent Multicast Dense Mode (PIM-DM) <ul><li>Uses any underlying routing protocol </li></ul><ul><ul><li>e.g. RIP, OSPF, IS-IS, BGP, etc. </li></ul></ul><ul><li>Very similar to DVMRP </li></ul><ul><li>Floods and prunes back based on membership </li></ul><ul><li>Does not scale to large networks (MBONE) </li></ul>
  12. 12. Protocol Independent Multicast Sparse Mode (PIM-SM) <ul><li>Supports source and shared trees </li></ul><ul><li>Uses a Rendevous Point (RP) </li></ul><ul><li>Can use any underlying routing protocol </li></ul><ul><li>Traffic only sent down joined branches </li></ul><ul><li>Can dynamically switch to optimal source tree depending on traffic pattern </li></ul>
  13. 13. PIM-SM Illustrated
  14. 14. Internet MBONE <ul><li>Multicast backbone overlay on the Internet </li></ul><ul><li>Originally used DVMRP, now mostly uses PIM-SM </li></ul><ul><li>Few commercial organizations using it </li></ul><ul><li>Many educational and research institutions using it </li></ul>
  15. 15. Common MBONE Tools <ul><li>SDR </li></ul><ul><li>VAT/RAT </li></ul><ul><li>VIC </li></ul><ul><li>WB </li></ul><ul><li>IP/TV </li></ul><ul><li>Mtrace </li></ul>

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