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Chapter 4 Logical DesignDuring the logical design phase of the solution life cycle, you design a logical architecture showing the interrelationships of the logical components of the solution. The logical architecture and the usage analysis from the technical requirements phase form a deployment scenario, which is the input to the deployment design phase. This chapter contains the following sections: About Logical ArchitecturesA logical architecture identifies the software components needed to implement a solution, showing the interrelationships among the components. The logical architecture and the quality of service requirements determined during the technical requirements phase form a deployment scenario. The deployment scenario is the basis for designing the deployment architecture, which occurs in the next phase, deployment design. Analysis of Logical ArchitectureA high-level logical architecture provides the basis for a low-level logical architecture. The high-level logical architecture needs to meet the business and technical needs that you previously established. The logical architecture is broken down according to the various applications that comprise the system as a whole and the way in which users interact with it. In general, the logical architecture includes Portal Server Secure Remote Access (SRA), high availability, security (including Access Manager, and Directory Server architectural components. The high- and low-level architectures also need to account for any factors beyond the control of the portal, including your network, hardware failures, and improper channel design. The low-level architecture specifies such items as the physical architecture, network infrastructure, Portal Desktop channel and container design and the actual hardware and software components. High-Level Logical ArchitectureThe high-level logical architecture to supports both the business and technical requirements and addresses questions such as:
Low-Level Logical ArchitectureLow-level architecture focuses on specifying the processes and standards you use to build your portal solution, and specifying the actual hardware and software components of the solution, including:
Portal Server ComponentsPortal Server deployment consists of the following components:
Note – See the latest Portal Server Release Notes for specific versions of products supported by Portal Server. In addition to the components that make up the portal, your design should include (but is not limited to) the following:
Additionally, you need to consider how the following three network zones fit into your design:
The logical architecture also describes the Portal Desktop look and feel, including potential items such as:
The logical architecture is where you also develop a caching strategy, if your site requires one. If the pages returned to your users contain references to large numbers of images, Portal Server can deliver these images for all users. However, if these types of requests can be offloaded to a reverse proxy type of caching appliance, you can free up system resources so that Portal Server can service additional users. Additionally, by placing a caching appliance closer to end users, these images can be delivered to end users somewhat more quickly, thus enhancing the overall end user experience. Secure Remote Access ComponentsThis section describes the following SRA components: SRA GatewayThe SRA Gateway is a standalone Java process that can be considered to be stateless, since state information can be rebuilt transparently to the end user. The Gateway listens on configured ports to accept HTTP and HTTPS requests. Upon receiving a request, the Gateway checks session validity and header information to determine the type of request. Depending on the type of request, the Gateway performs the following:
All the Gateway configuration information is stored in the Access Manager’s LDAP database as a profile. A gateway profile consists of all the configuration information related to the Gateway except. All machine-specific information, such as machine-specific information such as host name and IP address, is stored in a configuration file in the local file system where the Gateway is installed. This enables one gateway profile to be shared between Gateways that are running on multiple machines. As mentioned previously, you can configure the Gateway to run in both HTTP and HTTPS modes, simultaneously. This helps both intranet and extranet users to access the same Gateway: extranet users over HTTPS, and intranet users over HTTP (without the overhead of SSL). Multiple Gateway InstancesIf desired, you can run multiple Gateway instances on a single machine—this is referred as a multihomed Gateway. Each Gateway instance listens on separate port(s). You can configure Gateway instances to contact the same Portal Server instance, or different Portal Server instances. When running multiple instances of a Gateway on the same machine, you can associate an independent certificate database with each instance of the Gateway, and bind that Gateway to a domain. In essence, this provides the flexibility of having a different Gateway server certificate for each domain. Multiple Portal Server InstancesNote – Session stickiness is not required in front of a Gateway (unless you are using Netlet), however