Selective VP protection method in ATM network

Details Selective VP protection method in ATM network Selective VP protection method in ATM network

1998-06-01

2002-08-27

Nguyen, Chau (Department: 2663)

Multiplex communications

Fault recovery

Bypass an inoperative switch or inoperative element of a...

C370S244000, C370S395100

Reexamination Certificate

active

06442131

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a selective VP (Virtual Path) protection method, and in particular, to a selective VP protection method for performing protection of virtual paths in an ATM network comprising; a plurality of ATM cross-connect nodes, selectively employing VP end protection (VP protection executed by VP end nodes) and arbitrary type of VP protection executed by ATM cross-connect nodes other than the VP end nodes, in which an area of the VP-AIS (Alarm Indication Signal) cell transmitted by ATM cross-connect nodes which detected failure is utilized as information for selecting and determining the VP protection method.
DESCRIPTION OF THE PRIOR ART
Various kinds of VP protection methods (i.e. methods for protecting virtual paths established between VP end nodes) in ATM networks composed of a plurality of ATM cross-connect nodes have been proposed.
FIGS. 1 and 2
are schematic diagrams showing a general conventional VP protection method in an ATM network system. The ATM network system shown in
FIGS. 1 and 2
comprises six ATM cross-connect nodes XC
11
~XC
16
and ATM transmission lines connecting the ATM cross-connect nodes XC
11
~XC
16
. In the ATM network system of
FIGS. 1 and 2
, the ATM cross-connect nodes XC
11
and XC
12
, XC
12
and XC
13
, XC
13
and XC
14
, XC
14
and XC
15
, XC
15
and XC
11
, XC
12
and XC
16
, and XC
16
and XC
13
are connected by the ATM transmission lines.
FIG. 1
is conceptually showing a case where a line failure
23
such as disconnection of optical fibers etc. occurred on the transmission line between the ATM cross-connect nodes XC
12
and XC
13
when a virtual path connection XC
11
-XC
12
-XC
13
-XC
14
is established between the ATM cross-connect nodes XC
11
and XC
14
.
The ATM network system composed of the ATM cross-connect nodes XC
11
~XC
16
employs both VP end protection (VP protection executed by VP end nodes) and arbitrary VP protection. Here, the VP end protection means VP protection which is executed by VP end nodes of a virtual path. At present, the VP end protection can be classified into the following types.
I. pre-planned VP end protection
{circle around (1)} dedicated resources VP end protection
(with preset alternative routes and bandwidths)
{circle around (2)} semi-dedicated resources VP end protection
(with preset alternative routes)
II. real time restoration VP end protection
(or on-demand resources VP end protection)
The VP end protection executed by the VP end nodes XC
11
and XC
14
in
FIGS. 1 and 2
includes the above three types of VP end protection. The arbitrary VP protection means arbitrary type of VP protection in its literal sense which is spontaneously executed by adjacent ATM cross-connect nodes other than the VP end nodes. The arbitrary VP protection includes APS (Automatic Protection Switching) which is employed in SDH (Synchronous Digital Hierarchy) and ‘section protection switching’ which will described below, for example.
The VP end protection is executed between the ATM cross-connect nodes (VP end nodes) XC
11
and XC
14
using a route XC
11
-XC
15
-XC
14
as an alternative route of the route XC
11
-XC
12
-XC
13
-XC
14
, and the arbitrary VP protection is executed between the ATM cross-connect nodes XC
12
and XC
13
. In the case where the section protection switching is executed as the arbitrary VP protection between the ATM cross-connect nodes XC
12
and XC
13
, a route XC
12
-XC
16
-XC
13
is used as an alternative route of the route XC
12
-XC
13
.
FIG. 2
is conceptually showing a case where a node failure
24
occurred at the ATM cross-connect node XC
12
when a virtual path connection XC
11
-XC
12
-XC
13
-XC
14
is established between the ATM cross-connect nodes XC
11
and XC
14
. The node failures are roughly classified into equipment failures such as breakage of optical transmitting devices (laser diodes etc.) and control abnormality such as a failure of routing LSI.
In the following, the conventional VP protection method in the ATM network system of
FIGS. 1 and 2
employing both the VP end protection and the arbitrary VP protection will be described.
When the line failure
23
occurred on the transmission line XC
12
-XC
13
as shown in
FIG. 1
, the arbitrary VP protection
32
is executed between the ATM cross-connect nodes XC
12
and XC
13
which detected the line failure
23
. In the case where the section protection switching is executed as the arbitrary VP protection
32
, the alternative route XC
12
-XC
16
-XC
13
is used instead of the route XC
12
-XC
13
and thereby communication between the VP end nodes XC
11
and XC
14
is secured via the route XC
11
-XC
12
-XC
16
-XC
13
-XC
14
. Incidentally, in the case where the transmission line XC
12
-XC
13
includes ‘work’ and ‘standby’ signal lines and the line failure
23
occurred on a work signal line between the ATM cross-connect nodes XC
12
and XC
13
, the ATM cross-connect nodes XC
12
and XC
13
can execute switching from the work signal line to the standby signal line according to the APS, instead of the section protection switching.
FIG. 1
is showing a case where the section protection switching is executed by the ATM cross-connect nodes XC
12
and XC
13
, for example.
On the other hand, when the node failure
24
occurred at the ATM cross-connect node XC
12
as shown in
FIG. 2
, the VP end protection
33
is executed between the ATM cross-connect nodes XC
11
and XC
14
which are the VP end nodes of the virtual path connection XC
11
-XC
12
-XC
13
-XC
14
. In the VP end protection
33
, the alternative route XC
11
-XC
15
-XC
14
is used instead of the route XC
11
-XC
12
-XC
13
-XC
14
and thereby communication between the VP end nodes XC
11
and XC
14
is secured via the route XC
11
-XC
15
-XC
14
.
An example of pre-planned VP end protection method is disclosed in Japanese Patent Application Laid-Open No. HEI8-237253 ‘METHOD AND APPARATUS FOR VIRTUAL PATH SWITCHING IN ATM NETWORK’. In the method, an operating virtual path and a standby (spare) virtual path are doubly set between two VP end nodes and virtual path switching from the operating virtual path to the standby virtual path is executed by the VP end nodes in the case of failure. In the VP end protection method, an OAM (Operation And Maintenance) cell, including an switching instruction code for indicating the presence/absence of switching request and a sequence number, is used for controlling the virtual path switching. The transmitting end node transmits the switching control OAM cells periodically on both of the operating virtual path and the standby virtual path, and the receiving end node detects the phase difference between the switching control OAM cells supplied via the two virtual paths by comparing the sequence numbers included in the switching control OAM cells. If the switching instruction code requesting virtual path switching included in the switching control OAM cell reached the receiving end node via the standby virtual path in perfect form, the virtual path switching from the operating virtual path to the standby virtual path is performed compensating the detected phase difference. By the VP end protection method, the switching to the standby virtual path can be executed without instantaneous chopping (i.e. maintaining synchronization of ATM cell timing between the operating and standby virtual paths) and with confirmation of normal operation of the standby virtual path.
Another example of pre-planned VP end protection method is disclosed in Japanese Patent Application Laid-Open No. HEI5-235983 ‘APPARATUS AND METHOD FOR VIRTUAL PATH SWITCHING’. In the method, one or more alternative virtual paths are predetermined corresponding to a work virtual path, and information about the alternative virtual paths are prestored in an alternative virtual path information storing means of a virtual path switching device of each switching end nodes. The virtual path switching device of each switching end nodes further includes a virtual path capacity management means for storing and managing the capacity of the work virtual path,

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