ISDN Connection Management
IP Specifics
IP Address Connect
As stated previously, an IP Address Connect connection is an ISDN connection that is established to a specific destination IOLINK router dependent upon the destination IP address contained within IP traffic received from the local LAN.
This means that the IOLINK router continuously monitors IP traffic from the local LAN, as all IP routers do, and makes ISDN connections to partner IOLINK routers when IP traffic needs to be sent to remote LANs. Once the IP traffic is passed to the remote LAN and all sessions are closed, the local IOLINK router will then disconnect the ISDN call and continue to monitor the local LAN for IP traffic.
The IP Address Connect table consists of IP addresses and associated ISDN numbers of remote partner IOLINK IP Routers. Either one or both of the ISDN calls may be used for IP Address Connect use. When one of the ISDN calls is defined for
The combination of
Suspension of TCP/IP Sessions
When Connection Management is enabled, TCP sessions that are established across the ISDN calls are monitored and maintained in a table. The TCP session table may contain up to 256 entries. The IOLINK will filter all traffic for any TCP/IP session over the 256 limit of the table preventing any new TCP sessions from being established.
While an ISDN call is suspended, if the IOLINK router observes that one of the devices in the session stops sending keepalive packets, the IOLINK router will begin to generate keepalive packets and send them to the device in order to determine the status of the device. The length of time the IOLINK router waits before beginning to generate keepalive packets is definable by the operator.
If the device does not respond to five consecutive keepalive packets sent from the IOLINK router, the IOLINK router will determine that the device has gone away and the IOLINK router will send a packet to each end of the TCP session to shut down the session. When the shut down packet is generated for the remote device, the IOLINK router will
RIP—Routing Information Protocol
IOLINK ISDN routers incorporate a 3 second settling time for IP RIP updates. This means that an IOLINK will wait for three seconds after an initial change in the network is reported before transmitting that change on to the remaining IOLINK routers connected on the Wide Area Network.
