For most all folks today, their first physical hop or link, is to their ISP.
A GAA performing active timing attack, in the way of suspending your internet link for say 500 ms, is not possible to defend against when you have no other links for onboarding.
Acess censorship is separate from what the first overlay net node you connect to decides to do with the adverary modulated garbage they received from your node. That first node, or any other node, should drop you until you behave, assigning the bandwidth and timing contract they negotiated with you to a better participant in the meantime.
active link suspension across target sets of end users, bisecting as needed to map end user nodes to destination/ server streams of interest.
So what, a secure overlay should drop its apparently contract breaking nodes (as so affected by adversary whether by cutout or other modulation) up to and including the remaining overlay progressively cutting out thus effectively downing itself as protection in reaction to increasing adversary scopes of aggression. A net can't call itself secure if it is stupid enough to stay up under known successful attack methods, operational yes, secure no.
the less your enemy can hide, the better.
An estimate is required to determine if G* adversary can actually sustain modulation for traffic analysis against millions of nodes at once for what duration of time... if adversary cannot hold a self-defensive network down and out as such, the overlay wins, and adversary is relegated to a mere annoyance randomly sinking nodes as a sore loser for lols.
QoS, lo / hi priority
People first have to solve old problems with those... - Users declaring all their traffic as hi, because. - The overlay must see inside all traffic to inspect and classify, no go. - The overlay must becomes the State offering only proprietary apps that it can controls, boring limited. - Users pay for play to the overlay, complex. Users are paying ISP for what rate they choose to pass over their NIC. Most all overlays have always been able to handle user traffic because there are more than enough wheat-idle nodes to carry for example low quality video over 7 hops, or mid quality youtube over 3. Unlike Tor, if as in Phantom every user is a relay, there should be plenty of excess wheat-idle capacity because users are mostly idle.
Phone calls require QoS.
Both the Internet and Tor have no QoS, yet users have been able to hold voice and IRC conversations between Tor onions since day one, with some even being able to stuff low quality video calls over it as well. In a fill network, so long as fill yields to for wheat demand, the only real constraint seems how the overlay's transport such as TCP / UDP and or some proprietary bucket transport handle congestion when two or more users traffic shares the same physical path between nodes.
I don't understand the consideration
Overall point was, are people building some overlay to handle only one app (messages, storage, IRC, whatever), or a general purpose transport overlay like the internet that can carry whatever. Presuming both can be done equally securely and performant, there is no point to do the former. Lots of research and nets out there "We're building an overlay for this specific app". That being, much more research needs done in area of application agnostic, general purpose transport, traffic analysis resistant, networks. If you can figure out how to do the latter, the former is entirely moot. Study the latter first.
In an overlay net, we think of a link as peer to peer.
But physically that link is usually as follows:
NodeA -> ISP1 router -> GT-1 router ... ... -> ISP2 router -> NodeB
Wo when we talk base fill/ linerate/ fulltime chaff link, we should perhaps be clear about which physical links/routes we are referring to - we must consider the physical links as much as the virtual/ overlay links, in order to properly assess security implications.
In a fill-as-defense model, overlay links dont care about the physical between, only that whatever the two overlay nodes agreed about bandwidth and timing expectations they have for each other is upheld between them. If it isn't, they or their internet path between is under attack either by nature or adversary, the contract A B negotiated between themselves will fault, and they should sleep / drop / renegotiate, before passing data for the overlay again.