U.S. patent application number 09/745198 was filed with the patent office on 2001-05-03 for method and apparatus for achieving fast reconnection of permanent virtual channels in a frame relay network.
Invention is credited to Eslambolchi, Hossein, Lockhart, Clayton M..
Application Number | 20010000700 09/745198 |
Document ID | / |
Family ID | 22319571 |
Filed Date | 2001-05-03 |
United States Patent
Application |
20010000700 |
Kind Code |
A1 |
Eslambolchi, Hossein ; et
al. |
May 3, 2001 |
Method and apparatus for achieving fast reconnection of permanent
virtual channels in a frame relay network
Abstract
Rapid reestablishment of permanent virtual circuits (PVCs
15.sub.1-15.sub.6) between frame relay switches 12.sub.1-12.sub.4
in a frame relay (10) is accomplished by periodically polling the
switches by a configuration controller (18) via an out-of-band
connection to obtain PVC information from the switches. Should a
fault occur, the fault is isolated and mitigated. Thereafter, the
configuration controller (18) downloads the stored PVC information
to the switches in parallel via the out-of-band connection to
enable the switches to re-establish the PVCs quickly, rather than
wait to do so via an in-band connection.
Inventors: |
Eslambolchi, Hossein;
(Basking Ridge, NJ) ; Lockhart, Clayton M.; (Red
Bank, NJ) |
Correspondence
Address: |
Samuel H. Dworetsky
AT&T Corp.
P.O. Box 4110
Middletown
NJ
07748-4110
US
|
Family ID: |
22319571 |
Appl. No.: |
09/745198 |
Filed: |
December 21, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09745198 |
Dec 21, 2000 |
|
|
|
09107984 |
Jun 30, 1998 |
|
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Current U.S.
Class: |
370/217 ;
370/409; 370/410 |
Current CPC
Class: |
H04L 69/40 20130101;
H04L 12/2854 20130101 |
Class at
Publication: |
370/217 ;
370/409; 370/410 |
International
Class: |
H04L 012/56; H04L
012/28 |
Claims
What is claimed is:
1. A method for restoring Permanent Virtual Circuits (PVCs) linking
frame relay switches in a frame relay network following isolation
and mitigation of a fault, comprising the steps of: prior to
occurrence of the fault, periodically polling each of the frame
relay switches via an out-of-band connection with respect to the
PVCs by a main configuration controller to collect information from
each switch regarding its PVCs; storing at the main configuration
controller the PVC information for each switch obtained from each
polling operation to overwrite the stored PVC information obtained
from a previous polling operation; and following isolation and
mitigation of a fault, downloading the stored polling information
from the main configuration controller to each corresponding frame
relay switch via the out-of-band connection to cause each switch to
reconnect the PVCs in accordance with the downloaded PVC
information.
2. The method according to claim 1 further including the steps of:
storing at each switch prior to the occurrence of a fault, an image
table indicative of the PVCs originating at said switch; following
receipt of the downloaded PVC information received at said switch,
comparing the PVCs indicated by said downloaded information to the
PVCs indicated by said image table; and effecting a change in any
PVC specified in said image table that differs from said downloaded
PVC information.
3. The method according to claim 1 wherein the frame relay switches
are downloaded in parallel.
4. The method according to claim 1 wherein the polling step
includes the step of communicating information between each frame
relay switch and the configuration controller via a dedicated
Internet Protocol network that is out-of-band with respect to PVCs
of the frame relay network.
5. The method according to claim 1 wherein the polling step
includes the step of communicating information between each frame
relay switch and the configuration controller via a link of a
Public Switched Telephone network that is out-of-band with respect
to PVCs of the frame relay network.
6. The method according to claim 1 including the steps of storing,
at a back-up configuration controller the PVC information obtained
by polling each switch; and downloading from the back-up
configuration controller to each switch the stored PVC information
in the event of a failure of the main configuration controller.
7. A frame relay network comprising: a plurality of frame switches
linked to each other via Permanent Virtual Circuits (PVCs); a main
administrative port coupled to the frame relay switches; a main
configuration controller for (a) periodically polling each of the
frame relay switches to collect information from each switch
regarding its PVCs, (b) storing the PVC information for each switch
obtained from each polling operation to overwrite stored PVC
information obtained from a previous polling operation; and (c)
downloading the stored polling information to each corresponding
frame relay switch following isolation and mitigation of a fault to
cause each switch to reconnect the PVCs in accordance with the
downloaded PVC information; a control network for providing an
out-of band link between the main configuration controller and the
main administrative port with respect to the PVCs linking the frame
relay switches.
8. The network according to claim 7 further including a back-up
configuration controller for receiving from the main configuration
controller the stored polling information and for downloading the
stored polling information to each corresponding frame relay switch
following isolation and mitigation of a fault to cause each switch
to reconnect the PVCs in accordance with the downloaded PVC
information upon a failure of the main configuration
controller.
9. The network according to claim 7 wherein the control network
comprises a dedicated IP network.
