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Method for the Conversion of Multimedia Streams to Packet Streams

IP.com Disclosure Number: IPCOM000112603D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 118K

Publishing Venue

IBM

Related People

Hauris, J: AUTHOR [+3]

Abstract

Most LAN and WAN networks are packet-based. However, multimedia sources of information (e.g., voice, audio, and video) are isochronous (and analog) in nature. This means that the isochronous information must first be organized into discrete packets which are then transferred across the network.

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Method for the Conversion of Multimedia Streams to Packet Streams

      Most LAN and WAN networks are packet-based.  However,
multimedia sources of information (e.g., voice, audio, and video) are
isochronous (and analog) in nature.  This means that the isochronous
information must first be organized into discrete packets which are
then transferred across the network.

PROBLEM - Presently, the isochronous/multimedia information is sent
to the system memory where it is packetized by software algorithms.
This introduces extensive additional latency into the transmit and
receive paths.  A major problem in multimedia networking is this
end-to-end delay.  The end-to-end delay through a network must be
approximately 150 - 200 milliseconds.  The software packetization
process usually adds an additional 100 - 500 milliseconds.

      Thus, there is a cumbersome software conversion process between
the multimedia traffic and the packets, in order to permit the
existing packet networks (i.e., Token Ring, Ethernet, and FDDI) to
carry multimedia applications.

      Current routing algorithms employ large lookup tables for
general-purpose routing of packets through a network.  For
peer-to-peer applications where the number of destinations on the
system backplane is limited, these large tables are not required.
Therefore, a simpler hardware-assist routing algorithm is proposed
which improves performance for peer-to-peer transfers.

      A hardware-assisted conversion process was developed which
maintains compatibility between existing packet networks and the new
multimedia sources of information, and which eliminates additional
delay in converting between the multimedia/isochronous information
and the packet formats.  (This process implements a protocol/format
conversion.)  The hardware converter exists on the communication
adapter and thus allows the multimedia traffic to be transferred
directly between the multimedia source and the packet network
(without having to go through system memory or any other adapter).
This direct transfer process is known as "peer to peer" on the
backplane system bus.  (The hardware-assisted converter is referred
to as the Hardware Assist For Peer To Peer (HAPP)).

      The HAPP consists of a transmit section and a receive section.
Each section is programmable to accommodate various
multimedia/isochronous information sources and packet networks.

TRANSMIT - Based on the data rate of the multimedia source and the
characteristics of the packet network the HAPP determines an optimal
packet size.  The packet size is either given (as in ATM) or
calculated (as in FDDI and Token Ring).  The optimal packet size (for
a maximum of a single frame), or number of frames in the case of
maximum sized frames, is calculated as follows:

1.  PSize = (MMBitRate x NetAcc) / 8   for packets less than or equal
to the maximum frame size.

2.  PNmbrM = (MMBitRate x NetAcc) / (8 x MaxPac)    for packets that
would b...