Specifications

ATM/ForeRunner Overview
Introduction ForeRunner ATM Switch Modules
1-2 Management Module Guide
The 9A000 is a dual-slot MMAC-Plus module that provides an aggregate 2.5
Gbps of ATM switching capacity for up to 24 workstations or ATM devices. Its
four network module slots can provide a range of LAN and WAN interfaces
from 1.5 to 622 Mbps to accommodate ATM.
The SFCS-200BX and SFCS-1000 meet the needs of LAN backbone networks
and offer a variety of connectivity options including LAN to ATM access,
interswitch links, and WAN access. The SFCS-200BX is a 2.5 Gbps modular
ATM switch for the wiring closet with four network module slots. The
SFCS-1000 is a modular, 10 Gbps backbone ATM switch that includes two 2.5
Gbps switch modules, each containing four network module slots. It provides
connectivity for up to 96 ATM servers or LAN access devices.
The ASX100, ASX200 series, and ASX1000 are stand-alone switches that
provide workgroup, LAN, LAN backbone, and WAN access support. They are
configurable from 2 to 96 ports, offer a switching capacity ranging from 2.5 to
10 Gbps, and support LAN and WAN interface speeds of 34 to 155 Mbps.
ATM/ForeRunner Overview
Asynchronous Transfer Mode (ATM) is based on the transmission of
fixed-length (53-byte) cells of data. Contrast this with an Ethernet LAN,
which transmits variable-length packets ranging in size from 64 to over 1500
bytes of data. ATM’s use of small, fixed-length data cells allows for improved
traffic management and traffic shaping.
ATM is a connection-oriented network communication architecture, which
generally means that it transmits data through pre-established virtual
channels (circuits), similar to telephone calls. Virtual channels may be
established automatically by Switched Virtual Circuit (SVC) signaling or they
may be set up manually by the network administrator to form Permanent
Virtual Circuits (PVCs).
Each ATM cell contains a five-byte header and 48 bytes of payload. The header
includes a Virtual Path Identifier (VPI) and a Virtual Channel Identifier
(VCI). These identifiers are used by ATM switches to determine the correct
channels to transmit particular cells. Transmission is controlled by statistical
multiplexing, which awards bandwidth (channels) to devices ready to send
data on a first come, first served basis. (For more information on virtual paths
and virtual channels, see Appendix A, Overview of Signaling Concepts.)
The combination of small, fixed-length data cells and the efficient use of
bandwidth (among other things) allow ATM switches to communicate
time-critical video and audio data along with other computer data across the
ATM network. In an end-to-end transmission across a mixed LAN/ATM/LAN
network, packets transmitted by a LAN workstation to an ATM switch are
segmented into cells for high speed transmission through ATM channels. At
the receiving end, cells are reassembled into packets for use by another LAN
workstation.