> For the complete documentation index, see [llms.txt](https://archive-docs.klaytn.foundation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://archive-docs.klaytn.foundation/content/installation-guide/deployment/service-chain/getting-started/nested-sc.md). # Nested ServiceChain This chapter explains how to build ServiceChain networks in a hierarchical structure by adding a new ServiceChain network to the ServiceChain network built in the previous chapter. The ServiceChain network to be added also consists of 4 SCNs in this example. The ServiceChain network constructed in the previous chapter is defined as L2, and the ServiceChain network to be newly constructed is defined as L3. We are going to connect a bridge between L2 and L3 to create a hierarchical structure. The overall structure of the ServiceChain network to be constructed in this chapter is shown in the figure below. ![](/files/EnhA3z7J0hrn5a4jvfEu) ### Prerequisites * Assume that you have progressed to the ServiceChain configuration and Baobab EN described in [Nested ServiceChain](/content/installation-guide/deployment/service-chain/getting-started/nested-sc.md). So we will briefly explain what was explained in the previous section. * Assumptions and Limitations * One EN can bridge one-to-one to one of the SCNs of the ServiceChain L2. Similarly, one SCN in L2 of the ServiceChain can bridge one-to-one to one of the SCNs in L3. * An SCN node can have a main bridge and a sub bridge at the same time. However, the port numbers of the main bridge and the sub bridge must be set differently. (eg main-bridge: 50505, sub-bridge:50506) * Not all SCNs in L2 need to be bridged to EN, and likewise SCNs in L3 need not all be bridged to L2. However, for high availability, it is recommended that there are two or more main-bridge and sub-bridge pairs between chains. In this chapter, only one pair will be connected between L2 and L3, and the high availability between L2 and L3 is same to the HA between Baobab and L2. ### Step 1: Create and update Homi data for L3 As when configuring ServiceChain L2, execute the `homi` command to create scripts and configuration files for building L3. You can run `homi` on any Linux/Mac PC. Baobab's `chainID` is `1001`, and L2's `chainID` was set to `1002` in the previous example, so for convenience, L3's `chainID` is set to `1003`. When operating a blockchain for an actual service, you must register a new `chainID` value at to avoid the `chainID` conflict with other ServiceChains and EVM chains. ```console $ ./homi setup --gen-type local --cn-num 4 --test-num 1 --servicechain --chainID 1003 --p2p-port 22323 -o homi-output Created : homi-output/keys/passwd1 Created : homi-output/keys/passwd2 Created : homi-output/keys/passwd3 Created : homi-output/keys/passwd4 Created : homi-output/scripts/genesis.json Created : homi-output/keys/nodekey1 Created : homi-output/keys/validator1 Created : homi-output/keys/nodekey2 Created : homi-output/keys/validator2 Created : homi-output/keys/nodekey3 Created : homi-output/keys/validator3 Created : homi-output/keys/nodekey4 Created : homi-output/keys/validator4 Created : homi-output/scripts/static-nodes.json Created : homi-output/keys_test/testkey1 Created : homi-output/keys_test/keystore1/0xdC7218621513f71d609653d22C39d79d558d9CDC Created : homi-output/Klaytn.json Created : homi-output/Klaytn_txpool.json ``` ![](/files/Nsg4yKUwGBTautju1TnT) Update `IP address` and `port` information of ServiceChain L3 nodes in `homi-output/scripts/static-nodes.json`. ```json [ "kni://358235ccbf97a1f...787f7@192.168.0.21:22323?discport=0&type=cn", "kni://14ac4e3d53de5c7...6c91d@192.168.0.22:22323?discport=0&type=cn", "kni://5f36a456d93da09...8e216@192.168.0.23:22323?discport=0&type=cn", "kni://d62fd0928b9b6e5...6badf@192.168.0.24:22323?discport=0&type=cn" ] ``` Copy `homi-output` to all SCN nodes (SCN-L3-01, SCN-L3-02, SCN-L3-03, SCN-L3-04) of ServiceChain L3. ```console $ scp -r path/to/homi-output user@192.168.0.21:~/ $ scp -r path/to/homi-output user@192.168.0.22:~/ $ scp -r path/to/homi-output user@192.168.0.23:~/ $ scp -r path/to/homi-output user@192.168.0.24:~/ ``` Initialize all nodes. ```console $ kscn --datadir ~/data init ~/homi-output/scripts/genesis.json $ ls ~/data keystore klay kscn ``` Connect to all SCNs (SCN-L3-01, SCN-L3-02, SCN-L3-03, and SCN-L3-04), copy `static-nodes.json` to the data folder `~/data`, and copy `nodekeys` one by one. ```console $ cp ~/homi-output/scripts/static-nodes.json ~/data/ $ cp ~/homi-output/keys/nodekey{1..4} ~/data/klay/nodekey ``` ### Step 2: SCN configuration in L3 Edit `conf/kscnd.conf` on all SCNs in ServiceChain L3 as follows: The `PORT` uses 22323, the default port of the ServiceChain. `DATA_DIR` is `~/data`. ``` ... PORT=22323 ... DATA_DIR=~/data ... ``` Run the ServiceChain on all SCN nodes in L3 and check if it works properly. ```console $ kscnd start Starting kscnd: OK $ kscn attach --datadir ~/data > klay.blockNumber 10 ``` ### Step 3: Restart after setting L2 main bridge Connect to the console of SCN-L2-03 node, (Note: this is not in L3 but in L2) that will act as the main bridge in the ServiceChain L2. ![](/files/ImdOTDnQi6yyhxT0Jwns) Edit the kscn configuration file `conf/kscnd.conf` of SCN-L2-03 as follows. ```console SC_MAIN_BRIDGE=1 ``` Restart kscnd on SCN-L2-03. ```console SCN-L2-03$ kscnd stop SCN-L2-03$ kscnd start ``` ### Step 4: Check KNI of Main Bridge Node Check the KNI information of SCN-L2-03 node. This value will be used to create the `main-bridges.json` file of SCN-L2-03 node, which will be set up the subbridge in the ServiceChain L3. ![](/files/up1OXF7rRAEtlVAJ0Emc) ```console SCN-L2-03$ kscn attach --datadir ~/data > mainbridge.nodeInfo.kni "kni://87989a5a5dcc165...85b16b@[::]:50505?discport=0" ``` ### Step 5: Configure L3 sub-bridge Connect to SCN-L3-01 node that will have a subbridge of the ServiceChain L3 (Note: this is not L2). Create `main-bridges.json` under `~/data` folder. Replace \[::] after @ with the IP address of the node you checked in step 4. ```console SCN-L3-01$ echo '["kni://87989a5a5dcc165...85b16b@192.168.0.13:50505?discport=0"]' > ~/data/main-bridges.json ``` Edit the configuration file `conf/kscnd.conf` of the SCN-L3-01 node with subbridge as follows. set `SC_SUB_BRIDGE`to 1 for activating the bridge connection, and `SC_PARENT_CHAIN_ID` is `1002`, `chainID` of L2, Set `SC_ANCHORING` to 1 to automatically anchor data upon restart. You can also access the SCN-L3-01 shell and turn on data anchoring with the `subbridge.anchoring(true)` command or turn it off with the `subbridge.anchoring(false)` command. `SC_ANCHORING_PERIOD` is a parameter that determines how often anchoring transactions are sent to the parent chain. Set the node to anchor every 10 blocks by specifying a value of 10. Default is 1. ```console SC_SUB_BRIDGE=1 … SC_PARENT_CHAIN_ID=1002 … SC_ANCHORING=1 SC_ANCHORING_PERIOD=10 ``` Restart kscnd on SCN-L3-01 after completing the setup. ```console SCN-L3-01$ kscnd stop Shutting down kscnd: Killed SCN-L3-01$ kscnd start Starting kscnd: OK ``` Check `subbridge.peers.length` to see if SCN-L3-01 is connected to SCN-L2-03, check `subbridge.latestAnchoredBlockNumber` to check the latest anchored block number to see if anchoring is in progress. ```console SCN-L3-01$ kscn attach --datadir ~/data > subbridge.peers.length 1 > subbridge.latestAnchoredBlockNumber 5010 ``` --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. 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