Telephonic communications – Plural exchange network or interconnection – With interexchange network routing
Reexamination Certificate
2000-10-20
2004-07-06
Foster, Roland (Department: 2645)
Telephonic communications
Plural exchange network or interconnection
With interexchange network routing
C379S273000, C379S331000
Reexamination Certificate
active
06760424
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a method for establishing a protected communication segment between two network elements of a telecommunication network as well as to a corresponding telecommunication network.
FIG. 1
shows such a protected segment of a telecommunication network, this comprising a protected connection PECT (standing for “Protected”) and a connection PING (standing for “Protecting”) that protects this connection. Given the example shown in
FIG. 1
, the protected connection PECT proceeds from a network element NEa via network elements NEb and NEc to a network element NEz. Via intervening network elements NEd and NEe, the protecting connection proceeds parallel to the protected connection PECT, i.e. likewise proceeds between the network elements NEa and NEz. As shall be explained in greater detail below, the switching or establishment of the protected connection PECT and of the protecting connection PING is initiated by a management system MS of the telecommunication network.
The individual network element NEa . . . NEz are connected via corresponding termination points to a neighboring network element, whereby the termination points belonging to one and the same connection are connected via what is referred to as a cross connection. Given the example shown in
FIG. 1
, the two network elements NEa and NEz between which the two connections PECT and PING proceed therefore comprises termination points TPa . . . TPc, whereby a cross connection cCC that contributes to the protected connection PECT and therefore conducts the communication traffic must be respectively established between the two termination points TPa and TPb of the network elements NEa and NEz, whereas a protecting cross connection pCC contributing to the protecting connection PING must be respectively established between the two termination points TPa and TPc of the network elements NEa and NEz.
The management system assigns an attribute to every individual cross connection, this attribute unambiguously characterizing its function. For example, this attribute can assume the values “connected”, “protecting” and “not connected”. When a cross connection has the attribute “connected”, this means that this cross connection conducts the actual communication traffic. These cross connections are referenced below as “cCC” (standing for “connected cross connection”) and are shown in
FIG. 1
in the form of solid double lines within the individual network elements NEa . . . NEz. When a cross connection has the attribute “protecting”, this means that this cross connection has a protecting function for another cross connection with which it shares exactly one termination point and that has the attribute “connected”. Cross connections are referenced “pCC” below (standing for “protecting cross connection”) and are shown in
FIG. 1
in the form of broken double lines. A cross connection that has the attribute “not connected” is treated like a cross connection that does not exist. This attribute only plays a part for the sequence of the generation of the protecting pCC cross connections since it is always assumed for the generation of a pCC cross connection that the corresponding cross connection previously had the attribute “not connected”.
Protecting pCC cross connections are only present in those network elements NEa and NEz in which a protected connection and a corresponding protecting connection branch. A network element in which both the cCC cross connection of the protected connection as well as the pCC cross connection of the protecting connection lie automatically switch the communication traffic from the cCC cross connection onto the pCC cross connection if an interruption of the traffic on the protected connection occurs.
It proceeds from the above description that the establishment and switching of the cCC cross connections and pCC cross connections is of critical significance for the activation of the protected segment or, respectively, of the protected connection PECT and of the protecting connection PING. What is thereby understood by an activation of a connection is the physical establishment of the connection, so that the two termination points of the corresponding connection are physically connected to one another after a successful activation, whereby two termination points within a corresponding network element are physically connected to one another upon establishment or creation of a cross connection.
At the time the protected segment is activated, however, cross connections can already be present in the two network elements NEa and NEz, these having been previously locally switched by the operator of the telecommunication network or having not been eliminated after a circuit because of a system error. In the former instance, communication information can already be transmitted via these already existing cross connections at the point in time of the activation of the protected segment, so that these cross connections already existing before the activation of the protected segment dare not be eliminated or deleted. On the other hand, there is the need to activate the protected segment as requested, i.e. to have the protected connection PECT proceed via the network elements NEa-NEb-NEc-NEz and the protecting connection PING proceed via the network elements NEa-NEd-NEe-NEz in the example shown in FIG.
1
.
This problem was hitherto solved such that, before activation of a protected segment, the management system MS has viewed the constellation of existing, locally switched cross connections in the two terminating network elements NEa and NEz together in order to activate the protected connection PECT and the protecting connection PING. The problems that arise given this procedure shall be explained in greater detail below on the basis of the illustrations of
FIG. 3
, whereby it must be noted that the management system MS administers the protected segment in the form of a model in which the protected connection PECT and the protecting connection PING are modelled. The model assumes that the termination points TPa and TPb of the two network elements in
FIG. 1
are respectively connected by a cCC cross connection, whereas the termination points TPa and TPc must be respectively connected by a pCC cross connection. When, as shall be explained in greater detail later on the basis of
FIG. 3
, a constellation of the cross connections that cannot be reconciled with this model already exists in the two network elements NEa and NEz before the activation of the protected segment, the constellation cannot be described by the model. The result of nonadherence to the pre-conditions would be that the forward and return direction of the traffic proceeds differently (in this case, the traffic given the arrangement shown in
FIG. 1
would proceed, for example, from NEa to NEz via NEd and NEe and from NEz to NEa via NEc and NEb), i.e. the position of the protected connection and the protecting connection is not the same then for the forward and return direction of the traffic but depends on the direction of the traffic. A model that could also describe these cases is in fact fundamentally possible. However, it would be significantly more complicated.
A cCC cross connection, i.e. a cross connection with the attribute “connected”, cannot be established between two termination points (for example, between the termination points TPa and TPb according to
FIG. 1
) when one of these two termination points is already connected to another cross connection that has either the attribute “connected” or the attribute “protecting”. As has already been mentioned, in contrast, it is a pre-condition for the establishment of a pCC cross connection, i.e. a cross connection with the attribute “protecting”, that a cross connection with the attribute “not connected” is already present between the corresponding termination points. The establishment of a cross connection with the attribute “not connected” is always possible. However, a cross connection with the attribute “not connected” can only be turne
Mutz Martin
Sarfert Thomas
Bell Boyd & Lloyd LLC
Foster Roland
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