1. Department of Computer Science Southern Illinois University Edwardsville Spring, 2010 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu CS 547/490 Network Programming IP Multicast/000 IP Multicast, Concept and Implementation

2. IP Multicast/001 CS 547 Advanced Network Programming 1. What is multicasting? 2. Motivations and possible applications for multicast communication 3. Intra-LAN and Inter-LAN Multicasting 4. IP Multicast and IGMP (Internet Group Multicast Protocol) 5. Example of IP Multicast application: Multicast time server and client Presentation Agenda

3. CS 547 Advanced Network Programming 1. What is multicasting (Part 1)? = one-to-many communication where multiple receivers receives same data IP Multicast/002 ReceiverSender

4. CS 547 Advanced Network Programming 1. What is multicasting (Part 1 - continued)? = one-to-many communication where multiple receivers receives same data IP Multicast/003 Receiver Sender

5. CS 547 Advanced Network Programming 1. What is multicasting (Part 2)? Multicast sender (simply called “sender” hereafter) Multicast receiver (sometimes called “member”) Multicast Group Broadcast and Multicast - Multicast is a subset of broadcast IP Multicast/004 - a collection of multicast receivers Multicast sender Multicast Group A multicast receiver

6. CS 547 Advanced Network Programming Two different flavors of multicast communication: 1. One-to-many Multicasting 2. Many-to-many Multicasting (Only one multicast sender in a group) (Multiple multicast senders in a group) 1. What is multicasting (Part 3)? IP Multicast/005 Sender Multicast Group Sender 1 Sender 2

7. CS 547 Advanced Network Programming 1. What is multicasting (Part 1 - continued)? IP Multicast/006 Sender Receiver 2 Receiver 3 Receiver 1 Receiver 2 Receiver 3 Receiver 1 Sender Unicasting (one-to-one) communication Multicasting (one-to-many) communication

8. CS 547 Advanced Network Programming 2. The motivations and possible applications for multicast communication (Part 1) What are the technical motivations behind multicasting? 1. Bandwidth sharing IP Multicast/007 Unicasting (one-to-one) communication Must have separate connections even if sending the same content Receiver B Receiver A Sender 2X bandwidth Ethernet

9. Multicasting (one-to-many) communication Receiver B Receiver A Sender 1X bandwidth Ethernet One connection for same content to multiple receivers IP Multicast/008 CS 547 Advanced Network Programming 1. Bandwidth sharing (continued)

10. CS 547 Advanced Network Programming 2. The motivations and possible applications for multicast communication (Part 2) What are the technical motivations behind multicasting (continued) ? 2. Shorter response time IP Multicast/009 R3 R1 R2 S Receiver Group SR1 R2, R3 Time R2 Receives it R3 Receives it Unicasting

11. R3 R1 R2 S Multicast Group SR1 R2, R3 R2 Receives it R3 Receives it Time Multicasting CS 547 Advanced Network Programming IP Multicast/010 2. Shorter response time (continued)

12. CS 547 Advanced Network Programming 2. The motivations and possible applications for multicast communication (Part 3) Major Multicast Applications Teleconferencing (extended Internet phone) Network radio and TV broadcasting Database and distributed BBS Distributed/parallel computing system - MISD (Multiple Instruction Same Data) Architecture IP Multicast/011

13. CS 547 Advanced Network Programming MISD Architecture and typical application: IP Multicast/012 Example: A = (B + C) + (2  B  C) + (B - C) (Server = Sender) Receiver 1 Receiver 2 B, C (B + C) (B - C) (2  B  C) (MISD = Multiple Instructions Same Data) (B + C), (B - C) (2  B  C)

14. CS 547 Advanced Network Programming 3. Intra-LAN and Inter-LAN Multicasting (Part 1): Intra-LAN Multicasting = Multicasting implemented using broadcast capability of a LAN ALOHA radio packet broadcast system developed by Univ. of Hawaii ALOHA evolved into “Slotted ALOHA”, then into “Ethernet” (by Xerox) Since a LAN is broadcast capable, it’s extremely easy to implement IP Multicast/013

15. CS 547 Advanced Network Programming Inter-LAN Multicasting Multicasting among multiple LANs (called “Extended LAN”) The concept was first introduced by Stephen Deering* in 1980. Since it’s multicast outside of a LAN, it does not rely on LAN broadcast Multicast packets now need to be explicitly forwarded to member receivers “Multicast” usually means “inter-LAN multicasting 3. Intra-LAN and Inter-LAN Multicasting (Part 2): IP Multicast/014

16. CS 547 Advanced Network Programming Inter-LAN Example 3. Intra-LAN and Inter-LAN Multicasting (Part 3): IP Multicast/015 Internet Request Response Request (1) Response with tag (2) Request (3) Response (4) Internet Request Response Internet Request Response Request (1) Response with tag (2) Request (3) Response (4) Internet Request Response LAN 1 LAN 2 LAN 3 Sender Receiver 1 Receiver 2 Receiver 3 Internet Request Response Request (1) Response with tag (2) Request (3) Response (4) Internet Request Response Receiver 4

17. CS 547 Advanced Network Programming Inter-LAN Multicasting The term “multicast” usually means “inter-LAN multicasting”* IP Multicast (as we will start discussion shortly) is an inter-LAN multicast * The concept first proposed by Steve Deering in 3. Intra-LAN and Inter-LAN Multicasting (Part 4): IP Multicast/016 “ Multicast Routing in Datagram Internetworks and Extended LANs,” ACM Transactions on Computer Systems, vol. 8, no. 2, pp. 85-111, May 1990.

18. CS 547 Advanced Network Programming 4. IP Multicast and IGMP (Part 1) IGMP = Internet Group Management Protocol IGMP is a protocol a router uses to manage multicast receivers IGMP itself relies on broadcast capability of a LAN IP Multicast/017

19. CS 547 Advanced Network Programming 4. IP Multicast and IGMP (Part 2) IP Multicast Mechanism: IP and IGMP Collaboration Q: How a multicast sender can know where receivers exist? QUESTION SOLUTIONS Won’t work (too many routers in the Internet) S1: Broadcast to every possible router in the Internet S2: Send multicast data only to the routers in need But how we know which routers? IP Multicast/018

20. CS 547 Advanced Network Programming 4. IP Multicast and IGMP (Part 3) LAN A LAN B LAN C LAN D Router A Router B Router D Router C Router X Multicast Sender R1 R2 R3 R4 IP Multicast/019 IGMP

21. CS 547 Advanced Network Programming 4. IP Multicast and IGMP (Part 4) Router X Multicast Sender R1 TTL=1 TTL=2 IP Multicast/020