Abstract:
A user authentication service for a communication network authenticates local users before granting them access to personalized sets of network resources. Authentication agents on intelligent edge devices present users of associated end systems with log-in challenges. Information supplied by the users is forwarded to an authentication server for verification. If successfully verified, the authentication server returns to the agents authorized connectivity information and time restrictions for the particular authenticated users. The agents use the information to establish rules for filtering and forwarding network traffic originating from or destined for particular authenticated users during authorized time periods. An enhanced authentication server may be engaged if additional security is desired. The authorized connectivity information preferably includes identifiers of one or more virtual local area networks active in the network. Log-in attempts are recorded so that the identity and whereabouts of network users may be monitored from a network management station.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to regulating connectivity to and within communication networks. More specifically, the present invention relates to authenticating and establishing personalized network connectivity for local users of institutional communication networks.  
       BACKGROUND OF THE INVENTION  
       [0002]     Institutions are relying increasingly on their data communication network infrastructures for efficient communication and data transfer. With this increasing reliance on network computing has arisen a significant need for mechanisms to regulate connectivity to and within such networks. This need has been partially filled by internet protocol (IP) firewalls. IP firewalls typically restrict access to fixed sets of network resources by applying a set of protocol level filters on a packet-by-packet basis or by requiring prospective users to become authenticated before gaining access to the resources. Authentication has generally required users to supply certain signature information, such as a password. While this requirement of signature information has reduced the risk of unauthorized access to firewall-protected resources, firewalls have proven an imperfect and inflexible regulatory solution. Because firewalls are protocol-specific, firewalls have not provided a means for regulating network connectivity in a multi-protocol environment. Moreover, because firewalls regulate access to particular network resources, they have failed to provide a means for regulating access to sets of network resources which can vary as a function of user identity.  
         [0003]     Protocol-independent mechanisms have also been deployed for authenticating users of the resources of institutional networks. However, such authentication mechanisms are only known to have been deployed to challenge remote users attempting to log-in over dial-up phone lines. Such mechanisms are not known to regulate the network access of local users logging-in over a LAN interfaces, such as Ethernet or Token Ring interfaces. Moreover, such mechanisms have, like firewalls, provided an inflexible solution which is unable to regulate access to customized or personalized sets of resources within the network based on user identity.  
         [0004]     The flexibility limitations of the foregoing log-in challenge mechanisms have been partially overcome by independently implementing virtual local area networks (VLANs) within institutional networks. VLANs are sub-networks which typically include a plurality of network devices, such as servers, workstations and PCs, that together form a logical work group within a larger network. Because VLAN membership is assigned based on policies rather than physical location in the network, network bandwidth has been conserved and network security enhanced by assigning VLAN membership based on considerations of efficiency and need and restricting the flow of network traffic across VLAN boundaries.  
         [0005]     While significant security and efficiency gains have been realized by policy-based VLANs, the solution they have offered is far from complete. VLAN membership has generally been assigned to end systems without reference to the identity of the users of such systems. In the current technology, for instance, VLAN membership is typically assigned by comparing network traffic with a configured set of rules which classify the traffic, and by inference the system which originated the traffic, into one or more VLANs. The identity of the user who sent the traffic is not considered in the assignment process. The failure to consider user identity leaves some network security issues unaddressed. Particularly, a person not authorized to use the resources of a VLAN may be able to gain access to its resources by transmitting data packets which the configured rules will classify into the VLAN, either by communicating over a member end system or by spoofing the required identifiers. Known VLAN assignment methods have also failed to contemplate providing conditional access to users based on the day of the week, the time of day, the length of access or a combination of such factors. Furthermore, current networking equipment and policy-based VLANs in particular have not offered collateral functionality, such as the ability to dynamically track where local users are connected to the network. Such a tracking mechanism would greatly simplify tasks such as network troubleshooting by allowing the network location of a user requesting technical support to be easily determined.  
