I didn't find info about my situation in google so I need to ask here.

MK: 1.12.2
AE2: rv-5stable-11
Forge: 14.23.4.2760
Setup without channels:

networkfeatures {
    B:Channels=false
    B:PowerGen=true
    B:QuantumNetworkBridge=true
    B:Security=false
    B:SpatialIO=true
}

As I always play without channels I can remember that using simple ME cables leads to very simple and efficient network. Everything "just works".
But in this game I can see that network is dramatically slows down due to cable length or import/export buses count - I'm not sure what is affecting most.

Is this a bug or a new default behavior? If this is intended - how can I split network without controllers (they are autodisabled when channels is off) or increase network speed?
My last game with networks was MK 1.10 so I'm not sure about 1.12 changes.

There are so small information on addon's rules and best practices even on addon's wiki.

How have you determined that it is cable length that is affecting performance, and not a third factor?

Thinking about it, channels ore not, the count of the number of tiles is going to be the same either way. You can certainly look for ways to build sections into sub-networks (ore processing, for example, could be its own smaller network, that delivers the final ingot to the 'main' network, thus shrinking the size of the master network), but I'm not wholly convinced there isn't something else at play here.

There is a lack of details to help. Like pictures of the setup, are there any network bridges, what mods are installed and so on.

Make sure everything is chunkloaded especially with bridges and large area networks. Make sure to have enough energy cells, because input is limited by me power capacity.

That was just a "proof of concept" setup of my own modpack: a first try of AE2 for MK1.12.2 and testing of stability of power generation setup.

Everything was fully chunkloaded via ChickenChunks chunkloader on the top of the base and radius set to cover about 6*6 chunks with actual base sitting in nearest chunks.

First part of the base was a setup of 20 garden cloche from Immersive Engineering filled with different seeds from Mystical Agriculture.
All cloches was watered by fluiducts from Thermal Dynamics with water generated bu Aqueous Accumulator from Thermal Expansion.
ME system was set to take products by Import buses and feed with fertilizer via Export buses. There no speed cards were used here.
5 blocks higher on a second floor there was a 4 ME drives filled with 16K cards + 2 ME terminals (standard and crafting).

Second part was a power generation room 20 block away. Very standard setup of Syngas Producer + Gas Turbine Generator from Advanced Generators by BDew. I'm completely sure there no problems here.
ME system pulls coal essence to autocrafting table (can't remember addon) that creates coal wich is flows to Syngas producer via short (4 blocks) Itemduct. Also Syngas Produces was feed with water from near placed Aqueous Accumulator via Fluiduct.
Produced syngas feeded to Gas Turbine Generator and power generated distributed over all the base via fluxducts.
I'm completely sure that this part of base is a no problem.

Third part of base was a processing plant 15 blocks away with 3 machines from Thermal Expansion: Pulverizer, Redstone Furnace, Induction Smelter. Machines was manually feeded and only output was collected via Import buses on each machine with 4 speed card inserted.

ME cable was a staight line from ME Disk Drive on first part of the base thru second part (exporting coal essence via one Export bus) to third part connecting to machines and two additional ME Terminals.

The problem is ME Network dramatic slowdown.
I have a full bag of something. For example cobblestone. Open ME Terminal and doubleclick on items.
In 1.7.10 this was lead to instamove of all items to ME Network. In 1.10.2 everything was moved to ME Network by full stacks. In 1.12.2 I can see clear dependancy on something - network length or network elements count. With full network as I described I can move items only by 8 elements. If I cut off third part of base by removing one block of ME cable I can move elements to Network by 16 elements (not completely remember). If I cut off third and second parts of base I can move elements by about 32 elements.

