Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-07-30
2004-04-06
Vanderpuye, Kenneth (Department: 2631)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395100
Reexamination Certificate
active
06717948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention.
This invention relates in general to a network communications, and more particularly to a knowledge-based connection admission method and apparatus for providing efficient multiplexing of data and speech over AAL
2
.
2. Description of Related Art.
ATM has been selected as a world standard for broadband ISDN in network communication systems. ATM systems have been implemented on a global basis and developed in a rapid growth. ATM technology is destined to play a major role in both public and private broadband networks. AAL
2
is one of the four types of AAL (ATM Adaptive Layer) protocols which have been recommended by CCITT (now ITU-T), namely AAL
1
, AAL
2
, AAL
3
/
4
and AAL
5
. In general, the layer services provided by AAL
1
are constant bit rate (CBR) services which require information to be transferred between source and destination at a constant bit rate. AAL
2
offers a transfer of information with a variable bit rate. In addition, timing information is transferred between source and destination. Since the source is generating a variable bit rate, it is possible that cells are not completely filled and that filling level varies from cell to cell. AAL
3
/
4
is used for transfer of data which is sensitive to loss, but not sensitive to delay. The AAL
3
/
4
protocol may be used for connection oriented as well as for connectionless data communication. AAL
3
/
4
itself does not perform all functions required by a connectionless service, since functions like routing and network addressing are performed on the network layer. AAL
5
is designed to offer a service with less overhead and better error detection below the common part of the convergence sublayer (CPCS).
The AAL
2
signaling protocol describes methods by which a switched AAL
2
connection can be established between two AAL
2
end users across a network that consists of both ATM and AAL
2
switches. The important function of AAL
2
signaling protocol is to establish an AAL
2
connection between two AAL
2
end points on a concatenation of ATM Virtual Channel Connections (VCCs) that are either on demand (SVC) or semi-permanent (PVC). Some the basic requirements of AAL
2
signaling protocol include the ability to establish an AAL
2
connection between AAL
2
end systems that support AESA formats, the ability to support hop-by-hop routing mechanism between AAL
2
end systems, the ability to indicate any failures to corresponding management entity, and the ability to setup AAL
2
connections with different Quality-of-Service (QoS) requirements. In AAL
2
, packets (minicells) from many users are assembled into a single ATM cell and transmitted on the same ATM connection. In addition, packets are allowed to straddle across ATM cell boundary to maximize the bandwidth utilization.
The success of ATM in wireline network has given impetus to the wireless network operators to adopt ATM for efficient use of network resources and able to support growing demands for different services. With AAL
2
, low bit rate and delay sensitive applications, such as mobile telephony, share a common ATM VCC thus increasing statistical multiplexing efficiency. Bandwidth efficiency, due to AAL
2
for delay sensitive speech traffic, has been confirmed by simulation studies and commercial products available today.
The AAL
2
standard consists of Common Part Sublayer (CPS) and Segmentation and Reassembly Service Specific Convergence Sublayer (SAR-SSCS ). The CPS standard describes the procedures involved in multiplexing packets from different users on a single ATM VCC and the SAR-SSCS standard specifies ways to carry packets that are larger than 64 bytes in AAL
2
.
The procedure involved in transmitting data over AAL
2
is similar to AAL
5
. A data packet received from a user is added 8 byte Service Specific Transmission Error Detection Sublayer (SSTED) trailer similar to AAL
5
trailer. Even though, SAR-SSCS specification describes three different ways to transmit a data packet, the SSTED trailer is added to obtain similar services offered by AAL
5
. The main difference between AAL
5
and AAL
2
is the padding, which is not needed in AAL
2
. If the size of a data packet is larger than 64 bytes then it is segmented into multiple of 64 bytes. Each segment is converted into CPS-Packet with a 3 byte header and passed to the CPS layer for AAL
2
multiplexing. The CPS layer assemble these minicells in ATM cells and transmit them to remote AAL
2
peer entity. The maximum size of a data packet is limited to 65535 octets in SAR-SSCS.
Recently, there has been considerable interest in multiplexing best effort data traffic along with speech to achieve the maximum bandwidth efficiency in the output ATM link. However, with current multiplexing method and apparatus, speech and best effort data traffic are separated, with one VCC handling one type of traffic and a second VCC utilizing another AAL standard for handling another type of traffic, i.e., different Quality of Service. If there are not ATM cells to transmit from the first VCC, then ATM cells from the second VCC will be transmitted automatically. This is a standard procedure implemented in ATM switches that are available today.
Nevertheless, AAL
2
introduces a situation where the leftover bandwidth in one of the VCCs may not be used for any best effort data traffic. This may lead to ATM cells in one of the VCCs being partially filled resulting in in-efficient bandwidth utilization. Thus, potentially available bandwidth can not be used by any other traffic that passes through the ATM switch.
It can be seen that there is a need for a connection admission method and apparatus that uses knowledge-based techniques to decide when and what type of data traffic will be multiplexed with speech traffic in ATM Adaptation Layer
2
(AAL
2
) environment.
It can also be seen that there is a need for a connection admission method and apparatus that supports low bit rate and delay sensitive applications such as mobile telephony in an ATM environment.
It can also be seen that there is a need for a connection admission method and apparatus that maximizes the use of available bandwidth.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a knowledge-based connection admission method and apparatus for providing efficient multiplexing of data and speech over AAL
2
.
The present invention solves the above-described problems by using a knowledge-based technique to decide when and what type of data traffic will be multiplexed with speech traffic in ATM Adaptation Layer
2
(AAL
2
) environment. The knowledge-based connection technique supports low bit rate and delay sensitive applications such as mobile telephony in an ATM environment by maximizing the use of available bandwidth.
A method in accordance with the principles of the present invention includes monitoring ATM cells for a AAL
2
connection, determining whether the ATM cells contain unused bytes and multiplexing data traffic with speech traffic on the AAL
2
connection when the data meets a predetermined set of requirements.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the multiplexing further includes determining whether the data traffic requires a bandwidth that exceeds a bandwidth provided by the unused bytes and multiplexing the data traffic with the speech traffic when the bandwidth required by the data traffic does not exceeds the bandwidth provided by the unused bytes.
Another aspect of the present invention is that the multiplexing further includes determining whether the data traffic requires a bandwidth that exceeds a bandwidth provided by the unused bytes and preventing the multiplexing of the data traffic with the speech traffic when the bandwidth required by the data traffic exceeds
Nokia Corporation
Squire Sanders & Dempsey L.L.P.
Vanderpuye Kenneth
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