Fundamentals of Multicast pdf

© 2008 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialBSCI 1 Fundamentals of Multicast Fundamentals of Multicast © 2008 Cisco Systems, Inc. All rights reserved.BSCI 2 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Objectives – Why Multicast – Multicast Applications – Multicast Service Model – Multicast Distribution Tree – Multicast Forwarding – Multicast Protocol Basics – Multicast Protocol Review © 2008 Cisco Systems, Inc. All rights reserved.BSCI 3 CCNP – BSCI Bachkhoa Networking Academy Why Multicast?  When sending same data to multiple receivers  Better bandwidth utilization  Less host/router processing  Receivers’ addresses unknown Học viện mạng Bách Khoa - www.bkacad.com © 2008 Cisco Systems, Inc. All rights reserved.BSCI 4 CCNP – BSCI Bachkhoa Networking Academy Unicast vs Multicast Học viện mạng Bách Khoa - www.bkacad.com © 2008 Cisco Systems, Inc. All rights reserved.BSCI 5 CCNP – BSCI Bachkhoa Networking Academy Multicast Advantages  Enhanced Efficiency: Controls network traffic and reduces server and CPU loads  Optimized Performance: Eliminates traffic redundancy  Distributed Applications: Makes multipoint applications possible Học viện mạng Bách Khoa - www.bkacad.com © 2008 Cisco Systems, Inc. All rights reserved.BSCI 6 CCNP – BSCI Bachkhoa Networking Academy Multicast Disadvantages Multicast is UDP Based!!!  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 ―flow- control‖ mechanisms can result in network congestion. If possible, Multicast applications should attempt to detect and avoid congestion conditions.  Duplicates: Some multicast protocol mechanisms (e.g. Asserts, Registers and Shortest-Path Tree Transitions) result in the occasional generation of duplicate packets. Multicast applications should be designed to expect occasional duplicate packets.  Out-of-Sequence Packets: Various network events can result in packets arriving out of sequence. Multicast applications should be designed to handle packets that arrive in some other sequence than they were sent by the source. Học viện mạng Bách Khoa - www.bkacad.com © 2008 Cisco Systems, Inc. All rights reserved.BSCI 7 CCNP – BSCI Bachkhoa Networking Academy IP Multicast Applications Học viện mạng Bách Khoa - www.bkacad.com © 2008 Cisco Systems, Inc. All rights reserved.BSCI 8 CCNP – BSCI Bachkhoa Networking Academy IP Multicast Service Model  RFC 1112 (Host Ext. for Multicast Support)  Each multicast group identified by a class-D IP address  Members of the group could be present anywhere in the Internet  Members join and leave the group and indicate this to the routers  Senders and receivers are distinct: –i.e., a sender need not be a member  Routers listen to all multicast addresses and use multicast routing protocols to manage groups Học viện mạng Bách Khoa - www.bkacad.com © 2008 Cisco Systems, Inc. All rights reserved.BSCI 9 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Multicast Addressing IPv4 Header Options Padding Time to Live Protocol Header Checksum Identification Flags Fragment Offset Version IHL Type of Service Total Length Source Address Destination Address Destination Source 224.0.0.0 - 239.255.255.255 (Class D) Multicast Group Address Range Destination 1.0.0.0 - 223.255.255.255 (Class A, B, C) Source © 2008 Cisco Systems, Inc. All rights reserved.BSCI 10 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com IP Multicast Address Groups  Local scope addresses –224.0.0.0 to 224.0.0.255 –Reserved by the Internet Assigned Numbers Authority (IANA) for network protocol use. TTL=1  Global scope addresses –224.0.1.0 to 238.255.255.255 –Allocated dynamically throughout the Internet. –The 224.2.X.X range is used in Multicast Backbone (Mbone) applications. IETF  Administratively scoped addresses –239.0.0.0 to 239.255.255.255 –The administratively scoped multicast address space is divided into the following scopes: •Organization-local scope (239.192.0.0 to 239.251.255.255) •Site-local scope (239.255.0.0/16, with 239.252.0.0/16, 239.253.0.0/16, and 239.254.0.0/16 also reserved) [...]... www.bkacad.com 21 CCNP – BSCI Bachkhoa Networking Academy Multicast Protocol Basics  Multicast Distribution Trees  Multicast Forwarding  Types of Multicast Protocols –Dense Mode Protocols –Sparse Mode Protocols BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 22 CCNP – BSCI Bachkhoa Networking Academy Multicast Distribution Trees BSCI © 2008 Cisco Systems,... - www.bkacad.com 17 CCNP – BSCI Bachkhoa Networking Academy Multicast Addressing IP Multicast MAC Address Mapping (FDDI & Ethernet) Be Aware of the 32:1 Address Overlap 32 - IP Multicast Addresses 224.1.1.1 224.129.1.1 225.1.1.1 225.129.1.1 238.1.1.1 238.129.1.1 239.1.1.1 239.129.1.1 BSCI © 2008 Cisco Systems, Inc All rights reserved 1 - Multicast MAC Address (FDDI and Ethernet) 0x0100.5E01.0101... 233.242.58.0/24 GLOP address Học viện mạng Bách Khoa - www.bkacad.com 20 CCNP – BSCI Bachkhoa Networking Academy Learning About Multicast Sessions Potential receivers have to learn about multicast streams or sessions available before a multicast application is launched Possibilities:  Another multicast application sending to a well-known group whose members are all potential receivers  Directory services ... IANA Ethernet MAC Address Range Available range of MAC addresses for IP multicast 00000001:00000000:01011110:00000000:00000000:00000000 through 00000001:00000000:01011110:01111111:11111111:11111111  Within this range, these MAC addresses have the first 25 bits in common  The remaining 23 bits are available for mapping to the lower 23 bits of the IP multicast group address BSCI © 2008 Cisco Systems,... rights reserved Học viện mạng Bách Khoa - www.bkacad.com 29 CCNP – BSCI Bachkhoa Networking Academy Multicast Forwarding  Multicast Routing is backwards from Unicast Routing –Unicast Routing is concerned about where the packet is going Multicast Routing is concerned about where the packet came from  Multicast Routing uses “Reverse Path Forwarding” BSCI © 2008 Cisco Systems, Inc All rights reserved... Thresholds  What is a TTL Threshold? –A ―TTL Threshold‖ may be set on a multicast router interface to limit the forwarding of multicast traffic to outgoing packets with TTLs greater than the Threshold  The TTL Threshold Check –All incoming IP packets first have their TTL decremented byone If . www.bkacad.com Objectives – Why Multicast – Multicast Applications – Multicast Service Model – Multicast Distribution Tree – Multicast Forwarding – Multicast Protocol Basics – Multicast Protocol Review ©. © 2008 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialBSCI 1 Fundamentals of Multicast Fundamentals of Multicast © 2008 Cisco Systems, Inc. All rights reserved.BSCI 2 CCNP – BSCI. www.bkacad.com 224.1.1.1 224.129.1.1 225.1.1.1 225.129.1.1 . . . 238.1.1.1 238.129.1.1 239.1.1.1 239.129.1.1 0x0100.5E01.0101 1 - Multicast MAC Address (FDDI and Ethernet) 32 - IP Multicast Addresses Multicast Addressing Be Aware of the 32:1 Address Overlap IP Multicast MAC Address Mapping (FDDI