# Oracle Enterprise Gateway Architecture

## Contents
Overview Product Architecture Product Concepts

## Overview
This topic provides a high-level overview of the Oracle Enterprise Gateway product architecture, and describes its main components and concepts. For an introduction to the product features and benefits, see the Oracle Enterprise Gateway Overview.
## Product Architecture
This section provides a high-level overview of the Oracle Enterprise Gateway architecture. The following simple diagram shows the main components:
Simple Gateway Architecture
This diagram shows a simplified view, which includes a single Enterprise Gateway, Web Service, and client (for example, Oracle Service Explorer). However, you can deploy multiple components to suit the needs of your environment. In addition, this diagram shows communication between the client and the Enterprise Gateway using REST and XML. However, a wide range of transports and protocols is supported (for example, HTTP, JMS, TIBCO, FTP, SMTP, and POP). Enterprise Gateway The Enterprise Gateway provides governance, acceleration, integration, and security for SOA systems. It performs application networking by routing traffic based on content and sender, and by performing XML content screening. The Enterprise Gateway applies policies to incoming messages by running message filters on requests. For more details on Enterprise Gateway features, see Oracle Enterprise Gateway Overview. Service Explorer Service Explorer is a Web Services test client, which is used to generate test messages that are sent to the Enterprise Gateway and back to Service Explorer. Service Explorer supports both SOAP-based and REST-based invocations. The following diagram shows a simplified view of the design-time tools used to manage the Enterprise Gateway:
Simple Design Time Architecture
Policy Studio The Policy Studio is a policy management tool that enables an administrator to easily configure policies and Enterprise Gateway settings to control and protect all deployed Web Services. For example, the Policy Studio enables you to create and assign policies, configure the full range of Enterprise Gateway configuration settings, and manage your Enterprise Gateway deployments. The Policy Studio is typically installed on a separate machine from the Enterprise Gateway to enable remote administration. Service Manager Service Manager is a web-based system administration tool that simplifies Enterprise Gateway management tasks. It provides quick and easy access to enable you to manage your services and policies. For example, you can register Web services and assign policies to them. Real-time Monitoring Console The Real-time Monitoring Console provides web-based real-time monitoring of HTTP and HTTPS traffic processed by the Enterprise Gateway. This web-based console enables administrators to detect malicious activity in real time, and to take precautionary actions if they feel a service is under attack. Traffic Monitor The Traffic Monitor tool provides a web-based message log of the HTTP and HTTPS traffic processed by the Enterprise Gateway. You can filter messages on a range of criteria (for example, transaction ID, service name, or remote host), drill down to view and save message contents, and change logging settings on-the-fly. Service Monitor Service Monitor is a separately installed component that generates reports and charts based on the usage metrics of all the Enterprise Gateways in your network. Service Monitor provides integration with databases such as MySQL Server, MS SQL Server, and Oracle. Service Monitor also includes a Real-time Monitoring Console. For example, you can generate and store reports that monitor which authenticated clients are calling which Web Services.
Simple Runtime Architecture
In a typical deployment scenario, Oracle Enterprise Gateway components are deployed in the demilitarized zone (DMZ). The connection between the client and the Enterprise Gateway is protected by a perimeter firewall, and the connection between the Enterprise Gateway and the Web Service by a Network Address Translation (NAT) firewall.
## Product Concepts
This section explains the main concepts in the Oracle Enterprise Gateway product architecture. Policy A policy is a network of message filters in which each filter is a modular unit that processes a message. A message can traverse different paths through the network, depending on which filters succeed or fail. For example, this enables you to configure policies that route messages that pass a Schema Validation filter to a back-end system, and route messages that pass a different Schema Validation filter to a different system. Filter A filter is an executable rule that performs a specific type of processing on a message. For example, the Message Size filter rejects messages that are greater or less than a specified size. There are many categories of message filters available with the Enterprise Gateway, including authentication, authorization, content filtering, signing, and conversion. In the Policy Studio, a filter is displayed as a block of business logic that forms part of an execution flow known as a circuit. Circuit A circuit is a series of filters through which a message passes. A circuit can contain other circuits, which enables you to build modular reusable policies. In the Policy Studio, a circuit is displayed as a path through a set of filters. A filter can have only one Success Path and one Failure Path. You can use these success paths and failure paths to create sophisticated rules. For example, if the incoming data matches schema A, scan for attachments, and route to service A, otherwise route to service B. You can configure the colors used to display success paths and failure paths in the Policy Studio Preferences menu. You can also specify to Show Link Labels (S or F). The following example screen shot shows an example circuit with success paths and a failure path:
Example Authentication/Authorization Policy Circuit
A circuit must have a Start filter (in this example, Check against threats). Filters labeled End stop the execution of the policy if the filter execution fails. Filters labeled Start/End indicate that the circuit execution starts there, and that the circuit stops executing if this filter fails. A circuit with a single filter labeled Start/End is also valid. Message Attributes Each filter requires input data and produces output data. This data is stored in message attributes, and you can access their values using syntax such as `${attribute.name}`. You can also use specific filters to create your own message attributes, and to set their values. The full list of message attributes flowing through a policy is displayed when you right-click the Policy Studio canvas, and select Show All Attributes. You can also hover your mouse over a filter to see its inputs and outputs. The Trace filter enables you to trace message attribute values at execution time. The following example screen shot shows the attributes displayed when hovering over an HTTP Basic authentication filter:
