Virtual Server Test

The Load Balancer consists of multiple virtual servers which, in turn, consists of an IP address and port. This virtual server is bound to a number of physical servers a.k.a real servers within a server farm. A virtual server is capable of performing the following:

Distribute client requests across multiple servers to balance server load;
Apply various behavioral settings to a specific type of traffic;
Enable persistence for a specific type of traffic;
Direct traffic according to user-written rules

In addition, virtual servers can also be used in the following ways:

Directing traffic to a load balancing pool;
Sharing an IP address with a VLAN node;
Forwarding traffic to a specific destination IP address;
Increasing the speed of processing HTTP traffic;
Increasing the speed of processing Layer 4 traffic;
Relaying DHCP traffic

If the virtual servers are not able to manage the traffic and divert client requests to servers that are managing fewer requests, poor performance and outages cannot be avoided. Also, irregularities in load balancing can cause significant delay in request processing thus affecting the user experience with the load balancer. To avoid this, you can configure the periodic execution of the Virtual Server test.

For each virtual server configured on the target load balancer, this test continuously monitors the load on the load-balancing virtual servers and reveals how well each virtual server processes client requests. In addition, this test detects inconsistencies in load-balancing early on and warns administrators of possible deviations proactively.

Target of the test : A Load Balancer VA R20

Agent deploying the test : An external agent

Outputs of the test : One set of results for each Virtual server on the target load balancer being monitored

Configurable parameters for the test
Parameter	Description
Test Period	How often should the test be executed.
Host	The IP address of the host for which this test is to be configured.
SNMPPort	The port at which the monitored target exposes its SNMP MIB; The default value is 161.
SNMPVersion	By default, the eG agent supports SNMP version 1. Accordingly, the default selection in the SNMPVersion list is v1. However, if a different SNMP framework is in use in your environment, say SNMP v2 or v3, then select the corresponding option from this list.
SNMPCommunity	The SNMP community name that the test uses to communicate with the storage node. This parameter is specific to SNMP v1 and v2 only. Therefore, if the SNMPVersion chosen is v3, then this parameter will not appear.
UserName	This parameter appears only when v3 is selected as the SNMPVersion. SNMP version 3 (SNMPv3) is an extensible SNMP Framework which supplements the SNMPv2 Framework, by additionally supporting message security, access control, and remote SNMP configuration capabilities. To extract performance statistics from the MIB using the highly secure SNMP v3 protocol, the eG agent has to be configured with the required access privileges – in other words, the eG agent should connect to the MIB using the credentials of a user with access permissions to be MIB. Therefore, specify the name of such a user against this parameter.
Context	This parameter appears only when v3 is selected as the SNMPVersion. An SNMP context is a collection of management information accessible by an SNMP entity. An item of management information may exist in more than one context and an SNMP entity potentially has access to many contexts. A context is identified by the SNMPEngineID value of the entity hosting the management information (also called a contextEngineID) and a context name that identifies the specific context (also called a contextName). If the Username provided is associated with a context name, then the eG agent will be able to poll the MIB and collect metrics only if it is configured with the context name as well. In such cases therefore, specify the context name of the Username in the Context text box. By default, this parameter is set to none.
AuthPass	Specify the password that corresponds to the above-mentioned Username. This parameter once again appears only if the SNMPVersion selected is v3.
Confirm Password	Confirm the AuthPass by retyping it here.
AuthType	This parameter too appears only if v3 is selected as the SNMPversion. From the AuthType list box, choose the authentication algorithm using which SNMP v3 converts the specified username and password into a 32-bit format to ensure security of SNMP transactions. You can choose between the following options: MD5 - Message Digest Algorithm SHA - Secure Hash Algorithm SHA224 - Secure Hash Algorithm 224 bit SHA256 - Secure Hash Algorithm 256 bit SHA384 - Secure Hash Algorithm 384 bit SHA512 - Secure Hash Algorithm 512 bit
EncryptFlag	This flag appears only when v3 is selected as the SNMPversion. By default, the eG agent does not encrypt SNMP requests. Accordingly, the this flag is set to No by default. To ensure that SNMP requests sent by the eG agent are encrypted, select the Yes option.
EncryptType	If the EncryptFlag is set to Yes, then you will have to mention the encryption type by selecting an option from the EncryptType list. SNMP v3 supports the following encryption types: DES - Data Encryption Standard 3DES - Triple Data Encryption Standard AES - Advanced Encryption Standard AES128 - Advanced Encryption Standard 128 bit AES192 - Advanced Encryption Standard 192 bit AES256 - Advanced Encryption Standard 256 bit
EncryptPassword	Specify the encryption password here.
Confirm Password	Confirm the encryption password by retyping it here.
Timeout	Specify the duration (in seconds) within which the SNMP query executed by this test should time out in this text box. The default is 10 seconds.
Data Over TCP	By default, in an IT environment, all data transmission occurs over UDP. Some environments however, may be specifically configured to offload a fraction of the data traffic – for instance, certain types of data traffic or traffic pertaining to specific components – to other protocols like TCP, so as to prevent UDP overloads. In such environments, you can instruct the eG agent to conduct the SNMP data traffic related to the monitored target over TCP (and not UDP). For this, set this flag to Yes. By default, this flag is set to No.
Engine ID	This parameter appears only when v3 is selected as the SNMPVersion. Sometimes, the test may not report metrics when AES192 or AES256 is chosen as the Encryption type. To ensure that the test report metrics consistently, administrators need to set this flag to Yes. By default, this parameter is set to No.

Measurements made by the test
Measurement	Description	Measurement Unit	Interpretation
Associated real server	Indicates the number of real servers associated with this virtual server.	Number	The detailed diagnosis of this measure lists the name of the real server associated with the virtual server and the IP address through which the real server was connected to the virtual server.
Current connections	Indicates the number of connections handled by this virtual server during the last measurement period.	Number	This measure is a good indicator of load on the virtual server.
Received packets	Indicates the number of packets received by this virtual server during the last measurement period.	Number	Compare the value of this measure across the virtual servers to figure out the virtual server that is receiving the maximum number of packets.
Transmitted packets	Indicates the number of packets transmitted by this virtual server during the last measurement period.	Number	Compare the value of this measure across the virtual servers to figure out the virtual server that is transmitting the maximum number of packets.
Received data	Indicates the amount of data received by this virtual server during the last measurement period.	KB	Compare the value of this measure across the virtual servers to figure out the virtual server that is receiving the maximum amount of data.
Transmitted data	Indicates the amount of data transmitted by this virtual server during the last measurement period.	KB	Compare the value of this measure across the real servers to figure out the virtual server that is transmitting the maximum amount of data.
Received packet rate	Indicates the rate at which packets were received by this virtual server.	Packets/sec
Transmitted packet rate	Indicates the rate at which packets were transmitted by this virtual server.	Packets/sec
Received data rate	Indicates the rate at which data was received by this virtual server.	KB/sec
Transmitted data rate	Indicates the rate at which data was transmitted by this virtual server.	KB/sec