Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-08-21
2002-03-19
Marcelo, Melvin (Department: 2733)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395430
Reexamination Certificate
active
06359885
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fixed length packet switching apparatus (asynchronous transfer mode switching apparatus) which is used for building a B-ISDN (Broadband-Integrated Service Digital Network), and particularly, to an improved multi-channel packet switching apparatus which is composed of a multi-channel switch structure having a physically/logically configured multipoint-to-multipoint connection between input and output ports and is capable of preventing a cell loss and checking a lost cell.
2. Description of the Conventional Art
The technique concerning the ATM (Asynchronous Transfer Mode) which is capable of performing a transmission and exchange operation by the fixed length packet unit is important for building the B-ISDN (Broadband-Integrated Serivce Digital Network). In particular, the switching system which is one of the major systems in the communication network is implemented based on the ATM switching technique. In order to implement the above-described purposes, much study has been performed concerning the ATM switch structure. Switches which have been developed as a result of the above-described studies are currently used in the industry.
There are various ranges of speed of a link for the B-ISDN. In the B-ISDN, the information should be transmitted/received at a high speed. The basic speed of information was 155 Mbps which is the equivalent of an STM-1 (Synchronous Transfer Mode-1) and 622 Mbps which is the equivalent of an STM-4. However, 2.5 Gbps, 10 Gbps, even 100 Gbps are recently required for the high speed Gigabit Transport Network. The ATM system having a low speed of 25 Mbps, 51 Mbps, etc. may be used for Subscriber Access Network for the reason that the service network should be established at low cost. Therefore, a new switching system should have the capability of effectively adapting the above-described various channel speeds, that is multichannel switching capability.
However, the conventional switching system adapts a single channel switching method which is directed to a single-to-single interrelationship between the input and output ports for the switch network. In more detail, the single channel switching method is directed to a method wherein the output port physically and logically has one link. Therefore, the operations for allocating the bandwidth in a switch network and setting a routing path are independently implemented with respect to each port.
The multi-channel switching method is configured based on a multi-to-multi connection method between the input and output ports, and a plurality of input and output links are grouped to one link, so that the link group is logically operated as one port. Namely, since the inputted cells are provided with a routing path through one port in the group which has the same logic cells, the path setting is performed based on much opportunity, and since the total band width of a plurality of links in one logic port are shared at the maximum, it is possible to effectively use the assigned boardwidth, so that the burst characteristic of the ATM traffic is implemented.
Therefore, the system can concurrently use the input and output links, which require different speeds, through one switch network by using the above-described multi-channel switching technique. In this case, a time sharing multiplexing and demultiplexing unit which has a simple function is added to the system, whereby it is possible to configure a system which is capable of adapting various speed ranges. Therefore, it is possible to reduce the cost which is required for the system which is capable of adapting various transmission speeds.
A switching technique is disclosed for providing a few multi-channel switching functions based on the above-described demands.
Achille Pattavina disclosed a method for implementing multi-channel switching using a Batcher Banyan network in the article “Multi-channel Bandwidth Allocation in a Broadband Packet Switch: IEEE JSAC, Vol. 9, Dec. 1988, pp 1489-1499”. The switching apparatus which was disclosed in the above-described article is directed to using an input buffer method which checks whether a path allocation is performed and then routes a cell. Therefore, the cell loss does not occur in the switch network; however, a head-off line blocking phenomenon occurs, as a result of the input buffer method. Therefore, the cell processing capability is decreased. In addition, since there is not provided a function for preserving the sequence of cells in the switching system itself, the cell sequence should be adjusted at an end point.
Hyong S. Kim disclosed a method werein a switching apparatus is operated by a virtual FIFO (First In first Out) method in order to support a cell sequence preserving function in the article “Multi-channel ATM switch with Preserved Packet Sequence: ICC 92, 1992, pp 1634-1636”. This method requires an internal buffer in the switch network. In this method, it is possible to preserve the sequence of the cells; however, the buffer should be configured to have a sharing buffer type in order to reduce the capacity of the buffer, and two memory pointers are required for providing the characteristic of the FIFO, whereby the method for controlling the memory becomes complicated. In addition, since the cell storing and cell output for the memory are concurrently processed with respect to an N-number of switch input and output ports, the memory should be virtually divided into an N-number of memory spaces. Therefore, the memory control may be complicated, and the size of the switch is increased. In addition, when the port requires a high speed operation, the system becomes complicated under the condition such as memory access time.
The function for preserving the sequence of the cells from the switching system is the most important function. In particular, in the multi-channel switching method, the above-described function is considered as the more important function. Namely, when outputting the cells from one input link and the cells are divided into several input links and inputted through one virtual path to the grouped port composed of a plurality of output links, the output sequences of the cells are maintained.
However, in most conventional multi-channel switching methods, the function for preserving the output sequence of the cells is not included in the switching network. Namely, the cell to which sequence information is added is transferred to a service end point, and then the sequence of the cells are adjusted using a buffer mechanism at the service end point.
Therefore, both the end points of the service should be provided with a predetermined protocol for preserving a desired cell sequence, and such protocol should be identical at both the end points. In addition, since the sequence information is added to a payload of the cell, the transmission efficiency of the cell is decreased.
In addition, a copy function of a cell should be included in the switching network for providing a multi-casting service. Many switches among the conventional space division switches process a cell copy and a routing operation to an output port of the copied cells using an additionally provided network. Namely, a method, in which a desired number of ports is copied, and a path is designated through a routing network with respect to each of the copied cells, is used.
In order to implement the above-described method, the cell is copied to a plurality of output ports, respectively, in accordance with information with respect to a predetermined amount (the number of fanouts) for the copy, and the routing network allocates to a corresponding path in accordance with information of the final output port of a corresponding cell with respect to each cell which is divided to multiple ports and outputted.
Here, the conventional switch has a problem in that two network, namely, the copy networks and the routing network, are required for the multi-casting service, and a large capacity look-up table is required between the two networks.
In other words, th
Kim Keun Bae
Kim Kyeong-Soo
Min Paul S.
Schmid Otto
Cohen & Pontani, Lieberman & Pavane
Electronics and Telecommunications Research Institute
Marcelo Melvin
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