1. CS335 Principles of Multimedia Systems Multimedia Over IP Networks -- I Hao Jiang Computer Science Department Boston College Nov. 6, 2007

2. CS335 Principles of Multimedia Systems Introduction  Traffic on Internet was mainly from textual content.  In recent years, multimedia data transmission is occupying most of the network bandwidth.  IP network, especially Internet, is becoming a very attractive channel for multimedia communications. –Dedicated networks and ATM are not widely available. –There are many applications for Internet multimedia: Internet telephone, Internet TV, video conferencing, network games, remote corroboration, ….

3. CS335 Principles of Multimedia Systems Review Of TCP/IP Basic TCP/IP network model Data Encapsulation: Application Layer (telnet, ftp, etc.) Host-to-Host Transport Layer (TCP, UDP) Internet Layer (IP and routing) Network Access Layer (Ethernet, ATM, or whatever)

4. CS335 Principles of Multimedia Systems Review Of TCP/IP A TCP/IP node on 2 Ethernets

5. CS335 Principles of Multimedia Systems Review Of TCP/IP  Address Resolution Protocol (ARP) Each machine on a network has an ARP Table in its memory If “223.1.2.1” wants to send a packet to “223.1.2.2”, an ARP request will be broadcasted to the Ethernet.

6. CS335 Principles of Multimedia Systems Review Of TCP/IP “223.1.2.2” found the target IP matches its IP, it fills the Ethernet address and returns an ARP response to “223.1.2.1” “223.1.2.1” updates its ARP table and starts sending packets to “.2”

7. CS335 Principles of Multimedia Systems Review Of TCP/IP  Routing A sends E an IP packet. On “development”, the IP/Ethernet addresses are: While on “account”: 123

8. CS335 Principles of Multimedia Systems Review Of TCP/IP  Routing Table 123 Routing table for A --------------------------------------------------------------------- network direct/indirect router interface number --------------------------------------------------------------------- development direct 1 accounting indirect D 1 factory indirect D 1 --------------------------------------------------------------------- Routing table for D --------------------------------------------------------------------- network direct/indirect router interface number --------------------------------------------------------------------- development direct 1 accounting direct 2 factory direct 3 ---------------------------------------------------------------------

9. CS335 Principles of Multimedia Systems Review Of TCP/IP  Transport Protocols –UDP (User Datagram Protocol): A simple protocol for short delay and unreliable communication. –TCP (Transmission Control Protocol): A much more complex protocol that guarantees correct data transmission. By acknowledgement from the receiver. Retransmission if time is out or data is corrupted. –TCP is a stream protocol. The packet size is determined by the systems. –TCP also needs to build up a virtual circuit before the real communication happens.

10. CS335 Principles of Multimedia Systems Multimedia over Network  Properties of multimedia traffic –High bit rate. –Many coding schemes have variable bit rate streams. –Partial data missing or corrupted is Ok. –Tight timing constraint.  IP networks have no guarantee for –bandwidth allocation. –Limited delay.  Multimedia applications usually build on top of UDP –which may loses packets, receives packets in wrong order,…

11. CS335 Principles of Multimedia Systems Some Ad Hoc Schemes  For some simple applications, we can in fact use TCP to transmit videos. Multiple-view Video Streaming Server User 1 User 2 User n A Multiple-view Server Demo

12. CS335 Principles of Multimedia Systems Some Ad Hoc Schemes Some commercial products in fact use TCP for video streaming. Axis 206 network camera http://192.168.1.10/axis-cgi/mjpg/video.cgi For example, to get a motion jpeg video stream:

13. CS335 Principles of Multimedia Systems More about Ad Hoc Schemes UDP Header Some Additional Information Multimedia Data What should we put here?

14. CS335 Principles of Multimedia Systems Standard Solutions  The Integrated Services working group in the IETF (Internet Engineering Task Force) developed an enhanced Internet service model called Integrated Services that includes best-effort service and real-time service, see RFC 1633.  The real-time service will enable IP networks to provide quality of service to multimedia applications.  Resource ReServation Protocol (RSVP), together with Real-time Transport Protocol (RTP), Real-Time Control Protocol (RTCP), Real-Time Streaming Protocol (RTSP), provides a working foundation for real-time services.