Looks like ME logic of channels still works even after channels is disabled. As I said in my very first post I'm not sure is it error or planned behavior as I can't find any info in Wiki or Google. I remember very-very big ME Networks in 1.7.10 that was work perfect. Also I can't remember any countable problems in 1.10.2 setup. So I was really frustrated when I see this =)

ModPack list:

ActuallyAdditions-1.12.2-r140.jar
ae2stuff-0.7.0.4-mc1.12.2.jar
appliedenergistics2-rv5-stable-11.jar
Aroma1997Core-1.12.2-2.0.0.0.b156.jar
Aroma1997s-Dimensional-World-1.12.2-2.0.0.2.b81.jar
bdlib-1.14.3.12-mc1.12.2.jar
BetterFps-1.4.8.jar
binnie-mods-1.12.2-2.5.0.168.jar
BiomesOPlenty-1.12.2-7.0.1.2399-universal.jar
Bookshelf-1.12.2-2.3.559.jar
buildcraft-7.99.18.jar
buildcraft-compat-7.99.15.jar
Chameleon-1.12-4.1.3.jar
ChestTransporter-1.12.2-2.8.8.jar
ChickenChunks-1.12.2-2.4.1.73-universal.jar
Chisel-MC1.12.2-0.2.1.34.jar
ClientTweaks_1.12.2-3.1.9.jar
CodeChickenLib-1.12.2-3.2.2.353-universal.jar
CoFHCore-1.12.2-4.5.3.20-universal.jar
CoFHWorld-1.12.2-1.2.0.5-universal.jar
CompactSolars-1.12.2-5.0.17.340-universal.jar
CraftingTweaks_1.12.2-8.1.9.jar
CraftTweaker2-1.12-4.1.9.jar
CTM-MC1.12.2-0.3.2.18.jar
Cucumber-1.12.2-1.1.1.jar
diethopper-1.1.jar
EnderCore-1.12.2-0.5.39.jar
EnderIO-1.12.2-5.0.33.jar
EnderStorage-1.12.2-2.4.5.135-universal.jar
energyconverters_1.12.1-1.0.1.2.jar
environmentalcreepers-1.12.2-1.4.0.jar
environmentaltech-1.12.2-2.0.15.1.jar
ExtraCells-1.12.2-2.5.13a60.jar
extrautils2-1.12-1.9.3.jar
FastLeafDecay-v14.jar
foamfix-0.10.1-1.12.2.jar
forestry_1.12.2-5.8.1.341.jar
Forgelin-1.7.4.jar
ForgeMultipart-1.12.2-2.5.0.71-universal.jar
FTBLib-5.3.0.53.jar
FTBUtilities-5.3.0.51.jar
gendustry-1.6.5.8-mc1.12.2.jar
generators-0.9.20.12-mc1.12.2.jar
GraveStone-1.12.2-Graves-1.0.18.jar
HammerCore-1.12.2-2.0.2.3.jar
hopperducts-mc1.12-1.5.jar
iChunUtil-1.12.2-7.1.4.jar
ikwid-1.0.2.jar
ImmersiveEngineering-0.12-85.jar
immersivetech-1.12-1.3.10.jar
industrialcraft-2-2.8.99-ex112.jar
industrialforegoing-1.12.2-1.11.2-212.jar
InventoryTweaks-1.64-dev.jar
ironchest-1.12.2-7.0.46.831.jar
jeibees-0.9.0.5-mc1.12.2.jar
jeiintegration_1.12.2-1.5.1.36.jar
jei_1.12.2-4.12.0.216.jar
journeymap-1.12.2-5.6.0b2.jar
justenoughbuttons-1.12.2-1.2.2-5.jar
LLOverlayReloaded-1.1.6-mc1.12.2.jar
Login_Shield-1.12.2-3-g7c6e7ac.jar
MagicBees-1.12.2-3.1.10.jar
malisisblocks-1.12.2-6.1.0.jar
malisiscore-1.12.2-6.4.0.jar
malisisdoors-1.12.2-7.3.0.jar
Mantle-1.12-1.3.2.24.jar
mcjtylib-1.12-3.0.5.jar
Mekanism-1.12.2-9.4.13.349.jar
MekanismGenerators-1.12.2-9.4.13.349.jar
MekanismTools-1.12.2-9.4.13.349.jar
modtweaker-4.0.14.jar
MrTJPCore-1.12.2-2.1.3.35-universal.jar
MTLib-3.0.5.jar
natura-1.12.2-4.3.2.62.jar
NetherPortalFix_1.12.1-5.3.17.jar
NoMobSpawningOnTrees-1.2.2-mc1.12.2.jar
NotEnoughIDs-1.5.4.2.jar
NotEnoughItems-1.12.2-2.4.1.239-universal.jar
OpenBlocks-1.12.2-1.7.6.jar
OpenModsLib-1.12.2-0.11.5.jar
Pam's+HarvestCraft+1.12.2z.jar
plustic-6.5.2.0.jar
PortalGun-1.12.2-7.0.2.jar
pressure-1.3.1.9-mc1.12.2.jar
ProjectE-1.12-PE1.3.1B.jar
ProjectRed-1.12.2-4.9.1.92-Base.jar
ProjectRed-1.12.2-4.9.1.92-lighting.jar
rangedpumps-0.5.jar
reauth-3.6.0.jar
RedstoneArsenal-1.12.2-2.5.1.13-universal.jar
RedstoneFlux-1.12-2.0.2.3-universal.jar
rftools-1.12-7.56.jar
rftoolsctrl-1.12-1.9.1.jar
rftoolsdim-1.12-5.61.jar
SimplyJetpacks2-1.12.2-2.2.7.45.jar
SolarFluxReborn_1.12.2-4.12r.jar
SoulShards-TOW-1.12-2.7.6-56.jar
subcommonlib-sublib-1.12.2-1.2.0.4.jar
TConstruct-1.12.2-2.10.1.87.jar
telepads-1.12.2-1.1.0.6.jar
Tesla-1.12.2-1.0.63.jar
tesla-core-lib-1.12.2-1.0.15.jar
thebomplugin-1.12-0.2.3.jar
theoneprobe-1.12-1.4.24.jar
ThermalCultivation-1.12.2-0.3.0.7-universal.jar
ThermalDynamics-1.12.2-2.5.1.14-universal.jar
ThermalExpansion-1.12.2-5.5.0.29-universal.jar
ThermalFoundation-1.12.2-2.5.0.19-universal.jar
TinkersComplement-1.12.2-0.2.3b.jar
tinker_io-1.12.2-release 2.6.1.jar
topaddons-1.12.2-1.9.0.jar
valkyrielib-1.12.2-2.0.15.1.jar
WR-CBE-1.12.2-2.3.1.30-universal.jar
XRay-58.modded-for-1.12.2.jar