         [0006]     Accordingly, there is a need for comprehensive services for regulating connectivity in institutional networks which are not subject to the inflexibility of conventional user log-in mechanisms or the lack of consideration for user identity of conventional VLAN assignment techniques. There is also a need for services which authenticate local users of institutional networks before establishing network connectivity. There is a further need for user authentication services which provide collateral functionality, such as the ability to dynamically track the whereabouts of network users.  
       SUMMARY OF THE INVENTION  
       [0007]     In accordance with its basic feature, the present invention combines the user-specific advantages of log-in challenges and the flexibility of VLANs into a deterministic user-based authentication and tracking service for local users of institutional communication networks.  
         [0008]     It is therefore one object of the present invention to provide a service which authenticates local users before establishing network connectivity.  
         [0009]     It is another object of the present invention to provide a service which assigns and regulates user access to personalized sets of network resources.  
         [0010]     It is another object of the present invention to provide a service which grants user access to personalized sets of network resources upon verifying signature information.  
         [0011]     It is another object of the present invention to provide a service which conditions user access to personalized sets of network resources on one or more time-dependent variables.  
         [0012]     It is another object of the present invention to provide a service which tracks user identity and network location.  
         [0013]     These and other objects of the present invention are accomplished by a service which requires that local users be authenticated before gaining access to personalized sets of network resources. User identification information, time restrictions and authorized lists of resources for particular users are entered and stored in the network. Prior to authentication, packets from an end system being used by a prospective user of network resources are transmitted to an authentication agent operative on an intelligent edge device associated with the system. The agent relays log-in responses received from the system to a basic authentication server in the network for verification of the user. Verification is made by comparing log-in responses with the user identification information stored in the network and determining whether time restrictions associated with the user identification information are applicable. If the basic authentication server is able to verify from the log-in response that the user is an authorized user of network resources, and that the user is authorized to use the network resources at the time of the log-in attempt, the basic authentication server transmits to the agent the list of network resources for which the user is authorized, along with any time restrictions. The agent forwards the list of authorized network resources and time restrictions for storage and use on the edge device. The edge device uses the authorized list of resources and time restrictions to establish network connectivity rules for the user. Preferably, the authorized list of network resources is a list of one or more VLANs.  
         [0014]     If the basic authentication server is unable to verify from the log-in response that the user is an authorized user of network resources and authorized to use network resources at the time of the log-in attempt, the basic authentication server communicates that information to the agent. Packets from the user continue to be directed to the agent or, alternatively, are dropped. Preferably, the number of log-in attempts users are granted before packets are dropped is configurable.  
         [0015]     In another aspect of the invention, the basic authentication server records information relating to the identity and network location of users learned from log-in attempts. The information is accessible by a network administrator tracking network activity from a network management station.  
         [0016]     In another aspect of the invention, when the basic authentication server successfully verifies that the user is an authorized user of network resources, and that the user is authorized to use the network resources at the time of the log-in attempt, the basic authentication server, in lieu of transmitting to the agent the list of authorized network resources and time restrictions, initiates an enhanced authentication method for the user. The enhanced authentication method is preferably conducted by an enhanced authentication server within the network.  
         [0017]     In another aspect of the invention, when an authenticated user logs-off the network, or fails to transmit packets for a predetermined time, or if the system being used by the authenticated user is disconnected from the network, or if the authorized connectivity period expires, or if the basic authentication server or other management entity instructs the agent to abolish the authenticated user&#39;s network connectivity, the authenticated user&#39;s network connectivity is deactivated.  
