Abstract:
The invention has a general objective of mapping applications that generate packets to a QoS policy on a packet routed network, such as an IP network, and automatically generating and/or changing the configuration of network elements, such as routers, to treat packets from the application according to the QoS policy. In accordance with a preferred embodiment of the present invention, high-level descriptions of applications and quality of service (QoS) treatment, for example, are automatically translated into low-level QoS configurations for routers. Application profiles specifying how traffic for those applications should be treated can be specified by those without detailed technical knowledge and QoS configurations automatically created for download onto customer premises equipment and, if necessary, also to access and backbone networks.

Description:
RELATED APPLICATIONS 
   This patent application claims the benefit of Provisional Patent Application Ser. No. 60/397,081, entitled System and Method for Providing a Customer Controlled Network, filed on Jul. 19, 2002, the disclosure of which is incorporated herein by reference. 

   TECHNICAL FIELD OF THE INVENTION 
   The present invention relates generally to the field of computer networks, and more particularly to a system and method for providing a customer controlled network. 
   BACKGROUND OF THE INVENTION 
   Communications networks have finite capacity. When customers attempt to use more network capacity than is available, network equipment is forced to slow or stop some communications. A best-effort transport treats all traffic equally. In a network with best-effort delivery mechanisms, where for example, two end-users attempt to send 1 Mbps of traffic each across the same T 1  line, typically the network will limit each user to 0.77 Mbps of bandwidth. 
   However, networks of a type that traditionally provide best-effort transport, such as Internet Protocol (IP) based networks, are now carrying data for many different types of applications, with different quality of service (QoS) requirements. Examples of these applications are web browsing, database access, Voice over IP (VoIP), and videoconferencing. Network performance degradation impacts these applications differently. For example, a ten percent drop in available bandwidth has a negligible effect on web browsing but makes VoIP unusable. 
   Furthermore, enterprises place different values on various applications. For example, to an insurance company, a SAP-based claims processing application is mission-critical. To such a company, a ten percent drop in performance of a SAP® application is much worse than a ten percent drop in web browsing performance. 
   To address this problem, network elements, such as routers and switches, are now capable of classifying and prioritizing traffic in order to meet quality of service requirements. Each network element must be configured for quality of service requirements. Network elements typically use command line interfaces to enter configuration information. For this purpose cryptic and often complex commands must be learned. Furthermore, the mechanisms for providing QoS in the network elements are based on low-level network criteria, such as IP addresses, User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) port numbers. Thus, the underlying hardware and technology must be well understood. 
   Users who will also be referred to as customers, even if they are not purchasing, of wide area IP networks traditionally manage either their own routers directly or hire a service provider to do so. Direct management gives such user, complete control over their own equipment. However, customers must develop in-house expertise in router management. On the other hand, with a provider-managed router, customers do not need to develop router management expertise, but give up the ability to make arbitrary changes whenever they like. 
   Traditionally, either the user manages all aspects of a router configuration, or the service provider manages all aspects of the configuration. Since configurations are complex and cryptic, it is difficult to partition responsibility for different parts of a single configuration. Furthermore, traditionally, a “QoS policy” comprises a complex set of rules for classifying IP traffic and for tuning router parameters. For example, an access list may be used to match traffic on a particular port, say TCP port 6512, and route that traffic into a particular queue, say a weighted fair queue, with a particular weight, say 40.5. Furthermore, routers manufactured by different companies have different types of queues and different low level commands, thereby making it even more difficult for the customer to manage different aspects of configuring the router. 
   SUMMARY OF THE INVENTION 
   The invention has a general objective of mapping applications that generate packets to a QoS policy on a packet routed network, such as an IP network, and automatically generating and/or changing the configuration of network elements, such as routers, to treat packets from the application according to the QoS policy. In accordance with a preferred embodiment of the present invention, high-level descriptions of applications and quality of service (QoS) treatment, for example, are automatically translated into low-level QoS configurations for routers. Application profiles specifying how traffic for those applications should be treated can be specified by those without detailed technical knowledge and QoS configurations automatically created for download onto customer premises equipment (CPE) and, if necessary, also to access and backbone networks. 
   The invention is described and illustrated with reference to an exemplary application program embodying various aspects of the invention, which will be referred to herein as a “policy manager” (PM), that lets customers quickly and easily define application profiles. From the high-level descriptions provided by the customer, the PM automatically determines how to configure or reconfigure multiple network routers to translate the customer&#39;s high-level descriptions into low-level QoS configurations. 
