FIELD OF THE INVENTION 
   The invention relates generally to a mechanism, a system and a method involving packet inspection engines or entities that are in the path of a packet stream and provide packet inspection functions for various purposes. More particularly, the invention relates to a mechanism, system and a process involving packet inspection engines in which there is a requirement for redundancy in combination with a requirement of quick replacement of a failed inspection engine without the loss of information as to the processing state. 
   BACKGROUND OF THE INVENTION 
   Many complex solutions have been developed over time to provide processing redundancy. Many of these solutions rely on having either one system backing up several, or several systems backing up one system. Solutions which provide m for n redundancy often require complex configuration and coordination. In addition, for packet inspection services which require knowledge of subscriber state, additional protocol processing and operation is often required to recreate the subscriber state, often with concomitant delays in recovering operation. 
   VRRP or Virtual Router Redundancy Protocol is a protocol which allows several routers on a multiaccess link to utilize the same virtual IP address. VRRP is designed to eliminate the single point of failure inherent in the static default routed environment. The VRRP router controlling the IP address(es) associated with a virtual router is called the master, and forwards packets sent to these IP addresses. The master router is elected with the other routers acting as backups in case of the failure of the master router. Any of the virtual router&#39;s IP addresses on a LAN can then be used as the default first hop router by end-hosts. The advantage gained from using VRRP is a higher availability default path without requiring configuration of dynamic routing or router discovery protocols on every end-host. Using VRRP allows host systems to be configured manually or via Dynamic Host Configuration Protocol (DHCP) with a single default gateway, rather than running an active routing protocol. DHCP is the protocol for automating the configuration of computers that use Transmission Control Protocol/Internet Protocol (TCP/IP). VRRP provides a function similar to a Cisco Systems, Inc. proprietary protocol named Hot Standby Router Protocol (HSRP) and with a function similar to a Digital Equipment Corporation, Inc. proprietary protocol named IP Standby Protocol. VRRP provides only m backups (m redundancy) for each one primary unit. This m for 1 redundancy presents significant limitations as to redundancy possibilities and situations. VRRP also does not optimally utilize the redundant units. 
   SUMMARY OF THE INVENTION 
   The invention provides a mechanism, system and process for applications such as packet processing where it is important that solutions be highly redundant using an entity such as a node or other interface to provide a product to an IP service provider. The node works with the actual IP packet flow of subscribers. The invention allows for simple configuration and simple deployment of a full m for n redundancy mechanism with full subscriber state recovery without additional protocol participation. 
   According to the invention, a packet inspection engine system with m:n redundancy mechanism has n active application service engines inspecting packets from an actual Internet protocol (IP) packet flow of subscribers. Further, m redundant Application Service Engines (ASE or APE) are provided. Each of said n active ASEs multicast changes of subscriber state to each of the m redundant ASEs. Each of the m redundant ASEs maintains received changes of subscriber state as active ASE status data for each active ASE. A redundant or standby ASE is selectively activated when one of the n active ASEs fails with an activated formerly redundant ASE having all of the subscriber state information of the failed ASE. 
   The IP packet traffic is directed to the ASEs based on interface addresses that are known to neighbors that are advertised with Address Resolution Protocol (ARP) and tunnel termination points and address pools that are advertised in routing pools, or configured in other parts of the network to be tied to an interface address. When activated, the formerly redundant ASE advertises interface addresses and if necessary the routing advertisements that the failed ASE was advertising. The activated formerly redundant ASE is selectively activated by one of the ASEs acting as a master ASE. 
   The mechanism, method and system use one of the ASEs acting as a master. The master ASE is established by an election/re-election. Each ASE that detects that he can not reach the master starts participating in an election. All of the ASEs which can reach each other, and which cannot reach the current master, will conduct the election. The fact that one ASE cannot reach the master does not cause another ASE to start participating in the election. The election/re-election includes participation by all of the ASEs through exchanging messages among all of the ASEs. The master ASE sends regular hello messages to let other ASEs know that the master ASE is still alive. 
