Abstract:
A multi service platform including a layer two switching component and a layer three switching component is connected to a layer two network and a layer three network. The layer two switching component is a terminating point for the layer two network, whereas the layer three switching component terminates the layer three network A virtual UNI connection is established between the components increasing reliability of end to end connections across the networks, and simplifying provisioning of these types of networks.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of communications. More particularly, the present invention relates to improving reliability when interconnecting layer two and layer three networks. 
   2. Background Information 
     FIG. 1  illustrates an example of today&#39;s networking environment. In today&#39;s networking environment, layer two access networks  12  are often employed to access layer three core networks  14 . Thus, a customer  10  can access the layer three network  14  using layer two access mechanisms. This approach combines the flexibility of maintaining layer two access with the flexibility of supporting multiple virtual connections from a physical access port. These multiple virtual connections are available without full mesh virtual connections among all customer sites due to the layer three connectionless forwarding capabilities. 
   An example of such a topology is an IP (Internet protocol) enabled frame relay/ATM (asynchronous transfer mode) network. Failures within the layer two network  12  are handled by the layer two failure recovery schemes. Failures within the layer three network  14  are handled by the layer three failure recovery schemes. Failures on the UNI (user to network interface) connections  16  between the layer two network  12  and the layer three network  14 , however, are not protected by these recovery schemes and thus become single points of failure. 
   As shown in  FIG. 2 , a multi service platform  20  is conventionally provided in the layer three network  14 . The multi service platform  20  includes layer two switching capabilities  22  and layer three switching capabilities  24 . In today&#39;s multi service platforms  20 , the layer two portion  22  is independent from and isolated from the layer three portion  24 . Typically, the layer three portion  24  of the multi service platform  20  terminates the UNI connection  16 . Thus, when the UNI connection  16  (either the link or a port) fails, the layer two network  12  will not re-route a circuit to the multi service platform  20  in the layer three network  14  because the layer two network only extends to the UNI connection  16 . Although  FIG. 2  shows a core layer three network  14 , another layer two network may be provided instead of the layer three network  14 . 
   Current solutions addressing the single point of failure problem include dual homing from a customer site  10  to the layer three core  14 . In this case, when one connection fails, the other connection can maintain connectivity. This approach, however, consumes too many network resources by requiring both paths to be permanently maintained in the layer two network  12 , also adding significant complexity to the provisioning and maintenance procedures for this service. 
   Another solution reduces the length of the UNI connection  16  between the layer two network  12  and the layer three network  14  by deploying layer two and layer three switches within the same central office. Thus, the connection  16  becomes an intra-central office connection. This solution, however, increases the overall switch deployment cost and is still subject to a single point of failure. 
   Thus, a solution is needed to address the single point of failure problem without increasing consumption of network resources. 
   Provisioning a circuit using current multi service platforms  20  entails a complicated two step process. Initially, the terminating multi service platform  20  is identified, and it is determined which layer two switch will connect to the multi service platform  20 . A circuit can then be provisioned between the customer  10  and the identified layer two switch, which connects to the multi service platform  20 . Finally, the layer three portion  24  of the platform  20  must be provisioned. 
   It would be desirable to have a simpler provisioning process. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is further described in the detailed description that follows, by reference to the noted drawings by way of non-limiting examples of embodiments of the present invention, in which like reference numerals represent similar parts throughout several views of the drawings, and in which: 
       FIG. 1  is a diagram showing a prior art networking environment; 
       FIG. 2  is a diagram showing a prior art networking environment, including a multi-service platform; 
       FIG. 3  is a diagram showing a networking environment, including a multi-service platform, according to an aspect of the present invention; and 
       FIG. 4  is a diagram showing a networking environment, including a multi-service platform, according to another aspect of the present invention. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   The present invention relates to increasing reliability of interconnected layer two and layer three networks. The increased reliability is achieved by providing a virtual UNI between layer two and layer three switches within a multi service platform. 
   In view of the above, the present invention through one or more of its various aspects and/or embodiments is presented to accomplish one or more objectives and advantages, such as those noted below. 
   According to an aspect of the present invention, a multi service platform includes a layer two switching component, a layer three switching component, and an internal connection. the internal connection terminates at the layer two switching component and at the layer three switching component. Thus, layer two capabilities and layer three capabilities are integrated together. In one embodiment, the connection is an internal virtual UNI connection. 
   According to another aspect of the present invention, a network includes a layer two network, a layer three network, and a platform. The platform includes a layer two switching component, a layer three switching component and a connection between the layer two switching component and the layer three switching component. The layer two switching component of the platform is protected by the layer two network&#39;s failure restoration, and the layer three switching component of the platform is protected by the layer three network&#39;s failure restoration. 
   In one embodiment, the connection is an internal virtual UNI connection. Moreover, the layer two network may be an ATM network, and the layer three network may be an IP network. Similarly, the layer two switching component of the platform may be an ATM switch, and the layer three switching component of the platform may be an IP router. 
   According to a further aspect of the present invention, a method is provided for routing traffic across a layer two network and across a layer three network. The method includes routing traffic from a customer across the layer two network to a layer two switching component in a platform. The method also includes routing traffic from the layer two switching component across an internal virtual UNI connection to a layer three switching component in the platform. The method further includes routing traffic from the layer three switching component across the layer three network. 
   In one embodiment, the layer two network is an ATM network. In another embodiment, the layer three network is an IP network. The layer two switching component of the platform may be an ATM switch. The layer three switching component of the platform may be an IP router. 
   According to yet another aspect of the present invention, a method is provided for provisioning a circuit in a layer two/layer three network. The method includes locating a customer&#39;s port, locating an internal virtual UNI port, and establishing a connection between the customer&#39;s port and the internal virtual UNI port. 
