Patent Publication Number: US-6708187-B1

Title: Method for selective LDAP database synchronization

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional applications Nos. 60/138,849, 60/138,850, 60/139,033, 60/139,034 60/139,035, 60/139,036, 60/139,038, 60/139,042, 60/139,043, 60/139,044, 60/139,047, 60/139,048, 60/139,049, 60/139,052, 60/139,053, all filed on Jun. 10, 1999, and U.S. provisional application No. 60/139,076, filed on Jun. 11, 1999, the contents of all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to computer networks, and more particularly, to devices and methods for updating configuration database information of remote private networks across the Internet. 
     BACKGROUND OF THE INVENTION 
     The growth and proliferation of computers and computer networks allow businesses to efficiently communicate with their own components as well as with their business partners, customers, and suppliers. However, the flexibility and efficiencies provided by such computers and computer networks come with increasing risks, including security breaches from outside the corporation, accidental release of vital information from within it, and inappropriate use of the LAN, WAN, Internet, or extranet. 
     In managing the growth of computer networks as well as addressing the various security issues, network managers often turn to network policy management services such as firewall protection, Network Address Translation, spam email filtering, DNS caching, Web caching, virtual private network (VPN) organization and security, and URL blocking for keeping network users from accessing certain Web sites through use of the organization&#39;s ISP. Each policy management service, however, generally requires a separate device that needs to be configured, managed, and monitored. Furthermore, as an organization grows and spreads across multiple locations, the devices maintained also multiplies, multiplying the associated expenditures and efforts to configure, manage, and monitor the devices. 
     The solution to this problem is not as simple as just integrating multiple network policy management functions into a single device at each location and allowing each location to share its policy information with other locations. In fact, there are many obstacles and challenges in adopting such an approach. One of these challenges is devising a scheme for specifying, distributing, and updating policy management information effectively across the entire organization. The challenges increase if a directory service protocol such as a Lightweight Directory Access Protocol (LDAP) directory is used to store the policy management information. LDAP database management typically suffers from a lack of flexibility that becomes increasingly relevant as the size of the database increases. These problems generally become more severe in a network with multiple databases that must be synchronized together with multiple applications that require updates to only selected portions of a larger database. For example, conventional approaches to LDAP database management such as SLURPD (stand-alone LDAP update replication daemon) require updates of the entire database and do not include application-specific notification. 
     Accordingly, there remains a need in the art for a method for efficiently synchronizing multiple LDAP databases storing configuration information including policy management information. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a unified policy management system where various policies, namely, the set of rules and instructions that determine the network&#39;s operation, may be established and enforced from a single site. According to one embodiment of the invention, a central policy server maintains a central database storing configuration information for a plurality of edge devices in an organization. Relevant portions of the configuration information are transferred to subordinate databases associated with each of the edge devices. Each edge device may then manage policies for a network in the organization according to the configuration information in its database. 
     Any changes to the configuration information are made by the central policy server in the central database. The central policy server further creates a log of the changes, stores the log in the central database, and transfers the changes to the affected edge devices for updating their databases. 
     In one particular aspect of the invention, the central policy server maintains user logs and device logs for the changes. User logs associate the configuration changes to particular users making the changes (e.g. particular network administrators). Policy logs associate the configuration changes to particular edge devices affected by the changes. In creating the policy logs, the changes in the user logs are collected and filtered for each affected edge device and stored in the policy logs associated with the edge device for a later transfer to the edge device. 
     In another particular aspect of the invention, the central policy server receives a status of the transfer of the configuration changes from the affected edge devices. If the status indicates a successful transfer, the log of changes is deleted from the central database. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present invention will be more fully understood when considered with respect to the following detailed description, appended claims and accompanying drawings wherein: 
     FIG. 1 is a schematic block diagram of an exemplary unified policy management system; 
     FIG. 2 illustrates the hierarchical object-oriented structure of policies stored for an organization in accordance with the principles of the invention; 
     FIG. 3 is a schematic block diagram of a policy server in the policy management system of FIG. 1; 
     FIG. 4 is a schematic diagram of a central management sub-module in the policy server of FIG. 3; 
     FIG. 5 is an exemplary flow diagram of a device registration process carried out by the central management sub-module of FIG. 4; 
     FIG. 6 is a screen illustration of an exemplary graphical user interface for registering a device; 
     FIG. 7 is a screen illustration of an exemplary global monitor user interface presenting device health and status information; 
     FIG. 8 is a screen illustration of an exemplary graphical user interface provided by a policy management sub-module in the policy server of FIG. 3; 
     FIG. 9 is a screen illustration of an exemplary graphical user interface for managing system devices; 
     FIG. 10 is a screen illustration of an exemplary graphical user interface for managing system hosts; 
     FIG. 11 is a screen illustration of an exemplary graphical user interface for managing system services; 
     FIG. 12 is a screen illustration of an exemplary graphical user interface for managing time groups; 
     FIG. 13 is a screen illustration of an exemplary graphical user interface displaying a plurality of VPN clouds; 
     FIG. 14 is a screen illustration of an exemplary graphical user interface for adding a new firewall policy; 
     FIG. 15 is a schematic functional block diagram of policy enforcers updating their respective VPN membership information; 
     FIG. 16 is a block diagram of components in a self-extracting executable for downloading by a remote VPN client; 
     FIG. 17 is a functional block diagram for downloading the self-extracting executable of FIG. 16; 
     FIG. 18 is a schematic block diagram of a policy enforcer in the policy management system of FIG. 1; 
     FIG. 19 is a more detailed schematic block diagram of a policy engine in the policy enforcer of FIG. 18; 
     FIG. 20 is a more detailed schematic block diagram of a protocol classification engine of the policy enforcer of FIG. 18; 
     FIG. 21 is a more detailed schematic block diagram of an Internet protocol security engine in the policy enforcer of FIG. 18; 
     FIG. 22 is a schematic layout diagram of a common log format according to one embodiment of the invention; 
     FIG. 23 is a block diagram of an LDAP tree structure according to one embodiment of the invention; 
     FIG. 24 is a more detailed block diagram of a branch of the LDAP tree of FIG. 23; 
     FIG. 25 is a flow diagram for logging and propagating LDAP changes to policy enforcers; 
     FIG. 26 is a schematic block diagram of a high availability system including a primary unit and a backup unit; 
     FIG. 27 is a flow diagram of an exemplary status discovery process conducted by a high availability unit; 
     FIG. 28 is a flow diagram of a process for maintaining configuration information synchronized in the primary and backup units of FIG. 26; 
     FIG. 29 is an exemplary flow diagram of updating the primary and backup units of FIG. 26 when they are both functional; and 
     FIG. 30 is an exemplary flow diagram of updating the primary and backup units FIG. 26 when the primary is not functional. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     I. Unified Policy Management System Architecture 
     FIG. 1 is a schematic block diagram of an exemplary unified policy management system according to one embodiment of the invention. As illustrated in FIG. 1, private local networks  102 ,  104 , and  106  are all coupled to a public network such as the Internet  108  via respective routers (generally identified at  110 ) and Internet Service Providers (ISPs) (not shown). Also coupled to the public Internet  108  via the ISPs are web surfers  112 , dial-up network users  114 , servers providing unauthorized web sites  116 , email spammers  118  sending out unsolicited junk email, and remote VPN clients  140  seeking access to the private local networks  102 . 
     According to one example, local network  102  connects users and resources, such as workstations, servers, printers, and the like, at a first location of the organization, such as the organization&#39;s headquarters, and local network  104  connects users and resources at a second location of the organization, such as a branch office. Furthermore, local network  106  connects users and resources of a customer of the organization requiring special access to the organization&#39;s users and resources. Authorized dial-up network users  114  of the organization are respectively situated at remote locations from the first and second local networks, and also require special access to the organization&#39;s users and resources. Furthermore, web surfers  112  communicate with the organization&#39;s web server  120  over the public Internet  108  and access the organization&#39;s web site. 
