Traffic distribution in ATM network

Details Traffic distribution in ATM network Traffic distribution in ATM network

1996-08-27

1999-09-14

Nguyen, Chau

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

370394, H04L 1256

Patent

active

059533374

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a method for traffic distribution in a network realized using the ATM technology.
ATM is a new connection-oriented packet-switched technique, where the problems of traditional packet networks have been solved by employing short, fixed-size (53-byte) packets, called cells. Each cell consists of a 48-byte payload segment and a 5-byte header. However, the ATM technology is not described here in any greater detail, as the method of the invention does not require any special applications of the ATM technology. A detailed description of the ATM technology is available e.g. in specification).
In an ATM network (as in other packet networks), connections may be secured by using one or more spare routes between the nodes, in addition to the main route. Thus, when necessary (e.g. during maintenance), traffic may be transferred from one route to another.


SUMMARY OF THE INVENTION

It is an object of the present invention to improve both the quality of service offered to the subscriber and information security by utilizing these spare routes. This goal is achieved with the method of the invention.
The idea of the invention is to use, on the same connection (a connection from one subscriber to another), simultaneously at least two different routes by sending cells to different routes either according to a predetermined algorithm or in certain cases (described below) even at random. In this respect, the invention is in contradiction to the ATM specifications, which state that the cells are to follow the same route in order to maintain their relative order. (Cells relating to a particular connection form only a portion of the cells received by the node; i.e. the portion relating to the end-to-end communication between given subscribers.)
With high-speed connections, a possible change in cell order may be corrected by using an AAL protocol comprising a sequence number field for each cell. In these cases the above mentioned random transmission may be used.
The even distribution of traffic achieved by the method of the invention will facilitate dimensioning of the network and decrease delay variation. Thus subscribers may be offered qualitatively better service than before.
Even distribution of traffic will also prevent making external network analyses based on the direction of the traffic (e.g. unravelling authority relations in a military network).
Eavesdropping a virtual connection is extremely difficult in networks employing the solution of the invention, as all possible routes would need to be known.
The method of the invention has no requirements as regards the ATM network; the solution of the invention may be implemented simply as control measures on the periphery of the network.
With slow user connections, the method sets no requirements for the upper protocol layers, which may consequently be freely chosen.


BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention and its preferred embodiments will be described in greater detail with reference to examples in accordance with the accompanying drawings, in which:
FIG. 1 shows a section of a packet-switched network where there are two possible routes between two nodes,
FIG. 2 illustrates distribution of traffic in the node shown in FIG. 1, and
FIG. 3 shows transmission and reception in the nodes at the extreme ends of a route.


DETAILED DESCRIPTION

FIG. 1 shows a section of an ATM network where a connection between subscriber A (first party of a data link) and subscriber B (second party of a data link) has two possible routes between subscriber nodes A and B, i.e. A-B and a-b, so that may be transmitted to subscriber B (the former route via node A2 and the latter via node A1), and may be transmitted to subscriber A (the former route via node A2 and the latter via node A1).
In the invention, instead of using only one route at a time and keeping other routes in reserve, several, preferably all allocated, usable routes are used on the connection between the nodes. This is achieved by sending cells alternat

REFERENCES:
patent: 5231649 (1993-07-01), Duncanson
patent: 5285441 (1994-02-01), Bansal et al.
patent: 5293378 (1994-03-01), Shimizu
patent: 5357508 (1994-10-01), Le Boudec et al.
patent: 5386415 (1995-01-01), Ito et al.
patent: 5394398 (1995-02-01), Rau
Recommendation G.704, CCITT, "Synchronous Frame Structures Used At Primary and Secondary Hierarchical Levels", 1991.
ITU-T Recommendation I.361, "B-ISDN ATM Layer Specification", Mar. 1993.
ITU-T Recommendation I.362, "B-ISDN ATM Adaption Layer (ALL) Functional Description", Mar. 1993.
ITU-T Recommendation I.363, "B-ISDN ATM Adaption Layer (AAL) Specification ", Mar. 1993.
ITU-T Recommendation I.610, "B-ISDN Operation and Maintenance Principles and Functions", Mar. 1993.

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