Patent Publication Number: US-2009232150-A1

Title: Service edge platform architecture for a multi-service access network

Description:
This application claims the benefit of U.S. provisional patent application Ser. No. 60/605,299, filed Aug. 27, 2004, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to multi-service access networks and more particularly to a service edge node for a multi-service access network. 
     BACKGROUND OF THE INVENTION 
     The primary function of a multi-service access (MSA) network is to provide packet transport up to a service edge node. In today&#39;s network, the transport function is typically time-division multiplexing (TDM) or circuit-switching in nature (ex. DS0, DS1, OC3). As Metro transport networks evolve to more efficiently carry packet and circuit traffic, two approaches have developed: a circuit efficiency approach based on Generic Framing Protocol (GFP), Virtual Concatenation (VCAT), or Link Capacity Adjustment (LCAS) and a packet efficiency approach using Internet Protocol (IP) or Multiprotocol Label Switching (MPLS) or Ethernet. Of these two approaches, the packet efficiency approach is viewed as being more efficient while enabling new transport services and is deemed to become the normalized technology of the future. 
     A key component of an MSA network is a service edge node. A typical platform architecture of a service edge node includes line, service, fabric, and control functions. Each of these functions is typically supported on a single physical card. In some cases, two or more of these functions are combined into a single physical card. Further, a typical service edge node platform architecture has a 1:1 relationship between line cards and service cards. However, using a single service card to process packets corresponding to numerous logical channels (ex. Synchronous Transport Signal (STS) or Virtual Local Area Network (VLAN) channels) and/or numerous traffic types (ex. public IP, private IP, Layer 2 Virtual Private Network (VPN), and Layer 3 VPN) limits the efficiency of the service edge node and thus the MSA network. 
     Accordingly, there remains a need for a more efficient service edge node. 
     SUMMARY OF THE INVENTION 
     The present invention provides a service edge node for a multi-service access (MSA) network. In general, the service edge node includes a line card, numerous service cards, a control system, and switching fabric. The line card receives packets from an access network and removes framing information from the packets to provide raw packets. For each of the packets, the raw packet from the line card is directed to one of the service cards. In one embodiment, each of the service cards is dedicated to a particular logical channel, and the line card is configured to direct the packets based on the logical channels. In another embodiment, each of the service cards is dedicated to a particular traffic type, and the line card directs the raw packets to the service cards based on a pre-configured table from the control system defining the traffic type of each of the service cards. The service cards process the raw packets based on routing information from the control system to provide processed packets and communicate the processed packets to the switching fabric for transmission over a core packet network. 
     In one embodiment, the service edge node includes a first line card coupled to a first set of service cards and a second line card coupled to a second set of service cards. The first line card receives packets from an access circuit-switching network and removes framing information from the packets to provide raw packets. For each of the packets, the first line card directs the raw packet to one of the first set of service cards. In one embodiment, each of the first set of service cards is dedicated to a particular logical channel, and the line card directs the raw packets based on the logical channels. In another embodiment, each of the first set of service cards is dedicated to a particular traffic type, and the line card directs the raw packets based on traffic type. The second line card receives packets from an access packet network and removes framing information from the packets to provide raw packets. For each of the packets, the second line card directs the raw packet to one of the second set of service cards. In one embodiment, each of the second set of service cards is dedicated to a particular logical channel, and the second line card directs the raw packets based on the logical channels. In another embodiment, each of the second set of service cards is dedicated to a particular traffic type, and the second line card directs the raw packets based on traffic type. The first and second set of service cards process the raw packets based on routing information from the control system to provide processed packets and communicate the processed packets to the switching fabric for transmission over a core packet network. 
     Similarly, in another embodiment, the service edge node includes the first line card and the second line card each coupled to a common set of service cards. 
     Those skilled in the art will appreciate the scope of the present invention and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the invention, and together with the description serve to explain the principles of the invention. 
         FIG. 1  illustrates a multi-service access network including a service edge node having a line card associated with numerous service cards according to one embodiment of the present invention; 
         FIG. 2  illustrates a multi-service access network including a service edge node having line cards each associated with a set of service cards according to another embodiment of the present invention; 
         FIG. 3  is a more detailed illustration of the line cards of  FIGS. 1 and 2  according to one embodiment of the present invention; 
         FIG. 4  is a more detailed illustration of the service cards of  FIGS. 1 and 2  according to one embodiment of the present invention; 
         FIG. 5  is a more detailed illustration of the control system of  FIGS. 1 and 2  according to one embodiment of the present invention; 
         FIG. 6  illustrates a multi-service access network including a service edge node and more particularly provides a more detailed block diagram of the control system of the service edge node according to one embodiment of the present invention; and 
         FIG. 7  is a more detailed illustration of an exemplary embodiment of the subsystems of the control system of  FIG. 6  according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention and illustrate the best mode of practicing the invention. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the invention and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure. 
