In order for parachain to communicate with each other, they need to have a HRMP channel opened first.
Currently the maximum number of HRMP channel allowed on Kusama 10.

We have 27 parachains at moment and Karura is already have 6 channels and working with many more parachains on opening more channels. 10 channels is simply not enough.

There are overheads on relaychain per each established HRMP channels and therefore we needs an upper limit. However similar to number of parachains, we do not know the upper limit value and will want to gradually increase the limit and observe the performance of Kusama. This also helps to configure a safe limit for Polkadot.

This proposal aims to increase the maximum number of HRMP channels from 10 to 30. Note that number of inbound and outbound channels are separate configuration and therefore this is a batch call to update both values.

30 channels should be enough for at least next few months. We have another proposal to increase further if any parachains are approaching this limit and Kusama is still operating fine.

Schedule a majority-carries referendum to be tabled next once it is legal to schedule
an external referendum.

The dispatch of this call must be `ExternalMajorityOrigin`.

- `proposal_hash`: The preimage hash of the proposal.

Unlike `external_propose`, blacklisting has no effect on this and it may replace a
pre-scheduled `external_propose` call.

Weight: `O(1)`

Send a batch of dispatch calls.

May be called from any origin.

- `calls`: The calls to be dispatched from the same origin. The number of call must not
  exceed the constant: `batched_calls_limit` (available in constant metadata).

If origin is root then call are dispatch without checking origin filter. (This includes
bypassing `frame_system::Config::BaseCallFilter`).

# <weight>
- Complexity: O(C) where C is the number of calls to be batched.
# </weight>

This will return `Ok` in all circumstances. To determine the success of the batch, an
event is deposited. If a call failed and the batch was interrupted, then the
`BatchInterrupted` event is deposited, along with the number of successful calls made
and the error of the failed call. If all were successful, then the `BatchCompleted`
event is deposited.

- Parachains need to open HRMP channels to communicate with each other.
- Currently, Kusama allows a maximum of 10 HRMP channels.
- There are 27 parachains at the moment, and Karura already has 6 channels.
- This proposal aims to increase the maximum number of HRMP channels from 10 to 30.
- If needed, there may be another proposal to increase the limit further in the future.

#442 Increase maximum number of HRMP channels from 10 to 30