   The PM in its exemplary embodiments thus provides one or more benefits and allows users to manage QoS across an enterprise network through a central web interface. Users do not need to know or understand the underlying router command line interface instructions that might vary from one manufacturer&#39;s router to another manufacturer&#39;s router. Users may control their own equipment and at the same time make changes whenever they like. Users do not need to understand the details of QoS for a particular router. The details of QoS are transparent to the user and the user may configure or reconfigure many routers through a single action. The PM makes it easy for users to accurately describe how they wish their networks to perform. For example, using the web interface component of the PM, the user may specify a service plane from a plurality of service planes for each of its applications. For example, a user may map a SAP® application to a priority service plane, an ORACLE® application to the priority service plane, PBX traffic to a voice service plane, and video traffic to a video service plane. The PM automatically translates the high-level policies specified by the user via the web interface into low-level QoS command-line interface (CLI) commands acceptable by the routers. 
   Other aspects and features of the invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, the objects and advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings in which: 
       FIG. 1  is a schematic diagram of a customer controlled network; 
       FIG. 2A  is a flowchart of a method for providing a customer controlled network; 
       FIG. 2B  is a flowchart of a method for automatically updating a network; and 
       FIGS. 3A–3G  are exemplary screen displays of a policy manager. 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
   In accordance with an embodiment of the present invention, high-level descriptions of applications and quality of service (QoS) treatment, for example, are automatically translated into low-level QoS configurations for routers on a network. Users (who may also be referred to herein as customers because they are typically purchasing the transport services from a third party, and because the PM can be of particular advantage to users of third-party-managed network) may thus be permitted to specify application profiles on how traffic for those applications should be treated and how QoS configurations automatically created for download onto routers and other equipment for marking of packets. The equipment may be customer premises equipment (CPE) and, if necessary, equipment on access and backbone networks. 
   The invention will be described in reference to what will be referred to as a “policy manager” or “PM.” PM  12  is either a program in its preferred embodiment or a service provided through a web server  13  accessible through a web browser  15 . The invention is not limited to a PM as described. The PM preferably comprises a graphical user interface  17  ( FIG. 3A ) that lets customers quickly and easily define application profiles. From the high-level descriptions provided by the customer, PM  12  automatically determines how to configure or reconfigure multiple network routers  28   1  through  28   N  to translate the customer&#39;s high-level descriptions into low-level QoS configurations. 
   Briefly, in an exemplary embodiment, PM  12  receives application profiles from a customer. PM  12  converts the received application profiles into traffic descriptors. One or more generic, or vendor-independent, access lists are created from the traffic descriptors. Preferably, a generic access list is independent of router hardware. The vendor specific access list is then generated for the specific router(s) that will be marking the traffic for QoS treatment using, for example, DiffServ. Subsequently, the configurations of one or more routers in the network are updated with the access lists. A detailed description for each of the above steps follows. 
   PM  12  receives application profiles from a customer. Because routers use low-level network criteria, such as Transmission Control Protocol (TCP) port numbers, User Datagram Protocol (UDP) port numbers, IP protocol numbers, IP precedence values, etc., traditionally the most complex part of configuring QoS on a traditional router using a Common-Line Interface (CLI) is creating the rules to classify traffic. 
   PM  12  may, if desired, include a plurality of predefined default applications. For example a SAP® application may, by default, communicate through a specific port number. Thus, the customer can simply select the applications it is interested in from the plurality of predefined applications by using graphical user interface component  17  of PM  12 . Furthermore, PM  12  makes it easy for the customer to create new applications in terms of underlying network criteria. For example, if a legacy application PolicyRater uses TCP and runs on TCP port 15567, the customer can use graphical user interface component  17  of PM  12  to define a PolicyRater application that matches those network criteria. Once an application has been defined, the customer does not have to consider low-level network criteria. They can simply use the application by name in the PM policy definition. 
   The network preferably includes a plurality of predefined service planes for QoS from which a customer may select for mapping to the applications. Examples of such service planes are:
         Normal—Best-effort traffic.   Priority Data—Prioritized data applications. Within Priority, traffic may be classified Low, Medium, or High.   Reserved Bandwidth—Reserved bandwidth for bandwidth-critical applications.   Video—Reserved bandwidth with videoconferencing-quality latency and packet delivery.   Voice—Reserved bandwidth with voice-quality latency and packet delivery.       