   The master ASEs may be established upon determining that none of the ASEs are operating as a master and then electing one of the ASEs as a master. This may be done by each ASE exchanging multicast or broadcast messages indicting a software revision and configuration revision and a commissioned IP address. The ASE with the most current software and configuration, and within that, with the lowest identity, becomes master ASE after examining the messages. 
   The master may be used to form a redundancy group of the active and redundant (standby) ASEs. The master determines for the redundancy group how many active ASEs are needed to support an operational configuration of the IP packet flow of subscribers based on a configuration of IP packet flow for subscribers. If there is an active ASE performing a determined configured function, the master may allow the function to continue to be performed. Otherwise, the master may assign other configured functions to available ASEs with ASEs not assigned a configuration serving as the redundant ASEs in the redundancy group. 
   The master may also be used for updating software to a new software revision or release for the active and redundant ASEs. A prefered update method and system includes first setting the software release data of the master ASE to the new software release (but not yet resetting the mater ASE to run the new release software). The master then may update the active ASEs and the standby ASEs to the new software. Subsequently, the master is reset with the new release. 
   According to another aspect of the invention, a method is provided for inspecting packets. Application Processing Engines (also referred to as ASEs) inspect an IP packet flow of subscribers. It is determined whether any of the ASEs is operating as a master and if not, one of the ASEs is elected. The master forms one or more redundancy group of the ASEs based on a configuration of IP packet flow for subscribers determining for the redundancy group how many active ASEs are needed to support an operational configuration of the IP packet flow of the subscribers. If there is already an active ASE performing a determined configured function, the master allows the function to continue to be performed by that active ASE and assigns other configured functions to available ASEs with ASEs not assigned a configuration serving as standby ASE in the redundancy group. The active ASEs multicast subscriber state data to each of the standby ASEs. The standby ASEs maintain received subscriber state data for each active ASE. A standby ASEs is activated when one of the active ASEs fails. The activated ASE may advertise the interfaces of the activated standby ASE and if necessary the routing advertisements that the failed ASE was advertising. 
   According to another aspect of the invention, a system and a method are provided for backed up processing. The method includes providing application processing engines (ASEs) for processing IP packets and determining if any of the ASEs is operating as a master and if not electing one of the ASEs as a master based on factors including the software release being used by the ASE. The method uses the master to assign some of the ASEs as active ASEs and some of the ASEs as standby ASEs. The software release version the active ASEs and the standby ASEs are running is updated by setting the software release data of the master ASE to the new software release, updating the active ASEs and standby ASEs to the new software and subsequently resetting the master with the new release. 
   The invention represents a significant improvement on the redundancy mechanisms used in the past including the redundancy features used in the system described in U.S. application Ser. No. 09/811,204 (the contents of which are hereby incorporated by reference) and related publication US-2002-0181476-A1 (the contents of which are hereby incorporated by reference). Systems that provide packet inspection can benefit from the mechanism, system and process of the invention for control applications and application processing engines, and even routers. This invention also represents a significant improvement over the state of the art in such redundancy, as represented, for example, by VRRP and Cisco Systems, Inc. proprietary protocol HSRP. 
   The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view showing a possible physical arrangement embodying the mechanism, system and process of the invention; 
       FIG. 2  is a schematic view showing a logical arrangement embodying the mechanism, system and process of the invention; 
       FIG. 3  is a schematic view showing a the application processing engines (ASEs) of the system with election of a master according to the invention; 
       FIG. 4A  is a schematic view showing an elected master sending hello messages to ASEs of various redundancy groups; 
       FIG. 4B  is a schematic view showing an elected master sending a newer software and/or configuration to ASEs of various redundancy groups; 
       FIG. 5A  is a schematic view showing redundancy groups and the assignment of ASEs to be active ASEs in one of the redundancy groups or to be standby ASEs in that redundancy group; 
       FIG. 5B  is a schematic view showing the redundancy group with ASEs sending multicast subscriber status messages to all non-active ASEs in the redundancy group; 
       FIG. 6  is a schematic view showing the redundancy group with a failed ASE and with a non-active ASE being activated; and 
       FIG. 7  is a schematic view showing the redundancy group with a new ASE (processor blade) getting the state information from the active ASEs of the redundancy group that the master ASE has assigned the new ASE to participate in. 
