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

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

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

Network Architecture and Design 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

Network Architecture and Design 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

Network Architecture and Design Class–D Addresses 1 group ID 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

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

Network Architecture and Design 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

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

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

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

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

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

Network Architecture and Design 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

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

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

Network Architecture and Design 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

Network Architecture and Design 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

Network Architecture and Design 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

Network Architecture and Design 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

Network Architecture and Design RSVP Example R2 R3 PATH 2 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. PATH 3 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. R4 1. An application on Host A creates a session, 128.32.32.69/4078, by communicating with the RSVP daemon on Host A. 1 R1 Host B 128.32.32.69 Host A 24.1.70.210 R5 Network Architecture and Design

Network Architecture and Design RSVP Example R2 R3 6 PATH R4 6. Reservation has been made and data flow begins with the guaranteed QoS. 4 RESV R1 5 Host B 128.32.32.69 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

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

Network Architecture and Design RSVP Vs. ST2 ST2 RSVP Functionality Signaling protocol and data transfer. Signaling. Connection Types Connection-oriented, multicast, multipeer. Short-lived connections, multicast. Reservations Sender or Receiver oriented Receiver-oriented Modifications QoS and receiver group through explicit messages QoS and receiver group through periodic messages Error Handling Complex control and correction Periodic message exchange Heterogeneity No Yes Network Architecture and Design

Network Architecture and Design 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

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

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 IP header, dest = unicast dest = multicast transport header and data… Network Architecture and Design

Network Architecture and Design End of Third Lecture Network Architecture and Design