   The PM users assign application profiles to service planes. PM  12  takes two actions depending on the service plane selection:
         Marking—The PM uses DiffServ marking to mark each service plane differently. The network core uses these markings to differentiate traffic. For example, the PM marks voice traffic with IP precedence value  101 .   Prioritization—The PM prioritizes traffic on the outbound serial line. With reference to the exemplary service planes described above, the PM assigns reserved bandwidth capacity for Reserved, Video, and Voice. For Priority and Normal, the PM assigns relative priorities.       

   Internally, PM  12  describes application profiles as traffic descriptors. PM  12  converts the received application profiles into traffic descriptors. Traffic descriptors are Boolean expressions on primitive network predicates. For example, web traffic is TCP traffic to or from TCP port 80. Thus, for example, the traffic descriptor for web traffic can be expressed as AND(protocol=tcp, OR(source-port=80, dest-port=80)). However, Boolean expressions are difficult for non-technical customers to describe and edit. To simplify traffic description, PM  12  provides application profile abstraction which automatically converts application profiles into traffic descriptors thereby utilizing the power of traffic descriptors while hiding the complexity of Boolean expressions from the customer. 
   In an exemplary embodiment, an exemplary application profile comprises:
         One of the following combination rules:
           All—Match traffic that meets all of the following criteria.   Some—Match traffic that meets at least one of the following criteria.   None—Match traffic that does not meet any of the following criteria.   
           Zero or more “simple application descriptors”   Zero or more included application profiles       

   A simple application descriptor may comprise of one or more of the following properties:
         Protocol (Any, TCP, or UDP)   Source address (Any, a specific address, or a subnet)   Destination address   Source TCP/UDP ports (Any, or a specific port, or a range of ports)   Destination TCP/UDP ports   IP precedence value (0 through 7)   IP type of service (TOS) value (0 through 15)       

   A simple application descriptor represents the conjunction (logical AND) of all its components. For example, a simple application descriptor that specifies TCP for protocol and 80 for source ports matches traffic that (1) is TCP, and (2) originates from TCP port 80. 
   By combining simple application descriptors in application profiles, and optionally combining multiple application profiles into compound application profiles, customers can easily describe complex traffic classes. 
   To translate an application profile into a traffic descriptor, PM  12 :
         Translates each simple application descriptor into an AND.   Translates each included application profile into a traffic descriptor.   Combines the resulting traffic descriptors according to the combination rule:   All—Build an AND of the components.   Some—Build an OR of the components.   None—Build an AND of the negations of the components.       

   EXAMPLES 
   HTTP 
   To match simple web traffic, define an application profile HTTP using the combination rule “Some” and two simple application descriptors:
         protocol=TCP, source port=80   protocol=TCP, destination port=80       

   This application profile corresponds to the following traffic descriptor: OR(AND(protocol=tcp, source port=80), AND(protocol=tcp, destination port=80)). 
   Web 
   To match insecure and secure web traffic (HTTP or HTTPS), define an application profile using the combination rule “Some,” two simple application descriptors, and a single included application profile “HTTP.” The application descriptors are given by:
         protocol=TCP, source port=443   protocol=TCP, destination port=443.       

   This application profile corresponds to the following traffic descriptor: 
                                           OR(             AND(protocol = tcp, source port = 80),             AND(protocol = tcp, destination port = 80),             AND(protocol = tcp, source port = 443),             AND(protocol = tcp, destination port = 443)).                        
Non-Marketing Web
 
   Consider an enterprise where the marketing department uses a 10.2.3.0/24 subnet. The application profile NonMarketingWeb matches all web traffic from corporate departments other than the marketing department. 
   First, define an application profile MarketingSubnet that matches the marketing department subnet. Use the combination rule “Some” and two simple application descriptors—one that matches a source address of 10.2.3 in the 255.255.255.0 netmask, and another that matches a destination address of 10.2.3 in the 255.255.255.0 netmask. Then define an application profile NonMarketingSubnet by using the combination rule—None and including a single application profile—MarketingSubnet. Finally, define the NonMarketingWeb profile by using the combination rule—All to combine Web and NonMarketingSubnet. 
   This application profile corresponds to the following traffic descriptor: 
   
     
       
             
           
         
             
                 
             
           
           
             
               AND( 
             
             
                 /**Web**/ 
             
             
                 OR( 
             
             
                   AND(protocol = tcp, source port = 80), 
             
             
                   AND(protocol = tcp, destination port = 80), 
             
             
                   AND(protocol = tcp, source port = 443), 
             
             
                   AND(protocol = tcp, destination port = 443)), 
             
             
                 AND( 
             
             
                   /**NonMarketingSubnet**/ 
             
             
                   NOT( 
             
             
                     /**MarketingSubnet**/ 
             
             
                     OR( 
             
             
                       AND(source address = 10.2.3/255.255.255.0), 
             
             
                       AND(destination address = 10.2.3/255.255.255.0))))) 
             
             
                 
             
           
        
       
     
   
   PM  12  uses the traffic descriptor abstraction to describe subsets of the universe of IP data packets. For example, to construct a policy that prioritizes web access, PM  12  abstracts the set of all possible web data packets. A traffic descriptor matches the set of all IP data packets that evaluate to true under the traffic descriptor&#39;s Boolean expression. Exemplary Table A provides a list of elements that form traffic descriptors: 
   
     
       
             
             
           
         
             
               TABLE A 
             
             
                 
             
             
               ELEMENT SCHEMA 
               DESCRIPTION 
             
             
                 
             
           
           
             
               All 
               Matches all traffic. 
             
             
               None 
               Matches no traffic. 
             
             
               Protocol = PROTOCOL 
               Matches traffic of the given IP protocol PROTOCOL. 
             