   


   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to the drawings in particular, the invention may be provided by a physical system arrangement as shown in  FIG. 1 . The system arrangement  10  is connected to a router or switching device  5 . The router  5  receives and sends packets to subscribers  7  ( FIG. 2 ) and receives and sends packets to the Internet  9  or other sources of content. The router  5  directs packet traffic to the system arrangement  10  via a switch  12  or via a set of switches  12  and  14 . The switches  12  and  14  may be ethernet switches (e.g., gigabit ethernet). In the embodiment shown packets are inspected and/or processed with application processing engines (ASEs) using a chassis  16  with a plurality of processing blades  20 . Each processing blade  20  is connected to each of the switches  12 ,  14  via gigabit ethernet connections  22  or other similar connection. The ASEs may also be implemented using individual computers or other processor arrangements. For example, the invention may be realized using multiple personal computers. The preferred embodiment employs multiple Intel processor blades  20  in an Intel compact PCI chassis  16 . In the embodiment of  FIG. 1 , a further chassis  18  is provided with further processor blades  20 . Other and further processing capabilities may be provided as needed based on the particular processing situation encountered. 
   The physical arrangement as shown in  FIG. 1  is used to provide a virtual system as shown in  FIG. 2 . Specifically, the physical processing blades  20  are configured to do any processing required based on traffic being directed to the blades  20  from the access devices switch or router  5  and/or switches  12 ,  14  or other access device via a virtual local area network (VLAN) established by addressing via IP (Internet protocol) addresses. The switches  12  and/or  14 , are configured to use the active blades  20  of the system  10  as their next hop for subscriber traffic. Traffic for subscribers is directed to the correct processing blades  20  of the system  10  either by routing advertisements from the active blades  20  or by statically configured routing for directing traffic to the interface addresses of the active blades  20 . This configuration causes all traffic to pass through the active components (the active blades  20 ) of the system  10 , enabling the system  10  to perform packet inspection and processing. As the active blades  20  are in the data flow, it is often important that failures be recovered quickly. 
     FIG. 2  shows a logical embodiment of the invention. The logical embodiment comprises ASEs  100  as part of the system  10  for processing packets received and sent to subscribers  7  and the Internet  9 . In the preferred embodiment, the ASEs  100  are features of the packet inspection system  10  in a Mobile Services Delivery System (MSDS). The MSDS is a single point for the creation and delivery of mobile data service policies including policies for access networks (roaming, home, 2.5 G, 3 G, WLAN), charging (postpaid, prepaid, content, event, promotion, time of day), and forwarding (content control, content or event limits). Operators can use the system  10  to create dynamic policies based on the instantaneous subscriber state. Although the preferred embodiment shown is for this purpose, the invention can be applied to any packet inspection engine situation. The invention can be applied to Digital Subscriber Loop (DSL), or cable modems with signaled subscriber features, providing redundancy for the interacting packet inspection engines. 
   The underlying system  10  directs traffic to active ASE components  100  via two techniques. First, the interface addresses that are known to neighbors are advertised with Address Resolution Protocol (ARP). Second tunnel termination points and address pools are advertised in routing pools, or configured in other parts of the network to be tied to an interface address. The system  10  provides the processing needed in conjunction with the configuration of active component ASEs  100 A. The active ASEs  100 A are assigned to a configuration (a number (n) of active ASEs  100 A support a configuration). A number (m) of inactive redundant or standby ASEs  100 S cooperate with the active ASEs  100 A to form one or several redundancy groups  300 ,  301 ,  302 , etc. to support the configuration. 