Second part was a power generation room 20 block away. Very standard setup of Syngas Producer + Gas Turbine Generator from Advanced Generators by BDew. I'm completely sure there no problems here.

The problem is ME Network dramatic slowdown.
I have a full bag of something. For example cobblestone. Open ME Terminal and doubleclick on items.
In 1.7.10 this was lead to instamove of all items to ME Network. In 1.10.2 everything was moved to ME Network by full stacks. In 1.12.2 I can see clear dependancy on something - network length or network elements count. With full network as I described I can move items only by 8 elements. If I cut off third part of base by removing one block of ME cable I can move elements to Network by 16 elements (not completely remember). If I cut off third and second parts of base I can move elements by about 32 elements.

well you just literally explained why i was asking if you have eneergy cells installed :D

you don't and that is why you can only insert a small portion ... your system has so few internal capacity that it runs out of power and reboots on a permanent base (but you yet can't clearly see it besides side effects)

@yueh hope you get your power down before reboot feature done soon :P

just insert a few dense energy cells and you will see your problems vanish

you have to understand that when you have only (let's take random numbers)
10k energy capacity and your system basically requires already 9k/tick and THEN you increase load by moving items, you exceed the 10k in just one single tick and there is no way to draw anymore power in this single tick, so the system reboots and you have only insertted a few items

i will close this for now, if the issue persists, just speak up and the issue qwill be reopened :)

PS: the items being moved one by one instead of a whole stack IS required in 1.12 .. i can't tell the exact reason but it has been explained somewhere XD