Stacked address transport in connection oriented networks

Details Stacked address transport in connection oriented networks Stacked address transport in connection oriented networks

1998-06-11

2002-12-31

Nguyen, Chau (Department: 2663)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S410000

Reexamination Certificate

active

06501755

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the field of connection oriented communications networks and more particularly, to a method for stacked address transport in such networks.
According to preferred embodiments, the invention relates to the signalling of network messages across multiple network entities through which message addresses are not routable. Such signalling is accomplished by transporting, together with a terminal address, all locally routable addresses associated with the various network entities through which the message is to be transported. In other preferred embodiments of this invention, a method is described for the encapsulation and transport of multiple message addresses within a call set up message which employs a message address stack for that purpose. According to this particular preferred embodiment, the method is adaptable to Asynchronous Transfer Mode (“ATM”) network devices which can “PNNI” network protocols, namely Private Network-Network Interface and Private Network Node Interface signalling and routing protocols.
BACKGROUND OF THE INVENTION
Recent technological, economic and regulatory trends in the fields of telephony and data communications have resulted in the need for enhanced network interoperability. Where internetworking is to take place among connection oriented networks which operate using different addressing schemes, for instance a plurality of networks comprised of interconnected private networks or service provider networks, special techniques must usually be deployed in order for a message sent from the originating end system to properly route via the intermediate networks to the destination end system. Traditionally, network interoperability has been achieved by the use of routing tables, to support address relocation across different intermediate network boundaries.
Signalling in connection oriented networks is the process of establishing, maintaining and releasing a message connection through the exchange of connection establishment request and connection establishment acknowledgement messages through the network nodes along a given message path. For signalling purposes, each network node device in a given network may be associated with a routing table or the like which provides internal addressing information for all of the destination addresses that are employed by each of the network users. Generally, it is important to maintain routing tables which are relatively compact in size, in that limited memory may be available to each particular network node device for storage of its associated routing table. In any event, and as explained below, if the routing table must grow substantially as users are added or as the network grows, then this results in complexity which limits the size of the network which can be effectively attained.
Where destination addresses are aggregatable or topologically assigned, such that all addresses which are topologically related to each other can be summarized to a small number of addresses that are typically leading digits or prefixes (for example, addresses which are accessed off the same node), the routing table associated with each of the network node devices of the intermediate networks may be maintained to a manageable size. This is because the network node devices within the intermediate networks can advantageously employ prefix-based routing. However, with the advent of applications in telephony such as local number portability, mobility and customer owned addresses, the size and complexity of routing tables can be expected to increase as more addresses lose their topological significance. Where addresses are no longer assigned topologically, conventional switching systems may no longer scale well to larger and larger address spaces as the number of interworked networks which must be addressed is ever increased. This results from the fact that it would be necessary in such circumstances to have a routing table entry for every destination network node device on the interworked network space.
There are also instances where a given intermediate network, according to current standards and practices, may be unable or unwilling to route directly using the address spaces of other interworked networks. These instances include the implementation of Virtual Private Networks (“VPNs”), the incorporation and management of networks whose address spaces have been structured without considering the addressing scheme of the intermediate network, and the need in a given networking space to support location management for mobile end-user devices. As well, another example which may result in similar addressing problems for an intermediate network occurs in the context of topological reorganization of the address spaces of networks to which the intermediate network is connected. Yet another example involves situations where the addresses used by the networks connected to the intermediate network are not globally unique as is often the case for the previously mentioned VPNs.
As one technique for achieving some degree of network interoperability, it has been known to transport a message address between two networks where it may be used, across a single network where the message address cannot be used. This technique is sometimes known to those skilled in this art as tunnelling or tunnelled signalling. Typically, in tunnelled signalling, a signalling message employs an endpoint message address which is of routing significance to both the originating and destination interworked networks. Prior to a signalling message arriving at the ingress node of the intermediate network through which the signalling message is to be routed, the endpoint address is encapsulated in the signalling message and is thereafter routed to the appropriate egress node of the intermediate network via an intermediate address which is of routing significance to the intermediate network. Upon emerging from the egress node of the intermediate network, for instance at the ingress node of the destination network, the signalling message reverts to the use of the original endpoint message address which retains its routing significance to the destination network. Thus, this signalling technique is known as “tunnelling” since the intermediate network is unaware of the originating and endpoint destination addresses. The intermediate network merely routes these external addresses transparently.
In current ATM signalling standards, various mechanisms for tunnelling have been specified. For instance, such mechanisms are found in the ATM User-Network Interface (“UNI”) Specification Versions 2.0, 3.0 and 4.0, respectively dated June 1992, August 1993 and July 1996, each of which is published by the ATM Forum. These particular standards apply in routing connections between private ATM endpoints identified by NSAP formatted ATM addresses across a public network supporting E. 164 ATM addresses. Tunnelled signalling according to these known standards may be supported by the use of an existing message field or Information Element (“IE”) within the message format of a connection establishment request message, for instance a Call SETUP request message. The existing message field in question is known to those skilled in this art as the Called Party Subaddress IE, and this field may be used to store and encapsulate the destination endpoint address to which a message or call is destined to be routed.
By way of example, in signalling a Call SETUP request message, an egress network node device of an intermediate network may temporarily place the destination endpoint address of the called party, also known as the Called Party Number, into the Called Party Subaddress IE of the SETUP request message. That same network node device may then temporarily place the egress endpoint address of the intermediate network into the Called Party Number field of the Call SETUP request message. The Call SETUP request message can thereafter be routed to the egress endpoint address by the intermediate network. When the SETUP request message enters the destinati

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