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Multicast Communication

Multicast Communication. The Basics of Group Communication Types of communication Quality of Service Integrated Services (IntServ) Resource Reservation Protocol (RSVP) ST2 MBone Reference

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Multicast Communication

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  1. Multicast Communication • The Basics of Group Communication • Types of communication • Quality of Service • Integrated Services (IntServ) • Resource Reservation Protocol (RSVP) • ST2 • MBone Reference R. Wittman and M. Zitterbart, Multicast Communication, Protocols and Applications, ISBN 1-55860-645-9, 2001. Network Architecture and Design

  2. Unicast Communication (1:1) • One packet for each receiver Network Architecture and Design

  3. Multicast Communication (1:n) • One packet to many receivers • Routers replicate the packet • Like mailing lists • One email to many receivers Network Architecture and Design

  4. Unicast Vs. Multicast • Unicast • With 3 receivers, sender must replicate the stream 3 times. • Consider good quality audio/video streams are about 1.5Mb/s (a T1). • Each additional receiver requires another 1.5Mb/s of capacity on the sender network. • Multiple duplicate streams over expensive WAN links. • Multicast • Source transmits one stream of data for 3 receivers. • Replication happens inside routers and switches. • WAN links only need one copy of the data, not 3 copies. Network Architecture and Design

  5. How Multicast works? • Nodes consist groups • Each group is identified by a single IP address • Class-D addresses • Groups may be of any size and members of groups may be located anywhere in the Internet. • Members of groups can join and leave (IGMP). • Senders need not be members. Network Architecture and Design

  6. 1 1 1 0 group ID Class–D Addresses • Class-D IP address • In “dotted decimal” notation: • 224.0.0.0 — 239.255.255.255 • Nodes that support class-D addresses consist the Multicast Backbone (MBone) Network Architecture and Design

  7. Other Types of Communication • Concast Communication (m:1). • Multipeer/multipoint (m:n). • Broadcast. • Anycast. Network Architecture and Design

  8. Anycast • Distance between client and server is usually large • High response time • Bandwidth binding in many links • Inflexible in topology changes • Need for many service points Network Architecture and Design

  9. What is Anycast Routing? • A means of selecting and communicating with anyone of a set of distributed servers or service access points within a network • The router delivers the datagram to the nearest member of the group. • Appropriate for server-based applications Network Architecture and Design

  10. Unicast Routing Example FTP Request Database Request Database Server FTP Server Network Architecture and Design

  11. Anycast Routing Example FTP Request Database Request Database Server group FTP Server group Resolver Network Architecture and Design

  12. Anycast Routing - Resolver • Close to client • Maintains • Anycast group membership • Selects web server according to: • Best response time • Best server processing time Network Architecture and Design

  13. Multicast Communication • The Basics of Group Communication • Types of communication • Quality of Service • Integrated Services (IntServ) • Resource Reservation Protocol (RSVP) • ST2 • MBone Network Architecture and Design

  14. IntServ • Change Internet service to provide QoS • IntServ is not a protocol but a framework. • Usage of RSVP or ST2. • Supports three classes of services • Best Effort • Controlled Load Services • Guaranteed Services Network Architecture and Design

  15. IntServ • An analogy: Travel by airplane • Unreserved seat = Best Effort • Reserved Seat = Controlled Load • Charter your own flight = Guaranteed Service Network Architecture and Design

  16. IntServ • Best Effort • Bandwidth is not reserved • Per-packet delay is not guaranteed • Controlled Load • Bandwidth is reserved • Per-packet delay is not guaranteed • Performs like a lightly loaded Best Effort network • Guaranteed Service • Bandwidth is reserved • Per-packet delay is guaranteed • Performs like having your own network Network Architecture and Design

  17. IntServ • Traffic Flow • Multimedia IP traffic is correlated. • Each packet from a sender to a receiver is part of a flow. • IntServ provides QoS for a Flow, not individual packets. • Flow specification generally same as TCP connection (IP Address/Port). • Need for reservation setup mechanism. Network Architecture and Design

  18. RSVP • What is RSVP? • RSVP: Resource Reservation Protocol • Application reserve resources in order to specify desired QoS to net. • Multicast friendly, receiver-oriented. • Why run RSVP? • Allows precise allocation of network resources. • Guarantees on quality of service. • Heterogeneous bandwidth support for multicast. Network Architecture and Design

  19. RSVP Operation • Sender advertises PATH messages to receiver • PATH = TSpec + AdSpec • TSpec: Specify the traffic characteristics • AdSpec: • Contain information about the path’s resources • Updated in every RSVP capable router • Help receivers calculate the resources needed to obtain desired QoS Network Architecture and Design

  20. RSVP Operation (cont) • Receiver reserves resources using RESV messages • RESV = Rspec + filterspec + policy data • Rspec: Specify the bandwidth needed • Filterspec: How reservations are distributed to data streams and users. • Travel upstream in reverse direction of Path message • Routers receive the RESV messages and make the reservation (if available resources are more than Rspec resources) Network Architecture and Design

  21. 2 PATH PATH 1 3 PATH PATH 1. An application on Host A creates a session, 128.32.32.69/4078, by communicating with the RSVP daemon on Host A. 3. The PATH message follows the next hop path through R5 and R4 until it gets to Host B. Each router on the path creates soft session state with the reservation parameters. 2. The Host A RSVP daemon generates a PATH message that is sent to the next hop RSVP router, R1, in the direction of the session address, 128.32.32.69. RSVP Example R2 R3 R4 R1 Host B 128.32.32.69 Host A 24.1.70.210 R5 Network Architecture and Design

  22. PATH RESV RESV PATH RESV PATH PATH RESV 6. Reservation has been made and data flow begins with the guaranteed QoS. RSVP Example R2 R3 6 R4 4 R1 Host B 128.32.32.69 5 Host A 24.1.70.210 R5 4. An application on Host B communicates with the local RSVP daemon and asks for a reservation in session 128.32.32.69/4078. The daemon checks for and finds existing session state. 5. The Host B RSVP daemon generates a RESV message that is sent to the next hop RSVP router, R4, in the direction of the source address, 24.1.70.210. Network Architecture and Design

  23. Internet Stream Protocol Version 2 (ST2) • The communication process takes place in three separate steps: • Establishment of an ST2 stream • Transfer of user data • Termination of an ST2 stream. • Different protocols are applied • ST2 • SCMP (Stream Control Message Protocol) Network Architecture and Design

  24. RSVP Vs. ST2 Network Architecture and Design

  25. The MBone • An “interconnected” set of multicast-capable routers, providing the IP multicast service in the Internet • Can be thought of as a virtual network, overlaid on the Internet Network Architecture and Design

  26. Mbone - Example Tunnel Simple Router Multicast Router Source Node Destination Node Network Architecture and Design

  27. IP header, dest = unicast IP header, dest = multicast transport headerand data… MBone Tunnels • A method for sending multicast packets through multicast-ignorant routers • IP multicast packet is encapsulated in a unicast packet addressed to far end of tunnel • A tunnel acts like a virtual point-to-point link • Each end of tunnel is manually configured with unicast address of the other end Network Architecture and Design

  28. End of Third Lecture Network Architecture and Design

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