             
               source address = ADDR 
               Matches traffic from the given source IP address ADDR, 
             
             
               source address = ADDR/MASK 
               matching on nonzero bits of MASK, which defaults to 
             
             
                 
               255.255.255.255. 
             
             
               source port = PORT 
               Matches TCP or UDP traffic from the given TCP/UDP 
             
             
               source port = MIN . . . MAX 
               port numbers. 
             
             
               Destination address 
               Like source address, but for destinations. 
             
             
               Destination port 
               Like source port, but for destinations. 
             
             
               Precedence = VALUE 
               Matches traffic with an IP precedence value of VALUE. 
             
             
               tos = VALUE 
               Matches traffic with an IP TOS value of VALUE. 
             
             
               AND(expr 1 , expr 2 , . . . , expr N ) 
               Matches traffic that matches all of expr 1 , expr 2 , . . . , 
             
             
                 
               expr N . 
             
             
               OR(expr 1 , expr 2 , . . . , expr N ) 
               Matches traffic that matches at least one of expr 1 , expr 2 , 
             
             
                 
               . . . , expr N . 
             
             
               NOT(expr) 
               Matches traffic that does not match expr. 
             
             
                 
             
           
        
       
     
   
   Internally, PM  12  preferably represents traffic descriptors as tree data structures. PM  12  applies rules to simplify traffic descriptors as much as possible. Such simplification speeds configuration generation and results in shorter, faster configurations. Exemplary Table B provides a list of simplification rules that may be used by PM  12 : 
   
     
       
             
             
           
         
             
               TABLE B 
             
             
                 
             
             
               RULE 
               EXAMPLES 
             
             
                 
             
           
           
             
               splice like expression arguments 
               AND(AND(a, b), c) → AND(a, b, c) 
             
             
               delete non-primitive NOTs 
               NOT(AND(a, b)) → OR(NOT(a), NOT(b)) 
             
             
                 
               NOT(OR(a, b)) → AND(NOT(a), NOT(b)) 
             
             
                 
               NOT(NOT(a)) → a 
             
             
               combine network primitives 
               Some network primitives can combine under AND or 
             
             
                 
               OR. Some schematic examples: 
             
             
                 
               AND(port = 10 . . . 100, port = 50 . . . 200) → port = 50 . . . 100. 
             
             
                 
               AND(port = 10 . . . 100, port = 200) → none 
             
             
                 
               AND(address = 1.2.3.4/255.0.255.0, address = 5.6.7.8/0.255.0.255) → address = 1.6.3.8. 
             
             
                 
               NOT(port = 0 . . . 100) → port = 101 . . . 65535 
             
             
               same-sign subset rule 
               In an AND, if there are two clauses α and β such that 
             
             
                 
               α&#39;s OR-clauses form a subset of β&#39;s OR-clauses, then β 
             
             
                 
               may be eliminated. (And conversely for OR over 
             
             
                 
               AND.) For example, AND(P, X, Y, OR(P, Q, R)) → AND(P, 
             
             
                 
               X, Y) taking α = P and β = OR(P, Q, R). 
             
             
               opposite-sign subset rule 
               In an AND, if there are two clauses α and β such that 
             
             
                 
               the OR-clauses of the negation of α form a subset of 
             
             
                 
               the OR-clauses of β, then the OR-clauses of the 
             
             
                 
               negation of α may be dropped from β. (And conversely 
             
             
                 
               for OR over AND.) For example, AND(P, Q, R, 
             
             
                 
               OR(NOT(P), X, Y)) → AND(P, Q, R, OR(X, Y)) 
             
             
                 
               taking α = P and β = OR(NOT(P), X, Y). 
             
             
               eliminate trivial ANDs and ORs 
               AND(x) → x 
             
             
                 
               OR(x) → x 
             
             
                 
             
           
        
       
     
   
   PM  12  preferably comprises a generic access list generator  20 . Preferably, one or more generic access lists are created from the traffic descriptors. Preferably, a generic access list is created for each application profile. A generic access list comprises of one or more statements. A statement comprises of a clause and a match rule, for example a permit or a deny. A clause is preferably a list of network criteria, such as protocol, source address, destination address, source port, destination port, IP precedence value, IP TOS value, and/or the like. An exemplary clause may be given by &lt;source address=1.1.2.2, destination port =80&gt;. Preferably, clauses are logical ANDs and may not contain negations or ORs. 
   The following is a generic access list for matching HTTP traffic: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               permit &lt;protocol = tcp, source port = 80&gt; 
             
             
                 
               permit &lt;protocol = tcp, destination port = 80&gt; 
             
             
                 
               deny all 
             
             
                 
                 
             
           
        
       
     
   
   The following is a generic access list for the application profile NonMarketingWeb described above: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               deny &lt;source address = 10.2.3/255.255.255.0&gt; 
             
             
                 
               deny &lt;destination address = 10.2.3/255.255.255.0&gt; 
             