performance is improved with session stickiness. On the other hand, session stickiness to the Portal Server instances is enforced by SRA. ProxiesThe Gateway uses proxies that are specified in its profile to retrieve contents from various web servers within the intranet and extranet. You can dedicate proxies for hosts and DNS subdomains and domains. Depending on the proxy configuration, the Gateway uses the appropriate proxy to fetch the required contents. If the proxy requires authentication, the proxy name is stored as part of the gateway profile, that the Gateway uses automatically, when connecting to the proxy. Gateway and HTTP Basic AuthenticationThe Gateway supports basic authentication, that is, prompting for a user ID and password but not protecting those credentials during transmission from the user’s computer to the site’s web server. Such protection usually requires the establishment of a secure HTTP connection, typically through the use of SSL. If a web server requires basic authentication the client prompts for user name and password and sends the information back to the requesting server. With the Gateway enabled for HTTP basic authentication, it captures the user name and password information and stores a copy in the user’s profile in the Access Manager for subsequent authentications and login attempts. The original data is passed by the Gateway to the destination web server for basic authentication. The web server performs the validation of the user name and password. The Gateway also enables fine control of denying and allowing this capability on an individual host basis. Gateway and SSL SupportThe Gateway supports both SSL v2 and SSL v3 encryption while running in HTTPS mode. You can use the Portal Server administration console to enable or disable specific encryption. The Gateway also supports Transport Layer Security (TLS). SSL v3 has two authentication modes:
Personal Digital Certificate (PDC) authentication is a mechanism that authenticates a user through SSL client authentication. The Gateway supports PDC authentication with the support of Access Manager authentication modules. With SSL client authentication, the SSL handshake ends at the Gateway. This PDC-based authentication is integrated along with the Access Manager’s certificate-based authentication. Thus, the client certificate is handled by Access Manager and not by the Gateway. If the session information is not found as part of the HTTP or HTTPS request, the Gateway directly takes the user to the authentication page by obtaining the login URL from Access Manager. Similarly, if the Gateway finds that the session is not valid as part of a request, it takes the user to the login URL and at successful login, takes the user to the requested destination. After the SSL session has been established, the Gateway continues to receive the incoming requests, checks session validity, and then forwards the request to the destination web server. The Gateway server handles all Netlet traffic. If an incoming client request is Netlet traffic, the Gateway checks for session validity, decrypts the traffic, and forwards it to the application server. If Netlet Proxy is enabled, the Gateway checks for session validity and forwards it to Netlet Proxy. The Netlet Proxy then decrypts and forwards it to the application server. Note – Because 40-bit encryption is very insecure, the Gateway provides an option that enables you to reject connections from a 40-bit encryption browser. Gateway Access ControlThe Gateway enforces access control by using Allowed URLs and Denied URLs lists. Even when URL access is allowed, the Gateway checks the validly of the session against the Access Manager session server. URLs that are designated in the Non Authenticated URL list bypass session validation, as well as the Allowed and Denied lists. Entries in the Denied URLs list take precedence over entries in the Allowed URLs list. If a particular URL is not part of any list, then access is denied to that URL. The wildcard character, *, can also be used as a part of the URL in either the Allow or Deny list. Gateway LoggingYou can monitor the complete user behavior by enabling logging on the Gateway. The Gateway uses the Portal Server logging API for creating logs. Using Accelerators with the GatewayYou can configure accelerators, which are dedicated hardware co-processors, to off-load the SSL functions from a server's CPU. Using accelerators frees the CPU to perform other tasks and increases the processing speed for SSL transactions. NetletNetlet can provide secure access to fixed port applications and some dynamic port applications that are available on the intranet from outside the intranet. The client can be behind a remote firewall and SSL proxy, or directly connected to the Internet. All the secure connections made from outside the intranet to the intranet applications through the Netlet are controlled by Netlet rules. A Netlet applet running on the browser sets up an encrypted TCP/IP tunnel between the remote client machine and intranet applications on the remote hosts. Netlet listens to and accepts connections on preconfigured ports, and routes both incoming and outgoing traffic between the client and the destination server. Both incoming and outgoing traffic is encrypted using an encryption algorithm selected by the user, or configured by the administrator. The Netlet