CBR Links Test

In order to optimize bandwidth usage, minimize congestions, and maximize the speed of WAN and LAN links, administrators need to define the WAN and LAN links requiring traffic acceleration in the Citrix Branch Repeater, set the bandwidth limit for each of the links for receiving/sending data, and associate each link with traffic shaping policies. But, once the configuration is complete, how can administrators test the correctness of the configuration? For this, administrators can use the CBR Links test. For each WAN and LAN link configured in the branch repeater, this test reports real-time metrics of the volume of traffic handled by the link and packet drops over the link. This way, the test reveals those links that are candidates for fine-tuning, owing to their low throughput despite the traffic shaping and acceleration rules that apply to them.

Target of the test : A Citrix Branch Repeater

Agent deploying the test : An external agent

Outputs of the test : One set of results for WAN/LAN link managed by the Citrix Branch Repeater 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.

Port

Refers to the port at which the specified host listens to. By default, this will be NULL.

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 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

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 this 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
  • AES – Advanced Encryption Standard

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.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Data transmitted

Indicates the rate at which data was sent over this link.

KB/Sec

Any attempt made to send or receive traffic faster than the link throughput can result in congestion. Therefore, the branch repeater should make sure that just about enough data is sent and received over application links to prevent congestion and optimize throughput.

If the values of these measures exceed or are dangerously close to the bandwidth limit of the link, it signals a potential congestion or slowdown of traffic over the link. It also indicates that you may have to reconfigure the branch repeater with more robust QoS and compression rules to prevent such unpleasant eventualities.

Data received

Indicates the rate at which data was received over this application link.

KB/Sec

Packets transmitted

Indicates the number of packets transmitted over this link.

Number

Any attempt made to send or receive traffic faster than the link throughput can result in congestion. Therefore, the branch repeater should make sure that just about enough data packets are sent and received over application links to prevent congestion and maximize throughput.

If the values of these measures exceed or are dangerously close to the maximum number of data packets that the link can handle, it signals a potential congestion or slowdown of traffic over the link. It also indicates that you may have to reconfigure the branch repeater with more robust QoS and compression rules to prevent such unpleasant eventualities.

Packets received

Indicates the number of packets received over this link.

Number

Data dropped during transmission

Indicates the rate of traffic not sent over this link due to QoS threshold settings.

KB/Sec

QoS (quality-of-service) is a set of policies and priorities assigned to the application traffic prioritized under traffic shaping policies in BR devices. A QoS threshold allows a sender to deliver only as much data as the branch repeater allows it to send, and this data is placed on the link at exactly the right rate to keep the link full but not overflowing. By eliminating excess data, the branch repeater is not forced to discard it. Without the branch repeater, the dropped data would have to be sent again, causing delay.

A high value for these measures could therefore indicate one of the following:

  • The link bandwidth is low and hence the branch repeater has been rightly configured with a QoS threshold that allows only limited data to be sent/received over that link; this excludes a lot of data from transmissions/receptions and maximizes the responsiveness of the link; 
  • The branch repeater has been misconfigured with a QoS threshold that forces the link to send/receive much less data than what it can handle; this causes a lot of data to be unnecessarily dropped from transmissions/receptions, affecting the quality-of-experience in the process. In this case, you may have to fine-tune the QoS policy.  

Data dropped during reception

Indicates the rate of traffic not received over this due to QoS threshold settings.

KB/Sec

Packets dropped during transmission

Indicates the number of packets not sent over this link due to QoS threshold settings.

Number

QoS (quality-of-service) is a set of policies and priorities assigned to the application traffic prioritized under traffic shaping policies in BR devices. A QoS threshold allows a sender to deliver only as much data as the branch repeater allows it to send, and this data is placed on the link at exactly the right rate to keep the link full but not overflowing. By eliminating excess data, the branch repeater is not forced to discard it. Without the branch repeater, the dropped data would have to be sent again, causing delay.

A high value for these measures could therefore indicate one of the following:

  • The link bandwidth is low and hence the branch repeater has been rightly configured with a QoS threshold that allows only limited number of packets to be sent/received over that link; this excludes a lot of packets from transmissions/receptions and maximizes the responsiveness of the link; 
  • The branch repeater has been misconfigured with a QoS threshold that forces the link to send/receive much less data than what it can handle; this causes a lot of packets to be unnecessarily dropped from transmissions/receptions, affecting the quality-of-experience in the process. In this case, you may have to fine-tune the QoS policy.  

Packets dropped during reception

Indicates the number of packets not received over this link due to QoS threshold settings.

Number