         [0018]     The present invention can be better understood in reference to the following detailed description, taken in conjunction with the accompanying drawings which are briefly described below. Of course, the actual scope of the invention is defined by the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a schematic of a network in which a preferred embodiment of the present invention is operative;  
         [0020]      FIG. 2  is a schematic of an intelligent edge device operative in the network according to  FIG. 1 ;  
         [0021]      FIG. 3A  is a schematic of a network management station operative in the network according to  FIG. 1 ;  
         [0022]      FIG. 3B  is a schematic of a end system operative in the network according to  FIG. 1 ;  
         [0023]      FIG. 4  is a functional diagram of an authentication agent operative in the network according to  FIG. 1 ;  
         [0024]      FIG. 5  is a functional diagram of a basic authentication server operative in the network according to  FIG. 1 ;  
         [0025]      FIG. 6  is a functional diagram of an authentication client operative in the network according to  FIG. 1 ;  
         [0026]      FIG. 7  is a schematic of an LAN in which a more preferred embodiment of the present invention is operative;  
         [0027]      FIG. 8  is a functional diagram of a basic authentication server operative in the network according to  FIG. 7 ;  
         [0028]      FIG. 9  is a flow diagram of a preferred method for authenticating users within network  1 ; and  
         [0029]      FIG. 10  is a flow diagram of a preferred method for authenticating users within network  7 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]     Referring to  FIG. 1 , a network  1  operating in accordance with a preferred embodiment of the present invention is shown. Network  1  includes intelligent edge devices  10 ,  15  and a network management station  20  interconnected over a backbone network  30 , such as an asynchronous transfer mode (ATM) or fiber distributed data interface (FDDI) network. Devices  10 ,  15  and station  20  are interconnected using cables, which may be fiber optic, unshielded twisted pair, or other form. Devices  10 ,  15  are associated with end systems  40 ,  50 ,  60 , and  45 ,  55 ,  65 , respectively, which are operative in local area network (LAN) communication media, such as Ethernet or Token Ring. It will be appreciated that Ethernet as used herein is not limited to  10  megabit Ethernet, but includes other Ethernet varieties, such as Fast Ethernet and Gigabit Ethernet. Systems  40 ,  50 , 60  and  45 ,  55 ,  65  may be workstations, PCs, or other systems having a user interface. Although the illustrated network  1  is shown to include two edge devices each associated with multiple end systems, it will be appreciated that a network operating in accordance with the present invention may include one or more edge devices interconnected across a backbone network, and that each edge device may be associated with one or more end systems or servers. It will also be appreciated that, in networks operating in accordance with the present invention, every edge device preferably has common operational capabilities.  
         [0031]     Turning to  FIG. 2 , device  10  is shown in greater detail. Device  10  is preferably representative of devices  10 ,  15 . Device  10  includes a management processor module  210 , backbone module  220  and authentication modules  240 ,  250 ,  260  interconnected over a switching link  230 . Modules  220 ,  240 ,  250 ,  260  are preferably implemented using custom logic, e.g., application specific integrated circuits (ASICs), while management processor module  210  is preferably software-implemented. Authentication modules  240 ,  250 ,  260  each include a LAN interface interconnecting systems  40 ,  50 ,  60 , respectively, and switching link  230 . In contradistinction to hubs which indiscriminately forward packets in unmodified form to all associated end systems, device  10  includes means on each of modules  220 ,  240 ,  250 ,  260  for interpreting, modifying, filtering and forwarding packets. Preferably, modules  220 ,  240 ,  250 ,  260  are also operative to perform necessary LAN media translations so that device  10  is able to support end stations operating using disparate LAN media. Thus, for example, system  40  utilizing an Ethernet communication protocol may communicate through device  10  with system  50  utilizing Token Ring. LAN switches marketed by the assignee hereof under the federally registered trademarks OmniSwitch® and PizzaSwitch®, implemented with appropriate switching modules available from the assignee, may advantageously be implemented as devices  10 ,  15  in the performance of the above-described functionality.  
         [0032]     Turning to  FIG. 3A , a schematic diagram of network management station  20  is shown. Preferably, station  20  includes a user interface  310 , a software-implemented basic authentication server  320  and user records  330 . Although server  320  and user records  330  are shown operative on station  20 , server  320  and user records  330 , or either one, may be operative on another device in network  1  accessible by station  20 . Although network  1  is illustrated to include a single basic authentication server  320 , a network operating in accordance with the present invention may include one or more basic authentication servers. Server  320  is preferably configured with an address of each of devices  10 ,  15  and an associated authentication key for the authentication agent active on each of devices  10 ,  15 . The addresses are preferably IP addresses.  