10. The network according to claim 7 wherein the control network
comprises a Public Switch Telephone Network having a plurality of
dial up links, each connected to a separate frame relay switch.
11. The network according to claim 7 further including a back-up
administration port for coupling the main configuration controller
to the frame relay switches in the event of a failure of the main
administration port.
Description
TECHNICAL FIELD
1. This invention relates to a technique for re-establishing
permanent virtual circuits in a frame relay network in a rapid and
efficient manner following a service outage.
BACKGROUND ART
2. Presently, several inter-exchange telecommunications carriers,
such as AT&T, offer frame relay service for transporting data
packets from one local area network to another. Among the customers
that utilize frame relay service from AT&T and other
telecommunications carriers are banks and financial institutions
that transport data from automated teller machines and point of
service terminals to data processing facilities to enable debiting
of a purchaser's account for cash withdrawals and debit-card
purchasers. Other customers of frame relay service include
manufacturers that use the service to transmit data among
manufacturing facilities to coordinate scheduling, inventory
levels, and other activities. Large retailers who maintain
geographically separated stores and warehouses also use frame relay
service to exchange data between facilities to assure timely
delivery of merchandise.
3. The heavy reliance of customers on such frame relay service
mandates that the carriers that offer such service provide fast
restoration in the event of a service outage. Unfortunately,
present day techniques for restoring service often take a
significant amount of time, especially for very large networks.
Invariably, in the event of a service outage, all of the Permanent
Virtual Circuits (PVCs) that link frame relay switches become
disabled, and must be re-established after isolation and repair of
the fault. Reconnection of the PVCs requires re-establishment of
logical (control) signaling links among the frame relay switches
first before the frame relay switches can re-establish the PVCs
themselves. During normal operation of a frame relay network,
establishing such logical signaling links takes little time.
However, in the event of a large service outage, a significant
amount of activity often exists in the network, significantly
lengthening the time required to re-establish the PVCs among the
frame relay switches. As a consequence, customers incur delayed
restoration of service, increasing customer dissatisfaction and
reducing revenue to the carrier providing such service.
4. Thus, there is a need for a technique that reduces the time
required to re-establish PVCs in a frame relay network following a
service outage.
BRIEF SUMMARY OF THE INVENTION
5. Briefly, in accordance with a preferred embodiment of the
invention, a method is provided for restoring Permanent Virtual
Circuits (PVCs) that link frame relay switches in a frame relay
network following a fault. Prior to the fault, a main configuration
controller periodically polls each of the switches in the frame
relay network to obtain information about the PVCs linking the
switches. Such polling is done out-of band from the frame relay
network, either via a dedicated IP control network, or via dial-up
links of a Public Switched Telephone Network. The main
configuration controller stores the information obtained during
each polling by over-writing the information obtained during the
previous polling. Following isolation and mitigation of a fault in
the frame relay network, the main configuration downloads to each
switch, via the out-of-band network, the stored PVC information to
enable the frame relay switches to the switches to re-establish the
PVCs quickly.
BRIEF DESCRIPTION OF THE DRAWING
6. FIG. 1 shows a block schematic diagram of a frame relay network
in accordance with a preferred embodiment of the invention.
DETAILED DESCRIPTION
7. FIG. 1 illustrates a frame relay network 10 in accordance with a
preferred embodiment of the invention. The network 10 includes a
plurality of frame relay (FR) switches, such as the switches
12.sub.1-12.sub.4. While the network 10 of the preferred embodiment
includes the four switches, the network 10 could include a larger
or smaller number of switches as required. The switches
12.sub.1-12.sub.4 each receive packet data from a corresponding one
eof routers 13.sub.1-13.sub.4 that each serve one or more data
source/destinations 14--14. The frame relay switches
12.sub.1-12.sub.4 are linked to each other via permanent virtual
circuits (PVCs) 15.sub.1-15.sub.6 in the manner shown in FIG. 1.
The PVCs circuits 15.sub.1-15.sub.6 are akin to leased or private
lines in a conventional Public Switched telephone network in that
the PVCs do not require reestablishment for every subsequent
transmission of data between a pair of frame relay switches. During
normal operation, the frame relay switches 12.sub.1-12.sub.4 each
store information regarding the PVCs 15.sub.1-15.sub.6, especially
those originating at that switch within an image table (not shown).
The image table information enables to switch to know what PVC's
exist for that switch, thus enabling the switch to send data
without first having to establish a PVC for transmission.
8. In the event of a network outage, one or more of the PVCs may
become inoperative. Indeed, a large service outage may affect all
or a majority the PVCs 15.sub.1-15.sub.6. At the present time,
reestablishment of the PVCs 15.sub.1-15.sub.6 may consume
significant time, especially following a large service outage. To
re-establish the PVCs 15.sub.1-15.sub.5, the frame relay switches
12.sub.1-12.sub.4 must first reestablish signaling links
16.sub.1-16.sub.6, (shown by dashed lines), whereupon the frame
relay switches thereafter proceed to set up the PVCs
15.sub.1-15.sub.6 While the time required to set up the PVCs
15.sub.1-15.sub.6 during normal operation is generally minor, after
a major service outage, an extraordinary amount of activity
typically exists on the frame relay network, significantly
lengthening the time required to reestablish the PVCs.