   The invention makes use of six logical aspects. The first aspect is master election/re-election for the system  10 , comprising the ASEs  100  that can talk to each other. When an ASE  100  starts and/or when it determines that it cannot reach the master ASE  100 M, an election is held. All of the ASEs  100  which can reach each other, and which cannot reach the current master, will conduct the election. The fact that one ASE  100  cannot reach the master does not cause another ASE to start participating in the election. The election/re-election includes participation by all of the ASEs  100  through exchanging messages  110  among all of the ASEs. Messages  110  are exchanged (multicast or broadcast) by the ASEs  100 , and the master ASE  100 M is elected. To do this, each ASE  100  multicasts a message  110  indicting the revision of software and configuration it has available, and its commissioned IP address. All ASEs  100  in the system  10  participate in this election as shown in  FIG. 3 . If the set of ASEs  100  has gotten partitioned, each group of communicating ASEs will hold a separate election. An isolated node or blade  20  which has no control communication with any other ASE refrains from becoming a master. All ASEs  100  in the system  10  examine the information they receive for a period of time after coming up. The ASE  100  with the most current software and configuration, and within that with the lowest identity value (such as lowest IP Address or MAC Address to break a deadlock), becomes master ASE  100 M after examining the messages  110 . 
   Thereafter, as long as it is operational the master ASE  100 M sends regular hello messages  112 , as shown in  FIG. 4A , to let other ASEs  100  in all redundancy groups  300 ,  301 ,  302 , etc. know that the master ASE  100 M is still alive. Note that if there is a master ASE  100 M running, the election is preempted. The existence of the master  100  M (preferably the existence of such a master  100 M with the newest software release) prevents another ASE  100  in the system  10  from becoming the master. 
   In the second logical aspect, if the master ASE  100 M determines that it has newer software or configuration than some other ASE  100  in the system  10 , then the master ASE  100  sends the newer software and/or configuration as shown at  114  in  FIG. 4B , to the ASEs  100  with the older information. If the existing master ASE  100 M determines that an ASE  100  that is coming up (such as a newly added ASE) is a better master ASE  100 M, then all the ASEs  100  in the current system  10  are reset to allow the new ASE to come up as the master  110 M. As the blades  20  that have been reset come up again, they will pull the latest software and/or configuration from the new master ASE  100 M. As this method of software upgrade is disruptive, the preferred embodiment includes a method for a more graceful upgrade of the software. Accordingly, the Master ASE is given the newer software for installation. The invention then practices a method for such software upgrade or change in software version in which the master ASE  100 M sets its software release status to a new version number of the new software (although the master ASE  100 M is not running the new software). The master ASE  100 M upgrades at least one standby ASE  100 S, and then upgrades the active ASEs  100 A. With this there are upgraded standby ASEs  100 S ready to take over the functions of the active ASEs  100 A. The master  100 M then upgrades the various other ASEs  100  and  100 S as shown in  FIG. 4B . Thus, the upgrade process causes no service disruption or loss of state information. When the master ASE  100 M determines that all of the known ASEs  100  are running the new software release, the master ASE  100 M resets itself so that it will come up with the new software release. This procedure is useful as it avoids the possibility of a standby ASE  100 S coming-up and causing a new election of a master based on the master ASE  100 M having the older software version. 
   The third logical aspect commences once a master ASE  100 M is elected. As shown in  FIG. 5A , several redundancy groups  300 ,  301 ,  302 , etc. are established. The operational configuration is the basis for the number of redundancy groups  300 ,  301 ,  302 , etc. of ASEs  100 , that number of redundancy groups  300 ,  301 ,  302 , etc. required for the operational configuration. The system  10  uses master ASE  100 M to assign components (blades  20 ) to fill the active and standby ASE roles as needed to meet the configuration. The master ASE  100 M then determines for each redundancy group  300 ,  301 ,  302 , etc. how many active ASEs  110 A are needed to support the operational configuration. For each required ASE  100 , the master ASE  100 M determines if there is already an active ASE  100 A performing that/those configured function(s). If so, that ASE  100 A continues to perform that function. Additional configurations which are not currently being serviced are given to available ASEs  100  with the ASE  100 M assigning configurations as shown at  116 . This assigning  116  may, for example, include giving some of the additional configurations to the master ASE  100 M. The ASEs  100  that are assigned and receive configurations then become active ASEs  100 A, performing the configured functions they are assigned. The master ASE  100 M assigns any remaining ASEs  100  (remaining processor components) to the redundancy groups  300 ,  301 ,  302 , etc. as standby ASE  100 S as shown at  116  in  FIG. 5A . The master ASE  100 M may either be an active ASE  100 A or a standby ASE  100 S or not participate in the redundancy group  300 . However, with the embodiment shown, the master ASE  100 M makes itself an active ASE  100  M/A in a redundancy group  300  as it knows it is functioning and is ready to take on processing functions. 