rule contains the details of all servers, ports, and encryption algorithms used in a connection. Administrators create Netlet rules by using the Portal Server administration console. Static and Dynamic Port ApplicationsStatic port applications run on known or static ports. Examples include IMAP and POP servers, Telnet daemons, and jCIFS. For static port applications, the Netlet rule includes the destination server port so that requests can be routed directly to their destinations. Dynamic applications agree upon a port for communication as part of the handshake. You can include the destination server port as part of the Netlet rule. The Netlet needs to understand the protocol and examine the data to find the port being used between the client and the server. FTP is a dynamic port application. In FTP, the port for actual data transfer between the client and server is specified through the PORT command. In this case, the Netlet parses the traffic to obtain the data channel port dynamically. Currently, FTP and Microsoft Exchange are the only dynamic port applications that Portal Server supports. Note – Although Microsoft Exchange 2000 is supported with Netlet, the following constraints apply:
Netlet and Application IntegrationNetlet works with many third parties such as Graphon, Citrix, and pcAnywhere. Each of these products provides secure access to the user’s Portal Desktop from a remote machine using Netlet. Split TunnelingSplit tunneling allows a VPN client to connect to both secure sites and non-secure sites, without having to connect or disconnect the VPN—in this case, the Netlet—connection. The client determines whether to send the information over the encrypted path, or to send it by using the non-encrypted path. The concern over split tunneling is that you could have a direct connection from the non-secure Internet to your VPN-secured network, via the client. Turning off split tunneling (not allowing both connections simultaneously) reduces the vulnerability of the VPN (or in the case of Netlet) connection to Internet intrusion. Though Portal Server does not prohibit nor shut down multiple network connections while attached to the portal site, it does prevent unauthorized users from “piggybacking” on other users’s sessions in the following ways:
Netlet ProxyA Netlet Proxy helps reduce the number of open ports needed in the firewall to connect the Gateway and the destination hosts. For example, consider a configuration where users need Netlet to connect with a large number of Telnet, FTP, and Microsoft Exchange servers within the intranet. Assume that the Gateway is in a DMZ. If it routes the traffic to all the destination servers, a large number of ports would need to be open in the second firewall. To alleviate this problem, you can use a Netlet Proxy behind the second firewall and configure the Gateway to forward the traffic to the Netlet Proxy. The Netlet Proxy then routes all the traffic to the destination servers in the intranet and you reduce the number of open ports required in the second firewall. You can also deploy multiple Netlet Proxies behind the second firewall to avoid a single point of failure. You could also use a third-party proxy to use only one port in the second firewall. Note – Installing the Netlet Proxy on a separate node can help with Portal Server response time by offloading Netlet traffic to a separate node. NetFileNetFile enables remote access and operation of file systems that reside within the corporate intranet in a secure manner. NetFile uses standard protocols such as NFS, jCIFS, and FTP to connect to any of the UNIX or Windows file systems that are permissible for the user to access. NetFile enables most file operations that are typical to file manager applications. ComponentsTo provide access to various file systems, NetFile has three components:
NetFile is internationalized and provides access to file systems irrespective of their locale (character encoding). NetFile uses Access Manager to store its own profile, as well as user settings and preferences. You administer NetFile through the Portal Server administration console. InitializationWhen a user selects a NetFile link in the Portal Server Desktop, the NetFile servlet checks if the user has a valid SSO token and permission to execute NetFile. If so, the applet is rendered to the browser. The NetFile applet connects back to the servlet to get its own configuration such as size, locale, resource bundle, as well as user settings and preferences. NetFile obtains the locale information and other user information (such as user name, mail ID, and mail server) using the user’s SSO token. The user settings include any settings that the user has inherited from an organization or role, settings that are customized by the user, and settings that the user has stored upon exit from a previous NetFile session. Validating CredentialsNetFile uses the credentials supplied by users to authenticate users before granting access to the file systems. The credentials include a user name, password, and Windows or Novell domain (wherever applicable). Each share can have an independent password, therefore, users need to enter their credentials for every share (except for common hosts) that you add. NetFile uses UNIX Authentication from the Access Manager to grant access to NFS file systems. For file systems that are accessed