Multiplex communications – Network configuration determination
Patent
1997-01-28
1999-07-27
Nguyen, Chau
Multiplex communications
Network configuration determination
370385, 370400, H04L 100
Patent
active
059302364
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for preventing circular routing in a telecommunication network.
In principle, the solution of the invention is applicable to any communication network, but is, however, primarily intended to improve the management of routing in a common channel signalling system. This signalling system is described in detail in the CCITT blue book Specifications of Signalling System No. 7 (Melbourne 1988).
In common channel signalling, the method of the invention is limited particularly to the message transfer part (MTP) acting as the transmission system of this network. MTP transfers signalling messages between locations of user functions.
Circular routing refers to a situation where messages sent in a network start to circle in a loop and never reach the destination node. The messages may then even return to the originating node for onward routing towards the same destination.
Point 13 in the CCITT recommendation Q.704 proposes that particular management messages be used for notifying of the unavailability, restriction and availability of a signalling route. These messages include e.g: transfer point notifies adjacent signalling points that they must no longer route signalling messages via that transfer point, transfer point notifies adjacent signalling points that they may route signalling messages via that transfer point and, transfer point notifies adjacent signalling points that they should, if possible, no longer route signalling messages via that transfer point. According to the recommendation, transfer-restricted messages are a national option.
Below, transfer-prohibited messages are referred to as TFP messages, transfer-allowed messages as TFA messages and transfer-restricted messages as TFR messages. As a signalling network is concerned, the nodes are also referred to as signalling points. For a more detailed description of the messages, reference is made to the above-identified CCITT recommendation.
The problem of the procedures described in the CCITT recommendation is that the TFP messages prevent a loop between two points but are unable to prevent loops involving three or more signalling points. This is illustrated by an exemplary network of FIGS. 1a through 1d comprising four signalling points A through D. A primary route, denoted by reference I, and a secondary (standby) route, denoted by reference II, originates from each signalling point. (This example, where standby routes form a loop, cf FIG. 1a, is quite classical.) Following notations are used in the description:
______________________________________ A: B AV-EX a route originating from point A
passing subsequently via a channel
system leading to point B is in
status AV-EX.
______________________________________
______________________________________ AV-EX a route transmitting traffic,
AV-SP an available standby route,
UA-link an unavailable route because of
channel system failure.
______________________________________
With all channel systems leading to point D available (FIG. 1a), routing information of the signalling network to point D is as follows:
______________________________________ (i) A: D AV-EX B: D AV-EX C: D AV-EX
B AV-SP C AV-SP A AV-SP.
______________________________________
Should channel system C.fwdarw.D fail (FIG. 1b), signalling point C switches to channel system A and sends a TFP message (A.fwdarw.C.fwdarw.D) (a TFP message prohibiting message transmission from point A to point D via point C). The respective route is unavailable to signalling point A, and the routing status remains as:
______________________________________ (ii) A: D AV-EX B: D AV-EX C: D UA-link
B AV-SP C AV-SP A AV-EX.
______________________________________
Should channel system B.fwdarw.D fail subsequently (FIG. 1c), signalling point B switches to channel system C and sends a TFP message (C.fwdarw.B.fwdarw.D). Signalling point C does not process the TFP message because the respective route is unavailable to it, and the current routing status is:
__________________________
REFERENCES:
patent: 4656658 (1987-04-01), King
patent: 5084816 (1992-01-01), Boese et al.
patent: 5088032 (1992-02-01), Bosack
patent: 5239537 (1993-08-01), Sakauchi
patent: 5241533 (1993-08-01), Kimoto et al.
patent: 5253248 (1993-10-01), Dravida et al.
patent: 5265092 (1993-11-01), Soloway et al.
patent: 5345503 (1994-09-01), Lee
patent: 5481673 (1996-01-01), Michelson
Hyun Soon-Dong
Nguyen Chau
Nokia Telecommunications Oy
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