HTTP Basic Authentication Policy
If a filter requires an attribute as input that has not been generated in the previous execution steps, the filter is displayed in a different color in the Policy Studio (default is red). You can configure the color used to display missing attributes in the Policy Studio Preferences menu. Alternatively, you can also view all required attributes by right-clicking the canvas, and selecting Show All Attributes. A missing attribute may indicate a problem that you need to investigate (for example, in the chaining of filters or policies, or that the policy can not run on its own). This is often the case for reusable filters, such as those displayed in the previous example. At the policy level, you also can click the horizontal bar at the top of the Policy Studio canvas to show the list of all attributes required as input to the entire policy. If any attributes are generated by the policy, you can click a corresponding bar at the bottom to see a list of generated attributes. The following example screen shot shows the attributes required by an Authenticate policy:
HTTP Basic Authentication Attributes
Faults When a SOAP transaction fails, you can use a SOAP fault to return error information to the SOAP client. By default, the Enterprise Gateway returns a basic SOAP fault to the client when a message filter fails. You can add a SOAP Fault filter to a policy to return more detailed error information to the client. For example, the previous example screen shot shows an AuthenticationFaultHandler, which is a policy shortcut to the following fault handler policy:
Authentication Fault Handler
Policy Shortcut A policy shortcut enables you to create a link from one policy to another policy. For example, you could create a policy that inserts security tokens into a message, and another that adds HTTP headers. You can then create a third policy that calls the other two policies using Policy Shortcut filters. A policy shortcut chain enables you to run a series of policies in sequence without needing to create a policy containing policy shortcuts. In this way, you can create modular policies to perform certain specific tasks, such as authentication, content filtering, returning faults, or logging, and then link these policies together in a sequence using a policy shortcut chain. You can also use Service Manager to automate the creation of a policy shortcut chain simply by dragging and dropping existing policies into a composite policy. Alerts The Enterprise Gateway can send alert messages for specified events to various alerting destinations. System alerts are usually sent when a filter fails, but they can also be used for notification purposes. The Enterprise Gateway can send system alerts to the following destinations: Windows Event Log UNIX/Linux sylsog SNMP Network Management System Check Point Firewall-1 Email recipient You can configure alert destinations, and then add an Alert filter to a policy, specifying the appropriate alert destination. Policy Container A policy container is used to group similar policies together (for example, all authentication or logging policies), or policies that relate to a particular service. A number of useful policies are provided in the Policy Library container (for example, policies that return faults, and policies that block threatening content). You can add your own policies to this container, and add your own policy containers to suit your requirements. Policy Context Policies can execute in a specified context. You can set a context by associating a relative execution path or listener with a policy. When a policy is called from another policy, the context is set to the calling policy name (for example, Authenticate). In the Policy Studio, you can select a context from the drop-down list at the bottom of the canvas, and the Policy Studio displays whether the attributes required for execution are available in that context. Listeners You can define different types of listeners and associate them with specific policies. For example, listeners include the following types: HTTP/HTTPS Directory Scanner POP mail server connection JMS connection TIBCO RV/EMS connection The Enterprise Gateway can be used to provide protocol mediation (for example, receiving a SOAP request over JMS, and transforming it into a SOAP/HTTP request to a back-end service). For HTTP/HTTPS listeners, policies are linked to a relative path. Otherwise, policies are linked to the listener itself. You can associate a single policy with multiple listeners. Remote Hosts You can define a remote host when you need more control of the connection settings to a particular Web Service server. The available connection settings include the following: HTTP version IP addresses Timeouts Buffers Caches For example, by default, the Enterprise Gateway uses HTTP 1.1. You can force it to use HTTP 1.0 using Remote Host settings. You must also define a Remote Host if you want to track real-time metrics for a particular host. Servlet Applications The Enterprise Gateway provides a Web server and servlet application server that can be used to host static content (for example, documentation for your project), or servlets providing internal services. Static content or servlets can be accessed from a policy using the Call Internal Service filter. This feature is not meant to replace an enterprise J2EE server, but rather to enable you to write functionality using technology such as servlets. Configuration Profile A Configuration Profile contains the configuration information required to run the Enterprise Gateway. For example, a specific Configuration Profile instance can store certificates, users, core policies and Web Services, external connections, or listeners. A Configuration Profile can have a number of versions, which are created by users. You can use the Policy Studio to deploy Configuration Profile versions to Enterprise Gateway Processes, and to copy existing versions to create new Configuration Profiles. Process A Process is a running instance of the Enterprise Gateway. You can use Policy Studio to configure and deploy Enterprise Gateway Processes. Service Virtualization When you register a Web Service, and deploy it to the Enterprise Gateway, the Enterprise Gateway virtualizes the Web Service. Instead of connecting to the Web service directly, clients connect through the Enterprise Gateway. The Enterprise Gateway can then apply policies to messages sent to the destination Web Service (for example, to enable security, monitoring, and acceleration).