Migration of Multimedia Streams

1
Migration of Multimedia Streams

• John Gilbert

2
Streaming Technology

• Progressive download
• Hypertext transfer protocol (HTTP)
• True streaming
• Realtime streaming protocol (RTSP)
• Realtime protocol (RTP)
• Transport protocol - packet format definitions
• Control protocol (RTCP)
• Session description protocol (SDP)

3
True Streaming Example
Streaming client
Streaming server
4
Delivery Platforms

• Apple.
• Darwin streaming server.
• Hinted quicktime / MPEG.
• MPEG4IP project (encoder, hinter and client).
• Real.
• Helix DNA (encoder, server and client).
• Realtime packetisation of MP3, realaudio,
  realvideo etc.
• Microsoft.
• Windows media services.

5
Methods of Stream Migration

• Transparent to client application.
• Copy state to new server and synchronise handoff.
• Exploit client buffer for synch, rely on
  connectionless udp for stream delivery.
• Problem with RTSP RTCP.
• Transparent to end-user.
• Explicitly manage migration on client side.
• Setup multiple streams locally manage the
  client buffer.

6
Implementation

• Helix DNA reconnect feature
• Server specifies alternate servers during RTSP
  SETUP
• Client selects one to reconnect to
• Problems
• Does not detect failure
• Synchronisation algorithm not robust
• New RTSP method (MIGRATE)
• Client server protocol stack
• Server plugin API
• Averages to 0.6 seconds per migration (in lab)

7
Application - Load Balancing

• Group communication
• Spread
• Balance protocol
• Election of control server
• Br, dl, ll, al, hl
• Balance metric
• Bandwidth (multiple knapsack problem)
• Connections (alternative to hardware or DNS load
  balancing)

• Implementation
• Server plugins (single load v multi load)
• Helix server registry