Patent Publication Number: US-8526435-B2

Title: Packet node for applying service path routing at the MAC layer

Description:
TECHNICAL FIELD 
     The present invention relates generally to the field of communications and, more specifically, to a packet node for applying service path routing at the media access control (MAC) layer. 
     BACKGROUND 
     Recently, a concept of Service Path Routing (SPR) has been introduced in internet protocol (IP) nodes. According to SPR, packets traversing an IP node are routed through a pre-defined set of hardware cards, also called blades. Each packet entering the IP node is classified and assigned to a service path defining which blades of the IP node are to be visited by the packet and treated thereat. 
     Solutions based on SPR propose a special forwarding engine (FE) to classify packets and add a special indication to a packet, to determine a service to which this packet belongs. The FE needs to be invoked after each service blade has performed its task in order to determine if another service blade needs to further process the packet. Hence, the FE is generally present on each service blade, or shared by several service blades. 
     Current solutions require FEs at multiple components (e.g. several cards or blades) of an IP node. Because FEs are complex and expensive, this requirement has so far prevented a wide adoption of the SPR concept. In addition, while an instance of the FE may in principle be shared by multiple blades, presence of an FE instance on every service blade is required for maximum performance. This latter requirement may only come at the expense of increased costs of the service blades. 
     SUMMARY 
     It is therefore a broad object of this invention to provide a node that reuses Ethernet switching capabilities. 
     A first aspect of the present invention is directed to a packet node. The packet node comprises several cards. A first card acts as an ingress card for receiving a packet on an input port. The ingress card classifies the packet according to a service provided by the packet node. The ingress card then adds to the packet a first virtual media access control (VMAC) address selected according to the service. The ingress card then forwards the packet to a layer two switch. The layer two switch receives the packet and forwards it to a first service component based on the first VMAC address. The first service component receives and processes the packet. It replaces the first VMAC address of the packet with a second VMAC address and forwards the packet to the layer two switch. The layer two switch receives again the packet and, based on the second VMAC address, forwards the packet to a second service component or to an egress card. The egress card receives the packet, removes the second VMAC address, and forwards the packet on an output port of the egress card. 
     A second aspect of the present invention is directed to an embodiment of the packet node that further comprises a controller. The controller receives, upon startup of the packet node, registrations from a plurality of service components. Each of the registrations is for a distinct service provided by the packet node. The controller assigns a corresponding VMAC address to each service. A plurality of VMAC addresses is thereby mapped on the plurality of service components. The controller stores mappings between the plurality of VMAC addresses and the plurality of service components in a table of the layer two switch. 
     A third aspect of the present invention is directed to a method of switching a packet in a packet node. The method comprises a first step of receiving the packet at a layer two switch of the packet node, from an ingress card of the packet node. The packet comprises a first VMAC address selected according to a service provided by the packet node. The layer two switch forwards the packet to a first service component of the packet node, the first service component being selected by the layer two switch based on the first VMAC address. The layer two switch receives again the packet from the first service component, the packet now comprising a second VMAC address. On the basis of the second VMAC address, the layer two switch forwards the packet either to a second service component of the packet node or to an egress card of the packet node. 
     A fourth aspect of the present invention is directed to a method of configuring a packet node. A controller of the packet node receives registrations from a plurality of service components of the packet node. The registrations are for each of a plurality of services provided by the packet node. The controller assigns a corresponding VMAC address to each of the plurality of services, a plurality of VMAC addresses being mapped on the plurality of service components. Mappings between the plurality of VMAC addresses and the plurality of service components are stored in a layer two switch of the packet node. The VMAC addresses are for switching, by the layer two switch, packets received at the packet node, switching being made on the basis of services provided to the packets by the packet node. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed understanding of the invention, for further objects and advantages thereof, reference can now be made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  shows a functional diagram of an exemplary packet node, as per some teachings of the present invention; 
         FIG. 2  shows a physical layout of an exemplary packet node, as per some teachings of the present invention; 
         FIG. 3  shows a flow chart depicting exemplary steps of a switching method of the present invention; and 
         FIG. 4  shows a flow chart depicting exemplary steps of a configuration method of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The innovative teachings of the present invention will be described with particular reference to various exemplary uses and aspects of the preferred embodiment. However, it should be understood that this embodiment provides only a few examples of the many advantageous uses of the innovative teachings of the invention. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed aspects of the present invention. Moreover, some statements may apply to some inventive features but not to others. In the description of the figures, like numerals represent like elements of the invention. 
