Network system

Details Network system Network system

2000-03-20

2004-04-13

Pham, Chi (Department: 2667)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

Reexamination Certificate

active

06721319

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a network system such as a local area network system using Ethernet as a protocol.
2. Description of the Related Art
A constructional example of a conventional LAN system is shown in FIG.
1
. The system of
FIG. 1
is a network system
10
by an Ethernet LAN (or IEEE802.3 LAN) as a typical LAN.
In
FIG. 1
, hub apparatuses
1
-
1
and
1
-
2
and terminal apparatuses
1
-
3
to
1
-
5
,
1
-
20
, and
1
-
21
are connected through LAN cables and network connecting circuits.
For example, the hub apparatus
1
-
1
and terminal apparatus
1
-
3
are connected through an LAN cable
1
-
12
and a network connecting circuit
1
-
6
. Although the network connecting circuit
1
-
6
is positioned in the terminal apparatus
1
-
3
in
FIG. 1
, it can be arranged out of the terminal apparatus
1
-
3
.
The terminal apparatus
1
-
3
is connected to one port
1
-
7
of a plurality of ports
1
-
7
,
1
-
8
,
1
-
14
,
1
-
17
,
1
-
18
, and so on disposed in the hub apparatus
1
-
1
through the network connecting circuit
1
-
6
and cable
1
-
12
.
As for ports other than the port
1
-
7
which the hub apparatus
1
-
1
have, the port
1
-
8
is connected to a port
1
-
9
of the other hub apparatus
1
-
2
through an LAN cable
1
-
13
. The ports
1
-
17
and
1
-
18
are connected to the other terminal apparatuses
1
-
20
and
1
-
21
.
The terminal apparatuses
1
-
4
and
1
-
5
are connected to ports
1
-
10
and
1
-
11
of the hub apparatus
1
-
2
through cables and network connecting circuits in a manner similar to the connecting form between the terminal apparatus
1
-
3
and the hub apparatus
1
-
1
. Thus, network expansion of a star type connection constructing system is realized.
As for the ports of the hub apparatus
1
-
1
, there is also a port connected through a cable
1
-
15
to a backbone network
1
-
16
for connecting a plurality of LANs as shown by a port
1
-
14
. The backbone network
1
-
16
can be replaced with another network such as a WAN (Wide Area Network) represented by an ISDN network or the Internet.
In the network construction of the conventional LAN system
10
as mentioned above, to expand the network and the connecting terminals, it is necessary to use hub apparatuses such as the apparatuses
1
-
1
and
1
-
2
.
This is because in the LAN system
10
, an apparatus which is connected to one port of the hub apparatus is limited to one terminal apparatus or one hub apparatus.
How a packet (namely, LAN packet data) is transmitted and processed between the terminal apparatuses will now described in the following.
The packet which is transmitted from the terminal apparatus usually includes an address, namely a transmission destination MAC (Media Access Control) address that is peculiar to the apparatus and used to identify a terminal apparatus on the transmission destination side and an address, namely transmitting source MAC address that is peculiar to the apparatus and used to identify the terminal apparatus on the transmitting source side.
When the terminal apparatus on the transmission destination side recognizes that the transmitted packet includes data referring to a value of an transmission destination MAC address, the transmission destination terminal apparatus receives the packet, so that a data transfer is executed between the terminal apparatuses.
As a hub apparatus for transmitting and processing the packet, there are mainly two kinds of apparatuses such as a non-switching hub apparatus and a switching hub apparatus.
The non-switching hub apparatus receives a packet transmitted from a terminal apparatus at one port of a plurality of ports and transmits the received packet to all of the ports other than the port (reception port) which supplied with the received packet, without referring to the MAC address included in the received packet.
To efficiently process a traffic of a network, in the switching hub apparatus, the correspondence relation between the MAC address of each terminal apparatus connected to the hub apparatus and each port is previously held in a buffer area called an address table.
A port on the transfer destination side is determined by referring to the transmission destination MAC address included in the packet transmitted from the transmitting source terminal apparatus and comparing it with the address table and the packet is transmitted only to the decided port (hereinafter, this process is called a switching process).
The data transmission to the ports other than the port concerned with the packet transmission can be prevented by the switching process.
A case where the hub apparatus
1
-
1
shown in
FIG. 1
is a switching hub apparatus will now be considered. Even if the hub apparatus
1
-
1
is the switching hub apparatus, the hub apparatus
1
-
2
is not necessarily a switching hub apparatus.
For example, when the transmission destination MAC address in the packet transmitted from the terminal apparatus
1
-
3
is equal to the MAC address of the transmitting source terminal apparatus
1
-
3
, the port (transmission port) to transmit the packet is equal to the reception port. Thus, the packet is abandoned in the switching hub apparatus
1
-
1
.
There is a case where the packet data is transmitted from the terminal apparatus
1
-
4
connected to the port
1
-
10
of the hub apparatus
1
-
2
to the terminal apparatus
1
-
5
connected to the other port
1
-
11
of the hub apparatus
1
-
2
. In the case, the transmission destination MAC address in the packet data is equal to the MAC address of the terminal apparatus
1
-
5
.
Further, when the hub apparatus
1
-
2
is assumed to be a switching hub apparatus, the hub apparatus
1
-
2
transmits the packet only to the port
1
-
11
to which the terminal apparatus
1
-
5
is connected by the switching hub (switching process) function and does not transmit the packet to the port
1
-
9
connected to the hub apparatus
1
-
1
.
In the case, when the hub apparatus
1
-
2
is a non-switching hub apparatus, the hub apparatus
1
-
2
transmits the packet to all of the ports other than the reception port by the hub function, so that the packet is also transmitted to the port
1
-
9
.
The port
1
-
8
of the hub apparatus
1
-
1
is connected to the port
1
-
9
as mentioned above. In the hub apparatus
1
-
1
which received the packet by the port
1
-
8
, it is recognized that the terminal apparatuses
1
-
4
and
1
-
5
are connected to the same port
1
-
8
, and the transmission port is equal to the reception port, so that the packet is abandoned in the hub apparatus
1
-
1
.
Now, assuming that the hub apparatus
1
-
1
has a function to turn back the received packet to the reception port (turnback transfer function), the hub apparatus
1
-
1
transmits the packet to the port
1
-
8
.
The terminal apparatus
1
-
5
, therefore, receives the packet which is transmitted via the hub apparatus
1
-
1
and the packet that is directly transmitted from the hub apparatus
1
-
2
.
That is, the packet of the same contents is received twice and an overlap of the reception packet occurs.
It will be obviously understood that traffic of the hub apparatus
1
-
1
and the network which is concerned with the hub apparatus
1
-
1
increases.
The conventional switching hub apparatus, therefore, does not have the turnback transfer function to turn back the received packet to the reception port, and when it is recognized that the terminal apparatus having the transmitting source MAC address and the terminal apparatus having the transmission destination MAC address in the received packet are connected to the same port, the packet is abandoned in the switching hub apparatus.
FIG. 2
shows an LAN system
20
having a connecting construction such that by cascade connecting a plurality of terminal apparatuses to one port of a hub apparatus, the network and the number of connecting terminals can be expanded without adding new hub apparatuses as mentioned above.
The LAN system
20
is disclosed in JP-A-10-190714.
In
FIG. 2
, in a hub

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