Citrix Systems CITRIX NETSCALER 9.3 Flow Records, Templates, transactionID, connectionID, tcpRTT

Citrix NetScaler Administration Guide

To help the collector link all four flows in a transaction, AppFlow adds a custom transactionID element to each flow. For application-level content switching, such as HTTP, it is possible for a single client TCP connection to be load balanced to different backend TCP connections for each request. AppFlow provides a set of records for each transaction.

Flow Records

AppFlow records contain standard NetFlow or IPFIX information, such as time stamps for the beginning and end of a flow, packet count, and byte count. AppFlow records also contain application-level information (such as HTTP URLs, HTTP request methods and response status codes, server response time, and latency) IPFIX flow records are based on templates that need to be sent before sending flow records.

Templates

AppFlow defines a set of templates, one for each type of flow. Each template contains a set of standard Information Elements (IEs) and Enterprise-specific Information Elements (EIEs). IPFIX templates define the order and sizes of the Information Elements (IE) in the flow record. The templates are sent to the collectors at regular intervals, as described in RFC 5101.

A template can include the following EIEs:

transactionID

An unsigned 32-bit number identifying an application-level transaction. For HTTP, this corresponds to a request and response pair. All flow records that correspond to this request and response pair have the same transaction ID. In the most common case, there are four uniflow records that correspond to this transaction. If the NetScaler generates the response by itself (served from the integrated cache or by a security policy), there may be only two flow records for this transaction.

connectionID

An unsigned 32-bit number identifying a layer-4 connection (TCP or UDP). The NetScaler flows are usually bidirectional, with two separate flow records for each direction of the flow. This information element can be used to link the two flows.

For the NetScaler, connectionID is an identifier for the connection data structure to track the progress of a connection. In an HTTP transaction, for instance, a given connectionID may have multiple transactionID elements corresponding to multiple requests that were made on that connection.

tcpRTT

The round trip time, in milliseconds, as measured on the TCP connection. This can be used as a metric to determine the client or server latency on the network.

httpRequestMethod

An 8-bit number indicating the HTTP method used in the transaction. An options template with the number-to-method mapping is sent along with the template.

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