         [0033]     Turning to  FIG. 3B , a schematic diagram of system  40  is shown. System  40  is representative of systems  40 ,  50 ,  60  and  45 ,  55 ,  65 . System  40  has a user interface  350  and an authentication client  360 . Authentication client  360  is software used during the authentication process. This is preferably a software application installed on system  40  but may also take the form of a standard software application such as Telnet. Client  360  is configured with an address of an authentication agent on associated device  10 , which may be an IP address or a reserved media access control (MAC) address.  
         [0034]     An authentication agent is deployed on each of devices  10 ,  15 . Turning to  FIG. 4 , a functional diagram of an authentication agent  400  residing on device  10  is shown. Agent  400  is preferably a software module implemented by management processor module  210 . Agent  400  is configured with an address of device  10 , an address of basic server  320  and an authentication key for server  320 . The configured addresses are preferably IP addresses.  
         [0035]     Agent  400  includes CNCT EST means  410 . Means  410  serves, upon initialization of device  10 , to establish a secure connection with server  320 . Means  410  requests a connection to server  320  using the known address of server  320  and acknowledges a response from server  320  to such a request. Means  410  also transmits and receives information from and to server  320  sufficient to allow agent  400  and server  320  to authenticate one another. Preferably, mutual authentication is accomplished through exchange of authentication keys configured on agent  400  and server  320 . Means  410  may encrypt information and decipher encrypted information transmitted during the secure connection establishment process. TCP/IP based flows between agent  400  and server  320  are contemplated. Although network  1  is shown to include only one basic server  320 , it will be appreciated that a network may include more than one basic server. If an agent is configured with the address of more than one basic server in the network, and an attempt to establish a secure connection with a particular server fails, the agent may implement the foregoing process using the known address of another basic server until a secure connection is established.  
         [0036]     Agent  400  also includes ID REQ means  420 . Means  420  serves to obtain log-in responses from users of associated systems  40 ,  50 ,  60  by communicating with authentication clients operative on systems  40 ,  50 ,  60 . Means  420  acknowledges requests received from clients to establish an authentication session. Means  420  responds to the requests by transmitting a log-in prompt to the requesting one of clients. IP-based flows using an application, such as Telnet, or MAC-based flows between agent  400  and clients are contemplated. Flows are initiated by clients using a reserved MAC address or IP address of agent  400  configured on clients.  
         [0037]     Agent  400  also includes ID RLY means  430 . Means  430  serves to relay to server  320  for verification log-in responses received from users in response to log-in prompts. Means  430  associates the known address of device  10 , the identifier of the authentication module (i.e.,  240 ,  250  or  260 ) associated with the one of systems  40 ,  50 ,  60  being used by a user and the log-in response. Means  430  transmits the associated authentication information to server  320  for verification.  
         [0038]     Agent  400  also includes VER RLY means  440 . Means  440  serves to relay user status information received from server  320  to users. Means  440  transmits user status information to the one of systems  40 ,  50 ,  60  being used by a user. User status information preferably includes a log-in valid or log-in invalid message, depending on whether server  320  was able to successfully verify the log-in response. IP-based flows using an application such as Telnet or MAC-based flows are contemplated for transmission of user status information between agent  400  and clients.  
         [0039]     Agent  400  also includes SESS TERM means  450 . Means  450  serves to terminate an authentication session if a user has failed to be authenticated after a configurable number of failed log-in attempts. Means  450  transmits to the client associated with the one of systems  40 ,  50 ,  60  being used by the user an authentication session termination message after a configurable number of log-in failures. Means  450  also terminates the authentication session with the one of clients.  