             
                 
               permit &lt;protocol = tcp, source port = 80&gt; 
             
             
                 
               permit &lt;protocol = tcp, destination port = 80&gt; 
             
             
                 
               permit &lt;protocol = tcp, source port = 443&gt; 
             
             
                 
               permit &lt;protocol = tcp, destination port = 443&gt; 
             
             
                 
               deny all 
             
             
                 
                 
             
           
        
       
     
   
   Preferably, generic access lists are non-hierarchical. To evaluate a data packet against a generic access list, the first clause that matches the packet is determined. If the matching clause&#39;s statement is a permit statement, then the access list matches the packet. If the access list is being used to select packets for a particular bandwidth class, then the bandwidth class applies to that packet. If the matching clause&#39;s statement is a deny statement, then the access list does not match the packet. If the access list does not match, then the bandwidth class does not apply to that packet. Other classes and generic access lists map still apply. If no list applies, then preferably best-effort delivery is used. 
   A traffic descriptor may correspond to multiple generic access lists. For example, consider the traffic descriptor AND(source address=1.1.1.1, NOT(source port=15)). One generic access list that the above traffic descriptor corresponds to is: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               &lt;deny &lt;source port = 15&gt;, 
             
             
                 
               permit &lt;source address = 1.1.1.1&gt;, 
             
             
                 
               deny all&gt; 
             
             
                 
                 
             
           
        
       
     
   
   Another generic access list that the above traffic descriptor corresponds to is: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               &lt;permit &lt;source address = 1.1.1.1, source port = 0...14&gt;, 
             
             
                 
               permit &lt;source address = 1.1.1.1, source port = 16...65535&gt;, 
             
             
                 
               deny all&gt; 
             
             
                 
                 
             
           
        
       
     
   
   It is desirable to find the shortest generic access list that corresponds to a given traffic descriptor. However, this problem is “NP-complete,” a computer science term that indicates that a problem is intractable. In other words, it is impossible to write a computer program that is guaranteed to solve the generic access list translation problem exactly in a reasonable amount of time. However, it is possible to write an efficient algorithm that finds good approximate solutions. PM  12  uses an algorithm that finds generic access lists quickly, but does not always find the shortest possible generic access list. 
   There may be two types of generic access lists—a theory and a complete theory. A theory is a partially constructed access list with an unfinished component represented as a traffic descriptor. A theory is written as a pair of the access list statements generated so far and the traffic descriptor for the unfinished portion (the remainder). For example, any traffic descriptor D corresponds to the theory &lt;&lt;&gt;, D&gt;(the empty generic access list followed by D). A complete theory is a theory with a complete generic access list and a remainder of none. 
   To generate an access list, PM  12  uses a pool of theories starting with the &lt;&lt;&gt;, D&gt;theory. The PM repeatedly removes a theory from the pool, derives new theories from that theory, and adds the new theories to the pool. The PM seeks to generate simpler theories (theories that have longer access lists and shorter remainders than their bases). The PM is finished when it finds a complete theory. 
   An exemplary simple derivation of the generic access list for HTTP traffic is given below: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               &lt;&lt;&gt;, OR(AND(protocol = tcp, source port = 80), 
             
             
                 
                 AND(protocol = tcp, destination port = 80))&gt; 
             
             
                 
               &lt;&lt;permit &lt;protocol = tcp, source port = 80&gt;&gt;, 
             
             
                 
                 AND(protocol = tcp, destination port = 80)&gt; 
             
             
                 
               &lt;&lt;permit &lt;protocol = tcp, source port = 80&gt;, 
             
             
                 
                 permit &lt;protocol = tcp, destination port = 80&gt;&gt;, none&gt; 
             
             
                 
                 
             
           
        
       
     
   
   To complete the above schematic algorithm, an explanation of how to derive theories and how to select the next theory to work on is provided below. 
   Theory Derivation: 
   PM  12  uses rules for adding a new access list statement. 
   Permit Rule 
   Consider a theory T 1 =&lt;&lt;S 1 , S 2 , . . . , S N &gt;, R&gt; where remainder R=OR(E 1 , E 2 ). If E 1  is directly translatable into an access list clause X, then a new theory T 2 =&lt;&lt;S 1 , S 2 , . . . S N , permit X&gt;, E 2 &gt; may be derived. For example, consider the following partial theory: 
   
     
       
             
           
         
             
                 
             
           
           
             
                 &lt;&lt;permit &lt;source address = 1.1.1.1&gt;&gt;, 
             
             
                 OR(AND(protocol = tcp, source port = 80), 
             
             
                 AND(protocol = tcp, destination port = 80))&gt; 
             
             
                 AND(protocol = tcp, source port = 80) is directly translatable into an 
             
             
                 access list clause 
             
             
               &lt;protocol = tcp, source port = 80&gt;. So, the permit rule may be used to 
             
             
               derive this theory: 
             
