Wandering Thoughts archives

2008-06-11

Designing a usable DNS Blocklist result format

It's relatively common for DNS blocklists to want to encode a certain amount of information in their results, ranging from the source of the information to how reliable they consider the results. For sensible reasons, DNS blocklists have to encode this information in the IP address or addresses that they return.

As it turns out, there is a useful way and a not so useful way to encode this information, because of the limitations of mailer support for DNSBL lookups. Most mailers can ask only two questions: 'is this host listed at all?' and 'is this host listed with a specific IP address?'

(Even when mailers support more, I believe that those two are the easiest two conditions to use.)

There are two natural ways to encode multiple pieces of information in DNSBL results. One of them is to return multiple IP addresses, each one representing one piece of information; the other is to encode all of the information into a single IP address (using several octets, or encoding an octet by ORing flags together, or both). Now consider what happens if you want to know only one piece of information in your mailer, for example 'is this host blocked with high confidence'.

If the DNSBL encodes multiple pieces of information in a single IP address and you want only one piece, you probably have no good way of extracting it and matching on it; instead you have to inventory all of the different IP addresses that it might be encoded into. However, if the DNSBL encodes the information into multiple IP addresses, you have a simple check; 'does the DNSBL return IP <X> for this host'.

Thus, I believe that the most useful and best way for DNSBLs to encode multiple pieces of information is to return multiple IP addresses for each lookup, each one encoding one specific bit of information. Encoding several pieces of information in one IP address only makes sense if you are very confidant that most people will want to use them together and will never want to check just one.

spam/UsableDNSBLResults written at 23:54:51; Add Comment

Tabs versus windows, or why I usually want windows

Tabs versus windows is one of those eternal debates (well, now that we can have the debate at all). For a long time I was strongly on the window side, to the point where I didn't use tabs in Firefox at all, but I've recently relented a bit on my dislike.

For me, the core difference between the two is that windows can overlap, can be moved independently, and can be organized freely (in two dimensions). Tabs are inherently non-overlapping, and thus for me they only work for things where I only ever want to see one of a number of things and do not want to organize the things separately.

(I make heavy use of icon and window positions for organizing my desktop and keeping track of what is what and how things relate to each other.)

Similarly, it's easy to see the appeal of tabs to someone who runs all of their applications maximized; tabs are lighter weight and enable useful features, and such people don't use overlapping windows anyways. I also feel that separate windows are less useful and more annoying if you're using a window manager that auto-places new windows, because then new tabs are more predictable and controllable than new windows.

Given that most people use auto-placing window managers and (judging from what I see around here) many of them almost always use maximized or near-maximized windows, I am not terribly surprised at the popularity of tabs.

Sidebar: an ideal harmonious world of tabs and windows

In my ideal world, tabs and windows cooperate: you can rip off any tab into a new window, and you can dock any window back into a tab (or a bunch of tabs, if the window is a multi-tab one). This would make it easy to use both, moving back and forth where I was mistaken about what I was going to be using something for.

Right now, my major tab-using application is Firefox. While there are Firefox extensions for better tab handling, I don't think any of them can do this particular set of tricks; the closest I've seen is one that will collapse all of your current Firefox windows into tabs in one window, which is violently not what I want.

programming/TabsVsWindows written at 00:39:56; Add Comment


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