Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-12-09
2001-01-16
Ton, Dang (Department: 2732)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S465000
Reexamination Certificate
active
06175571
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to the field of local area network (LAN) hubs. Specifically, the present invention relates to an distributed memory switching hub that connects heterogeneous LANs.
B. Description of the Related Art
Client/server computing architecture provides for a large number of clients, i.e., desktop computing devices such as PCs, distributed across an enterprise to be connected in a data network in order to share information and resources located at one or more locations within the enterprise. The information and resources are generally located within or maintained by high performance computer systems called servers and may comprise application software, databases, high speed peripherals or large mass storage devices. Client/server computing architecture has traditionally been based on local area network (LAN) technology such as 10 Mb/s Ethernet or, more generally, a 10 Mb/s bus employing the well known carrier sense, multiple access bus with collision detection (CSMA/CD) to transmit data.
Over the past decade, the number of devices, or “end stations” connected to CSMA/CD LANs and the amount of information transferred between such end stations has grown rapidly. The growth has led to congestion affecting the performance of such LANs. Congestion can be overcome to some degree by partitioning a LAN into multiple segments via bridges or routers. While providing access to the entire data network, these devices electrically isolate the separate segments, thereby reducing the congestion and collisions that can occur when multiple end stations attempt to transmit data at the same time onto the same LAN segment. Bridges and routers have additional capabilities which allow them to properly discard frames of data that would otherwise be unnecessarily transmitted across LAN segments to which they are connected, thereby further reducing unnecessary traffic over the interconnected LAN segments. However, the overall transmission speed of the enterprise-wide data network is still limited to the speed of the underlying LAN technology employed. Furthermore, the presence of bridges and routers, while reducing unnecessary traffic, introduce yet another source of congestion due to the processing overhead incurred as frames of data traverse bridges and routers within the internetwork.
The relatively slow transmission speed of a CSMA/CD LAN, the bridge or router processing overhead encountered as information traverses the data network, and the increasing use of imaging, distributed database management, multimedia or other data-intensive software applications all contribute to an increasingly congested data network. CSMA/CD LAN switching is another approach to reducing network congestion between multiple LAN segments. When a client sends information to a server in another LAN segment, the CSMA/CD LAN switch determines the proper segment to which the information is destined and forms a connection between the appropriate segments. While reducing data network congestion, this approach is also limited to the 10 Mb/s transmission speed of a CSMA/CD LAN. Thus, the inability of existing technology to satisfactorily resolve problems encountered due to greater volumes of traffic on the today's data networks has prompted the development and use of higher speed LAN technologies such as 100 Mb/s Fiber Distributed Data Interface (FDDI), Fast Ethernet, also 100 Mb /s, and Asynchronous Transfer Mode (ATM), which allows speeds from 155 Mb/s up to 622 Mb/s.
Relative to CSMA/CD LAN technology, higher speed LAN technologies, for example, FDDI, are expensive to implement at every desktop. Furthermore, migrating every existing end station in a CSMA/CD LAN to a FDDI ring precludes leveraging investments in CSMA/CD LAN technology and equipment such as software, drivers, adapters, hubs and bridges. Additionally, given the present requirements of client/server applications, it is not necessary to provide 100 Mb/s or greater transmission speeds to every end station in the data network. A client, which requires low cost connectivity to the data network, typically communicates with only one server, and needs a quick response to requests sent to the server. On the other hand, a server needs to respond quickly to requests from a potentially large number of clients while at the same time managing information and resources. Thus, servers can benefit greatly from the increased bandwidth achieved by migrating to a high speed LAN environment, such as FDDI, while clients might see only an incremental benefit in their performance. By migrating to a FDDI ring only those end station s, e.g., servers, requiring such transmission speed, a substantial increase in the performance of a data network can be achieved, while at the same time, substantial savings can be realized.
As has been indicated above, FDDI and CSMA/CD LANs are different LAN technologies in at least certain respects. For example, a FDDI ring supports 100 Mb/s transmission speed, while a CSMA/CD bus supports 10 Mb/s transmission speed. Additional differences, such as, but not limited to, the method of accessing and transmitting data on the medium, frame formats, and frame lengths exist. It is not possible for a client operating in a CSMA/CD LAN environment to directly communicate with a server that has been migrated to a FDDI environment. A hub comprising one or more FDDI and CSMA/CD LAN ports may be used so that CSMA/CD LAN-based end stations can communicate with FDDI-based end stations, thereby increasing the performance of the data network without abandoning existing investments in CSMA/CD LAN technology at the desktop.
FIG. 1
provides a diagram of a typical enterprise-wide data network topology including an embodiment of distributed memory switching hub
18
interconnecting FDDI ring
16
to one or more CSMA/CD LAN segments
12
. Although
FIG. 1
includes a FDDI ring, an embodiment of distributed memory switching hub
18
could interconnect one or more CSMA/CD LAN segments
12
to any high speed network, for example, Fast Ethernet or ATM. Multiple CSMA/CD LAN segments
12
may be coupled to a single 10Base-T hub
17
, although
FIG. 1
shows only one CSMA/CD LAN segment
12
coupled to a 10Base-T hub
17
. 10Base-T hub
17
, in turn provides a connection between a CSMA/CD LAN port
11
on distributed memory switching hub
18
and the attached CSMA/CD LAN segments
12
via segment
21
, itself a CSMA/CD LAN. Distributed memory switching hub
18
functions as a CSMA/CD LAN switch, as described above. Additionally, distributed memory switching hub
18
has one FDDI port
19
through which it is coupled by fiber optic cable
20
or UTP wiring to FDDI concentrator
15
. FDDI concentrator
15
can act as a collapsed FDDI ring (“collapsed backbone”) or provide a connection to physical FDDI ring
16
. In alternative embodiments, multiple FDDI ports may be utilized. FDDI concentrator
15
, in turn, provides a connection to a number of servers
14
that are each configured with an appropriate FDDI adapter and software driver. Distributed memory switching hub
18
provides a connection between FDDI concentrator
15
and its associated servers
14
and 10Base-T hubs
17
, their associated CSMA/CD LAN segments
12
and attached clients
10
. Thus, distributed memory switching hub
18
allows both FDDI and CSMA/CD LAN technologies to coexist in an enterprise-wide data network, thereby enhancing the performance of the client/server computing paradigm.
A switching hub is a computer system including software optimized to receive and transmit frames of data between LAN segments. Referring to
FIG. 2
, as an optimized computer system, prior art switching hub
35
is generally comprised of the same components as a general purpose computer system, including a central programmable processor
30
, an internal control and data bus
33
and shared common memory
31
controlled by central programmable processor
30
. Additionally, prior art switching hub
35
has a plurality of low speed media access controllers (MACs)
Haddock Stephen R.
Harwood Michael J.
Scherbarth Darrell R.
Schneider Herb O.
Crosby, Heafey Roach & May
Network Peripherals, Inc.
Shaw, Jr. Philip M.
Ton Dang
LandOfFree
Distributed memory switching hub does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Distributed memory switching hub, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Distributed memory switching hub will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2521296