             
                 &lt;&lt;permit &lt;source address = 1.1.1.1&gt;, 
             
             
                 permit &lt;protocol = tcp, source port = 80&gt;&gt;, 
             
             
                 AND(protocol = tcp, destination port = 80)&gt; 
             
             
                 
             
           
        
       
     
   
   A second application of the permit rule to the above theory would derive a complete theory. 
   Deny Rule 
   Consider a theory T 1 =&lt;&lt;S 1 , S 2 , . . . , S N &gt;, R&gt; where remainder R=AND(E 1 , E 2 ). If the negation of E 1  is directly translatable into an access list clause X, then a new theory T 2 =&lt;&lt;S 1 , S 2 , . . . , S N , deny X&gt;, E 2 &gt; may be derived. For example, consider the partial theory: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               &lt;&lt;permit &lt;source address = 1.1.1.1&gt;&gt;, 
             
             
                 
               AND(OR(NOT(protocol = tcp), NOT(source port = 1500)), 
             
             
                 
               OR(protocol = tcp, destination port = 80))&gt; 
             
             
                 
                 
             
           
        
       
     
   
   Consider the clause OR(NOT(protocol=tcp), NOT(source port=1500)). Its negation is AND(protocol=tcp, source port=1500), which is directly translatable into an access list clause. So, the deny rule may be used to derive this theory: 
                                           &lt;&lt;permit &lt;source address = 1.1.1.1&gt;,           deny &lt;protocol = tcp, source port = 1500&gt;&gt;,           OR(protocol = tcp, destination port = 80)&gt;                        
Complex Theory Derivation:
 
   Most derivations revolve around the permit and deny rules. However, for many traffic descriptors, neither rule applies. For example, consider the traffic descriptor:
         OR(AND(source port=5, not(source address=1.1.1.1)),   AND(source port=7, not(source address=2.2.2.2)))       

   The outer OR implies the permit rule. However, neither OR clause can be represented as a single access list clause. 
   The PM preferably uses two techniques on theories where neither simple rule applies—Cross Multiplication and Clausal Inflation. 
   Cross Multiplication 
   Any AND of ORs may be converted into an OR of ANDs, or vice versa, by cross-multiplying, since AND is distributive over OR and vice versa. By cross-multiplying and simplifying, the PM often transforms inconvertible remainders to convertible remainders. 
   Clausal Inflation 
   Consider a network primitive such as NOT(source port=50). The NOT may be eliminated by increasing the number of clauses: NOT(source port=50)→OR(source port=0 . . . 49, source port=51 . . . 65535). This is a deliberate reversal of a simplification rule. 
   By inflating, the PM can transform inconvertible remainders into convertible remainders. 
   Table C illustrates an exemplary conversion of an exemplary traffic descriptor into a generic access list. 
                           TABLE C                           Input:           &lt;&lt;&gt;, OR(AND(source port = 5, NOT(source address = 1.1.1.1)),             AND(NOT(source port = 7), source address = 2.2.2.2))&gt;           After inflating NOT(source port = 7):           &lt;&lt;&gt;, OR(AND(source port = 5, NOT(source address = 1.1.1.1)),             AND(OR(source port = 0...6, source port = 8...65535),              Source address = 2.2.2.2))&gt;           Cross-multiply against the inflation result:           &lt;&lt;&gt;, OR(AND(source port = 5, NOT(source address = 1.1.1.1)),             OR(AND(source port = 0...6, source address = 2.2.2.2),              AND(source port = 8...65535, source address = 2.2.2.2)))&gt;           Splice OR of OR:           &lt;&lt;&gt;, OR(AND(source port = 5, NOT(source address = 1.1.1.1)),             AND(source port = 0...6, source address = 2.2.2.2),             AND(source port = 8...65535, source address = 2.2.2.2))&gt;           Use the permit rule:           &lt;&lt;permit &lt;source port = 0...6, source address = 2.2.2.2&gt;&gt;,            OR(AND(source port = 5, NOT(source address = 1.1.1.1)),            AND(source port = 8...65535, source address = 2.2.2.2))&gt;           Use the permit rule:           &lt;&lt;permit &lt;source port = 0...6, source address = 2.2.2.2&gt;            permit &lt;source port = 8...65535, source address = 2.2.2.2&gt;&gt;,            OR(AND(source port = 5, NOT(source address = 1.1.1.1)))&gt;           OR(x) → X:           &lt;&lt;permit &lt;source port = 0...6, source address = 2.2.2.2&gt;            permit &lt;source port = 8...65535, source address = 2.2.2.2&gt;&gt;,            AND(source port = 5, NOT(source address = 1.1.1.1))&gt;           Use the deny rule:           &lt;&lt;permit &lt;source port = 0...6, source address = 2.2.2.2&gt;            permit &lt;source port = 8...65535, source address = 2.2.2.2&gt;            deny &lt;source address = 1.1.1.1&gt;&gt;,            source port = 5&gt;           Use the permit rule to reach a complete theory:           &lt;&lt;permit &lt;source port = 0...6, source address = 2.2.2.2&gt;            permit &lt;source port = 8...65535, source address = 2.2.2.2&gt;            deny &lt;source address = 1.1.1.1&gt;            permit &lt;source port 5&gt;&gt;,            none&gt;                        
Theory Selection:
         1. The main loop of the access list generator works by selecting a theory, removing it from the pool, and adding its derivatives to the pool.   2. The PM selects the “best” available theory from the pool according to these criteria:
           Prefer theories with remainders that have fewer total primitive network cr 2 teria.   
           For theories with equal remainders, prefer theories with shorter so-far access lists.   3. This technique helps the PM find solutions quickly, by preferring theories that are closer to completion.       
   The received application profiles and the selected QoS are converted into hardware specific low-level CLI commands. The actual implementation of this step is hardware specific. Following is an example implementation for CISCO® routers. 
   CISCO® “policy maps” are CLI commands that establish queuing techniques for different traffic classes. Policy maps do not provide a way to combine absolute bandwidth criteria (suitable for applications such as voice and video) with relative priority criteria (suitable for applications such as an ORACLE® application and a SAP® application). The PM uses the following method to create CISCO® policy maps:
         Use CISCO® “priority” commands to establish fixed low-latency-queue bandwidth reservation for the Voice and Video service planes.   Count the number N of relative priority classes. For example, if a policy maps a PEOPLESOFT® application to Normal, an ORACLE® application to Priority/Low, a SAP® application to Priority/Medium, and a BAAN® application to Priority/High, there are four classes.   Use the CISCO® “bandwidth” command to assign relative bandwidth to each traffic class using this formula:       

