I loved Deepness In The Sky, one of the darkest ("Age of Failed Dreams", twentieth-century style authoritarianism coupled with technologies of the future, etc...) and yet most fascinating pieces of fiction. It's also one of the few (along with Vinge's other work) to depict distributed systems (in this sensor networks) in a realistic manner.

Couple of things to keep in mind though:

- With the exception of the spiders and two other aliens, most of the civilizations the Qeng Ho (another romanization of Zheng He, http://en.wikipedia.org/wiki/Zheng_He) are human. As a result (and based on their historical and software archives), they are able to understand what drives the civilization they deal with. Even then, however, contact with some of them turns out for the worse (The Emergents in this case) at least in the short term (and by short I here I mean decades -- human life is extended due to medical advances and suspended animation, and that's not taking into the account relativistic effects, e.g., by the time one comes back to their planet, the civilization on that planet may have already fallen).

- Qeng Ho is better termed as a culture: they're certainly not a government much less an empire. The book goes very deep into this angle and I won't go further to avoid plot spoilers.

- Relativistic time dilation ("grandfather paradox") plays a huge role here in travel. The civilizations rely on Bussards Ramjets (which seem to be impractical, magnetic sails would be more likely) and constant acceleration and then (from half-way point) deceleration: they're effectively marooned if they're unable to repair or refuel their "ram scoops", so they're taking bets that whenever they reach their target, the civilization on the other end is able to repair the ships. Again, that works well if the civilizations are human: even if the civilization has fallen into barbarism (like Pham Nuwen's home, Canberra -- where they've lost even radio and aircraft) it's possible to rebuild based on archaeology, knowledge of human nature (arranging deals and trades), and (as the parent mentioned) radio communications.

So I think this is where the analogy fails: it's possible to have an inter-stellar culture without faster than light travel or communications, but probably only as long as civilizations already familiar with each other are within light decades.

Fire Upon the Deep is quite fascinating in the sense of what is possible with FTL, although even there it seems that there are mostly cultures as opposed to empires (with Skroderiders -- the sci-fi aliens I want to meet most in real life! -- being the equivalent of Qeng Ho)