Multiplex communications – Fault recovery – Bypass an inoperative station
Reexamination Certificate
2001-03-27
2004-12-07
Pham, Chi (Department: 2663)
Multiplex communications
Fault recovery
Bypass an inoperative station
C370S403000
Reexamination Certificate
active
06829215
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed toward the field of data communication networks. In particular, the invention is directed to a system and method for providing protected communication paths between a LAN and a carrier network.
2. Description of the Related Art
FIG. 1
sets forth a schematic drawing of a communication system
2
that provides a user or a user's local area network
3
(“LAN”) with access to the internet or some other wide area network (“WAN”). In the embodiment shown, a LAN
3
is provided with internet access through a fiber optic system
4
. The fiber optic system
4
provides a connection between the user LAN
3
and an internet access device such as an internet backbone router
5
(“BR”). The BR
5
has a number of ports (not shown) with internet protocol (“IP”) addresses assigned thereto. Internet access is achieved through accessing the ports on the BR
5
.
The preferred user LAN
3
is an Ethernet LAN but other LAN types such as token ring, FDDI, etc., could be used. LAN Hosts
7
b
preferably are personal computers (“PCs”) but optionally could be servers or other computer or communication equipment. LAN router
7
a
preferably comprises computer or communication hardware that forwards data from or to other computer or communication equipment on the LAN
3
. LAN router
7
a
optionally could be coupled to other subnets (not shown) on the user's premises which interconnect other LAN hosts (not shown).
FIG. 2
sets forth a more detailed view of an exemplary communication system
2
for providing a plurality of user LANs
3
with access to the internet or other WAN via a fiber optic system. The exemplary communication system
2
includes a fiber optic system that preferably is arranged in a ring network
10
and more preferably in a Synchronous Optical Network (“SONET”) or SDH ring. The communication system
2
also includes a plurality of network nodes
12
a
,
12
b
,
12
c
, &
12
d
that are coupled together in the SONET/SDH ring
10
, a plurality of local or user LANs
3
a
,
3
b
&
3
c
that are coupled to the network nodes
12
a
,
12
b
&
12
c
, respectively, preferably via fiber optic cables
15
, and an internet or WAN access device
5
such as an internet backbone router (“BR”) coupled to network node
12
d.
FIG. 3
sets forth a system diagram of a preferred SONET/SDH ring
20
for use in a communication system that practices the present invention. The SONET/SDH ring
20
includes a plurality of network nodes
22
, labeled N
0
-N
3
, coupled in a ring structure by one or more communication paths
24
A,
24
B. As shown in
FIG. 3
, the two paths
24
A,
24
B transport SONET/SDH data streams (many packets/cells) in opposite directions about the ring (i.e., east and west). The communication paths
24
A,
24
B are preferably fiber optic connections (in SONET/SDH), but could, alternatively be electrical paths or even wireless connections (in other types of ring networks). In the case of a fiber optic connection, paths
24
A,
24
B could be implemented on a single fiber
24
, on dual fibers
24
A,
24
B, or some other combination of connections. Each network node
22
is preferably coupled to two other network nodes
22
in the ring structure
20
. For example, network node N
0
is coupled to network nodes N
1
and N
3
. The coupling between the nodes in
FIG. 3
is two-way, meaning that each node
22
transmits and receives data (packets/cells) to and from each of the two other nodes
22
to which it is connected Each network node
22
includes at least two transmitter/receiver interfaces, one for each connection to another node
22
. The network nodes
22
could be many types of well-known network devices, such as add-drop multiplexers (“ADMs”), switches, routers, cross-connects or other types of devices. The devices
22
shown in
FIG. 3
are preferably ADMs. An ADM is a three terminal device having a local add/drop interface, an upstream network node interface, and a downstream network node interface. These ADMs
22
are coupled to local nodes
26
, and are used to add packets/cells from the local nodes
26
to the SONET/SDH data stream, and conversely to drop packets from the SONET/SDH data stream to the local nodes
26
. A system and method for packet transport in a SONET/SDH ring network and an exemplary ADM is described in more detail in commonly-assigned U.S. patent application Ser. No. 09/378,844 (“the '844 application”), which is incorporated herein by reference. For more information on SONET/SDH formats, line-speeds, and theory of operation, see John Bellamy,
Digital Telephony
, 2d Edition (1991), pp. 403-425.
The network nodes
22
shown in
FIG. 3
may be logically connected by a plurality of virtual paths that coexist on the physical network connection(s)
24
. Virtual paths are also known as logical paths or “pipes.” For example, although there is only one physical connection from node N
0
to node N
1
to node N
2
, there may be numerous virtual paths between these nodes, such as one virtual path from N
0
to N
1
, another from N
0
to N
2
and another from N
1
to N
2
. Each virtual path may include a plurality of virtual channels, wherein each virtual channel transports packets (or cells) formatted according to the SONET/SDH SPE. The use of virtual paths in SONET/SDH ring networks is described in more detail in commonly-assigned U.S. Pat. No. 6,594,232, which also is incorporated herein by reference.
In the exemplary communication system
2
shown in
FIG. 2
, the network nodes
12
a
,
12
b
&
12
c
are access nodes. The network devices that make up access nodes
12
a
,
12
b
&
12
c
each include an access device or access card (“AC”)
14
. Each access card
14
is operable to transfer data packets between a user's equipment on a LAN
3
and other nodes
12
on the ring network
10
. The access cards
14
of the present invention may physically reside within a network device of the SONET/SDH ring
10
or alternatively may be coupled to a network device.
The network node
12
d
of the exemplary communication system
2
is an internet gateway node and the network device that makes up the gateway node
12
d
includes a multiplexor device or concentrator card (“CC”)
16
. The CC
16
functions as a switch that multiplexes data packets transmitted by the access nodes
12
a
,
12
b
&
12
c
onto a single data transmission channel
18
for further routing to the internet access device
5
. The CC
16
also functions as a switch for forwarding data packets received over the data transmission channel
18
from the internet access device
5
to one or more access nodes
12
a
,
12
b
or
12
c.
Router ports have been configured for shared use between multiple virtual circuits and sub-interfaces. The concentrator card
16
facilitates the shared use of a router port and has a two-fold role. The concentrator card
16
merges the data from the various LANs
3
and access cards
14
on the ring network into a single pipe for forwarding to the single router port of the BR
5
to which the concentrator card
16
is coupled. In merging the data, the concentrator card
16
couples the data to different interfaces within the router port. The concentrator card's
16
second task is to take data from the BR
5
, packet by packet, and forwards the data to the various access nodes
12
on the ring network.
Each access card
14
includes at least one protocol engine
30
, as shown in
FIG. 4
, for providing a fiber extended router port
6
to a LAN
3
. The protocol engine
30
provides a permanent address for use by the LAN devices
7
when transmitting data packets to the WAN. The protocol engine
30
reformats data packets from the LAN devices
7
and transmits the reformatted data packets over the ring
10
through the concentrator interface of CC
16
to a sub-interface of BR
5
. The protocol engine
30
also receives data packets from a sub-interface of BR
5
through the concentrator interface and reformats those data packets to the format used on the LAN
3
. Th
George Keith M.
Jones Day
Marconi Intellectual Property (Ringfence) , Inc.
Pham Chi
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