     Local network  102  includes a policy server  122  for defining and managing network services and policies for the organization. The network policies are a set of rules and instructions that determine the network&#39;s operation, such as firewall, VPN, bandwidth, and administration policies. The firewall policies decide the network traffic that is to be allowed to flow from the public Internet  108  into the local networks  102 ,  104 , and the traffic that is to be blocked. The bandwidth policies determine the kind of bandwidth that is to be allocated to the traffic flowing through the local networks. The VPN policies determine the rules for implementing multiple site connectivity across the local networks. The administration policies decide the users that have access to administrative functions, the type of administrative functions allocated to these users, and the policy enforcers  124 ,  126  on which these users may exercise such administrative functions. The firewall, VPN, bandwidth, and administration policies for the entire organization are preferably stored in a policy server database  130  maintained by the policy server  122 . 
     Each local network  102 ,  104  also includes an edge device, referred to as a policy enforcer  124 ,  126 , for controlling access to the network. Each policy enforcer  124 ,  126  manages the network policies and services for the users and resources of their respective local networks  102 ,  104 , as permitted by the policy server  122 . Respective portions of the policy server database  130  are copied to the policy enforcer databases  132 ,  134  for allowing the policy enforcers to manage the network policies and services for the local networks  102 ,  104 . 
     According to one embodiment of the invention, the policy server  122  and policy enforcers  124 ,  126  may be implemented in a similar fashion as the FORT KNOX series of policy routers made by Alcatel Internetworking, Inc., of Milpitas, Calif. 
     II. Object Model for Network Policy Management 
     According to one embodiment of the invention, the policy server database  130  and policy enforcer databases  132 ,  134  are LDAP databases adhering to a unified hierarchical object oriented structure. The LDAP directory service model is based on entries where each entry is a collection of attributes referenced by a distinguished name (DN). Each of the attributes includes a type and one or more values. The type is typically a mnemonic string, such as “o” for organization, “c” for country, or “mail” for email address. The values depend on the type of attribute. For example, a “mail” attribute may contain the value “babs@umich.edu.” A “jpegPhoto” attribute may contain a photograph in binary JPEG/JFIF format. Additional details of the LDAP directory service model are defined in RFC 1777 “The Lightweight Directory Access Protocol” (W. Yeong, T. Howes, and Kille, Network Working Group, March 1995) and “LDAP Programming: Directory-enabled Applications with Lightweight Directory Access Protocol” (T. Howes, and M. Smith, Macmillan Technical Publishing, 1997), incorporated herein by reference. 
     The entries in the LDAP database are preferably arranged in a hierarchical tree-like structure reflecting political, geographic, and/or organizational boundaries. Entries representing countries appear at the top of the tree. Below them are entries representing states or national organizations. Below the states or national organizations may be entries representing people, organization units, printers, documents, and the like. 
     FIG. 2 is a schematic layout diagram of a unified hierarchical object oriented structure adhered by the policy server database  130  according to one embodiment of the invention. The policy enforcer databases  132 ,  134  adhere to a similar structure except for a few differences. For example, the policy enforcer databases preferably do not contain a policy server domain object  201  and related policy server objects, nor a policy domain object  240 . 
     As illustrated in FIG. 2, each object in the structure is preferably stored as an LDAP entry. At the top of the hierarchy is the policy server domain object  201  including various policy server resources and a plurality of policy domains objects (generally referenced at  204 ). Each policy domain object  240  is a grouping of policy enforcers that share common policies. Each policy domain object  240  includes a resource root object  200  and a group root object  202 . All policy management functions are preferably implemented in terms of the resource objects which include devices  204 , users  206 , hosts  208 , services  210 , and time  220 . Thus, a firewall policy may be defined by simply assigning the particular devices, users, hosts, services, and time applicable to the policy. The devices, users, hosts, and services are preferably organized in groups  212 ,  214 ,  216 , and  218 , respectively, having a group name, description, and member information for a more intuitive way of addressing and organizing the resources. 
     Users  206  are preferably associated with a user domain providing a secure and efficient means of authenticating the user. Each user domain has a single policy enforcer who is authorized to authenticate the user. Thus, user domains ensure that the authenticating agent is generally located in the same local network as the user. This helps eliminate the cost of network dependency or network latency during the user authentication process. It should be noted, however, that users may also constitute authorized dial-up users  114  and users from the customer network  106 . These users contact a remote authenticating agent which proxies the authentication back to the appropriate policy enforcer. 
     Hosts  208  are the various networks present in an organization. For instance, a particular LAN subnet may be specified as a host in the system. Hosts  208  are preferably organized based on their physical locations within the organization. A host&#39;s physical location is identified by the device (policy enforcer)  204  associated with the host. 
     Services  210  reflect the various services provided by the policy server  122 . Such services include, for example, multimedia streaming/conferencing, information retrieval, security and authentication, database applications, mail applications, routing applications, standard communication protocols, and the like. Attributes associated with each service preferably include a service name, description, type (e.g. HTTP, HTTPS, FTP, TELNET, SMTP, Real Networks, and the like), and group. 
     Devices  204  are the policy enforcers  124 ,  126  at the edge of a particular local network. Each device/policy enforcer preferably includes users  206  and a host/network  208  that is managed by the policy enforcer. 
     Time  220  is another dimension in controlling access to the network resources. Various time objects covering a range of times may be created and used in creating the firewall policies. 
     Similar to resources, network policies are also preferably defined in terms of objects for a more efficient and intuitive definition of the policies. Policies are defined by the administrators and implemented by the policy enforcers  124 ,  126  on the network traffic flowing between the public Internet  108  and the local networks  102  and  104 . 
     According to one embodiment of the invention, a policy object  222  includes a bandwidth policy  224 , firewall policy  226 , administration policy (not shown), and VPN policy  230 . The VPN policy  230  defines a security policy for the member networks and includes one or more VPN clouds  232 . Each VPN cloud  232  is an individual VPN or a group of VPNs defining a security policy group, which includes a list of sites  234  and users  236  who can communicate with each other. A site is preferably a set of hosts/networks physically located behind one of the policy enforcers  124 ,  126 . In other words, a site is a definition of a network, which includes the policy enforcer that is associated with it. The policy enforcers for the sites act as VPN tunnel endpoints once the hosts under the sites start communicating. These communications are governed by a set of rules  238  configured for each VPN cloud. The rules  238  may govern, among other things, VPN access permissions and security features such as the level of encryption and authentication used for the connectivity at the network layer. 
     The object oriented structure of FIG. 2 thus allows the network administrators to define policies in an intuitive and extensible fashion. Such policies may be defined by simply associating resources to the policies. This allows for a policy-centric management model where the administrator is given the impression that a single logical server provides the firewall, bandwidth management, and VPN services across the enterprise. The fact that the policy is enforced on individual policy enforcers in different locations is transparent to the administrator. 
     III. Policy-Based Network Architecture 
     FIG. 3 is a more detailed schematic block diagram of the policy server  122  according to one embodiment of the invention. The policy server  122  preferably includes a management module  302  that allows centralized control over the policy enforcers  124 ,  126  from a single console. The policy server  122  further includes a log collecting and archiving module  304  and a policy server reports module  316 . The log collecting and archiving module  304  collects information about the status and usage of resources from the policy enforcers  124 ,  126  as well as from the management module  302 , and stores them in an archive database  318 . The policy server reports module  316  uses the collected logs and archives to generate reports in an organized report format. 
     Referring again to the management module  302 , the management module  302  preferably includes four sub-modules aiding in the centralized control, namely, a centralized management sub-module  306 , policy management sub-module  308 , secure role-based management sub-module  310 , and multiple site connectivity management sub-module  312 . 
     The centralized management sub-module  306  enables a network administrator to install and manage individual policy enforcers from a central location. The network administrator preferably uses a web-based graphical user interface to define the policy enforcer&#39;s network configuration and monitor various aspects of the device, such as device health, device alarms, VPN connection status, and the like. 
     The policy management sub-module  308  provides the network administrator with the ability to create policies that span multiple functional aspects of the policy enforcer (e.g. firewall, bandwidth management, and virtual private networks), multiple resources (e.g. users, hosts, services and time), and multiple policy enforcers. 
     The secure role-based management sub-module  310  provides role-based management to enable administrators to delegate administrative responsibilities to other administrators. This sub-module preferably provides for maximum security when it comes to accessing the management functions. 
     The multiple site connectivity management sub-module  312  allows the network administrator to set-up secure communication channels between two or more remote sites. In doing so, this sub-module leverages the centralized management sub-module  306 , policy management sub-module  308 , dynamic routing capabilities of the policy enforcers  124 ,  126 , and the management infrastructure to provide virtual private networks across the enterprise with fine grained access control. 
