Network communication device

Details Network communication device Network communication device

1997-10-24

2001-02-27

Nguyen, Chau (Department: 2739)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S395430

Reexamination Certificate

active

06195361

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to network communication devices, such as ATM (Asynchronous Transfer Mode) switches, which discard invalid packets.
2. Description of the Background Art
The network communication devices on a network like the Ethernet switch and the ATM switch handle masses of data (hereinafter referred to as packets) as units. Such network communication devices switch packets through hardware to realize high throughput. The ATM switch is the hardware for switching lines. It is determined by an international recommendation that the ATM switches should handle fixed-length (53-byte) packets. Among the packets, fixed-length packets are called “cells.”
FIG. 22
is a diagram showing the concept of an example of a conventional ATM switch
100
a
. Input lines IN#
1
-
4
and output lines OUT#
1
-
4
are connected to the ATM switch
100
a
. An input portion
11
is connected to the input lines IN#
1
-
4
. An output portion
13
is connected to the output lines OUT#
1
-
4
. A line interface
11
a
, a destination analyzing portion
11
b
and an in-device interface
11
c
are provided for each of the input lines IN#
1
-
4
. A line interface
13
a
, a destination adding portion
13
b
and an in-device interface
13
c
are provided for each of the output lines OUT#
1
-
4
. The input portion
11
receives cells provided with destinations from the input lines IN#
1
-
4
. In the input portion
11
, data in the cells (cell data) are transferred to the switch portion
12
through the line interface
11
a
, the destination analyzing portion
11
b
for analyzing the destinations and adding in-device management information to the cell data, and the in-device interface
11
c.
Next, the switch portion
12
outputs the cell data to the in-device interfaces
13
c
corresponding to the destinations. In the output portion
13
, the cells are transferred to the target lines through the in-device interface
13
c
, the destination adding portion
13
b
for removing the in-device management information added to the cell data and adding destinations to the cells, and the line interface
13
a
. Thus, the switch portion
12
transfers the cells received from the plurality of input lines to the output lines corresponding to the destinations.
When a plurality of cells directed to a certain output line are received from a plurality of input lines at the same time, the cell data collide (congestion). To avoid the congestion, first, the switch portion
12
once stores the plurality of cell data received from the plurality of input lines into the built-in buffer memory BM. The plurality of cell data directed to a certain output line stored in the buffer memory BM are placed in the wait state until that output line is freed. When the output line becomes free, the switch portion
12
outputs the plurality of cell data directed to that output line to the output portion
13
.
The ATM switches containing such a buffer memory BM include those called “shared-buffer ATM switches.” The shared-buffer ATM switches include that described in the collection of preparatory manuscripts, Masahiko Ishiwaki et al., “Efficient Self-timed Queue Architecture for a shared-buffering ATM Switch”, Institute of Electronics, Information and Communication Engineers of Japan, Integrated Circuit Study Group, ICD94-67, June 1994.
A flow of a plurality of cells (a data stream) may become invalid. This is caused by a trouble on the network or in a terminal connected to the network, for example. Such a trouble is caused when a trouble, e.g., a data error, occurs, or when a request from a source party for connecting the line (hereinafter referred to as “a call”) is unexpectedly disconnected, or when a data stream with low priority is interrupted due to congestion of cells on the network, for example.
The capability of managing the cell data in the conventional buffer memory BM is limited. The cell data are, mainly, managed only with the destinations. For example, this management cannot identify cell data belonging to an invalidated data stream. Accordingly, the conventional ATM switch
100
a
cannot discard invalid cells in the switch portion
12
, but the input portion
11
and the output portion
13
discard the invalid cells. For example, suppose that discarding information for informing that cells belonging to a particular data stream are discarded was issued outside of the ATM switch
100
a
and then the ATM switch received the discarding information. Then the input portion
11
of the ATM switch
100
a
discards the cells corresponding to the discarding information among the received cells, or the output portion
13
of the ATM switch
100
a
discards the cells corresponding to the discarding information.
The ATM switch
100
a
requires high speed performance. Particularly, when a data stream with low priority is interrupted due to congestion of cells on the network, it is preferable to immediately discard the invalid cells. If the cells are not discarded at once, the congestion cannot be avoided.
In the conventional ATM switch
100
a
, however, the switch portion
12
does not discard invalid cells. Accordingly, the invalid cells cannot be discarded while they exist in the buffer memory BM. After the cell discarding information has been received, the invalid cells are discarded when the corresponding output line has become free and the switch portion
12
has outputted the invalid cells directed to that output line into the output portion
13
. Thus, the conventional ATM switch
100
a
has the problem that even if invalid cells are accumulated in the buffer memory BM, they cannot be discarded at once.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a network communication device comprises: a storage area for storing a plurality of received packets received from a plurality of input lines; and received packet managing means for managing management data corresponding to the plurality of received packets in a one-to-one manner and each including a tag for identifying a call related to the corresponding received packet and a write address of the corresponding received packet in the storage area; wherein the received packet managing means comprises packet managing detecting means receiving discarding information for discarding a packet and the tag, for detecting the management data having the tag corresponding to the discarding information, and discards the management data detected by the packet managing detecting means.
Preferably, according to a second aspect of the present invention, in the network communication device, the received packet managing means further comprises management data storing means having a plurality of stages connected in series, for storing each management data into each of the plurality of stages in the order of reception from a preceding stage to a following stage, and management data overwriting means for overwriting, into a stage in which the management data detected by the packet managing detecting means is stored, the management data in the following stage.
Preferably, according to a third aspect of the present invention, in the network communication device, the management data further comprises a destination of the corresponding received packet, wherein the packet managing detecting means invalidates the destination of the detected management data, and the management data overwriting means overwrites, into the stage in which the management data with the invalid destination is stored, the management data in the following stage.
Preferably, according to a fourth aspect of the present invention, in the network communication device, the packet managing detecting means includes a plurality of packet managing detecting means each provided for each stage, and the network communication device further comprises discarded number detecting means for totalizing results detected by the individual packet managing detecting means.
Preferably, according to a fifth aspect of the present invention, in the netwo

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