What is the difference between PING and HTTP HEAD?

Question

I have an domain name to test. Ping is ~20 ms. 'HTTP HEAD' is ~500 ms.

Why there are so big difference between them? Is this a server-side problem? Isn't there are too big difference? 25 times.

Answer 1

When you run ping it responds much quicker because is it is designed to respond immediately. It shows you approximate latency, so if you get consistent results using ping you cannot get lower latency than that.

When you run HTTP HEAD you are actually making a request to a specific page, it is processed, executed rendered and only head is returned. It has much more overhead compared to ping, that's why it is taking much longer.

Answer 2

If I'm not mistaken, a ping request is handled on the network driver level, and is extremely fast as a result (sometimes it's handled by the hardware itself, skipping software processing altogether). It will portray network latency fairly well.

An HTTP HEAD request must visit the web server, which is a user-level program, and requires copying bits of data a couple times, and web server code to parse the request, etc. The web server then has to generate the HTTP response headers for the request. Depending on the server and the requested page, this can take a while, as it has to generate the requested page anyway (It just sends you the headers only, and not the page content.)

Answer 3

Ping is usually implemented as an ICMP echo request. A simpler datagram protocol: You send a packet, the server replies with the corresponding packet and that's about it.

HTTP HEAD is still HTTP: a TCP connection must be established between both ends and the HTTP server must reply with the headers for your request. It's obviously fast but not as simple as sending a single packet response.

If you're testing a domain, ping is a more adequate tool, while HTTP HEAD is a tool better suited to test an HTTP server.

Answer 4

Well, for one, ping goes over a different protocol, ICMP. The server itself directly responds to pings. HTTP is a different protocol handled by an additional application, a web server, that must be running on the server (ping is built-in to the OS). Depending on how heavy the web server is, it could take a significant amount of time more, relative to something like a ping. Also, HEAD is sent along with a particular URL. If that URL is handled by something like ASP.NET instead of just the web server directly, then there's additional processing that must be done to return the response.