Dynamic Service Principal Name Generation for Load Balancer Authentication

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Solution Overview

Problem

Existing network traffic management systems face maintenance overhead and inefficiencies in dynamically selecting backend servers, as they require manual configuration of service principal names (SPNs), which is not feasible in environments where backend servers are selected dynamically.

Innovation Solution

A method and device for dynamically constructing a service principal name (SPN) at a network traffic management device by identifying the IP address of a selected backend server, determining its hostname, and generating the SPN using a preconfigured pattern, allowing the device to obtain a service ticket from a domain controller for user access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If administrators manually configure the service principal name for each backend server, then the service ticket acquisition is reliable, but the maintenance overhead increases and scalability decreases

Engineering Contradiction:

Improveservice ticket acquisition reliabilityVSAvoidconfiguration maintenance complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The network traffic management device automatically generates service principal names by extracting information from backend server hostnames, eliminating the need for manual configuration. The system self-services by dynamically constructing SPNs using a consistent pattern (service-type.hostname.realm) based on the actual server identity, thereby reducing maintenance overhead while maintaining reliability.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system changes the approach from static manual configuration to dynamic automated generation. By transforming the hostname parameter into an SPN using a standardized pattern, the system adapts to different backend servers without requiring pre-configured SPN values, thus reducing complexity while ensuring reliable ticket acquisition.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If administrators manually configure the service principal name for each backend server, then authentication works correctly, but the system cannot handle dynamically selected backend servers

Engineering Contradiction:

Improveauthentication correctnessVSAvoiddynamic backend server selection capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system transitions from static pre-configured SPN values to dynamic SPN generation. The network traffic management device dynamically constructs the service principal name based on the actual backend server hostname at the time of authentication, enabling the system to handle dynamically selected servers while maintaining authentication correctness through consistent SPN pattern application.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The network traffic management device acts as an intermediary that translates the backend server hostname into the appropriate service principal name format. This intermediary function allows the system to work with any dynamically selected server by applying the standardized SPN pattern transformation, bridging the gap between dynamic selection and authentication requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If the network traffic management device uses the host name from user request for SPN, then the configuration is simple, but the SPN does not correspond to the actually selected backend server

Engineering Contradiction:

Improveconfiguration simplicityVSAvoidSPN correspondence accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The system incorporates feedback by using the actual backend server hostname (obtained through DNS resolution of the selected server's IP address) to generate the SPN, rather than relying on the original user request hostname. This feedback mechanism ensures the SPN accurately corresponds to the actually selected server, resolving the discrepancy between request hostname and server identity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Instead of using the user request hostname directly (top-down approach), the system inverts the approach by first identifying the actual selected backend server through its IP address, then deriving the hostname and SPN from that (bottom-up approach). This inversion ensures the SPN corresponds to the actual server rather than the requested service endpoint.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS10230566B1Methods for dynamically constructing a service principal name and devices thereof

Publication Date: 2019.03.12 F5 NETWORKS INC

AI summary

A system, medium and method for dynamically constructing a service principal name is disclosed. A client request from a user to access a service is received at a network traffic management device which identifies an internet protocol (IP) address of a selected backend server to provide the requested service to the client. The network traffic management device identifies a hostname of the selected backend server based at least on the identified IP address and dynamically generates a service principal name (SPN) of the selected backend server based on the determined host name. The network traffic management device obtains a service ticket from a domain controller server using at least the generated SPN of the selected backend server. The network traffic management device uses the obtained service ticket along with the client request to provide the user access to the selected backend server for the client request.