[wp-hackers] Ping and trackbacks.

[Scott Merrill]

Craig Hartel wrote:
> Okay...here's a good question for you folks. We all wish there was one 
> standard RSS, I'm sure, just like we want one standard for browsers and 
> so on. So, how come "we" have both track and pingbacks. I have never 
> been able to explain this to someone on the forums. I myself don't 
> understand the differences.

I added this layman's explanation to the Codex some time ago:
http://codex.wordpress.org/Introduction_to_Blogging#Pingback_and_trackback

Does that help at all?

> So, good coders, why can't we have a simple ping? Why can't it be one 
> simple, straight-forward little thing? I realize that some pings are to 
> a specific URI, while others are simply to a URL, but what is it about 
> them that prevents them from being merged into oneness?

Trackbacks send some portion of the data from the originator to the 
recipient, as kind of a teaser or preview.  This snippet is generally 
displayed inline with regular comments.

Pingbacks send only the ping, with no content.  Pingbacks are generally 
best thought of as "off-site comments", and the ping is intended to let 
the ping recipient know that the ping originator has something to say 
about the matter.

Pingbacks were designed to overcome many of the deficiencies of 
trackbacks.  There's no verification of trackbacks: it's a one-way 
communuication from trackback originator to trackback recipient. 
Pingbacks are a two-way connection, in which the pingback recipient will 
actually make a new connection to the pingback originator to confirm 
that the ping is coming from a legitimate source.

Pingbacks are harder to spoof (though not impossbile), and can therefore 
be considered as more "authoritative".

Hope that helps explain why both exist -- each serves a slightly 
different purpose.