over FTP and jCIFs protocols, NetFile uses the methods provided by the protocol itself to validate the credentials. Access ControlNetFile provides various means of file system access control. You can deny access to users to a particular file system based on the protocol. For example, you can deny a particular user, role, or organization access to file systems that are accessible only over NFS. You can configure NetFile to allow or deny access to file systems at any level, from organization, to suborganization, to user. You can also allow or deny access to specific servers. Access can be allowed or denied to file systems for users depending on the type of host, including Windows, FTP, NFS, and FTP over NetWare. For example, you can deny access for Windows hosts to all users of an organization. You can also specify a set of common hosts at an organization or role level, so that all users in that organization or role can access the common hosts without having to add them for each and every member of the organization or role. As part of the NetFile service, you can configure the Allowed URLs or Denied URLs lists to allow or deny access to servers at the organization, role, or user level. The Denied URLs list takes precedence over the Allowed URLs. The Allowed URLs and Denied URLs lists can contain the * wildcard to allow or deny access to a set of servers under a single domain or subdomain. SecurityWhen you use NetFile with SRA configured for SSL, all connections made from NetFile applets to the underlying file system happen over the SSL connection established between the Gateway and the browser. Because you typically install the Gateway in a DMZ, and open a limited number of ports (usually only one) in the second firewall, you do not compromise security while providing access to the file systems. Special OperationsNetFile is much like a typical file manager application with a set of features that are appropriate for a remote file manager application. NetFile enables users to upload and download files between the local and remote file systems (shares). You can limit the size of the upload file (from the local to the remote file system) through the Portal Server administration console. NetFile also enables users to select multiple files and compress them by using GZIP and ZIP compression. Users can select multiple files and send them in a single email as multiple attachments. NetFile also uses the SSO token of Access Manager to access the user’s email settings (such as IMAP server, user name, password, and reply-to address) for sending email. Double-clicking a file in the NetFile window launches the application corresponding to the MIME type and opens the file. NetFile provides a default MIME types configuration file that has mappings for most popular file types (extensions) and MIME-types that you can edit for adding new mappings. You can search for files and display the list in a separate window using NetFile. The results of each search are displayed in a new window while maintaining the previous search result windows. The type of character encoding to be used for a particular share is user configurable, and is part of the share’s setting. If no character encoding is specified, NetFile uses ISO-8859-1 while working with the shares. The ISO-8859-1 encoding is capable of handling most common languages. ISO-8859-1 encoding gives NetFile the capability to list files in any language and to transferring files in any language without damaging the file contents. NetFile creates temporary files only when mailing files (in both NetFile Java 1 and Java 2). Temporary files are not created during uploading and downloading files between Windows file systems and the local file systems over the jCIFS protocol. Note – NetFile supports deletion of directories and remote files. All the contents of remote directories are deleted recursively. NetFile and MultithreadingNetFile uses multithreading to provide the flexibility of running multiple operations simultaneously. For example, users can launch a search operation, start uploading files, then send files by using email. NetFile performs all three operations simultaneously and still permit the user to browse through the file listing. RewriterRewriter is an independent component that translates all URIs (in both HTML and JavaScript code) to ensure that the intranet content is always fetched through the Gateway. You define a ruleset (a collection of rules) that identifies all URLs that need to be rewritten in a page. The ruleset is an XML fragment that is written according to a Document Type Definition (DTD). Using the generic ruleset that ships with the Rewriter, you can rewrite most URLs (but not all) without any additional rules. You can also associate rulesets with domains for domain-based translations. An external ruleset identifies the URI in the content. Any request that needs to be served by SRA follows this route:
|
Route for SRA Requests
|
Component Requirements |
Necessary for Best Effort Deployment? |
Necessary for NSPOF Deployment? |
Necessary for Transparent Failover Deployment? |
|---|---|---|---|
|
Yes |
Yes |
Yes |
|
|
Portal Server Building Modules |
No |
Yes |
Yes |
|
No |
Yes |
Yes |
|
|
Load Balancing |
Yes |
Yes |
Yes |
|
No |
No |
Yes |
|
|
No |
No | ||
|
No |
No |
Yes |
Note –
Load balancing is not provided out-of-the-box with the Web Server product.
