BPX, IGX, and IPX Architecture

The BPX provides the following features:

• Increased node switching capacity to facilitate the deployment of larger, higher-capacity networks.

• A platform for providing multiple services such as frame relay, ATM, SMDS, CES.

• Increased network capacity by using T3, E3, or OC3/STM-1 trunks to facilitate statistical bandwidth aggregation as frame relay Committed Information Rates increase.

• A clear migration path to networks utilizing the 53-byte cell relay network protocols defined by ATM standards.

• Ability to support higher-speed network access interfaces such as SONET, and SDH to access rates up to 622 Mbps.

• Advanced congestion management and routing features such as FairShare, ForeSight, AutoRoute, and Opticlass.

• Higher-speed network management interfaces and access for real-time, per-connection statistics collection.

The BPX employs a redundant 9.6 Gbps non-blocking crosspoint switch matrix for cell switching. The switch matrix can establish up to 20 million point-to-point connections per second between ports. A single BPX provides twelve high-speed switch ports, each of which is capable of operating at 800 Mbps. Access to and from the crosspoint switch is through multi-port network and user access cards.

An arbiter is utilized to set up and release each cell path based on those ports with traffic data to switch. The arbiter can set up 20 million point-to-point connections per second between the BPX switch ports. For maximum reliability, the switch matrix, data paths, and all control and arbiter functions are provisioned in a fail-safe 1:1 redundant configuration.

Each BPX node is configured with twelve slots (switch ports) for network or user interfaces and three slots for common equipment cards. Each Broadband Network Interface (BNI) card provides high-speed network interfaces for trunking to other BPX nodes, to IPX nodes equipped with an ATM trunking card, or to other networks. Each of the BPX's high-speed trunk cards can be configured for 1:1 redundancy. An ATM Service Interface (ASI) card provides two DS3, E3, or OC3/STM-1 ATM ports for connection to ATM customer premise equipment.

The BPX is a virtual circuit switch. It can switch on VCI and/or VPI fields in the ATM cell header. Individual connections, as well as groups of connections within a path, may be switched. This greatly enhances the versatility of the BPX as a network switch.

Frame Relay to ATM Interworking enables frame relay traffic to be connected across high-speed ATM trunks. Interworking allows users to retain their existing Frame Relay services, and as their needs expand, migrate to the higher bandwidth capabilities provided by BPX ATM networks. Two types of interworking are supported, network interworking and service interworking. The network interworking function is performed by the AIT card on the IPX and by the BTM card on the IGX. The FRSM card on the AXIS supports both Network Interworking and Service Interworking. On the AXIS, IPX, or IGX, Frame Relay data is received directly from the user equipment, converted from the Frame Relay protocol to the ATM protocol, and the data streamed into the ATM cell's 48-byte payload, sending ATM cell after cell, until the end of a frame is reached. This is repeated for each frame received from the user until the last frame is transmitted.

If the traffic is voice or constant bit rate, low-speed data, which will terminate on an IPX or IGX, the 24-byte FastPackets are combined within the 48-byte ATM payload, normally two FastPackets to a cell. If the connection carries data or voice that is very delay sensitive, the StrataCom switch may, as an option, occasionally pack only one FastPacket into a cell payload to reduce delay to a minimum. Once data is segmented into cells, the cells can easily be converted from one size to another without requiring additional adaptation simply by changing the cell size and streaming the data into a different capacity payload.

The BPX may also be used to provide a smooth migration path for network operators currently using IPX and IGX nodes in their networks who need additional capacity and would like to build on their existing equipment. Since the BPX can be integrated into an existing IPX/IGX network by adding only a single card to each of the IPX or IGX nodes that need to connect to the BPX, the hardware costs are kept to a minimum.

The ATM cell payload is ideally suited to transporting IPX FastPackets since both are fixed length and the size of the ATM cell is larger than the FastPacket cell length (no segmentation of the cell is necessarily required). Packets of data that are created by IPX and IGX nodes in a mixed environment are encapsulated in the ATM cells for transmission throughout the network.

For more details on the BPX hardware, refer to the BPX Reference. For information on the BPX commands, refer to the Command Reference.

Each BPX switch port has a capacity of operating at 800 Mbps and is capable of supporting OC-12 data rates in each of the twelve switch ports on the BPX when this interface becomes available.

All data flow through the switch is monitored at every process to detect any corruption of the data or addressing. Flow-through parity recomputation and checking is performed within the individual cards and data paths on the backplane to detect data path and memory faults that would otherwise be difficult to detect with periodic checks.

The controller, switch matrix, backplane data paths, and all control and timing signals are redundant throughout the BPX switch to provide maximum reliability. Both Broadband Controller Cards (BCCs) are synchronized to each other and data paths are buffered so any switchover will be transparent.

• Adapts customer frame relay, voice/FAX, synchronous and asynchronous data, and digital video into high-speed, fixed length cells (either ATM cells or FastPackets).

• Transmits data utilizing high-speed digital transmission facilities and simple transmission protocol resulting in very low end-to-end delays.

• Maximizes network bandwidth utilization by compressing voice data, eliminating silent periods, eliminating repetitive patterns and idle codes in data streams, and transmitting packets only when there is actual circuit data to be sent.

• Connections are easily established and automatically routed.

• Users can assign a hierarchy of class of service and priorities for various types of traffic.

• Monitors all trunk activity, detects trunk failures, and automatically reroutes around failed trunks without loss of service (as long as sufficient spare bandwidth is available).

• Provides tools for detecting and dynamically avoiding and/or managing network congestion.

• Collects status and traffic statistics on all trunks, circuits, connections, frame relay ports.

• Display of network configuration and status from any node.

The IPX family consists of different configurations designed to meet the needs of small, medium, and large sites. There are three basic IPX packaging options: the IPX 8, IPX 16, and IPX 32. All three systems use virtually identical hardware and software; they differ only in the number of card slots provided. The IPX 8 extends the benefits of FastPacket technology to the edge of networks without losing bandwidth efficiency.

Non-disruptive diagnostics continuously monitor the performance of each component in the node. In the event of a failure, a backup component is automatically switched into service with no effect on the user. All cards and power supplies are hot-replaceable; they can be added or replaced on-line with no interruption in service.

IPX systems can be configured to operate in network applications at any world-wide network location. Options include interfaces to both North American and International standard trunks and ports. Power supply options include 208 VAC, 240 VAC, and 48 VDC modules. All cards are programmable, with downloadable firmware, to operate with various network parameters and are easily upgraded to take advantage of new features as they are developed.