Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-06-06
2004-10-19
Patel, Ajit (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S522000
Reexamination Certificate
active
06807185
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to multimedia systems and, more specifically, to a system and method for achieving true endpoint-to-endpoint signalling without the need to establish a user information path until the path is required to complete a call between the endpoints.
BACKGROUND OF THE INVENTION
Currently, “Information superhighway” and “multimedia” are probably the most often spoken and least often understood aspects of a coming revolution in data communication. Although issues specific to an information superhighway are beyond the scope of the present discussion, interactive multimedia systems are very much within the present scope.
An interactive multimedia system is broadly defined as a system capable of processing, storing, communicating and coordinating data pertaining to visual information, aural information and other information. Visual information is generally divided into still picture or graphics and full motion video or animation categories. In the vernacular of those involved in multimedia, such visual information is generically referred to as “video.” Aural information is generally divided into speech and non-speech categories and is generically referred to as “voice.”“Other information” is directed primarily to computer data, often organized in files and records, and perhaps constituting textual and graphical data. Such computer data are generally referred to as “data.”
To date, multimedia has, for the most part, been limited to stand-alone computer systems or computer systems linked together in a local area network (“LAN”). While such isolated systems have proven popular and entertaining, the true value of multimedia will become apparent only when multimedia-capable wide area networks (“WANs”) and protocol systems are developed, standardized and installed that permit truly interactive multimedia. Such multimedia systems will allow long distance communication of useful quantities of coordinated voice, video and data, providing, in effect, a multimedia extension to the voice-only services of the ubiquitous telephone network.
Defining the structure and operation of an interactive multimedia system is a critical first step in the development of such system. Accordingly, before entering into a discussion herein of more specific design issues, it is important to discuss more general questions that need to be resolved concerning design objectives of the system as a whole and some generally.agreed-upon answers and specifications.
Interactive multimedia may be thought of as an electronic approximation of the paradigm of interactive group discussion. It involves the interactive exchange of voice, video and data between two or more people through an electronic medium in real time. Because of its interactive and real-time nature, there are some stringent requirements and required services not normally associated with multimedia retrieval systems. Some of the more obvious examples of those requirements and services include latency (transmission delay), conferencing, availability (“up-time”) and WAN interoperability.
The evolution of existing private branch exchange (“PBX”) and LAN topologies towards a composite interactive multimedia system based upon client/server architectures and isochronous networks is a natural trend. However, to merge the disparate mediums of voice, video and data successfully into a cohesive network requires that three fundamental integration issues be defined and resolved. The first of the fundamental integration issues is quality of service (“QoS”). QoS is defined as the effective communication bandwidth, services and media quality coupling of separate equipment or “terminals” together and the availability (“up-time”) of the same. QoS parameters are divided into four groups: 1) terminal QoS, 2) network QoS, 3) system QoS, and 4) availability requirements. Thus, QoS parameters must be defined for both terminal equipment (“TE”) and network equipment (“NE”) governing the communication of data between the TE. System QoS is derived from a combination of terminal and network QoS. The suggested values for QoS parameters are considered to be a practical compromise between required service quality, technology and cost. See, Multimedia Communications Forum (“MMCF”) Working Document “Architecture and Network QoS”, ARCH/QOS/94-001, Rev. 1.7, MMCF, (September 1994) and ITU-T Recommendation I.350 “General Aspects of Quality of Service and Network Performance in Digital Networks, including Integrated Services Digital Networks (“ISDNs”), (1993). The following Table I summarizes some suggested parameters for terminal QoS.
Parameter
Parameter Type
Parameter Value
Explanation
Audio Frequency
3.4 kHz
Optimization is for
Range
voice, and is
consistent with
existing Legacy
voice systems.
Audio Level
−10 dBmO
Optimization is for
voice, and is
consistent with
Legacy voice
systems.
Audio Encoding
G.711 (8-bit pulse
Consistent with
code modulation
Legacy voice
(“PCM”))
systems.
Video Resolution
≧352 × 288 (SIF)
Minimal acceptable
size for video
conferencing.
Video Frame Rate
≧20 frames per
Minimal
second (fps)
optimization for
detection of facial
expression
transitions.
Voice/Video
<100 milliseconds
A differential
Intramedia-
(ms)
delay greater than
Intermedia
100 ms between voice
Differential Delay
& video is
noticeably
significant.
Video Encoding
H.261 & Motion
H.261 meets WAN
Picture Experts
interoperability,
Group (“MPEG”)-1
MPEG-1 is more
consistent with
desktop trends and
quality
requirements.
Intramedia Latency
<100 ms
The delay of the TE
(TE)
itself for encoding
and framing
purposes.
TABLE I
Terminal QoS Parameters
Parameter
Parameter Type
Parameter Value
Explanation
User Data Rate
≧64 kbps
Minimal acceptable
data bandwidth for
data sharing
applications.
Consistent with
ISDN Basic Rate
Instrument (“BRI”).
Data Encoding
HDLC encapsulation
Consistent with
isochronous service
bearer channels.
Network QoS parameter requirements consist of those parts of the system that are between two TE endpoints. This includes a portion of the TE itself, the private network (if required), and the public network (if required). Some of the requirements imposed upon the network QoS are a result of the terminal QoS parameters. The following Table II summarizes the network QoS requirements.
TABLE II
Network QoS Parameters
Parameter
Parameter Type
Value
Parameter Explanation
Intramedia Latency
<50
ms
Intramedia latency is
(NE)
the delay between
source TE transmis-
sion and destination
TE reception; i.e.
the delay of NE.
Network Capacity
≧1,536
kbps
G.711 Audio (64
kbps), MPEG-1 Video
(1,344 kbps), HDLC
data (128 kbps).
The system QoS encompasses the terminal and network elements. The particular value critical to the system is the intramedia latency. The following Table III summarizes this value that is the sum of the terminal and network values for the same parameter.
TABLE III
System QoS Parameters
Parameter Type
Parameter Value
Parameter Explanation
Intramedia Latency
<150 ms
Intramedia latency is
(System)
the delay between
source transmission
and destination
reception. It
includes latency
imposed by the source
and destination TEs
as well as the NE.
These latency values
might include
encoding and decoding
delays, transmission
delays, and
adaptation delays.
The system QoS parameter of Intramedia Latency is the sum of twice the TE and the NE latency. Intramedia Latency parameter value is bounded by voice requirements since latent delay is more readily perceived by the ear than the eye. However, the delay itself is typically a function of video since it is the component requiring the most time for encoding and decoding.
Availability (“up-time”) includes several aspects. In particular, the network elements have very strict requirements. These requirements are typical of private branch exchanges (“PBXs”) and other private network voice equipment, but are very atypical of Legacy LANs. Most LANs are susceptible to power-losses, single points of failure, and errant TE. An interactive multimedia system must
Bell Robert T.
Platt Richard J.
Baker & Botts L.L.P.
Cisco Technology Inc.
Patel Ajit
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