Best Effort
In this scenario, you install Portal Server and Directory Server on a single node that has a secured hardware configuration for continuous availability, such as Sun Fire UltraSPARCTM III machines. (Securing a SolarisTM Operating Environment system requires that changes be made to its default configuration.)
This type of server features full hardware redundancy, including: redundant power supplies, fans, system controllers; dynamic reconfiguration; CPU hot-plug; online upgrades; and disks rack that can be configured in RAID 0+1 (striping plus mirroring), or RAID 5 using a volume management system, which prevents loss of data in case of a disk crash. Figure 4–5 shows a small, best effort deployment using the building module architecture.
Figure 4–5 Best Effort Scenario
In this scenario, for memory allocation, four CPUs by eight GB RAM (4x8) of memory is sufficient for one building module. The Portal Server console is outside of the building module so that it can be shared with other resources. (Your actual sizing calculations might result in a different allocation amount.)
This scenario might suffice for task critical requirements. Its major weakness is that a maintenance action necessitating a system shutdown results in service interruption.
When SRA is used, and a software crash occurs, a watchdog process automatically restarts the Gateway, Netlet Proxy, and Rewriter Proxy.
No Single Point of Failure
Portal Server natively supports the no single point of failure (NSPOF) scenario. NSPOF is built on top of the best effort scenario, and in addition, introduces replication and load balancing.
Figure 4–6 shows a building module consisting of a a Portal Server instance, a Directory Server replica for profile reads and a search engine database. As such, at least two building modules are necessary to achieve NSPOF, thereby providing a backup if one of the building modules fails. These building modules consist of four CPUs by eight GB RAM.
Figure 4–6 No Single Point of Failure Example
When the load balancer detects Portal Server failures, it redirects users’ requests to a backup building module. Accuracy of failure detection varies among load balancing products. Some products are capable of checking the availability of a system by probing a service involving several functional areas of the server, such as the servlet engine, and the JVM. In particular, most vendor solutions from Resonate, Cisco, Alteon, and others enable you to create arbitrary scripts for server availability. As the load balancer is not part of the Portal Server software, you must acquire it separately from a third-party vendor.
Note –
Access Manager requires that you set up load balancing to enforce sticky sessions. This means that once a session is created on a particular instance, the load balancer needs to always return to the same instance for that session. The load balancer achieves this by binding the session cookie with the instance name identification. In principle, that binding is reestablished when a failed instance is decommissioned. Sticky sessions are also recommended for performance reasons.
Multi-master replication (MMR) takes places between the building modules. The changes that occur on each directory are replicated to the other, which means that each directory plays both roles of supplier and consumer. For more information on MMR, refer to the Sun Java System Directory Server Deployment Guide.
Note –
In general, the Directory Server instance in each building module is configured as a replica of a master directory, which runs elsewhere. However, nothing prevents you from using a master directory as part of the building module. The use of masters on dedicated nodes does not improve the availability of the solution. Use dedicated masters for performance reasons.
Redundancy is equally important to the directory master so that profile changes through the administration console or the Portal Desktop, along with consumer replication across building modules, can always be maintained. Portal Server and Access Manager support MMR. The NSPOF scenario uses a multi-master configuration. In this configuration, two suppliers can accept updates, synchronize with each other, and update all consumers. The consumers can refer update requests to both masters.
SRA follows the same replication and load balancing pattern as Portal Server to achieve NSPOF. As such, two SRA Gateways and pair of proxies are necessary in this scenario. The SRA Gateway detects a Portal Server instance failure when the instance does not respond to a request after a certain time-out value. When this occurs, the HTTPS request is routed to a backup server. The SRA Gateway performs a periodic check for availability until the first Portal Server instance is up again.
The NSPOF high availability scenario is suitable to business critical deployments. However, some high availability limitations in this scenario might not fulfill the requirements of a mission critical deployment.
Transparent Failover
Transparent failover uses the same replication model as the NSPOF scenario but provides additional high availability features, which make the failover to a backup server transparent to end users.
Figure 4–7 shows a transparent failover scenario. Two building modules are shown, consisting of four CPUs by eight GB RAM. Load balancing is responsible for detecting Portal Server failures and redirecting users’ requests to a backup Portal Server in the building module. Building Module 1 stores sessions in the sessions repository. If a crash occurs, the application server retrieves sessions created by Building Module 1 from the sessions repository.