         [0040]     Agent  400  also includes RSRC RLY means  460 . Means  460  serves to forward for storage and use on device  10  authorized connectivity information received from server  320  for authenticated users of systems  40 ,  50 ,  60 . Authorized connectivity information may advantageously be transmitted by server  320  to agent  400  in the same data packet as user status information. Authorized connectivity information includes, for the particular one of the systems  40 ,  50 ,  60 , a list of authorized network resources. Authorized connectivity information may also include time restrictions, if any. Time restrictions preferably define times during which the particular user is authorized to use the network resources, such as the day of the week, the time of day, and the length of permitted access. The list of authorized network resources is preferably a list of VLAN identifiers. Authorized connectivity information is preferably forwarded by agent  400  to management processor module  210  along with the authentication module identifier. Management processor module  210  preferably associates the authorized connectivity information with a known address of the one of the systems  40 ,  50 ,  60  being used by the authenticated user and stores the pair in device records. The address is preferably a MAC address.  
         [0041]     Device records are advantageously used on device  10  to make filtering and forwarding decisions on packets received from and destined for authenticated users. Packets transmitted by an unauthenticated one of systems  40 ,  50 ,  60 , unless addressed to authentication agent  400 , are dropped by the receiving one of modules  240 ,  250 ,  260 . Packets addressed to an unauthenticated one of systems  40 ,  50 ,  60  are also dropped. Packets transmitted by one of authenticated systems  40 ,  50 ,  60  addressed to another authenticated one of systems  40 ,  50 ,  60  are selectively forwarded according to the following rules: 
        1. If the destination address is the address of another one of systems  40 ,  50 ,  60  associated with device  10 , resort is made to device records on device  10  to verify that the source and destination systems share a common VLAN. If a VLAN is shared, the packet is forwarded to the destination system. If a VLAN is not shared, the packet is dropped.     2. If the destination address is not the address of another one of systems  40 ,  50 ,  60  associated with device  10 , resort is made to device records on device  10  to retrieve the VLAN identifiers associated with the source system. The VLAN identifiers are appended to the packet and the packet is forwarded to backbone module  220  for transmission on backbone network  30 . When the packet arrives on the edge device (e.g., 15) associated with the destination system (e.g., 45), resort is made to device records on the edge device to verify that the source and destination systems share a common VLAN. If a VLAN is shared, the packet is forwarded to the destination system. If a VLAN is not shared, the packet is dropped. Packets addressed to unauthenticated systems in network  1  continue to be dropped. The foregoing rules may be implemented using various known protocols. See, e.g., Ross U.S. Pat. No. 5,394,402 and Nair &amp; Bailey, Application Ser. No. 08/782,444, which are incorporated herein by reference. It will be appreciated that any addressable core, edge, or end devices, stations and systems in network  1  which are not subject to authentication requirements may be treated as authenticated systems for purposes of transmitting and receiving packets under the foregoing rules.        
 
         [0044]     Agent  400  also includes ID TERM means  470 . Means  470  serves, upon receipt of log-off commands from authenticated users, or upon expiration of the authorized connectivity period, or when one of authenticated systems  40 ,  50 ,  60  is physically disconnected from network  1 , or when one of authenticated systems  40 ,  50 ,  60  fails to send traffic for a prescribed length of time, or upon receipt of instruction from server  320 , to deactivate the established network connectivity. Means  460  forwards to management processor module  210  a request to remove from device records the address-authorized connectivity information entry for the user whose connectivity is to be deactivated. Upon receipt of such a request, management processor module  210  preferably removes the entry from device records and the authenticated one of systems  40 ,  50 ,  60  reverts to the unauthenticated state.  
         [0045]     Turning to  FIG. 5 , a functional diagram of basic authentication server  320  is shown. Server  320  includes RSRC AUTH means  510 . Means  510  serves to enable network administrators to define, on an individualized basis, authorized connectivity information for users of the network  1 . Means  510  enables a network administrator to input user-specific entries. Means  510  supplies a textual or graphical display to user interface  310  operative to accept user-specific entries. Means  510  stores each user-specific entry as a related pair in user records  330 . Each user-specific entry preferably includes user identifier information and a list of authorized network resources. User-specific entries may also include time restrictions for the particular user. User identification information preferably includes signature information for the user, such as a password. Means  510  also enables a network administrator to input device-specific entries. Device-specific entries preferably includes, for each edge device in network  1  having an authentication agent, a device address and an authentication key. Device addresses are preferably IP addresses. Means  510  stores each device-specific entry as a related pair in network management records (not shown). Each device address is preferably uniquely assigned to a particular edge device operative within network  1 .  