     FIG. 4 is a more detailed schematic diagram of the central policy management sub-module  306  according to one embodiment of the invention. The sub-module includes a policy server installation wizard  404  providing an interactive user interface to aid the installation of the policy server  122 . In this regard, the network administrator has access to a personal computer connected to a LAN port of the policy server  122  via a cross over cable, hub, or the like. The network administrator connects to the policy server  122  by preferably typing-in a URL of the policy server  122  into a standard Internet browser such as Microsoft Internet Explorer. The URL is preferably of the form of “http://&lt;ipaddress&gt;:88/index.html” where &lt;ipaddress&gt; is the IP address that is to be assigned to the policy server. The IP address is automatically assigned to the policy server when the browser attempts to contact the address. When the administrator&#39;s personal computer sends an address resolution protocol request for the IP address, the policy server detects that a packet directed to port  88  is not claimed, and assumes the IP address. 
     Once connected, the policy server installation wizard  404  invokes the interactive user interface to assist the administrator in setting up the policy server  122 . Among other things, the policy server installation wizard  404  prompts the administrator to specify a server name, server IP address, and router IP address. Furthermore, the policy server installation wizard  404  prompts the administrator to select one of various default policies for creating default firewall, VPN, bandwidth, and administrator policies. These policies are then replicated on each new policy enforcer registering with the policy server  122 . 
     The centralized management sub-module  306  further includes a policy enforcer installation wizard  406  providing an interactive user interface to aid the installation of the policy enforcers  124 ,  126 . As with the installation of the policy server  122 , the access to the wizard  406  is preferably web-based using the network administrator&#39;s personal computer. 
     Once connected, the policy enforcer installation wizard  406  invokes the interactive user interface to assist the network administrator in setting up a particular policy enforcer  124 ,  126 . Among other things, the policy enforcer installation wizard  464  prompts the administrator to specify the policy server IP address, policy enforcer IP address, and router IP address. The policy enforcer then registers with the policy server  122  by invoking a URL on the policy server with basic bootstrap information of its own. The registration of the policy enforcer allows the initialization of the policy enforcer&#39;s database  132 ,  134  with the configuration information, as well as the monitoring of the policy enforcer&#39;s status and health by the policy server  122 . 
     Prior to registering the policy enforcer with the policy server  122 , the network administrator preferably pre-registers the policy enforcer on the policy server. Such pre-registering allows the creation of a placeholder node on the policy server for the policy enforcer data for when the policy enforcer does in fact register. In this regard, the centralized management sub-module  306  includes a configuration interface  410  allowing the pre-registration of a new policy enforcer. 
     FIG. 5 is an exemplary flow diagram of a policy enforcer pre-registration and registration process according to one embodiment of the invention. In step  401 , the policy enforcer is connected to the network and installed at its actual physical location using the above-described policy enforcer installation wizard  406 . The network administrator, possessing the new device&#39;s serial number, pre-registers the policy enforcer by adding the new policy enforcer to a device group in step  403 . In this regard, the configuration interface  410  invokes an interactive graphical interface, such as the one illustrated in FIG. 6, allowing the network administrator to enter a device name  415 , serial number  417 , and location information  419 , and further allowing the administrator to select a device group  421  to which the new policy enforcer is to belong. Actuation of an apply button  423  causes the new policy enforcer, in step  405 , to contact the policy server  122  by preferably invoking a URL on the policy server. Once the policy server has been contacted, the new policy enforcer transmits its registration packet to the policy server. The registration packet includes at least a serial number of the new policy enforcer, as well as the IP addresses of the LAN, WAN, and DMS on the policy enforcer. In step  407 , the centralized management sub-module  306  compares the serial number of the new policy enforcer with the list of policy enforcers pre-registered with the policy server  122 . If a match is found, the policy server  122  proceeds with the registration process by packaging, in step  409 , the settings selected for the policy enforcer during its installation process, preferably into an LDAP Data Interchange Format (ldif) file. In step  411 , the file is transmitted to the policy enforcer, preferably over an HTTPS channel, by invoking a common gateway interface (CGI) on the policy enforcer. The policy enforcer then uses the file to initialize its configuration database, such as database  132 ,  134 , in step  413 . 
     Referring again to FIG. 4, the centralized management sub-module  306  also includes a global monitor user interface  402  and a data collector program  412 , respectively displaying and collecting the health and status of all the policy enforcers managed by the policy server  122 . The data collector program  412  receives health and status information from each of the up-and-running policy enforcers it manages, and passes the relevant information to the global monitor user interface. A health agent running as a daemon in each of the policy enforcers being monitored periodically collects data from the device and analyzes its health status. The collected data is then transferred to the policy server  122  when requested by the data collector program  412 . 
     FIG. 7 is a screen illustration of an exemplary global monitor user interface  402  presenting various types of health and status information. Such information may relate to the health of the device, such as system load  712  and network usage information  714 . The information may also relate to current alarms  716  on the device including alarm name, type, description, and the like. The information may further relate to current VPN connections  718  including connection type, source/destination, duration, and VPN traffic volume. 
     Referring again to FIG. 3, the policy management sub-module  308  allows for policy management of the policy enforcers  124 ,  126 . As discussed above, all policy management functions are implemented in terms of resource objects stored in the policy databases  130 ,  132 ,  134  including users, devices, hosts, services, and time. Preferably, all resources are associated with default policy settings selected by the administrator during the installation process. The network administrator views, adds, and modifies the policies centrally via a graphical user interface provided by the policy management sub-module  308 . This allows for a policy-centric management model where the administrator is given the impression that a single logical server provides the firewall, bandwidth management, and VPN services across the enterprise. The fact that the policy is enforced on individual policy enforcers in different locations is transparent to the administrator. 
     FIG. 8 is a screen illustration of an exemplary graphical user interface provided by the policy management sub-module  308 . The interface includes a resource palette  718  including a list of resource tabs including a users tab  718   a , devices tab  718   b , hosts tab  718   c , services tab  718   d , and time tab  718   e . The resource palette allows the administrator to add and modify resource definitions from a single console. 
     Selection of the users tab  718   a  causes a display of the user groups  722  defined for the system. New users may be added to the group by selecting a particular group and defining various attributes of the user such as a login name, full name, policy enforcer to which the user belongs, authentication scheme, password, and the like. 
     Selection of the devices tab  718   b  causes a display of various device management icons for managing the policy server  122  and the policy enforcers  124 ,  126  as is illustrated in FIG. 9. A policy server systems settings icon  750  allows the network administrator to view and modify system settings like LAN, WAN/DMS IP addresses of the policy server  122 . A policy server archive options icon  752  allows specification of reporting and other database archive options at the policy server  122 . A global URL blocking icon  754  allows the administrator to specify a list of unauthorized web sites  116  to be blocked by all the policy enforcers  124 ,  126  of the system. Similarly, a global spam list icon  756  allows the administrator to specify a list of email addresses of spammers  118  to be blocked by all the policy enforcers. 
     The administrator may view information on all the policy enforcers  124 ,  126  by selecting icon  758 . Information on a specific policy enforcer may be viewed by selecting a specific policy enforcer  760  under a particular device group  761 . Such information includes system settings information  762 , URL blocking information  764 , spam list information  766 , and the like, that is specific to the selected policy enforcer. For instance, selection of the policy enforcer&#39;s URL blocking information  764  icon causes a display of various categories  768  of URLs that the network administrator may select to block for the selected policy enforcer. 
     Selection of the hosts tab  718   c  causes a display of various hosts (networks) of the system as is illustrated in FIG. 10. A host is organized based on its physical location and is further associated with a particular policy enforcer  124 ,  126 . Hosts are associated with various attributes including a unique name  770 , an IP address of the network  772 , and a subnet mask  774 . In addition, the administrator may specify whether the host is an external host  776  belonging to a network that is not administered by the policy server  122 . If the host is an external host, the administrator specifies an IP address  778  of the external device to which the host belongs. A device field  780  allows the administrator to enter the policy enforcer&#39;s name to which the host belongs. Each host is further associated with a particular group  782  assigned by the administrator. 
     Selection of the services tab  718   d  causes a display of various service groups supported by the policy server  122  as is illustrated in FIG.  11 . Such service groups include, for example, multimedia streaming/conferencing, information retrieval, security and authentication, mail applications, routing applications, database applications, standard communication protocols and the like. Users may also add new service groups as desired. 
