Cisco Systems 8600 Series manual Functional Description

Broadband Controller Card (BCC-32, BCC-3, BCC-4)

Functional Description

The BPX switch is a space switch. It employs a crosspoint switch for individual data lines to and from each port. The switching fabric in each BPX switch consists of three elements for the BCC-32, BCC-3 and for the BCC-4 (see Figure 3-2and Figure 3-3):

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Central Arbiter on each BCC.

Crosspoint Switch.

—16 X 16 Crosspoint Switching Matrix on each BCC (12 X 12 used) for BCC-32 and BCC-3.

—16 X 32 Crosspoint Switching Matrix on each BCC (2 X [12 X 12]) used for BCC-4. Serial Interface and LAN Interface Modules on each BCC and on each Function Module.

The arbiter polls each card to see if it has data to transmit. It then configures the crosspoint switching matrix to make the connection between the two cards. Each connection is unidirectional and has a capacity of 800 Mbps (616.7 Mbps for cell traffic plus the frame overhead).

Since there are 16 X 16 (BCC-32 or BCC-3) or 16 X 32 (BCC-4) independent crosspoints and only 15 cards, the switch fabric is non-blocking. However, only one connection at a time is allowed to an individual card. The BPX switch cell switching is not synchronized to any external clocks; it runs at its own rate. No switch fabric clocks are used to derive synchronization nor are these signals synchronized to any external sources.

Each card contains a Switch Interface Module (SIM) which merely provides a standardized interface between the card and the data lines and polling buses. The SIM responds to queries from the BCC indicating whether it has data ready to transmit.

With the BPX switch equipped with two BCCs, the cell switching is completely redundant in that there are always two arbiters, two crosspoint switches, two completely independent data buses, and two independent polling buses.

The BCC incorporates non-volatile flash EEPROM which permits new software releases to be downloaded over the network and battery-backup RAM (BRAM) for storing user system configuration data. These memory features maintain system software and configuration data even during power failures, eliminating the need to download software or reconfigure after the power returns.

Node clocking is generated by the BCC. Since the BPX switch resides as an element in a telecommunications network, it is capable of synchronizing to higher-stratum clocking devices in the network and providing synchronization to lower stratum devices. The BCC can be synchronized to any one of three different sources under software control:

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An internal, high-stability oscillator

Derived clock from a BNI module (no IPX clock sources allowed)

An external clock source connected directly to the BPX

The BCC clock circuits provide clocking signals to every other card slot. If a function card needs to synchronize its physical interface to the BPX switch clock, it can use this timing signal to derive the proper reference frequency. These reference frequencies include DS1, E1, DS3, and E3.

3-4Cisco BPX 8600 Series Reference