Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Patent
1995-08-04
1997-11-18
Marcelo, Melvin
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
370397, H04L 1256
Patent
active
056894996
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to managing the statistical multiplexing of data in digital communication networks which employ the Asynchronous Transfer Mode of multiplexing, transmission and switching.
BACKGROUND OF THE INVENTION
The telephone industry is moving within the Standardisation Sector of the International Telecommunications Union to define the concept of a Broadband Integrated Services Network or B.sub.-- ISDN. This B.sub.-- ISDN is to be capable of providing a complete range of services, including telephone, television and data, with all services being multiplexed onto the network over a defined User Network Interface (UNI). Switches within the network are interconnected over a defined Network Node Interface (NNI).
Information for all services within the Broadband Integrated Services Network is conveyed and switched in irregularly occurring fixed size segments called cells, with the method of cell handling referred to as the Asynchronous Transfer Mode (ATM). ATM is a connection oriented technique where ATM level connections are established between service users by means of a call set up or signalling process, or alternatively administratively by network management. Connections may be established for the duration of a call or information transfer, or they may be established on a permanent or semi-permanent basis. The ATM cell has a header block which carries a label necessary to associate cells belonging to the same virtual connection.
In terms of protocol architecture the ATM layer sits immediately above the physical or transmission layer, and has two hierarchical sub-layers. These are the lower Virtual Path (VP) sub-layer and the higher Virtual Channel (VC) sub-layer. The Virtual Channel describes the unidirectional flow of ATM cells marked by a unique identifier called the Virtual Channel Identifier (VCI) which is carried in the cell header. The Virtual Channels are associated by a common unique identifier called the Virtual Path Identifier (VPI) which is also carried in the cell header. Virtual Channels are thus transported within Virtual Paths which are used to aggregate the Virtual Channels.
In accepting connections over the B.sub.-- ISDN the network operator needs to confirm that sufficient network resources are available to sustain the connection end-to-end at its required Quality of Service and without affecting the service guarantees of the existing connections. To assist in the process of Connection Admission Control the network user is required to characterise its traffic and specify the required Quality of Service. The digital information generated by a source may be characterised by its average bit rate, burstiness, peak duration and other such measures. However for purposes of ATM connection admission, ITU Draft Recommendation I.371 sets out that the traffic on a requested connection be characterised solely by the peak cell rate. If adequate network resources are available to sustain a new connection at its required Quality of Service at the indicated peak cell rate, the connection would be accepted by the network which would then monitor the traffic flow to ensure that the agreed rate is not violated. Although ITU Recommendation 1.371 indicates that other parameters besides peak cell rate may be introduced in the future, the present provision is for peak cell rate only, and the provision applies to connections equally at the VP and the VC sublayers.
To assist in the understanding of the significance of the present invention, it is useful to explain why for ATM carried communications in general, definite restrictions on traffic rates over both VP and VC connections are necessary, not only because of the provisions of the ITU Recommendation but for satisfactory operation of the ATM network. An accepted precept for the ATM network is that switching will be done in both the VP and the VC levels. Switching at the VP level would mean that ATM cells entering an input port of a switch would according to the particular VPI label be transferred to a specific output port
REFERENCES:
patent: 5173897 (1992-12-01), Schrodi et al.
patent: 5260935 (1993-11-01), Turner
patent: 5301193 (1994-04-01), Toyofuku et al.
Budrikis Zigmantas Leonas
Cantoni Antonio
Hullett John Leslie
Curtin University of Technology
Marcelo Melvin
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