     Each service is associated with a name  784 , description  786 , and service type  788  (e.g. HTTP, HTTPS, FTP, TELNET, SMTP, Real Networks, and the like). Furthermore, each service is associated with a service group  790 . Based on the type of service, additional information may also be specified for the service. For instance, for an HTTP service, the administrator may specify whether URL blocking  792  is to be enabled. 
     Selection of the time tab  718   e  causes a display of various time group icons  794  covering a range of times to be used in the firewall policies as is illustrated in FIG.  12 . For instance, selection of a work time group icon allows the network administrator to set the days and times which are to be set as working days and hours. 
     Referring again to FIG. 8, the interface also includes a policy canvas  720  including a list of policies available to the system. A policy definition is preferably an association of a set of resources that may be dragged from the resource palette  718  and dropped onto the policy canvas  720 . 
     Selection of a firewall tab  720   a  causes a display of all the firewall policies defined for a particular policy domain including one or more policy enforcers. The network administrator decides the domain to which a policy enforcer is to belong during pre-registration of the policy enforcer. The interface allows the network administrator to view, add, and modify the various policies from the policy server  122  and effectuate the changes on the policy enforcers  124 ,  126  without the need to make such changes individually in each policy enforcer. 
     According to one embodiment of the invention, each firewall policy includes a policy identifier (ID) attribute  724  for identifying a particular policy rule in the list of policies. An order number attribute  726  for the policy rule indicates the sequence in which the policy is to be applied. In this regard, the policy enforcer  124 ,  126  for the local network takes one rule at a time, in sequence, compares it against the network traffic, and preferably applies the first rule that matches the network traffic. 
     Each firewall policy also includes a description attribute  728  for describing the firewall policy to be applied. For instance, the description may indicate that the policy allows spam blocking, URL blocking, VPN key management, and the like. An action flag attribute  730  indicates whether traffic is to be allowed or denied for the indicated policy. An active flag attribute  732  indicates whether the policy has been activated or de-activated. Thus, the network administrator may create a policy and activate it at a later time. A policy that has been de-activated preferably has no effect on the network traffic. 
     Each firewall policy further includes a user attribute  734 , source attribute  736 , service attribute  738 , destination attribute (not shown), and time attribute (not shown). Each of these attributes is preferably represented by a group name or a resource name. The name acts as a pointer to an entry in the group root object  202  or resource root object of the LDAP database  130 ,  132 , or  134 . 
     Preferably, the user attribute  734  indicates the user groups and users that are eligible for the policy. The source attribute  736  indicates a point of origination of the network traffic associated with the user. The service attribute  738  indicates the services to be allowed or denied by the policy. The destination attribute indicates a specific LAN, WAN, DMS segment or specific hosts where the specified services are to be allowed or denied. For example, to configure SMTP pop services on a mail server, the host may be the IP address where the mail server is running, and the services specified is SMTP. The time attribute indicates a time slot in which the policy is to be effective. 
     In addition to the above, each firewall policy also includes an authentication attribute (not shown) indicating an authentication scheme for the policy (e.g. none, LDAP, SecurID, RADIUS, WinNT, or all). 
     FIG. 14 is a screen illustration of an exemplary graphical user interface for adding a new firewall policy to the policy domain upon actuation of an add button  725 . Existing firewall policies may also be modified or deleted by actuation of a modify button  727  and a delete button  729 , respectively. 
     As illustrated in FIG. 14, a new firewall policy may be defined by simply adding a description of the policy in a description area  728   a , selecting an action to be applied to the matching network traffic in an action box  730   a , and indicating in an active area  732   a  whether the policy is to be active or inactive. Furthermore, the network administrator specifies the user, source, services, destination, and time resources in a user area  734   a , source area  736   a , services area  738   a , destination area  739   a , and time area  741 , respectively. The network administrator further selects an authentication scheme for the policy in an authentication area  743 . Upon actuation of an OK button  745 , appropriate entries of the policy server database&#39;s LDAP tree are suitably changed to reflect the addition of the new policy. The change is also transmitted to the respective policy enforcers as is described in further detail below. 
     Referring again to FIG. 8, selection of the bandwidth tab  720   c  allows the display, addition, and modification of various bandwidth policies determining the kind of bandwidth to be allocated to a traffic flowing through a particular policy enforcer. Different bandwidths may be specified for different users, hosts, and services. 
     Selection of the administration tab  720   d  allows the display, addition, and modification of various administrative policies allowing a head network administrator to delegate administrative responsibilities to other administrators. In this regard, the head network administrator specifies administration policies that determine which users have access to what functions, and for what devices. Preferably the administration policies include similar attributes as the firewall rules except for the specification of a role attribute. Extra administrative privileges may be afforded to certain users depending on their role. 
     IV. Virtual Private Network Having Automatic Reachability Updating 
     Referring again to FIG. 3, the multi-site connectivity management module  312  allows the creation of dynamically routed VPNs where VPN membership lists are automatically created without statically configuring the membership information by the network administrator. Thus, once the administrator configures a VPN from one policy enforcer&#39;s LAN to another, routing protocols such as RIPv1 or RIPv2 running on the LAN interfaces learn about the networks reachable through their respective interfaces. These networks then become the VPN&#39;s members, and the policy enforcers  124 ,  126  on either side of the VPN create membership tables using the learned routes. The membership information is preferably exchanged between the policy enforcers  124 ,  126  through the LDAP databases  132 ,  134 . Thus, the combined use of routing protocols and LDAP allows the creation of VPNs whose member lists are dynamically compiled. 
     Referring again to FIG. 8, the network administrator configures VPN policies for multiple site connectivity using the resource palette  718  and policy canvas  720 . Selection of the VPN tab  720   b  in the policy canvas  720  causes the display of a collection of VPN clouds  270  already configured for the system as is illustrated in FIG.  13 . As described above, a VPN cloud is an individual VPN or a group of VPNs for which a security policy may be defined. Each VPN cloud includes a list of sites under a sites node  234  and users under a users node  236 , who can communicate with each other. A site is a set of hosts that are physically behind one of the policy enforcers  124 ,  126 . The policy enforcers for the sites preferably act as VPN tunnel endpoints once the hosts under the sites start communicating. 
     The users in the VPN cloud are the users who may access the hosts associated with the sites  234 . The users access the hosts as VPN clients using VPN client software installed in each user&#39;s personal computer as is described in further detail below. 
     Each VPN cloud  270  further includes a firewall rules node  276  including firewall rules to be applied to all the connections in the cloud. The rules may govern, among other things, VPN access permissions, security features such as the level of encryption and authentication used for the connectivity at the network layer. 
     The hierarchical organization provided by the VPN clouds thus allows the network administrator to create fully meshed VPNs where every site within a VPN cloud has full connectivity with every other site. The network administrator need no longer manually configure each possible connection in the VPN, but only need to create a VPN cloud and specify the sites, users, and rules to be associated with the VPN. Each connection is then configured based on the configuration specified for the VPN cloud. The hierarchical organization thus facilitates the setup of a VPN with a large number of sites. 
     The network administrator preferably adds a new VPN cloud by actuating an add button  280 . In response, the policy server  122  automatically creates the sites node  272 , users node  274 , and rules node  276  under the VPN cloud. The administrator then specifies the sites and users in the VPN. 
     According to one embodiment of the invention, the rules node  276  initially includes a default VPN rule  278  corresponding to the policy settings selected by the network administrator during setup of the policy server  122 . The default VPN rule  278  allows unrestricted access between the hosts in the VPN. 
     The administrator may implement the access control within the VPN cloud by deleting the default rule  278  and adding specific firewall rules to the VPN. Such firewall rules allow the administrator to have fine grained access control over the traffic that flows through the VPN, all within the realm of the encrypted access provided by such VPN. The firewall rules are applied to the cleartext packet after it is decrypted or before it is encrypted. 
     According to one embodiment of the invention, the administrator selects the default rule  278  to effectuate such changes to the default rule. Selection of the default rule invokes a graphical user interface similar to the one illustrated in FIG.  8 . The network administrator then fine tunes the access to the VPN by defining the firewall rules applicable to the VPN. The parameters in these firewall rules are preferably identical to the general firewall rules illustrated in FIG.  8 . 
