Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-07-29
2002-03-19
Jung, Min (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S463000, C370S465000
Reexamination Certificate
active
06359893
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of local area networks (LANs) using the Ethernet communication protocol (e.g., the IEEE 802.3 Standard). Specifically, the present invention relates to a switchable component within a network repeater hub.
2. Description of Related Art
Communication networks for computer systems are an extremely popular form of providing network computing today.
FIG. 1
illustrates a high level block diagram of the communication levels within a typical communication network system
5
. System
5
has a first communication level
12
including communication adapters (“cards”) that are inserted into computer systems to provide them with networking capability. The computer systems interface with users
10
. The second communication level
14
is the workgroup level and includes hubs (e.g., repeater hubs, switching hubs, etc.). The hubs provide communication pathways between computer systems of the same or multiple local area networks (LANs). Computer systems coupled to a common hub share the same collision domain. A collision domain is a group of computer systems logically connected to share the same physical bandwidth (e.g. 10 Megabits/sec or 100 Megabits/sec) of a communication pathway. In the field of twisted pair cable repeater hubs, a collision domain is managed by a Repeater Interface Controller (RIC). The third level
16
is often called the backbone or backplane level and can include segment switches. Among other functions, the components of level
16
provide communication pathways between hubs and between different collision domains.
Recently, 100 Megabit bandwidth networking (100 M or 100) has been introduced into the marketplace of computer network systems from an installed base of 10 Megabit bandwidth systems (10 M or 10). This has led to the development of dual rate adapter cards (e.g., of level
12
) that can be configured to communicate at 100 M or 10 M; these dual rate adapters are referred to as
10
/
100
adapters. The IEEE 802.3 standard provides for an auto-negotiation session whereby the
10
/
100
adapter can determine which communication rate is supported by its coupled hub (e.g., of level
14
). However, as described in more detail below, many of the workgroup hubs in level
14
do not support 100 M networking because of the additional cost required to upgrade the workgroup equipment to this rate.
For instance, refer to
FIG. 2A
which illustrates a prior art communication system
44
employing two repeater hubs
30
and
32
. Repeater hubs are low cost because they do not require an expensive Media Access Controller (MAC) for each port nor do they require switches; only a physical device (e.g.,
21
a
-
21
d
or
23
a
-
23
d
) is required at each port to provide repeating. Within system
44
, all ports of a repeater hub (the hub having one repeater interface controller, RIC) are required to be of the same communication rate because: (1) messages from one port are repeated to all other ports by the hub's RIC; and (2) because only one RIC is provided, only one collision domain is allowed. Therefore,
10
/
100
adapters
20
a
-
20
d
are coupled to repeater hub
30
operating at 10 M while
10
/
100
adapters
22
a
-
22
d
are coupled to repeater hub
32
operating at 100 M. The adapters
20
a
-
20
d
and
22
a
-
22
d
are coupled to their associated hubs through physical devices
21
a
-
21
d
and
23
a
-
23
d
, respectively. The repeater hubs
30
and
32
are coupled to backbone circuit
40
through pathways
34
and
36
, respectively. Backbone circuit
40
may contain segment switches or routers. Due to the difference in operational speeds of hubs
30
and
32
, the only means by which the two hubs can communicate is through backbone level
40
, which has circuits that can adapt the data from each segment.
FIG. 2B
illustrates a similar prior art communication system
78
using three exemplary stackable low cost repeater hubs
50
a
,
50
b
and
54
that each use a single RIC. Hubs
50
a
and
50
b
operate at 10 M while hub
54
operates at 100 M. Hubs
50
a
and
50
b
are coupled to switch module
62
via separate pathways
52
a
and
52
b
, respectively, while hub
54
is coupled to switch module
62
via separate pathway
56
. The switch module
62
provides communication between the different collision domain segments. This can be accomplished either using a bus based CPU architecture or a cross bar switch architecture. A management module
64
is also included and interfaces with the switch module
62
.
In systems like system
44
and system
78
(FIGS.
2
A and
2
B), the majority of installed repeater hubs support only 10 M communication (e.g., 10 Base T). If one port of a 10 M repeater hub (e.g., hub
30
or a hub of hubs
50
a
and
50
b
) needs to be upgraded to 100 M, all ports within the 10 M repeater hub need to be upgraded because the hub only supports collision domain. This causes a problem because the cost of performing such an upgrade for all ports in a 10 M repeater hub is very expensive and can be impractical if only one port needs the 100 M communication rate. The prior art solution for providing 100 M communication has been to add repeaters, e.g., repeater hub
54
, that handle only 100 M communication. However, this solution has drawbacks when a computer system moves from one port to another. For instance, if system
44
includes ten 10 M hubs like hub
30
and only one 100 M hub like hub
32
and then adapter
22
a
is moved from one building to another, adapter
22
a
may no longer be physically accessible to hub
32
. The same is true for system
78
. It would be advantageous to provide a low cost repeater hub design that offers the flexibility of readily upgrading one or more ports of the hub to 100 M while allowing the remainder ports to operate at 10 M without requiring expensive switching circuitry. The present invention provides such a repeater hub.
FIG. 3
illustrates a high cost communication network
96
based on a switching hub
90
that provides mixed 10 M and 100 M ports. Adapters
80
a
-
80
h
of the
10
/
100
type are coupled via respective physical devices
81
a
-
81
h
to switching hub
90
. Switching hub
90
contains complex circuitry
92
to provide multiple independent communication channels between respective pairs of adapters
80
a
-
80
h
. Switching hub
90
allows for mixed 10 M and 100 M ports because independent communication channels can be formed between adapter pairs. However, system
96
is a very expensive network solution due to the required switching logic. For instance, the cost per port of the switching hub
90
is well over an order of magnitude greater than the cost per port of repeater system
44
(
FIG. 2A
) or repeater system
78
(FIG.
2
B). For many network applications, the use of switching hub
90
is not a practical solution for providing mixed 10 M and 100 M ports within a workgroup hub because of its high cost per port. It would be advantageous to provide a workgroup hub that offers the flexibility of mixed 10 M and 100 M ports while avoiding the high cost per port associated with switching hubs. The present invention provides such a repeater hub.
Lastly, some repeater hubs incorporate more than one RIC circuit allowing a mixture of both 10 M and 100 M ports within a single
10
/
100
repeater hub. However, these
10
/
100
repeater hubs, as well as the repeater hubs of system
44
and system
78
, use prior art physical devices to recover information at the port connection. As shown in
FIG. 4
, the physical device circuits
100
of the prior art, while supporting either 10 Base T 106 or 100 Base T 108 communication, nevertheless offer only one media independent interface (MII)
104
. Therefore, each port within the prior art
10
/
100
repeater hub (using physical device
100
) is hardwired to communicate within one, and only one, collision domain
102
(e.g., 100 M domain or 10 M domain). While allowing mixed
10
/
100
port assignments, this prior art
10
/
100
repeater hub is not flexible
Conexant Systems Inc.
Jung Min
Lyon & Lyon LLP
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