Spirent SmartBits System, Reference Manual

Page: 81 / 278

Chapter 7: Sample Test Topologies
Sample Devices and Networks to Test
SmartBits System Reference 73
Testing ATM
Asynchronous Transfer Mode (ATM) is a connection-based technology. It requires that a
specific path be established between two endpoints before data can be transferred between
them.
The ATM series of SmartBits
™
compatible cards can be used to generate and monitor
ATM network traffic. Applications include testing:
•
ATM-to-LAN internet working devices.
•
Very high-performance ATM backbones.
•
LAN-to-ATM edge devices.
Among the significant capabilities of these low cost/high performance ATM cards are:
•
Frame-level testing at full-duplex, full-wire rate on edge devices and switches.
•
Switch testing at full-cell rate.
•
High-rate signaling testing for edge devices.
SmartWindow uses the concept of streams as a transmission engine. When you create a
stream, you define what to transmit, how and where to transmit it, and how fast to transmit it.
The what to transmit is the frame that a stream will use. Each time you create a stream,
you must give the card a data pattern (frame) to transmit for the specified stream. When
you click on the Start button, the stream transmits that data pattern repeatedly in its
assigned turn.
The how and where to transmit depend greatly on stream type and encapsulation. The two
stream types are Permanent Virtual Connections (PVC) and Switched Virtual Connections
(SVC). In ATM, one physical “pipe” is used to transmit and receive all data, but the pipe can
be divided into channels (as in television transmission). When a data cell is transmitted, its
data channel is indicated by two fields in the cell header that is included in each cell. These
are the
Virtual Path Identifier (VPI) and Virtual Channel Identifier (VCI) fields.
The how and where to transmit greatly depends on stream type and encapsulation . There are
two types of streams:
•
Permanent Virtual Connections (PVC).
•
Switched Virtual Connections (SVC).
For ATM, although there is one physical pipe that all data is transmitted and received on, it is
divided into channels much like it is for television. When a data cell is transmitted, the data
channel it belongs to is indicated by the Virtual Path Indicator (VPI) and the Virtual Channel
Indicator (VCI) fields in a Cell Header that accompanies every cell.
Refer to the SmartWindow User Guide located at
http://www.netcomsystems.com/
support/documentation.asp
for detailed information regarding applicable tests and
features.