Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-08-18
2002-03-19
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S467000
Reexamination Certificate
active
06359902
ABSTRACT:
BACKGROUND INFORMATION
The capabilities of the Internet for dissemination of data to and from various points on the Internet network are well established. For example, during point-to-point (“unicast”) communications over the Internet, a source workstation identified by a unique Internet address (“IP address”) attempts to transmit data to a single destination workstation, identified by a unique destination IP address. The path traveled by the data over the network to reach the destination is determined based on network “nodes”—e.g., routers physically implemented in the network to transmit data.
FIG. 1
illustrates a portion of a network
10
connecting a source workstation
12
and a destination workstation
20
for point-to-point communication. In this example, network nodes
14
establish a path
16
(denoted by arced vectors) for transmission of data between each workstation.
The Internet may also be used for dissemination of data from a single source to multiple destinations by what has been termed “multicasting.” For example, a presentation at a particular location can be converted (via camera and microphone) into video and audio data streams, and the video and audio data may then be communicated over the network to various destination workstations at remote locations. Presently, the Internet includes facilities within the network to facilitate such multicast transmissions of data from a single source to multiple destinations. Network nodes may include specific hardware/software to handle the routing of multicast transmission data. One example of such facilities is referred to as the “multicast backbone,” or “MBONE.” The MBONE permits data content (for example, audio and video data streams) to be routed over the Internet to multiple end-users which have “subscribed” to receive the data content. The network nodes operate to propagate the content to the correct end-user destinations.
FIG. 2
is a network diagram illustrating a portion of a network
30
implementing a prior art multicast transmission facility. A data source
32
is connected to the network
30
via a network node
40
a
(which is part of a collection of network nodes
40
). Data source
32
provides a data stream, for example, digital video and audio signals produced by a camera and/or microphone used to record a presentation. Note that the data stream may be transmitted in compressed or otherwise encoded form in order to reduce the network bandwidth needed to transmit the data stream. For example, as depicted in
FIG. 2
, the data source
32
transmits the data stream containing digital audio compressed using the G.711 compression standard and having a bandwidth of approximately 8 Kbits/s, and digital video compressed using the H.261 compression standard and having a bandwidth of approximately 200 Kbits/s.
The data stream traverses the network
30
over paths
38
(as shown by the arced flow vectors). The node
40
a
coupled to the data source
32
is first to receive the multicast transmission data. The transmission from the data source
32
is identified as a multicast transmission, for example, by identifying the destination IP address for the transmission as an address that is specially allocated to indicate a multicast transmission. For example, as presently defined, multicast transmissions are indicated by “class D” destination IP addresses (in the IP address range 224.x.x.x to 229.x.x.x). Thus any data being sent to a destination IP address in this range will be recognized and treated as a multicast transmission.
Upon identification of the transmission as a multicast transmission, the node
40
a
accesses a database indicating the actual destination IP addresses for those end-users that have subscribed to receive the particular multicast transmission. Subscription may be achieved, for example, via messages using the Internet Group Management Protocol (“IGMP”), by an end-user sending an e-mail message to an appropriate authority to request inclusion in the multicast transmission table, or by other means. Once the destination addresses for those who have subscribed to the transmission have been resolved (in this example, end users
42
) the node
40
a
replicates the data stream and transmits the data stream to those end-users
42
coupled to the node
40
a
. Furthermore, the node
40
a
routes the data stream to another node
40
for further replication and transmission to other end-users
42
who have subscribed to receive the multicast transmission. In this manner, the multicast transmission may traverse multiple paths
38
, as shown in FIG.
2
.
At any given time, several multicast transmissions may be in progress, the different multicast transmissions being distinguished, for example, by the different destination IP addresses that identify each transmission. Each multicast transmission may be described as a “multicast group” or “multicast channel.” In order to allow users to select which multicast group to receive, a “Session Description Protocol” (SDP) message is sent over the network. The SDP message includes basic information about the multicast program, such as the title, time and location of various multicasts being provided over the network. The end-user may then “tune in” to the desired multicast group using the information provided by the SDP message. The SDP transmissions are typically low-bandwidth uncompressed messages which can be accessed by most contemporary workstations operating in conjunction with even low-bandwidth network connections.
Multicast facilities are particularly useful in transmitting “real-time” (i.e., live) audio/video signals to multiple end-users. This audio/video data may be transmitted, for example, using the “Real time Transport Protocol,” also known as RTP. The RTP sets the format for transmitting data comprising multimedia (audio and/or video) or other signals over a network where real-time access is desired. For example, the RTP specifies the provision of packet numbering, timestamping, and other information about the data being transmitted that is useful for real-time data transmissions and reception. A more detailed description of RTP is given in Schulzrinne et al., “RTP: A Transport Protocol for Real-Time Applications,” IETF Network Working Group RFC 1889, January 1996.
As part of the RTP, end-user workstations that receive an RTP transmission will respond periodically by transmitting an “RTCP” (Real-time Transport Control Protocol) message. The RTCP message is used for various functions, such as indicating who is “listening” to the multicast transmission, and how well the transmission is being received. A more detailed description of RTCP is also given in the aforementioned Schulzrinne et al. reference.
Traditional multicast transmissions (and, in particular, transmissions over the MBONE) pose several problems for end-users, and particularly end-users that are part of a private network (e.g., a corporate network). The end-user equipment or private network interconnections that provide access to the user equipment may be unable to accommodate the bandwidth or decompression processing requirements of multicast data streams, thus preventing proper reception. For example, it is common in corporate networks that not every end-user have the same computer equipment or the same network connection, particularly in large networks. Another problem for private networks is that the content being provided via the multicast facilities of the Internet is not restricted or filtered, and also, unwanted/undesirable multicast transmissions may be accessible by end-users. Such unregulated access may cause network bandwidth problems that can severely degrade all network service. Furthermore, because multicast transmissions are received from outside the private network, multicast transmissions can serve as an access point for illegal entry into private networks.
SUMMARY OF THE INVENTION
According to the present invention, a multicast transmission gating system may be implemented. The multicast transmission gating system comprises a receiver to receive a multicast transmissio
Cangialosi Salvatore
Intel Corporation
LandOfFree
System for translation and delivery of multimedia streams does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for translation and delivery of multimedia streams, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for translation and delivery of multimedia streams will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2860912