Video over ATM Networks

The delivery of video involves many types of Quality of Service issues:

1.

CBR (Constant Bit Rate) - e.g. uncompress video

2.

VBR (Variable Bit Rate) - suitable for packetized video (compressed video)

3.

ABR (Available Bit Rate) - can be backed off or buffered due to congestion, can only specify frame/cell loss and error

4.

UBR (Unspecified Bit Rate) - no guarantee on any quality parameter

Many Multimedia systems and formats will provide native support for Video, For example ATM systems:

• ABR is currently supported by most existing networks.

  CBR needs AAL 1 which supports Class A, i.e., real-time, constant bit rate, connection-oriented traffic

  VBR needs AAL 2 which takes care of variable bit rate

• MPEG2 Convergence to ATM - MPEG will be supported over AAL5 (ATM Adaptation Layer 5). A new Audio-Visual Service-Specific Convergence Sublayer (AVSSCS) will be developed.

Video Requirement        Support in ATM              Support without ATM
------------------   ------------------------   ------------------------------------
Bandwidth            Scalable to several Gbps           Up to 100 Mbps
Latency and Jitter        QoS support           Resource Reservation Protocol (RSVP)
CBR or VBR           AAL 1, 2, 5, LAN emulation,         p x 64 kbps
                     circuit emulation, etc.
Multicasting         Multicast switch, or              IP-multicast or 
                     permanent virtual circuit  Protocol-Independent Multicast (PIM)