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

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, ….

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)

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

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 “ ” wants to send a packet to “ ”, an ARP request will be broadcasted to the Ethernet.

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

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

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 Routing table for D network direct/indirect router interface number development direct 1 accounting direct 2 factory direct

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.

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,…

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

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

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

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  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.