Multiplex communications – Channel assignment techniques – Polling
Reexamination Certificate
1997-09-22
2003-01-07
Nguyen, Steven (Department: 2665)
Multiplex communications
Channel assignment techniques
Polling
C370S477000
Reexamination Certificate
active
06504849
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of networking, and more specifically, to the automatic configuration of a fiber optic link that couples two communication nodes.
BACKGROUND
Computer networks enable different systems to communicate with one another. Desirable figures of merit for computer networks include: 1) high bandwidth, 2) low costs associated with bringing up and maintaining a network and 3) backward compatibility of new equipment that is added to an existing network. Existing computer networks are constantly evolving. As the performance of systems that attach to and communicate over a computer network increase, there must be a corresponding improvement in the performance (e.g., bandwidth) of the network. Networks must not only improve in their performance, but also must improve in their ease of management. As network configurations become more complex, network administrators continue to require less and less time spent for each addition, removal, replacement and/or upgrade of their networking hardware or software. Furthermore, new hardware or software must be able to co-exist with the existing hardware and software. This maximizes the return on investment in the older equipment and software. As a result, network administrators place high demand on those new products that increase network performance and ease system management without making their existing hardware and software obsolete. Auto-Negotiation is a network function that enhances network bandwidth, reduces network maintenance costs and accounts for the desire of backward compatible equipment.
Auto-Negotiation is an additional layer within the physical layer of a network communication node. Auto-Negotiation for twisted-pair (copper wire) based Ethernet (“BASE-T”) has been defined in a standard promulgated by the Institute of Electrical and Electronic Engineers (IEEE), entitled “Physical Layer Link Signaling for 10 Mb/s & 100 Mb/s Auto-Negotiation on Twisted-Pair” and referred to as IEEE Standard 802.3u, cl. 28. Briefly, Auto-Negotiation allows a network administrator to add a communication node to a network without having to configure the communication node as to the speed or complexity of the link that connects the node to the network. That is, the communication node itself has the intelligence to optimize itself to the network. Thus, the optimization process, referred to as “negotiation”, is automatic. BASE-T Auto-Negotiation was developed to work within a star (as opposed to ring) topology.
Refer to
FIG. 1
a
. Bus architectures such as BASE-T (as well as ring architectures), were originally designed and developed as shared media networks. That is, for a bus architecture
100
all communication nodes
101
were attached to the same transmission media (e.g., a copper wire bus)
102
, or at least were electrically shorted to one another.
As network configurations evolved, the shared medium
102
was replaced by repeaters or hubs
103
shown in
FIG. 1
b
. Within each repeater/hub
103
is a virtual shared media bus
108
. Thus a “bus” medium may be either actually shared or virtually shared. Virtual shared media bus
108
is not an actual shared media. That is, there are various transceivers
109
on each port
107
a
-
107
d
such that the links
104
a
-
104
d
are no longer short circuited to one another.
Hubs are designed to intelligently manipulate and analyze packets that are received from and transmitted to systems
101
a
-
101
d
on each link
104
a
-
104
d
, while repeaters
103
simply resend the digital data received on one port
107
a
-
107
d
to all other ports
107
a
-
107
d
. The ensuing discussion refers to systems
101
a
-
101
d
and hubs or repeaters
103
. It must be understood that both systems
101
a
-
101
d
and hubs/repeaters
103
are communication nodes. A communication node is any machine or device attached to a link. Usually there are two communication nodes per link. A link is usually a copper-based cable or a fiber optic cable.
Most local area networks (LANs) are currently implemented such that each system link
104
a
-
104
d
is wired to a patch panel
105
within a wiring closet
106
. The repeater or intelligent hub
103
is mounted within the wiring closet
106
and its ports
107
a
-
107
d
are wired to the patch panel
105
such that each repeater/hub port
107
a
-
107
d
has a direct link
104
a
-
104
d
to each system
101
a
-
101
d
. Over time, systems
101
a
-
101
d
and repeaters/hubs
103
may be replaced by higher performance units (in order to meet the networking requirements of the improved systems). For the most part, system
101
a
-
101
d
and repeater/hub
103
upgrades have been possible without replacing the installed cables
104
a
-
104
d
. Thus the layout of
FIG. 1
b
has allowed for relatively easy equipment upgrades while presenting the investment made in the installed cables.
In this sense, the emergence of repeaters/intelligent hubs
103
has resulted in the evolution of LANS away from their original actual shared media design point. Auto-Negotiation was originally designed to ease the effort associated with bringing up systems attached to a hub-based LAN. That is, Auto-Negotiation appeared sometime during or after the evolution away from actual shared media LANs. Auto-Negotiation allows a system, e.g., system
101
a
, and its specific hub port, e.g., port
107
a
, to automatically configure themselves according to their highest performing mode of operation.
As an example, when the network shown in
FIG. 1
b
is brought up or when an older system is replaced by system
101
a
, system
101
a
will advertise its various modes of operation to the hub
103
. The hub
103
will detect this advertisement, through port
107
a
, and respond with its own advertisement of possible modes of operation at port
107
a
. Together, the two systems can understand their common mode(s) of operation (as to copper wire link
104
a
), reject their uncommon modes and, if there is more than one common mode, resolve to a single mode of operation based upon a priority resolution function found within both the system
101
a
and the hub
103
. The priority resolution function is designed to configure the system
101
a
and the hub
103
at port
107
a
such that they operate at their highest performing common mode on the copper wire link
104
a.
The process of advertisement, acknowledgment, response, etc. is generally referred to as negotiation. Such negotiation takes place between every system
101
a
-
101
d
on the network that has Auto-Negotiation capability and its associated hub port
107
a
-
107
d
. As a result, the mode of operation between each system is maximized to the highest performing common mode along each of copper wire links
104
a
-
104
d
. Thus, if a first system
101
a
has a highest common mode, A, with its associated hub port
107
a
, the hub
103
and systems
101
a
will communicate with each other under mode A. If a different system
101
b
has another highest common mode, B, with its associated hub port
107
b
, system
101
b
will communicate with hub
103
, along copper wire link
104
b
, under mode B.
A “mode” of operation is generally representative of the performance of the interconnection between two communication nodes. Under IEEE std. 802.3u, cl. 28, the modes of operation are prioritized according to the maximum data rate of each link. Within identical data rates, modes are prioritized according to the number of lines utilized (i.e., the link's capacity). Thus, 100BASE-TX Full-Duplex is prioritized over 100BASE-TX Half-Duplex; 100BASE-TX Half-Duplex is prioritized over 10BASE-T Full-Duplex; and 10BASE-T Full-Duplex is prioritized over 10BASE-T Half-Duplex (see Annex 28B.3in IEEE std. 802.3u cl. 28). Under the BASE-T technologies, “100” and “10” correspond to 100 MB/s and 10 MB/s data rates, respectively. Different modes exist for a number of reasons. These include: 1) more advanced physical layer technologies continue to evolve (e.g., 10 MB/s to 100 MB/s) and 2) different markets exist for each unique mode. By al
Hsu Chuan-Ding Arthur
Sukavanam Venkataraman
Wang Yun-Che
Cypress Semiconductor Corporation
Nguyen Phuongchau Ba
Nguyen Steven
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