           ⌊     100   ×         2     i   -   1       -   1         2   N     -   1         ⌋         
for each class i=1 to N. For example, in the example above, for a BAAN® application, i=4, the formula yields “bandwidth 46.”
 
   This method combines absolute and relative priorities in the same policy and effectively translates high-level QoS policy. 
   One or more routers, for example Customer Premises Equipment (CPE) in the network may then be updated. In order to log in and make configuration changes in the routers, the PM needs to know the router passwords. Customers can choose to save passwords within the PM, or provide passwords when prompted for every change. 
   The PM represents QoS configlets (lists of configuration commands) as directed acyclic graphs (DAGs). For example, a CISCO® policy-map command is one node in the PM DAG. If two policy-maps use the same underlying access list (for example, when the same policy is applied to two different router interfaces), then the policy-map nodes will point to the same child node in the DAG. 
   When the PM updates a router, it first checks to see if the router&#39;s configuration has changed since the PM last touched the router. If not, the PM retrieves the DAG that was used to produce the last configuration, and compares it to the new DAG.
         If a sub-DAG of the new DAG matches a sub-DAG of the old DAG, the PM reuses the old sub-DAG by copying its name into the new DAG.   Any sub-DAGs of the old DAG that are not used in the new DAG are deleted using delete statements of the underlying hardware.   Any sub-DAGs of the new DAG that are not in the old DAG are created.       