         [0046]     Server  320  also includes CNCT EST means  520 . Means  520  serves, upon receipt of a request from an authentication agent, to establish a secure connection with the agent. Means  520  acknowledges receipt from the agent of a request to establish a secure connections and to respond to the request. Means  520  also transmits and receives information sufficient to allow the agent and server  320  to authenticate one another. Preferably, authentication is established through exchange of authentication keys. Means  520  may encrypt information and decipher encrypted information transmitted during the secure connection establishment process. TCP/IP based flows between the agent and server  320  are contemplated.  
         [0047]     Server  320  also includes ID VER means  530 . Means  530  serves to subject to a verification process authentication information received from users via agent  400 . Means  530 , upon receipt of authentication information from agent  400 , determines if the log-in response matches the user identification information associated with a user-specific entry in user records  330 . If a match is found, and there are time restrictions associated with the user-specific entry, means  530  determines from the time restrictions if the user is authorized to use network  1  at the particular time. If the user is time-authorized or there are no time restrictions, means  530  generates authorized connectivity information. Means  530  retrieves the list of authorized network resources associated with the matching user identification information in the generation of authorized connectivity information. Authorized connectivity information may also include any time restrictions. Means  530  also generates user status information. User status information is information sufficient to communicate to agent  400  whether user identification information was successfully verified. User status information is preferably either a log-in valid or log-in invalid message. Means  530  transmits authorized connectivity information and user status information to agent  400 . Preferably, authorized connectivity information and user status information are transmitted as part of the same data packet. If no match for user identification information is found, or if the user is not time-authorized, means  530  generates and transmits to agent  400  user status information, preferably in the form of a log-in invalid message, but does not generate or transmit authorized connectivity information. Although the above described means operative on server  320  are described to be interoperative in conjunction with agent  400 , it will be appreciated that the means are fully interoperative with other authentication agents residing on edge devices in network  1 .  
         [0048]     Server  320  also includes ID STOR means  540 . Means  540  serves to forward for storage and use by a network administrator user tracking information. User tracking information is preferably retained for all log-in attempts made by prospective users, whether successful or unsuccessful. User tracking information may include, for each log-in attempt, any information learned from one or more of the following: user identification information, authentication information, user status information, authorized connectivity information. User tracking information also may include the time of day the log-in attempt was made. The time of day may be kept on and obtained from server  320 . Server  320  preferably associates the user tracking information and stores the information as an entry in a network activity database (not shown) that is accessible by or resides on station  20 . Network activity database entries are accessible by a network administrator using interface  310 .  
         [0049]     Server  320  also includes NET MNTR means  550 . Means  550  serves to enable a network administrator to access and use user tracking information. Means  550  supplies a textual or graphical display to interface  310  operative to display user tracking information. Means  550  also enables a network administrator to generate user tracking information reports consisting of related information from one or more user tracking information entries.  
         [0050]     Turning to  FIG. 6 , a functional diagram of client  360  is shown. Client  360  is representative of clients residing on systems  40 ,  50 ,  60  and  45 ,  55 ,  65 . Client  360  includes ID INIT means  610 . Means  610  serves, when system  40  is booted-up by a user, to request and establish an authentication session with agent  400 . Alternatively, means  610  can be activated by a direct action of the user of system  40 . Means  610  transmits to agent  400  a request to establish an authentication session using a known address of agent  400 . Client  360  preferably transmits requests periodically until agent  400  responds. A MAC-based flow is contemplated. Alternatively, an IP-based flow using an application such as Telnet may be used.  
         [0051]     Client  360  also includes ID RPLY means  620 . Means  620  serves to enable users to reply to log-in prompts received from agent  400 . Means  620  supplies a textual or graphical display to a user interface of system  40  operative to accept log-in responses. Means  620  also transmits log-in responses to agent  400 .  