Figure 4–7 Transparent Failover Example Scenario
The session repository is provided by the application server software. Portal Server is running in an application server. Portal Server supports transparent failover on application servers that support HttpSession failover. See Chapter 9, Portal Server and Application Servers for more information.
With session failover, users do not need to reauthenticate after a crash. In addition, portal applications can rely on session persistence to store context data used by the checkpointing. You configure session failover in the AMConfig.properties file by setting the com.iplanet.am.session.failover.enabled property to true.
The Netlet Proxy cannot support the transparent failover scenario because of the limitation of the TCP protocol. The Netlet Proxy tunnels TCP connections, and you cannot migrate an open TCP connection to another server. A Netlet Proxy crash drops off all outstanding connections that would have to be reestablished.
Building Module Solution Recommendations
This section describes guidelines for deploying your building module solution.
How you construct your building module affects performance. Consider the following recommendations to deploy your building module properly:
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Deploy a building module on a single machine.
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If you use multiple machines, or if your Portal Server machine is running a large number of instances, use a fast network interconnect.
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On servers with more than eight CPUs, create processor sets or domains with either two or four CPUs. For example, if you choose to install two instances of Portal Server on an eight CPU server, create two four-CPU processor sets.
Directory Server
Identify your Directory Server requirements for your building module deployment. For specific information on Directory Server deployment, see the Directory Server Deployment Guide.
Consider the following Directory Server guidelines when you plan your Portal Server deployment:
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The amount of needed CPU in the Directory Server consumer replica processor set depends on the number of Portal Server instances in the building module as well as performance and capacity considerations.
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If possible, dedicate a Directory Server instance for the sole use of the Portal Server instances in a building module.
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Map the entire directory database indexes and cache in memory to avoid disk latency issues.
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When deploying multiple building modules, use a multi-master configuration to work around bottlenecks caused by the profile updates and replication overhead to the Directory Server supplier.
LDAP
The scalability of building modules is based on the number of LDAP writes resulting from profile updates and the maximum size of the LDAP database.
Note –
If the LDAP server crashes with the _db files in the /tmp directory, the files are lost when the server restarts. This improves performance but also affects availability.
If the analysis at your specific site indicates that the number of LDAP write operations is indeed a constraint, some of the possible solutions include creating building modules that replicate only a specific branch of the directory and a layer in front that directs incoming requests to the appropriate instance of portal.
Search Engine
When you deploy the Search Engine as part of your building module solution, consider the following:
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In each building module, make sure only one Portal Server instance has the Search Engine database containing the Resrouce Descriptors (RDs). The remaining Portal Server instances have default empty Search Engine databases.
-
Factors that influence whether to use a building module for the portal Search database include the intensity of search activities in a Portal Server deployment, the range of search hits, and the average number of search hits for all users, in addition to the number of concurrent searches. For example, the load generated on a server by the Search Engine can be both memory and CPU intensive for a large index and heavy query load.
-
You can install Search on a machine separate from Portal Server, to keep the main server dedicated to portal activity. When you do so, you use the searchURL property of the Search provider to point to the second machine where Search is installed. The Search instance is a normal portal instance. You install the Search instance just as you do the portal instance, but use it just for Search functionality.
Access Manager and Portal Server on Separate Nodes
Figure 4–8 illustrates Access Manager and Portal Server residing on separate nodes.
Figure 4–8 Access Manager and Portal Server on Different Nodes
As a result of this implementation of Portal Server and Access Manager separation, other topology permutations are possible for portal services architecture deployments as shown in the next three figures.
Two Portal Servers One Access Manager
Figure 4–9 shows two Portal Server instances configured to work with a single Access Manager and two Directory Servers where both the Access Manager and the Directory Servers operate in a Java Enterprise System Sun Clustered environment. This configuration is ideal when Access Manager and Directory Server instances are not the bottleneck.
Figure 4–9 Two Portal Servers and One Access Manager
Two Portal Servers Two Access Managers
Figure 4–10 shows a configuration for maximum horizontal scalability and higher availability achieved by a horizontal server farm. Two Portals Servers can be fronted with a load balancer for maximum throughput and high availability.