     Once a VPN cloud is configured, VPN membership information is dynamically created by the policy enforcers  124 ,  126  in the VPN. In this regard, each VPN site includes a tag identifying the hosts included in the site. At runtime, the policy enforcers  124 ,  126  for the respective sites associate IP addresses to the tag identifying the hosts in each site. This allows the IP addresses to be dynamically discovered without requiring static configuration of the IP addresses. 
     After the creation of the membership tables, any changes in the routing information is detected and notified to the member policy enforcers using a publish/subscribe process. The actual changes are retrieved by a policy enforcer by querying the LDAP database on the particular network that corresponds to the changed routing information. 
     FIG. 15 is a schematic functional block diagram of policy enforcers  124 ,  126  at opposite ends of a VPN tunnel updating their respective routing information. As illustrated in FIG. 15, each policy enforcer  124 ,  126  includes a gated module  252 ,  261  configured as a daemon to run one or more routing protocols for exchanging routes on the network. Such routing protocols may include RIPv1, RIPv2, OSPF, and the like. 
     When a network administrator wishes to add a new route to the private local network  102  connected to policy enforcer  124 , the administrator submits, in step  241 , the new route to a gated module  252  in the policy enforcer  124 . This is typically done by configuring a downstream of the policy enforcer to have an additional network. This information is then propagated by standard routing protocols to the gated module  252  of the policy enforcer  124 . For example, the policy server  122  may publish the new route to the policy enforcer  124  with which the new route is to be associated. The route may be specified, for example, by an LDAP statement such as “LAN_Group@PR1,” which specifies a new route from a policy enforcer PR1 to a LAN named LAN_Group. The gated module  252 , in step  242 , writes the new route to a kernel  253  of the policy enforcer including a VPN driver  254  so that the policy enforcer  124  can properly direct appropriate messages along the new route. Furthermore, the gated module  252 , in step  243 , writes the new route to its LDAP database  132 . 
     The gated module  252  also provides, in step  244 , the name of the new route to a distinguished name monitor (DNMonitor) daemon  255  configured to listen for updates in the LDAP database  132 . The DNMonitor in turn notifies, in steps  245   a ,  245   b , a VPN daemon  256  and a policy deployment point (PDP) engine  257  of the change in the LDAP database  132 . The PDP engine then updates the modules that enforce the policies, with the change. 
     The VPN daemon  256 , in step  246 , uses the route name to access the LDAP database  132  to get the complete route information, a list of all VPNs to which the new route belongs, and a list of all other policy routers connected to those VPNs. In step  247 , the VPN daemon  256  proceeds to send the new route name to each of the other policy routers. 
     When policy router  126  receives a new route name from policy router  124 , its network daemon  258 , in step  248 , accesses the LDAP database  132  in the sending policy router  124  to obtain the complete new route information. If the new route belongs to more than one VPN and has different parameters for the different VPNs, routers on the different VPNs retrieve different information corresponding to the individual VPNs. 
     In step  249 , the network daemon  258  writes the new route information obtained in its own LDAP database  134  and provides it to its own DNMonitor module. As in the sending policy router  124 , the DNMonitor module  259  in the receiving policy router  126  provides the new route information to its PDP engine  260  for updating its kernel  262  with the latest changes. 
     Although FIG. 15 has been described in connection with addition of a route to a policy enforcer and its associated VPNs, it should be readily apparent to those skilled in the art that essentially the same techniques may be applied to deletion of a route (for example, if a network component becomes inoperative or incommunicative), or change of a route (the policy router may recognize that a route already exists in a different form and simply overwrite it). In this way, the VPN system or systems can dynamically maintain routing information between its policy enforcers with minimal intervention by the system administrator. 
     V. Virtual Private Network Having Automatic Updating of Client Reachability Information 
     Remote users communicate over the public Internet  108  with the other members of the VPN behind policy enforcers  124 ,  126 , upon presenting appropriate credentials. These remote users access the private networks as VPN clients  140  using a VPN client software. According to one embodiment of the invention, the system allows the remote user to download a self-extracting executable which, upon execution, installs both the VPN client software and VPN reachability information unique to the remote user in the user&#39;s remote terminal. 
     Each policy enforcer  124 ,  126  preferably maintains a copy of the self-extracting executable of the VPN client software including a setup program and VPN reachability configuration template. The setup program allows the VPN client software to be installed on the VPN client  140 . When downloading the self-extracting executable, the configuration template is replaced with the VPN reachability information that is specific to the downloading user. 
     According to another embodiment of the invention, the system allows the VPN client  140  to download a self-extracting executable which, upon execution, only installs the VPN reachability information that is unique to the user. According to this embodiment, the VPN client software is already installed on the VPN client  140 . In this scenario, the setup program allows the installation of the reachability information that is specific to the downloading user, on the VPN client  140 . 
     According to a third embodiment of the invention, the system allows the VPN client  140  to automatically download the VPN reachability information each time it connects to the policy enforcer  124 ,  126 . Thus, VPN reachability information is kept up-to-date for each VPN client  140 . Once a VPN session is established, the connection between the VPN client  140  and the policy enforcer is assumed to already be secure. The VPN client preferably makes a common gateway interface (CGI) query to a web server running on the policy enforcer, and downloads the current VPN reachability information from the corresponding LDAP database. 
     FIG. 16 is a block diagram of components in a self-extracting executable  290  according to one embodiment of the invention. The self-extracting executable  290  may be created using commercially available tools such as the INSTALLSHIELD EXEBUILDER of InstallShiled Software Corporation of Schaumburg, Ill. 
     The self-extracting executable  290  preferably includes an executable setup file  292  for installing the VPN client software and/or the VPN configuration information. The setup file  292  preferably forms a static portion  298  of the self-extracting executable since this information does not change based on the downloading VPN client. The self-extracting executable  290  further includes VPN configuration file templates for the VPN reachability information  294  and the VPN client&#39;s preshared key information  296 . The VPN reachability information  294  and the VPN client&#39;s preshared key  296  preferably form a dynamic portion  299  of the self-extracting executable  290  since this information changes based on the downloading VPN client. The self-extracting executable  290  is then saved as a template file in the policy enforcers  124 ,  126  and is ready to be downloaded by the remote users. 
     FIG. 17 is a functional block diagram for downloading the self-extracting executable  290  of FIG. 16 according to one embodiment of the invention. In step  320 , a new VPN client  140  first establishes a secure communication session with the policy enforcer  124 ,  126  to download the self-extracting executable  290 . Preferably, this is accomplished via an HTTPS protocol session on the VPN client&#39;s web browser or the like. In steps  322  and  324 , the policy enforcer engages the VPN client in an authentication procedure where the policy enforcer requests, and the VPN client provides, his or her user name and password. In step  326 , the policy enforcer compares the provided information with entries in its VPN client database  328 . If the information is correct, the policy enforcer finds appropriate preshared keys for the user, and in step  330 , also determines the VPN reachability information of the client from a VPN configuration database  332 . The VPN client database  328  and VPN configuration database  332  may reside as part of a single LDAP database  312 ,  314  managed by the policy enforcer  124 ,  126 , or may constitute separate LDAP databases. 
     In step  334 , the policy enforcer replaces the dynamic portion  299  of the self-extracting executable  290  with the VPN reachability information and preshared key that is unique to the VPN client. The newly generated self-extracting executable is then downloaded to the VPN client  140  in step  336 . When the executable is run, it either installs the VPN client software and/or the VPN reachability information. 
     Similar techniques may also be used for downloading a new and updated copy of the VPN configuration information to the VPN client each time the client connects to the policy enforcer and negotiates a session key. In addition, the user may obtain the latest configuration of the VPN network by expressly requesting the policy enforcer for such information. Thus, the VPN client need not be reinstalled and reconfigured each time updates are made to the VPN reachability information. 
     VI. Integated Policy Enforcer 
     According to one embodiment of the invention, the functionalities of the policy enforcer  124 ,  126  for policy enforcement are partitioned for effective hardware implementation. However, it should be apparent to one skilled in the art that some or all of the functionalities may be implemented in software, hardware, or various combinations thereof. 