         [0052]     Client  360  also includes VER DSPL means  630 . Means  630  serves to convey to users whether log-in attempts were successful or unsuccessful. Means  630  supplies a textual or graphical display to a user interface of system  40  operative to display user status information, preferably a log-in valid message or a log-in invalid message, received from agent  400 .  
         [0053]     Client  360  further includes ID OFF means  640 . Means  640  serves to initiate the log-off process by which authenticated users log-off the network  1 . Means  640  supplies a textual or graphical display to user interface  350  operative to accept log-off commands. Means  640  transmits log-off commands to agent  400  for deactivation of established network connectivity.  
         [0054]     Referring to  FIG. 7 , a network  7  operating in accordance with an alternative embodiment of the present invention is shown. In the alternative embodiment, an enhanced authentication method is conducted before network connectivity is granted. Network  7  includes intelligent edge devices  710 ,  715  and a network management station  720  interconnected over a backbone network  730  by means similar to those described in relation to network  1 . Bridges  710 ,  715  are associated with end systems  740 ,  750 ,  760  and  745 ,  755 ,  765 , respectively, which utilize LAN communication media, such as Ethernet or Token Ring. Network  7  also includes enhanced authentication server  770  interconnected over backbone network  730 . It will be appreciated that, as in the previous preferred embodiment, a network operating in accordance with the alternative embodiment may include one or more edge devices having common operational capabilities and associated with one or more end sytems. In network  7 , devices  710 ,  715  station  720  and systems  740 ,  750 ,  760  and  745 ,  755 ,  765  have operational capabilities common to their counterparts in network  1 , plus additional operational capabilities hereafter described.  
         [0055]     Turning to  FIG. 8 , a functional diagram of a basic authentication server  800  preferably operable on station  720  is shown. Server  800  is preferably interoperative with devices  710 ,  715  and systems  740 ,  750 ,  760  and  745 ,  755 ,  765  and associated modules, agents and clients to perform the functionality of server  320  described above, including RSRC AUTH means  510 , CNCT EST means  520 , ID VER means  530 , ID STOR means  540  and NET MNTR means  550 .  
         [0056]     Server  800  also includes ENH CNCT EST means  810 . Means  810  serves to establish and maintain a secure connection with enhanced authentication server  770 . A TCP/IP based flow is contemplated. Server  800  also includes ENH RSRC AUTH means  820 . Means  820  serves to enable network administrators to define, on an individualized basis, an enhanced authentication method for each prospective user of network  7 . Means  820  enables a network administrator to enter user-specific entries which additionally include enhanced authentication method information. Enhanced authentication method information includes information sufficient to enable basic server  800  to identify a device, station, or system within network  7  which will conduct the enhanced authentication session, if any, the prospective user must successfully complete to become authenticated. Preferably, enhanced authentication method information includes an IP address of enhanced authentication server  770 . Enhanced authentication methods may include one of various security methods implemented on enhanced authentication server  770 . Authentication methods marketed under the trade names Secure ID™ by Security Dynamics, Inc. and methods that comply with Internet Engineering Task Force (IETF) RFC 2058 Remote Authentication Dial-in User Service (RADIUS) are referenced herein by way of example.  
         [0057]     Server  800  also includes ENH ID VER means  830 . Means  830  serves, upon verifying log-in responses received from a user and that the user is authorized to use the network  7  at the time of the log-in attempt, to initiate an enhanced authentication method, if indicated. Means  830 , upon determining that the log-in response matches user identification information associated with a user-specific entry in user records, and upon determining that the user is time-authorized if time restrictions are indicated, checks whether there is an enhanced authentication method associated with the matching user-specific entry. If an enhanced authentication method is indicated, means  820 , before transmitting authorized connectivity information and user status information to the agent on the appropriate one of devices  710 ,  715 , transmits a request to enhanced authentication server  770  to conduct an enhanced authentication session with the user. The enhanced authentication session is preferably conducted between enhanced server  770  and the user transparently to basic server  800 . Enhanced server  770  instructs basic server  800  of the results of the enhanced authentication session. If the user was successfully authenticated, means  830  transmits to the agent authorized connectivity information and user status information, preferably in the form of a log-in valid message. If the user was not successfully authenticated, means  830  transmits user status information, preferably a log-in invalid message, but no authorized connectivity information. If an enhanced authentication method is not indicated when the check for an enhanced authentication method is performed, means  830  transmits to the agent authorized connectivity information and user status information, in the form of a log-in valid message, without engaging server  770 . If a matching entry for user identification information is not found in user records, or if the user is not time-authorized, means  830  transmits to the agent user status information, in the form of a log-in invalid message, without transmitting authorized connectivity information.  
