Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
1999-01-12
2004-04-20
Ton, Dang (Department: 2666)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C370S216000
Reexamination Certificate
active
06724756
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to providing high service availability in networks. More particularly, the present invention relates to using both an active controller and standby controller to ensure continuous communication across a network in the event of network controller failure.
BACKGROUND
Asynchronous transfer mode (“ATM”) networks use a cell-based switching and multiplexing technology to provide a general-purpose connection-oriented transfer mode for a wide range of services. These services include the simultaneous transfer of voice, video, and data between end-users connected to an ATM network. Examples of end-users include, but are not limited to, work stations, network nodes, and routers. Typically, each end-user relies on an ATM user-network interface (“UNI”) and an edge switch to communicate across the ATM network. The edge switches allow the end-user to transmit across the multiple nodes of an ATM network by creating a virtual connection from one end-user to another end-user. Alternatively, edge switches are also used to create virtual connections from one end-user to multiple end-users.
The complexity of ATM networks led to the development of a Private Network-Node Interface (“PNNI”) protocol. The PNNI protocol provides a signaling and routing protocol that relies on a hierarchical addressing scheme to summarize routing information. In particular, the routing protocol uses both a topology scheme and end-user hierarchical scheme to identify the address of all nodes and end-users in an ATM network. Accordingly, through the exchange of topology information over PNNI links, every node in the ATM network receives a hierarchically summarized version of the entire network. Given that a source node has a summarized view of the entire network, the source node uses the PNNI signaling protocol to set up an ATM connection along the path determined by the routing protocol.
FIG. 1
illustrates a prior art ATM network using a PNNI scheme. In particular, network
100
comprises a group of nodes (
120
-
130
) connected by links (
141
-
146
). As illustrated in
FIG. 1
, the combination of nodes and links form PNNI
110
. Network
100
also includes end-users (
115
-
118
). PNNI
110
allows each end-user to transfer data, in the form of cells, to another end-user or a group of end-users. For example, a data transfer from end-user
115
to end-user
117
is performed along link
141
. Alternatively, the same data transfer is performed via link
142
, node
130
, and line
143
. As previously described, in a PNNI protocol the source node has a summarized view of the entire network. Accordingly, following the previous example, node
120
is aware of the different routing paths between end-user
115
and end-user
117
. Thus, based on the network congestion found in PNNI
110
, node
120
selects one of the paths between end-user
115
and end-user
117
and establishes a switched virtual connection (“SVC”).
To establish the SVC, node
120
moves through three different phases. In the initial phase—also referred to as the call establishment phase—node
120
initiates a set up call using the address of the destination device. The setup call is routed through the intermediate nodes of PNNI
110
until the destination device is reached. The destination device responds with a call connect message that is transmitted back to node
120
. When the call connect reaches node
120
, node
120
transfers to a call active phase. In the call active phase, data is transmitted between end-user
115
of node
120
and the destination device. Subsequently, node
120
moves to the third phase—the release phase—and the call between node
120
and the destination device is terminated.
FIG. 2
shows a prior art switching circuit used in a node of an ATM network. In particular, network switch
200
has two planes of operation, a user plane and a control plane. The user plane deals with the actual user traffic managed by switch
210
, call database
209
, interfaces
220
(
a
)-
220
(
n
), and interfaces
221
(
a
)-
221
(
n
). In particular, switch
210
uses call data base
209
to maintain different virtual paths and virtual channel connections between interfaces
220
(
a
)-
220
(
n
) and interfaces
221
(
a
)-
221
(
n
). The control plane is set up by controller
215
and is responsible for setting up a connection between controller
215
and a remote controller via interface
221
or interface
220
. For example, if network switch
200
is used in node
120
of network
100
, One of the interfaces
220
(
a
)-(
n
) is coupled to end-user
115
. Additionally, a subset of interfaces
221
(
a
)-(
n
) are coupled to links
141
and
142
and interface
221
is coupled to both links
141
and
142
. Thus, the control plane of controller
215
is coupled to a controller in node
126
and a controller in node
130
via interface
221
.
One of the functions maintained by the control plane is to ensure a continuous communications link between adjacent nodes in a network. Typically, the continuity of the communication link is maintained by a keep alive protocol in which each controller periodically checks the operation of controllers in adjacent nodes. Specifically, a controller will periodically transmit a query signal to the controller of an adjacent node or adjacent nodes. Each controller in an adjacent node responds to the query signal with a reply signal indicating that the controller is operating normally. In the event that the controller in the adjacent node does not respond to the query signal, the controller originating the query signal tears down (terminates) all active calls with the non responding adjacent node.
As illustrated in
FIG. 2
, network switch
200
includes a controller
215
coupled to switch
210
via line
225
. Controller
215
generally controls the switching characteristics of switch
200
using line
225
. In particular, controller
215
controls switch
200
using a call database (
216
) comprising switch control code, a connection routing protocol (
217
), and call control logic
218
. The call database
216
contains information regarding each of the links connected to network switch
200
via interfaces
220
(
a
)-
220
(
n
) and interfaces
221
(
a
)-
221
(
n
). The call database
216
resides on controller
215
. The call control logic
218
establishes and releases switched virtual connections under the control of the controller
215
.
Controller
215
and switch
210
operate as a single network node. Controller
215
receives and processes connection routing protocol messages and determines which local resources of switch
210
are affected by the protocol messages. Switch
210
, in turn, adds and deletes cross-connects as determined by controller
215
and logs the new switch connections in switch cross-connect database
209
.
In this prior art switch and controller arrangement, a single controller supporting a network software layer is allowed to control the resources of the switch. Numerous disadvantages result from this configuration. One disadvantage results from a controller failure. In particular, a controller failure results in a failure of a node which in turn leads to the interruption of data transfers. Another disadvantage results from call tear-downs. Specifically, a controller failure results in an active call being dropped. The dropped call creates an interruption of service to the end user. Thus, resulting in service unavailability and a subsequent re-establishment of the call using alternate nodes.
SUMMARY OF THE INVENTION
A method for sharing a call record between a first controller and a second controller is disclosed. The method comprises the step of generating the call record in the first controller. For one embodiment, the call record comprises call parameters operable to establish a call connection between the first controller and a remote controller. The method also comprises the step of transferring the call record to the second controller. For one embodiment, the second controller performs as a stand-by controller. Thus, in the
Fourie Henry L.
Lau Chun-Hung
Cisco Technology Inc.
Ton Dang
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