     FIG. 18 is a schematic block diagram of the policy enforcer  124 ,  126  illustrating the partitioning of the various functionalities according to one embodiment of the invention. The policy enforcer includes an Internet protocol security (IPSec) engine  502  for performing security and authentication functions in implementing, for instance, virtual private networks. A stream table  506  assembles the packets passing through the policy enforcer into streams. A protocol classification engine  508  decodes the protocols used in forwarding the packets. A policy engine  510  enforces policies for the packets based on the policy settings stored in the policy database  132 ,  134 . A packet forwarding module  504  receives packets from the public Internet via the router  110  and buffers, forwards, or drops the packets based on the policies being enforced. A bandwidth management module  514  provides bandwidth shaping services to the packets being forwarded based on the bandwidth settings stored in the policy database  132 ,  134 . 
     In practice, an incoming packet is matched against the stream table  506  for determining if a matching entry already exists in the table. If not, a new entry is added. The stream table preferably includes enough portions of the packet to uniquely identify a stream. For example, in enforcing policies on IP layer three through layer four traffic, the stream table may store a source IP, destination IP, source port, destination port, and protocol number of the incoming packet. 
     The protocol classification engine  508  takes the new stream and obtains a detailed protocol decode for the stream. The policy engine  510  is then queried for the policy rules to be applied to the stream. Based on the policy rules returned by the policy engine  510 , the packet forwarding module  504 , IPSec engine  502 , and/or the bandwidth management module  514  process the streams accordingly. The processing may be recursive until the packets in the stream have had all the actions specified by the policy rule set applied to them. 
     The policy enforcer also includes a statistics module  512  for collecting statistics on the packets forwarded through the local network as well as other status and resource usage information, and provides the same in logs and archives for sending to the policy server  122 . According to one embodiment of the invention, the statistics module  512  keeps running byte counts of the packets passing through the network  102 ,  104 . These byte counts may be automatically sorted by classes, such as classes based on certain resources (e.g. users, hosts, services), as well as by bytes that are blocked by policies and exceptions, such as firewall policies. In this regard, the statistics module  512  maintains in a cache a state table including a list of resources involved for each connection allowed through the firewall. For every packet flowing through the connection, the statistics module increments the packet and byte count for each of the resources in the list. The statistics module  512  then forwards the organized information to the policy server  122  which enters the information directly into tables organized by classes and aged out periodically. 
     FIG. 19 is a more detailed schematic block diagram of the policy engine  510  according to one embodiment of the invention. The policy engine  510  includes a policy request table  602  that acts as a queue for all the policy decision requests. In this regard, the portion of the packet matching the information stored in the stream table  506  is presented to the policy engine  510  in the form of a policy request. The policy request is then queued in the policy request table  602 . 
     A resource engine  604  maintains an up-to-date mapping of resource group names to member mappings. A policy rules database buffer  608  stores a current policy rule set to be applied by the policy engine  510 . The policy rules stored in the buffer  608  are preferably in the original group-based rule specification format. Thus, the buffer  608  stores a rule created for a group in its group-based form instead of instantiating a rule for each member of the group. 
     A decision engine  606  includes logic to serve the incoming policy decision requests in the policy request table  602  by matching it against the policy rule set in the policy rules database buffer  608  based on the actual membership information obtained from the resource engine  604 . The relevant group-based rule matching the traffic is then identified and decision bits in the stream table set for enforcing the corresponding actions. The decision bits thus constitute the set of actions to be performed on the packets of the stream. All packets matching the streams are then processed based on these decision bits. The decision engine may also specify an access control list (ACL) including a set of rules that allow/deny traffic, a DiffServ standard for providing a quality of service level to the traffic, and/or VPN implementation information. 
     FIG. 20 is a more detailed schematic block diagram of the protocol classification engine  508  according to one embodiment of the invention. As illustrated in FIG. 20, the protocol classification engine  508  includes a stream data assembly  702 , a sliding stream data window  704 , an ASN.1 block  706 , a protocol classification state machine  708 , and a protocol definition signature database  710 . The stream data assembly  702  extracts and re-assembles the data portion of an input packet stream and stores it in the sliding stream data window  704 . Preferably, the sliding stream data window follows first-in-first-out protocols. The ASN.1 decoder further decodes the data stream, if needed, per conventional ASN.1 encoding/decoding standards. The protocol classification state machine  708  then matches the fully re-assembled and decoded data against the protocol definition signature database  710 . This database  710  preferably holds a mapping of protocol names to data patterns to be found in the data stream. The matched protocol is then returned to the stream table  506 . 
     Thus, the protocol classification engine  508  provides extensive layer three through layer seven protocol decode and packet classification, including complete identification of dynamic streams using a dynamically updated signature database compiled from scripted protocol definitions. As new protocols are defined in the future and/or users create their own custom applications with custom protocols, a need may arise to add recognition of these protocols to the protocol classification engine. The described protocol classification engine architecture allows such additions by simply adding a new scripted definition of the new protocol to the protocol classification engine without having to change the design each time a new protocol is added. This allows for custom protocol support and future protocol extensibility. 
     FIG. 21 is a more detailed schematic block diagram of the IPSec engine  502  according to one embodiment of the invention. As illustrated in FIG. 21, the IPSec engine  502  includes a Pseudo-Random Number Generator (PRNG) function  802  for generating random numbers used for cryptographic key generation according to well known methods. A Diffie Hellman  804  and RSA  812  blocks implement the corresponding asymmetric public key encryption/decryption/signature algorithms which are also well known in the art. An IKE block  806  communicates with an IPSec SA table  808  for implementing standard ISAKMP/Oakley(IKE) key exchange protocols. A cryptographic transforms block  814  implements standard symmetric encryption/decryption algorithms. An IPSec Encapsulation/Decapsulation block  810  performs standard encapsulation/decapsulation functions. Accordingly, the IPSec engine  502  provides mature, standards-based IKE/IPSec implementation with public key certificate support and necessary encryption/decryption functionality for packets passing through the private local networks  102 ,  104 . 
     VII. Network Policy Logs and Statistics Aggregation 
     Referring again to FIG. 3, the log collecting and archiving module  304  collects information about the status and usage of resources from the policy enforcers  124 ,  126  as well as from the management module  302 , and stores them in the archive database  318 . The policy server reports module  316  then uses the collected logs and archives to generate reports in an organized report format. 
     According to one embodiment of the invention, each policy enforcer  124 ,  126  maintains a log file with information collected about the flow of traffic through the policy enforcer as well as the status and usage of resources associated with the policy enforcer. All the log files follow a predefined common log format, preferably designed to create compact logs. 
     FIG. 22 is a schematic layout diagram of such a log format according to one embodiment of the invention. Each log entry includes a timestamp  820  in the format yyyymmddhhmmss, indicative of the year, month, date, hours, minutes, and seconds in which the log entry was created. A service field  822  indicates the type of service rendered by the policy enforcer  124 ,  126 . Such services include VPN, FTP, Telnet, HTTP, packet filter, bandwidth, and the like. Each log entry further includes a source IP address and port  824  indicating the source from where a packet was received, as well as a destination IP address and port  826  indicating the destination to which the packet was forwarded. 
     A user ID field  828  identifies the user transmitting the packet. The user ID may be mapped to an entry in the LDAP database  130 ,  132 , or  134  for obtaining additional details about the user. 
     A status field  830  indicates the status of an operation and may include a result code, error code, and the like. For example, for a packet filter service, the status field may include a result code “p” if the packet was passed or code “b” if the packet was blocked. 
     An operation field  832  indicates codes for a type of operation conducted by the service. For instance, operations for a VPN service may include sending packets and receiving packets. Operations for an FTP service may include GET and PUT operations. Operations for an HTTP service may include GET and POST operations. 
     In addition to the above, each log entry includes an in-bytes field  834  indicative of the number of bytes the policy enforcer received as a result of the activity, and an out-bytes field  836  indicative of the number of bytes transferred from the policy enforcer. Furthermore, a duration field  838  indicates the duration (e.g. in seconds) of the activity. 
     Certain fields of a particular log entry may be left blank if not applicable to a particular service. For instance, for an FTP download. Where there is no outgoing traffic, the out-bytes field is left blank. Furthermore, additional fields may be added based on the type of service being logged. For instance, for an HTTP activity, the URL that is accessed is also logged in the log entry. The additional fields are preferably appended to the end of the standard log format. 
     A person skilled in the art should recognize that additions, deletions, and other types of modifications may be made to the log format without departing from the spirit and the scope of the invention as long as the log format is common to all the policy enforcers and is aimed in creating compact logs. 