         [0058]     Referring now to  FIG. 9 , a flow diagram illustrates a preferred method for implementing the invention within network  1 . When device  10  is initialized ( 905 ), agent  400  attempts to establish a secure connection with server  320  using the known address of server  320 . Once a TCP session is successfully established, agent  400  and server  320  authenticate one another by exchanging authentication keys.  
         [0059]     When a user boots-up device  40  ( 910 ), client  360  activates. Client  360  sends an authentication request to agent  400  using a known address of agent  400 . Authentication requests are transmitted to agent  400  periodically until agent  400  responds. When agent  400  receives a request, agent  400  responds by transmitting a log-in prompt to client  360 .  
         [0060]     The user enters a log-in response and the response is transmitted to agent  400  ( 915 ). Agent  400  transmits authentication information to server  320 . Authentication information preferably includes an address of device  10 , an identifier of authentication module  240  associated with system  40 , and the log-in response.  
         [0061]     Server  320  determines whether the log-in response is recognized on station  20  ( 920 ). Server  320  checks user records  330  for a user-specific entry having user identification information matching the log-in response. If a matching entry is found, server  320  checks any time restrictions associated with the entry to determine if the user is authorized to use the network resources at the particular time ( 925 ). If the prospective user is time-authorized, server  320  retrieves the list of authorized network resources and any time restrictions associated with the matching user identification information. The information is transmitted to agent  400  ( 930 ) along with user status information, preferably a log-in valid message. If no matching entry is found ( 935 ), or if the user is not time-authorized ( 940 ), user status information, preferably a log-in invalid message, is returned to the user via agent  400 . Agent  400  also in that instance determines if user has made the configurable number of failed log-in attempts ( 945 ). If the configurable number of failed log-in attempts has been reached ( 950 ), agent  400  terminates the authentication session with client  360 . The user is denied network access until such time as the user reboots system  40 . If the configurable number of failed log-in attempts has not been reached ( 955 ), agent  400  presents the user with another log-in prompt.  
         [0062]     Turning to  FIG. 10 , a flow diagram illustrates a preferred method for implementing the invention within network  7 . The method proceeds generally as in  FIG. 9 , except that an enhanced authentication method is performed, if indicated. Accordingly, once a determination is made that the user is time-authorized ( 1005 ), basic server  800  checks whether there is an enhanced authentication method associated with the matching entry ( 1010 ). If an enhanced authentication method is indicated, server  800  transmits a request to enhanced authentication server  770  to conduct an enhanced authentication session with the user ( 1015 ). Enhanced server  770  informs basic server  800  of the results of the enhanced authentication session. If the session was successfully completed ( 1020 ), basic server  800  transmits authorized connectivity information and user status information, in the form of a log-in valid message, to the agent ( 1030 ). If enhanced session was not successfully completed ( 1025 ), basic server  800  transmits a log-in invalid message to user and does not transmit authorized connectivity information to agent. Agent also in that instance determines if user has made a configurable number of failed log-in attempts. The authentication session either continues or terminates as discussed depending on the outcome of that inquiry. If an enhanced authentication method is not indicated when the check for an enhanced authentication method is performed ( 1010 ), server  800  transmits authorized connectivity information and user status information, in the form of a log-in valid message, without requesting server  770  to conduct an enhanced authentication session.  
         [0063]     It will be appreciated by those of ordinary skill in the art that the invention can be embodied in other specific forms without departing from the spirit or essential character hereof. The present description is therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.