Configuring an IP SLAs HTTP Operation
This chapter describes how to configure an IP Service Level Agreements (SLAs) HTTP operation to monitor the response time between a Cisco device and an HTTP server to retrieve a web page. The IP SLAs HTTP operation only supports the normal GET requests.
About IP SLAs HTTP Operations
An HTTP request can be made through a proxy server.
The HTTP operation measures the round-trip time (RTT) between a Cisco device and an HTTP server to retrieve a web page. The HTTP server response time measurements consist of three types:
DNS lookup - RTT taken to perform a domain name lookup.
TCP Connect - RTT taken to perform a TCP connection to the HTTP server.
HTTP transaction time - RTT taken to send a request and get a response from the HTTP server. The operation retrieves only the home HTML page.
The HTTP operation first performs the DNS operation and measures the DNS RTT. Once the domain name is found, the HTTP operation performs a TCP Connect operation to the appropriate HTTP server. The HTTP operation then measures the TCP connect RTT. Finally, the HTTP operation sends a HTTP request to retrieve the home HTML page from the HTTP server. The HTTP operation then measures the RTT to retrieve the home HTML page. The HTTP operation makes another last measurement called "the time to first byte". This measures the time from the start of the TCP Connect operation to the first HTML byte retrieved by the HTTP operation. The total HTTP RTT is a sum of the DNS RTT, the TCP Connect RTT, and the HTTP RTT. You can use the total HTTP RTT to monitor Web server performance levels by determining the RTT taken to retrieve a web page.
For GET requests, IP SLAs will format the request based on the specified URL.
Restrictions for IP SLAs HTTP Operations
IP SLAs HTTP operations have the following restrictions:
IP SLAs HTTP operations only support the HTTP GET probe on the Cisco Nexus 9300 and 9500 Series switches beginning with Cisco NX-OS Release 7.0(3)I6(1).
Setting the frequency to less than 60 seconds increases the number of packets sent. However, this might impact the performance of IP SLA operations when a scheduled operation has the same start time.