Virtual local area networks having rules of precedence

Details Virtual local area networks having rules of precedence Virtual local area networks having rules of precedence

1998-12-23

2003-02-25

Vincent, David (Department: 2661)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S395530

Reexamination Certificate

active

06526052

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to communications networks and more particularly to communications systems having various types of virtual local area networks and established rules of precedence for matching a communication packet with a particular virtual local area network.
2. Discussion of the Related Art
Local area networks (LANs) are used to facilitate communications between a number of users. Individual LANs may be bridged together to allow a larger number of users to communicate amongst themselves. These bridged LANs may be further interconnected with other bridged LANs using routers to form even larger communications networks.
FIG. 1
depicts an exemplary interconnected bridged LAN system. The numerals
10
,
20
,
30
, etc., are used to identify individual LANs Bridges between LANs are designated by the numerals
5
,
15
,
25
and
35
. A router between bridged LAN
100
and bridged LAN
200
is identified with the reference numeral
300
. In the bridged LAN system depicted, a user A is able to communicate with a user B without leaving the LAN
10
. If user A desires to communicate with user C in LAN
20
or user D in LAN
30
, the communication is transmitted via bridges
5
and
15
.
If user A desires to communicate with user E, the communication must be routed via router
300
to bridged LAN
200
. As will be understood by those skilled in the art, bridges operate at layer
2
of the OSI network model and transparently bridge two LANs. It is transparent to users A and C that communications between them are ported over bridge
5
because layer
2
bridges do not modify packets, except as necessary to comply with the type of destination LAN. However, if user A wishes to communicate with user E, the communication must be ported via router
300
which operates at level
3
of the network model. Accordingly, communications over routers flow at a much slower rate than communications over a bridge, and, therefore communications are regulated by the routers.
Therefore, LAN network administrators generally attempt to connect together those users who frequently communicate with each other in bridged LANs. However, if the bridged LAN becomes too large, it becomes unscalable and may experience various well-known problems. Accordingly, routers are used to interconnect bridged LANs so that the bridged LANs themselves can be kept to an acceptable size. This results in delays in communications between users which are transmitted via the router
300
. If, for example, in
FIG. 1
, user E and user A need to communicate frequently, it would be advantageous to interconnect LAN
10
and LAN
50
via a bridge rather than the router
300
. This would require the rewiring of the system which is costly and may be impracticable under many circumstances, such as, if users A and E will only need to frequently communicate for a limited period of time.
Virtual LANs (VLANS) have recently been developed to address the deficiencies in interconnected bridged LAN systems of the type depicted in FIG.
1
. VLANs allow LANs to be bridged in virtually any desired manner, i.e., independent of physical topology, with switches operating at layer
2
. Hence, the switches are transparent to the user. Furthermore, the bridging of LANs can be changed as desired without the need to rewire the network. Because members of one VLAN cannot transmit to the members of another VLAN, a firewall is effectively established to provide security which would not be obtainable in a hardwired interconnected bridged LAN system. Accordingly, VLAN systems provide many advantages over interconnected bridged LANs.
For example, as shown in
FIG. 2
, individual LANs
10
,
20
,
30
,
40
,
50
,
60
,
70
,
80
,
90
(
10
-
90
) are interconnected by layer
2
switches
5
′,
15
′,
25
′,
35
′,
45
′, (
5
′-
55
′). A network management station (NMS)
290
controls the interconnection of the individual LANs such that LANs can be easily bridged to other LANs on a long term or short term basis without the need to rewire the network. As depicted in
FIG. 2
, the NMS
290
has configured two VLANs by instructing, e.g., programming, and thereby configuring the switches
5
′-
55
′ such that LANs
10
-
60
are bridged together by switches
5
′,
15
′,
55
′,
35
′ to form VLAN
100
′ and LANs
70
-
90
are bridged together by switches
45
′ and
55
′ to form VLAN
200
′. This is possible because, unlike the bridges
5
-
35
of
FIG. 1
, which include only two ports, and accordingly are able to only transfer information from one LAN to another LAN, the switches
5
′-
55
′ are multi-ported and programmable by the NMS
290
such that the network can be configured and reconfigured in any desired manner by simply changing the switch instructions.
As shown in
FIG. 2
, the switch
55
′ has been instructed to transmit communications from user A of LAN
10
to user E of LAN
50
, since both users are configured within VLAN
100
′. User A, however, is not allowed to communicate with users H or F since these users are not configured within the VLAN
100
′ user group. This does not, however, prohibit users F and H, both of whom are members of VLAN
200
′, from communicating with one another via switches
45
′ and
55
′.
If it becomes desirable to change the network configuration, this is easily accomplished by issuing commands from NMS
290
to the applicable switches
5
′-
55
′. For example, if desired, user H could be easily added to VLAN
100
′ by simply reconfiguring VLAN
100
′ from the NMS
290
. The NMS
290
issues an instruction to switch
55
′, instructing switch
55
′ to allow communications to flow between users A-D and E and user H via switch
55
′, i.e., to include LAN
90
in VLAN
100
′ and remove it from VLAN
200
′.
Because the switches
5
′-
55
′ are layer
2
switches, a bridge formed by the switch is transparent to the users within the VLAN. Hence, the transmission delays normally associated with routers, such as the router
300
of
FIG. 1
, are avoided. The flexibility of the VLAN lies in its' ability to have its' network configuration controlled through software on the NMS
290
. More particularly, in accordance with its' programmed instructions, the NMS
290
generates and transmits signals to instruct the switches
5
′-
55
′ to form the desired VLAN configurations.
In a conventional LAN protocol, a communication packet
400
, as shown in
FIG. 3
, includes a destination address
118
having six bytes, a source address
116
, and message data
112
. The packet
400
also includes an indication of the applicable LAN protocol identifier
114
.
FIG. 5
is a schematic of a conventional VLAN system. The VLAN system includes LANs
205
-
260
which are connected by switches
270
-
280
to a high-speed LAN backbone or trunk
265
. An NMS
290
is interconnected to the switches
270
-
280
via LAN
260
. The NMS
290
is interconnected via LAN
260
as an example and could be interconnected to switches
270
-
280
via any of the LANs
205
-
260
. A trunk station
285
is connected to the high-speed LAN backbone
265
via a trunk port
315
. The LANs
205
-
215
, and
230
-
235
have designated members F-J. LANs connect to each of the switches
270
-
280
by a plurality of access ports
305
. For example, switch
270
is connected via access ports
305
to LANs
205
-
220
.
Each switch is capable of interconnecting a LAN connected via an access port
305
with another LAN connected via an access port
305
. For example, switch
270
can be instructed by the NMS
290
to interconnect LAN
205
to LAN
215
by configuring a VLAN including LANs
205
and
215
, thereby enabling communications between members F and H.
Each switch is also capable of interconnecting a LAN connected by an access port
305
with a LAN connected to another swi

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