Before we prepare for the interview first there are couple of terms that you need to know.
Lot of services and roles involved, and unless you have done your research it can be troublesome to get the overview you need.So hopefully you will be able to understand a bit more about how xenapp communicates after you have read this post.
Zones
A zone is a grouping of XenApp servers that communicate with a common data collector. In large farms with multiple zones, each zone has a server designated as its data collector. Data collectors in farms with more than one zone function as communication gateways with the other zone data collectors. The data collector maintains all load and session information for the servers in its zone. All farms have at least one zone, even small ones. The fewest number of zones should be implemented, with one being optimal. Multiple zones are necessary only in large farms that span WANs.
Data Store port 1433 for MSSQL server
The data store is the database where servers store farm static information, such as configuration information about published applications, users, printers, and servers. Each server farm has a single data store.
This usually resides on a MSSQL server.
Data Collector
A data collector is a server that hosts an in-memory database that maintains dynamic information about the servers in the zone, such as server loads, session status, published applications, users connected, and license usage. Data collectors receive incremental data updates and queries from servers within the zone. Data collectors relay information to all other data collectors in the farm. By default, the data collector is configured on the first server when you create the farm, and all other servers configured with the controller server mode have equal rights to become the data collector if the data collector fails. When the zone’s data collector fails, a data collector election occurs and another server takes over the data collector functionality. Farms determine the data collector based on the election preferences set for a server. Applications are typically not published on the data collector.
Web Interface
The Web Interface is where where users access their applications using either Receiver (PNagent service site) or a Web browser.
Citrix XML Broker and the Web Interface
The Citrix XML Broker functions as an intermediary between the other servers in the farm and the Web Interface. When a user authenticates to the Web Interface.The XML Broker Receives the user’s credentials from the Web Interface and queries the server farm for a list of published applications that the user has permission to access. The XML Broker retrieves this application set from the Independent Management Architecture (IMA) system and returns it to the Web Interface.
Independent Management Architecture (IMA) port 2512
Is a service that is used for transferring the background information between Xenapp servers, including server load, current users and connections, and licenses in use.
Independent Computing Architecture (ICA) port 1494
Is a protocol that is used for client-to-server connections.
Local Host Cache (LHC)
A local cache of the data store, which allows a server to function in the absence of data store.
I have setup a basic diagram here, which contains a basic setup in Xenapp. Which consists of a
1 * data collector
1 * data store
1 * web interface
And a bunch of Xenapp servers.
And of course we have the users that connect from the wan to the servers.So lets go trough a couple of scenarios.Q.What happens when you add a new server to this farm (lets say server 4)
1: Server 4 via the IMA service establishes a connection to the data store for the farm. The service then downloads the information it needs to initialize. It also check that the data in the LHC is current.
2: When the IMA service is the started, it registers with the data collector for the farm and publishes what applications the server is contributing to.
Q.What happens when a client connects to a server? (lets say client 1)
1: The client requests the data collector to resolve the published application to the IP address of the least loaded servers in the farm.
2: The Data collector checks what server has the published applications available, and has the least load.
3. The client then connects to the least loaded server returned by the data collector.
4. The member server then updates its information to the data collector via the IMA service.
Q.What happens if the Data collector goes down ?
1. Data collector server goes down.
2. The servers in the zone recognize that the data collector has gone down and start the election process. In this example the back up data collector is elected as the new data collector for the zone.
3. The member servers in the zone then send all of their information to the new data collector for the zone. This is a function of the number each server has of sessions, disconnected session, and applications.
4. In turn, the new data collector replicates this information to all other data collectors in the farm.
(Incase you have to set a preferred backup data collector) http://support.citrix.com/proddocs/topic/xenapp65-admin/ps-console-zones-config-v2.html
Even if a Data collector is unavailable the servers will continue to function. The users that are already logged in will not be affected.
Q.What happens if a update a setting on a Xenapp server?
1. you make some changes in the Appcenter Server Console affecting all the servers in the farm.
2. The server that the Appcenter Console is connected to updates its LHC and write the change to the data store via IMA.
3. The member server then forwards the change to the data collector for the zone in which it resides. The data collector updates its LHC.
4. The data collector in turn forwards the change to all the member servers in its zone. All servers update their LHCs with the change.
Q.What happens if the Data store goes down ?
1. Data store Server goes down (And you have a backup from the Data store available, If you don’t you would have to recreate all the farm settings) dsmaint backup takes a backup of the data store.
