Strategies?

I've been pretty interested in siege tactics lately. See, I sell antique maps for a living, and the shop I work for just got this: 

Antonio LaFreri's 1565 plan of the siege of Malta, that same year

The siege didn't go well for the besieging Ottomans; they gave up after four months. (But I bet it wouldn't have turned out that way if those galleys cannonading the harbor had meson guns.)

In the 16th century, towns in northern Italy bankrupted themselves putting up modern fortifications. Huge amounts of money were spent on state-of-the-art defenses.

Thinking of starships as defensive weapons - the modern means of defeating other starships - then the fleet surrounding a planet is Traveller's walled city. It's silly to place your defensive fleet anywhere but where you want defended - because anything you put "forward" of that can be bypassed by fleets with good logistic chains. You place patrols and forward fleets at key locations, but your main fleet has to stay home. It's your moat. So the vast bulk of a world's shipbuilding budget must go to getting the most, best, biggest ships you can buy and putting them in orbit.

On the face of it, this seems to call for the building of big gun carrying system ships, not starships - though I dislike the notion of a fleet having no opportunity to either retreat, or to attempt pursuit of a retreating foe. An outclassed system defense boat is a dead system defense boat. A jump-capable fleet, outclassed, can still be saved for another day.

Also: I'm assuming a large Imperium Festerium: any planetary fleet is going to be, at least notionally, subject to the empire. The world may have a responsibility to provide a significant portion of its ship-build as auxiliary, or even as part of the main battle fleet. So at least half of the naval budget ought to go to jumpships,  I'm guessing. Assuming the relative scarcity of pilots, keep ship sizes up and fleet numbers down.

IN other words, the role of a fleet as an anti-siege device concentrates it on one world, and keeps it from being all over the subsector inconveniencing free traders.

 So a high pop, high tech world fleet: 45% main battle fleet:

EDIT: Owing to a fascinating discussion with TCS veterans on the CT-Starships Yahoo Group, the following revisions to the below:

BBs should be few and huge: flagships.
BE: Their escorts should be in the 20kt range and have the largest spinals possible for the size.
BCs should be as stated - but they're not strictly line of battle ships. Keep for pursuit or independent ops.
The screening ships should be smaller, harder to hit and plentiful: 2000 tons or less. Note that a larger fleet can make up for a lack of agility.

BBs: spinal mount ships supplemented with multiple bays & turrets high armor and screens, highly redundant systems, minimal carried craft, J-3 standard (or best if lower)  High escape agility is ideal, but extreme combat agility less so. The "stand and fight" ships. 70kton +, size no object.

BCs: spinal mount ships, multiple bays & turrets; less armor and redundancy, minimal carried craft, J3 or 4, high combat agility preferable for pursuit. For escort of BBs, pursuit, and independent operations. Should be in the 10-60 kton range.

BE - escorts for the battleships: their performance should match that of the BBs they escort; should be heavily armored to provide screening. 10-60 ktons, lighter spinal mounts, more granular weaponry.

Destoyers and frigates, running from 1000 to 9000 tons, should be added to a) improve strategic fleet numbers for purposes of initiative and b) provide granularity in weapons systems. The main fleet will be very meson heavy; these ships should be built around bay "spinal" weapons with a variety of turrets.

NOT a carrier navy.

50% home defense fleet:

A similar breakdown of heavily armored, highly resilient monitor craft built around the biggest mesons possible, and an array of system defense craft for pursuit and system patrol.

5% Patrol element: some variant of the T or C, upgunned, in whatever numbers available, for subsector patrol duties.