   By following these steps, the PM guarantees maximum reuse of configuration objects that already exist on a target router, and a minimal list of commands. By using a minimal list of commands, the PM speeds router updating. 
   Service Plane Abstraction 
   The PM automatically preferably selects the best underlying QoS for each application profile received from the customer. In general, routers provide many low-level QoS technologies. For example, routers manufactured by CISCO® provide techniques, such as low-latency queuing, class-based weighted fair queuing, and weighted random early detection. 
   The PM hides this detail from end-users by automatically selecting the best underlying technology for a particular need. For example, consider a policy that maps a SAP® application to the Priority plane and video traffic to the Video plane. It has been empirically determined that on CISCO® routers, low-latency queuing with padded bandwidth reservation is the best way to prioritize video traffic, while class-based weighted fair queuing with bandwidth-based tuning is the best way to prioritize application traffic. For the example policy, the PM automatically generates CLI commands corresponding to CISCO® routers to map the video traffic to a low-latency queue and SAP® traffic to a weighted fair queue. 
     FIG. 1  shows an exemplary network  10 . In a preferred and exemplary embodiment, PM  12  comprises a workflow manager  14 , a configuration generator  16 , a router manager  18 , the generic access list generator  20 , the web interface  22 , and an application layer  24 . These elements are implemented in software executing on a computing machine, which may include a general purpose computer, a router, or other network element with a processor capable of executing software or firmware instructions. The software is stored in computer readable media or memory. Furthermore, these elements represent general functions, and these functions may be combined or implemented in a single program or multiple programs, and may run on the same computing machine or be distributed among multiple computing machines. Briefly, application layer  24  reads and writes data to and from a Relational Database Management System (RDBMS)  26 . Although an exemplary embodiment of the present invention is discussed herein with reference to the use of RDBMS  26 , the invention is not so limited. If desired, any type of data storage mechanism may be used to store the data on any type of persistent data storage device, such as FLASH memory, text or flat files on a disk, and/or the like. Application layer  24  is also capable of verifying whether the application profiles received from the customer are valid. Router manager  18  interfaces with a plurality of routers  28   1 ,  28   2 , . . . ,  28   N , for example CPE routers. Workflow manager  14  determines which routers are effected by the changes and calls router manager  18  to update the routers. Workflow manager  14  also calls configuration generator  16  to generate new configurations based on the changes received from the customer. 
   The flowcharts of  FIGS. 2A and 2B  illustrate an exemplary process flow. At step  32 , an end-user, for example, an IT administrator, of a customer logs into a web site (step  32 ), and selects the PM screen (step  34 ). At step  36 , the customer makes changes to his or her PM definitions using an interface  17 , such as shown in  FIGS. 3A through 3E . The customer may make one or more of the following changes: select a policy for a router interface that had no policy (one site router may have multiple interfaces); select no policy for an interface that had a policy; select a different policy for an interface; create or delete a policy; select a service plane in a policy for an application that was unprioritized in that policy; change service planes for an application in a policy; select the Normal (unprioritized) plane for an application in a policy. Normal is the default for all applications; create or delete an application; and/or change an application, such as by adding a simple application descriptor, deleting a descriptor, or changing the list of included applications ( FIG. 3E ). 
   At step  38 , the customer clicks [Done]. At step  40 , PM  12  checks dependencies and determines which sites should be updated. For example, if policy A uses application profile B, and site S uses policy A, then S needs to be updated if B changes. At step  42 , PM  12  presents a screen to the customer, detailing which sites need to be updated at step  42 . The customer can choose to update immediately, not update, or update at a specific time. 
   As indicated by steps  44 ,  46 ,  48  and  50 , if the customer chooses to update at a specific time, PM  12  waits for that time to arrive before beginning the update process. When it is time to update, PM  12  queries the database for the current state of the customers application profiles, policies, and sites at step  60  ( FIG. 2B ). For each site that needs to be updated, and for each policy applied to an interface on that site, PM  12  performs one or more of the steps of  FIG. 2B  as discussed below. 
   At step  62 , PM  12  queries the application profiles used by that policy. At step  64 , PM  12  generates traffic descriptors for each application. At step  66 , PM  12  merges traffic descriptors for applications assigned to the same service plane. For example, if a Web application and an ORACLE® application are both assigned to Reserved, the PM generates a single traffic descriptor that matches traffic that is associated with the Web application or the ORACLE® application. At step  68 , PM  12  generates a generic access list for each merged traffic descriptor. At step  70 , PM  12  translates the generic access list into a router-specific access list. At step  72 , PM  12  creates router specific policy commands that assign priorities to access lists. At step  74 , PM  12  determines which commands are not necessary due to existing configuration on the target router. At step  76 , PM  12  connects to the target router via telnet or Secure Shell (SSH) (user configurable). At step  78 , the router&#39;s current entire configuration is compared against the last known configuration stored in the database. If the configuration changed, PM  12  deletes PM  12  created router commands and recreates the QoS configuration from scratch at steps  80  and  82 . At step  84 , PM  12  issues commands to create new access lists and policy choices, delete old ones, and apply the new policy if any. At step  86 , PM  12  queries the target router for its entire current resulting configuration. At step  88 , PM  12  stores the entire current resulting configuration in the database. At step  50  ( FIG. 2A ), PM  12  reports interactive progress bars to the user during the update as shown in  FIG. 3F . 
   Policy Inheritance: 
   When a customer creates a policy, the customer may optionally base that policy on another policy. A policy inherits the prioritization selection of its base policy, and may override with additional selections. For example, consider a policy Corporate that prioritizes a SAP® application and an ORACLE® application on the Priority plane. 
   A customer applies Corporate to all sites. Then, the customer adds a new site that has VoIP traffic. The customer creates a new policy, CorporateVoice, based on Corporate. In CorporateVoice, the customer defines one prioritization: voice traffic to the Voice service plane. When the customer adds a BAAN® policy to the Corporate policy, all sites are updated, including the site with CorporateVoice. That site is the only site with prioritized voice traffic. 
   Exemplary screen shots of the web interface component of PM  12  are illustrated in  FIGS. 3A through 3F . 
   Although an embodiment of the present invention has been described above with different modules performing different operations, the invention is not so limited. One or more of the above described modules may be combined without departing from the scope of the present invention. Embodiments of the present invention may be implemented in software, hardware, or a combination of both software and hardware. 
   If desired, the different steps discussed herein may be performed in any order and/or concurrently with each other. Furthermore, if desired, one or more of the above described steps may be optional or may be combined without departing from the scope of the present invention.