       FIG. 1  illustrates a multi-service access network  10  according to one embodiment of the present invention. As illustrated, the multi-service access network  10  includes access edge nodes  12 A and  12 B, an access circuit-switching network  14 A, an access packet network  14 B, a service edge node  16 , and a core packet network  18 . As discussed below in detail, the focus of the present invention lies in the architecture of the service edge node  16 . In general, the multi-service access network  10  provides an interface to numerous disparate networks  20 A- 20 G. The networks  20 A- 20 G are exemplary. Various types of networks that may be connected to the core packet network  18  via the multi-service access network  10  of the present invention will be apparent to one of ordinary skill in the art upon reading this disclosure. 
     The access edge nodes  12 A,  12 B, the access circuit-switching network  14 A, and the access packet network  14 B, respectively, form access networks for coupling the networks  20 A- 20 G to the service edge node  16 . As an example, the access circuit-switching network  14 A may be a Generic Framing Protocol (GFP), a Virtual Concatenation (VCAT), or a Link Capacity Adjustment (LCAS) network, and the access packet network  14 B may be an Ethernet network. In addition, the access packet network  14 B may also include an Internet Protocol (IP), Multiprotocol Label Switching (MPLS), and/or Pseudo-Wire (PW) overlay. 
     According to one embodiment of the present invention, the service edge node  16  includes one or more line cards each associated with numerous service cards. More particularly, a first line card  22  is associated with N service cards  24 . The first line card  22  may be coupled to the service cards  24  via a high-speed backplane such as a 2.5 Gigabit, 10 Gigabit, or 20 Gigabit backplane. It should be noted that other types of physical interconnects between the first line card  22  and the service cards  24  will be apparent to one of ordinary skill in the art upon reading this disclosure. In operation, the first line card  22  receives packets from the access circuit-switching network  14 A, removes frame information from the packets, and passes raw packets including only a data portion of the packets to the service cards  24 . As an example, the packets may be IP packets, packets associated with a frame relay connection, or packets associated with an Asynchronous Transfer Mode (ATM) or MPLS connection. In an exemplary embodiment, the packets received by the first line card  22  may be received at optical carrier (OC) levels such as OC48 and OC192 and/or may be transmitted to the first line card  22  as 1 Gigabit-Ethernet (GE) packets or 10 GE packets. 
     After the frame information is removed from the packets, each of the raw packets is directed to a particular one of the service cards  24 . In one embodiment, the first line card  22  is configured to direct raw packets to the service cards  24  based on logical channels such as, but not limited to, VLAN and STS channels. Thus, all packets associated with a particular logical channel are directed to the service card  24  dedicated to that logical channel. In another embodiment, the raw packets are directed to the service cards  24  based on traffic types such as, but not limited to, public IP, private IP, Layer 2 VPN, and Layer 3 VPN. For this embodiment, the first line card  22  examines the packet to access packet information identifying the traffic type of the packet. Then, based on the packet information identifying the traffic type of the packet and a pre-configured table provided by a control system  26  which defines the traffic type handled by each of the service cards, the first line card  22  determines the service card  24  to which to direct the raw packet. 
     The service cards  24  process the raw packets from the first line card  22  based on routing information from the control system  26 . Alternatively, the routing information may be cached locally on the service cards  24 . In one embodiment, the service cards  24  perform Layer 2 and/or Layer 3 processing in preparation for transmission of the raw packets over the core packet network  18 . Packet processing at the service cards  24  may include classification, filtering, conditioning, forwarding, queuing, scheduling, policing, remapping, and encapsulation. The processed packets are communicated to the core packet network  18  via switching fabric  28 , which is also controlled by the control system  26 , service card  30 , and line card  32 . 
     The service card  30  and line card  32  operate to logically and physically connect the switching fabric  28  to the core packet network  18 . For example, the service card  30  and line card  32  operate as an interface to the core packet network  18  and may operate to communicate with the core packet network  18  at optical carrier levels such as OC-48 and OC-192. Functionally, the service card  30  operates similarly to the service cards  24 . More specifically, because the output packets from the service cards  24  are each to be directed though the single line card  32 , the service card  30  operates to provide such functions as queuing, traffic management, encapsulation, and mapping. The line card  32  operates similarly to the first line card  22  and provides a physical interface to the core packet network  18 . Note, however, that the service card  30  and the line card  32  have greater capacity than the line card  22  and service cards  24 . 
