Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-12-12
2001-03-06
Vu, Huy D. (Department: 2739)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S379000, C370S382000
Reexamination Certificate
active
06198741
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a network interface apparatus called a router or the like which is provided in a network system and relays a transmission of a data packet as a bundle of information.
2. Description of the Related Art
Hitherto, in a network system, a network interface apparatus for relaying a transmission of a data packet which is transmitted and received in the network existed.
FIG. 5
is a diagram showing an example of a network system.
A network system
10
is constructed by: a network interface apparatus
11
having three ports (ports
1
,
2
, and
3
) for inputting and outputting a data packet; LANs (Local Area Networks)
1
,
2
, and
3
connected to the ports
1
,
2
, and
3
; and a number of terminals A to J connected to any one of the ports via any one of the LANs
1
,
2
, and
3
. Among those many terminals, the terminals A to C are connected to the port
1
, the terminals D to G are connected to the port
2
, and the terminals H to J are connected to the port
3
, respectively.
In case of transmitting a data packet from the terminal A to the terminal D, the data packet transmitted from the terminal A serving as a transmitting source is inputted from the port
1
to the network interface apparatus
11
via the LAN
1
. The network interface apparatus
11
knows that the terminal D serving as a receiving destination is the terminal connected to the port
2
from a receiving destination address in the data packet, and generates the data packet from the port
2
to the LAN
2
.
The terminal D knows that the data packet is a data packet to be received by itself from the receiving destination address in the data packet sent via the LAN
2
, and receives the data packet. The data packet is transmitted and received in this manner.
Because of a problem on safety of data communication and blocking a broadcast packet, in recent years, an idea of VLAN (Virtual LAN) has been used. The VLAN is a logical LAN defined as a group capable of communicating at a position away from the physical LANs
1
,
2
, and
3
connected to the ports
1
,
2
, and
3
. For example, in a configuration shown in
FIG. 5
, it is assumed that the terminals A, B, D, E, and F surrounded by a broken line construct one VLAN labeled as VLAN
1
, the terminals D, E, H, I, and J surrounded by an alternate long and short dash line construct one VLAN labeled as VLAN
2
, and the terminals C, E, F, G, and J surrounded by a dotted line construct one VLAN labeled as VLAN
3
, respectively. As shown in this example, it is also permitted that one terminal belongs to a plurality of VLANs.
FIG. 6
is a diagram showing relations among the terminals and the VLANs shown in FIG.
5
.
In the example shown here, the terminals A and B belong to only the VLAN
1
, the terminals H and I belong to only the VLAN
2
, the terminals C and G belong to only the VLAN
3
, the terminal D belongs to the VLAN
1
and VLAN
2
, the terminal J belongs to the VLAN
2
and VLAN
3
, the terminal F belongs to the VLAN
3
and VLAN
1
, and the terminal E belongs to the VLAN
1
, VLAN
2
, and VLAN
3
, respectively.
Corresponding relations among addresses of the terminals, VLAN IDs of the VLANs to which the respective terminals belong, and port IDs of the ports to which the terminals are connected have been recorded in the network interface apparatus
11
. When a data packet is inputted to the network interface apparatus
11
, the network interface apparatus knows whether the terminal of the transmitting source and the terminal of the receiving destination belong to the same VLAN or not by referring to a transmitting source address and a receiving destination address of the data packet. When they belong to the same VLAN, the data packet is transmitted from the port to which the receiving destination terminal is connected.
FIG. 7
is a diagram showing an example of a VLAN control table showing the corresponding relation among the addresses of the terminals, the VLAN IDs of the VLANs to which the terminals belong, and the port IDs of the ports to which the terminals are connected in the network interface apparatus.
In the diagram, the addresses (MAC addresses) of the terminals, the VLAN IDs to identify the VLANs to which the terminals belong, and the port IDs to identify the ports to which the terminals are connected are simply stored as a table.
For example, the terminal (terminal A) of an MAC address A belongs to the VLAN
1
and is connected to the destination of the port
1
. The terminal (terminal D) of an MAC address D belongs to the VLAN
1
and VLAN
2
and is connected to the destination of the port
2
. The terminal (terminal E) of an MAC address E belongs to the VLAN
1
, VLAN
2
, and VLAN
3
and is connected to the destination of the port
2
.
A case where, for instance, the terminal J belonging to the VLAN
2
and VLAN
3
becomes a transmitting source and transmits the data packet to the terminal F belonging to the VLAN
1
and VLAN
3
will now be considered. Since the terminals J and F belong to the common VLAN, namely, VLAN
3
, communication can be performed between the terminals J and F.
In this case, the network interface apparatus
11
first knows that the terminal J belongs to the VLAN
2
from the transmitting source address J in the inputted data packet, knows that the terminal F belongs to the VLAN
1
from the receiving destination address F in the data packet, and compares the VLAN
2
and VLAN
1
. Since they do not coincide here, subsequently, the network interface apparatus
11
knows that the terminal F belongs to the VLAN
3
and compares the VLAN
2
of the terminal J with the VLAN
3
of the terminal F. Since they also do not coincide here, the network interface apparatus
11
knows that the terminal J belongs to the VLAN
3
, knows that the terminal F belongs to the VLAN
1
, and compares the VLAN
3
and VLAN
1
. Since they do not coincide here, the network interface apparatus
11
knows that the terminal F also belongs to the VLAN
3
and compares the VLAN
3
and VLAN
3
. Since they coincide now, the network interface apparatus
11
knows that the inputted data packet can be also transmitted to the terminal F, and sends the data packet to the port
2
to which the terminal F is connected. In this manner, whether the transmitting source terminal and the receiving destination terminal belong to the same VLAN or not is known with reference to the table shown in FIG.
7
. When they belong to the same VLAN, the data packet can be transmitted to the receiving destination terminal. However, it is necessary to successively compare as mentioned above in order to know whether the transmitting source terminal and the receiving destination terminal belong to the same VLAN or not. When each terminal belongs to a number of VLANs, such a method of finding the common VLAN by the successive comparison has problems such that it needs a long time and a communicating speed is reduced.
FIG. 8
is a diagram showing another corresponding method among the addresses (MAC addresses) of the terminals and the VLANs to which the terminals belong.
In this instance, a bit arrangement of a length of the maximum number (n+1) of VLANs is provided every MAC address (each terminal) and each VLAN is allocated to each bit in a manner such that the VLAN
1
is allocated to bit
0
, the VLAN
2
is allocated to bit
1
, and the VLAN
3
is allocated to bit
2
.
For example, a bit arrangement of (n+1) bits corresponding to the MAC address A (terminal A) is shown in FIG.
8
(
a
). The diagram shows that only bit
0
is set to “1” and all of the other bits are set to “0”, so that the terminal A belongs to only the VLAN
1
. Similarly, a bit arrangement of (n+1) bits corresponding to the MAC address D (terminal D) is shown in FIG.
8
(
b
). Since bit
0
and bit
1
are set to “1” and the other bits are set to “0”, it will be understood that the terminal D belongs to the VLAN
1
and VLAN
2
. Further, a bit arrangement of (n+1) bits corresponding to the MAC address E (terminal E) is shown in FIG.
8
(
c
)
Ishida Yoshihiro
Yoneda Masato
Yoshizawa Hiroshi
Kawasaki Steel Corporation
Oliff & Berridge PLC.
Toan Nguyen
Vu Huy D.
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