2. Run a dsmaint migrate to migrate the settings to a new data store.
Even if a Data store is unavailable the LHC contains enough information about the farm to allow normal operations for an indefinite period of time. However, no new information can be published, or added to the farm, until the farm data store is online.
If you need to start from scratch with a new data store, prepare a new data store the way you did before configuring XenApp and run the Server Configuration Tool from any farm server. After running the Server Configuration Tool, manually reenter the lost settings. If you use the same name as he previous data store, you do not need to reconfigure the farm servers.
Q.Explain Citrix Logon Process.
- Users types their credentials, it is forwarded from XML then to IMA service in HTTP (or HTTPS) form.
- The IMA then forwards the credential data to local Lsass.exe (lsass.exe” is the Local Security Authentication Server. It verifies the validity of user logons to your PC or server).
- The Lsass.exe encrypts the credentials then passes them to the domain controller.
- The DC returns the SIDs (user’s SID and the list of group SIDs) to Lsass.exe and to IMA.
- IMA used the SIDs to search the Local Host Cache (LHC) for a list of applications and the Worker Group Preference policy for that authenticated user.
- The list of the applications together with the user’s worker group preference policy are returned to the Web Interface.
- The Web Interface returns the web page to the web browser with the list of applications
- Web Interface passes the application information together with the user’s Worker Group Preference policy back to IMA on the XML broker server.
- It then forwards to the IMA service on the Zone Data Collector.
- The Zone Data Collector tries to find out a least loaded server according to the Worker Group preference list.
- When it finds the least loaded server, it sends a query to the Citrix Service Manager of that server to verify whether the server has the required application installed, if the answer is yes, it then provides this server’s host ID to the XML broker.
- The XML broker translates this host ID into it’s IP address by searching the LHC.
- The IP address is then provided to Web Interface and it creates the ICA file.
- The ICA file is then returned to Web browser on the client machine.
- Citrix online Web plug-in uses the ICA file to launch an ICA connection to the least loaded XenApp server.
- The XenApp server launches the application for the user
Q.Purpose of Zone
Zone is subset of Farm. It is a grouping of Presentation Servers that shares the common Data Collector
Q.When would you suggest creating new zones?
Zone is subset of Farm. It is a grouping of Presentation Servers that shares the common Data Collector
Q.When would you suggest creating new zones?
Presentation Server is part of a disaster plan that fails over to an alternate location
The same published applications are hosted in multiple zones
User-specific backend data is located in other locations than the main data center
Communicating with the XenApp farm / XenDesktop zones; the XML broker
Generating and validating secure ticket to authorize users, the Secure Ticket Authority (STA)
Q.Citrix Ports:
Communication
|
Default port
|
Configuration
|
Delivery Services Console/Access Management Console
|
135
|
Not configurable
|
Citrix SSL Relay
|
443
|
See Using the SSL Relay with the Microsoft Internet Information Server (IIS)
|
Citrix XML Service
|
80
|
See Installing and Configuring XenApp
|
Client-to-server (directed UDP)
|
1604
|
Not configurable
|
ICA sessions (clients to servers)
|
1494
|
See XenApp Command Reference for information about using the ICAPORT command
|
License Management Console
|
8082
|
See Licensing Your Product
|
Server to license server
|
27000
|
In the console, open the farm or server properties page, and select License Server
|
Server to Microsoft SQL Server or Oracle server
|
139, 1433, or 443 for MS-SQL
|
See the documentation for the database software
|
Server to server
|
2512
|
See XenApp Command Reference for information about using the IMAPORT command
|
Q. How big a zone can get?
It’s just a matter of looking at the traffic patterns. For instance, do you want one single data collector updating 1000 servers whenever you make a change to the environment (one zone), or do you want two data collectors to each update only 500 servers (one zone).
Q. When would you suggest creating new farm?
When you want the member servers talk to different datastore – like a test environment;
Q. What is a Data Store?
This is the place where all the static information are stored. Farm configuration information, Published Application configurations, Server configurations, Static policy configuration, XenApp administrator accounts, and Printer configurations) that all servers can refer.
Q. How to migrate datastore database from SQL2000 to SQL2005 OR How to recover datastore database?
Restore the DB to new server
Change mf20.dsn on all servers starting with data collectors
Restart IMA service on all servers
Q. How to find out the datastore database server name?
Examine the DSN file which contains the connection details to the database.
Examine the DSN file which contains the connection details to the database.