     The present invention provides a node for treating data packets. A data packet arrives at the node and is classified by an ingress card. The principles underlying the packet classification are essentially conventional; however a result of this classification is not conventional. Building on the presence of an Ethernet-capable switch in a backplane of current packet nodes, the present invention assigns a virtual media access control (VMAC) address to the packet, as a result of the packet classification. The VMAC address thus acts as a service identifier for a service applied to the packet by the packet node. While the VMAC address has a generic MAC address format and can thus be handled by a conventional Ethernet layer two switch, the VMAC does not relate to any physical port. The VMAC address is used solely within the packet node and thus does not require to be coordinated with MAC addresses used any other network element in communication with the packet node. The packet, enhanced by the addition of the VMAC address, is directed to a service component by the layer two switch. The service component applies a treatment to the packet, overwrites the VMAC address with a new VMAC address indicative of a result of the treatment, and returns the packet to the layer two switch. Based on the new VMAC address, the layer two switch may forward the packet to another service component that performs similar actions. Eventually, based on a final VMAC address inserted in the packet by a last service component, the layer two switch forwards the packet to an egress card that removes the VMAC address and forwards the packet to an intended destination, beyond the packet node. It may be observed that while the layer two switch directs the packet based on VMAC addresses that reflect services provided by the packet node, the layer two switch is in fact unaware of any notion of those services. The use of virtual addresses provide the possibility of hosting more than one service on a given service component card and the possibility to relocate a given service from one service component card to another, for example upon component failure. 
     In the context of the present invention, a packet node may comprise a router, a gateway, a server, and the like. The packet node may receive and route packets according to various protocols including the internet protocol (IP), the multiprotocol label switching (MPLS), Ethernet, and the like. Non-limiting examples of services that various embodiments of the packet node may provide include deep packet inspection, charging, filtering, audio transcoding, video transcoding, encryption, decryption, tunneling, detunneling, proxying, load distribution, lawful interception, and the like. 
     Reference is now made to the Drawings, in which  FIG. 1  shows a functional diagram of an exemplary packet node, as per some teachings of the present invention. The packet node  100  as shown comprises a layer two switch  110 , an ingress card  120 , an egress card  130 , a controller  140  and a service component card  150 . 
     The controller  140  may be any commercially available, general purpose processor, or may be specifically designed for operation in the packet node  100 . The controller  140  may be operable to execute processes related to the present invention in addition to numerous other processes. 
     Each of the ingress card  120  and the egress card  130  may support various types of interface and protocols. The packet node  100  may be connected toward a plurality of routers, gateways, servers and clients; means for connecting the packet node  100  toward other network elements may vary as, for example, connection toward one client might be on an Ethernet link while connection toward a gateway might be on an asynchronous transfer mode (ATM) link. Therefore each of the cards  120  and  130  may comprise a plurality of devices for connecting on a plurality of links of different types. Generic cards  120  and  130  are illustrated for ease of presentation of the present invention. Communication between the packet node  100  and other network elements, such as routers, may be bidirectional. As such, in some embodiments, some interface cards of the packet node  100  may at once act as ingress cards and as egress cards. For example, the ingress card  120  may receive a first packet from a first router, the first packet being later forwarded to a second router via the egress card  130 . A second packet may arrive at the packet node  100 , being sent from the second router, arriving at card  130  (now acting as an ingress card for the second packet), the second packet eventually being forwarded to the first router via card  120  (now acting as an egress card for the second packet). In some cases, a packet may be received at one of the cards  120  or  130  and, after processing, may be forwarded beyond the packet node  100  via the same card. Those skilled in the art will appreciate that the present description of  FIG. 1  makes mentions of the ingress card  120  and of the egress card  130  as distinct entities for the purposes of illustrating some of the features of the present invention, without limiting its scope. 
