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ATM Network Configuration Layer

This section describes virtual circuit setup by the network configuration system. There are two approaches at this level, depending on whether switched virtual circuits (SVCs) or Permanent Virtual Circuits (PVCs) are available. RFC1577 [6] is followed on both the fixed and wireless networks. A Logical IP Subnet (LIS) can be comprised of fixed and wireless portions of the network.

As a requirement for RFC1577 the underlying virtual fiber connections must be fully meshed. If switched virtual circuits are not available, the network configuration program, of which the orderwire is a part, will immediately establish a fully meshed VC configuration. In order to establish this fully meshed network, the network configuration system must have knowledge of all nodes to be connected. All wireless nodes are clearly available from the physical setup layer, however, the nodes which reside on the fixed network are not known. Information about which nodes reside on the fixed network can come from the ATMARP server.

The network configuration system establishes the fully meshed VC connections as follows. The EN on receipt of a USER_POS packet (Table 6) from a new physically connected RN sends pairs of VC_SETUP packets (Table 8) to the new RN and each one of the existing RNs. Each VC_SETUP packet contains a designated IP address of the new RN and a VCI number identifying the VC to be setup. The RN on receipt of each pair of VC_SETUP packets, extracts the IP address and VCI number from each VC_SETUP packet and uses it to setup the VC. Since the VC_SETUP packets are sent in pairs to the new RN and to each of the existing RNs for each RN in the network, VCs will be setup between the new RN and each of the existing RNs resulting in a fully meshed VC configuration as desired.

If switched virtual circuits are used, only the signaling VCs as specified in the standards will be established in a manner similar to that described above.

In the prototype system, remote nodes tear down their VCs and re-establish connections when handing off from one switch to another. The time to establish a PVC from the network configuration system has been measured to be on the order of 300 milliseconds. This includes the time to send a PVC setup message to the switch from the network configuration processor, until an acknowledgement is received at the network configuration processor.


next up previous
Next: ARP Network Configuration Layer Up: Establishing an End-to-End Connection Previous: Establishing an End-to-End Connection

Steve Bush
Sun Aug 25 17:29:09 CDT 1996