     The log files created by the policy enforcers  124 ,  126  are transferred to the policy server  122  based on archive options set by the policy server. In this regard, the network administrator specifies a threshold size for the logs created by the policy enforcers upon selection of the policy server archive option  752  of FIG.  9 . When the log file exceeds the specified size, it is sent to the policy server  122 . Preferably, the logs are transferred to the policy server  122  at least once a day even if the threshold size has not been exceeded. The logs may also be archived locally at the policy enforcer if so specified by the network administrator. 
     Once the policy server  122  receives the logs, it is stored in the archive database  318  preferably taking the form of an SQL database. The policy server reports module  316  queries this database to generate reports for each policy enforcer  124 ,  126 . In addition, the logs may be exported in a format that may be interpreted by commercially available products such as WEBTRENDS, manufactured by WebTrends Corporation of Portland, Oreg. 
     The reports created by the reports module  316  include summary usage reports for the various resources including policy enforcers, users, services, hosts, and VPNs. For instance, the reports may include VPN summary reports, bandwidth summary reports, packet filter reports, and the like, for each policy enforcer. 
     The reports preferably show usage of each of the resources over a period of time. The start and the end date for the report may be specified by the user. The user may further drill down on the time dimension and on the resource dimension for viewing specific times and specific resources. For instance, in creating the packet filter reports, the user may indicate a start and end time, source IP address, source port, destination IP address, and destination port. All packets meeting these criteria are then fetched from the archive database  318  and shown in a packet report. 
     VIII. Method for Selective LDAP Database Synchronization 
     According to one embodiment of the invention, the databases  130 ,  132 ,  134  in the unified policy management system of FIG. 1 are LDAP databases storing policy management information including policies for firewall, VPNS, bandwidth, administration, user records, network records, services, and the like. As described above, the LDAP directory service model is based on entries where each entry is a collection of attributes. Entries are arranged in a tree structure that follows a geographical and organizational distribution. Entries are named according to their position in the hierarchy by a distinguished name (DN). 
     The policy server  122  preferably stores the policy management information for all the policy enforcers in the policy server database  130 . This information is organized in the databases  130  as one or more DNs with corresponding attributes. Appropriate portions of the policy server database are then copied to the policy enforcer databases  132 ,  134 . 
     FIG. 23 is a block diagram of an LDAP tree structure including an LDAP root  265  and a plurality of branches  264 ,  266 ,  268 ,  270 . According to one example, the policy server  122  maintains in the policy server database  130  branches  264  and  266  with policy management information for all the policy enforcers  124 ,  126 . Each of the policy enforcers  124 ,  126  also maintain portions of the branches  264  and/or  266  in their respective policy enforcer databases  132 ,  134  as sub-trees of the policy server database  130 . The portions of the branches maintained by each policy enforcer  124 ,  126  preferably relates to the configuration information for that policy enforcer as well as some additional information about the other policy enforcers. This additional information is used to communicate with the other policy enforcers. 
     The policy server  122  may further maintain branch  268  storing information used only by the applications running on the server and not shared with any of the policy enforcers  124 ,  126 . Likewise, policy enforcers  124 ,  126  may maintain a portion of branch  268  containing information used only by the applications on each of the policy enforcers and not shared elsewhere. Typically, the data stored in branch  268  is dynamically generated and used by the applications running on the corresponding server or agent. 
     Branch  270  is preferably only included in the LDAP tree for the policy server database  130  and stores logged policy management changes that may be propagated to the policy enforcers  124 ,  126 . Such changes may include, for example, addition, deletion, or modifications of a user on a device, VPN cloud, bandwidth policy, or firewall policy made by the network administrator via the various graphical user interfaces described above. Such changes result in the updating of the policy database  130  where the corresponding DN of the LDAP tree is added, deleted, or modified. The policy server  122  further creates a log of the changes and stores them in branch  270  for later distribution to the policy enforcers  124 ,  126 . 
     FIG. 24 is a more detailed block diagram of branch  270  of the LDAP tree of FIG.  23 . The LDAP root  265  includes an ApplyLog  270   a  entry which in turn includes a user log entry  270   b  and a device log entry  270   c . The user log entries include specific administrator log entries identified by specific DNs  270   d  for reflecting the changes made by the particular administrators. The device log entry  270   c  includes specific device log entries identified by specific DNs  270   e  reflecting the changes that are to be distributed to the particular policy enforces  124 ,  126 . Preferably, the changes made by the administrators are propagated to the policy enforcers  124 ,  126  upon actuation of an apply button such as the apply button  417  illustrated in FIG.  6 . 
     FIG. 25 is a flow diagram for logging and propagating LDAP changes to the policy enforcers according to one embodiment of the invention. In step  420 , a particular network administrator makes a policy setting change. According to one example, the administrator is administrator “adm” working in the domain “domain1,” and the change is the addition of a new user on a device. 
     In step  422 , the change made to the administrator is reflected in the policy server database  130 . In this regard, branches  264  and  266  of the LDAP tree are modified accordingly to reflect the change in the policy setting. Additionally, in step  424 , the policy server  122  creates a log of the changes for the administrator for later processing and sending to the appropriate policy agent. In step  426 , the policy server  122  updates the administrator&#39;s log DN  270   d  to reflect the change. In the above example and as illustrated in FIG. 24, if the log created is named “A_L1,” the policy server  122  updates the DN  270   d  for “adm” at “domain1” to create an attribute “apply”  270   f  that has the value “A_L1”  270   g . Other changes made by the administrator are reflected in separate logs (e.g. “A_L2,” “A_L3”) and appended to the existing value of the apply attribute in the administrator&#39;s log DN  270   d.    
     In step  428 , the policy server  122  checks whether the changes made by the administrator are to be propagated to the appropriate policy enforcers  124 ,  126 . As discussed above, the changes are preferably propagated upon actuation of an apply button from the administrator&#39;s graphical user interface. 
     If the apply button has been actuated, the policy server creates, in step  430 , a log for each policy enforcer to whom the change is to be transmitted. In this regard, the policy server  122  collects all the changes made by the administrator as reflected in the values  270   g ,  270   h  of the apply attribute  270   f  of the administrator&#39;s log DN  270   d . These changes are processed for each policy enforcer belonging to the administrator&#39;s domain. Such processing preferably involves picking the relevant changes and suitably modifying the DNs for the policy enforcer&#39;s LDAP. Such suitable modifications may be necessary, for instance, due to the differences in the tree structures in the policy server database  130  and the policy enforcer databases  132 ,  134 . For instance, a change in the administrator&#39;s log may contain a DN that specifies the domain name of the policy enforcer. In applying this change to the policy enforcer, the domain name would not be specified in the DN since the policy enforcer&#39;s tree structure does not include a domain name. 
     The changes suitably modified for each policy enforcer&#39;s LDAP are then stored in a device log. Each policy enforcer&#39;s log DN  270   e  is then modified to reflect the change to be transmitted to the particular policy enforcer. In the above example and as illustrated in FIG. 24, if the device log created is named “PE_L1,” the policy server  122  updates the DN  270   e  for the particular policy enforcer “PE1” at “domain1” to create an attribute “apply”  270   i  that has the value “PE_L1”  270   j.    
     In step  432 , the apply attribute  270   f  for the administrator&#39;s log DN  270   d  is then deleted from the LDAP tree. In step  434 , the changes collected for each policy enforcer, as reflected in the values  270   j ,  270   k  of the apply attribute  270   i  of the policy enforcer&#39;s log DN  270   e , are transmitted to the policy enforcer for updating its database  132 ,  134 . The changes are sent to the policy enforcers preferably over the HTTPS channel. 
     In step  436 , the policy server  122  checks whether the updates have been successful. In this regard, the policy server  122  waits to receive an acknowledgment from the policy enforcer that the updates have been successfully completed. Upon a positive response from the policy enforcer, the policy server  122  deletes the apply attribute  270   e  for the policy enforcer&#39;s log DN  438 . Otherwise, if the update was not successful (e.g. because the policy enforcer was down), the apply log is re-sent the next time another apply function is invoked. Alternatively, the failed policy enforcer transmits a request to the policy server  122  of the log of non-applied changes when it rejoins the network (e.g. by rebooting). 
