The Server Side Navigation Bar is the replacement for the old Web-Ring "HTML code fragment".
The code fragment contained the web-ring "navigation" links to the next link (web site) in the chain, a link to the ring home and to a list of the all the sites on the ring.
Code fragments were often personalized or contained custom graphics becoming a billboard advertising "the ring".
(Samples at anvilfire.com web-ring nexus)
The SSNB replaces all that with a simple, boring, corporate grey bar.
However, the important feature of the SSNB is that it is served from the ring host's computer, not from the ring member's computer.
This gives the host and the ringmaster the ability to change the content of the SSNB at any time.
Ring members do not have to update the code when there are changes.
There is also no code they CAN edit so the SSNB are always uniform (supposedly).
One of the important uses of the SSNB is to determine if a member site has the linking code installed.
IF it is installed then any time the page is loaded the host can tell when and by whom since they are supplying part of the page.
It replaces the "Ring Checker" that was launched earlier this year.