Corda 4, TestNet - Transaction exceeded network's maximum transaction size limit : 4000000 bytes

Question

We are building a POC using Corda and Springboot web server.

Following are the versions of Corda platform, Springboot server, and other essential dependencies used for building the POC-

cordaReleaseGroup=net.corda
cordaVersion=4.0
gradlePluginsVersion=4.0.45
kotlinVersion=1.2.71
junitVersion=4.12
quasarVersion=0.7.10
spring_version = '4.3.11.RELEASE'
spring_boot_version = '2.0.2.RELEASE'
spring_boot_gradle_plugin_version = '2.1.1.RELEASE'
jvmTarget = "1.8"
log4jVersion =2.11.2
platformVersion=4
slf4jVersion=1.7.25
nettyVersion=4.1.22.Final

The CorDapp developed for POC has four nodes -

Notary Node (Validating)
Provider Company Node (Node A)
Consumer Company 1 Node (Node B)
Consumer Company 1 Sub Contact Node (Node C)    

Following are the flows defined in the CorDapp -

Flow 1: "Node A" sends a trade request to "Node B" and "Node C". "Node A" self-signs it and also collect signatures from other nodes. The trade request also contains an attachment.

Flow 2: "Node B" approves the trade request, self-signs it, gets signature from "Node A" and "Node C" and closes the trade.

In the local N/W, these flows work properly.

However, in Corda TestNet N/W, the "Flow 1" fails and throws the following exception -

Transaction exceeded network's maximum transaction size limit : 4000000 bytes.

In the Stack Overflow, we found related issue (see URL: Changing the maxTransactionSize using Corda OS v3.x with network bootstrapper ) which says -

In Corda 4, a mechanism will be introduced to allow the network 
parameters of a bootstrapped network to be modified.

Question: Is it possible to increase the max transaction limit of the network? If yes, please guide to do so.

Answer 1

The Testnet was built for the community to experience the Corda network.

Same as I replied here: Corda, TestNet: Is it allowed to modify the X.500 name of a pre-configured Corda node downloaded from https://testnet.corda.network

Answer 2

The ability to change network parameters depends on the kind of network you are deploying to. At this point most managed networks on Corda have a max_transaction_size which is much higher than 4mb so an increase is recommended.

Bootstrapped Network

Developers have complete control over the network parameters of a network they bootstrap. You can now override the default network parameters during the bootstrap process as described here: https://docs.corda.net/network-bootstrapper.html#modifying-the-network-parameters

A Corda Network

No matter which network you deploy to (eg. Testnet, UAT, the Corda Network [tCN] or a private network) network parameters can only be changed by the network operator. In the case of Testnet, UAT and tCN that network operator is the Corda Network Foundation. The update policy is described here: https://corda.network/participation/networkparamsschedule.html In the case of a private network you would consult with the operator of that network or have this control yourself if you are running the Corda Enterprise Network Manager (CENM).

When network parameters are updated it requires agreement amongst the nodes on the network. The process for updating the parameters and requesting acceptance from nodes is described here: https://docs.corda.r3.com/network-map.html#network-parameters-update-process