     In some embodiments, some of the components  110 - 150  of the packet node  100  may be duplicated. For example, the packet node  100  may comprise several distinct service component cards, or a few separate layer two switches. A given service component card may comprise several service components while another service component card may hold a single other service component. In yet some other embodiments, one or more service components may be implemented on ingress cards or on egress cards, or both. A given ingress card  120  or a given egress card  130  may also double as a service component card  150 . As such, while the present description illustrates service component cards, ingress cards and egress cards as distinct cards, this separation of features on distinct cards is made in order to clearly distinguish the various features of the packet node  100 . It should be understood that variations in the hardware configuration of the packet node  100  may exist while still falling within the scope of the present invention as claimed. Elements of the packet node  100  are shown as directly coupled in  FIG. 1 . In a practical embodiment, communication between the various components of the packet node  100  may take the form of, for example, electrical or optical signals. The simplified coupling is shown in order to more clearly illustrate communication paths. 
     The ingress card  120  comprises one or more input ports  122 , a classifier  124  and a MAC-in-MAC tunnel operator  126 . The egress card  130  may comprise similar elements, including output ports  132 , a classifier  134  and a MAC-in-MAC tunnel operator  136 . The layer two switch  110  comprises a switch agent  112 , and a mapping table  114 . The service component card  150  comprises one or more service components  150   a-c . A number of service components on a given service component card  150  may depend on various factors, including for example an amount of processing required in a given service component to fulfill its tasks or an expected amount of packet traffic arriving at the packet node requiring a given type of service. The service component card also comprises a service agent  154 . The service component card  150  is physically addressable via a MAC address  152 . The MAC address  152  is for use by the service component card  150  for communicating within the packet node  100 , and specifically with the controller  140 , at the time of a registration process of the services, said process being described hereinbelow. 
     Configuration of the packet node  100  is made, for example, at system start or restart of the packet node  100 . The controller  140  receives registrations from each of the service components  150   a-c , the registrations being initiated at the service component cards  150  by the service agent  154 . A registration may also be received at the controller  140  because a new service is introduced in one of the service components  150   a-c , or moved between service component cards  150 . Deregistration, or an equivalent process, may be used when a service is removed from a service component card  150 . If there are more than one layer two switches  110 , they may also send registrations to the controller  140 . The controller  140  assigns a VMAC address to each one of the service components  150   a-c . Because these are virtual addresses, they do not relate to any physical port or entity of the packet node  100 . However, because these addresses have the well-known format of MAC addresses, they can be used for switching by the layer two switch (or switches)  110 . The controller  140  stores mappings of the VMAC addresses and of the service components  150   a-c  in the mapping table  114  of the layer two switch  110 . The mappings may be realized as relations between the VMAC addresses and internal ports (not shown) of the layer two switch  110 , the switch ports corresponding to connections on the service component card  150 . The mappings may further comprise virtual local area network (VLAN) identifications. A given service component  150   a-c  may support more than one service, possibly in combination with other service components  150   a-c  and may thus be part of more than one VLAN. The controller also stores the mappings in the classifier  124  of the ingress card  120  (the mappings may also be stored in the egress card  130 , which also has a classifier  134  because the egress card  130  may act as an ingress card for some traffic). In some embodiments, the classifier  124  only needs to store the mappings for specific service components  150   a-c  that may first treat a packet incoming at the packet node  100 . In fact, while some of the service components  150   a-c  may be for use after some processing of the packet has already taken place in other service components  150   a-c , it is in practice simpler to store all mappings in the classifier  124  rather than to make a selection of the mappings. In embodiments having more than one layer two switch  110 , because each layer two switch  110  has registered to the controller  140 , the controller  140  stores the mappings in every mapping table  114 . It is to be noted that while the mappings reflect services offered by the packet node, the mapping table simply contains, from a practical standpoint, mappings between internal ports on the layer two switch  110 , the switch ports being connected to components of the packet node, and VMAC addresses. The layer two switch (or switches)  110  is in fact unaware of any notion of the services provided by the packet node. Finally, the controller  140  provides information about the VMAC addresses to the ingress card  120  and to the service agent  154 . The ingress card  120  stores the VMAC information in the classifier  124  (the egress card  130  does not necessarily need the VMAC information, but may store it in its classifier  134 , accounting for the fact that the egress card  130  may act as an ingress card for packets arriving one of its ports  132 ). While the packet node  100  may comprise a plurality of service component cards  150 , the service agent  154  of each service component card  150  stores a complete list of VMAC addresses assigned to the service components  150   a-c  located on all service component cards  150 . 
