Agent communication parameters
Parameter | Default value | Description |
|---|---|---|
Port | 1610 | The TCP port number of the parent server on which it communicates with its children. |
Console Port | 1611 | The number of the port that the console uses for communication with the agent. |
Parent Name | The name of the direct parent to which the target device is to be connected. This is either the master or the new device's relay on the next higher level. The name may be entered as the short or long network name, that is, scotty or scotty.enterprise.com or as its IP address in dotted notation, that is, 192.168.1.1 or 2001:db8:85a3::8a2e:370:7334 . You may also select the parent from the list of available devices by clicking the Add Device icon and selecting the desired parent from the list. | |
Parent Port | 1610 | The port number of the direct parent to which the device is connected. |
Overview of agent communication
There are two basic modes of agent communication:
- Static Relay: Clients always use the selected relay and do not attempt communication with another relay. This is typically used for smaller LAN environments that do not use many relays.
- Auto-select Relay: Clients attempt to find a relay by using one or more of the selected methods in the order defined in the following section. If a method cannot find the relay, it returns and the next method in the list is tried.
Configuring Auto-select Relay
Auto-selecting a relay involves the clients attempting to find a relay by using one or more of the selected methods in the following order. If a method cannot find the relay, it returns and the next method in the list is tried.
DHCP method
In this method, the BCM agent sends the DHCPINFORM packet as a request to the DHCP server and retrieves the DHCPACK packet as a response from the DHCP server. It is advised to use the DHCP method first in well-configured DHCP environments, by adding a new extended option that provides the relay information. The detailed steps in the process are described below:
- The BCM agent creates a UDP socket which listens to all the network interfaces at the same time.
- If it fails, the agent retries creating the socket 150 times with a 2 seconds pause between each try. If it still fails, the agent moves to the next mechanism such as relay list or backup relay etc.
- If it succeeds, the agent starts iterating it on all available network interfaces and all IP addresses of the current network interface until it gets a response from the DHCP server.
The agent sends a request (DHCPINFORM) which contains the DHCP Extended Option and a transaction ID to the network. The DHCP Extended Option parameter defines an option to retrieve the BCM relay address and port from the configured DHCP server.
The agent waits for a response from the DHCP server. The timeout value to wait for a response from the DHCP server is configured in the DhcpSelectTimeOut parameter in the mechanism section of the Relay.ini file.
- The DHCP server sends a response (DHCPACK) to the agent which contains the IP address and port (optional) of the BCM Relay and also the transaction ID. The agent verifies the transaction ID to confirm that the response is sent specifically to its request. If the transaction ID is wrong, the agent sends the request again to the same network (maximum 6 retries are allowed).
- Based on the IP address of the BCM relay received in the response, the relay module from the BCM agent establishes a connection with the BCM relay. The first valid response that contains the BCM relay IP address is taken into account. The IP address returned in the response is assigned as a parent.
If there is no response after timeout that means the network has no device with the DHCP server. In this case, the agent retries the same process with another network and so on. If all iterations fail, the agent moves to the next mechanism such as relay list or backup relay etc.
Relay List
Another common primary method is Relay List which is hosted on one or more relay servers. This method enables mapping of IP subnets to relays. The Relay List method can be complemented by Static Relay or Backup Relay as secondary methods (that is, if DHCP and Relay List were not able to find a suitable relay, a list of backup or a static relay is used).
In the Relay List method, you can configure multiple relay servers. Client devices try to connect to a relay server, get the relay list from the server, and use the list to establish connection with a relay server. The relay server order is important because clients connect to the first relay server defined on the list and move sequentially till the end of the list. For more information on relay list, see Managing-relay-lists and Relay-List-Server-parameters.
Relay Balancer
Like the Relay List, the Relay Balancer is hosted on one or more relay servers. This method provides a basic load balancing mechanism to connect agents with their parent. Relay balancers use one or more configurations that include the list of available relays with their associated capacity. The relay balancer tries to distribute the load across all the available relays and guarantee that each requester is always redirected to the same parent. This behavior can be modified using parameters regarding the leases. For more information on relay balancers, see Managing relay balancers and Relay-Balancer-Server-parameters.
Static relay
The static mechanism represents the static mode capabilities offered to the dynamic mode. Having such a mechanism can be helpful, because users may decide to revert back to a static configuration if none of the configured dynamic mechanisms succeed.
Backup Relay
This method is also well suited for agents that connect through the internet and do not have access to DHCP or the master server. In this case, one or more internet facing relays can be added to the backup relays. For more information on backup relay, see Backup-Relay-parameters .
Auto-discovery
By using this method, client agents perform a network scan on either a pre-defined range of IP addresses or a number of neighbors surrounding their IP address. However, this method must be used cautiously as it creates network traffic and requires good configuration so agents efficiently find their relays. For more information on auto-discovery, see Autodiscovery-of-your-network.
Custom Script
Use this method only when none of the built-in methods mentioned above fits the environment and a customized script is available to handle relay discovery. For more information on custom script, see Custom-Script-parameters .