Another load balancer can be put between Portal Servers and Access Managers to achieve authentication and policy processes as a load distributor and failover mechanism for higher availability.
In this scenario, Blade 1500s can be utilized for Portal Services to distribute the load, similar Blades can be used to host Access Manager Services and Directory Services respectively. With the architecture shown in Figure 4–10, a redundancy of services exists for each of the product stack, therefore, most of the unplanned downtime can be minimized or eliminated.
However, the planned downtime is still an issue. If an upgrade or patch includes changes to the Directory Server software schema used by the Access Manager software, all of the software components must be stopped to update the schema information stored in the Directory Server. However, updating schema information can be considered a fairly rare occurrence in most patch upgrades.
Figure 4–10 Two Portal Servers and Two Access Managers
One Load Balancer Two Access Managers
Figure 4–11 shows configuration allowing authentication throughput coming from Portal Server to be load-balanced across the two Access Managers.
This configuration could be implemented when the Portal Server resides on a high-end medium to large server (that is 1 to 4 processors) with a very wide bandwidth network connection. The Access Managers with the policy and authentication services could be on two medium-size servers.
Figure 4–11 Load Balancing two Access Managers
Example SRA Logical Architectures
The SRA Gateway provides the interface and security barrier between the remote user sessions originating from the Internet and your organization’s intranet. The Gateway serves two main functions:
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Provides basic authentication services to incoming user sessions, including establishing identity and allowing or denying access to the platform.
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Provides mapping and rewriting services to enable web-based links to the intranet content for users.
For Internet access, use 128-bit SSL to provide the best security arrangement and encryption or communication between the user’s browser and Portal Server. The Gateway, Netlet, NetFile, Netlet Proxy, Rewriter Proxy, and Proxylet constitute the major components of SRA.
This section lists some of the possible configurations of these components. This section is meant only as a guide, not a complete deployment reference. Choose a configuration based on your business needs:
Tip –
To set up the authlessanonymous page to display through the Gateway, add /portal/dt to the non-authenticated URLs of the gateway profile. However, this means that even for normal users, portal pages will not need authentication and no session validation is performed.
Basic SRA Configuration
Figure 4–12 shows the most simple configuration possible for SRA. The figure shows a client browser running NetFile and Netlet. The Gateway is installed on a separate machine in the DMZ between two firewalls. The Portal Server is located on a machine beyond the second firewall in the intranet. The other application hosts that the client accesses are also located beyond the second firewall in the intranet.
The Gateway is in the DMZ with the external port open in the firewall through which the client browser communicates with the Gateway. In the second firewall, for HTTP or HTTPS traffic, the Gateway can communicate directly with internal hosts. If security policies do not permit it, use SRA proxies between the Gateway and the internal hosts. For Netlet traffic, the connection is direct from the Gateway to the destination host.
Without a SRA proxy, the SSL traffic is limited to the Gateway and the traffic is unencrypted from the Gateway to the internal host (unless the internal host is running in HTTPS mode). Any internal host to which the Gateway has to initiate a Netlet connection should be directly accessible from DMZ. This can be a potential security problem and hence this configuration is recommended only for the simplest of installations.
Figure 4–12 Basic SRA Configuration
Disable Netlet
Figure 4–13 shows a scenario similar to the basic SRA configuration except that Netlet is disabled. If the client deployment is not going to use Netlet for securely running applications that need to communicate with intranet, then use this setup for performance improvement.
You can extend this configuration and combine it with other deployment scenarios to provide better performance and a scalable solution.
Figure 4–13 Disable Netlet
Proxylet
Figure 4–14 illustrates how Proxylet enables users to securely access intranet resources through the Internet without exposing these resources to the client.
It inherits the transport mode (either HTTP or HTTPS) from the Gateway.
Figure 4–14 Proxylet
Multiple Gateway Instances
Figure 4–15 shows an extension of the SRA basic configuration. Multiple Gateway instances run on the same machine or multiple machines. You can start multiple Gateway instances with different profiles.