     In operation, the packet node  100  receives a packet at an input port  122  of the ingress card  120 . The packet is classified by the classifier  124  according to well-known methods including, but not limited to, basing the classification on a port number of the input port  122 , on a port number, protocol, source address or destination address present in a header of the packet, on a packet size, on matching of various patterns with the header or with a payload content of the packet, on an inter-arrival rate of the packet relative of a previous packet, and the like. Based on a result of the classification, the classifier  124  selects one of the stored VMAC addresses, thereby selecting one of the service components  150   a-c  for providing a service to the packet. The classifier  124  may also further assign a VLAN identification to the packet. It should be observed that while the classification and the selection of the VMAC address, possibly adding the VLAN identification, effectively leads to the selection of a given service component, the classifier  124  may remain unaware of any relation between the given service component on one hand, and the selected VMAC address and VLAN identification on the other hand. The classifier  124  only needs to be aware of a relationship between a result of the packet classification and the VMAC address and VLAN identification. The MAC-in-MAC tunnel operator  126  encapsulates the packet by adding the selected VMAC address and optional VLAN identification. The ingress card  120  then places the encapsulated packet on the layer two switch  110 . The layer two switch  110 , using the mappings between VMAC addresses, the optional VLAN identification and service components stored in the mapping table  114 , redirects the encapsulated packet to the intended service component  150   a-c , for example service component B  150   b . The service component B  150   b  decapsulates the packet, processes the packet according to its content and according to features of the service component B  150   b , and determines whether the packet requires further processing within the packet node  100 . If no more processing is required, the service component B  150   b  obtains from the service agent  154  a VMAC address indicative that the processing is complete. If further processing is required, based on a nature of that further processing, the service component B  150   b  obtains from the service agent  154  a VMAC address designating another service component for continued processing. It is to be noted that this last service component may reside on any service component card  150  of the packet node  100 . In either case, the service component B  150   b  encapsulates the packet with the VMAC address obtained from the service agent  154 . The service component B  150   b  places the encapsulated packet on the layer two switch  110 . The layer two switch  110  redirects the packet using its currently assigned VMAC address. A VMAC address having been selected by the service component B  150   b  on the basis that no more processing is required makes the layer two switch  110  forward the packet to the egress card  130 . One possible manner of ensuring selection of the egress card  130  at the end of processing is to simply consider outputting of the packet by the egress card  130  as another one of the services provided by the packet node  100 . As such, the egress card  130  may register this “outputting service” to the controller  140 , in the same manner as any of the service components  150   a-c . In the egress card  130 , the MAC-in-MAC tunnel operator  136  decapsulates the packet by removing the VMAC address and the optional VLAN identification. The packet is forwarded to its intended destination, as is well-known in the art, via the output port  132 . If the VMAC address selected by the service component B  150   b  suggests that more processing of the packet is required, the selected VMAC address makes the layer two switch  110  forward the packet to the designated service components. 
     From the above, those skilled in the art will recognize that, for some services, in some embodiments, a first and a second service components may each support a part of a given service provided by the packet node. A final VMAC address designating the egress card is determined by a last one of the service components supporting the service provided by the packet node, when it has done its own processing of the packet. Of course, a second VMAC address determined by a first service component designates the egress card when the first service component completely supports a particular service provided to a given packet by the packet node. The first, second and any other VMAC addresses are part of a service path that the packet follows throughout the packet node. Assigning a same VMAC address to more than one service results in bicasting or multicasting of the packet to more than one service components. This may be useful for some special services such as charging, lawful intercept or transcoding. For some services, in some embodiments of the packet node  100 , a received packet is not forwarded beyond the packet node  100 . A last service component treating the received packet does not return it to the layer two switch  110  at the end of processing. This may be the case, for example, for some charging or logging services. This may of course be the case when it is found that the packet is malevolent and comprises a virus, spam, or similar content. 