C:\Program Files\Citrix\Independent Management Architecture\MF20.dsn
The following is an example of an MF20.dsn file from a server connecting to a remote SQL Server instance:
[ODBC]
DRIVER=SQL Server
UID=useraccount
Address=MySqlServer,1433
Network=DBMSSOCN
DATABASE=myfarmdb
WSID=MyMfServer
APP=Citrix IMA
SERVER=MySqlServer
Q. How to verify Datastore DB connectivity?
To determine if a server is communicating regularly with the data store, check the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\CITRIX\IMA\DataStoreFailureTime
If the value is all zeros, the MetaFrame server is communicating with the data store.
Q. How often does the member servers check datastore database?
By default, every 30 minutes.
Q. what happens if datastore connectivity is lost?
If the server loses its connection to the central data store, there’s no limit to how long it will continue to function. (In MetaFrame XP, this is limited to 48 or 96 hours, but that was because the data store also store license information.) But today, the server can run forever from the LHC and won’t even skip a beat if the central connection is lost. In fact now you can even reboot the server when the central data store is down, and the IMA service will start from the LHC with out any problem. (Older versions of MetaFrame required a registry modification to start the IMA service from the LHC.)
Q. How will you remove Citrix server from the farm?
If the server is unresponsive, remove it by right click on server in the console.
For functional server, remove it from add/remove programs
use CHFARM command
Q. How will you remove citrix server from the datastore DB?
When citrix is uninstalled from the server, it cleans the entry from data store database. Additionally you can run this command to remove the entry from Datastore DB.
DSCHECK /servername
Q.How to clean up datastore database?
DSCHEK without parameters will check for consistency and clean up the database. /clean parameter can be used to clean up specific server/application from the datastore but use with caution.
Q.How do you troubleshoot printing issues?
Check print spooler service
Check printer mapping errors in event log
Check printer driver availability n compatibility
Check printer policies for over rides
Q.Have you configured session printers?
Through policies.
Add the printer drivers first, map thee printer and then assign to user/group
Q.What are monitors in Netscaler?
Netscaler uses monitors to track the status of back end servers. These monitors can be http, tcp, ping etc
Q.What would you do if you see a service down in Netscaler?
Try pinging the actual server from netscaler CLI and verify its responding
Q.Have you configured Netscaler?
Q.Can you monitor Citrix services through EdgeSight?
Q.How do you configure alerts in EdgeSight?
Q.How many users can you host on XenApp 6.5 vs XenApp 5.0?
Q.How do you manage capacity planning?
Q.What are the challenges that you have faced in current environment?
Q.XML service is down. What happens?
Q.XML service down on serverA which has 10 applications; can you access the applications?
Q.What is Citrix XML service?
The Citrix XML server is a component of Citrix XenApp and XenDesktop that’s used to enumerates available resources and provide secure tickets for users that to use the WebInterface or CloudGateway.
XML service has two functions:
Q.How to change the port used by XML service?
By default XML service uses port 80. But citrix recommends using port 8080 inorder to avoid conflicts with IIS.
To change the port used by XML service:
In XenApp 6 and above – this can be changed via Citrix policies.
In Earlier versions – Use the ctxxmlss command-line utility. This can be done by unloading the Citrix XML Service with /u, changing the port with /r
ctxxmlss /u
ctxxmlss /r8080
An alternative method is by changing the port in the registry (and restart the Citrix XML service after changing).
Key :HKLM\System\CurrentControlSet\Services\CtxHTTP
Value: TCP Port
The value is listed in hex, you need to change the view to decimal.
Q.Explain Citrix Load Levels?
The following are explanations of the load levels:
9999 : No load balancing installed
0 to 9998 : “normal” load level
10000! : Application is disabled for this server
10000 : Load is at 100%
10001 : Out of licenses
10002 : Indicates that no ICA connections, listener is disabled, are available on that server.
20000 : Citrix server is unable to reach license server
Q.How to recover Citrix License Server?
The Citrix servers can function without contacting the license server and it is 30-days fault tolerant, and in Enterprise version an alert can be set with Resource Manager to send an email in case of License Server Connection Failure. If the license server reconnects at any time in the thirty days the problem resolves itself. If the server is not going to come back up, then the license file, digitally signed with the case-sensitive hostname of the old license server, is the critical component. The license file, a *.lic file, can be backed up to a thumb drive separately, and restored to a new server with the same name of the old license server, and the Citrix License server software installed.
Q.How to recover from IMA failing?