   According to still yet another aspect of the present invention, a method is provided for routing traffic across a plurality of layer two networks. The method includes routing traffic from a customer across a first layer two network to a layer two switching component in a platform. The method also includes routing traffic from the layer two switching component across an internal virtual UNI connection to a layer three switching component in the platform. At the layer three switching component, virtual channel information is determined. Then, traffic the virtual channel information are routed from the layer three switching component across the internal virtual UNI connection to the layer two switching component in the platform. Finally, the method includes routing traffic from the layer two switching component across another layer two network based on the virtual channel information. 
   The various aspects and embodiments of the present invention are described in detail below. 
   The present invention improves reliability of interconnected layer two/layer three networks by extending the layer two network to the layer two switching component of a multi service platform. Thus, if an interface between the layer two switch and the layer two switching component of the multi service platform fails, the layer two network failure recovery scheme re-routes the circuit to the layer two switching component of the multi service platform. Similarly, if an interface between the layer three switch and the layer three switching component of the multi service platform fails, the layer three network failure recovery scheme re-routes the circuit to the layer three portion of the multi service platform. 
   Referring now to  FIG. 3 , an embodiment of the present invention is shown. The multi service platform  20  includes an internal virtual UNI connection  30  which connects the layer two switching component  22  of the platform  20  and the layer three switching component  24  of the platform  20 . The UNI connection  30  is considered to be virtual because it is within the multi service platform  20 , rather than between two physical ports. 
   In one embodiment, the layer two network  12  is an ATM network, and the layer three network  14  is an IP network, although any other type of layer two and layer three networks can be provided, for example, an ethernet network. In the ATM/IP embodiment, the multi service platform  20  includes an ATM switch as the layer two portion  22  and an IP router as the layer three portion  24 . An exemplary multi service platform  20  is an Alcatel 7670 RSP (routing switch platform), available from Compagnie Financiere Alcatel of France. 
   In the ATM/IP embodiment, the ATM network  12  terminates on the ATM switch  22  in the platform  20 . The IP network  14  connects to the IP router  24 . A virtual internal UNI  30  connects the IP router  24  and the ATM switch  22  within the multi service platform  20 . Thus, the ATM network  12  includes the ATM switch  22  and accordingly protects the switch  22  with its failure restoration. Similarly, the IP router  24  is part of the IP network  14  and is thus covered by the IP network&#39;s failure recovery schemes. 
   Implementation of the internal virtual UNI  30  is architecture dependent and relatively straight forward. The internal virtual UNI  30  could be a standard ATM connection using internal ATM ports. Alternatively, the connection  30  could be between a chip on the router  24  and a chip on the ATM switch  22 . In another embodiment, the ATM connection is simpler than a standard ATM connection. In still another embodiment when the router  24  and switch  22  are on a common bus, the connection  30  can be implemented with control signaling. 
   The internal virtual UNI  30  thus becomes the only unprotected link. The failure probability of the link  30  is low, however, due to fact that the connection is internal to the platform  20  and not subject to cable cut failure, and because the link is so short. Moreover, the reliability is further enhanced by the extension of the layer two network&#39;s recovery scheme and the extension of the layer three network&#39;s recovery scheme. 
   Provisioning of a circuit in a network employing the present invention is also simplified. That is, the provisioning is a one step process. The customer&#39;s port and the internal virtual UNI&#39;s port are located and then a connection can be established. 
   Another advantage of the present invention is the saving of physical ports and associated transport facilities on the multi service platform  20  for trunking. This savings contrasts with deployment of a layer two and layer three switch in the same physical central office and interconnecting the switches with physical trunk ports. 
   Another embodiment is shown in  FIG. 4 . In  FIG. 4 , a layer two network  12  is provided between the multi service platforms  20 . In this case, the layer two switching component  22  connects to each layer two network  12 . In operation, the layer two switching component  22  directs all traffic via the virtual UNI  30  to the layer three switching component  24 . The layer three switching component  24  then consults its routing tables in order to determine how to route the traffic. Subsequently, the layer three switching component  24  selects an appropriate virtual channel and forwards this information back to the layer two switching component  22 , which then forwards the traffic to the correct interface based upon the received information. 
   Thus, the present invention provides an internal virtual UNI connection between layer two and layer three switching components of a multi service platform thereby improving end to end reliability. It is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in its aspects. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed; rather, the invention extends to all functionally equivalent structures, methods, and uses such as are within the scope of the appended claims. 
   In accordance with various embodiments of the present invention, the methods described herein are intended for operation as software programs running on a computer processor. Dedicated hardware implementations including, but not limited to, application specific integrated circuits, programmable logic arrays and other hardware devices can likewise be constructed to implement the methods described herein. Furthermore, alternative software implementations including, but not limited to, distributed processing or component/object distributed processing, parallel processing, or virtual machine processing can also be constructed to implement the methods described herein. 
   It should also be noted that the software implementations of the present invention as described herein are optionally stored on a tangible storage medium, such as: a magnetic medium such as a disk or tape; a magneto-optical or optical medium such as a disk; or a solid state medium such as a memory card or other package that houses one or more read-only (non-volatile) memories, random access memories, or other re-writable (volatile) memories. Accordingly, the invention is considered to include a tangible storage medium or distribution medium, as listed herein and including art-recognized equivalents and successor media, in which the software implementations herein are stored. 
   Although the present specification describes components and functions implemented in the embodiments with reference to particular standards and protocols, the invention is not limited to such standards and protocols. Each of the standards for Internet and other packet-switched network transmission and public telephone networks represent examples of the state of the art. Such standards are periodically superseded by faster or more efficient equivalents having essentially the same functions. Accordingly, replacement standards and protocols having the same functions are considered equivalents.