     A failure of one of the plurality of service components may be detected, for example by an alternate service component or by the controller  140 . As this happens, the alternate service component may take over from the failed service component and provide the same or similar features and processing. The alternate service component sends an updated registration to the controller  140 , which in turns updates a VMAC address mapping for a service now supported by the alternate service component. The same VMAC address initially allocated to the failed service component may be mapped to the alternate service component. The controller  140  stores the updated mapping on the mapping table  114  of the layer two switch  110 . Consequently, as a new packet arrives at the ingress card  120 , if the ingress card  120  selects the VMAC address designating the failed service component, the layer two switch  110  is capable of directing the packet to the alternate service component, using the updated mapping. 
       FIG. 2  shows a physical layout of an exemplary packet node, as per some teachings of the present invention. A packet node  200  comprises a backplane  210 , and several cards, also called blades. These include an ingress card  220 , an egress card  230 , a controller card  240 , and one or more service component cards  250   a-b . The packet node  200  may comprise other elements (not shown), as is well known in the art. A layer two switch is present, but not explicitly shown, because it is integral to the backplane  210 . The cards  220 - 250  are connected to the backplane  210  by use of connectors  212  of the backplane  210 . The connectors  212  may support any type of connection, including for example electrical or optical connections. The ingress card  220  comprises one or more input ports  222  and the egress card  230  comprises one or more output ports  232 . As in the case of the ingress and egress cards of  FIG. 1 , the ingress card  220  and the egress card  230  may, in some embodiments, share similar features and functionalities and thereby interchangeably act as input for some traffic and output for some other traffic. The input ports  2220  and output ports  232  may support various types of physical interfaces as well as various protocols. 
     The packet node  200 , as shown in  FIG. 2  in its physical layout, embodies some or all of the features of the packet node  100  presented in relation with the description of  FIG. 1 . Service components are implemented on the one or more service component cards  250   a-b , each of the service component card  250   a-b  supporting one or more service components. In some embodiments, the controller and a given service component may be located on a same card. 
       FIG. 3  shows a flow chart depicting exemplary steps of a switching method of the present invention. A sequence  300  starts at step  310  when a packet is received at a layer two switch of a packet node, from an ingress card of the packet node. The packet comprises a first VMAC address selected according to a service provided by the packet node. The layer two switch forwards the packet, at step  320 , to a first service component of the packet node. The first service component is selected by the layer two switch based on the first VMAC address. The selection by the layer two switch may rely on a mapping table of the layer two switch, wherein mappings of a list of VMAC addresses with a list of corresponding service components are stored. The layer two switch receives again the packet, at step  330 , from the first service component. The packet now comprises a second VMAC address. The layer two switch considers the second VMAC address at step  340 . If the VMAC address suggests that the packet requires further treatment, based on the mappings, the layer two switch forwards the packet to a second service component of the packet node at step  350 . Otherwise, the treatment of the packet being completed, the layer two switch forwards the packet or to an egress card of the packet node at step  360 . 
       FIG. 4  shows a flow chart depicting exemplary steps of a configuration method of the present invention. A sequence  400  starts when a controller of a packet node receives registrations from a plurality of service components of the packet node. Each registration is for each of a plurality of services provided by the packet node. The controller assigns, at step  420 , a corresponding VMAC address to each of the plurality of services. The controller maps each of a plurality of VMAC addresses to a corresponding one of the plurality of service components. The controller stores mappings between the plurality of VMAC addresses and the plurality of service components in a layer two switch of the packet node, at step  430 . The layer two switch uses the VMAC addresses, at step  430 , to switch packets received at the packet node on the basis of services provided to the packets by the packet node. 
     Although several aspects of the preferred embodiment of the methods and of the packet node of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the teachings of the invention as set forth and defined by the following claims.