   In the fourth logical aspect, during operation, all active ASEs  100 A in a redundancy group  300  multicast all changes of subscriber state (accounting, service bindings, etc.) as shown schematically at  120  in  FIG. 5B  to all standby ASEs  100 S in the redundancy group  300 . Even when no state updates occur, each active ASE  100 A sends an update so that lost information can be recovered and so that the master ASE  100 M knows that the active ASE  100 A is still functioning. Sequence numbers and retransmission mechanisms ensure that this transmission is reliable. In the preferred embodiment, each message sent by an active ASE  100 A has a sequence number. If a standby ASE  100 S receives an update, and determines, due to a gap in the sequence numbers, that it is missing information, it sends a request  122  to the active ASE  100 A whose information it is missing, requesting that the information be sent. This request is retransmitted until the missing information is received. The process whereby active ASEs  100 A provide status data to redundant ASEs  100 S provides active mirroring, where the subscriber status data for any of the ASEs  100 A is also in the possession of each standby ASE  100 S. 
   In the fifth logical aspect ( FIG. 6 ), when an active ASE  100 A fails (any type of hardware or software failure) as indicated at  122 , the master ASE  100 M/A detects this failure by noting the absence of messages from that previously active failed ASE  100 F. The master ASE  100 M/A selects a standby ASE  100 S from the redundancy group  300  that the failed ASE  100 F was in, and directs that standby ASE  100 S as shown at  130  to assume the functions of the failed ASE  100 F. The standby ASE  100 S already has all of the configuration and all of the state (subscriber state) information from the failed ASE  100 A, so it can promptly assume the functions of the failed ASE  100 A. If the master ASE  100 M fails, a new election is held. 
   The selected standby ASE  100 S/A, now active, advertises the interfaces (and if necessary the routing advertisements) that the failed  100 F was advertising. The ASE  100 S/A receives the traffic the failed ASE  100 F was receiving, and processes it just as the failed ASE  100 F would have. 
   In the sixth logical aspect, if new ASEs  100 N are added to the system as shown in  FIG. 7 , they become additional standby ASEs  100 S. The new ASE  100 N listens to the multicast messages and detects the Master ASE  100 M. It sends its own liveness message, after which the Master ASE assigns the new ASE  100 N to a redundancy group. The new ASE  100 N then uses reliable transmission protocols (e.g., TCP, SCTP, etc.) to retrieve all previous state information from all the active ASEs in the redundancy group as shown at  140 , and then maintains that state information using the mechanism described above. In the event that the new ASE  100 N has a newer software release or a newer configuration than the current master ASE  100 M, then the new ASE 100 N takes over as master ASE, and distributes its newer software and/or configuration to all ASEs  100  in the system  10 . 
   While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
A system, mechanism and method are provided for inspecting packets. Application processing engines (ASEs) inspect an IP packet flow of subscribers. It is determined whether any of the ASEs is operating as a master and if not one of the ASEs is elected. The master forms one or more redundancy group of the ASEs based on a configuration of IP packet flow for subscribers determining for the redundancy group how many active ASEs are needed to support an operational configuration of the IP packet flow of the subscribers. If there is already an active ASE performing a determined configured function, the master allows the function to continue to be performed by that active ASE and assigns other configured functions to available ASEs with ASEs not assigned a configuration serving as standby ASE in the redundancy group. The active ASEs multicast or broadcast subscriber state data to each of the standby ASEs. The standby ASEs maintain received subscriber state data for each active ASE. A standby ASEs is activated when one of the active ASEs fails, the activated ASE may advertise the interfaces of the activated standby ASE and if necessary the routing advertisements that the failed ASE was advertising.