Multiplex communications – Pathfinding or routing
Reexamination Certificate
2001-01-29
2003-06-03
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
C370S252000, C370S390000, C709S241000
Reexamination Certificate
active
06574215
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
In modern communications networks, which comprise a large number of network nodes, data is frequently transmitted within data packets. As a rule, a so-called routing statement is thereby transmitted in association with a data packet, specifying a destination network node or a destination terminal and, possibly, also a route leading to it. Network nodes which are involved in the data transmission use the routing statement—or parts of it—to in each case determine the network node to which the received data packet is intended to be relayed, in order to pass this data packet through the communications network to a destination network node or destination terminal. If a routing statement formed in the source network node itself specifies a complete route to a destination network node or a destination terminal, this is referred to as explicit routing (or source routing). In this case, the routing statement defines, for each network node located on the route, the network node to which the data packets associated with the routing statement should in each case be relayed. An alternative method is so-called hop-by-hop routing, in which, although a routing statement formed in the source network node specifies a destination network node or a destination terminal, it does not, however, specify a route leading to it. Instead of this, the specific route is defined by those network nodes which are involved in the transmission of the data packets and which each autonomously use the routing statement and the network topology to decide the network nodes to which the data packets should in each case be relayed.
These days, a large number of routing methods are used for data transmission on the Internet. Data transmission on the Internet is based on the so-called Internet Protocol (IP) in which each data packet to be transmitted contains as the routing statement a so-called IP address which identifies the destination terminal. Although, on the one hand, such a routing statement can be produced very easily, on the other hand it requires relatively time-consuming evaluation of the IP address by network nodes which are involved in a data transmission, in order to gain the information required for relaying the data packets.
Prior art routing methods for reducing this complexity are so-called label-switching methods, in which each data packet provided with an IP address is preceded by an additional routing statement, from which the information required for relaying the data packets can be obtained very quickly. The additional routing statement in this case essentially comprises one or more identification records, which may be used as table indices for routing information tables provided in network nodes. The process of determining the information required for relaying the data packets can thus be reduced to table accesses. The original routing statement—that is to say the IP address—is still also transmitted so that data packets can also be passed on in subregions of the communications network which are not designed for a label-switching method. When handing over to such a subregion, the additional routing statement is removed once again, and the data packets are relayed on the basis of the IP address and in accordance with the Internet Protocol.
A label-switching method has been found to be particularly advantageous in conjunction with explicit routing since, in this case, route definition may be carried out only in the source network node, for example using a Dijkstra routing algorithm. In a label-switching method based on explicit routing, a sequence of identification records is combined in the routing statement, with these identification records each denoting, for each of the network nodes located on the route, that network node to which data packets associated with that routing statement should be relayed.
However, until now, label-switching methods used in conjunction with explicit routing still have a weakness. No way has yet been found for using these methods to transmit a data packet by explicit routing in parallel to a number of destination network nodes and/or destination terminals. When such a transmission mode, which is also referred to as multicast routing, were present, the range of applications of a label-switching method would be extended considerably in conjunction with explicit routing. In particular, this would allow applications such as point-to-multipoint links and conference circuits to be provided in a simpler manner than in the past.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method of transmitting data packets in a heterogeneous communications network which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this general kind. More specifically, the novel method should allow transmitting data packets or connection setup messages on the basis of routing statements which are intended for different routing methods, between a source network node and a number of destination network nodes and/or destination terminals.
With the above and other objects in view there is provided, in accordance with the invention, a method of transmitting data packets in a communications network from a source network node to a plurality of destinations (i.e., destination network nodes and/or destination terminals) along a branching route specified by a number of routing statements provided for different routing methods. The novel method comprises the following steps:
producing a first routing statement in a source network node, the first routing statement
having branching information for each branch in the route and having partial routing information, specifying the route branch, for each route branch of the given branch; and
containing a cross-reference to a further routing statement;
allocating the first routing statement to at least one data packet to be transmitted, and transmitting to network nodes immediately following the source network node on the route; and
controlling with the routing statement the network node receiving the routing statement, with
branching information initiating transmission of a received data packet through network nodes denoted by the partial routing information allocated to a route branch and immediately following the branch, to which, furthermore, the respective partial routing information is transmitted, with or without information in each case denoting one of these nodes, as the routing statement, and
initiating, with the network node receiving the routing statement, a valuation of the further routing statement denoted by the cross-reference when a cross-reference relating to this network node is present, and the received data packet being passed on to network nodes or terminals denoted in the further routing statement.
This first method is particularly relevant for transmission of data packets.
With the above and other objects in view there is also provided, in accordance with the invention, a method of transmitting connection setup messages in a communications network from a source network node to a plurality of destinations along a branching route specified by a plurality of routing statements provided for different routing methods. The novel method comprises the following steps:
producing a first routing statement in a source network node, the first routing statement
having branching information for each branch in the route and having partial routing information, specifying the route branch, for each route branch of the relevant branch; and
containing a cross-reference to a further routing statement;
allocating the first routing statement to at least one connection setup message to be transmitted, and transmitting the first routing statement to network nodes immediately following the source network node on the route; and
controlling a network node with the routing statement received thereby, wherein
branching information initiating transmission of a received connection setup message through network nodes denoted by the partial routing in
Chin Wellington
Greenberg Laurence A.
Locher Ralph E.
Pham Brenda
Siemens Aktiengesellschaft
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