【正文】 1 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 2 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Introduction to IP Multicast Session 2214 3 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Other Related Presentations ?Multicast Sessions Session Title 2214 Introduction to IP Multicast 2215 PIM Multicast Routing 2216 Deploying IP Multicast 2217 Advanced IP Multicast Routing ?MBGP Related Sessions Session Title 2209 Deploying BGP 4 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Agenda ? Why Multicast? ? Multicast Addressing ? HostRouter Signaling: IGMP ? Multicast Distribution Trees ? Multicast Forwarding ? Multicast Routing Protocols Geekometer 5 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Server Router Unicast Server Router Multicast Unicast vs. Multicast 6 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Example: Audio Streaming All clients listening to the same 8 Kbps audio ? Enhanced Efficiency: Controls work traffic and reduces server and CPU loads ? Optimized Performance: Eliminates traffic redundancy ? Distributed Applications: Makes multipoint applications possible 0 Traffic Mbps 1 20 40 60 80 100 Clients Multicast Unicast Multicast Advantages 7 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Multicast Disadvantages ? Best Effort Delivery: Drops are to be expected. Multicast applications should not expect reliable delivery of data and should be designed accordingly. Reliable Multicast is still an area for much research. Expect to see more developments in this area. ? No Congestion Avoidance: Lack of TCP windowing and ―slowstart‖ mechanisms can result in work congestion. If possible, Multicast applications should attempt to detect and avoid congestion conditions. ? Duplicates: Some multicast protocol mechanisms (. Asserts, Registers and SPT Transitions) result in the occasional generation of duplicate packets. Multicast applications should be designed to expect occasional duplicate packets. ? Out of Order Delivery : Some protocol mechanisms may also result in out of order delivery of packets. Multicast Is UDP Based!!! 8 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Apps that Benefit from IP Multicast ? Multimedia –Streaming media –Training, corporate munications –Conferencing—video/audio ? Data warehousing ? Financial applications ? Any onetomany data push applications 9 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Agenda ? Why Multicast? ? Multicast Addressing ? HostRouter Signaling: IGMP ? Multicast Distribution Trees ? Multicast Forwarding ? Multicast Routing Protocols 10 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 ? IP Multicast Group Addresses – – – Class ―D‖ Address Space ? High order bits of 1st Octet = ―1110‖ ? Reserved Linklocal Addresses – – – Transmitted with TTL = 1 – Examples: ? All systems on this sub ? All routers on this sub ? DVMRP routers ? OSPF routers ? PIMv2 Routers Multicast Addressing 11 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 ? Administratively Scoped Addresses – – – Private address space ?Similar to RFC1918 unicast addresses ?Not used for global Inter traffic ?Used to limit ―scope‖ of multicast traffic ?Same addresses may be in use at different locations for different multicast sessions – Examples ?Sitelocal scope: ?Organizationlocal scope: Multicast Addressing 12 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 32 Bits 28 Bits 25 Bits 23 Bits 48 Bits 01005e7f0001 1110 5 Bits Lost Multicast Addressing IP Multicast MAC Address Mapping (FDDI and Ether) 13 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 . . . 1 Multicast MAC Address (FDDI and Ether) 32 IP Multicast Addresses Multicast Addressing Be Aware of the 32:1 Address Overlap IP Multicast MAC Address Mapping (FDDI amp。 Ether) 14 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 A Layer 3 IPmc Address Maps to a single Token Ring Functional Address or the all ones’ Broadcast address: Results in high levels of unwanted interrupts for noninterested Hosts c00000040000 ffffffffffff (Shown in Token Ring, noncanonical format) IP Multicast MAC Address Mapping (Token Ring) Multicast Addressing 15 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 . . . 1 Multicast MAC Address (Token Ring) ALL 268,435,200 IP Multicast Addresses Multicast Addressing RUN AWAY ! ! ! Be Aware of the 268,435,200:1 Address Overlap IP Multicast MAC Address Mapping (Token Ring) 16 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Multicast Addressing ? Dynamic Group Address Assignment – Historically acplished using SDR application ?Sessions/groups announced over wellknown multicast groups ?Address collisions detected and resolved at session creation time ?Has problems scaling – Future dynamic techniques under consideration ?Multicast Address SetClaim (MASC) – Hierarchical, dynamic address allocation scheme – Extremely plex garbagecollection problem. – Long ways off ?MADCAP – Similar to DHCP – Need application and host stack support 17 169。 2022, Cisco Systems, Inc. 2214 1197_05_2022_c2 Multicast Addressing ? Static Group Address Assignment (new) – Temporary method to meet immediate needs – Group range: ?Your AS number is inserted in middle two octets ?Remaining loworder octet used for group assignment – Defined in IETF draft ?―‖ 18 169。 2022, Cisco Systems, Inc. 2214 1197_05_202