There are many reasons that the IMA Service doesn’t start
1. IMA Service load time
2. IMA Service subsystem
3. Missing Temp directory
4. Print spooler service
5. ODBC configuration
6. Roaming Profile
Check the Windows Registry setting: HKEY_LOCAL_MACHINESOFTWARECitrixIMARuntimeCurrentlyLoadingPlugin
If there is no value specified in the CurrentlyLoadingPlugin portion of the above Windows Registry entry then the IMA Service could not connect to the data store or the local host cache is missing or corrupt.
If a CurrentlyLoadingPlugin value is specified the IMA Service made a connection to the data store and the value displayed is the name of the IMA Service subsystem that failed to load.
If administrators see an “IMA Service Failed” error message with an error code of 2147483649 when starting the Presentation Server the local system account might be missing a Temp directory which is required for the IMA Service to run.
Change the IMA Service startup account to the local administrator and restart the server. If the IMA Service is successful in starting under the local administrator account then it is likely that a missing Temp directory for the local system account is causing the problem.
If the Temp directory is not present then manually create one as >Temp. For example: C:\Windows\Temp
Also verify that the TMP and TEMP system environment variables point to the temporary directory. Restart the server to restart the IMA Service
Q.What is new in XenApp 6.5?
Session Lingering
Session Pre-Launch
App Center
Load Evaluators assigned to Worker Groups or OUs instead of individual servers
Datastore and Zone information configured via GPO
Sesssion Only and Controller roles
Desktop Director web console can manage XenApp sessions
MultiStream ICA – ica traffic can be split into four separate TCP streams if required
Log On control feauture to drain users.
Q.Load Evaluators - Load Throttling
Reference: CTX112082 - Troubleshooting Load Balancing Issues
Extreme: 1
High: 2
Medium High: 3
Medium: 4
Low: 5
What is Speed Screen Latency Reduction?
- SLR is built into MetaFrame Presentation servers and ICA client systems that provides users to experience smooth typing, where the latency is high between ICA client and the server.
How do you remove a dead server from the Citrix Management Console?
Q.What is ICA and what is the advantage of ICA?
The Independent Computing Architecture (ICA) is the communication protocol by which servers and client devices exchange data in a server environment. ICA is optimized to enhance the delivery and performance of this exchange, even on low-bandwidth connections.
The ICA protocol transports an application’s screens from the server it is running on to the user’s client device, and returns the user’s input to the application on the server. As an application runs on a server, MetaFrame Presentation Server intercepts the application’s display data and uses the ICA protocol to send this data (on standard network protocols) to the client software running on the user’s client device.
When the user types on the keyboard or moves and clicks the mouse, the client software sends this data to the application on the server. ICA requires minimal client workstation capabilities and includes error detection and recovery, encryption, and data compression.
Citrix ICA protocol is used for remote application sessions between users and Presentation servers. The ICA protocol supports TCP/IP, NetBIOS, or IPX/SPX. Citrix ICA protocol is responsible for transmitting background information between the ICA clients and the Presentation servers, including the port mappings, drive mappings, print jobs, and sound. Only Sends Screen Updates & Mouse/Key Board Strokes. Only 30 – 35 kb/sec (Printing and File Transfer increase this) Fat Apps VS Thin Apps
Ports used by ICA:
1494: ICA Protocol on TCP (TCP + HTTP) & 1604: ICA Protocol on UDP.
Q.Describe ZDC Election Process in detail?
Incase ZDC is not be available, another server in the zone can take over that role. The process of taking the role is called ZDC election. Server Administrators should choose the Zone Data Collector strategy carefully during the farm design itself. When an election needs to occur in a zone, the winner of the election is determined by
1. Highest version of Presentation Server first
2. Highest rank (as configured in the Management Console)
3. Highest Host ID number (Every server has a unique ID called Host ID).
When the existing data collector for Zone failed unexpectedly or the communication between a member server and the Zone Data Collector for its zone failed or the communication between data collectors failed, then the election process begins in the Zone. If the server is shutdown properly, it triggers the election process before it goes down. The servers in the zone recognize the data collector has gone down and starts the election process. Then the ZDC is elected and the member servers send all of their information to the new ZDC for the zone. In turn the new data collector replicates this information to all other data collectors in the farm.
Note: The data collector election process is not dependent on the data store. If the data collector goes down, sessions connected to other servers in the farm are unaffected .The data collector election process is triggered automatically without administrative interference. Existing as well as incoming users are not affected by the election process, as a new data collector is elected almost instantaneously.