9. In accordance with the invention, the time required to set up
the PVCs' 15.sub.1-15.sub.6 can be reduced by communicating PVC
information to the frame relay switches 12.sub.1-12.sub.4 out of
band, i.e., via a channel that is separate and distinct than the
PVCs 15.sub.1-15.sub.6 and the control channels 16.sub.1-16.sub.6.
To accomplish such out-of-band communication of PVC information,
the network 10 of the invention includes a main configuration
controller 18, and preferably, a back-up configuration controller
20. A control network 22 that is out-of-band with respect to the
PVCs 15.sub.1-15.sub.6 and the signaling links 16.sub.1-16.sub.6
couples the main and back-up configuration controllers 18 and 20,
respectively, to a main administration port 24, and preferably, a
back-up administration port 26 as well. The control network 22 may
comprise a dedicated data network, such as a network that uses an
IP protocol. Alternatively, the network 22 could comprise a Public
Switched Telephone Network (PSTN), such as the PSTN maintained by
AT&T. When the network 22 comprises a PSTN, the connections
between the PSTN and the main and back-up configuration controllers
18 and 20, respectively, and the main and back-up administrative
ports 24 and 26, respectively, may comprise dedicated lines or
dial-up links. The main administrative port 24 has connections
28.sub.1-28.sub.4 to the frame relay switches 12.sub.1-12.sub.4,
respectively, whereas each of the connections 30.sub.1-30.sub.4
links a corresponding one of the frame relay switches to the
back-up administrative port 26. Each of the connections
28.sub.1-28.sub.4 and 30.sub.1-30.sub.4 typically has a T3
bandwidth and serves to communicate PVC information between each
switch and a corresponding one of the main and back-up
administration ports 224 and 26.
10. In operation, the main controller 18 periodically polls each of
the frame relay switches 12.sub.1-12.sub.4 via the main
administrative port 24 (or in the event of its failure, via the
back-up administrative port 26) to obtain information regarding the
cross connects, that is the PVCs 15.sub.1-15.sub.6, that exist
between switches. Depending on the size of the frame relay network,
and the frequency at which PVC changes occur, the main
configuration controller 18 may poll the switches as often as every
hour, or as infrequently as once each day. The main configuration
controller 18 obtains the PVC information from the frame relay
switches 12.sub.1-12.sub.4 out-of-band, that is separate from the
PVCs 15.sub.1-15.sub.6 and the control links 16.sub.1-16.sub.6, by
making use of the out-of-band control network 22. The main
configuration controller 18 stores the PVC information obtained
during each subsequent polling by overwriting the information
obtained during the last previous polling. As the main
configuration controller 18 stores the most recently obtained
polling information, main configuration controller provides the
information to the back-up configuration controller 20 via the
network 22. In this way, the PVC information stored at the back-up
configuration controller 20 mirrors the PVC information stored at
the main configuration controller 18.
11. Should the frame relay network 10 suffer a fault, those
responsible for maintaining the network will to isolate and
mitigate the fault. After fault isolation and mitigation, the main
configuration controller 18 (or in the event of its failure, the
back-up configuration controller 20) downloads to each of the frame
relay switches 12.sub.1-12.sub.4 the PVC information for that
switch based on the last polling. In practice, the main
configuration controller 18 downloads the PVC information to the
frame relay switches 12.sub.1-12.sub.4 in parallel, thus enabling
the switches to receive the information quickly, and thereafter
commence restoration of the PVCs, rather than wait to communicate
the information among themselves in-band, as occurred in the prior
art. The receipt of the PVC information from the main configuration
controller 18 (or in the event of its failure, from the back-up
configuration controller 20) out-of-band thus enables the frame
relay switches to re-establish the PVCs 15.sub.1-15.sub.6 more
quickly, reducing the interval of customer outage, and the
accompanying customer dissatisfaction.
12. In practice, the PVC information downloaded from the main
configuration controller 18 may not reflect the latest
cross-connection information at the frame relay switch, especially
if new cross-connects have been added since the last polling. We
assume the frame relay switches 12.sub.1-12.sub.4 have the
capability of comparing the downloaded PVC information from the
main configuration controller 18 to the PVC information stored by
the switch in its image table. Assuming that the switches also have
the ability of reconnecting/disconnecting its PVCs, then each
switch can advantageously make the comparison between the
downloaded PVC information, and the PVC information in its image
table, and thereafter make the necessary
re-connections/disconnections in accordance with the
comparison.
13. The foregoing describes a technique for establishing rapid
reconnection of permanent virtual circuits in a frame relay
network.
14. It is to be understood that the above-described embodiments are
merely illustrative of the principles of the invention. Various
modifications and changes may be made thereto by those skilled in
the art which will embody the principles of the invention and fall
within the spirit and scope thereof.
* * * * *