     Like the first line card  22 , a second line card  34  is associated with M service cards  36 . The numbers N and M of service cards  24  and  36 , respectively, depend on the particular implementation and may or may not be the same. In one embodiment, the second line card  34  is coupled to the service cards  36  via a high-speed backplane such as a 2.5 Gigabit, 10 Gigabit, or 20 Gigabit backplane. It should be noted that other types of physical interconnects between the second line card  34  and the service cards  36  will be apparent to one of ordinary skill in the art upon reading this disclosure. In operation, the second line card  34  receives packets from the access packet network  14 B, removes frame information from the packets, and passes raw packets including only a data portion of the packets to the service cards  36 . As an example, the packets may be IP packets, packets associated with a frame relay connection, or packets associated with an ATM connection. In an exemplary embodiment, the packets received by the second line card  34  may be at optical carrier (OC) levels such as OC48 and OC192 and/or may be transmitted to the second line card  34  as 1 Gigabit-Ethernet (GE) packets or 10 GE packets. 
     After the frame information is removed from the packets, each of the raw packets is directed to a particular one of the service cards  36 . In one embodiment, the second line card  34  is configured to direct raw packets to the service cards  36  based on logical channels such as, but not limited to, VLAN and STS channels. Thus, all packets associated with a particular logical channel are directed to the service card  36  dedicated to that logical channel. In another embodiment, the raw packets are directed to the service cards  36  based on traffic types such as, but not limited to, public IP, private IP, Layer 2 VPN, and Layer 3 VPN. For this embodiment, the second line card  34  examines the packet to access packet information identifying the traffic type of the packet. Then, based on the packet information identifying the traffic type of the packet and a pre-configured table provided by the control system  26  which defines the traffic type handled by each of the service cards, the second line card  34  determines the service card  36  to which to direct the raw packet. 
     The service cards  36  process the raw packets from the second line card  34  based on routing information from the control system  26 . In one embodiment, the service cards  36  perform Layer 2 and/or Layer 3 processing in preparation for transmission of the raw packets over the core packet network  18 . The processed packets are communicated to the core packet network  18  via the switching fabric  28 , which is controlled by the control system  26 , the service card  30 , and the line card  32 . 
     In one embodiment, the core packet network  18  is an Internet Protocol (IP)/Multiprotocol Label Switching (MPLS) network. Further, as an example, the processed packets may be transmitted from the service edge node  16  to the core packet network  18  as OC48 packets, OC1  92  packets, 1 GE packets, or 10 GE packets. 
     It should be noted that the embodiment of  FIG. 1  illustrates both the access circuit switching network  14 A and the access packet network  14 B. As such, the service edge node  16  includes the first and second line cards  22  and  34 , respectively. However, the multi-service access network  10  may include the access circuit switching network  14 A but not the access packet network  14 B. As such, the service edge node  16  would need only the first line card  22 , service cards  24 , control system  26 , and switching fabric  28 , and not the second line card  34  and the service cards  36 . In yet another embodiment, the multi-service access network  10  includes the access packet network  14 B but not the access circuit switching network  14 A. As such, the service edge node  16  would need only the second line card  34 , service cards  36 , switching fabric  28 , and control system  26 , and not the first line card  22  and the service cards  24 . 
       FIG. 2  illustrates another embodiment of the service edge node  16  of the present invention. This embodiment is similar to that of  FIG. 1 . However, the first line cards  22  and the second line cards  34  share a single set of service cards  38 . More particularly, the first line card  22  and the second line card  34  are each associated with the service cards  38 . The number of service cards  38  depends on the particular implementation. In one embodiment, the first and second-line cards  22 ,  34  are coupled to the service cards  38  via a high-speed backplane such as a 2.5 Gigabit, 10 Gigabit, or 20 Gigabit backplane. It should be noted that other types of physical interconnects between the line cards  22 ,  34  and the service cards  38  will be apparent to one of ordinary skill in the art upon reading this disclosure. 
     As discussed above, the first and second line cards  22 ,  34  operate to remove frame information from received packets and direct the raw packets to the service cards  38  based on logical channels or traffic types. For example, in one embodiment, each of the service cards  38  corresponds to a particular channel, such as a particular STS or VLAN channel. Accordingly, each of the first and second line cards  22 ,  34  operates to direct each of the raw packets to one of the service cards  38  dedicated to the particular channel of the raw packet. In another embodiment, each of the service cards  38  is dedicated for a particular traffic type. For example, there may be four service cards  38  with a first of the service cards  38  dedicated to public IP traffic, a second of the service cards  38  dedicated to private IP traffic, a third of the service cards  38  dedicated to Layer 2 VPN traffic, and a fourth of the service cards  38  dedicated to Layer 3 VPN traffic. Accordingly, the first and second line cards  22 ,  34  operate to direct the raw packets to the service cards  38  based on the traffic type of the packet. After processing by one of the service cards  38 , each of the processed packets is transmitted to the core packet network  18  through the switching fabric  28 , service card  30 , and line card  32 . 
