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 , 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 to many receivers
Network Architecture and Design

4. 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

5. 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

6. Network Architecture and Design
Class–D Addresses 1
group ID
Class-D IP address
In “dotted decimal” notation: —
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. 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

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. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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,
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, /4078, by communicating with the RSVP daemon on Host A. 1 R1
Host B
Host A R5
Network Architecture and Design

22. 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
Host A R5
4. An application on Host B communicates with the local RSVP daemon and asks for a reservation in session /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,
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. 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

25. 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

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

27. 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

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