Figure 4–15 Multiple Gateway Instances
Note –
Although Figure 4–15 shows a 1-to-1 correspondence between the Gateway and the Portal Servers, this need not necessarily be the case in a real deployment. You can have multiple Gateway instances, and multiple Portal Server instances, and any Gateway can contact any Portal Server depending on the configuration.
The disadvantage to this configuration is that multiple ports need to be opened in the second firewall for each connection request. This could cause potential security problems.
Netlet and Rewriter Proxies
Figure 4–16 shows a configuration with a Netlet Proxy and a Rewriter Proxy. With these proxies, only two open ports are necessary in the second firewall.
The Gateway need not contact the application hosts directly now, but will forward all Netlet traffic to the Netlet proxy and Rewriter traffic to the Rewriter Proxy. Since the Netlet Proxy is within the intranet, it can directly contact all the required application hosts without opening multiple ports in the second firewall.
The traffic between the Gateway in the DMZ and the Netlet Proxy is encrypted, and gets decrypted only at the Netlet Proxy, thereby enhancing security.
If the Rewriter Proxy is enabled, all traffic is directed through the Rewriter Proxy, irrespective of whether the request is for the Portal Server node or not. This ensures that the traffic from the Gateway in the DMZ to the intranet is always encrypted.
Because the Netlet Proxy, Rewriter Proxy, and Portal Server are all running on the same node, there might be performance issues in such a deployment scenario. This problem is overcome when proxies are installed on a separate nodes to reduce the load on the Portal Server node.
Figure 4–16 Netlet and Rewriter Proxies
Netlet and Rewriter Proxies on Separate Nodes
To reduce the load on the Portal Server node and still provide the same level of security at increased performance, you can install Netlet and Rewriter Proxies on separate nodes. This deployment has an added advantage in that you can use a proxy and shield the Portal Server from the DMZ. The node that runs these proxies needs to be directly accessible from the DMZ.
Figure 4–17 shows the Netlet Proxy and Rewriter Proxy on separate nodes. Traffic from the Gateway is directed to the separate node, which in turn directs the traffic through the proxies and to the required intranet hosts.
You can have multiple instances or installations of Netlet and Rewriter Proxies. You can configure each Gateway to try to contact various instances of the proxies in a round robin manner depending on availability.
Figure 4–17 Proxies on Separate Nodes
Two Gateways and Netlet Proxy
Load balancers provide a failover mechanism for higher availability for redundancy of services on the Portal Servers and Access Managers.
Figure 4–18 Two Gateways and Netlet Proxy
Gateway with Accelerator
You can configure an external SSL device to run in front of the Gateway in open mode. It provides the SSL link between the client and SRA. For information on accelerators, see the Sun Java System Portal Server 6 Secure Remote Access 2005Q4 Administration Guide
Figure 4–19 SRA Gateway with External Accelerator
Netlet with 3rd Party Proxy
Netlet with 3rd Party Proxy illustrates using a third-party proxy to limit the number of ports in the second firewall to one. You can configure the Gateway to use a third-party proxy to reach the Rewriter and the Netlet Proxies.
Figure 4–20 Netlet and Third-Party Proxy
Reverse Proxy
A proxy server serves Internet content to the intranet, while a reverse proxy serves intranet content to the Internet. Certain deployments of reverse proxy are configured to serve the Internet content to achieve load balancing and caching.
Figure 4–21 illustrates how you can configure a reverse proxy in front of the Gateway to serve both Internet and intranet content to authorized users. Whenever the Gateway serves web content, it needs to ensure that all subsequent browser requests based on this content are routed through the Gateway. This is achieved by identifying all URLs in this content and rewriting as appropriate.
Figure 4–21 Using a Reverse Proxy in Front of the Gateway
Deployment Scenario
The completed logical architecture design by itself is not sufficient to move forward to the deployment design phase of the solution life cycle. You need to pair the logical architecture with the quality of service (QoS) requirements determined during the technical requirements phase. The pairing of the logical architecture with the QoS requirements constitutes a deployment scenario. The deployment scenario is the starting point for designing the deployment architecture, as explained in Chapter 5, Deployment Design.