US 7664123 Generalized virtual router

ABSTRACT – A generalized virtual router is disclosed. A routing and switching apparatus includes a switching fabric and a matrix of switching and routing elements. At least some of the elements are interconnected by the switching fabric. A router control provides control for the switching fabric. The apparatus has both cross-connect and routing functionality.


This invention relates to virtual routers (VRs) and, in particular, a generalized virtual router (GVR) that is an IP-based layer-3 VR combined with the functionality of a virtual private packet/TDM/wavelength/fiber GMPLS-based cross-connect.


While the use of multi-protocol label switching (MPLS) in core networks is well known, providing generalized multi-protocol label switching (GMPLS) within core networks is currently being explored.

GMPLS can be understood as follows. First, a label edge router (LER), a label switch path (LSP) and a label switch-router (LSR) are components within an MPLS network. LERs are routers on the edge of the network that attach labels to packets based on a forwarding equivalence class (FEC). An LSP is essentially the predetermined route that a set of packets bound to an FEC traverse through an MPLS network to reach their destination. Each LSP is unidirectional. An LSR is a router capable of forwarding packets according to a label switching algorithm. As opposed to LERs which can be found On the edge of the network, LSRs are found in the core of the network.

In terms of overall operation, incoming packets to an MPLS network are assigned a label by an LER. Packets are forwarded along an LSP where each LSR makes forwarding decisions based solely on the contents of the label. At each hop, the LSR strips off the existing label and applies a new label which tells the next hop how to forward the packet. GMPLS extends MPLS from supporting packet switching (PSC) interfaces and switching to include support of the following three classes of interfaces and switching: time-division multiplex (TDM), lambda switch (LSC) and fiber-switch (FSC).

A core network is a backbone network that provides any-to-any connections among devices on the network. Core networks are typically a combination of switching offices and a transmission plant connecting switching offices together. Many core networks include multiple ATM switches configured in a multi-linked mesh topology. Other core networks include IP routers. Yet another type of core network includes Synchronous Optical Network (SONET)/Synchronous Digital Hierarchy (SDH) Optical-Electrical-Opticals (OEOs) with routers at the edge. Providers associated with any of these types of core networks typically offer a limited range of services to customers.

United States Patent Application Publication 2003/0147402 A1 discloses a provider network offering multi-service virtual private cross-connect (VPxC). The VPxC can appear to a customer network as a virtual node within the network and may be addressed using a client addressing scheme. A VPxC can also use techniques associated with a virtual private optical cross-connect (VPOxC), with the exception that the VPxC m ay a Iso accommodate packet-based links, such as IP, ATM, Ethernet or other packet-based links (a VPxC is a Generalized Virtual Private Cross-Connect). In a Provider Provisioned Virtual Private Service Network, a VPxC may provide packet-based layer-2, layer-3 and GMPLS-based Optical/TDM virtual private network (VPN) services where the concept of GMPLS-based Virtual Private optical/TDM cross-connect may be extended to include packet-based VPNs. The VPxC may also use technology developed in provider provisioned virtual private networks (e.g., layer-3, layer-2, OVPNs) such as VPN auto-discovery used for VPOxC and generalized VPN (GVPN) as applied to layer-2 circuits, for example. A provider network offering VPxC services can include devices such as optical cross-connects, routers, ATM, Frame Relay or Ethernet switches, SONET/SDH cross-connects and other similar devices.

A VR has different functionality than a VPxC. A VR is an emulation of a physical router at the software and hardware levels. Furthermore, a VR has the same mechanisms as physical routers, and can therefore be used to provide layer-3 VPN services. Each VR can run any routing protocols (OSPF, RIP, BGP-4). VR-based mechanisms include VR using Border Gateway Protocol (BGP) (see Hamid Ould-Brahim et al. “Network based IP VPN Architecture using Virtual Routers,” July 2002, available at the Internet Engineering Task Force web site) or VPNs based on RFC 2547bis (often referred to as BGP/MLPS-based VPNs) (see Eric Rosen et al., “BGP/MPLS VPNs” available at the Internet Engineering Task Force web site). A VR and 2547 are only capable of IP. 2547 cannot support either MPLS or GMPLS over its networks. A VR does not implement in general a VPxC type switching and control plane.

It would be desirable to provide a GVR which combines the functionality of a VR and a VPxC.

It would also be desirable to provide a GVR that can be used to provide layer-3 services, as well as layer-1 services such as optical/TDM VPNs.

The GVR should be able to run routing protocols such as OSPF, RIP and BGP-4, and the GVR should support GMPLS.

When instantiated on a network-level, a GVR should be able to implement a VPN auto-discovery mechanism. Instantiation of the GVR on a single or multiple physical network nodes should be possible.

It would be desirable if the GVR could be logically/physically interconnected to build virtual private, routed switched networks.

Possible interfaces for the GVR should include both packet and optical/TDM interfaces, and the interfaces should be GMPLS-based, thus inheriting all GMPLS link constructs such as link bundling, unnumbered and numbered, to name a few.

The GVR should be a building block for a carrier wishing to sell a complete virtual network.

In view of the foregoing, it would be desirable to provide a generalized virtual router which overcomes the above-described inadequacies and shortcomings.


An object of the present invention is to provide an improved virtual router that combines layer-3, layer-2 and layer-1 routing and switching functionalities.

According to a first aspect of the present invention, there is disclosed a routing and switching apparatus that includes a switching fabric and a matrix of switching and routing elements. At least some of the elements are interconnected by the switching fabric. A router control provides control for the switching fabric. The apparatus has both cross-connect and routing functionality.

According to one embodiment, the apparatus can support GMPLS and it can also provide layer-3 VPN services.

According to another aspect of the invention, there is disclosed a fabric card for use in a routing and switching apparatus. The fabric card includes a circuit board, a switching fabric, and a matrix of switching and routing elements attached to the circuit board. At least some of the elements are interconnected by the switching fabric.

In a related embodiment, a CLOS architecture is employed, and the fabric card further includes a fabric control processor attached to the circuit board.

According to yet another aspect of the invention, there is disclosed a method for operating a router including the steps of:

(1) using a primary router to direct an electrical signal to a virtual router that runs GMPLS; and

(2) using the virtual router to perform virtual router functions.

In a related embodiment, the virtual router supports a combination of at least two of layer-2 switching Ethernet, layer-2 switching MPLS, and layer-3 forwarding via a network processor.

Further features and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings.


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