     IX. State Transition Protocal for High Availability Units 
     According to one embodiment of the invention, the policy server  122 , policy enforcers  124 ,  126 , as well as other network devices may be configured for high availability by maintaining a backup unit in addition to a primary unit. 
     FIG. 26 is a schematic block diagram of a high availability system including a primary unit  902  and a backup unit  904 . The two units  902 ,  904  communicate with each other by exchanging heartbeats over parallel ports  906   a ,  906   b  and a cable  908 . Such parallel ports  906   a ,  906   b  and cable  908  are conventional components that are commonly available in the art. 
     The primary unit  902  and the backup unit  904  are each similarly connected to other components  910 ,  912 ,  914  via ports  920   a ,  920   b ,  922   a ,  922   b ,  924   a ,  924   b , respectively. These components  910 ,  912 ,  914  may be hubs, switches, connectors, or the like. Because the primary unit  902  and backup unit  904  provide similar services and functions and may be used interchangeably, each unit is preferably connected to the same components  910 ,  912 ,  914 . 
     The parallel port cable  908  is preferably a conventional laplink cable designed to connect two parallel ports and allow communications between them. The primary unit  902  and the backup unit  904  preferably communicate with each other via TCP packets over the high-availability ports  906   a ,  906   b . A point-to-point connection preferably exists between the primary unit  902  and the backup unit  904  over the high-availability ports  906   a ,  906   b.    
     The primary unit  902  is preferably responsible for checking the status of its network ports for problems or failures. For example, if the primary unit  902  detects that one of its network ports is inoperable, e.g. port  922   a , the primary unit  902  then checks whether the corresponding port  922   b  in the backup unit  904  is operational. Upon determining that the corresponding port  922   b  in the backup unit  904  is operational, the primary unit  902  sends a request to the backup unit  904  to take over the system functions as the active unit. The primary unit  902  then relinquishes its role as the active unit and shuts itself down, allowing the backup unit  904  to take on the responsibilities of the primary unit  902 . When the primary unit  902  restarts operation, the backup unit  904  receives a request from the primary unit  902  to relinquish its role as the active unit. 
     When the primary unit  902  is active and does not detect any defects in its ports, it continuously listens on the high-availability port  906   a  to keep track of the status of the backup unit  904 . The primary unit  902  continues to listen on the high-availability port  906   a  for signals coming from the backup unit  904 . When the backup unit  904  is up and running, it connects to the primary unit  902 . Once the connection is made, the backup unit  904  begins sending heartbeats to the primary unit  902 . The backup unit  904  continuously sends heartbeats to the primary unit  902  in predetermined intervals. According to one embodiment of the invention, the backup unit  904  sends a “Keep Alive” packet including a KEEP_ALIVE command to the primary unit  902  every one second. 
     The primary unit  902  responds to the “Keep Alive” packet by changing the command field of the packet to a KEEP_ALIVE_RESP command and re-transmitting the packet to the sender. If the backup unit  904  does not receive a response back from the primary unit  902  for a predetermined period of time (e.g. one second) for one “Keep Alive” packet, the backup unit  904  begins preparing to take over the active role. Preferably, the predetermined period should not be greater less than two consecutive “Keep Alive” packets. 
     Upon taking the role of the active unit, the backup unit  904  attempts to reestablish a connection with the primary unit  902  at regular intervals to determine whether the problem or failure in the primary unit has been cured. If the problem or failure has been cured, the backup unit  904  relinquishes its control to the primary unit  902  after setting the IP addresses of all the network interface cards to the assigned value. 
     In situations where the backup unit  904  takes over the active role from the primary unit  902 , an alert/alarm is sent to the network administrator indicating such a change. In addition, if the primary unit  902  does not receive heartbeats from the backup unit  904 , an alert/alarm is sent to the administrator indicating that the backup unit has failed. 
     A situation may arise when both the primary unit  902  and the backup unit  904  are fully functional, and the backup unit  904  desires to take over the active role. In this case, the backup unit  904  transmits a shut-down command to the primary unit  902  which then relinquishes control. The backup unit  904  continues its role as the active unit until the primary unit  902  transmits a request to the backup unit  904  to relinquish its active role. 
     According to one embodiment of the invention, the initial status determination protocol of each high availability unit as a primary, backup, or stand-alone unit relies on a self-discovery process. FIG. 27 is a flow diagram of an exemplary status discovery process according to one embodiment of the invention. In step  930 , a first high availability unit (unit X) that has not yet definitively discovered its status as a primary or a backup unit boots up, and in step  932  assumes the role of a backup unit. In step  934 , unit X searches the network for a primary unit and inquires, in step  936 , whether a primary unit has been detected. If the answer is YES, unit X tries to connect to the primary unit. If it is successful, unit X initializes as the backup unit in step  938 . If, on the other hand, unit X does not detect the primary unit, unit X assumes the role of the primary unit in step  940 . 
     In step  942 , unit X searches the network for a backup unit. If the backup unit is detected, as inquired in step  944 , unit X connects to the backup unit and initializes as the primary unit in step  946 . If, on the other hand, unit X does not detect any other units in the network within a predetermined time, unit X initializes as a stand-alone unit in step  948 . 
     Once the primary and secondary units have been initialized, configuration changes of the primary unit are also transferred to the backup unit in order to keep the two units synchronized. The configuration information is preferably stored in an LDAP database such as the central policy server database  130  or policy agent databases  124 ,  126 . 
     FIG. 28 is a flow diagram of a process for maintaining configuration information synchronized in the primary and backup units. In step  950 , the primary unit boots up and in step  952 , detects the backup unit. In step  954 , the backup unit receives configuration change information from the primary unit if it is functional. Otherwise, the configuration changes are entered directly into the backup unit by the network administrator. If the configuration change is to be received from the primary unit, the primary unit notifies the backup unit when configuration changes occur in the primary unit. The changes are then transferred and applied to the backup unit. The backup unit in turn transmits the status of the transfer and the apply back to the primary unit. 
     In step  956 , the primary unit is checked to determine whether it is functional. If it is, the primary unit is likewise updated with the configuration change. Otherwise, if the primary unit is not functional, the backup unit takes on the active role and becomes the active unit in step  958 . The primary unit may become non-functional and thus, inactive, due failures in the CPU board, the network interface card, or power supply. 
     In step  960 , the backup unit tags the changes to transfer them to the primary once the primary becomes functional. Once the primary unit becomes functional, the primary unit is updated with the tagged changes maintained by the backup unit as is reflected in step  962 . 
     According to one embodiment of the invention, software updates on the primary and backup units are also synchronized so as to update the primary and backup units serially in a single cycle without the need for multiple update cycles. Thus, the network administrator need not duplicate the efforts of updating the backup unit with the same information as the primary unit. 
     FIG. 29 is an exemplary flow diagram of updating the primary and backup units when they are both functional. In step  970 , an update, such as a software update not stored in the LDAP databases, is sent/transmitted to the primary unit from a management station accessible by the network administrator. The primary unit then updates itself in step  972 . In step  974 , the primary unit automatically sends/transmits the update information to the backup unit. In step  976 , the backup unit updates itself with the update information received from the primary unit. 
     FIG. 30 is an exemplary flow diagram of updating the primary and backup units when the primary unit is not functional. In step  978 , the primary unit becomes nonfunctional, and in step  980 , the network administrator sends/transmits an upgrade directly to the backup unit instead of the primary unit. In step  982 , the backup unit updates itself with the information received from the management station and waits for the primary unit to become functional. Once the primary unit becomes functional  984 , the update is automatically sent/transmitted to the primary unit for upgrading in step  986 . The primary unit then updates itself in step  988 . 
     Although the present invention has been described in detail with reference to the preferred embodiments thereof, those skilled in the art will appreciate that various substitutions and modifications can be made to the examples described herein while remaining within the spirit and scope of the invention as defined in the appended claims. 
     For example, the unified policy management system of FIG. 1 should be viewed as illustrative rather than limiting. It should be apparent to those skilled in the art who are enlightened by the present invention that many alternative configurations are possible. For example, there may be additional networks with policy enforcers or no additional networks at all. Likewise, policy enforcers may not necessarily access the policy server through the Internet, but may be connected via other means such as a WAN, MAN, etc. In short, the number and type of users and resources within and without the organization can vary greatly while staying within the scope of the invention.