C:\ QueryHR.exe
------ Showing Hosts for "10.22.44.0" ------
Host 1:
-----------------------------
Zone Name: 10.22.44.0
Host Name: TEDDYCTX02
Admin Port: 2513
IMA Port: 2512
Host ID: 4022
Master Ranking: 1
Master Version: 1
---------------------------------
------ Show Host Records Completed -------
To see the Host ID number and its version, run queryhr.exe utility (with no parameters).
Each server in the zone has a rank assigned to it. The administrator can configure such that the servers in a zone can be ranked to make the server as the most desired to serve as the zone master or ZDC. The ties between servers with the same administrative ranking are broken by using the HOST IDs assigned to the servers.
When a Presentation Server starts or when the IMA service starts, the IMA service starts trying to contact other servers via the IMA protocol on port 2512 until it finds one that’s online. When it finds, it queries it to find out which server is acting as the data collector. The winner of this Zone Data Collector election is determined by the newest version of the IMA service. We can control which server will act as data collector by keeping that server the most up-to-date.
Data Collection Election Priority
Whichever server has the most recent version of the IMA Service running. (This may include hotfixes) and the server with the highest preference set in the data store
Basically data collectors and data store are not really related. The data store holds permanent farm configuration information in a database, and the data collector tracks dynamic session information in its RAM.
In addition to their primary role to provide dynamic farm information for admin consoles or for incoming connection requests, data collectors also take part in the distribution of configuration changes to Presentation Servers in the farm. When we make a changes in a presentation server that change is written to the local host cache of whichever server we connected to, and then immediately replicated to the data store. Presentation Server only looks for changes in the central data store every 30 minutes. Whenever a change is made to the data store, that change is sent to the data collector for the zone.
The data collector then distributes that change (via IMA port 2512) to all of the servers in its zone, allowing each server to update its own local host cache accordingly. Furthermore, if we have more than one zone, the initial data collector contacts the data collectors in the other zones. It sends its change to them, and in turn those data collectors forward the change to all of the servers in their zones.
Coolest part is if the change is larger than 64k, the data collectors don't send the actual change out to its zone. Instead they send out a notification which causes the servers in the zone to perform an "on demand" sync with the central data store. However it's rare for a single change to be more than 64k in size.
The data collector election priority settings in the management console
Presentation Server Java Management Console > Right-click on farm name >Properties > Zones > highlight server > “Set Election Preference”
We can totally control which server is our data collector by manually setting the preferences in the Java console. We can manually configure four levels of Zone's Data Collector election preference options
Most Preferred
Preferred
Default Preferred
Not Preferred
The important thing to remember is that these preferences will be ignored if a newer server is up for election.
Q.How Load Evaluator works?
QFARM /LOAD command executed in a Presentation Server farm will display all servers in the farm along with each server’s respective load value. Each and every Presentation Server generates its own “score” and sends this information to the data collector in the respective zone. This score will be a decimal number between 0 and 10,000, with zero representing a “no load” situation, and 10,000 indicating the particular server is fully loaded and is not accepting any more connections. Citrix Load Management is handled by load evaluator and its simply a set of rules that determine a particular server’s “score”, or current load value. It is the “score” that determine the decisions that distribute loads within the server farm. Load evaluators can be applied to servers and/or published applications. If any servers in the Zone go down then Load Evaluators are used to overcome the situation. In default XenApp installation there are Advanced and Default Load Evaluators are there.D
Default Load Evaluator includes only two rules, Load Throttling and Server User Load.
Advanced Load Evaluator includes four rules, CPU Utilization, Load Throttling, Memory Usual and Page Swaps.
Q.How Zone Preference and failover configured?
Zone preference and failover can be configured from Policies. It is located in User Workspace > Connections in Citrix Policy. You can select the server group in which order the connections are preferred. This is useful when an entire zone goes down
Q.What is Preferred Load Balancing?
Preferred Load balancing is the feature in XenApp Platinum edition, which allows you to configure preference for the particular users to access the applications in the XenApp farm.
We can see this in Server properties in Advanced Management Console. In Memory/CPU > CPU Utilization Management, there will be the third option called "CPU sharing based on Resource Allotments"
To give more resources to particular application in the server, we can configure in Application properties > Advanced > Limits and Application important in Access Management Console. So if you set the Application importance to High, then when those application is used by the users will get more CPU cycles than the users accessing other applications
To give more resources to the users, we can configure it in Citrix Policies in XenApp Advanced Configuration. To enable it go to the policy properties > Service Level > Session Importance > enable, and assign preferred Importance Level (High, Medium, Low).
