Real Server Test

Real servers are dedicated physical servers that you typically configure in groups called real server groups. The Radware Alteon Load Balancer distributes incoming network traffic and session load across a real server group.

Typically, the real servers in a group are bound to a virtual server. Whenever a client request is received, the virtual server bound to a real server group responds to those requests by routing the requests to those real servers in that group that are currently available. Load distribution can be done in different ways. The load balancer may use a round-robin method, where each server is used in turn. It can also use a weighted round robin system, where servers are assigned traffic based on their configured capabilities. Regardless of which load balancing technique/algorithm is used, the aim is to ensure that no single real server is overloaded with requests.

If one/more real servers in the group are unavailable, then the load should be shared by the other real servers in the group. However, if at any given point in time, one/more real servers in a group handle a significantly higher session and/or data load than the rest, it is a clear indicator of ineffective load-balancing! Under such circumstances, administrators may have to fine-tune/change the load-balancing algorithm.

To be able to quickly and accurately spot load-balancing irregularities and to initiate remedial measures, administrators should keep a close watch on the availability of each real server in a group and the session and data load handled by each server. This is what the Real Servers Test does!

For each real server in a group, this test reports the availability and operational status of the server. In addition, the test also enables you to analyze the impact of the unavailability (if any) of a server on the load imposed on other servers in the group by reporting the total session load on each server and data handled by every server in the group. This way, the test sheds light on issues in load-balancing, and thus urges administrators to take appropriate corrective action.

Target of the test : A Radware Alteon Load Balancer

Agent deploying the test : An external agent

Outputs of the test : One set of results for each real server in every server group that is mapped to a virtual server

Configurable parameters for the test
Parameter	Description
Test period	How often should the test be executed
Host	The IP address of the Radware Alteon load balancer that is being monitored.
SSH Port	Besides SNMP, this test also uses the Radware CLI to pull metrics on real servers. To run the CLI commands, the test first needs to establish an SSH connection with the Radware Alteon load balancer. To enable the test to establish this connection, specify the SSH Port here.
SSH Username, SSH Password, and Confirm Password	As stated earlier, this test also uses the Radware CLI to pull metrics on real servers. To use the CLI, the test first needs to connect to the Radware Alteon load balancer via SSH, and then run commands using CLI. For running the commands, this test requires the privileges of a valid SSH user with permission to run the CLI commands. Specify the user name and password of such a user against SSH UserName and SSH Password text boxes, and confirm the password by retyping it in the Confirm Password text box.
SNMPPort	The port at which the monitored target exposes its SNMP MIB; the default 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 firewall. 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.
Detailed Diagnosis	To make diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option. The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled: The eG manager license should allow the detailed diagnosis capability Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.

Measurements made by the test

Measurement

Description

Measurement Unit

Interpretation

Status

Indicates the current status of this real server.

The values that this measure can report and their corresponding numeric values are as follows:

Measure Value	Numeric Value
Running	2
Disabled	4
Failed	5

Note:

By default, this measure reports one of the Measure Values listed in the table above to indicate the status of the real server. In the graph of the measure however, the real server status is indicated using the corresponding numeric equivalents only.

Use the detailed diagnosis of this measure to determine the IP address of the real server.

Current sessions

Indicates the number of sessions currently handled by this real server.

Number

Compare the value of this measure across real servers in a particular group to determine whether/not session load has been uniformly distributed across the servers in that group. If load distribution is not uniform, then identify which real server has handled a significantly higher session load than the rest. You will then have to investigate the reasons for this load-balancing faux pas - is it because the other servers in the group are unavailable? If this is not the case, then you may have to fine-tune the load-balancing algorithm.

Total sessions

Indicates the total number of sessions handled by this real server from the time it was started.

Number

Was real server down?

Indicates whether/not this real server was down even once during the last measurement period.

The values that this measure can report and their corresponding numeric values are as follows:

Measure Value	Numeric Value
Yes	1
No	0

Note:

Data transfer rate

Indicates the rate at which data was handled by this real server.

MB/Sec

Compare the value of this measure across the real servers in a group to figure out if any particular server is handling a significantly higher data load than the others in the group. If so, this could hint at a load-balancing irregularity. You may want to investigate the reasons for this - could it be because the other servers are unavailable? If this is not the case, you may want to fine-tune the load-balancing algorithm.