       FIG. 3  illustrates an exemplary embodiment of the first and second line cards  22  and  34 . For this discussion, the line card illustrated in  FIG. 3  will be referred to as the line card  22 . However, this discussion equally applies to each of the first and second line cards  22  and  34 . In general, the line card  22  includes a controller  40  associated with memory  42  containing software  44 . The line card  22  also includes a network interface  46  enabling communication with the circuit switching access network  14 A and a service card interface  48  enabling communication with the service cards  24  or  38 . In operation, the controller  40  operates to run the software  44 , wherein the software  44  provides the functionality of the line card  22  described herein. 
       FIG. 4  illustrates an exemplary embodiment of the service cards  24 ,  36 , and  38 . For this discussion, the service card illustrated in  FIG. 4  will be referred to as the service card  24 . However, this discussion equally applies to each of the service cards  24 ,  36 , and  38 . In general, the service card  24  includes a controller  50  associated with memory  52  containing software  54 . The service card  24  also includes a line card interface  56  enabling communication with the line card  22  and/or  34  and a switching fabric interface  58  enabling communication with the switching fabric  28 . In operation, the controller  50  operates to run the software  54 , wherein the software  54  provides the functionality of the service card  24  described herein. 
       FIG. 5  illustrates an exemplary embodiment of the control system  26  of  FIGS. 1 and 2 . In general, the control system  26  includes a controller  60  associated with memory  62  containing software  64 . The control system  26  also includes one or more communications interfaces  66  enabling communication with the line cards  22 ,  34 ; the service cards  24 ,  36 ,  38 ; and the switching fabric  28 . In operation, the controller  60  operates to run the software  64 , wherein the software  64  provides the functionality of the control system  26  described herein. 
       FIG. 6  illustrates the MSA network  10  of  FIG. 1  including another exemplary embodiment of the control system  26 . It should be noted that the following discussion of the control system  26  equally applies to the embodiment of  FIG. 2 . As illustrated, the control system  26  may include numerous subsystems  68 A- 68 C, generally referred to as subsystem  68 . As illustrated in  FIG. 7 , each of the subsystems  68  includes a controller  70  associated with memory  72  containing software  74 . The software  74  may provide routing, signaling, or Layer 2 control functions. Each of the subsystems  68  also includes one or more communication interfaces  76  enabling communication with the first and second line cards  22 ,  34 ; the service cards  24 ,  36 ; and the switching fabric  28 . Referring back to  FIG. 6 , each of the subsystems  68  is assigned to perform a specific application function and is associated with one or more of the service cards  24 ,  36 . For example, one of the subsystems  68  runs the software  74 , wherein the software  74  controls the controller  70  such that the subsystem  68  performs control functions for public IP traffic and, as such, is configured to be associated with ones of the service cards  24 ,  36  that are dedicated to public IP traffic. Further, in operation, the one of the subsystems  68  performing control functions for public IP traffic operates to handle a routing protocol of the public IP traffic such as the Open Shortest Path First (OSPF) routing protocol, perform routing computations to derive a forwarding table, and communicate the forwarding table to the ones of the associated ones of the service cards  24 ,  36 . In a similar fashion, one of the subsystems  68  may be associated with ones of the service cards  24 ,  36  dedicated to private IP traffic, one of the subsystems  68  may be associated with ones of the service cards  24 ,  36  dedicated to Layer 2 VPN, and one of the subsystems  68  may be associated with ones of the service cards  24 ,  36  dedicated to Layer 3 VPN. 
     The service edge node  16  of the present invention provides substantial opportunity for variation without departing from the scope of the present invention. For example, in one embodiment, the first and second line cards  22 ,  34  direct packets to the service cards  24 ,  36 , or  38  based on traffic type. As described above, in this embodiment, one of the service cards  24 ,  36 , or  38  may be dedicated to public IP traffic. However, it should be noted that there may be numerous service cards  24 ,  36 , or  38  dedicated to public IP traffic with each the service cards dedicated to public IP being more specifically dedicated to a specific range of public IP addresses. 
     Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present invention. All such improvements and modifications are considered within the scope of the concepts disclosed herein.