Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-12-29
2002-03-12
Olms, Douglas (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S401000
Reexamination Certificate
active
06356563
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed generally to apparatus and methods for uniquely assigning and utilizing conventionally locally-significant identifiers in a multi-protocol interworked network as global identifiers.
BACKGROUND OF THE INVENTION
A large portion of networking traffic in the world is handled by interworked networks, which involves the transfer of data across networks that follow different network protocols. An important example of interworking is the interconnection of Frame Relay (FR) networks and Asyncrhononous Transfer Mode (ATM) networks.
A typical configuration of an FR-ATM service interworked network is a hub-and-spoke configuration such as is shown in FIG.
1
. FR-ATM service interworked hub-and-spoke networks are often used by customers that require communication between a relatively large number of remote sites and a small set of data center hub sites. FR-ATM service interworking provides a means of bundling low-speed Permanent Virtual Circuits (PVCs) from remote sites into high-speed (e.g., DS
3
) data center access links.
In a hub-and-spoke network such as network
100
, FR remote sites
101
a-b
are connected to ATM edge nodes
103
a-b
via FR PVCs, and ATM remote site
101
c
is connected directly to an ATM edge node
103
c
. These FR PVCs are established by FR network access shelves (NASs)
102
a-b
. Each FR NAS
102
a-b
has a plurality of network access ports for connecting to FR remote sites. The FR NAS bundles FR data together from the various network access ports, performs protocol conversion, and forwards the bundled and converted data to an ATM edge node via a feeder trunk (e.g., a single DS-
3
). The ATM edge nodes
103
a-c
provide access to the network cloud of switches and trunks that transport PVCs to an FR-ATM service gateway user-to-network
etwork-to-network (UNI/NNI) interface. The PVCs pass through the service gateway and enter the ATM network cloud. The ATM network cloud delivers the PVCs to the destination ATM edge nodes.
Each remote site and each ATM edge node is identified by one or more identifiers. In portions of the network using the FR protocol, the identifier is called a Data Link Connection Identifier (DLCI). In portions of the network using the ATM protocol, two identifiers, a Virtual Path Identifier (VPI) and a Virtual Channel Identifier (VCI), are used in conjunction. Each of these DLCI, VPI, and VCI identifiers is selected from a limited range of possible values and is either located in the header of, or encapsulated within, a message sent through the network.
Each PVC is terminated at one end by a remote site having an assigned DLCI and at the is other end by an ATM edge node having an assigned VPI/VCI. However, each of these identifiers typically only has local significance. In other words, one particular network element may interpret a particular DLCI (or VPI/VCI) to identify one particular PVC associated with one network access port, while another different network element may interpret the same DLCI (or VPI/VCI) to identify another different PVC associated with a different network access port. Network protocols conventionally using locally-significant identifiers are referred to herein as local network protocols.
FIG. 2
illustrates an example of conventional local addressing (i.e., using a local network protocol) in an FR-ATM service interworked network
200
. The interworked network
200
includes an FR network
201
interconnected with an ATM network
202
. The FR network
201
includes FR sites A and B, and the ATM network
202
includes ATM sites X and Y. In order transmit data to ATM site X FR site A would use the local outgoing path defined by, e.g., DLCI=100, and FR site B would use the local outgoing path defined by, e.g., DLCI=101. In the other direction, ATM site X would use the local outgoing path defined by, e.g., VPI/VCI 2/1035 to transmit data to FR site A, and ATM site X would use the local outgoing path defined by, e.g., VPI/VCI 3/1060 to transmit data to FR site A. The DLCIs and VPI/VCIs are different for different sites because the DLCIs and VPI/VCIs are interpreted locally. Thus, the use of such local identifiers provides a scheme for selecting a local outgoing path.
The use of FR-ATM service interworking conventionally requires the assignment and use of both FR DLCI values and ATM VPI/VCI values, each of which has significance only at the local FR or ATM site. A problem with this local addressing scheme is that customers who utilize interworked networks must often handle multiple different sets of identifiers. Customers often find the non-unique assignment of multiple different sets of identifiers to be troublesome and difficult to manage.
There is therefore a need for a satisfactory method for globally assigning network-wide global identifiers for sites in heterogeneous networks (e.g., networks having FR and ATM sites). It would be a further benefit to be able to assign and utilize such global identifiers in a way that is compatible with existing network equipment and protocols.
SUMMARY OF THE INVENTION
The present invention solves at least the above-identified problems of the prior art. A global addressing and identifier assignment scheme is presented herein. The scheme introduces a global (e.g., throughout the entire interworked network) interpretation for multiple identifiers within an interworked network. The term “global identifier” or “global address” is used herein to describe an assignment by a service provider and/or customer of conventionally local identifiers in a manner that permits meaningful reference to the assigned values from remote locations.
Thus, according to one aspect of the present invention, instead of serving as locally significant identifiers for routing traffic to remote sites, the conventionally local identifiers may be interpreted as global identifiers (a.k.a. global addresses) for remote destination sites. For example, regardless of whether a destination site is a frame relay (FR) or asynchronous transfer mode (ATM) site, source FR sites may use the destination site's global Data Link Connection Identifier (G-DLCI), and source ATM sites may use the destination site's global Virtual Path Identifier/Virtual Channel Identifier (G-VPI/VCI), for routing traffic to the destination site. These global identifiers may be used in FR-to-FR transmissions as well as ATM-to-ATM transmissions. Further, ATM network nodes may continue to use the VCI/VPI to identify a destination site, and FR nodes may continue to use the DLCI to identify a destination site, just as in conventional networks, except that the identifiers are globally, instead of locally, assigned.
According to another aspect of the invention, a network-wide global addressing and identifier assignment method for interworked networks is provided, along with various exemplary embodiments of such a method. For example, in an FR-ATM service interworked network, a unique global DLCI and a unique global VPI and/or VCI may be assigned for each customer site in the interworked network, regardless of whether the site is an FR site or an ATM site.
Global identifiers may be preferably defined and assigned to each site in order to maximize the number of unique global identifiers available, since re-use of DLCIs and/or VPI/VCIs introduces the potential for confusion. Global identifier assignment schemes preferably should also effectively handle cases where the number of customer locations exceeds the number of distinct values available within an identifier (e.g., DLCI) usable range. In some assignment schemes, overlapping ranges of values for each protocol may be identified and taken into consideration in assigning the addresses such that each node has an identifier of a first protocol and an identifier of a second protocol having identical values and/or values that are otherwise related to each other in some way. In further assignment schemes, assignments may be made sequentially so that assignments can easily be performed automatically by a computer.
Assignments may be made such th
Nicoll Peter R.
Pedersen John L.
AT&T Corp.
Banner & Witcoff , Ltd.
Olms Douglas
Vanderpuye Ken
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