Application Importance + Session Importance = Resource Allotmment.
Q.What are the different Types of Citrix Load Evaluators?
1. CPU Utilization
2. Memory Utilization
3. Page Swap
4. Application User Load
5. Context Switches
6. Disk Data I/O
7. Disk Operations
8. IP Range
9. Page Faults
10. Scheduling
11. Server User Load
Q.How to recover from IMA failing?
There are many reasons that the IMA Service doesn't start
1. IMA Service load time
2. IMA Service subsystem
3. Missing Temp directory
4. Print spooler service
5. ODBC configuration
6. Roaming Profile
Check the Windows Registry setting: HKEY_LOCAL_MACHINESOFTWARECitrixIMARuntimeCurrentlyLoadingPlugin
If there is no value specified in the CurrentlyLoadingPlugin portion of the above Windows Registry entry then the IMA Service could not connect to the data store or the local host cache is missing or corrupt.
If a CurrentlyLoadingPlugin value is specified the IMA Service made a connection to the data store and the value displayed is the name of the IMA Service subsystem that failed to load.
If administrators see an "IMA Service Failed" error message with an error code of 2147483649 when starting the Presentation Server the local system account might be missing a Temp directory which is required for the IMA Service to run.
Change the IMA Service startup account to the local administrator and restart the server. If the IMA Service is successful in starting under the local administrator account then it is likely that a missing Temp directory for the local system account is causing the problem.
If the Temp directory is not present then manually create one as >Temp. For example: C:\Windows\Temp
Also verify that the TMP and TEMP system environment variables point to the temporary directory. Restart the server to restart the IMA Service
Q.What is Special Folder Redirection?
Special Folder Redirection (SFR) allows for the automatic redirection of server-side Special Folders to their client-side equivalents. When a user clicks on the Documents folder in their XenApp 5 session, the folder that opens will actually be the local Documents folder. When SFR is used, all file operations will take place in the client-side folder. SFR is only available when XenApp 5 is installed on Windows Server 2008 and also requires XenApp Plugin version 11 (client).
Q.What is Citrix Resource Manager?
Citrix Resource Manager (RM) is a tool that is used to manage resources on single or multiple MetaFrame servers. RM enables the ability to collect, display, store, and analyze data about system performance, application or process use, and user activity. RM provides real-time system monitoring, reporting of system activity, and billing reports to charge users for use of resources using a summary database.
In XenApp5 Resource Manager is moved to EdgeSight. We cannot connect to RMSummaryreport database from XenApp5. But still we can see some of the reports from Report Center in Access Management Console. One of the important reports is Policy Report.
Q.Application launch process in XenApp 6 and 6.5
The application listing and displaying process is as follows:
1. A user launches the Web Interface URL, it returns the logon page.
2. Users types their credentials, it is forwarded from XML then to IMA service in HTTP (or HTTPS) form.3. The IMA then forwards the credential data to local Lsass.exe (lsass.exe” is the Local Security Authentication Server. It verifies the validity of user logons to your PC or server).4. The Lsass.exe encrypts the credentials then passes them to the domain controller.5. The DC returns the SIDs (user’s SID and the list of group SIDs) to Lsass.exe and to IMA.6. IMA used the SIDs to search the Local Host Cache (LHC) for a list of applications and the Worker Group Preference policy for that authenticated user.7. The list of the applications together with the user’s worker group preference policy are returned to the Web Interface.8. The Web Interface returns the web page to the web browser with the list of applications
2. Web Interface passes the application information together with the user’s Worker Group Preference policy back to IMA on the XML broker server.
3. It then forwards to the IMA service on the Zone Data Collector.
4. The Zone Data Collector tries to find out a least loaded server according to the Worker Group preference list.
5. When it finds the least loaded server, it sends a query to the Citrix Service Manager of that server to verify whether the server has the required application installed, if the answer is yes, it then provides this server’s host ID to the XML broker.
6. The XML broker translates this host ID into it’s IP address by searching the LHC.
7. The IP address is then provided to Web Interface and it creates the ICA file.
8. The ICA file is then returned to Web browser on the client machine.
9. Citrix online Web plug-in uses the ICA file to launch an ICA connection to the least loaded XenApp server.
10. The XenApp server launches the application for the user
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