Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-09-28
2004-11-23
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S389000, C370S395700
Reexamination Certificate
active
06822967
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a relay unit and a frame tracing method that relay frames between a sending terminal and a receiving terminal belonging to different networks and are suitable for use in a network relay unit for managing the history of the process of relaying such transmission-reception of frames.
(2) Description of the Related Art
FIG. 13
is a block diagram for explaining an example of how a general relay unit is used. A relay unit (network relay unit)
100
shown in the diagram relays the transmission-reception of a frame (packet) between a plurality-of networks (in
FIG. 13
, three networks A to C). The relay unit
100
is respectively connected to the networks A to C through I/O interfaces
101
a
to
101
c
such that a frame can be transmitted and received between the networks A to C.
For instance, when a frame is transmitted from a sending terminal belonging to the network A through the relay unit
100
to a receiving terminal belonging to the network B, the relay unit
100
receives the frame transmitted from the network A, through the I/O interface
101
a
and then judges a receiving end, for example, from information recorded on the header portion of the frame and then transmits the frame to the receiving end of the network B through the I/O interface
101
b.
In such a relay unit, tracing the history of the frame relaying operation is performed as a countermeasure at the time of a fault occurrence, for example.
FIG. 14
is a block diagram showing the construction of the aforementioned relay unit
100
in further detail. As shown in the diagram, the relay unit
100
is constituted by a CPU
102
, I/O interfaces
101
a
to
101
c
, a bus
103
, and a random access memory (RAM)
104
. With this arrangement, the relay unit
100
relays the transmission-reception of a frame between a plurality of networks A to C.
The I/O interfaces (hereinafter referred to as simply interfaces)
101
a
to
101
c
are respectively connected to the networks A to C, as previously described, and are also connected to the CPU
102
and the RAM
104
through the bus
103
, whereby a frame can be delivered between the relay unit
100
and each of the networks A to C.
The RAM
104
stores various kinds of data or the like. This RAM
104
ensures both an area for a transmitting-receiving buffer
104
b
that temporarily stores a frame received from a sending terminal and an area for a trace buffer
104
a
that stores the whole or part of the frame stored in the transmitting-receiving buffer
104
b.
The bus
103
interconnects the interfaces
101
a
to
101
c
, the CPU
102
, and the RAM
104
, as previously described, and delivers various kinds of data or the like.
In the relay unit
100
, the CPU
102
controls operation of the interfaces
101
a
to
101
c
, the RAM
104
and the like, thereby executing the frame relaying process and the frame tracing process as described infra.
FIG. 15
is a diagram for explaining a conventional frame tracing method in the relay unit
100
shown in FIG.
14
. As shown in
FIG. 15
, the relay unit
100
temporarily stores a received frame in the transmitting-receiving buffer
104
b
and then copies the whole or part of the frame stored in the transmitting-receiving buffer
104
b
to the trace buffer
104
a.
For example, when data is transmitted from a terminal A
1
of the network A to a terminal B
1
of the network B through the relay unit
100
by the aforementioned construction, in the relay unit
100
the frame transmitted from the terminal A
1
is received by the interface
101
a
as shown in
FIG. 14
, and this frame is temporarily stored in the transmitting-receiving buffer
104
b
of the RAM
104
through the bus
103
, as shown by a dotted arrow a in FIG.
14
.
Also, in the relay unit
100
, either the whole frame stored in the transmitting-receiving buffer
104
b
or a portion of the frame including its header portion is copied in sequence to the trace buffer
104
a
of the RAM
104
.
And the CPU
102
refers, for example, to information about the protocol header included in the header portion of the frame stored in the transmitting-receiving buffer
104
b
and then recognizes, based on the address or the like of the receiving end (terminal B
1
), that a network to which the terminal B
1
belongs is the network B. After recognition, the CPU
102
transmits the frame from the transmitting-receiving buffer
104
b
through the bus
103
to the interface
101
b
connected to the network B, as shown by a dotted arrow b in FIG.
14
. The interface
101
b
receiving the frame from the transmitting-receiving buffer
104
b
transmits the frame to the network B.
In addition, for example, in the case where the transmission of a frame has been completed or where the frame is abandoned by reasons such that no receiving end is found, the CPU
102
releases an area where the frame was stored, from the transmitting-receiving buffer
104
.
In this manner, in the relay unit
100
, the transmission-reception of a frame is relayed between a plurality of networks and also the whole or part of the relayed frame is stored in the trace buffer
104
a
as data to be traced (trace data). Trace data is thus stored in the trace buffer
104
a
, whereby the history of the relaying operation in the relay unit
100
can be managed.
And the trace data, which was stored in the trace buffer
104
a
, is traced and analyzed. With this, which I/O operation (relaying operation) has been performed can be known. Therefore, the trace data becomes important information, for example, when a fault is checked or when debugging is performed. Particularly, in the case where the relay unit
100
is operated with firmware, for example, it becomes important information.
However, in the conventional frame tracing method in the aforementioned relay unit
100
, in the RAM
104
the whole or part of the frame stored in the transmitting-receiving buffer
104
b
is copied in sequence to the trace buffer
104
a
, but generally the speed of accessing (reading and writing) memory is considerably slower compared with the command executing time in the CPU
102
and therefore in the RAM
102
the process of copying data from the transmitting-receiving buffer
104
b
to the trace buffer
104
a
takes substantial time. For this reason, there is also a possibility that the copying process will increase the overhead time in the CPU
102
and constitute a hindrance to the relaying operation.
On the other hand, in Japanese Laid-Open Patent Publication No. HEI 4-135348, in a LAN controller a method is disclosed which directly writes the head portion of a frame including its header to a trace buffer and also writes the remaining portion excluding the head portion to a transmitting-receiving buffer, in order to eliminate copying a frame between memories and enhance the processing speed.
However, this method has to provide a dedicated trace buffer or previously ensure an area for a trace buffer onto memory. When a dedicated trace buffer is provided, an increase in the manufacturing cost will be incurred. Also, when an area for a trace buffer is previously ensured on memory, an area on the memory cannot be effectively utilized.
Furthermore, when the method disclosed in the aforementioned publication is applied to the relay unit in which a frame received from a sending source, as it is, is transmitted to a receiving terminal, the received frame has to be divided into two parts and stored in different buffers. Subsequently, the two parts must be read out from the different buffers and again transmitted as a single frame. That is, the aforementioned method requires both the process of dividing a frame when it is received and the process of reconstituting the divided parts when they are transmitted, so that there is also a problem that the process will become complicated.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned problems. Accordingly, it is an object of the present invention to provide a relay unit and a frame
Kizou Hassan
Odland David
Staas & Halsey , LLP
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